Platelets play a key role in hemostasis and various diseases including arterial thrombosis. Glycoprotein VI (GPVI) mediates adhesion to collagen structures exposed at sites of vascular injury and subsequent platelet activation. We determined the effects of specific activation of GPVI on the human platelet proteome. Isolated human platelets were stimulated with an activating monoclonal antibody specific for GPVI. Platelet proteins were analyzed by 2-dimensional difference gel electrophoresis (2D-DIGE) and mass spectrometry. We identified 8 differentially abundant proteins associated with cell signaling, metabolism, organization and rearrangement of the cytoskeleton, and membrane trafficking. Differentially abundant proteins included aldose reductase (AR), beta-centractin, charged multivesicular body protein 3, Src substrate cortactin, ERp57, and pleckstrin. Importantly, GPVI-modulated protein abundance was functionally relevant. Correspondingly, AR enzyme activity significantly increased upon GPVI activation and inhibition of AR resulted in reduced platelet aggregation. Furthermore, ERp57 was released upon ligation of platelet GPVI and increased the activity of tissue factor, a major initiator of blood coagulation. In summary, GPVI activation results in differential changes in abundance of platelet proteins, including AR and ERp57, which support platelet aggregation and plateletdependent coagulation. These results provide further insight into the mechanisms that underlie platelet activation through the GPVI receptor and may help to identify novel pharmacologic targets.

Background: Platelets play a key role in haemostasis and in the pathophysiology of various diseases including arterial thrombosis. Glycoprotein (GP)VI, the major platelet collagen receptor, mediates platelet activation and firm adhesion to collagen structures exposed at sites of vascular injury. Here, we determined the effects of specific activation of GPVI on the human platelet proteome by two-dimensional differential in-gel electrophoresis (2D-DIGE) and mass spectrometry. Methods and Results: Platelets from healthy human donors were isolated and purified. Platelets were stimulated with an activating monoclonal antibody specific for GPVI, or control IgG. Platelet proteins were subjected to 2D-DIGE with extensive software-assisted image analysis. Subsequent identification of the differentially abundant proteins was carried out by MALDI TOF/TOF MS and LC ESI-MS/MS. We identified 8 differentially regulated proteins associated with cell signaling, metabolism, organization and rearrangement of the cytoskeleton, and membrane trafficking. Differentially abundant proteins included pleckstrin, beta-centractin, src substrate cortactin, charged multivesicular body protein 3, aldose reductase and protein disulfide isomerase-associated 3 precursor. Conclusion: Specific platelet activation via GPVI results in the differential regulation of several proteins. The results provide further insight into the mechanisms that underlie platelet activation through the GPVI receptor, which may help to identify novel pharmacological targets.