Modulation of Cardiac E-C Coupling by Sorcin

Sorcin 对心脏 E-C 耦合的调节

• 批准号: 6861092
• 负责人: Hector H Valdivia
• 金额: $ 36.14万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-01 至 2009-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6861092
• 关键词: calcium binding protein; calcium channel; genetically modified animals; heart; heart cell; heart electrical activity; laboratory mouse; mutant; myocardium; phosphorylation; protein protein interaction; protein structure; tissue /cell culture; transfection; voltage /patch clamp

DESCRIPTION (provided by applicant): Excitation-contraction (E-C) coupling is a Ca-dependent process in cardiac muscle. Depolarization of the surface membrane permits a small influx of Ca (the inward Ca current, ICa). ICa then evokes Ca release from the sarcoplasmic reticulum (SR), a process termed Ca-induced Ca release (CICR). The protein responsible for CICR is the Ca release channel/ryanodine receptor (RyR). Isolated RyRs are "eager Ca responders" that quickly open when (Ca) rises and remain open as long as (Ca) remains high. This willingness of RyRs to act as Ca indicators is surprising given that in cellular settings RyRs quickly close despite (Ca) being high, thereby avoiding SR Ca depletion and overflowing of cytosolic compartments with Ca. The mechanism(s) that allows RyR closure in vivo is unknown. This proposal will determine whether sorcin, a novel Ca-binding protein inhibitor of RyRs, is an important component of the mechanism that quenches CICR in intact cells. The specific aims are: 1) To establish the structural determinants of sorcin modulation of cardiac RyRs. We will determine the kinetics of sorcin interaction with RyRs and the role played by phosphorylation. Also, we will obtain sorcin mutants that are unable to bind Ca in one or several of its five E-F hands as well as sorcin mutants unable to undergo phosphorylation; of special interest is F112L-sorcin, a sorcin mutant associated with Familial Hypertrophic Cardiomyopathy and hypertension. 2) To determine the role of sorcin in regulation of Ca release and E-C coupling of cardiac cells. We will determine effects of sorcin in localized and global Ca release in intact and permeabilized cardiac myocytes. We will also determine the effects of overexpression and ablated expression of sorcin in ventricular cells. Finally, we will characterize a sorcin-null transgenic mouse.

描述（由申请人提供）：兴奋-收缩（E-C）耦合是心肌中的 Ca 依赖性过程。 表面膜的去极化允许少量 Ca 离子流入（内向 Ca 离子电流，ICa）。 ICa 然后引起肌浆网 (SR) 中的 Ca 释放，这一过程称为 Ca 诱导的 Ca 释放 (CICR)。 负责 CICR 的蛋白质是 Ca 释放通道/兰尼碱受体 (RyR)。 孤立的 RyR 是“热切的 Ca 反应器”，当 (Ca) 升高时，它们会迅速打开，并且只要 (Ca) 保持高水平，就会保持打开状态。 RyRs 充当 Ca 指示剂的意愿令人惊讶，因为在细胞环境中，尽管 (Ca) 较高，RyRs 仍会快速关闭，从而避免 SR Ca 耗尽和细胞质室中 Ca 溢出。 允许 RyR 在体内闭合的机制尚不清楚。 该提案将确定 sorcin（一种新型 RyRs 钙结合蛋白抑制剂）是否是完整细胞中猝灭 CICR 机制的重要组成部分。 具体目标是： 1) 确定 sorcin 调节心脏 RyR 的结构决定因素。 我们将确定 sorcin 与 RyR 相互作用的动力学以及磷酸化所起的作用。 此外，我们还将获得在其五个E-F手中的一只或多只中无法结合Ca的sorcin突变体以及无法进行磷酸化的sorcin突变体；特别感兴趣的是F112L-sorcin，一种与家族性肥厚性心肌病和高血压相关的sorcin突变体。 2)确定sorcin在调节心肌细胞Ca释放和E-C耦合中的作用。 我们将确定 sorcin 对完整和透化心肌细胞局部和整体 Ca 释放的影响。 我们还将确定心室细胞中 sorcin 过度表达和消除表达的影响。 最后，我们将表征 sorcin 无效的转基因小鼠。