Calcium signaling plays a critical role in the pathology of cerebral ischemia. However, clinical trials testing treatments which block calcium signaling have failed to improve outcomes in patients with ischemic stroke. One possible explanation is that these agents also inhibited potentially beneficial effects of raised intracellular calcium. Emerging data suggest that calcium may trigger endogenous protective pathways in the ischemic brain. A logical solution is to augment the endogenous protective mechanisms induced by increased calcium, while inhibiting the detrimental effects of excessive calcium. We discovered that CaMKK (calcium/calmodulin-dependent protein kinase kinase), a major kinase in calcium signaling, is implicated in endogenous neuroprotection after stroke. The overall goal of this proposal is to study the functional roles of CaMKK in stroke and uncover the mechanism by which CaMKK signaling activates pro-survival pathways after stroke. CaMKK activates its downstream kinases CaMK I and CaMK IV (together these three kinases are termed the CaMK cascade). We will test the hypothesis that CaMK I/IV are important mediators of CaMKK's neuroprotective actions in stroke. Both kinases target multiple critical cell death/survival pathways and our preliminary data definitively show that loss of components of this cellular cascade exacerbate ischemic injury. Finally, our and others' findings have demonstrated that there is a decline in the levels of proteins involved in CaMK signaling in the brain during aging. We will test if activating this cascade in young and aging brain reduces stroke damage and improves post-stroke functional recovery. We will use a combination of pharmacological tools, mice with targeted deletions of these kinases, and viral transfection systems to over-express or in-activate these kinases in vivo. These studies represent the first steps in improving our understanding of the endogenous signaling pathways that are activated by calcium in the ischemic brain.
Stroke is the third leading cause of death in the U.S., and the most common cause of disability. We have recently found that CaMKK signaling is an important contributor to the protection induced by the brain during injury. In this application, we will purse a focused investigation on the functional role of this signaling pathway in stroke in an attempt to develop novel treatmentsfor stroke.
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