CARDIAC SARCOPLASMIC RETICULIM CALCIUM CYCLING PROTEINS

心肌质网钙循环蛋白

• 批准号: 6718642
• 负责人: Evangelia G Kranias
• 金额: $ 4.45万
• 依托单位: UNIVERSITY OF CINCINNATI
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-02-01 至 2005-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6718642
• 关键词: calcium binding protein; calcium channel; calcium flux; calcium transporting ATPase; genetically modified animals; heart contraction; heart metabolism; laboratory mouse; neuromuscular transmission; phospholamban; sarcoplasmic reticulum; stoichiometry

In cardiac excitation-contraction coupling, the sarcoplasmic reticulum (SR) plays an essential role in the regulation of the cytosolic free Ca2+ concentration. There are three major functions of the SR: a) Ca2+-uptake from the cytosol into the SR lumen resulting in muscle relaxation; b) Ca2+ storage in the SR lumen; and c) Ca2+-release from the SR into the cytosol resulting in muscle contraction. The main SR proteins responsible for these functions are: the Ca2+-transport ATPase (SERCA), the Ca2+ storage protein calsequestrin, and the Ca2+ release channel or ryanodine receptor, respectively. Phospholamban is another SR protein, which plays a crucial role in the regulation of the Ca2+-ATPase activity and myocardial contractility. In this project, we propose further studies on elucidating the regulatory role of PLB in the mammalian heart and defining the stoichiometric coupling ratio between PLB and the Ca2+-pump, which appears to be a key determinant of cardiac contractile parameters. We also propose to elucidate the role of the PLB phosphorylation status, through regulation of its phosphatase activity by inhibitor 1, in the control of contractility under basal and beta-agonist conditions. Furthermore, since alterations in the levels of PLB or in the degree of PLB phosphorylation reflect alterations in SR Ca2+ load and contractility, we propose to elucidate the functional role of SR Ca2+ load through calsequestrin, the major Ca2+ storage protein in the SR lumen. Animal models with alterations in the expression levels of this protein (overexpression and knockouts) will be generated and their cardiac phenotype will be analyzed at the subcellular, cellular, organ and intact animal levels. These studies will provide important information on the physiological role of calsequestrin in vivo. Overall, our proposed studies will advance our knowledge on the mechanisms underlying regulation of Ca2+ homeostasis by the SR function. They will also provide valuable insights into the crosstalk between the various SR Ca2+ handling proteins and their regulatory effects on cardiac contractility.

在心脏兴奋-收缩耦合中，肌浆网 (SR) 在调节胞质游离 Ca2+ 浓度中起着重要作用。 SR 具有三个主要功能： a) 将 Ca2+ 从细胞质摄取到 SR 腔中，导致肌肉松弛； b) SR 腔内的 Ca2+ 储存； c) Ca2+ 从 SR 释放到细胞质中，导致肌肉收缩。 负责这些功能的主要 SR 蛋白分别是：Ca2+ 转运 ATP 酶 (SERCA)、Ca2+ 储存蛋白 calsequestrin 和 Ca2+ 释放通道或兰尼碱受体。 Phospholamban 是另一种 SR 蛋白，在 Ca2+-ATPase 活性和心肌收缩力的调节中起着至关重要的作用。 在这个项目中，我们建议进一步研究阐明 PLB 在哺乳动物心脏中的调节作用，并定义 PLB 和 Ca2+ 泵之间的化学计量耦合比，这似乎是心脏收缩参数的关键决定因素。 我们还建议通过抑制剂 1 调节 PLB 磷酸酶活性来阐明 PLB 磷酸化状态在基础和 β 激动剂条件下控制收缩性中的作用。 此外，由于 PLB 水平或 PLB 磷酸化程度的变化反映了 SR Ca2+ 负荷和收缩性的变化，因此我们建议通过 SR 腔中主要 Ca2+ 储存蛋白 calsequestrin 来阐明 SR Ca2+ 负荷的功能作用。 将生成该蛋白质表达水平发生改变（过度表达和敲除）的动物模型，并在亚细胞、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 calsequestrin 在体内的生理作用提供重要信息。 总体而言，我们提出的研究将增进我们对 SR 功能调节 Ca2+ 稳态的潜在机制的了解。 他们还将为各种 SR Ca2+ 处理蛋白之间的串扰及其对心脏收缩力的调节作用提供有价值的见解。