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

项目总结/摘要 血栓栓塞性卒中是房颤（AF）死亡的主要原因。目前的预防战略 AF诱发的卒中，如口服抗凝剂，具有显著的风险且不能完全抑制卒中。心房 房颤患者的收缩力显著降低，并导致卒中风险;然而， 调节肌节功能的机制阻碍了靶向治疗方法的发展 心房收缩功能障碍我们实验室和其他人的最新见解表明，hypo- 心房肌球蛋白轻链（MLC 2a）的磷酸化是心房收缩功能障碍的主要原因， AF.此外，我们已经证明，蛋白磷酸酶1调节亚基12 C（PPP 1 R12 C） 导致AF中MLC 2a去磷酸化和心房收缩功能减退。本项目的长期目标是 确定蛋白磷酸酶调节和催化亚基调节MLC 2a的机制 磷酸化和肌丝Ca 2+敏感性，并确定如何减少MLC 2a磷酸化 导致心房收缩功能减退、房颤易感性和卒中。本申请的目的是 评估PPP 1 R12 C蛋白表达和活性作为心房Ca 2+敏感性和心房肌钙蛋白依赖性的调节剂。 体内收缩性。然而，我们已经表明PPP 1 R12 C蛋白表达的增加与 人AF患者和AF小鼠模型中MLC 2a去磷酸化，调节机制 PPP 1 R12 C的表达仍然未知。此外，PPP 1 R12 C缺失或 药理学PPP 1 R12 C抑制仍然未测试。核心假设是， PPP 1 R12 C活性与心房收缩力关系，以及PPP 1 R12 C表达或 活动将增加AF的心房收缩力。为了检验这一假设，提出了三个具体目标：目标1- 确定AngII信号传导增加PPP 1 R12 C表达的机制;目的2-评估 小鼠中Ppp 1 r12 c基因敲除是否增加心房收缩力;目的3 -验证药理学 修饰PPP 1 R12 C体内活性的方法。我们项目的创新之处在于我们正在评估 心房收缩功能减退是Virchow三联征中唯一一个在预防AF卒中方面未得到解决的分支。 该项目将首次尝试干预心房收缩基质， 体内心肌病。我们预期完成拟议目标后， 了解AF中心房收缩功能障碍的潜在机制，并验证 增加心房收缩力并降低房颤患者中风风险。

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.