Abstract 24: Thrombus Formation is Impaired in Glutamate Receptor Interacting Protein 1 Deficient Mice
Platelets contribute to the pathogenesis of myocardial infarction and stroke. Understanding mechanisms of platelet activation and thrombus formation may provide new targets for anti-platelet therapies. GRIP1 (glutamate receptor interacting protein 1) is a 7 PDZ domain scaffolding protein which localizes receptors at the membrane in a regulated manner. Previous work has shown that glutamate receptors increase platelet activation through glutamate receptor signaling and we wanted to investigate the regulation of these receptors. In the neuron, GRIP1 regulates surface expression of GluR2, however, GRIP1 KO mice are embryonic lethal due to hemorrhage and hypovolemia indicating severe vascular defects. Endothelial cells do not appear to express GRIP1, therefore, we hypothesize that GRIP1 mediates platelet activation by PDZ domain coordination of protein-protein interactions. We have discovered that GRIP1 is present in mouse and human platelets. To explore the role of GRIP1 in platelets we have created a platelet-specific GRIP1-/- mouse. GRIP1-/- mice have normal platelet counts but significantly decreased thrombus formation (p<0.05) during ferric chloride injury and their bleeding time is significantly longer (p<0.05) in tail bleeding assays. They have no observed spontaneous bleeding or premature death. CD62P and JON/A expression after stimulation with thrombin, 2-meADP, U46619, or convulxin was unchanged compared to WT mice. To determine which protein-protein interactions could be mediating the GRIP1 effects in platelets, we performed IP of GRIP1 and mass spectrometry. GRIP1 showed an association with the GP1b complex. Aggregation after stimulation with thrombin and 2-meADP is also impaired. Ongoing studies will determine whether specific members of the GP1b complex associate with GRIP1 in IP assays, flow chamber adhesion, and botrocetin aggregation to complement our in vivo data. Based on our data, GRIP1 has a central role in platelet thrombus formation through non-glutamate receptor dependent interactions.
- © 2013 by American Heart Association, Inc.