Calcium-dependent gating of the L-type Calcium Channel

描述（由申请人提供）：电压门控L型Ca 2+通道的钙依赖性失活（CDI）在心脏生理学中具有根本重要性。 它是动作电位持续时间的主要决定因素，因此是兴奋-收缩偶联的重要调节剂。 在心力衰竭中，异常CDI可能是血栓形成的触发因素。 CDI也是反馈抑制的一个突出例子，其中渗透通道的Ca 2+触发加速通道失活。 本研究的目的是通过关注最近发现的分子组分来确定CDI的分子机制：1）Ca 2-感受器是钙调素（CaM），它与通道的成孔亚基α 1c组成性结合; 2）α 1c中的CDI效应子是“IQ基序”，即α 1c C-末端尾部的CaM结合位点;本研究的目的包括三个方面：1）确定CaM在失活调控中的结构作用; 2）确定IQ模体在失活调控中的结构作用; 3）确定EF-手在CDI中的作用。 前两个目标将确定钙调素和IQ基序的分子作用，在钙依赖性和钙非依赖性失活必不可少。 第三个目的提出了新的假说，关于有争议的EF-手基序内α 1C的作用。 我们已经确定了第二EF手，并显示初步结果表明，两个EF手形成一个结构对，类似于一个单一的叶钙调素。 我们的初步数据使我们能够提出一个模型，结合钙调素，IQ基序，EF-手对功能在调节失活。 这些新的假说有望显着改变目前的CDI模型，也提供了一个模板，了解电压门控通道失活。这项工作将增加我们对正常心脏功能的理解，以及这些过程在病理生理状态下如何受到干扰，如心力衰竭和心肌梗死。

DESCRIPTION (provided by applicant): Calcium-dependent inactivation (CDI) of voltage-gated L-type Ca2+ channels is of fundamental importance in cardiac physiology. It is a major determinant of the action potential duration and thus an essential regulator of excitation-contraction coupling. Disturbed in heart failure, abnormal CDI may be a trigger for arrhythmogenesis. CDI is also a pre-eminent example of feedback inhibition, in which the very Ca2+ that permeates the channel triggers accelerated channel inactivation. This proposal aims to identify the molecular mechanisms underlying CDI by focusing on the molecular components that have recently been identified: 1) the Ca2-sensor is calmodulin (CaM), constitutively bound to the channel's pore-forming subunit alpha 1c; 2) the CDI effector in alpha 1c is the "IQ motif', a CaM binding site in the alpha 1c C-terminal tail; and 3) an EF-hand motif in the C-terminal tail serves an essential structural role.This proposal contains three specific aims: Aim 1) Determine the structural role of CaM in the regulation of inactivation Aim 2) Determine the structural role of the IQ motif in the regulation of inactivation and Aim 3) Define the role of the EF-hand(s) in CDI. The first two Aims will identify the molecular roles of CaM and the IQ motif, essential in both Ca2+-dependent and Ca2+-independent inactivation. The third Aim proposes novel hypotheses regarding the role of the controversial EF-hand motif within alpha 1c. We have identified a second EF-hand, and show preliminary results indicating that the two EF-hands form a structural pair, similar to a single lobe of CaM. Our preliminary data allow us to propose a model that incorporates how CaM, the IQ motif, and the EF-hand pair function in regulating inactivation. These novel hypotheses promise to significantly alter the current model of CDI and also provide a template for the understanding of voltage-gated channel inactivation. This work will augment our understanding of normal cardiac function and how these processes are perturbed under pathophysiological states, such as heart failure and arrhythmogenesis.