Regulation of the Cardiac Sodium Channel by SIRTUIN1

描述（申请人提供）：心脏Na+通道SCN5A （Nav1.5）和向内去极化Na+电流（INa）在调节心房、心室和特化传导系统的肌细胞动作电位中起关键作用。SCN5A突变与多种心律失常表型相关，包括长QT综合征、Brugada综合征和扩张型心肌病。Brugada综合征还与甘油-3-磷酸脱氢酶样（GPD1-L）蛋白基因突变有关，该蛋白依赖于细胞内NADH和NAD+的平衡，从而影响细胞的能量状态。SIRT1是一种哺乳动物蛋白赖氨酸脱乙酰酶，属于NAD+依赖性脱乙酰酶SIRTUIN家族。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是否靶向心脏离子通道，尤其是SCN5A，从而在调节心脏兴奋性中发挥作用尚不清楚。此外，GPD1-L、心室肌细胞代谢状态和SIRT1活性之间的潜在相互作用完全未被探索。这个修订后的应用是基于非常新颖的初步数据，SIRT1与Nav1.5和GPD1-L相互作用来调节INa。它假设动态赖氨酸乙酰化和去乙酰化是先前描述的调节INa的SCN5A翻译后修饰，SIRT1依赖的Nav1.5去乙酰化增加了INa， GPD1-L突变通过改变sirt介导的Nav1.5去乙酰化改变了INa， SIRT1的改变可以改变心律不调的风险。它将使用HEK 293细胞、大鼠新生心肌细胞、ips衍生心肌细胞和转基因小鼠对这些假设进行严格测试。去乙酰化介导的SIRT1对Nav1.5的激活，以及GPD1-L对其的调节，将确定一种全新的心脏INa调节机制。在此过程中，它将打开药理学SIRT1激活剂作为潜在治疗药物的大门，用于因遗传性和获得性心脏INa紊乱而有心律失常风险的患者。

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.