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Tight Junctions Occluding junctions

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Presentation on theme: "Tight Junctions Occluding junctions"— Presentation transcript:

1 Tight Junctions Occluding junctions
Sealing strands are rows of transmembrane proteins

2 Transcellular Transport
Essential for segregating transport proteins

3 Anchoring Junctions Attach cytoskeleton to neighboring cell or to extracellular matrix Intracellular anchor proteins Transmembrane adhesion proteins

4 Adherens Junctions Connect actin filaments in neighboring cells
Cadherin transmembrane adhesion proteins Catenin anchor proteins

5 Desmosomes Connect intermediate filaments in neighboring cells
Cadherin transmembrane adhesion proteins Complex of anchoring proteins Pemphigus autoimmune disease

6 Focal Adhesions Connect actin filaments to extracellular matrix
Integrin transmembrane adhesion proteins Various anchor proteins

7 Hemidesmosomes Connect intermediate filaments to basal lamina
Integrin transmembrane adhesion proteins Plectin anchor protein

8 Types Of Anchoring Junctions
Junction Transmembrane Extracellular Cytoskeletal Intracellular Adhesion Protein Attachment Attachment Anchor Protein Cell-Cell Adherens cadherins cadherin actin filaments catenins Junction (E-cadherin) (a- and b-) Desmosome cadherins cadherin intermediate catenins, (desmoglein, desmocollin) filaments desmoplakin Cell-Matirx Focal integrins extracellular actin filaments talin, vinculin, adhesion matrix proteins others Hemi- integrin a6b4 extracellular intermediate plectin desmosome matrix proteins filaments

9 Gap Junctions Communicating junctions
Channels composed of connexin transmembrane proteins

10 Junctional Complex Same relative positions of three junctions in most epithelium

11 Glycosaminoglycans Unbranched polysaccharide chain with repeating disaccharide unit Large volume, high negative charge result in gel-like form

12 Hyaluronan Simple GAG Not usually linked to protein

13 Proteoglycans Most GAGs covalently attached to protein
Synthesized in Golgi apparatus Link tetrasaccharide added to serine; other sugars added one at a time

14 Diversity Of Proteoglycans
Extensive variation in types and number of GAG chains

15 Collagens Triple helix from three collagen a chains
Rich in proline and glycine Proline- ring, stabilizes helix Glycine- small, tight chain packing Multiple a chains associate in different combinations

16 Synthesis of Collagens
Synthesized as pro-a-chain precursors Cleavage of pro-peptides following secretion Self-assembly into fibrils and aggregation into fibers


18 Hydroxylation In Collagen
Certain lysine and proline residues Form interchain hyrodrogen bonds Requires vitamin C; deficiency results in easy bruising, petechiae, scurvy

19 Cross-Linking Of Collagen
Occurs between lysine residues of separate molecules to strengthen fibrils

20 Genetic Diseases Affecting Collagen
Affected Disease Collagen Mutant Phenotype Osteogenesis imperfecta I weak bones, fractures Chondrodysplasias II cartilage deficiency Ehlers-Danlos syndrome III fragile skin & blood vessels, loose joints

21 Elastin Elastin molecules are cross-linked
Molecules in network expand and contract

22 Fibronectin Multiple binding sites for extracellular matrix and cell surface molecules

23 Laminin Component of basal lamina
Composed of a, b, and g chains that form distinct isoforms

24 Basal Lamina Sheet-like networks of laminin and type IV collagen

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