Mechanisms of Long-term Cardiac Ion Channel Regulation

心肌细胞中钙离子的异常调节导致心脏发育缺陷和心脏疾病 老化的心脏。这项提议的长期目标是提供一种分子机制，解释如何 心脏L型钙通道(LTCC)感知和转导动态平衡调节心脏的信号 肌细胞。心肌细胞在钙信号转导到细胞核方面是一个难题。胞浆型病例 在每个心动周期中，幅度变化10倍，但钙的变化以某种方式被差异化地解码 以获得更长期的转录信号。在这一资助期间，我们将测试钙通道活动和 心脏L型钙通道本身编码钙信号，对钙信号进行长期调节。在过去的资助期，我们 发现RGK对ICa有慢性抑制作用，L(LTCC电流)，而这种RGK对ICa的抑制作用，导致L 代偿性上调CaV1.2基因的表达。这提示ICA、L阻断可能是转录事件的信号传导途径。 在原子核中。在新的研究中，我们证实并扩展了这一概念，表明LTCC-药理- 阻碍心脏发育的通常是体内的钙，而不是体内的钙。沿着同样的路线，在 成熟的心脏，长期阻断LTCC也会导致LTCC和ICA的代偿性上调。 驱动假说认为，信号不是简单地由钙决定的，而是由活跃的钙通道决定的。这一发现 LTCC的活动部分定位于核或T管，加上最近的报告说，这 多肽是一种转录因子，推动了令人兴奋的新假说，即LTCC的这一片段，调节 LTCC表达式。我们将从三个方面研究长期渠道监管：1.我们将评估 LTCC一个结构域的核移位，并确定LTCC活性与亚基之间的相互作用 细胞定位；2.我们将确定LTCC转录自我调节的能力；以及3.我们 将确定SL钙调节蛋白在LTCC阻断后的代偿性变化。这部作品 可能在LTCC功能和下游信号事件之间提供了缺失的分子链接。

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.