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Cell-cell adhesion

Cell-cell adhesion. Cell adhesion molecules (CAMs) Lots of them Involved in many cellular processes Cadherins Adhesive glycoproteins. Cell juctions. Adhesive junctions Strong links Tight junctions Prevent leaks between cells Gap junctions Forms direct link between cells.

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Cell-cell adhesion

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  1. Cell-cell adhesion • Cell adhesion molecules (CAMs) • Lots of them • Involved in many cellular processes • Cadherins • Adhesive glycoproteins

  2. Cell juctions • Adhesive junctions • Strong links • Tight junctions • Prevent leaks between cells • Gap junctions • Forms direct link between cells

  3. Adhesive junctions • Desmosomes • Hemidesmosomes • Adherens junctions • Focal adhesions All contain - intracellular attachment proteins—link to cytoskeleton - transmembrane linker proteins—link the cells

  4. Desmosomes—rivets between cells

  5. Adherens junctions • Belt around cell • Connects to actin, not tonofilaments • Look a lot like desmosomes • Found in • Heart • Epithelial layers • Oftern form belt • Called “focal adhesion” if connects to ECM

  6. Tight junctions

  7. Gap junctions • Direct electrical connection • Formed by connexons • Protein=connexin • Prominent in muscle and nerve—e.g. electrical tissues • Form of cell-cell communication

  8. Cell walls

  9. Plant cell walls • Cellulose (40%) • Branched polysaccharides • Hemicellulose (20%) • Pectins (30%) • Extensins--glycoproteins (10%) • Lignins—woody tissues • Insoluble aromatic alcohols • Cross-link to form wood

  10. Plasmodesmata

  11. Signal Transduction

  12. General Scheme of Cell Signalling

  13. Types of Receptors • G-protein linked receptors • cAMP • Ca2+ • Inositol triphosphate • Diacylglycerol • Protein-kinase receptors • Serine/threonine kinases • Tyrosine kinase

  14. G Protein linked receptors

  15. G proteins • Large heteromeric G proteins • Alpha—binds GTP/GDP • Beta • Gamma • Together they control the alpha subunit • Small monomeric G proteins • Generally called by another name • Example: ras

  16. Adenylate cyclase • Activated by G proteins • Makes cAMP • cAMP activates cAMP dependent protein kinase • aka protein kinase A (PKA)

  17. Pg 261

  18. Diseases • Cholera • Vibrio cholerae • Toxin modifies a G protein • Continually activates adenylate cyclase • Whooping cough • Bordetella pertussis • Pertussis toxin • Inactivates a G protein that inhibits adenylate cyclase

  19. Inositol triphosphate and diacylglycerol second messengers

  20. Protein Kinase-associated Receptors

  21. Tyrosine kinase receptors • Activated by ligand binding • Often growth factors • Form dimers • Autophosphorylation • On tyrosines • SH2 domain • Src homology (domain) 2 region • Bind to phosphorylated tyrosines • Activate various second messengers

  22. Serine/threonine kinases • Two different subunits • Direct phosphorylation of transcription regulators

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