A study on the mechanism of Na^+/Ca^<2+> exchange and its cellular role

Na^/Ca^2交换机制及其细胞作用的研究

• 批准号: 10470013
• 负责人: SHIGEKAWA Munekazu
• 金额: $ 2.5万
• 依托单位: National Cardiovascular Center Research Institute
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10470013/
• 关键词: Na^+; Ca^<2+> exchanger; Ca^<2+> exchange inhibitor; Ca^<2+> signaling; H^+ exchanger

We have recently developed the first selective inhibitor of Na^+/Ca^<2+> exchanger (NCX), KB-R7943, that has a therapeutic potential for clinical use. In this study, we have analyzed the topology of the cardiac NCX molecule as well as interactions of NCX with the transport substrate Ca^<2+>, KB-R7943, a nonselective inhibitor Ni^<2+>, and an activator Li^+. Based on detailed analysis by cysteine scanning and site-directed mutagenesis, we found that the highly conserved α-1 and α-2 repeat regions in NCX is involved in interactions with these inhibitors and ligands, suggesting that these regions participate in the formation of ion transport pathway in NCX.This study have also provided evidence that NCX consists of 9 transmembrane segments, with regions containing α-1 and α-2 repeats forming re-entrant membrane loops originating from the opposite sides of the membrane. On the other hand, Na^+/H^+ exchanger (NHE) is an excellent target for the study of cellular signal transduction, because it is extensively regulated by a variety of extracellular signals. We have recently analyzed interactions of calmodulin (CaM) and the calcineurin-homologous protein CHP with various NHE isoforms, and found that CaM is involved in Ca^<2+>-induced activation of NHE1, whereas CHP is an essential cofactor to support physiological activity of multiple NHE isoforms. We also analyzed membrane topology of NHE1, and found that NHE1 comprises 12 transmembrane segments with N- and C- termini in thcytosol.

我们最近开发了第一个选择性的Na~(++)/Ca~(2+)交换(NCX)抑制剂KB-R7943，具有临床治疗潜力。在这项研究中，我们分析了心脏NCX分子的拓扑结构以及NCX与转运底物Ca^&lt；2+&gt；、KB-R7943、非选择性抑制剂Ni^&lt；2+&gt；和激活剂Li^+的相互作用。基于半胱氨酸扫描和定点突变的详细分析，我们发现NCX中高度保守的α-1和α-2重复区域参与了与这些抑制剂和配体的相互作用，表明这些区域参与了NCX离子转运途径的形成。本研究还提供了NCX由9个跨膜片段组成的证据，其中包含α-1和α-2重复区域的区域形成了起源于膜两侧的可重入膜环。另一方面，Na~+/H~+交换器(NHE)受到多种细胞外信号的广泛调控，是研究细胞信号转导的良好靶点。我们最近分析了钙调素(CaM)和钙调神经磷酸酶同源蛋白CHP与各种NHE亚型的相互作用，发现CaM参与了钙离子诱导的NHE1的激活，而CHP是支持多种NHE亚型生理活性的重要辅助因子。我们还分析了NHE1的膜拓扑结构，发现NHE1由12个跨膜片段组成，在胞浆中有N-末端和C-末端。

项目成果

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