Cell Adhesion

Ca2+ dependent, dimer repeats, homophilic

E-Cadherin - epithelial sheets - mediates cell-cell adhesion

single pass homophilic cell-cell adhesions (sometimes heterophilic) Ca2+ independent

• 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)

• mediate leukeocyte endothelila cell interaction, ca2+ dependent, heterophilic cell-cell interaciotn.
• lectin doman - binds to carbohydrates: glycoproteins, heterophilic interaction

• 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).

• 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

• 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

• 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

spot of specialized cadherin protiens: desmoglein and desmocollin, interacts with special cytosolic adaptor proteins, connect intermediate filaments

• 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...

• 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

• 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