Cardiac Sarcoplasmic Reticulum Calcium Cycling Proteins

描述（由申请人提供）：心力衰竭动物模型和人类心力衰竭中的钙循环抑制被认为至少部分反映了肌浆网（SR）钙循环受损。SR有三个主要功能：a)钙从细胞质吸收到SR管腔，导致肌肉松弛；b) SR腔内的钙储存；c)钙从SR释放到胞质中，导致肌肉收缩。负责这些功能的主要SR蛋白有：钙转运atp酶（SERCA2）及其调节因子磷蛋白（PLN）；钙储存蛋白、钙固蛋白和富含组氨酸的钙结合蛋白（HRC）；以及由ryanodine受体、连接素和triadin组成的ca释放集合。在这个项目中，我们建议进一步研究阐明PLN磷酸化增加（慢性或急性）的调节作用，通过抑制剂- 1调节其磷酸酶1活性，控制收缩力和心脏对应激的反应。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：a) SR钙通过钙螯合蛋白（SR管腔中主要的钙储存蛋白）负荷；b) SR - ca通过连接蛋白（释放盒中的主要蛋白之一）释放。将生成calsequestrin或连接蛋白表达减少或消失的动物模型，并在基础和应激条件下在分子、亚细胞、细胞、器官和完整动物水平上分析其心脏表型。这些研究将为钙栓蛋白和连接蛋白在体内生理和病理生理条件下的功能作用提供重要信息。总的来说，我们提出的研究将推进我们对哺乳动物心脏中SR功能调节Ca稳态的机制的认识。他们还将为各种SR Ca处理蛋白之间的串扰及其对心脏收缩性的调节作用提供有价值的见解。

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.