Epithelial Cells. Skin Lung Alveoli & Bronchi Kidney Tubules Intestinal Villi Bladder Glandular Ducts

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1 Epithelial Cells Skin Lung Alveoli & Bronchi Kidney Tubules Intestinal Villi Bladder Glandular Ducts

2 Types of Epithelium Basal lamina Simple Squamous/ Cuboidal cells wider than they are tall line body cavities e.g. peritoneum, hepatocytes Basal lamina Columnar cells taller than they are wide mucus seceting line the intestinal tract, kideny tubules, ducts of glands Basal lamina Stratified a) transitional - usually associated with cavities subject to expansion and contaction e.g. bladder b) stratified squamous - subject to frequent renewal e.g. skin

3 Epithelial Cell Characteristics Apical Membrane Regulation of nutrient & water uptake Regulated secretion Protection TJ Apical membrane Glycosyl-phosphatidylinositol linked (PI) proteins Na + -dependent transporters Hydrolases Cl-channels H + -ATPase Lateral Membrane Cell contact Cell communication Baso-Lateral Membrane Signal reception & transduction Generation of ionic gradients Constitutive secretion Basal Membrane Cell-matrix interactions AJ D HD GJ Basement membrane Lateral membrane Cell adhesion molecules Tight Junctions (TJ) Adherens Junction (AJ) Desmosomes (D) Gap Junctions (GJ) Baso-Lateral membrane Anion transporters Na+K+-ATPase Growth factor receptors Hormone & neurotransmitter receptors Basal membrane Hemidesmosomes (HD) Basement membrane receptors

4 Cell Junctions * * *

5 Tight Junctions seal apical surfaces from lateral and basal surfaces

6 Tight Junction Molecules

7 Desmosomes Important for strength and flexibilty E-cadherin α,β,γ catenins

8 Cadherins

9 Hemidesmosome Anchoring to the basement membrane Laminin 5 Basement membrane

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11 Salivary Gland Kidney Branching Morphogenesis Mesenchymal- Epithelial Transistion

12 Branching Morphogenesis mesenchyme determines epithelial differentiation

13 Kidney Organ Culture

14 Advantages of the Kidney Organ Culture Model Inducer and responder tissues remain separate until late stages of development Isolation of metanephric mesenchyme and in vitro growth is possible Development occurs slowly, allowing characterization of all stages Polarization of epithelial cells can be studied, a characteristic shared by all epithelial cell regardless of mode of development

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16 distal tubule podocytes proximal tubule bowmans capsule

17 +/- Antibodies Differential expression of genes expressed in uninduced and induced mesenchyme Effect on tubule formation

18 Stages in Epithelial Development in the Kidney and Important Factors Loose mesenchyme Condensate Comma-shaped body S-shaped tubule Induction/Proliferation Polarization Extracellular Matrix Cell-Matrix Receptors Cell-Cell Adhesion Transcription Factors Growth Factors collagen I/III fibronectin/ tenascin-c laminin α1 laminin α5 integrin α6 dystroglycan NCAM syndecan-1 E-cadherin Pax2 WT1 WNT4 BMP4 FGF7 ureter loose condensate polarisation Tubule mesenchyme (comma-shaped body) (S-shaped tubule) / (++)

19 Laminin α1/ integrin α6β1, α-dystroglycan condensation and polarisation Uvomorolin/ E-cadherin condensation WNT4 WT1 Pax2 BMP4 FGF7 required for condensation and epithelial cell formation inhibits apoptosis of metanephric mesenchyme/ proliferation maintains podocytes early ureteric bud formation and branching inhibits ureteric bud branching induces ureteric bud branching

20 Laminin Family

21 KEY: nidogen perlecan laminin type IV collagen

22 Pan-Laminin Laminin α1 Laminin α5

23 Comma shaped bodies ureter condensate ureter Laminin α1 S-shaped tubule

24 Pan Laminin Laminin α1

25 Protease Fragments of Laminin 1 E1-x P1 E3 E8 E = elastase P = pepsin T = trypsin C = cathepsin G

26 Antibodies to laminin α1 (E8) inhibit epithelial cell development no polarization

27 E3 Data

28 α6β1

29 α dys α dys α dys Integrin α6 Lam α1 α dys α dys + Integrin α6

30 α6β1 Laminin 1 G1-3 Laminin 1 G4-5

31 Laminin 1 α1 α6β1 G1-3 G4-5 α-dystroglycan

32 Angiogenesis -ingrowth of blood vessels

33 distal tubule podocytes proximal tubule bowmans capsule

34 Podocytes produce laminin α5 which is deposited in the glomerular basement membrane Substrate for endothelial cell ingrowth

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36 Laminin α5 knockout mouse α5 Podocytes proliferate No glomerular basement membrane formation Overexpression of transgene for a chimeric laminin α5 cannot rescue the phenotype

37 Role of Laminins in Differentiation Kidney salivary gland, lung organ cultures Pan LM LM α1 control + anti-e8 24h Pan LM LM α1 36h 72h 72h Laminin α1 appears around forming epithelia Antibodies to laminin α1 (E8) inhibit epithelial cell development no polarization Refs: Ekblom et al., 1980 PNAS USA 77, 485; Klein et al., Cell 55, 331

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39 Models for Investigating Protein Targeting MDCK cell line = madin-darby canine kidney epithelial cell line Viral Model - polarized viral budding occurs in different viruses and various cell types e.g. Influenza virus buds APICALLY in all epithelia Vesicular stomatitis virus (VSV) buds BASO-LATERALLY in all epithelia - viral proteins are produced times in excess over endogenous plasma proteins 20 C incubation (accumulation of viral poteins in trans-golgi) nitrocellulose 37 C incubation MDCK + Influenza-haemaglutini (HA) + VSV Vesicles released into medium IP with anti-viral tails Differential sedimentation Analysis of HA & VSV containing vesicles Proteins common to HA & VSV vesicles are involved in vesicle budding Proteins specific for HA or VSV vesicles are involved in apical or baso-lateral targeting