Cardiac Sarcoplasmic Reticulum Calcium Cycling Proteins

描述(申请人提供)：在心力衰竭和人类心力衰竭的动物模型中，钙循环的抑制至少部分地反映了肌浆网(SR)对钙循环的损害。SR有三个主要功能：a)胞浆中的钙摄取到SR腔内，导致肌肉松弛；b)SR腔内的钙储存；c)SR中的Ca释放到胞浆中，导致肌肉收缩。负责这些功能的主要SR蛋白是：钙转运ATPase(SERCA2)及其调节因子磷蛋白(PLN)；钙储存蛋白、钙库蛋白和富含组氨酸的钙结合蛋白(HRC)；以及由兰诺定受体、连接素和Triadin组成的钙释放系统。在这个项目中，我们建议进一步研究PLN磷酸化增加(慢性或急性)，通过抑制物-I调节其磷酸酶1的活性，在控制收缩能力和心脏对应激的反应中发挥调节作用。此外，由于PLN磷酸化程度的改变反映了SR钙负荷和释放的变化，我们建议阐明以下功能：a)通过SR腔中主要的钙储存蛋白Calequestrin来装载SR Ca；b)通过释放盒中的主要蛋白质之一Junctin来释放SR Ca。在基础和应激条件下，将建立钙调素或连接素表达减少或消融的动物模型，并在分子、亚细胞、细胞、器官和完整动物水平上分析其心脏表型。这些研究将为钙调素和连接素在生理和病理生理条件下在体内的功能作用提供重要的信息。总体而言，我们提出的研究将促进我们对哺乳动物心脏SR功能调节钙稳态的潜在机制的了解。他们还将提供有价值的见解，以了解不同的SR钙处理蛋白之间的串扰及其对心脏收缩能力的调节作用。

DESCRIPTION (provided by applicant): The depressed Ca-cycling in animal models of heart failure and human failing hearts has been suggested to reflect, at least in part, the impaired Ca-cycling by the sarcoplasmic reticulum (SR). There are three major functions of the SR: a) Ca-uptake from the cytosol into the SR lumen resulting in muscle relaxation; b) Ca-storage in the SR lumen; and c) Ca-release from the SR into the cytosol resulting in muscle contraction. The main SR proteins responsible for these functions are: the Ca-transport ATPase (SERCA2) with its regulator phospholamban (PLN); the Ca-storage proteins, calsequestrin and a histidine rich Ca-binding protein (HRC); and the Ca-release ensemble composed of the ryanodine receptor, junctin and triadin. In this project, we propose further studies on elucidating the regulatory role of increased (chronic or acute) PLN phosphorylation, through regulation of its phosphatase 1 activity by Inhibitor-I, in the control of contractility and the heart's responses to stress. Furthermore, since alterations in the degree of PLN phosphorylation reflect alterations in SR Ca-load and release, we propose to elucidate the functional roles of: a) SR Ca load through calsequestrin, the major Ca storage protein in the SR lumen; and b) SR Ca-release through junctin, one of the major proteins in the release cassette. Animal models with reduced or ablated expression of calsequestrin or junctin will be generated and their cardiac phenotypes will be analyzed at the molecular, subcellular, cellular, organ and intact animal levels under basal and stress conditions. These studies will provide important information on the functional role of calsequestrin and junctin in vivo under physiological and pathophysiological conditions. Overall, our proposed studies will advance our knowledge on the mechanisms underlying regulation of Ca homeostasis by the SR function in the mammalian heart. They will also provide valuable insights into the crosstalk between the various SR Ca handling proteins and their regulatory effects on cardiac contractility.