Regulation of Calcium Channel Function by the Rem GTPase

描述（由申请人提供）：电压激活的钙通道具有两个关键功能：调节细胞兴奋性和调节钙的进入。l型钙通道密度或功能的改变与多种心血管疾病有关。因此，阐明调节钙通道的基本机制对于理解基本通道生理学和治疗干预都很重要。在过去的资助期间，我们已经确定了Rem GTPase是一种新的I（Ca）调制器。最初认为Rem与cavβ -亚基的关联通过抑制通道运输来长期调节I（Ca）。我们的研究反驳了这一假设，证明rem介导的Ca通道调节没有改变表面密度。相反，Rem似乎通过与cav β和靠近CB/IQ结构域的近端CaV1.2 c端相互作用来调节Ca通道活性。两个最相关的生理控制I（Ca）是pka调节和钙调素（CaM）调节。我们最近的研究表明，Rem调节I（Ca）对这些信号通路的反应。因此，Rem似乎对I（Ca）的β -肾上腺素能和Ca- cam控制都有贡献。需要验证的具体假设是Rem GTPase通过与cavb亚基和CaV1.2 C-末端的相互作用来调节心肌中Ca通道的活性。三个假设驱动的目标集中了我们的研究，并推进了对这种新型调节机制的认识。目的1将通过检查Rem损失对Ca通道调节的影响来探索Rem介导的通道调节的本质。Rem基因敲除小鼠的初步表征表明：i) Rem在体内具有调节i （Ca）的功能；Ii)有助于心脏对压力过载的反应；iii)有助于心肌细胞生长/成熟的稳态。目的2将确定Rem与CaVbeta或CB/IQ的相互作用是否对I（Ca）的调制至关重要。Aim 3将研究钙调蛋白如何调节Rem介导的通道阻断，并确定PKA磷酸化是否会改变Rem膜运输或Rem与其结合伙伴之间的相互作用。RGK - g蛋白作为Ca通道活性的调节剂，有助于调节I（Ca）、兴奋-收缩耦合和心脏对压力过载的反应。本研究的目的是更深入地了解RGK/Ca通道调节的生理后果和分子机制，以加快RGK在心血管疾病治疗中的应用进展。

DESCRIPTION (provided by applicant): Voltage-activated Ca channels serve two critical functions: the regulation of cellular excitability and the regulation of Ca entry. Alterations in the density, or function, of L-type Ca channels are implicated in a variety of cardiovascular diseases. Thus, elaborating the basic mechanisms that regulate Ca channels is important for understanding both fundamental channel physiology and for therapeutic intervention. During the past funding period, we have identified the Rem GTPase as a novel modulator of I(Ca). It was originally thought that Rem association with CaVbeta- subunits chronically regulated I(Ca) by inhibiting channel trafficking. Our studies have disproved this hypothesis, demonstrating Rem-mediated Ca channel regulation without changes in surface density. Instead, Rem seems to modulate Ca channel activity through interactions with both CaVbeta and the proximal CaV1.2 C-terminus near the CB/IQ domain. Two of the most physiologically relevant controls of I(Ca) are PKA-modulation and calmodulin (CaM)-modulation. Our most recent studies suggest that Rem modulates I(Ca) responses to each of these signaling pathways. Thus, Rem appears to contribute to both beta-adrenergic and Ca-CaM control of I(Ca). The specific hypothesis to be tested is that Rem GTPase regulates Ca channel activity in cardiac muscle through interactions with both CaVb-subunits and the CaV1.2 C- terminus. Three hypothesis driven aims focus our studies and advance knowledge of this novel regulatory mechanism. Aim 1 will explore the nature of Rem-mediated channel regulation by examining the effect of Rem loss on Ca channel regulation. Initial characterization of Rem knockout mice indicates that i) Rem functions in vivo to regulate I(Ca); ii) contributes to the cardiac response to pressure-overload; and iii) contributes to cardiac myocyte growth/maturation homeostasis. Aim 2 will determine whether interaction of Rem with CaVbeta or CB/IQ is critical for modulation of I(Ca). Aim 3 will investigate how Ca- calmodulin modulates Rem-mediated channel blockade, and determine whether PKA phosphorylation alters Rem membrane trafficking or the interaction between Rem and its binding partners. RGK G-proteins function as modulators of Ca channel activity, contributing to regulation of I(Ca), excitation- contraction coupling, and the cardiac response to pressure-overload. The goal of this research is to generate a deeper understanding of the physiological ramifications and molecular mechanism of RGK/Ca channel modulation, to speed progress toward the therapeutic exploitation of RGKs in cardiovascular disease. PUBLIC HEALTH RELEVANCE: Voltage-activated calcium channels serve two critical functions: the regulation of calcium entry and the control of heart contraction. Changes in the number, or function, of L-type calcium channels are implicated in a variety of cardiovascular disease, including atrial fibrillation, heart failure, and ischemic heart disease. Thus, understanding the basic mechanisms that regulate calcium cannels is important in understanding both fundamental heart muscle performance and for therapeutic intervention. We have identified a family of proteins that regulate calcium channels and the goal of this research is to speed progress toward the day when these proteins can be used to treat heart disease.