N-methyl-D-aspartate (NMDA) receptors constitute the major subtype of glutamate receptors and normally participate in rapid excitatory synaptic transmission throughout the CNS. To date, a variety of NMDA receptor subunit proteins (NR1, NR2A-D) have been cloned. Native NMDA receptors appear to be heteroligomeric complexes consisting of an essential NR1 subunit and one or more regulatory NR2 subunits (NR2A-D) and possibly the more recently identified NR3 subunit. Activation of NR2A and NR2B receptor channels are permeable to Na+ and K+ and also to Ca2+, which triggers multiple intracellular catabolic processes, leading to the irreversible death of neuronal cells. Recently, we have used reverse phase nano-LC-MS/MS mass spectrometry to analyze protein components in the NR2B receptor complex from forebrain of mice that had been subjected to sham or focal cerebral ischemia. We have shown that cerebral ischemia recruits death-associated protein kinase (DAPK1) into the NR2B receptor complex. DAPK1 is one member of Ca2+/calmodulin (CaM)-dependent serine/threonine kinase family and functions as a critical mediator of cell death. Whole-cell patch clamp recordings have demonstrated that activation of DAPK1 increases the NR1/NR2B receptor-mediated currents. Subsequently, we have generated genetically modified mice (cdDAPK1), in which catalytic domain of DAPK1 is selectively deleted. We have found that neurons in the forebrain of the cdDAPK1 mutant mice are resistant to ischemic insults. Thus, we hypothesize that DAPK1 physically and functionally interacts with NR2B receptors and this interaction contributes to neuronal injury in ischemic stroke. Proposed studies will address this question. To date, all clinical stroke trials targeting glutamate receptors (AMPA or NMDA) have failed, possibly because receptor antagonists block the physiological actions of glutamate as well. This proposal describes, for the first time, a molecular approach to selectively block the pathological effects of NR2B receptors by targeting DAPK1. Thus, this approach should not affect the physiological actions of glutamate receptors in the brain, thereby defining a promising target for stroke therapy.
Stroke is a third leading cause of death in the United States. A critical feature of the disease is selective degeneration of neurons in the brain by activation of glutamate receptor channels. To date, all clinical stroke trials targeting glutamate receptors have, however, failed, because receptor antagonists block the physiological actions of glutamate as well. This proposal describes, for the first time, a molecular approach to selectively block the pathological effects of glutamate receptors by targeting DAPK1 enzyme. Thus, this approach should not affect the physiological actions of glutamate receptors in the brain, thereby defining a promising target for stroke therapy.
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