Premium
Concurrent signaling from Gα q ‐ and Gα i ‐coupled pathways is essential for agonist‐induced αvβ3 activation on human platelets
Author(s) -
Paul B. Z. S.,
Vilaire G.,
Kunapuli S. P.,
Bennett J. S.
Publication year - 2003
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1046/j.1538-7836.2003.00099.x
Subject(s) - vitronectin , integrin , osteopontin , chemistry , platelet , microbiology and biotechnology , p2y12 , platelet activation , adenosine diphosphate , cytoskeleton , platelet membrane glycoprotein , apyrase , gpvi , cytochalasin d , biochemistry , receptor , biology , endocrinology , immunology , platelet aggregation , aspirin , cell , clopidogrel
Summary. The integrin αvβ3 mediates platelet adhesion to the matrix protein osteopontin and likely is the predominant integrin mediating platelet adhesion to the matrix protein vitronectin. To address the mechanism that regulates αvβ3 activity in platelets, we measured the effect of the P2Y 1 antagonist adenosine 3′‐phosphate‐5′‐phosphate (A3P5P) and the P2Y 12 antagonist AR‐C66096 on ADP‐stimulated platelet adhesion to osteopontin and vitronectin. Each antagonist completely inhibited platelet adhesion, implying that concurrent stimulation of P2Y 1 and P2Y 12 was required to activate αvβ3. The reducing agent dithiothreitol and Mn 2+ also induced platelet adhesion to osteopontin, but did so without stimulating platelet activation. Thus, these data suggest that ADP stimulation regulates αvβ3 activity by perturbing the conformation of its extracellular domain. The actin polymerization inhibitors cytochalasin D and latrunculin A also induced platelet adhesion to osteopontin and vitronectin. Thus, αvβ3 activity in resting platelets appears to be constrained by the platelet cytoskeleton. Moreover, the effect of these agents was inhibited by A3P5P and AR‐C66096 at micromolar and subnanomolar concentrations, respectively, suggesting that subthreshold platelet stimulation by ADP was required. Our data suggest that signals from both Gα q ‐ and Gα i ‐coupled receptors converge to release cytoskeletal constraints on αvβ3. We propose that the release of cytoskeletal constraints and a concurrent increase in affinity for ligands is responsible for αvβ3‐mediated platelet adhesion.