Molecular mechanism underlying the regulation and its failure of calcium signalosome in atrial myocytes.

最近的研究表明，L型钙通道功能受损与房颤等心律失常有关。为了阐明参与调节心房(钙信号体)L型钙通道的信号分子复合体，我们筛选了与CAV1.2羧基末端区域相关的蛋白质。我们发现Cav1.2的C末端区域与磷脂酰胆碱转移蛋白样蛋白(PCTP-USTARD10)相互作用。PCTP-L在胚胎全心中表达，在成人心脏中表达，在心房中表达，在心室中不表达。在大鼠心房肌细胞中，PCTP-L与Cav1.2共定位并免疫共沉淀。PCTP-L通过与Cav1.2的C-末端区域的特异性相互作用减弱了Cav1.2的电压依赖性失活。在本研究中，我们的发现如下：1)在心房肌细胞中，pCTP-L被RNA干扰后，动作电位时程缩短，SP-…频率增加。更多的同时动作电位以及钙离子瞬变。此外，在压力超负荷房颤模型大鼠的心房中，PCTP-L基因的表达水平显著降低。这些结果表明，PcTP-L参与了心房肌细胞兴奋性的调节。2)为了阐明Cav1.3的作用，我们将其与Cav1.2的电生理特性进行了比较。除了激活和失活对电压的依赖性较低外，与Cav1.2相比，Cav1.3还存在较慢的电压依赖失活(VDI)和较快的失活恢复。在SA结型起搏器动作电位(AP)电压钳下，Cav1.3电流在舒张期去极化时激活，复极化时重新激活，而Cav1.2电流在AR阈值时激活。在重复去极化下，Cav1.3保持了比Cav1.2更高的可用性。计算机模拟表明，Cav1.3缓慢的VDI和快速的恢复动力学有助于维持其在SA节点重复去极化下的可利用性。3)Cav1.2与PCTP-L之间的功能相互作用受到损害，因为Cav1.2的C末端区域被Cav1.3的可比区域所替代，从而表明PCTP-L与Cav1.2以一种亚型特异性的方式相互作用。4)为了阐明PCTP-L在L型心房肌钙通道周围信号体中的功能角色，我们建立了PCTP-L-KO小鼠。PCTP-L-KO小鼠的表型正在调查中。较少

Recent studies have shown that the impairment of L-type Ca^<2+> channel function is associated with arrhythmia such as atrial fibrillation. Aiming at clarifying the signaling molecular complex involved in the regulation of L-type Ca^<2+> channel in atria (calcium signalosome), we screened proteins associated with the carboxyl terminal region of Cav1.2. We found that the C-terminal region of Cav1.2 interacts with phosphatidylcholine transfer protein-like protein (PCTP-USTARD10). PCTP-L was expressed in embryonic whole heart and, in adult heart, in atria but not in ventricle. In rat atrial myocytes, PCTP-L colocalized and was coimmunoprecipitated with Cav1.2. PCTP-L attenuated the voltage-dependent inactivation of Cav1.2 through the specific interaction with the C-terminal region of Cav1.2. In the present study, our findings are as follows :1) The knockdown of PCTP-L by RNAi, in atrial myocytes, resulted in the shorteningof action potential duration and an increase in the frequency of sp … More ontaneous action potentials as well as Ca^<2+> transients. In addition, in atria of pressure-overloaded atrial fibrillation model rats, the mRNA expression level of PCTP-L was significantly reduced. These results suggest that PCTP-L is involved in the regulation of the excitability of atrial myocytes.2) To elucidate the role of Cav1.3, an atrial-specific subtype of L-type Ca^<2+> channels, we compared the electrophysiological properties with those of Cav1.2. In addition to lower voltage-dependence of activation and inactivation, Cav1.3 exibited slower voltage-dependent inactivation (VDI) and faster recovery from the inactivation compared to Cav1.2. Under voltage-clamp with SA nodal pacemaker action potential (AP) waveform, Cav1.3 current activated during diastolic depolarization and reactivated during repolarizing phase, while Cav1.2 current activated at the threshold of AR. Under repetitive depolarization, Cav1.3 maintained higher availability than Cav1.2. Computer simulation indicates that slow VDI and fast recovery kinetics of Cav1.3 contribute to maintain its availability under repetitive depolarizarion in SA node.3) The functional interaction between Cav1.2 and PCTP-L was impaired by replacing the C-terminal region of Cav1.2 by the comparable region of Cav1.3, thus indicating that PCTP-L interacts with Cav1.2 in a subtype-specific manner.4) ln order to clarify thefunctional role of PCTP-L in the Ca^<2+> signalosome surrounding the L-type Ca^<2+> channel in atria, we generated PCTP-L-KO mice. Phenotypes of PCTP-L-KO mice are under investigation. Less