Platelets integrins

The role of the platelet integrin GPIIb/IIIa receptor and its potential utility as a radio-diagnostic agent in the rapid detection of thromboembolic events has been demonstrated [6]. This approach may be useful for the noninvasive diagnosis of various thromboembolic disorders. 

Collagen is a major component of connective tissue that becomes exposed at the subendothelium of injured blood vessels. It contributes to platelet adhesion and also plays a role in platelet activation by binding to several receptors on platelets such as integrin a 2(3 1 or glycoprotein VI (GP VI). 

Table 52-11. Examples of integrins that are important in the function of neutrophils, of other white blood cells, and of platelets. ...

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. 

Thus, while glycoprotein Ia/IIa (a2Pj) binds to collagen, glycoprotein Ic/IIa (a ) binds to fibronectin (5). The other integrin belonging to the beta 1 family that is involved in platelet adhesion is ct6P, which binds laminin. 

In the intact blood vessel, ligands involved in adhesion to platelets, such as collagen, fibronectin, and von Willebrand factor, are sequestered in the subendothelium, thus preventing access to platelet adhesive receptors. Table 1 summarizes the functions of platelet membrane integrin receptors. 

Therefore, RSNOs appear to regulate PDI-dependent adhesion by competitively inhibiting integrin-ligand disulfide bond formation and, in the process, producing NO which prevents further activation of recruited platelets via the GC/G-kinase route. 

D. W., Farndale, R. W., Enzymatically catalyzed disulfide exchange is required for platelet adhesion to collagen via integrin alpha 2 beta l, Blood 102 (2003), p. 2085-2092... 

Miao, W.M., Vasile, E., Lane, W.S., and Lawler, J., 2001, CD36 associated with CD9 and integrins on human blood platelets. Blood 97 1689-1696. 

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