Collagen integrins interactions with

Type I collagen can interact with various other molecules in the extracellular matrix and on the cell surface. Cell receptors of type I collagen have been identified and include the heterodimeric integrin family receptors, ctl, 0 2, olO, and ol 1, especially o2/3l, the receptor tyrosine kinase discoidin domain receptor (DDR), and the heparan sulfate membrane proteoglycan syndecan family... 

The extracellular domains of integrins interact with a variety of profeins of the extracellular matrix. These include fibronectin, fibrinogen, vifronecfin, collagen, and entacfin. Other large cell surface adhesins include laminin and osteopontin (Chapfer 8), thrombospondin, von Willebrand factor, and related proteins. These adhesins appear to depend upon the sequence Arg-Gly-Asp (RGD), which binds nonco-valently to integrins, which act as cell-surface receptors. See also Chapter 12, Section C,9. 

Figure 48-4. Schematic representation of a cell interacting through various integrin receptors with collagen, fibronectin, and laminin present in the ECM. (Specific subunits are not indicated.) (Redrawn after Yamada KM Adhesive recognition sequences. J Biol Chem 1991 266 12809.)...

Integrins themselves are found on nearly all cells and mediate several physiological responses, such as cell-cell and cell-matrix interactions. Three families of integrins, each family with a common beta subunit in combination with distinct alpha subunits, have been recognized. The beta 1 family, also called very late lymphocyte-activation antigen or VLA, has receptors mediating extracellular matrix interactions with molecules such as collagen, laminin, and fibronectin. Naturally, platelets contain many of the receptors of the beta 1 family. 

Receptors (adhesion receptors) that interact with macromolecular components of the extracellular matrix (such as collagen) and convey to the cytoskeletal system instructions on cell migration or adherence to the matrix. Integrins (discussed in Chapter 10) illustrate this general type of transduction mechanism. 

Fibronectin is a cell-surface compound with domains that interact with many compounds, including integrins and extracellular matrix proteins such as collagen. Fibronectin expression can be stimulated by I GF-[3 and by CTGF,41 although increases in fibronectin expression can also be mediated by TGF-(3-independent means 42 We found some evidence of increased expression of fibronectin in FBC tissue, but not to the degree in which I GF-[3, CTGF, and decorin were expressed.16,17... 

Nieswandt B, Brakebusch C, Bergmeier W et al. (2001) Glycoprotein VI but not alpha2betal integrin is essential for platelet interaction with collagen. EMBO J 20 2120-2130... 

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