Glutamate Mediates Platelet Activation through an Ionotropic Glutamate Receptor

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DESCRIPTION (provided by applicant): Cardiovascular disease and stroke are major causes of morbidity and mortality. Although many pathophysiological processes play a role in the development of vascular disease, thrombosis often is the event that precipitates stroke and acute coronary syndromes. Many platelet receptors and activation pathways are conserved in other cell types, including neurons. Platelets release the neurotransmitter glutamate during activation, but the role of glutamate signaling in the vasculature is unknown. We have discovered that platelets express ionotropic glutamate receptors, including the AMPA type receptor (AMPAR) and the Kainic Acid (KA) type receptor (KAR). Furthermore, we demonstrate that AMPA and KA receptor signaling increase platelet activation. We hypothesize that platelets express functional glutamate sensitive complexes that increase agonist induced platelet activation and thrombosis. To explore this hypothesis, we propose the following Specific Aims: Specific Aim 1: To define the mechanisms of glutamate mediated increase in agonist induced platelet activation. We will extend our extensive Preliminary Data to further explore the regulation of platelet activation by ionotropic glutamate receptors. Using flow cytometry, platelet aggregation, and whole cell patch clamp techniques we will further dissect platelet glutamate signaling. Specific Aim 2: To define platelet glutamate receptor accessory molecule interactions. Aim 2 will focus on the molecular machinery that facilitates AMPAR and KAR membrane localization and stability in platelets. Specific Aim 3: To demonstrate that glutamate signaling promotes thrombosis and ischemia-reperfusion injury. To further explore glutamate regulation of platelet function we will use in vivo measurements of platelet function, including bleeding time and thrombosis. We will also demonstrate the importance of the promotion of platelet activation by AMPAR and KAR using a model of ischemia- reperfusion injury. PUBLIC HEALTH RELEVANCE: In 2001, a World Health Report noted atherothrombosis (ischemic heart disease and stroke) to be the leading cause of death worldwide. Platelets have a prominent role in cardiovascular disease and platelet inhibitors are a main therapeutic intervention. The proposed study will help elucidate novel targets for the development of new therapies in the prevention and treatment of cardiovascular disease.