title: Role for ADAP in shear flow-induced platelet mechanotransduction.
abstract: Binding of platelets to fibrinogen via integrin alphaIIbbeta3 stimulates cytoskeletal reorganization and spreading. These responses depend on tyrosine phosphorylation of multiple proteins by Src family members and Syk. Among Src substrates in platelets is adhesion- and degranulation-promoting adapter protein (ADAP), an adapter with potential binding partners: SLP-76, VASP, and SKAP-HOM. During studies of platelet function under shear flow, we discovered that ADAP(-/-) mouse platelets, unlike ADAP+/+ platelets, formed unstable thrombi in response to carotid artery injury. Moreover, fibrinogen-adherent ADAP(-/-) platelets in shear flow ex vivo showed reduced spreading and smaller zones of contact with the matrix. These abnormalities were not observed under static conditions, and they could not be rescued by stimulating platelets with a PAR4 receptor agonist or by direct alphaIIbbeta3 activation with MnCl2, consistent with a defect in outside-in alphaIIbbeta3 signaling. ADAP+/+ platelets subjected to shear flow assembled F-actin-rich structures that colocalized with SLP-76 and the Rac1 exchange factor, phospho-Vav1. In contrast, platelets deficient in ADAP, but not those deficient in VASP or SKAP-HOM, failed to form these structures. These results establish that ADAP is an essential component of alphaIIbbeta3-mediated platelet mechanotransduction that promotes F-actin assembly and enables platelet spreading and thrombus stabilization under fluid shear stress.
authors.affiliation: Department of Medicine, University of California San Diego, La Jolla, CA 92093-0726, USA. akasirer@ucsd.edu
authors.forename: Ana
authors.initials: A
authors.lastname: Kasirer-Friede
authors.forename: Zaverio M
authors.initials: ZM
authors.lastname: Ruggeri
authors.forename: Sanford J
authors.initials: SJ
authors.lastname: Shattil
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000172:deficiency / Q000378:metabolism*; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism* / Q000473:pathology; D002339:Carotid Arteries / Q000378:metabolism / Q000473:pathology; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002465:Cell Movement; D003599:Cytoskeleton / Q000378:metabolism; D005340:Fibrinogen / Q000378:metabolism; D018056:Hemorheology; D042541:Intracellular Space / Q000378:metabolism; D040542:Mechanotransduction, Cellular; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010973:Platelet Adhesiveness; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D051567:Proto-Oncogene Proteins c-vav / Q000378:metabolism; D013314:Stress, Mechanical; D013927:Thrombosis / Q000378:metabolism / Q000473:pathology; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D015815:Cell Adhesion Molecules; C491468:Fyb protein, mouse; D008840:Microfilament Proteins; D010750:Phosphoproteins; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D051567:Proto-Oncogene Proteins c-vav; C092947:SLP-76 signal Transducing adaptor proteins; C496619:Vav1 protein, mouse; D000098662:Vasodilator-Stimulated Phosphoprotein; D005340:Fibrinogen