Physiological roles of junctional membrane complex formed by Ca^<2+> store and plasma membranes in excitation-contraction coupling of cardiac myocytes.

Ca ^ 2 库与质膜形成的连接膜复合物在心肌细胞兴奋-收缩耦合中的生理作用。

• 批准号: 16590171
• 负责人: UEHARA Akira
• 金额: $ 2.3万
• 依托单位: Fukuoka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16590171/
• 关键词: Physiology; Heart; Cardiomyocyte; Excitation-contraction coupling; Ca^<2+>; Sarcoplasmic reticulum; Junctophilin; Ryanodine receptor; Caストア; Ca

In heart muscle cells, sarcoplasmic reticulum (SR) membranes function as the intracellular Ca^<2+> store. The SR membranes form a junctional membrane complex with cell surface membrane by juctophilins of SR proteins. In this study, we explored the functional roles of junctional membrane complex composed of SR and sarcolemmal membranes in the excitation-contraction coupling.Utilizing the junctophilin knockout mice, we thus conducted the following experiments. (1)An abnormal contractility induced by the knockout of juctophilins was obserbed and characterized in detail. The abnormal contractility was considered to be due to disorganized structures of junctional membrane complex. (2)The action potentials were measured from the mouse heart. The abnormal contractility by the knockout of juctophilins was ascribed to the alteration in the action potential configuration. (3)Myoplasmic Ca^<2+> was measured from the mouse heart. The abnormal contractility by the knockout of juctophilins was media … More ted by the influx of the extracellular Ca^<2+> into the myoplasm. (4)During the abnormal contraction by the knockout of juctophilins, Ca^<2+> waves moving around the myocytes were detected with the confocal laser microscopy. (5)L-type Ca^<2+> channel and ryanodine receptor are strucurally coupled with each other. The coupling ratio of the L-type Ca^<2+> channel and the ryanodine receptor, calculated from the whole-cell current data, was decreased by the knockout of juctophilins. (6)Many parameters of cardiovascular system were studied at the animal level. Wave forms of the electrocardiogram (ECG) were altered by the knockout of juctophilins.The cardiac SR membranes express not only juctophilins but also ryanodine receptors. The ryanodine receptors function as Ca^<2+>-induced Ca^<2+> release channels from the Ca^<2+> store in the SR membranes to trigger the heart muscle contraction. Therefore, we also conducted experiments mentioned above using the ryanodine receptor knockout mice. This ryanodine receptor knockout mice showed an abnormal contractility, which was, different from that of the junctophilin knockout animal.Taken together, the present data strongly suggest that the junctional membrane complex containing junctophilins and ryanodine receptors is essential to the excitation-contraction coupling. Intact expression of both junctophilins and ryanodine receptors in the SR membrane would be important for the normal heart contraction. Less

在心肌细胞中，肌浆网(SR)膜起到细胞内Ca 2+ 储存的作用。 SR膜通过SR蛋白的亲乳素与细胞表面膜形成连接膜复合物。在本研究中，我们探讨了SR和肌膜膜组成的连接膜复合物在兴奋-收缩耦合中的功能作用。利用junctophilin敲除小鼠，我们进行了以下实验。 (1)对亲乳素敲除引起的异常收缩性进行了详细观察和表征。异常的收缩性被认为是由于连接膜复合体的结构紊乱造成的。 (2)从小鼠心脏测量动作电位。亲乳蛋白敲除导致的异常收缩性归因于动作电位构型的改变。 (3)从小鼠心脏测量肌质Ca 2+ 。亲乳糖蛋白敲除导致的异常收缩性是由细胞外 Ca^2+ 流入肌质引起的。 (4)在亲乳蛋白敲除引起的异常收缩过程中，用共聚焦激光显微镜检测到在肌细胞周围移动的Ca ^ 2+ 波。 (5)L型Ca 2+ 通道和兰尼碱受体在结构上彼此偶联。由全细胞电流数据计算的L-型Ca 2+ 通道和兰尼碱受体的偶联比因亲乳蛋白的敲除而降低。 (6)在动物水平上研究了心血管系统的许多参数。心电图 (ECG) 的波形因亲乳素的敲除而改变。心脏 SR 膜不仅表达亲乳素，还表达兰尼碱受体。兰尼碱受体充当Ca ^ 2+ 诱导的Ca ^ 2+ 释放通道，从SR膜中的Ca ^ 2+ 库释放，以触发心肌收缩。因此，我们也利用兰尼碱受体敲除小鼠进行了上述实验。这种兰尼碱受体基因敲除小鼠表现出异常的收缩性，这与亲细胞素基因敲除动物不同。总之，目前的数据强烈表明，含有亲细胞素和兰尼碱受体的连接膜复合物对于兴奋-收缩耦合至关重要。 SR 膜中亲结蛋白和兰尼碱受体的完整表达对于正常的心脏收缩非常重要。较少的