EXCEED THE SPACE PROVIDED. Ca_+entry through Cav2.1 (P/Q-type) channels initiates neurotransmitter release at most central synapses. Because small changes in intracellular Ca 2+ can significantly alter synaptic efficacy, regulation ofpresynaptic Car2.1 channels can powerfully influence processes of information transfer and storage in the brain. Cav2.1 channels undergo a feedback regulation by Ca 2+ mediated by calmodulin (CAM)binding to the pore-forming ot_2.1subunit of these channels. CaBP1 is representative of a family of neuronal CaZ+-bindingproteins (NCBPs) that are related to CaM, but are expressed primarily in neurons. CaBP1 also binds to a12.1, but has surprisingly different effects than CaM in regulating Cav2.1 function. A splice variant of CaBP 1, caldendrin, also associates with Cav2.1 channels both in transfected cells and in the brain. Therefore, presynaptic Ca 2+ signals and synaptic strength may depend on the differential modulation of Cav2.1 by CaBP1, CaM, or other NCBPs. The goal of this proposal is to characterize the molecular mechanisms and neurobiological significance of Car2.1 modulation by CaBP 1. Accomplishing this objective may resolve longstanding questions regarding the diversity of Cav2.1 channels in the brain, and suggest alternative therapeutic strategies for treating disorders linked to genetic defects in Cav2.1 such as familial hemiplegic migraine, spinocerebellar ataxia, and absence epilepsy. Molecular biology, immunochemistry, and electrophysiology will be used to address four specific aims: (1) to define the molecular determinants in c_12.1for binding to CaBP1 and CaM; (2) to determine how structural differences between CaBP1 and CaM affect interactions with Car2.1; (3) to characterize the effect of CaBP 1on the pharmacological properties of Cav2.1; and (4) to compare Cav2.1 regulation by CaBP 1 and caldendrin and colocalization of these proteins in the brain. These studies may reveal how other NCBPs could interact with target molecules thought to be regulated primarily by CaM, which may illuminate novel mechanisms controlling the development, plasticity, and ultimately, the behavioral output of the nervous system. PERFORMANCESITE( ========================================Section End===========================================
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