Cell Adhesion

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Cell Adhesion
2010-04-27 00:46:52
Cell Adhesion

Cell Adhesion
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  1. Cadherins
    Ca2+ dependent, dimer repeats, homophilic

    E-Cadherin - epithelial sheets - mediates cell-cell adhesion
  2. Ig-superfamily (CAMs)
    single pass homophilic cell-cell adhesions (sometimes heterophilic) Ca2+ independent
  3. Integrins
    • ca2+ independent
    • heterophilic interaction
    • heterodimers
    • Substrates in the ECM: collagen, laminin, fibronectin, proteoglycan
    • beta subunit contains cysteine rich domains
    • alpha subunit contains disulfied bonds
    • fibronectin + integrin: important for development
    • the COOH terminus in cytosol is usually actin binding (except in hemidesmosomes)
  4. Selectins
    • mediate leukeocyte endothelila cell interaction, ca2+ dependent, heterophilic cell-cell interaciotn.
    • lectin doman - binds to carbohydrates: glycoproteins, heterophilic interaction
  5. fibronectin
    • Fibronectin is a high-molecular weight (~440kDa) extracellular matrix glycoprotein
    • that binds to membrane-spanning receptor proteins called integrins.[1]
    • In addition to integrins, fibronectin also
    • binds extracellular matrix components such as
    • collagen,
    • fibrin
    • and heparan sulfate proteoglycans (e.g. syndecans).
  6. 4 types of epithelia
    • simple columnar - digestive tract, certical tract
    • simple squamous - blood vessels and body cavities
    • transitional - expansion and contraction urinary b ladder
    • stratified squamous (nonkeratinized) - mouth surface
  7. Cell junctions
    • tight junction; anchoring junction (adherens, desmosomes, hemidesmosomes); gap junction
    • binds cells together to form tissues
    • water and salt tight seal between cells
    • metabolically or electrically couple cells
    • anchor cells to ECM
  8. adherens junction
    • cadheren = ca2+ depdendent
    • a belt formed by clustered Ecadherins connected to actin filaments via anchor proteins
    • beta catenin used to bind to F-actin
    • or p120 + vinculin bind to alpha actinin
  9. Desmosome
    spot of specialized cadherin protiens: desmoglein and desmocollin, interacts with special cytosolic adaptor proteins, connect intermediate filaments
  10. Hemidesmosome
    • on the inner basal surface attache cells to the extracellular matrix - use integrin cell adhesion proteins to attach to laminin, fibronectins; ICAM; collagen; serum proteins... in ECM - non motile
    • important for development, cell migration, bone remodling, signaling...
  11. Tight junction
    • occluding junction
    • divides cell into 2 surfaces: apical and basolateral
    • epithelial, epidermis, intestinal wall, pancreatic ducts
    • functions: restirction of diffusion of membrane components; maintain cell polarity, seals off body cavities (blood-brain barrier
    • Proteins located at tight junction: occludin; claudin; JAMs
  12. Gap junctions
    • communicating junction: metabolic and electric coupling
    • hexagonal cylilndrical particles that compose pores connecting the cytoplasm of adjacent cells
    • composed of connexins (vetebrate) innexins (invetebrate) or pannexins (both)
    • permeability can be regulated by pH, Ca2+ concentration and connexin phosphorylation