Development of a new drug for heart failure

心肌的收缩和舒张是由细胞内钙离子（Ca）调节的。其中，钙泵（SERCA）和心脏肌浆网（SR）的钙释放通道在这些过程中起着关键作用。心肌SERCA受另一种SR蛋白磷蛋白调控，其抑制SERCA的活性。去除磷蛋白的抑制作用，有利于心肌松弛，增加收缩力。研究表明，去除磷蛋白抑制可改善心力衰竭。为了开发一种新的心力衰竭药物，我们研究了SERCA和磷蛋白之间的分子相互作用以及调节这种相互作用的因素。以下是我们研究结果的摘要。基于SERCA-磷蛋白系统的药物筛选方法的开发利用SERCA-磷蛋白细胞质区域的融合蛋白重构了SERCA和磷蛋白之间的分子相互作用。通过优化384孔板的条件，我们成功地开发了一种针对serca -磷蛋白系统的阻力筛选方法2。由于磷蛋白只有单体形式而不是五聚体形式抑制SERCA，因此了解这两种形式之间的动态平衡是很重要的。增加单体形式解离低聚物的因素可能潜在地影响心肌的收缩性。在所检测的八种磷脂中，磷脂酸是五聚体解离的有效诱导剂，而其他磷脂则表现出五聚体稳定活性。溶血磷脂酰胆碱、溶血磷脂酰乙醇胺和磷脂酰甘油是五聚体的高效稳定剂。因此，SR膜中的磷脂是该蛋白单体和五聚体形式之间平衡的重要决定因素。我们的研究结果表明，一种直接或间接通过磷脂酶D增加磷蛋白五聚体形式的药物可能改善心肌功能。少

Contraction and relaxation of heart muscle is regulated by intracellular calcium ions (Ca). Especially, Ca pumps (SERCA) and Ca release channels of cardiac sarcoplasmic reticulum (SR) play pivotal roles in these processes. SERCA of heart muscle is modulated by another SR protein phospholamban which inhibits the activity of SERCA. Removal of the inhibition by phospholamban facilitates relaxation of heart muscle and increases the contractility. It has been shown that removal of phospholamban inhibition improves heart failure. In order to develop a new drug for heart failure, we investigated the molecular interaction between SERCA and phospholamban and factors that modulate the interaction. The followings are the summary of our results.1.Development of a screening method for a drug which targets the SERCA-phospholamban systemWe reconstituted the molecular interaction between SERCA and phospholamban using fusion proteins of cytoplasmic regions of each protein. Optimizing the conditions for … More a 384-well plate, we succeeded in development of a screen method for a drag which targets the SERCA-phospholamban system2.Searching for factors which modulate oligomeric structure of phospholambanSince only the monomeric form, not a pentameric form, of phospholamban inhibits SERCA, it is important to gain insight into the dynamic equilibrium between these two forms. Factors that increase the monomeric form dissociating the oligomer can potentially affect the contractility of heart muscle. Among the eight phospholipids examined, phosphatidic acid was an effective inducer of pentamer dissociation, whereas the other phospholipids exhibited pentamer-stabilizing activity. Lysophosphatidylcholine, lysophosphatidylethanolamine, and phosphatidylglycerol were highly effective stabilizers of the pentamer. The phospholipids in the SR membrane are thus important determinants of the equilibrium between the monomeric and pentameric forms of this protein. Our results suggest that a drug that directly or indirectry through phospholipase D increases the pentameric form of phospholamban potentially improves heart muscle function. Less