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Biochem Pharmacol. 2000 Oct 15;60(8):1069-74.

The integrin alpha IIb/beta 3 in human platelet signal transduction.

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Inserm Unite 326, Hopital Purpan, IFR 30, 31059 Toulouse, France.


Platelets are critical for the maintenance of the integrity of the vascular system and are the first line of defence against haemorrhage. When they encounter a subendothelial matrix exposed by injury to a vessel, platelets adhere, are activated, and become adhesive for other platelets so that they aggregate. alpha IIb/beta 3, a platelet-specific integrin, is largely prominent amongst the adhesion receptors and is essential for platelet aggregation. The ligands for alpha IIb/beta 3 are the multivalent adhesive proteins fibrinogen and von Willebrand factor. In resting platelets, alpha IIb/beta 3 is normally in a low activation state, unable to interact with soluble fibrinogen. Stimulation of platelets with various agonists will induce a conformational change in alpha IIb/beta 3 (inside-out signalling), which is then able to bind soluble fibrinogen resulting in the onset of platelet aggregation. However, fibrinogen binding to its membrane receptor is not simply a passive event allowing the formation of intercellular bridges between platelets. Indeed, a complex signalling pathway triggered by integrin ligation and clustering (outside-in signalling) will regulate the extent of irreversible platelet aggregation and clot retraction. Amongst the signalling enzymes activated downstream of alpha IIb/beta 3 engagement, phosphoinositide 3-kinase plays an important role in the control of the irreversible phase of aggregation.

[Indexed for MEDLINE]

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