Regulation of Calcium Channel Function by the Rem GTPase

描述（由申请人提供）：电压激活钙通道具有两种关键功能：调节细胞兴奋性和调节钙离子进入。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Ca通道的基本机制对于理解基本通道生理学和治疗干预都是重要的。在过去的资助期间，我们已经确定了雷姆GTdR作为一种新的调节剂的I（钙）。最初认为Rem与CaV β亚基的结合通过抑制通道运输来长期调节I（Ca）。我们的研究已经推翻了这一假设，证明雷姆介导的钙离子通道的调节，而不改变表面密度。相反，Rem似乎通过与CaV β和CB/IQ结构域附近的近端CaV1.2 C-末端的相互作用来调节Ca通道活性。两个最生理相关的控制I（Ca）是PKA-调制和钙调素（CaM）-调制。我们最近的研究表明，雷姆调节I（钙）的反应，这些信号通路。因此，Rem似乎有助于β-肾上腺素能和Ca-CaM对I（Ca）的控制。待检验的特定假设是Rem GT3通过与CaVb亚基和CaV1.2 C末端的相互作用调节心肌中的Ca通道活性。三个假设驱动的目标集中在我们的研究和推进这种新的调控机制的知识。目的1将通过检测Rem丢失对Ca通道调节的影响来探索Rem介导的通道调节的性质。Rem敲除小鼠的初步表征表明：i）Rem在体内起调节I（Ca）的作用; ii）有助于心脏对压力超负荷的反应;以及iii）有助于心肌细胞生长/成熟稳态。目的2将确定Rem与CaV β或CB/IQ的相互作用是否对I（Ca）的调节至关重要。目的3将研究Ca-钙调蛋白如何调节Rem介导的通道阻滞，并确定PKA磷酸化是否改变Rem膜运输或Rem与其结合伴侣之间的相互作用。RGK G蛋白作为Ca通道活性的调节剂发挥作用，有助于调节I（Ca）、兴奋-收缩偶联和对压力超负荷的心脏反应。本研究的目的是更深入地了解RGK/Ca通道调节的生理学分支和分子机制，以加速RGK在心血管疾病中的治疗开发。

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.