Myosin Light Chain Dephosphorylation by PPP1R12C Promotes Atrial Hypocontractility and Atrial Fibrillation

项目摘要/摘要 血栓栓塞性中风是房颤(房颤)的主要死亡原因。当前的预防战略 房颤诱发的卒中，如口服抗凝药物，具有显著的风险，且不能完全抑制卒中。心房 房颤患者的收缩能力显著降低，并导致卒中风险；然而，对这一问题的理解并不完整 调节肌节功能的机制阻碍了靶向治疗方法的发展 心房收缩功能障碍。来自我们实验室和其他实验室的最新见解表明，次要的- 心房肌球蛋白轻链(MLC2a)的磷酸化是导致心房收缩功能障碍的主要因素 自动对焦。此外，我们还证明了蛋白磷酸酶1调节亚基12C(PPP1R12C) 参与房颤时MLC2a去磷酸化和心房收缩功能减退。这个项目的长期目标是 确定蛋白磷酸酶调节和催化亚基调节MLC2a的机制 磷酸化和肌丝钙敏感性，并确定如何减少MLC2a磷酸化 导致心房收缩功能减退、房颤易感性和中风。此应用程序的目标是 PPP1R12C蛋白表达和活性作为心房钙敏感性和心房调节因子的评价 体内的收缩能力。鉴于我们已经证明PPP1R12C蛋白表达增加与 人房颤患者和小鼠房颤模型中MLC2a去磷酸化及其调控机制 PPP1R12C的表达仍然未知。此外，PPP1R12C缺失或缺失的功能意义 药理上的PPP1R12C抑制作用仍未得到测试。中心假设是存在一个相反的情况 PPP1R12C活性与心房收缩性能关系及抑制PPP1R12C表达的研究 房颤时，活动会增加心房的收缩能力。为了验证这一假设，提出了三个具体目标：目标1-- 确定Angii信号增加PPP1R12C表达的机制；目的2-评估 小鼠Ppp1r12c基因敲除是否增加心房收缩能力；目标3--验证药理学 体内修饰PPP1R12C活性的方法。我们项目的创新之处在于我们正在评估 心房收缩功能低下，这是Virchow三联症中唯一未用于预防房颤卒中的肢体。建议数 该项目将首次尝试干预心房收缩底物，并修改心房 活体心肌病。完成拟议目标后，我们预期会有更好的结果。 房颤患者心房收缩功能障碍机制的了解及靶点的验证 增加房颤患者的心房收缩能力，降低卒中风险。

Project Summary / Abstract Thromboembolic stroke is a leading cause of death from atrial fibrillation (AF). Current strategies to prevent AF-induced stroke, such as oral anticoagulants, have significant risks and incompletely suppress stroke. Atrial contractility is significantly reduced in AF and contributes to stroke risk; however, an incomplete understanding of mechanisms regulating sarcomere function has hindered development of therapeutic approaches targeting atrial contractile dysfunction. Recent insights from our lab and others have demonstrated that hypo- phosphorylation of atrial myosin light chain (MLC2a) is a major contributor to atrial contractile dysfunction in AF. Furthermore, we have demonstrated that the protein phosphatase 1 regulatory subunit 12C (PPP1R12C) contributes to MLC2a dephosphorylation and atrial hypocontractility in AF. The long-term goal of this project is to determine the mechanisms by which protein phosphatase regulatory and catalytic subunits regulate MLC2a phosphorylation and myofilament Ca2+ sensitivity, and determine how reduced MLC2a phosphorylation contributes to atrial hypocontractility, AF susceptibility, and stroke. The objective of this application is to evaluate PPP1R12C protein expression and activity as a regulator of atrial Ca2+ sensitivity and atrial contractility in vivo. Whereas we have shown that increased PPP1R12C protein expression is associated with MLC2a dephosphorylation in human AF patients and mouse models of AF, the mechanisms regulating PPP1R12C expression remain unknown. Furthermore, the functional significance of PPP1R12C deletion or pharmacologic PPP1R12C inhibition remain untested. The central hypothesis is that there is an inverse relationship between PPP1R12C activity and atrial contractility, and that inhibition of PPP1R12C expression or activity will increase atrial contractility in AF. To test this hypothesis, three Specific Aims are proposed: Aim 1- To determine the mechanism whereby AngII signaling increases PPP1R12C expression; Aim 2- To assess whether genetic knockout of Ppp1r12c in mice increases atrial contractility; Aim 3 - To validate pharmacologic approaches to modifying PPP1R12C activity in vivo. The innovation of our project is that we are evaluating atrial hypocontractility, the only limb of Virchow's triad unaddressed for stroke prevention in AF. The proposed project would, for the first time, attempt to intervene upon the atrial contractile substrate and modify atrial cardiomyopathy in vivo. Our expected outcome from completion of the proposed Aims is an enhanced understanding of the mechanisms underlying atrial contractile dysfunction in AF, and validation of targets to increase atrial contractility and reduce stroke risk in AF.