SARCOPLASMIC RETICULUM FUNCTION IN NORMAL AND FAILING HEARTS

在心脏兴奋-收缩偶联中，肌浆网（SR）在调节胞浆游离Ca ~（2+）浓度中起着重要作用。SR有三个主要功能：a）从胞质溶胶到SR腔的Ca 2+摄取，导致肌肉松弛; B）SR腔中的Ca 2+储存;以及c）这些功能分别是：Ca 2+转运ATP酶（SERCA 2）、Ca 2+储存蛋白钙螯合蛋白和Ca 2+释放通道或ryanodine受体。受磷蛋白（PLB）是另一种SR蛋白，其在Ca 2 +-ATP酶活性和心肌收缩性的调节中起关键作用。在该项目中，我们提出进一步研究阐明PLB在哺乳动物心脏中的调节作用，并定义PLB和Ca 2+泵之间的化学计量偶联比，这似乎是心脏收缩参数的关键决定因素。我们还建议阐明PLB磷酸化状态的作用，通过调节其磷酸酶活性的抑制剂-1，在基础和β-激动剂条件下的收缩控制。此外，我们建议将我们的研究扩展到临床竞技场，并且：a）筛选患有心力衰竭的患者在PLB和SR Ca 2 +-泵之间的相互作用区域中的点突变，其可以改变这两种蛋白质的相互作用的性质或程度，导致病理生理学后果;和B）评估人衰竭心脏中PL B和SR CA 2+泵的水平以及PL B磷酸化的程度。我们的研究将推进我们对正常和衰竭心脏中SR功能调节Ca 2+稳态的机制的认识。他们还将提供有价值的见解之间的串扰的各种SR钙处理蛋白质和它们对心肌收缩力的调节作用。

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) for these functions are: the Ca2+- transport ATPase (SERCA2), the Ca2+ storage protein calsequestrin and the Ca2+ release channel or ryanodine receptor, respectively. phospholamban (PLB) 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, we propose to extend our studies to the clinical arena and: a) screen patients with heart failure for point mutations in the areas of interaction between PLB and the SR Ca2+-pump, which may modify the nature or degree of interaction of these two proteins, resulting in pathophysiological consequences; and b) assess the levels of PLB and the SR CA2+ pump as well as the degree of PLB phosphorylation in human failing hearts. Our proposed studies will advance our knowledge on the mechanisms underlying regulation of Ca2+ homeostasis by the SR function in the normal and failing heart. They will also provide valuable insights into the crosstalk between the various SR Ca2+ handling proteins and their regulatory effects on cardiac contractility.