Lung Endothelial Transcytosis

Size: px
Start display at page:

Download "Lung Endothelial Transcytosis"

Transcription

1 Lung Endothelial Joshua H. Jones 1 and Richard D. Minshall *1,2 ABSTRACT of macromolecules through lung endothelial cells is the primary route of transport from the vascular compartment into the interstitial space. Endothelial transcytosis is mostly a caveolae-dependent process that combines receptor-mediated endocytosis, vesicle trafficking via actin-cytoskeletal remodeling, and SNARE protein directed vesicle fusion and exocytosis. Herein, we review the current literature on caveolae-mediated endocytosis, the role of actin cytoskeleton in caveolae stabilization at the plasma membrane, actin remodeling during vesicle trafficking, and exocytosis of caveolar vesicles. Next, we provide a concise summary of experimental methods employed to assess transcytosis. Finally, we review evidence that transcytosis contributes to the pathogenesis of acute lung injury American hysiological Society. Compr hysiol 10: , Didactic Synopsis Major teaching points Endothelial transcytosis is an energy-dependent process in which macromolecules in the blood are internalized via vesicles, trafficked across the cell, and ultimately released into the subendothelial space. Caveolae are 40 to 80 nm omega-shaped vesicles that act as transcytotic carriers for macromolecular cargo. Cargo receptors that localize to caveolae enable specific uptake into endothelial cells. Receptor-mediated endocytosis entails ligand-receptor interactions that result in Src activation, caveolin-1 phosphorylation, caveolar vesicle swelling, and ultimately vesicle release from the plasma membrane. Caveolae directly associate with the cellular cytoskeleton via actin-binding proteins. Association with actin filaments is required for caveolae invagination from the plasma membrane. Caveolae internalization and trafficking require posttranslational modification of caveolin-1 and actin-binding proteins. Internalized caveolar vesicles eventually tether to the abluminal membrane, followed by vesicle fusion via SNARE proteins and exocytosis of cargo into the subendothelial space. Experimental evaluation of caveolar transcytosis often requires the use of multiple techniques, including transmission electron microscopy and transwell studies. Lipopolysaccharide, hydrogen peroxide, and activated neutrophils increase transcytotic events in lung endothelial cells, and thus transcytosis contributes to the pathogenesis of acute lung injury. Introduction, or transcellular vesicular transport, generally describes the intracellular movement of relatively large (>10 kda) macromolecules within vesicles through epithelial and endothelial cells (64, 69, 179, 276, 308). in health may contribute to serum protein homeostasis (e.g., Immunoglobulin G transport via the neonatal Fc receptor) or disease progression (e.g., low-density lipoprotein transport in endothelial cells, contributing to the development of atherosclerosis) (72, 105, 135). A variety of macromolecular cargo is transported via transcytosis, including albumin, low-density lipoproteins, immunoglobulins, insulin, and lipids (105, 147, 153, 237, 292). has been reported in several organs, including the lungs, heart, brain, and intestines (7, 185, 209, 342). Endothelial cells, which comprise the tunica intima (the innermost layer of all blood vessels), form a tight monolayer that restricts bulk transport of fluid and protein leakage (131, 132, 179, 311, 320). However, regulated cellular transport allows a fraction of circulating plasma proteins to traverse through the endothelial layer (308, 334, 336). Cells utilize several forms of cargo uptake, including phagocytosis (e.g., macrophages, dendritic cells), pinocytosis (a form of *Correspondence to 1 Department of harmacology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA 2 Department of Anesthesiology, College of Medicine, University of Illinois at Chicago, Chicago, Illinois, USA ublished online, April 2020 (comprehensivephysiology.com) DOI: /cphy.c Copyright American hysiological Society. Volume 10, April

2 receptor-independent endocytosis), and receptor-mediated endocytosis (49, 56, 58, 67, 182). Lung endothelial cell transcytosis of serum proteins is an energy-driven process that integrates both receptor-mediated endocytosis and intracellular vesicular transport to deliver cargo from the blood plasma to the subendothelial or interstitial space (55, 137, 336). In contrast, paracellular transport describes movement of molecules (typically fluid and small molecular weight proteins) between cells (132, 320). Research over the last 50 years has uncovered a wealth of information regarding transcytosis in endothelial cells. The bulk of internalized plasma protein is transported via caveolin-coated vesicles that are assembled and trafficked from the Golgi apparatus to the plasma membrane (81, 138). Endothelial cells express a significant quantity of flask-shaped vesicles that are exposed to the vessel lumen and form a linear array along the plasma membrane (65, 209). These vesicles, termed caveolae for their resemblance to little caves, comprise the overwhelming majority of endocytic vesicles in endothelial cells (277, 327). Cargo entry into caveolae stimulates vesicle internalization (35, 76, 120, 175, 345). Consistent with these findings, the majority of studies implicate a predominant role for caveolae-mediated transcytosis in macromolecule transport in endothelial cells (188, 231). Hence, this article will describe the current understanding of the basic biology of caveolae, caveolae-mediated endocytosis, trafficking, and fusion and exocytosis of caveolae. We will also discuss the contributions of transcytosis to the pathogenesis of acute lung injury (ALI). Structure and Biochemical roperties of Caveolae Caveolae are 40 to 80 nm omega-shaped invaginations of the plasma membrane and free cytoplasmic vesicles within cells (36, 218, 286). These vesicles were first characterized in heart endothelium (216), but caveolae are observable in many cell types including endothelial cells, adipocytes, fibroblasts, and smooth muscle cells (38, 57, 172, 223). Endothelial caveolae can be distinguished from other vesicles by high-resolution electron microscopy based on their linear arrangement in the plasma membrane and characteristic surface defined by approximately 10 nm ridges (220). These ridges form a striped ring around the inner vesicle, which appears to have a dimpled surface. The ridges converge into a plane parallel to the plasma membrane in both directions, giving rise to a so-called bi-polar appearance that is morphologically distinct from other vesicles in endothelial cells. Caveolae comprise approximately 15% to 20% of the total endothelial cell volume (114, 277). Analysis of different tissues revealed that 45% to 70% of caveolae reside in the plasma membrane (21, 205, 224). Specific features of caveolae might vary between cells. For example, the caveolar neck domain, which recruits fission GTases and actin-binding proteins, has a larger diameter in endothelial cells than in fibroblasts (245). The increased neck size may be important for transcytosis, as this provides greater surface area for plasma cargo to collect inside the vesicles. It is important to note that caveolae number also varies between cell types, with the highest density found in venular endothelium (1200 caveolae/μm 3 ) (275, 277). Caveolae are rich in cholesterol and sphingolipids, which allows for these microdomains to be classified as a lipid raft (136, 140, 244, 265). Rafts are resistant to extraction with nonionic detergents, allowing for their separation from nonraft membrane domains, cytoplasm, and other cellular organelles using biochemical methods (20, 59). Depletion of membrane cholesterol using methyl-β-cyclodextrin results in loss of caveolae, demonstrating that cholesterol is required for caveolae stability (19, 50, 91). The localization of specific phospholipids in caveolae is also important since the loss of phosphatidylserine reduces caveolae formation (101). Moreover, phospholipid-associated protein phospholipase Cβ1 regulates caveolae number (108). In contrast, overexpression of phospholipase Cβ1 causes membrane tubulation (108). Interrogation of caveolae function in endothelial cells advanced further after the discovery of caveolin-1, the first identified protein in caveolar vesicles (75, 250). Caveolin-1, a 22 kda protein first identified in transformed fibroblasts, comprises the ridges of the cytoplasmic caveolar vesicle coat (24, 141, 250). Caveolin-1 has a central hydrophobic domain (amino acids ) that forms a hairpin structure in the plasma membrane, whereas its amino terminus (amino acids 1 101) and carboxyl terminus ( ) are hydrophilic and oriented toward the cytoplasm (169, 256, 282). While caveolin-1 is a definitive component of caveolae, it is also found in noncaveolae membrane domains (92, 193). Caveolin-1 has two isoforms, α and β, which are expressed in different proportions in various cell types (62, 130). Lung endothelial cells express primarily the α isoform, whereas type I alveolar epithelial cells primarily express the β isoform (130). Depletion of caveolin-1 results in loss of caveolae in cultured cells and in vivo (35, 242, 321). Later studies revealed that caveolin-1 is required for inducing membrane curvature and sequestering cholesterol in caveolar membranes (11, 103, 248). Since its discovery, two additional caveolins have been identified (aptly named caveolin-2, caveolin-3) along with caveolin-associated proteins called cavins (cavins 1 4) (14, 86, 98, 178, 255, 300). Caveolin-1 forms homo-oligomers (> kda) in the caveolar coat, along with hetero-oligomers with other caveolin proteins (191, 192, 253, 254). Additionally, cholesterol sequestration is required for caveolin-1 oligomerization and recruitment of caveolin-1 to the plasma membrane (191, 198). It is currently unknown whether caveolin hetero-oligomers are necessary for the formation or function of caveolae. Nevertheless, caveolin-1 and caveolin-2 proteins are expressed in several cell types (e.g., endothelial cells, fibroblasts, adipocytes), while caveolin-3 is restricted to muscle cells (46, 300). Expression of caveolin-1 is sufficient for caveolae formation, but caveolae expression in muscle appears to require both caveolin-3 and syndapin III 492 Volume 10, April 2020

3 (243, 264, 300). Indeed, expression of caveolin-1 alone is sufficient for de novo caveolae formation in cultured cells and in vivo (61, 199). Generation of genetic knockout mice has led to greater understanding of the role of caveolins and caveolae-associated proteins in mammalian physiology. Depletion of caveolin-1 in vivo results in hypercellularity of the pulmonary endothelium (170, 242). Additionally, caveolin-1 knockout cells exhibit an increased level of endothelial nitric oxide synthase (enos) activity, which has been associated with the development of cardiomyopathy and pulmonary hypertension (262, 273, 340, 341). Caveolin-1 deficient mice exhibit deficits in T cell migration (Th1) in an experimental autoimmune encephalomyelitis model (168). Alterations in the distribution of B cell antigen receptor clusters have been observed in lymphocytes isolated from caveolin-1 null mice (187). Interestingly, global caveolin-1 deletion in mice is protective against lipopolysaccharide (LS)-induced endotoxemia, significantly improving survival compared to wild-type controls (109). Finally, caveolin-1 null mice demonstrate lipodystrophy and hyperlipidemia (241). Investigation of caveolin-2 knockout mice surprisingly revealed that caveolin-2 is dispensable for caveolae formation (243). However, these mice demonstrated hypercellularity and higher proliferation rates in the pulmonary endothelium and marked exercise intolerance (243, 324, 325). Lipid abnormalities were not reported in caveolin-2 null mice. In contrast to caveolin-1 null mice, caveolin-2 deficiency increases mortality in mice following exposure to endotoxin (42). Caveolin-3 deletion in mice results in loss of caveolae in muscle cells but not in endothelial cells (300). Loss of caveolin-3 in muscle cells results in T-tubule abnormalities and loss of dystrophin-glycoprotein complex from lipid rafts (22, 66). Caveolin-3 deficiency prevents serotonin-mediated constriction of extrapulmonary airways; however, intrapulmonary airways exhibit an increased constriction response to muscarine compared to wild type mice (124). Caveolin-3 is expressed at the neuromuscular junction, where it regulates clustering of the nicotinic acetylcholine receptors (97). Additionally, caveolin-3 knockout mice exhibit adiposity and insulin resistance (26, 214). atients with caveolin-3 mutations 28L and R26Q exhibit fewer membrane caveolae and altered IL6/STAT3 signaling (46). To our knowledge, the roles of caveolin-2 and caveolin-3 in caveolae-mediated transcytosis have not been reported in the literature. In addition to their role in transcytosis, caveolae also function as signaling centers in cells. The caveolin-1 scaffolding domain (CSD; amino acids ) recruits receptors and kinases to caveolae, resulting in a signaling microdomain (141, 154, 328). Some of these receptors specifically bind plasma macromolecules, which subsequently activate nearby signaling effectors that initiate endocytosis (105, 110, 121, 162). Caveolae also regulate vascular pressure due in large part to the presence of enos which interacts with caveolin-1 via the CSD, thus basally inhibiting its activity and also inactivating enos following transient activation (225, 340, 341). Ion channels, heterotrimeric G proteins, and effectors of Ras signaling are also localized on or in caveolae (89, 154, 211, 281). Additional caveolae coat-associated proteins have been identified over the past two decades, namely the cavin family of proteins. There are four cavin proteins that have been identified (14, 86, 98, 178). Cavin-1 (polymerase I and transcript release factor) and cavin-2 (serum deprivation-response protein) are the most well studied of these proteins. Similar to caveolin-1, both cavin-1 and cavin-2 are required for caveolae formation and abundance (88, 158, 160, 305). Cavin-1 is targeted to the caveolar coat through its interaction with phosphatidylserine (98). Cavin-1 also binds to phosphatidylinositol bisphosphate, which along with phosphatidylserine is required for caveolae formation (24, 134). Cavin-1 is required for caveolin-1 oligomerization, although it does not directly interact with caveolin-1 (24, 160). However, the addition of a cross-linking reagent to cells prior to harvest has revealed that caveolin-1 associates with cavin-1 in a 1:4 ratio (164). Cavin-1 binds to cavin-2, which is essential for its targeting to caveolae (86). Cavin-1 null mice lack caveolae and develop muscle hypertrophy, which was attributed to constitutive Akt signaling (47). Additionally, cavin-1 deficiency causes progressive cardiac hypertrophy and fibrosis, which was associated with increased ERK1/2 signaling (301). Cavin-2 deletion in vivo results in loss of endothelial caveolae in lung and adipose tissue but not loss of caveolae in heart endothelium (88). Moreover, cavin-2 directly influences the curvature of the plasma membrane and normal caveolae shape in vivo (86). In cultured endothelial cells, cavin-2 depletion reduces nitric oxide production, endothelial cell migration, invasion, proliferation, and angiogenesis (16). Interestingly, cavin-3 deletion does not result in any loss of caveolae in lung endothelial cells, fibroblasts, and adipocytes but does perturb caveolae abundance in smooth muscle cells (88, 159, 343). Cavin-3 depletion in fibroblasts increases Akt phosphorylation and reduces ERK1/2 signaling, while overexpression of cavin-3 has the opposite effects (95). Cavin-4 is expressed only in myocytes, similar to caveolin-3 (14, 208). Overexpression of cavin-4 in vitro increases caveolae area in cardiomyocytes (207). Loss of cavin-4 is protective against phenylephrine-induced concentric hypertrophy and hyperactive ERK1/2 signaling (207). The Role of Caveolae in Transcellular Transport Analysis of permeability in different vascular beds with molecular tracers of varying size and chemical properties led to the development of the endothelial pore theory (217, 246). The two-pore model postulates that endothelial cells possess a relatively small population (<0.1% of total pores) of pores (radii nm) that mediate transport of large plasma macromolecules. Small pores were postulated to have a size of roughly approximately 10 nm. However, evidence Volume 10, April

4 (A) WT (B) Cav-1 / Cap. Cap. Figure 1 of Au-albumin in mouse lung. (A) Au-albumin uptake from the capillary lumen is transported via caveolae toward the subendothelial space. Caveolae reside attached to the plasma membrane and as free intracellular vesicles within lung endothelial cells. Vesicular invaginations of the plasma membrane mediate tracer albumin uptake (black arrows) leading to internalization and exocytosis (arrowhead). The majority of albumin in healthy endothelial cells is transported through caveolae, while paracellular transport is restricted by junctional proteins (green arrow). (B) Absence of Au-albumin transport in caveolin-1 knockout (Cav-1 / ) mouse lung endothelium. Genetic deletion of caveolin-1 resulted in the elimination of caveolae and thereby vesicular uptake and transport of Au-albumin tracer. Caveolin-1 deficiency is associated with increased enos activity and loss of junctional integrity (green arrow) resulting in paracellular transport of Au-albumin in Cav-1 / lung endothelium but not healthy controls. for permanent, large, open pores in continuous endothelium of the lung has not been reported. Grotte (83) demonstrated that dextrans of varying radii (1 10 nm) injected into the blood appear in lymphatic capillaries in a size-dependent manner for tracers less than approximately 5 nm. Dextrans with radii greater than 10 nm are transported across most continuous-type endothelium, with minor differences (83, 142). Further, studies revealed that plasma proteins (e.g., albumin, ferritin, myoglobin) and large molecular weight nonphysiological tracers (e.g., terbium) are internalized via caveolae (21, 185, 278, 314). Since the caveolar neck diameter is typically approximately 25 nm, caveolae are regarded as the large pore system in endothelial cells. In addition to caveolae, endothelial cells contain other transient organelles that may have importance in fluid and solute permeability. These include vesicular-vacuolar organelles (VVOs) and trans-endothelial channels (TECs) (51, 52, 287). VVOs are present in normal venular endothelium and tumor endothelium (51, 52, 156). Macromolecules extravasate through endothelial VVOs in response to classical permeability factors (e.g., vascular endothelial growth factors, serotonin, and histamine) (51, 52, 156). It is currently not known whether VVOs are fused caveolar vesicles or caveolae-independent structures. However, VVOs have been identified in flank skin of caveolin-1 null mice, suggesting that caveolae are not required for de novo VVO formation (30). Interestingly, VVOs have not been observed in capillaries, an important observation since numerous studies have demonstrated transcellular transport of large molecular weight proteins in lung, aortic, heart, and mesenteric capillary beds. Moreover, caveolin-1 deletion in mice results in both loss of caveolae and reduced transcellular transport of albumin (261, 297). These findings suggest that VVOs are not primary mediators of macromolecule transport under basal conditions, especially in capillary endothelium. To our knowledge, the role of caveolin-2, caveolin-3, and the cavins (1 4) in VVO formation and stability in endothelial cells is not known. TECs are mostly absent from continuous endothelial cells but are observed in fenestrated endothelium in the kidney cortex, duodenal mucosa, and exocrine pancreas (184, 287). It is thought that these structures are formed by the fusion of caveolae, creating a pore that is spanned by a diaphragm on the apical and basal plasma membranes. It is not known whether TECs are present in the absence of caveolin-1 or other caveolae-associated proteins. Although once challenged as unlikely, the evidence for a vesicular transport pathway has been supported by numerous independent studies. Uptake of labeled plasma protein into caveolar vesicles has been reported by several independent groups (185, 278, 314). Exocytosis of cargo into the subendothelial space has also been observed in electron micrographs (230). Moreover, loss of caveolin-1 in vivo reduces albumin internalization and transcytosis in endothelial cells (261) (Figure 1). Finally, total internal reflection fluorescence (TIRF) microscopy of endothelial cells revealed that green fluorescent protein (GF) tagged-caveolin-1, often used to identify caveolae in live imaging studies, rapidly internalizes when exposed to albumin (112, 345). Taken together, these and other studies indicate that caveolae are the primary mediators of transcellular transport in endothelial cells. During transcytosis, the caveolar coat undergoes modifications that result in vesicle swelling (345). Caveolae subsequently undergo dynamin-dependent fission from the plasma membrane, followed by cytoskeletal rearrangements that facilitate the movement of vesicles (94, 196). Finally, vesicles must fuse with the abluminal plasma membrane in order to release their contents into the subendothelial space (257). Broadly, transcytosis can be categorized by as: (i) endocytosis, (ii) trafficking, and (iii) exocytosis. Endocytosis Endocytosis refers to the internalization of cargo from the external milieu into the cytoplasm of the cell (49, 99, 252). The ability of cargo to be internalized by caveolae vesicles 494 Volume 10, April 2020

5 (1) Src ITSN1 Receptor activation enos ITSN1 ITSN1 ITSN1 ITSN1 ITSN1 (2) (3) Src activation Src NO enos L-Arginine Vesicle filling/ swelling Src enos Endocytosis Dynamin (4) Figure 2 Mechanism of receptor-mediated endocytosis. (1) Serum albumin binds and activates albuminbinding protein gp60 in caveolae and on the plasma membrane proper. (2) Ligation of gp60 results in its clustering and G βγ and nitric oxide-mediated activation of Src kinase. (3) Src subsequently phosphorylates caveolin-1 (Y14), destabilizing caveolin-1 oligomers and causing vesicle swelling. Caveolin-1 Y14 phosphorylation subsequently inhibits further nitric oxide production, thereby limiting local Src activation in caveolae. Finally, phosphorylated dynamin-2 is recruited from the cytosol to the caveolar neck via the SH3 domain of intersectin-1. (4) Dynamin-2 subsequently oligomerizes and initiates GT-dependent fission of caveolae from the plasma membrane. These events result in internalization of caveolae. depends on cargo radius and presence of a specific receptor for the cargo (116, 135, 227, 334). The effect of molecular radius on caveolae-mediated endocytosis was demonstrated by redescu et al. (227). Briefly, internalization and transcytosis of orosomucoid-dinitrophenyl (DN), a glycoprotein with 10 nm radius, were significantly more efficient than orosomucoid-gold ( 22 nm radius). Gold-labeled orosomucoid was trapped in the neck of the luminal and abluminal caveolae, resulting in fewer particles in the subendothelial space. Caveolae-mediated endocytosis is initiated by the interaction of plasma macromolecules with their receptors, which in some cases are recruited to caveolae via interaction with the caveolin scaffolding domain. Interaction between macromolecule ligands with receptors results in activation of signaling effectors and caveolar fission (39, 70, 268, 304). Indeed, specific knockdown of macromolecule receptors in endothelial cells results in diminished endocytosis (63, 135, 163, 237). Tracer studies have suggested that endocytosis may be restricted by caveolar diaphragms which span the neck of lung endothelial cell caveolae (286). Caveolae with diaphragms seemingly have little if any tracer in them, while diaphragm-free caveolae are filled with tracer (312). The first and only identified protein to localize in caveolar diaphragms is plasmalemmal vesicle-associated protein 1 (V-1, LVA) (287, 289). V-1 is a 60 kda glycoprotein that dimerizes and self-oligomerizes, thereby contributing to the diaphragm s spoke-like structure (285, 288). Overexpression of V-1 is sufficient to generate de novo diaphragms in nonendothelial cells (290). Further, V-1 is required for diaphragm formation since loss of V-1 results in loss of caveolar diaphragms (239, 240, 291). A single study that employed electron tomography in cultured cells concluded that caveolae with diaphragms exhibit a wider neck diameter than diaphragm-free caveolae (245). Whether diaphragms actually restrict endocytosis or regulate caveolar neck dynamics is of great interest and requires further study. Albumin is the most studied cargo in transcytosis studies, although internalization of other macromolecules shares a mechanism similar to that of caveolae-mediated albumin transport (71, 125, 174, 295, 316, 317). Albumin transcytosis is initially receptor dependent but is also mediated by a fluid-phase, receptor-independent transport mechanism (116). Here, we describe what is currently known about receptor-mediated endocytosis of albumin (Figure 2). Receptor activation Albumin, a 66 kda protein that constitutes over half of the plasma protein, stimulates its own endocytosis after binding to a specific receptor on the endothelial cell surface (27, 31, 85, 181). Albumin transport is receptor dependent since greater than 80% of labeled albumin internalization can be inhibited by a 1000-fold excess of unlabeled albumin (116). gp60 (albondin), identified as the albumin receptor in endothelial cells, is a 60 kda glycoprotein that localizes to caveolae and interacts with caveolin-1 through its caveolin Volume 10, April

6 scaffolding domain (189, 274, 302). gp60 is also expressed in epithelial cells (115). Depletion of gp60 receptors diminishes albumin uptake and transcytosis (116, 259). gp60 receptors cluster within 15 min of albumin binding or gp60-antibodyinduced cross-linking (304). This results in activation of G αi subunit and disassociation from G protein G βγ subunit (269). In fact, immunostaining of G αi at the surface decreases after gp60 activation and loss of G αi activity via pertussis toxin or dominant-negative mutants prevents gp60-induced vesicle internalization (189). Src activation c-src, commonly referred to as Src, is a 60 kda nonreceptor tyrosine kinase that localizes to caveolae in endothelial cells (143, 151). gp60-dependent albumin transport is mediated by activation and autophosphorylation of Src family tyrosine kinases (85, 270, 304). Subsequent studies revealed that gp60 receptor clustering results in disassociation of G βγ which leads to Src phosphorylation at active-site tyrosine-416 (189, 269). Earlier studies in nonendothelial cells suggested a link between G βγ subunits and Src activation since overexpression of G βγ induces Src phosphorylation (3, 166, 167). The mechanism through which G βγ activates Src in endothelial cells is unclear. Several studies indicate that calcium release results in Src activation (8, 74, 293, 326, 339). Consistent with these results, calcium ionophore activates Src (74, 319, 323). The calcium ionophore A23187 stimulates albumin transport in endothelial cells under moderate extracellular calcium conditions (5). Calcium release in both human embryonic kidney cells overexpressing enos and endothelial cells activates enos via phosphorylation on serine-1177 resulting in nitric oxide release and Src activation (34). In cultured endothelial cells, binding of enos to GIT1 (G-protein-coupled receptor kinase-interacting protein-1) stimulates NO release (161). Interestingly, G βγ subunits mediate downstream activation of Src and phosphorylation of GIT1, allowing for enos to interact with GIT1 (161). Loss of enos prevents calciuminduced Src activation in these cells (34). Chen et al. (35) demonstrated that loss of enos results in less albumin transport in endothelial cells. Together, these results suggest that Src activation is calcium and nitric-oxide dependent. Caveolin-1 phosphorylation Caveolin-1 was first identified as a tyrosine-phosphorylated protein in Rous Sarcoma virus-transformed fibroblasts (75). However, caveolin-1 phosphorylation is tightly regulated in endothelial cells. Later studies confirmed that Src kinase phosphorylates the caveolin-1 α isoform on its amino terminus at tyrosine-14 via direct Src-caveolin-1 interaction (79, 139, 152, 206). Albumin binding or gp60 receptor cross-linking results in caveolin-1 phosphorylation, which is inhibited by tyrosine kinase inhibitors and caveolin-1 Y14F mutant (213, 268, 270). almitoylation of caveolin-1 at cysteine-156 is required for caveolin-1 phosphorylation since C156S mutant expression prevents direct binding of Src to caveolin-1 (144). In cultured endothelial cells, forced expression of a constitutively active Src mutant increases internalized vesicle abundance and caveolae diameter (9). Zimnicka et al. (345) reported that overexpression of caveolin-1 Y14D, a phospho-mimicking caveolin-1 mutant, results in caveolar vesicle swelling, increased caveolar vesicle internalization rates, and increased caveolar vesicle trafficking. Further, forced expression of caveolin-1 Y14D mutant yields fewer caveolin-1 oligomers (>250 kda) in lung endothelial cells suggesting that caveolin-1 oligomers restrict the volume of the caveolar bulb. In contrast, caveolin-1 Y14F mutant expressing endothelial cells exhibit fewer internalized caveolar vesicles. Thus, phosphorylation of caveolin-1 promotes cargo internalization into endothelial cells and caveolar vesicle release. hospho-caveolin regulates enos via direct interaction, thereby restricting further NO release, Src activation, and further phosphorylation of caveolin-1 (34). Indeed, loss of caveolin-1 increases enos phosphorylation and NO release in cultured endothelial cells (35). In addition to its role in regulating vesicle dynamics and caveolin-1 oligomerization, phospho-caveolin also regulates caveolae biogenesis in MDA-231 cells (118). Indeed, cells expressing caveolin-1 Y14D mutant express higher quantities of caveolin-1 and cavin-1 proteins which correspond with an elevated number of caveolae (118). This effect on caveolae biogenesis is mediated by loss of Egr1 suppression. This finding, taken together with studies in endothelial cells, suggests that phospho-caveolin provides a feedback mechanism at the level of transcription to ensure that caveolae vesicles are present at the membrane for cargo internalization (345). Caveolae fission via GT-driven dynamin-2 Caveolar vesicles detach from the plasma membrane following gp60 activation, a process known as fission. Fission of caveolae is a GT-driven process (234, 260). GT hydrolysis stimulates caveolae release while GTγS, a mutant form of GT, fails to induce caveolae internalization (260). Dynamin- 2, a 100 kda GTase, hydrolyzes GT and thus provides the energy for caveolar fission (94, 272). Dynamin-2 is a cytosolic protein that is phosphorylated by Src kinase on tyrosine-231 and tyrosine-597, which subsequently increases its interaction with caveolin-1 (2, 60, 272). Expression of dynamin mutants or treatment with dynasore (a dynamin inhibitor) restricts caveolae budding and fission in cells (4, 18, 210, 307). Dynamin-2 is also required for caveolae-mediated endocytosis of other ligands, including viral particles (68, 337, 338). Dynamin-2 phosphorylation results in its oligomerization and recruitment to the caveolar neck (127, 249, 268). A single study concluded that dynamin-2 forms a tetramer (249). However, this study did not evaluate dynamin-2 oligomer formation during cargo-driven endocytosis. 496 Volume 10, April 2020

7 Intersectin-1s, a short isoform of intersectin-1, is expressed in endothelial caveolae in the caveolae neck domain (234). The short form of intersectin-1 is also critical for clathrinmediated endocytosis in neurons, while the long form of intersectin-1 is required for actin assembly (106, 107). Intersectin-1s is required for caveolae fission, as its depletion in a cell-free system resulted in failure of GT to stimulate vesicle release (234). In addition, intersectin-1s forms a membrane-tethered protein complex with dynamin-2 and SNA23 (234). Silencing of intersectin-1s results in loss of caveolae and impaired endocytosis (12, 229). Interestingly, overexpression of intersectin-1s or its SH3 domain results in abnormal caveolae and vesicular organelles (129). These caveolar defects were accompanied by disrupted endocytosis (129). Together, these data suggest that intersectin-1s is required for caveolae formation, caveolae-mediated endocytosis, and dynamin-2 recruitment to the caveolar neck where it directs caveolae fission. Internalization and Trafficking via Caveolae-actin Interactions Internalized vesicles that have detached from the endothelial cell plasma membrane represent 30% to 55% of the caveolae content in endothelial cells (21, 205, 224). Once vesicles are released, caveolae migrate to the abluminal side of the cell in order to release their contents into the subendothelial space. Relatively little is known about caveolar trafficking, despite being an essential component of transcytosis. The available evidence suggests that caveolae are anchored to the plasma membrane by actin filaments. Early electron microscopy studies in myofibroblasts and mouse embryonic fibroblasts demonstrated that caveolae are associated with actin fibers (247, 279). Later studies supported these findings by demonstrating that caveolin-1 co-localizes with actin (250). In migrating cells, phospho-caveolin targets Src to focal adhesions and also associates with integrins (17, 203). Specifically, phospho-caveolin recruits focal adhesion kinases (FAK) to focal adhesions, thereby enhancing focal adhesion turnover and formation (77). Additionally, phosphocaveolin interacts with vinculin and focal adhesions more so than nonphosphorylated caveolin (28, 77, 180, 203, 310). Transport of cholesterol-enriched membrane microdomains requires phospho-caveolin (45). These findings suggest that caveolin-1 phosphorylation alters cytoskeletal dynamics. Interestingly, caveolin-1 expression regulates actin dynamics. Indeed, caveolin-1 is necessary for actin polymerization since caveolin-1 deletion reduces actin organization in cells (195). In addition, caveolin-1 depletion disrupts the actin cytoskeleton and reduces RhoA GTase activity but increases Rac1 protein and activity (80, 202, 238). In adipocytes, cavin-1 is required for aggregation of vinculin, paxillin, and FAK into focal adhesion complexes under baseline conditions and relocates from lipid rafts to focal adhesions following insulin stimulation (315). Actin filament dynamics are critical for both membrane invagination and scission of vesicles. Loss of the actinbinding regions of clathrin adaptors ENT1 and SLA2 in yeast impairs actin-mediated plasma membrane invagination and endocytosis (222, 280). This suggests that either actin polymerization or recruitment of actin filaments to the plasma membrane might be required for vesicle invagination. Actin turnover regulates clathrin vesicle internalization, as jasplakinolide, an inducer of actin polymerization, prolongs clathrin vesicle maturation, and endocytosis (332). In contrast, actin polymerization inhibitors increase internalization events. Similarly, actin depolymerization shifts caveolin-1-gf positive vesicles from the cell surface to actin patches (294). Moreover, cytochalasin-d, an inhibitor of actin polymerization, reduces albumin uptake in rat pulmonary endothelial cells, possibly due to the lack of available membrane caveolae (150). Caveolin-1 dependent uptake of Leptospira interrogans is reduced in cytochalasin-d treated endothelial cells (155). Interestingly, SV-40 infection in fibroblasts results in actin filament breakdown (219). On the other hand, jasplakinolide treatment impaired caveolin-1 dependent human coronavirus OC43 infection in HCT-8 cells (215). Together, these studies suggest that actin filaments are required to support caveolae localization at the plasma membrane and that caveolae-mediated internalization triggers remodeling of the cytoskeleton to initiate trafficking (Figures 3A and 3B). In addition to direct caveolin-actin interactions, caveolae recruit actin-associated proteins to the plasma membrane. These interactions subsequently regulate actin stability and caveolae internalization. Dynamin-2, which is recruited from the cytosol to facilitate the scission of caveolae, removes capping protein gelsolin from actin filaments, thus allowing for actin elongation (41, 78, 84). EHD2, an ATase that forms oligomers within the caveolar neck, restricts caveolae to the plasma membrane (294). Deletion of either EHD2 or its AT-binding domain results in loss of the linear array of caveolae along actin filaments and increases the number of internalized caveolar vesicles (102, 194, 331). EHD2 interacts with F-BAR domain protein pacsin2 (194). acsin2, an approximately 56 kda protein that interacts directly with F-actin, is recruited to caveolae and is required for caveolae formation (87). Loss of pacsin2 increases both caveolae neck diameter and depth of caveolae invagination while reducing dynamin recruitment to membrane caveolae (266). Moreover, phosphorylation of pacsin2 by protein kinase C reduces pacsin2 localization to caveolae and promotes vesicle internalization (267). Filamin A, a 280 kda actin cross-linking protein, interacts with both caveolin-1 and actin stress fibers (111, 201, 298). Filamin A is required for actin-dependent caveolin-1 localization along the plasma membrane (200, 298). Loss of filamin A increases the motility of caveolin-1 and reduces its interaction with stress fibers (200). Therefore, filamin A is also required for actin-mediated anchoring of caveolae at the plasma membrane. roper inward trafficking of caveolae requires KCα-mediated-phosphorylation of filamin A at serine-2152 Volume 10, April

8 YF-actin BSA-AF 549 (A) (B) (C) FLNA Actin polymerization Cdc42 GT GT Cdc42 GD EHD2 ACN2 CAV1 EHD2 ACN2 FLNA Rac1 GT RhoA GT (D) KC FLNA ACN2 KC FLNA KC ACN2 KC Arp2/3 complex (formin) mdia Cdc42 Cdc42 GT GD CAV1 CAV1 CAV1 Actin depolymerization Actin polymerization FLNA FLNA KC FLNA RalA EHD2 EHD2 Cytochalasin D C LD2 A Endocytic vesicle Figure 3 Actin dynamics during caveolae internalization. Rat lung microvascular endothelial cells demonstrating actin organization at baseline (A) and following exposure to albumin (B). Actin patches (arrowheads) visible following albumin exposure. (C) Caveolae neck proteins, filamin A, and Rho GTases work in concert to promote actin polymerization and actin filament stability, thus maintaining a linear array of caveolae at the plasma membrane. (D) Receptor activation by macromolecules results in caveolin-1 phosphorylation and KC-mediated phosphorylation of pacsin2 and filamin A, promoting vesicle internalization. hospho-caveolin interacts with several effectors of caveolae internalization, including Cdc42, filamin A, and RalA. Cdc42-GD binding to phospho-caveolin prevents its conversion to the GT bound state, reducing actin polymerization. RalA is recruited to caveolae along with filamin A, resulting in downstream activation of LD2, production of phosphatidic acid, and subsequent endocytosis. (200). Moreover, filamin A is recruited to caveolae following Src dependent-phosphorylation of caveolin-1 and is required for albumin endocytosis in endothelial cells (298). Filamin A binding to inositol requiring enzyme 1 is required for its phosphorylation at serine-2152, thus regulating filamin A s actin cross-linking activity (309). Immunoprecipitation studies in human lung endothelial cells reveal that RalA, a small Ras GTase, associates with both filamin A and caveolin-1 during albumin uptake in lung endothelial cells (112). Binding of albumin results in RalA-mediated LD2 activation and subsequent phosphatidic acid production, a known effector of membrane curvature (Figures 3C and 3D) (112, 133). Monomeric GTases, small 21 kda GTases of the Rho family that are also involved in cell cycle dynamics, have been implicated in vesicle trafficking from the plasma membrane (53). Rac1 and RhoA are enriched in caveolae/lipid raft fractions isolated from cultured cells, and Cdc42 directly binds to caveolin-1 (10, 73, 183, 190, 204). Rac1, RhoA, and Cdc42 act upstream of actin polymerization. Rac1 interacts with WAS (Wiskott-Aldrich syndrome protein) family members to form a WAVE regulatory complex, which signals to the Arp2/3 complex to initiate actin filament polymerization (32, 100). Inhibition of Rac1 reduces clathrin-independent endocytosis (283). RhoA promotes actin elongation via mdia1, a formin that facilitates actin-capping (13, 333). In addition to actin polymerization, RhoA also acts upstream of cofilin, which promotes severing of actin filaments (146, 176, 235). Loss of cofilin delays internalization of Sla1- positive (a marker for clathrin) vesicles (212). Similar to Rac1 and RhoA, Cdc42 is required for actin assembly and reorganization following extracellular stimulation (37, 106). Specifically, Cdc42 is required for actin polymerization (33, 48, 299). Depletion of Cdc42 disrupts both F-actin at the apical plasma membrane and vesicle trafficking in acinar cells (271). hospho-caveolin-1 binds GD-bound Cdc42, resulting in caveolar endocytosis (37). Loss of caveolin-1 results in activation of Cdc42 in the absence of stimuli (Figures 3C and 3D) (37). These results suggest that phospho-caveolin restricts Cdc42-mediated-actin polymerization. Cdc42 also interacts with intersectin-2l and other regulators of the actin cytoskeleton (N-WAS, Arp2/3) (128). Loss of intersectin- 2L results in both impaired Cdc42 activation and F-actin reorganization but increased caveolae internalization (128). IQGA1 (p195), an effector of Rac1 and Cdc42, binds to caveolin-1, cavins 1 to 3, and EHD2 (119). Interestingly, silencing of IQGA reduces FM4-64 uptake, a marker for endocytic vesicles, in pancreatic tumor cells (126). Exocytosis Once caveolae have reached the abluminal membrane, vesicles must fuse with the plasma membrane in order to deposit cargo into the subendothelial space. Exocytosis describes a regulated process in which vesicles tether to the plasma membrane, followed by fusion of the vesicle lipid bilayer with that of the membrane to which it is tethered. In both yeast and mammalian cells, internalized vesicles are directed to specific locations on the plasma membrane via tethering proteins that collectively form an exocyst complex (173, 322). Eight proteins are thought to form the exocyst complex, 498 Volume 10, April 2020

9 although there remains unresolved understanding as to the formation and assembly of the complex at the plasma membrane (90, 157, 221). Exo70, a subunit of the exocyst complex, co-localizes with caveolin-1 at the plasma membrane in cells (96). Moreover, exo70 arrives at the plasma membrane prior to assembly of the complex and subsequent docking and fusion (1). Components of the exocyst complex might be present on both the migrating vesicle and the plasma membrane, allowing for targeting of the vesicle to a specific location (90, 157). Once a vesicle is tethered to the membrane, fusion proteins enable membrane integration of the vesicle lipid bilayer and deposition of cargo outside of the cell. Lung endothelial cells express many components of vesicle fusion and exocytosis machinery found in other cells (e.g., neurons). N-ethylmaleimide sensitive fusion protein (NSF), a 78 kda ATase known for its role in neurotransmitter release from the pre-synaptic membrane, is expressed in endothelial cells (329). Soluble NSF attachment protein receptor (SNARE) proteins are also enriched in caveolae vesicles (232, 258). Consistent with these results, treatment of endothelial cells with N-ethylmaleimide inhibits greater than 70% of the transport of albumin, myoglobin, and other tracers in the mouse heart and lung (226, 227, 231, 257). These studies, combined with albumin tracer studies in caveolin-1 null mice, provide strong in vivo evidence of transcytosis of macromolecules in endothelial cells. Lung endothelial cells express SNARE protein-lipid complexes that are present in both the cytosol and membrane (232). This finding suggests that endothelial cells, similar to neurons, express v-snare and t-snare proteins. These complexes also contain vesicle-associated membrane proteins (VAMs), dynamin-2, syntaxins, caveolin-1, and rab5 (232). VAM2 is required for cholera toxin trafficking in endothelial cells (177). Synaptosomal-associated proteins (SNAs) are 20 to 25 kda proteins expressed in SNARE complexes of many cell types, including neurons and endothelial cells (23, 344). SNA23 clusters with syntaxin-4 during caveolar fusion in lung endothelial cells (233). Experimental Methods for Assessing Endothelial Several strategies exist to determine endothelial transcytosis in both animals and in cell culture models. Using a combination of experimental strategies is necessary to determine (i) caveolae abundance (ii) percentage of caveolae involved in transport (iii) quantity of tracer per caveolar vesicle (iv) total amount of internalized tracer (v) rate of endocytosis (vi) rate of exocytosis. Importantly, each of these variables must be experimentally determined for each organ and vascular bed type since endothelial cells exhibit heterogeneity across different blood vessel types (e.g., arteries vs veins) and different organs (e.g., lung vs brain). Investigation of endothelial transcytosis, either in vivo or in vitro, requires the use of a labeled macromolecules. Labels refer to compounds (e.g., fluorescein isothiocyanate) that are covalently attached to macromolecules. In some cases, labels may alter macromolecule chemistry or reduce its stability (306). Thus, it is important to assess labeled macromolecule activity prior to its use in transcytosis experiments. The radius of the label is also important since relatively large labels might restrict uptake into caveolae vesicles and thus result in diminished transcytosis (227). Finally, label selection should be determined based on the type of experiment to be performed. Dense labels (e.g., colloidal gold) are particularly useful to visualize caveolar tracer transport via electron microscopy, while radiolabeled (e.g., iodine-125, carbon-14) are more useful for assessing quantitative transport in organs and cells. For studies investigating the specific route of transport of a given macromolecule, the use of an additional labeled molecule (one that is transported primarily between endothelial cells rather than vesicles) may be used to determine the relative contribution of transcytosis to total transport (197). This strategy, effective in both animal models and cell culture experiments, is also useful for evaluating transcytosis in disease models with moderate to severe endothelial junctional permeability (e.g., sepsis). In both intact organ preparations and cultured cells, transmission electron microscopy (TEM) is the method most frequently used to determine caveolae morphology, caveolae diameter, caveolae abundance, macromolecule quantity per vesicle and percentage of caveolae involved in transport in block preparations of tissue (228). TEM simultaneously allows for determination of relative junctional permeability. While TEM is essential for determining the route of transport in endothelial cells, it does not allow for quantitative assessment of total macromolecule internalization within a specific organ or blood vessel. Consequently, TEM provides answers as to whether internalization and/or transcytosis occurs but is not adequate for determining the kinetics of transport. To estimate total tracer transport, radiolabeled tracers are substituted in place of gold-labeled or fluorescent tracers. Radiolabeled macromolecules are preferred in quantitative transport studies due to their higher sensitivity and specificity (especially compared to fluorescent labels). Whole organs, tissues, and blood samples are analyzed for radioactivity using a gamma counter. The radioactivity that is reported represents the total amount of tracer that is internalized. However, assessment of transcytosis requires (i) determination of tracer present within the endothelial cells and (ii) determination of tracer transported via paracellular pathway. After perfusing intact lung preparations with radiolabeled albumin, Vogel et al. (313) demonstrated approximately 25% of tracer is present in lung endothelial cells, while 75% was completely transported to the subendothelial space. In this study, the authors used hypo-osmotic shock (brief perfusion of distilled water, thus causing rupture of endothelial cells) to release the tracer present within the endothelial cells. Volume 10, April

10 Assessment of the kinetics of transcytosis often employs the use of cultured endothelial cells. In general, endothelial cells are seeded on transwell inserts to assess exocytosis. An insert typically defines the upper chamber of a well within a 6, 12, or 24 well plate. The bottom chamber is the noninsert part of the well. Endothelial cell monolayers on the insert are subsequently exposed to labeled macromolecules, and media in the bottom chamber is collected at several time intervals to determine both total accumulation and rate of accumulation of macromolecules. Several considerations must be made prior to experimentation, including the use of organ-specific primary endothelial cells or endothelial cell lines, transwell pore filter size, mixed culture/coculture with nonendothelial cells, and cell confluence (which can be assessed using transendothelial electrical resistance techniques). Tracer uptake and imaging studies should be performed in conjunction with transwell studies to provide a full quantitative description of transcytosis (116). Live imaging studies in endothelial cells overexpressing fluorescent caveolin-1 protein allow for quantification of caveolin-1 trafficking following endocytosis, which presumably reflects the movement of caveolae (345). Assuming that the majority of transport occurs within the capillaries, endothelial membrane transport can be mathematically modeled by the Kedem-Katchalsky equations: J v = K f,c [(H cap H int ) σ(o cap O int )] J s = J v (1 σ)m cap + S(M cap M int ) where J v and J s indicate volume flux (e.g., water) and solute flux (e.g., albumin), K f,c is the volume filtration coefficient, H cap and H int indicate hydrostatic pressure of the capillary and interstitium, O cap and O int indicate osmotic pressure of the capillary and interstitium, M cap and M int indicate macromolecule concentration in the capillary and interstitium, σ is the reflection coefficient (measures the probability of a particular solute crossing the membrane) and S is the permeability-surface area product (which entails both probability of solute transport and the area available for macromolecule transport) (122). The volume flux equation is often used to assess microvessel or capillary permeability to an aqueous solution in animal studies. However, in typical transcytosis studies, the volume of labeled macromolecule solution is often several orders of magnitude less than the volume into which it is delivered. If the volume contributed by the macromolecule solution is negligible, J v = 0 and J s = S(M cap M int ) (1) At the beginning of the experiment, M int = 0. For a sufficiently short time interval ΔT, M cap > M int and Eq. (1) can be approximated as: J s = S(M cap ) (2) Since macromolecule flux is the total amount of macromolecule (M F ) internalized over a defined interval of time, Eq. (2) can be re-written as: M S = F (3) M cap ΔT S product is a useful parameter for assessing permeability of different macromolecules within a specific vascular bed, or permeability of the same macromolecule in different vascular beds (e.g., intestines, heart). Equation (3) can also be used to assess permeability in vitro since M F can be readily determined from an aliquot from the bottom chamber of a transwell system (M cap = M insert ). Endothelial in Lung Injury Lung endothelial cells are critical for maintaining osmotic pressure through fluid and protein plasma homeostasis (251, 284, 318). Endothelial barrier function is critical for oxygen diffusion and proper lung vascular perfusion (6). Loss of endothelial barrier integrity due to sepsis, acid aspiration, or trauma results in plasma protein extravasation and immune cell transmigration into the interstitial and alveolar spaces (15, 25, 171, 186). These events are defining features of ALI and acute respiratory distress syndrome (ARDS), which presently exhibit a 26% mortality rate (54). Unfortunately, clinical treatment of ALI/ARDS is primarily supportive therapy (117). A critical understanding of endothelial barrier dysregulation following injury may be useful in the development of targeted therapies that improve outcomes for afflicted patients. Several studies have observed increased paracellular permeability to both fluid and protein following ALI but also that endothelial transcytosis increases following exposure to LS, an endotoxin that is released from the cell wall of Gram-negative bacteria known to cause ALI (44, 93, 131). In mice, LS exposure increases both caveolae abundance and the number of vesicles transporting labeled albumin within 2 h of treatment, notably in the absence of detectable edema (93). This suggests that increased endothelial transcytosis precedes edema formation following ALI. Treatment of cultured lung endothelial cells with LS results in Src activation and caveolin-1 phosphorylation (113). Moreover, inflammatory signaling through TLR4, the primary LS receptor, is phospho-caveolin dependent (113). Liposome-mediated expression of a Y14F (phospho-defective) caveolin-1 mutant in caveolin-1 knockout mouse lungs prevented LS-induced pulmonary edema after 6 h and improved survival (113). LS increases radiolabeled albumin permeability in lung endothelial cells in vitro (43, 303). Together, these studies indicate that LS alters albumin transport in endothelial cells by increasing transcytosis after injury. Finally, thrombin, a procoagulant factor that converts fibrinogen into fibrin, is thought to contribute to fibrin deposition and accumulation following sepsis-induced ALI (149, 236). Thrombin, well known for inducing paracellular permeability, also increases albumin transcytosis in both mouse lungs and cultured lung 500 Volume 10, April 2020

1.1.2. thebiotutor. AS Biology OCR. Unit F211: Cells, Exchange & Transport. Module 1.2 Cell Membranes. Notes & Questions.

1.1.2. thebiotutor. AS Biology OCR. Unit F211: Cells, Exchange & Transport. Module 1.2 Cell Membranes. Notes & Questions. thebiotutor AS Biology OCR Unit F211: Cells, Exchange & Transport Module 1.2 Cell Membranes Notes & Questions Andy Todd 1 Outline the roles of membranes within cells and at the surface of cells. The main

More information

Absorption of Drugs. Transport of a drug from the GI tract

Absorption of Drugs. Transport of a drug from the GI tract Absorption of Drugs Absorption is the transfer of a drug from its site of administration to the bloodstream. The rate and efficiency of absorption depend on the route of administration. For IV delivery,

More information

Mammalian Physiology. Cellular Membranes Membrane Transport UNLV. PHYSIOLOGY, Chapter 1 Berne, Levy, Koeppen, Stanton UNIVERSITY OF NEVADA LAS VEGAS

Mammalian Physiology. Cellular Membranes Membrane Transport UNLV. PHYSIOLOGY, Chapter 1 Berne, Levy, Koeppen, Stanton UNIVERSITY OF NEVADA LAS VEGAS Mammalian Physiology Cellular Membranes Membrane Transport UNLV 1 UNIVERSITY OF NEVADA LAS VEGAS PHYSIOLOGY, Chapter 1 Berne, Levy, Koeppen, Stanton Objectives Describe the structure of the cell membrane

More information

4. Biology of the Cell

4. Biology of the Cell 4. Biology of the Cell Our primary focus in this chapter will be the plasma membrane and movement of materials across the plasma membrane. You should already be familiar with the basic structures and roles

More information

Human Anatomy & Physiology I with Dr. Hubley. Practice Exam 1

Human Anatomy & Physiology I with Dr. Hubley. Practice Exam 1 Human Anatomy & Physiology I with Dr. Hubley Practice Exam 1 1. Which definition is the best definition of the term gross anatomy? a. The study of cells. b. The study of tissues. c. The study of structures

More information

Vascular System The heart can be thought of 2 separate pumps from the right ventricle, blood is pumped at a low pressure to the lungs and then back

Vascular System The heart can be thought of 2 separate pumps from the right ventricle, blood is pumped at a low pressure to the lungs and then back Vascular System The heart can be thought of 2 separate pumps from the right ventricle, blood is pumped at a low pressure to the lungs and then back to the left atria from the left ventricle, blood is pumped

More information

CELL MEMBRANES, TRANSPORT, and COMMUNICATION. Teacher Packet

CELL MEMBRANES, TRANSPORT, and COMMUNICATION. Teacher Packet AP * BIOLOGY CELL MEMBRANES, TRANSPORT, and COMMUNICATION Teacher Packet AP* is a trademark of the College Entrance Examination Board. The College Entrance Examination Board was not involved in the production

More information

CHAPTER 5.1 5.2: Plasma Membrane Structure

CHAPTER 5.1 5.2: Plasma Membrane Structure CHAPTER 5.1 5.2: Plasma Membrane Structure 1. Describe the structure of a phospholipid molecule. Be sure to describe their behavior in relationship to water. 2. What happens when a collection of phospholipids

More information

The Lipid Bilayer Is a Two-Dimensional Fluid

The Lipid Bilayer Is a Two-Dimensional Fluid The Lipid Bilayer Is a Two-Dimensional Fluid The aqueous environment inside and outside a cell prevents membrane lipids from escaping from bilayer, but nothing stops these molecules from moving about and

More information

Six major functions of membrane proteins: Transport Enzymatic activity

Six major functions of membrane proteins: Transport Enzymatic activity CH 7 Membranes Cellular Membranes Phospholipids are the most abundant lipid in the plasma membrane. Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions. The fluid mosaic

More information

BSC 2010 - Exam I Lectures and Text Pages. The Plasma Membrane Structure and Function. Phospholipids. I. Intro to Biology (2-29) II.

BSC 2010 - Exam I Lectures and Text Pages. The Plasma Membrane Structure and Function. Phospholipids. I. Intro to Biology (2-29) II. BSC 2010 - Exam I Lectures and Text Pages I. Intro to Biology (2-29) II. Chemistry of Life Chemistry review (30-46) Water (47-57) Carbon (58-67) Macromolecules (68-91) III. Cells and Membranes Cell structure

More information

Biological cell membranes

Biological cell membranes Unit 14: Cell biology. 14 2 Biological cell membranes The cell surface membrane surrounds the cell and acts as a barrier between the cell s contents and the environment. The cell membrane has multiple

More information

BIOLOGICAL MEMBRANES: FUNCTIONS, STRUCTURES & TRANSPORT

BIOLOGICAL MEMBRANES: FUNCTIONS, STRUCTURES & TRANSPORT BIOLOGICAL MEMBRANES: FUNCTIONS, STRUCTURES & TRANSPORT UNIVERSITY OF PNG SCHOOL OF MEDICINE AND HEALTH SCIENCES DISCIPLINE OF BIOCHEMISTRY AND MOLECULAR BIOLOGY BMLS II / B Pharm II / BDS II VJ Temple

More information

FIGURE 2.18. A. The phosphate end of the molecule is polar (charged) and hydrophilic (attracted to water).

FIGURE 2.18. A. The phosphate end of the molecule is polar (charged) and hydrophilic (attracted to water). PLASMA MEMBRANE 1. The plasma membrane is the outermost part of a cell. 2. The main component of the plasma membrane is phospholipids. FIGURE 2.18 A. The phosphate end of the molecule is polar (charged)

More information

Cell Biology - Part 2 Membranes

Cell Biology - Part 2 Membranes Cell Biology - Part 2 Membranes The organization of cells is made possible by membranes. Membranes isolate, partition, and compartmentalize cells. 1 Membranes isolate the inside of the cell from the outside

More information

Membrane Structure and Function

Membrane Structure and Function Membrane Structure and Function -plasma membrane acts as a barrier between cells and the surrounding. -plasma membrane is selective permeable -consist of lipids, proteins and carbohydrates -major lipids

More information

Homeostasis and Transport Module A Anchor 4

Homeostasis and Transport Module A Anchor 4 Homeostasis and Transport Module A Anchor 4 Key Concepts: - Buffers play an important role in maintaining homeostasis in organisms. - To maintain homeostasis, unicellular organisms grow, respond to the

More information

Biological Membranes. Impermeable lipid bilayer membrane. Protein Channels and Pores

Biological Membranes. Impermeable lipid bilayer membrane. Protein Channels and Pores Biological Membranes Impermeable lipid bilayer membrane Protein Channels and Pores 1 Biological Membranes Are Barriers for Ions and Large Polar Molecules The Cell. A Molecular Approach. G.M. Cooper, R.E.

More information

PART I: Neurons and the Nerve Impulse

PART I: Neurons and the Nerve Impulse PART I: Neurons and the Nerve Impulse Identify each of the labeled structures of the neuron below. A. B. C. D. E. F. G. Identify each of the labeled structures of the neuron below. A. dendrites B. nucleus

More information

Mechanisms of Hormonal Action Bryant Miles

Mechanisms of Hormonal Action Bryant Miles Mechanisms of ormonal Action Bryant Miles Multicellular organisms need to coordinate metabolic activities. Complex signaling systems have evolved using chemicals called hormones to regulate cellular activities.

More information

Ch. 8 - The Cell Membrane

Ch. 8 - The Cell Membrane Ch. 8 - The Cell Membrane 2007-2008 Phospholipids Phosphate head hydrophilic Fatty acid tails hydrophobic Arranged as a bilayer Phosphate attracted to water Fatty acid repelled by water Aaaah, one of those

More information

3) There are different types of extracellular signaling molecules. 4) most signaling molecules are secreted by exocytosis

3) There are different types of extracellular signaling molecules. 4) most signaling molecules are secreted by exocytosis XIV) Signaling. A) The need for Signaling in multicellular organisms B) yeast need to signal to respond to various factors C) Extracellular signaling molecules bind to receptors 1) most bind to receptors

More information

Lecture 8. Protein Trafficking/Targeting. Protein targeting is necessary for proteins that are destined to work outside the cytoplasm.

Lecture 8. Protein Trafficking/Targeting. Protein targeting is necessary for proteins that are destined to work outside the cytoplasm. Protein Trafficking/Targeting (8.1) Lecture 8 Protein Trafficking/Targeting Protein targeting is necessary for proteins that are destined to work outside the cytoplasm. Protein targeting is more complex

More information

Actions of Hormones on Target Cells Page 1. Actions of Hormones on Target Cells Page 2. Goals/ What You Need to Know Goals What You Need to Know

Actions of Hormones on Target Cells Page 1. Actions of Hormones on Target Cells Page 2. Goals/ What You Need to Know Goals What You Need to Know Actions of Hormones on Target Cells Graphics are used with permission of: Pearson Education Inc., publishing as Benjamin Cummings (http://www.aw-bc.com) Page 1. Actions of Hormones on Target Cells Hormones

More information

Keystone Review Practice Test Module A Cells and Cell Processes. 1. Which characteristic is shared by all prokaryotes and eukaryotes?

Keystone Review Practice Test Module A Cells and Cell Processes. 1. Which characteristic is shared by all prokaryotes and eukaryotes? Keystone Review Practice Test Module A Cells and Cell Processes 1. Which characteristic is shared by all prokaryotes and eukaryotes? a. Ability to store hereditary information b. Use of organelles to control

More information

Hormones & Chemical Signaling

Hormones & Chemical Signaling Hormones & Chemical Signaling Part 2 modulation of signal pathways and hormone classification & function How are these pathways controlled? Receptors are proteins! Subject to Specificity of binding Competition

More information

Chapter-21b: Hormones and Receptors

Chapter-21b: Hormones and Receptors 1 hapter-21b: Hormones and Receptors Hormone classes Hormones are classified according to the distance over which they act. 1. Autocrine hormones --- act on the same cell that released them. Interleukin-2

More information

Modes of Membrane Transport

Modes of Membrane Transport Modes of Membrane Transport Transmembrane Transport movement of small substances through a cellular membrane (plasma, ER, mitochondrial..) ions, fatty acids, H 2 O, monosaccharides, steroids, amino acids

More information

Date: Student Name: Teacher Name: Jared George. Score: 1) A cell with 1% solute concentration is placed in a beaker with a 5% solute concentration.

Date: Student Name: Teacher Name: Jared George. Score: 1) A cell with 1% solute concentration is placed in a beaker with a 5% solute concentration. Biology Keystone (PA Core) Quiz Homeostasis and Transport - (BIO.A.4.1.1 ) Plasma Membrane, (BIO.A.4.1.2 ) Transport Mechanisms, (BIO.A.4.1.3 ) Transport Facilitation Student Name: Teacher Name: Jared

More information

RAD 223. Radiography physiology. Lecture Notes. First lecture: Cell and Tissue

RAD 223. Radiography physiology. Lecture Notes. First lecture: Cell and Tissue RAD 223 Radiography physiology Lecture Notes First lecture: Cell and Tissue Physiology: the word physiology derived from a Greek word for study of nature. It is the study of how the body and its part work

More information

Lecture 4 Cell Membranes & Organelles

Lecture 4 Cell Membranes & Organelles Lecture 4 Cell Membranes & Organelles Structure of Animal Cells The Phospholipid Structure Phospholipid structure Encases all living cells Its basic structure is represented by the fluidmosaic model Phospholipid

More information

Compartmentalization of the Cell. Objectives. Recommended Reading. Professor Alfred Cuschieri. Department of Anatomy University of Malta

Compartmentalization of the Cell. Objectives. Recommended Reading. Professor Alfred Cuschieri. Department of Anatomy University of Malta Compartmentalization of the Cell Professor Alfred Cuschieri Department of Anatomy University of Malta Objectives By the end of this session the student should be able to: 1. Identify the different organelles

More information

Chapter 8. Movement across the Cell Membrane. AP Biology

Chapter 8. Movement across the Cell Membrane. AP Biology Chapter 8. Movement across the Cell Membrane More than just a barrier Expanding our view of cell membrane beyond just a phospholipid bilayer barrier phospholipids plus Fluid Mosaic Model In 1972, S.J.

More information

Diabetes and Insulin Signaling

Diabetes and Insulin Signaling Diabetes and Insulin Signaling NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE by Kristy J. Wilson School of Mathematics and Sciences Marian University, Indianapolis, IN Part I Research Orientation

More information

Lecture 6: Cholesterol (Ch. 9.1e, 9.2b, 19.7b,c) & Lipoproteins (Ch. 10.3*, 19.1, 19.7b,c)

Lecture 6: Cholesterol (Ch. 9.1e, 9.2b, 19.7b,c) & Lipoproteins (Ch. 10.3*, 19.1, 19.7b,c) Lecture 6: Cholesterol (Ch. 9.1e, 9.2b, 19.7b,c) & Lipoproteins (Ch. 10.3*, 19.1, 19.7b,c) Next lecture: Fatty Acid Oxidation (Ch. 19.2), Ketone Bodies (Ch. 19.3) and Fatty Acid Biosynthesis (Ch. 19.4)

More information

Cell Biology Questions and Learning Objectives

Cell Biology Questions and Learning Objectives Cell Biology Questions and Learning Objectives (with hypothetical learning materials that might populate the objective) The topics and central questions listed here are typical for an introductory undergraduate

More information

An Overview of Cells and Cell Research

An Overview of Cells and Cell Research An Overview of Cells and Cell Research 1 An Overview of Cells and Cell Research Chapter Outline Model Species and Cell types Cell components Tools of Cell Biology Model Species E. Coli: simplest organism

More information

The Cell: Organelle Diagrams

The Cell: Organelle Diagrams The Cell: Organelle Diagrams Fig 7-4. A prokaryotic cell. Lacking a true nucleus and the other membrane-enclosed organelles of the eukaryotic cell, the prokaryotic cell is much simpler in structure. Only

More information

Lymph capillaries, Lymphatic collecting vessels, Valves, Lymph Duct, Lymph node, Vein

Lymph capillaries, Lymphatic collecting vessels, Valves, Lymph Duct, Lymph node, Vein WLHS/A&P/Oppelt Name Lymphatic System Practice 1. Figure 12-1 provides an overview of the lymphatic vessels. First color code the following structures. Color code in Figure 12-1 Heart Veins Lymphatic vessels/lymph

More information

10. T and B cells are types of a. endocrine cells. c. lymphocytes. b. platelets. d. complement cells.

10. T and B cells are types of a. endocrine cells. c. lymphocytes. b. platelets. d. complement cells. Virus and Immune System Review Directions: Write your answers on a separate piece of paper. 1. Why does a cut in the skin threaten the body s nonspecific defenses against disease? a. If a cut bleeds, disease-fighting

More information

April 18, 2008 Dr. Alan H. Stephenson Pharmacological and Physiological Science

April 18, 2008 Dr. Alan H. Stephenson Pharmacological and Physiological Science Renal Mechanisms for Regulating Urine Concentration April 18, 2008 Dr. Alan H. Stephenson Pharmacological and Physiological Science Amount Filtered Reabsorption is selective Examples of substances that

More information

IB104 - Lecture 9 - Membranes

IB104 - Lecture 9 - Membranes There have been many magnificent boats built to try to reach 50 knots. This was the creation of an Australian team that held the record for more than a decade, from 1993 till 2005, at 46.5 knots with their

More information

Your Life Your Health Cariodmetabolic Risk Syndrome Part VII Inflammation chronic, low-grade By James L. Holly, MD The Examiner January 25, 2007

Your Life Your Health Cariodmetabolic Risk Syndrome Part VII Inflammation chronic, low-grade By James L. Holly, MD The Examiner January 25, 2007 Your Life Your Health Cariodmetabolic Risk Syndrome Part VII Inflammation chronic, low-grade By James L. Holly, MD The Examiner January 25, 2007 The cardiometabolic risk syndrome is increasingly recognized

More information

Cell Membrane Structure (and How to Get Through One)

Cell Membrane Structure (and How to Get Through One) Cell Membrane Structure (and How to Get Through One) A cell s membrane is a wall of sorts that defines the boundaries of a cell. The membrane provides protection and structure for the cell and acts as

More information

2006 7.012 Problem Set 6 KEY

2006 7.012 Problem Set 6 KEY 2006 7.012 Problem Set 6 KEY ** Due before 5 PM on WEDNESDAY, November 22, 2006. ** Turn answers in to the box outside of 68-120. PLEASE WRITE YOUR ANSWERS ON THIS PRINTOUT. 1. You create an artificial

More information

Inflammation and Healing. Review of Normal Defenses. Review of Normal Capillary Exchange. BIO 375 Pathophysiology

Inflammation and Healing. Review of Normal Defenses. Review of Normal Capillary Exchange. BIO 375 Pathophysiology Inflammation and Healing BIO 375 Pathophysiology Review of Normal Defenses Review of Normal Capillary Exchange 1 Inflammation Inflammation is a biochemical and cellular process that occurs in vascularized

More information

Review of the Cell and Its Organelles

Review of the Cell and Its Organelles Biology Learning Centre Review of the Cell and Its Organelles Tips for most effective learning of this material: Memorize the names and structures over several days. This will help you retain what you

More information

Membrane Transport. Extracellular Concentration of X

Membrane Transport. Extracellular Concentration of X Use the following graph to answer questions 1 and 2. Rate of diffusion of X into the cell 1. Which of the following processes is represented by the above graph? c. Active transport 2. Molecule X is most

More information

Membrane Structure and Function

Membrane Structure and Function Membrane Structure and Function Part A Multiple Choice 1. The fluid mosaic model describes membranes as having A. a set of protein channels separated by phospholipids. B. a bilayer of phospholipids in

More information

Platelet Review July 2012. Thomas S. Kickler M.D. Johns Hopkins University School of Medicine

Platelet Review July 2012. Thomas S. Kickler M.D. Johns Hopkins University School of Medicine Platelet Review July 2012 Thomas S. Kickler M.D. Johns Hopkins University School of Medicine Hemostasis Hemostasis is the process that leads to the stopping of bleeding Hemostasis involves blood vessels,

More information

2007 7.013 Problem Set 1 KEY

2007 7.013 Problem Set 1 KEY 2007 7.013 Problem Set 1 KEY Due before 5 PM on FRIDAY, February 16, 2007. Turn answers in to the box outside of 68-120. PLEASE WRITE YOUR ANSWERS ON THIS PRINTOUT. 1. Where in a eukaryotic cell do you

More information

Plasma Membrane hydrophilic polar heads

Plasma Membrane hydrophilic polar heads The Parts of the Cell 3 main parts in ALL cells: plasma membrane, cytoplasm, genetic material this is about the parts of a generic eukaryotic cell Plasma Membrane -is a fluid mosaic model membrane is fluid

More information

The diagram below summarizes the effects of the compounds that cells use to regulate their own metabolism.

The diagram below summarizes the effects of the compounds that cells use to regulate their own metabolism. Regulation of carbohydrate metabolism Intracellular metabolic regulators Each of the control point steps in the carbohydrate metabolic pathways in effect regulates itself by responding to molecules that

More information

Unit 2: Cells, Membranes and Signaling CELL MEMBRANE. Chapter 5 Hillis Textbook

Unit 2: Cells, Membranes and Signaling CELL MEMBRANE. Chapter 5 Hillis Textbook Unit 2: Cells, Membranes and Signaling CELL MEMBRANE Chapter 5 Hillis Textbook HOW DOES THE LAB RELATE TO THE NEXT CHAPTER? SURFACE AREA: the entire outer covering of a cell that enables materials pass.

More information

Section 7-3 Cell Boundaries

Section 7-3 Cell Boundaries Note: For the past several years, I ve been puzzling how to integrate new discoveries on the nature of water movement through cell membranes into Chapter 7. The Section below is a draft of my first efforts

More information

Chapter 3. Cellular Structure and Function Worksheets. 39 www.ck12.org

Chapter 3. Cellular Structure and Function Worksheets. 39 www.ck12.org Chapter 3 Cellular Structure and Function Worksheets (Opening image copyright by Sebastian Kaulitzki, 2010. Used under license from Shutterstock.com.) Lesson 3.1: Introduction to Cells Lesson 3.2: Cell

More information

O ρόλος της ακετυλοχολίνης στη σύσπαση και τον πολλαπλασιασµό των ΛΜΚ (του αναπνευστικού) Απ. Χατζηευθυµίου 2015

O ρόλος της ακετυλοχολίνης στη σύσπαση και τον πολλαπλασιασµό των ΛΜΚ (του αναπνευστικού) Απ. Χατζηευθυµίου 2015 O ρόλος της ακετυλοχολίνης στη σύσπαση και τον πολλαπλασιασµό των ΛΜΚ (του αναπνευστικού) Απ. Χατζηευθυµίου 2015 Σύσπαση ΛΜΙ An increase in free intracellular calcium can result from either increased flux

More information

Todays Outline. Metabolism. Why do cells need energy? How do cells acquire energy? Metabolism. Concepts & Processes. The cells capacity to:

Todays Outline. Metabolism. Why do cells need energy? How do cells acquire energy? Metabolism. Concepts & Processes. The cells capacity to: and Work Metabolic Pathways Enzymes Features Factors Affecting Enzyme Activity Membrane Transport Diffusion Osmosis Passive Transport Active Transport Bulk Transport Todays Outline -Releasing Pathways

More information

Anatomy and Physiology Placement Exam 2 Practice with Answers at End!

Anatomy and Physiology Placement Exam 2 Practice with Answers at End! Anatomy and Physiology Placement Exam 2 Practice with Answers at End! General Chemical Principles 1. bonds are characterized by the sharing of electrons between the participating atoms. a. hydrogen b.

More information

Microscopes. Eukaryotes Eukaryotic cells are characterized by having: DNA in a nucleus that is bounded by a membranous nuclear envelope

Microscopes. Eukaryotes Eukaryotic cells are characterized by having: DNA in a nucleus that is bounded by a membranous nuclear envelope CH 6 The Cell Microscopy Scientists use microscopes to visualize cells too small to see with the naked eye. In a light microscope (LM), visible light is passed through a specimen and then through glass

More information

Milwaukee School of Engineering Gerrits@msoe.edu. Case Study: Factors that Affect Blood Pressure Instructor Version

Milwaukee School of Engineering Gerrits@msoe.edu. Case Study: Factors that Affect Blood Pressure Instructor Version Case Study: Factors that Affect Blood Pressure Instructor Version Goal This activity (case study and its associated questions) is designed to be a student-centered learning activity relating to the factors

More information

Muscles How muscles contract - The Sliding Filament Theory

Muscles How muscles contract - The Sliding Filament Theory Muscles How muscles contract - The Sliding Filament Theory A muscle contains many muscle fibers A muscle fiber is a series of fused cells Each fiber contains a bundle of 4-20 myofibrils Myofibrils are

More information

Student name ID # 2. (4 pts) What is the terminal electron acceptor in respiration? In photosynthesis? O2, NADP+

Student name ID # 2. (4 pts) What is the terminal electron acceptor in respiration? In photosynthesis? O2, NADP+ 1. Membrane transport. A. (4 pts) What ion couples primary and secondary active transport in animal cells? What ion serves the same function in plant cells? Na+, H+ 2. (4 pts) What is the terminal electron

More information

Copyright 2000-2003 Mark Brandt, Ph.D. 54

Copyright 2000-2003 Mark Brandt, Ph.D. 54 Pyruvate Oxidation Overview of pyruvate metabolism Pyruvate can be produced in a variety of ways. It is an end product of glycolysis, and can be derived from lactate taken up from the environment (or,

More information

Viruses. Viral components: Capsid. Chapter 10: Viruses. Viral components: Nucleic Acid. Viral components: Envelope

Viruses. Viral components: Capsid. Chapter 10: Viruses. Viral components: Nucleic Acid. Viral components: Envelope Viruses Chapter 10: Viruses Lecture Exam #3 Wednesday, November 22 nd (This lecture WILL be on Exam #3) Dr. Amy Rogers Office Hours: MW 9-10 AM Too small to see with a light microscope Visible with electron

More information

Resting membrane potential ~ -70mV - Membrane is polarized

Resting membrane potential ~ -70mV - Membrane is polarized Resting membrane potential ~ -70mV - Membrane is polarized (ie) Electrical charge on the outside of the membrane is positive while the electrical charge on the inside of the membrane is negative Changes

More information

http://faculty.sau.edu.sa/h.alshehri

http://faculty.sau.edu.sa/h.alshehri http://faculty.sau.edu.sa/h.alshehri Definition: Proteins are macromolecules with a backbone formed by polymerization of amino acids. Proteins carry out a number of functions in living organisms: - They

More information

CHAPTER 1: THE LUNGS AND RESPIRATORY SYSTEM

CHAPTER 1: THE LUNGS AND RESPIRATORY SYSTEM CHAPTER 1: THE LUNGS AND RESPIRATORY SYSTEM INTRODUCTION Lung cancer affects a life-sustaining system of the body, the respiratory system. The respiratory system is responsible for one of the essential

More information

7 Answers to end-of-chapter questions

7 Answers to end-of-chapter questions 7 Answers to end-of-chapter questions Multiple choice questions 1 B 2 B 3 A 4 B 5 A 6 D 7 C 8 C 9 B 10 B Structured questions 11 a i Maintenance of a constant internal environment within set limits i Concentration

More information

Questions on The Nervous System and Gas Exchange

Questions on The Nervous System and Gas Exchange Name: Questions on The Nervous System and Gas Exchange Directions: The following questions are taken from previous IB Final Papers on Topics 6.4 (Gas Exchange) and 6.5 (Nerves, hormones and homeostasis).

More information

Chapter 8. Summary and Perspectives

Chapter 8. Summary and Perspectives Chapter 8 Summary and Perspectives 131 Chapter 8 Summary Overexpression of the multidrug resistance protein MRP1 confer multidrug resistance (MDR) to cancer cells. The contents of this thesis describe

More information

Chapter 18: Applications of Immunology

Chapter 18: Applications of Immunology Chapter 18: Applications of Immunology 1. Vaccinations 2. Monoclonal vs Polyclonal Ab 3. Diagnostic Immunology 1. Vaccinations What is Vaccination? A method of inducing artificial immunity by exposing

More information

Chapter 7: Membrane Structure and Function

Chapter 7: Membrane Structure and Function Name Period Concept 7.1 Cellular membranes are fluid mosaics of lipids and proteins 1. The large molecules of all living things fall into just four main classes. Name them. 2. Explain what is meant when

More information

The immune response Antibodies Antigens Epitopes (antigenic determinants) the part of a protein antigen recognized by an antibody Haptens small

The immune response Antibodies Antigens Epitopes (antigenic determinants) the part of a protein antigen recognized by an antibody Haptens small The immune response Antibodies Antigens Epitopes (antigenic determinants) the part of a protein antigen recognized by an antibody Haptens small molecules that can elicit an immune response when linked

More information

Muscle Tissue. Muscle Physiology. Skeletal Muscle. Types of Muscle. Skeletal Muscle Organization. Myofibril Structure

Muscle Tissue. Muscle Physiology. Skeletal Muscle. Types of Muscle. Skeletal Muscle Organization. Myofibril Structure Muscle Tissue Muscle Physiology Chapter 12 Specially designed to contract Generates mechanical force Functions locomotion and external movements internal movement (circulation, digestion) heat generation

More information

BME 42-620 Engineering Molecular Cell Biology. Lecture 02: Structural and Functional Organization of

BME 42-620 Engineering Molecular Cell Biology. Lecture 02: Structural and Functional Organization of BME 42-620 Engineering Molecular Cell Biology Lecture 02: Structural and Functional Organization of Eukaryotic Cells BME42-620 Lecture 02, September 01, 2011 1 Outline A brief review of the previous lecture

More information

2161-1 - Page 1. Name: 1) Choose the disease that is most closely related to the given phrase. Questions 10 and 11 refer to the following:

2161-1 - Page 1. Name: 1) Choose the disease that is most closely related to the given phrase. Questions 10 and 11 refer to the following: Name: 2161-1 - Page 1 1) Choose the disease that is most closely related to the given phrase. a disease of the bone marrow characterized by uncontrolled production of white blood cells A) meningitis B)

More information

NO CALCULATORS OR CELL PHONES ALLOWED

NO CALCULATORS OR CELL PHONES ALLOWED Biol 205 Exam 1 TEST FORM A Spring 2008 NAME Fill out both sides of the Scantron Sheet. On Side 2 be sure to indicate that you have TEST FORM A The answers to Part I should be placed on the SCANTRON SHEET.

More information

Animal Tissues. I. Epithelial Tissue

Animal Tissues. I. Epithelial Tissue Animal Tissues There are four types of tissues found in animals: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. In this lab you will learn the major characteristics of each tissue

More information

7. A selectively permeable membrane only allows certain molecules to pass through.

7. A selectively permeable membrane only allows certain molecules to pass through. CHAPTER 2 GETTING IN & OUT OF CELLS PASSIVE TRANSPORT Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells. Some substances can cross the cell membrane

More information

F fusion of Cytosolic Droplets and Insulin Resistance to Lung Cancer

F fusion of Cytosolic Droplets and Insulin Resistance to Lung Cancer Cytosolic lipid droplets: link to the development of insulin resistance and increased production of VLDL1 Sven-Olof Olofsson, MD, PhD Insulin resistance is an important risk factor for the development

More information

Electron Transport Generates a Proton Gradient Across the Membrane

Electron Transport Generates a Proton Gradient Across the Membrane Electron Transport Generates a Proton Gradient Across the Membrane Each of respiratory enzyme complexes couples the energy released by electron transfer across it to an uptake of protons from water in

More information

Pulmonary interstitium. Interstitial Lung Disease. Interstitial lung disease. Interstitial lung disease. Causes.

Pulmonary interstitium. Interstitial Lung Disease. Interstitial lung disease. Interstitial lung disease. Causes. Pulmonary interstitium Interstitial Lung Disease Alveolar lining cells (types 1 and 2) Thin elastin-rich connective component containing capillary blood vessels Interstitial lung disease Increase in interstitial

More information

Smooth Muscle. Learning Objectives.

Smooth Muscle. Learning Objectives. Smooth Muscle. Learning Objectives. At the end of this course, you should be able to : 1. describe the structure of smooth muscle 2. describe where smooth muscle occurs within the body 3. discuss the structural

More information

The Immune System. 2 Types of Defense Mechanisms. Lines of Defense. Line of Defense. Lines of Defense

The Immune System. 2 Types of Defense Mechanisms. Lines of Defense. Line of Defense. Lines of Defense The Immune System 2 Types of Defense Mechanisms Immune System the system that fights infection by producing cells to inactivate foreign substances to avoid infection and disease. Immunity the body s ability

More information

ANIMALS FORM & FUNCTION BODY DEFENSES NONSPECIFIC DEFENSES PHYSICAL BARRIERS PHAGOCYTES. Animals Form & Function Activity #4 page 1

ANIMALS FORM & FUNCTION BODY DEFENSES NONSPECIFIC DEFENSES PHYSICAL BARRIERS PHAGOCYTES. Animals Form & Function Activity #4 page 1 AP BIOLOGY ANIMALS FORM & FUNCTION ACTIVITY #4 NAME DATE HOUR BODY DEFENSES NONSPECIFIC DEFENSES PHYSICAL BARRIERS PHAGOCYTES Animals Form & Function Activity #4 page 1 INFLAMMATORY RESPONSE ANTIMICROBIAL

More information

Anaerobic and Aerobic Training Adaptations. Chapters 5 & 6

Anaerobic and Aerobic Training Adaptations. Chapters 5 & 6 Anaerobic and Aerobic Training Adaptations Chapters 5 & 6 Adaptations to Training Chronic exercise provides stimulus for the systems of the body to change Systems will adapt according to level, intensity,

More information

Psychology 3625 Cellular and Molecular Neuroscience. Dr Darren Hannesson

Psychology 3625 Cellular and Molecular Neuroscience. Dr Darren Hannesson Psychology 3625 Cellular and Molecular Neuroscience Dr Darren Hannesson Lecture 6 Cells of the nervous system Neurons Glia Other cell types Blood-brain barrier Types of nervous system cells Neurons The

More information

B Cell Generation, Activation & Differentiation. B cell maturation

B Cell Generation, Activation & Differentiation. B cell maturation B Cell Generation, Activation & Differentiation Naïve B cells- have not encountered Ag. Have IgM and IgD on cell surface : have same binding VDJ regions but different constant region leaves bone marrow

More information

Cells and Their Housekeeping Functions Cell Membrane & Membrane Potential

Cells and Their Housekeeping Functions Cell Membrane & Membrane Potential Cells and Their Housekeeping Functions Cell Membrane & Membrane Potential Shu-Ping Lin, Ph.D. Institute of Biomedical Engineering E-mail: splin@dragon.nchu.edu.tw Website: http://web.nchu.edu.tw/pweb/users/splin/

More information

serum protein and A/ G ratio

serum protein and A/ G ratio serum protein and A/ G ratio Blood plasma contains at least 125 individual proteins. Serum ( as contrasted with plasma) is deficient in those coagulation protein which are consumed during the process of

More information

Intracellular Calcium and Phosphatidylserine Exposure in the red Blood Cells

Intracellular Calcium and Phosphatidylserine Exposure in the red Blood Cells Intracellular Calcium and Phosphatidylserine Exposure in the red Blood Cells Biotechnology Seminar 2 Yaser Alkhaled 30.10.13 Table of Content 1. Introduction.... 3 2. Membrane of red blood cell.... 4 3.

More information

UNIT 3 : MAINTAINING DYNAMIC EQUILIBRIUM

UNIT 3 : MAINTAINING DYNAMIC EQUILIBRIUM BIOLOGY - 2201 UNIT 3 : MAINTAINING DYNAMIC EQUILIBRIUM What happens to your body as you run? Breathing, heart rate, temperature, muscle pain, thirsty... Homeotasis Homeostasis is the process of maintaining

More information

Given these characteristics of life, which of the following objects is considered a living organism? W. X. Y. Z.

Given these characteristics of life, which of the following objects is considered a living organism? W. X. Y. Z. Cell Structure and Organization 1. All living things must possess certain characteristics. They are all composed of one or more cells. They can grow, reproduce, and pass their genes on to their offspring.

More information

Histology. Epithelial Tissue

Histology. Epithelial Tissue Histology Epithelial Tissue Epithelial Tissue Lines internal and external body surfaces Forms glands Epithelial Tissue Little extracellular matrix Attached on one side Avascular Basement membrane Apical

More information

4. Which carbohydrate would you find as part of a molecule of RNA? a. Galactose b. Deoxyribose c. Ribose d. Glucose

4. Which carbohydrate would you find as part of a molecule of RNA? a. Galactose b. Deoxyribose c. Ribose d. Glucose 1. How is a polymer formed from multiple monomers? a. From the growth of the chain of carbon atoms b. By the removal of an OH group and a hydrogen atom c. By the addition of an OH group and a hydrogen

More information

Muscular dystrophy: basic facts

Muscular dystrophy: basic facts Muscular dystrophy: basic facts - heterogenous group of inherited disorders characterized by progressive muscle weakness and wasting (regeneration of muscle tissue fails) - most apparent or symptomatic

More information

The Immune System: A Tutorial

The Immune System: A Tutorial The Immune System: A Tutorial Modeling and Simulation of Biological Systems 21-366B Shlomo Ta asan Images taken from http://rex.nci.nih.gov/behindthenews/uis/uisframe.htm http://copewithcytokines.de/ The

More information

Endocrine Responses to Resistance Exercise

Endocrine Responses to Resistance Exercise chapter 3 Endocrine Responses to Resistance Exercise Chapter Objectives Understand basic concepts of endocrinology. Explain the physiological roles of anabolic hormones. Describe hormonal responses to

More information

The Cell Interior and Function

The Cell Interior and Function The Cell Interior and Function 5 5.0 CHAPTER PREVIEW Investigate and understand the organization and function of the cell interior. Define the differences between eukaryotic and prokaryotic cell structure.

More information