The experiments in this application will test the hypothesis that clusters of voltage-gated L-type CaV1.2 channels are capable of undergoing coordinated openings (""""""""coupled gating""""""""), amplifying Ca2+ influx into arterial smooth muscle. A key discovery is that Ca2+ influx via coupled CaV1.2 channels plays a critical role in excitation-contraction (EC) coupling and excitation-transcription (ET) coupling in arterial myocytes. Preliminary data suggest that association of CaV1.2 channels with the anchoring protein AKAP150 is necessary for coupled gating activity in these cells. The significance of these findings is underscored by the observation that the frequency of coupled CaV1.2 gating events increases in arterial smooth muscle during hypertension and that loss of AKAP150 protects against coupled gating and hypertension. The project has two specific aims designed to investigate the mechanisms and physiological implications of these findings.
Specific aim 1 is to test the hypothesis that coupled gating of CaV1.2 channels amplifies Ca2+ influx in arterial myocytes.
Specific aim 2 is to test the hypothesis that AKAP150 is required for increased coupled CaV1.2 channel activity and the induction of arterial dysfunction during the development of hypertension. The methods that will be used to achieve these aims include patch-clamp electrophysiology, optical clamping, light- and chemically-induced dynamic targeting of kinases to cellular membranes, light-induced activation of adrenergic signaling (i.e., optogenetics), confocal, and TIRF microscopy. Experiments will involve new transgenic, knock in, and knock out mice. This work will generate fundamental information on the mechanisms by which AKAP150 and CaV1.2 channels control of excitability, gene expression, and EC coupling in vascular smooth muscle under physiological and pathological conditions.
Recent data from the Centers for Disease Control and Prevention suggest that, in the USA, nearly 33% of adults ages 20 and older suffer of hypertension, a clinical syndrome characterized by increased vascular tone. However, the mechanisms underlying these pathological changes in vascular function are poorly understood. The experiments proposed in this application have important implications for public health because they investigate the mechanisms by which a new Ca2+ signaling modality regulates the function of vascular smooth muscle under normal conditions and during the development of hypertension. The results of the proposed work may lead to the development of rational strategies for the treatment of hypertension.
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