Granule exocytosis is an essential platelet function, contributing not only to hemostasis and thrombosis, but also to inflammation, wound healing, malignancy, and angiogenesis. Previous efforts to understand the molecular mechanisms of granule exocytosis have identified the SNARE machinery and chaperone proteins required for membrane fusion. Studies described in this proposal will evaluate the premise that this machinery serves a role in sorting specific cargos to distinct subpopulations of -granules and enabling differential release of granule contents upon platelet activation. We will study granule segregation and secretion in mice lacking VAMP-3, VAMP-5, VAMP-7, and VAMP-8. Cytoskeleton dynamics that occur during platelet spreading can influence SNARE interactions and modify granule exocytosis. We will evaluate granule exocytosis during platelet spreading. These studies will also assess the role of exocytosis in providing membrane for growing actin structures at the periphery of adherent platelets and for directed spreading and movement on micropatterned matrices of adhesion proteins. Use of high-speed intravital microscopy will be used to monitor release of granules from individual platelets during thrombus formation in vivo. These approaches will allow us to evaluate the hypothesis that the mechanism of granule secretion is altered in adherent platelets compared to suspension platelets. We will also evaluate the role of dynamins in controlling fusion pore dynamics, demonstrating a level of control of platelet exocytosis that occurs following SNARE-mediated membrane fusion. These studies will use single-cell amperometry to monitor the release of individual granules from single platelets. The role of dynamins in controlling platelet exocytosis during thrombus formation in vivo will evaluate the hypothesis that the platelet fusion pore can be regulated to control thrombus formation. These experiments will address poorly understood aspects of platelet granule exocytosis and provide a foundation for targeting select platelet membrane fusion events during thrombosis.
Arterial clot formation causes myocardial infarction, strokes, and vascular disease and is the single most common cause of morbidity and mortality in the U.S. Platelets serve a central role in arterial thrombosis. During incorporation into thrombi, platelets secrete factors that propagate thrombus formation. We will identify platelet proteins responsible for platelet granule secretion and, thereby, identify new targets for inhibiting arteril occlusive disease.
| De Ceunynck, Karen; Peters, Christian G; Jain, Abhishek et al. (2018) PAR1 agonists stimulate APC-like endothelial cytoprotection and confer resistance to thromboinflammatory injury. Proc Natl Acad Sci U S A 115:E982-E991 |
| Sharda, Anish; Flaumenhaft, Robert (2018) The life cycle of platelet granules. F1000Res 7:236 |
| Flaumenhaft, Robert (2017) Advances in vascular thiol isomerase function. Curr Opin Hematol 24:439-445 |
| Flaumenhaft, Robert; De Ceunynck, Karen (2017) Targeting PAR1: Now What? Trends Pharmacol Sci 38:701-716 |
| Stopa, Jack D; Neuberg, Donna; Puligandla, Maneka et al. (2017) Protein disulfide isomerase inhibition blocks thrombin generation in humans by interfering with platelet factor V activation. JCI Insight 2:e89373 |
| Bekendam, Roelof H; Bendapudi, Pavan K; Lin, Lin et al. (2016) A substrate-driven allosteric switch that enhances PDI catalytic activity. Nat Commun 7:12579 |
| Flaumenhaft, Robert (2016) SERCAmnavigating calcium signaling in platelets. Blood 128:1034-5 |
| Atefi, Gelareh; Aisiku, Omozuanvbo; Shapiro, Nathan et al. (2016) Complement Activation in Trauma Patients Alters Platelet Function. Shock 46:83-8 |
| Jain, Abhishek; Graveline, Amanda; Waterhouse, Anna et al. (2016) A shear gradient-activated microfluidic device for automated monitoring of whole blood haemostasis and platelet function. Nat Commun 7:10176 |
| Flaumenhaft, R (2016) Probing for thiol isomerase activity in thrombi. J Thromb Haemost 14:1067-9 |
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