Mechanisms of Long-term Cardiac Ion Channel Regulation

描述（由申请人提供）：心肌细胞中的Ca失调有助于心脏发育缺陷和衰老心脏疾病。本研究的长期目标是提供一种分子机制来解释心脏L型钙通道（LTCC）如何感知和抑制稳态调节心肌细胞的信号。心肌细胞提出了一个难题，相对于钙信号的核。在每个心动周期期间，细胞溶质Ca幅度变化>10倍，但Ca的改变以某种方式被差异解码用于长期转录信号传导。在此资助期间，我们将测试钙通道活性和心脏L型钙通道本身是否编码钙信号进行长期调节。在过去的研究期间，我们发现RGK长期抑制伊卡，L（LTCC电流），并且这种RGK对伊卡，L的抑制导致CaV 1.2 mRNA的补偿性上调。这表明伊卡，L阻断可能是细胞核中转录事件的信号传导。在新的研究中，我们证实并扩展了这一概念，表明LTCC药理学阻断，而不是内部钙一般是负责扰乱心脏发育。沿着相同的思路，在成熟心脏中，LTCC的长期阻断也引起LTCC和伊卡，L的代偿性上调。我们的驱动假设是，信号传导不是简单地由钙决定，而是由活性钙通道决定。LTCC的移动的区段定位于细胞核或t-小管的发现，以及最近报道该肽是转录因子，推动了令人兴奋的新假设，即LTCC的该区段调节LTCC表达。我们将研究这方面的长期渠道管制在三个目标：1。我们将评估LTCC的一个结构域的核转位，并确定LTCC活性和亚细胞定位之间的相互作用;我们将确定LTCC转录自我调节的能力; 3.我们将确定SL Ca处理蛋白对LTCC阻断的代偿性变化。这项工作可能提供了一个缺失的分子之间的联系LTCC功能和下游信号事件。公共卫生相关性：这些研究表明，广泛使用的用于阻断LTCC的临床相关药物可能会通过矛盾地增加LTCC功能而无意中加剧心脏功能障碍。这一提议将导致对一种新机制的理解，即控制心脏电活动的离子通道也可能控制对维持心脏结构和功能至关重要的长期信号通路。

DESCRIPTION (provided by applicant): Ca dysregulation in cardiac myocytes contributes to heart development defects and diseases of the aging heart. The long-term objective of this proposal is to provide a molecular mechanism that explains how cardiac L-type Ca channels (LTCC) sense and transduce signals that homeostatically regulate cardiac myocytes. Cardiac myocytes present a conundrum with respect to Ca signaling to the nucleus. Cytosolic Ca amplitude varies >10-fold during each cardiac cycle, yet alterations of Ca somehow are differentially decoded for longer-term transcriptional signaling. In this funding period we will test whether Ca channel activity and the cardiac L-type Ca channel itself encodes Ca signaling for long-term regulation. In the past funding period we discovered that RGK chronically inhibited ICa,L (LTCC current), and this RGK inhibition of ICa,L resulted in a compensatory up-regulation of CaV1.2 mRNA. This suggests that ICa,L block may signal transcriptional events in the nucleus. In new studies we confirmed and extended this notion by showing that LTCC-pharmacological- block, but not internal Ca in general is responsible for perturbing heart development. Along the same lines, in mature heart, long-term blockade of LTCC also causes a compensatory up-regulation of LTCC and ICa,L. Our driving hypothesis is that signaling is not simply determined by Ca, but by active Ca channels. The discovery that mobile segment of LTCC is localized to the nucleus or t-tubules coupled with the recent report that this peptide is a transcription factor drives the exciting new hypothesis that this segment of the LTCC, regulates LTCC expression. We will study this aspect of long-term channel regulation in three aims: 1. We will assess nuclear translocation of a domain of the LTCC, and determine the interaction between LTCC activity and sub- cellular localization; 2. We will determine the ability of LTCC to auto-regulate itself transcriptionally; and 3. We will determine the compensatory changes of SL Ca handling proteins in response to LTCC blockade. This work may provide a missing molecular link between LTCC function and downstream signaling events. PUBLIC HEALTH RELEVANCE: These studies show that widely used clinically-relevant drugs that are used to block LTCC may inadvertently exacerbate heart dysfunction by paradoxically increasing LTCC function. This proposal will lead to understanding of a new mechanism whereby ion channels that control cardiac electrical activity also may control long-term signaling pathways that are critical for maintenance of cardiac structure and function.