Integrins[edit] Main article: Integrin Integrins, one of the major classes of receptors within the ECM,[3] mediates cell-ECM interactions with collagen, fibrinogen, fibronectin, and vitronectin.[4] Integrins provide essential links between the extracellular environment and the intracellular signalling pathways, which can play roles in cell behaviours such as apoptosis, differentiation, survival, and transcription.[5] Integrins are heterodimeric, as they consist of an alpha and beta subunit.[6] There are currently 18 alpha subunits and 8 beta subunits, which combine to make up 24 different integrin combinations.[4] Within each of the alpha and beta subunits there is a large extracellular domain, a transmembrane domain and a short cytoplasmic domain.[7] The extracellular domain is where the ligand binds through the use of divalent cations. In general, Mn2+ increases affinity, Mg2+ promotes adhesion to cells, and Ca2+ decreases cell adhesion.[5] Integrins regulate their activity within the body by changing conformation. Most exist at rest in a low affinity state, which can be altered to high affinity through an external agonist which causes a conformational change within the integrin, increasing their affinity.[5] An example of this is the aggregation of platelets;[5] Agonists such as thrombin or collagen trigger the integrin into its high affinity state, which causes increased fibrinogen binding, causing platelet aggregation. Cadherins[edit] Main article: Cadherin The cadherins are homophilic Ca2+ -dependent glycoproteins.[8] The classic cadherins (E-, N- and P-) are concentrated at the intermediate cell junctions, which link to the actin filament network through specific linking proteins called catenins.[8] Each cadherin exhibits a unique pattern of tissue distribution, such as epithelial (E-cadherins), placental (P-cadherins), neural (N-cadherins), retinal (R-cadherins), brain (B-cadherins and T-cadherins), and muscle (M-cadherins).[8] Many cell types express combinations of cadherin types. The extracellular domain has major repeats called extracellular cadherin domains (ECD). Sequences involved in Ca2+ binding between the ECDs are necessary for cell adhesion. The cytoplasmic domain has specific regions where catenin proteins bind.[9] Selectins[edit] Main article: Selectin The selectins are a family of heterophilic CAMs that bind fucosylated carbohydrates, e.g., mucins. The three family members are E-selectin (endothelial), L-selectin (leukocyte), and P-selectin (platelet). The best-characterized ligand for the three selectins is P-selectin glycoprotein ligand-1 (PSGL-1), which is a mucin-type glycoprotein expressed on all white blood cells. 1976 copyright act entitles fair use for non profit educational purposes. I don’t make any money off of videos, and the dmca extends the definition of fair use from the 1976 copyright act

• published: 21 Sep 2015
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