The myosin light chain regulators of heart function

摘要 肌球蛋白必需轻链（ELC）和调节轻链（RLC）在心肌收缩中起重要作用， 但它们在调节肌球蛋白运动功能中的具体作用还不清楚。科学的前提是 本申请涉及调节肌球蛋白运动功能的两种肌球蛋白轻链（MLC）调节剂的作用 在体内和体外：（1）心脏ELC的长N-末端（N-ELC），和（2）心肌肌球蛋白RLC磷酸化 （P-RLC）。沿着N-末端截短的ELC-Δ43的心肌病小鼠模型（HCM、RCM和DCM） 将对小鼠进行研究，以充分理解这两种肌球蛋白调节剂在控制心脏运动中的作用模式。 健康和疾病中的肌肉收缩。这里讨论的研究问题是N-ELC和P-RLC如何工作， 分子、肌丝和整个心脏水平？我们的中心假设是MLC调节器的功能是 分子和/或能量触发器控制肌球蛋白的动力冲程，ATP利用和力的产生， 心肌 目的1：N-ELC和P-RLC在不同条件下肌球蛋白运动功能调节中的作用 心肌病模型。这一目标将集中在心脏的分子触发器和MLC调节器 肌球蛋白分子水平的重塑。假设：N-ELC使用步长和步长的新机制， 频率调制以控制心肌肌球蛋白功率输出并促进肌动蛋白-肌球蛋白相互作用， 过程由P-RLC调节。我们将研究HCM/RCM/DCM/Δ43突变是否以及如何在MLC中表达。 调节肌球蛋白ATP周转率，并影响心脏的超松弛（SRX）参与松弛（DRX）平衡。 目的2：询问MLC调节的肌球蛋白运动功能和血液动力学、运动和 心脏的免疫反应。Aim 1和MLC依赖性改变的机制研究 肌球蛋白运动功能将与心脏的血液动力学、收缩和能量反应相结合 in vivo.假设：HCM，RCM，DCM和Δ43心脏对ATP的需求不同，以维持其功能。 在体内的血液动力学和收缩功能，从而不同地影响线粒体生物能量学。 目的3：评估肌球蛋白RLC和ELC的磷酸化作为减轻 HCM、RCM和DCM的病理学心脏SRX作为心脏能量利用的调节器， 参与降低代谢率（负荷），在这两个，正常功能的心肌，并在时间 压力，例如心肌病。假设：肌球蛋白RLC的磷酸化，可能还有ELC，可能在 在心肌病中的保护作用，涉及SRX状态和磷酸化的改变， 超弛豫（SRX）参与无序弛豫（DRX）平衡向DRX状态的诱导移位，其中 肌球蛋白头可以容易地与细丝相互作用并产生力。

ABSTRACT The myosin essential (ELC) and regulatory (RLC) light chains play important roles in cardiac muscle contraction, yet their specific roles in regulating myosin motor function are not well understood. The scientific premise of this application regards the role of two myosin light chain (MLC) regulators that modulate myosin motor function in vivo and in vitro: (1) the long N-terminus of cardiac ELC (N-ELC), and (2) cardiac myosin RLC phosphorylation (P-RLC). Mouse models of cardiomyopathy (HCM, RCM and DCM) along with N-terminally truncated ELC-Δ43 mice will be studied to fully comprehend the mode of action of these two myosin regulators in controlling cardiac muscle contraction in health and disease. The study question addressed here is how N-ELC and P-RLC work at the molecular, myofilament and whole heart levels? Our central hypothesis is that MLC regulators function as molecular and/or energetic triggers controlling myosin’s power stroke, ATP utilization and force production in cardiac muscle. AIM 1: THE ROLE OF N-ELC AND P-RLC IN THE REGULATION OF MYOSIN MOTOR FUNCTION IN DIFFERENT MODELS OF CARDIOMYOPATHY. This aim will focus on the molecular triggers and MLC regulators of heart remodeling at the level of myosin molecules. Hypothesis: N-ELC uses a novel mechanism of step-size and step- frequency modulation to control cardiac myosin power output and facilitate actin-myosin interaction, and this process is regulated by P-RLC. We will investigate whether and how HCM/RCM/DCM/Δ43 mutations in MLC regulate myosin ATP-turnover rates and affect the super-relaxed (SRX)↔ relaxed (DRX) equilibrium in the heart. AIM 2: INTERROGATE MLC-REGULATED MYOSIN MOTOR FUNCTION AND HEMODYNAMIC, CONTRACTILE AND ENERGETIC RESPONSES OF THE HEART. Mechanistic studies of Aim 1 and MLC-dependent alterations in myosin motor function will be integrated with the hemodynamic, contractile and energetic responses of the heart in vivo. Hypothesis: HCM, RCM, DCM and Δ43 hearts exhibit different demands for ATP to sustain their hemodynamic and contractile functions in vivo, thus differently affecting mitochondrial bioenergetics. AIM 3: ASSESS PHOSPHORYLATION OF MYOSIN RLC AND ELC AS A MOLECULAR MECHANISM TO MITIGATE THE PATHOLOGY OF HCM, RCM AND DCM. The cardiac SRX serves as a modulator of cardiac energy utilization, involved in decreasing metabolic rate (load) in both, the normally functioning myocardium and during times of stress, e.g. cardiomyopathy. Hypothesis: Phosphorylation of myosin RLC, and possibly ELC, play a potential protective role in cardiomyopathy disease that involve alterations of the SRX state and the phosphorylation- induced shift in the super-relaxed (SRX) ↔ disordered relaxed (DRX) equilibrium toward the DRX state in which myosin heads can readily interact with thin filaments and produce force.