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This Article Full Text Full Text (PDF) All Versions of this Article: 295/4/C1045    most recent 90644.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Speich, H. E. Articles by Jennings, L. K. PubMed PubMed Citation Articles by Speich, H. E. Articles by Jennings, L. K.

RECEPTORS AND SIGNAL TRANSDUCTION

Platelets undergo phosphorylation of Syk at Y525/526 and Y352 in response to pathophysiological shear stress

¹Department of Biomedical Engineering, The University of Memphis; and ²Vascular Biology Center of Excellence, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee

Submitted 21 December 2007 ; accepted in final form 12 August 2008

Atherosclerotic plaques can lead to partial vascular occlusions that produce abnormally high levels of arterial wall shear stress. Such pathophysiological shear stress can promote shear-induced platelet aggregation (SIPA), which has been linked to acute myocardial infarction, unstable angina, and stroke. This study investigated the role of the tyrosine kinase Syk in shear-induced human platelet signaling. The extent of Syk tyrosine phosphorylation induced by pathophysiological levels of shear stress (100 dyn/cm²) was significantly greater than that resulting from physiological shear stress (10 dyn/cm²). With the use of phospho-Syk specific antibodies, these data are the first to show that key regulatory sites of Syk at tyrosines 525/526 (Y525/526) and tyrosine 352 (Y352) were phosphorylated in response to pathophysiological shear stress. Increased phosphorylation at both sites was attenuated by pharmacological inhibition of Syk using two different Syk inhibitors, piceatannol and 3-(1-methyl-1H-indol-3-yl-methylene)-2-oxo-2,3-dihydro-1H-indole-5-sulfonamide (OXSI-2), and by inhibition of upstream Src-family kinases (SFKs). Shear-induced response at the Syk 525/526 site was ADP dependent but not contingent on glycoprotein (GP) IIb-IIIa ligation or the generation of thromboxane (Tx) A₂. Pretreatment with Syk inhibitors not only reduced SIPA and Syk phosphorylation in isolated platelets, but also diminished, up to 50%, the platelet-mediated thrombus formation when whole blood was perfused over type-III collagen. In summary, this study demonstrated that Syk is a key molecule in both SIPA and thrombus formation under flow. Pharmacological regulation of Syk may prove efficacious in treating occlusive vascular disease.

GPIb; GPIIb-IIIa; signal transduction; thrombosis; collagen