Regulation of the Cardiac Sodium Channel by SIRTUIN1

描述(由申请人提供)：心脏钠离子通道SCN5A(NaV1.5)和内向去极化钠电流(INA)在调节心房、心室和特殊传导系统的心肌细胞的动作电位方面起着关键作用。SCN5A基因突变与几种心律失常表型有关，包括长QT综合征、Brugada综合征和扩张型心肌病。Brugada综合征还与类似甘油-3-磷酸脱氢酶(GPD1-L)蛋白的基因突变有关，该蛋白依赖于细胞内NADH和NAD+的平衡，从而依赖于细胞的能量状态。SIRT1是一种哺乳动物蛋白赖氨酸脱乙酰酶，属于依赖NAD+的Sirtuin家族脱乙酰酶。SIRT1针对许多蛋白质进行赖氨酸去乙酰化，以响应细胞能量状态的变化。SIRT1是否针对心脏离子通道，特别是SCN5A，从而在调节心脏兴奋性方面发挥作用尚不清楚。此外，GPD1-L、心室肌细胞的代谢状态和SIRT1活性之间的潜在相互作用完全没有被探索。这一修订后的应用基于非常新的初步数据，即SIRT1与NaV1.5和GPD1-L相互作用调节Ina。它假设动态赖氨酸乙酰化和去乙酰化是先前未知的SCN5A的翻译后修饰，调节INA，依赖SIRT1的NaV1.5的脱乙酰基增加INA，GPD1-L突变通过SIRT介导的NaV1.5的脱乙酰基改变改变INA，并且SIRT1的变化可以改变心律失常的风险。它将使用HEK 293细胞、大鼠新生心肌细胞、iPS来源的心肌细胞和转基因小鼠来关键地检验这些假说。SIRT1通过脱乙酰基介导NAV1.5的激活，并被GPD1-L调控，这将为心脏INA的调节找到一种全新的机制。通过这样做，它将为药物SIRT1激动剂作为潜在的治疗药物打开大门，用于因心脏INA遗传和获得性障碍而导致心律失常的风险患者。

DESCRIPTION (provided by applicant): The cardiac Na+ channel SCN5A (Nav1.5) and the inward depolarizing Na+ current (INa) play a critical role in regulating the action potential of myocytes in the atrium, ventricle, and specialized conduction system. Mutations in SCN5A are associated with several arrhythmia phenotypes including long QT syndrome, Brugada syndrome, and dilated cardiomyopathy. Brugada Syndrome has also been linked to a mutation in the gene for the glycerol-3-phosphate dehydrogenase-like (GPD1-L) protein, which is dependent on the balance of cellular NADH and NAD+, and thus the energetic state of the cell. SIRT1 is a mammalian protein lysine deacetylase which belongs to the SIRTUIN family of NAD+-dependent deacetylases. SIRT1 targets many proteins for lysine deacetylation in response to changes in the energetic state of the cell. Whether SIRT1 targets cardiac ion channels, and SCN5A in particular, and thus plays a role in regulating cardiac excitability is not known. Moreover, potential interactions between GPD1-L, the metabolic state of ventricular myocytes, and SIRT1 activity are completely unexplored. This revised application is based on very novel preliminary data that SIRT1 interacts with Nav1.5 and GPD1-L to regulate INa. It hypothesizes that dynamic lysine acetylation and deacetylation is a previously undescribed post-translational modification of SCN5A that regulates INa, that SIRT1-dependent deacetylation of Nav1.5 increases INa, that GPD1-L mutations alter INa through changes in SIRT-mediated deacetylation of Nav1.5, and that changes in SIRT1 can modify arrhythmic risk. It will critically test these hypotheses using HEK 293 cells, rat neonatal cardiac myocytes, iPS-derived cardiac myocytes and transgenic mice. Deacetylation-mediated activation of Nav1.5 by SIRT1, and its modulation by GPD1-L, will identify an entirely new mechanism for regulation of cardiac INa. In doing so, it will open the door for pharmacologic SIRT1 activators as potential therapeutic agents in patients at risk for cardiac arrhythmias dues to inherited and acquired disturbances in cardiac INa.