Role of phosphorylation in cardiac muscle myosin

了解心肌肌球蛋白调节轻链（RLC）磷酸化如何改变心肌力学是很重要的，因为它在心脏病中经常发生改变。在心脏产生能量和工作的生理速度缩短范围内，这种蛋白质磷酸化对肌肉力学的影响尚未得到解决。我们表达并磷酸化了重组褐家鼠左心室RLC。在体外，我们用心肌肌球蛋白轻链激酶和拉链相互作用蛋白激酶磷酸化了这些重组物种。我们比较了与不同磷酸化RLC物种进行交换的大鼠心脏小梁通透性。与对照组相比，我们能够使小梁RLC磷酸化增加40%，并且在单独的系列中，RLC磷酸化降低到控制值的60%。与RLC磷酸化水平较低的小梁相比，RLC磷酸化富集使小梁的等长力增加了3倍以上，峰值输出功率增加了7倍以上，最大缩短速度和产生峰值功率的缩短速度都增加了约一倍。我们通过观察心内膜左心室匀浆中人类和大鼠HF样品的RLC磷酸化增加来增强这些测量。这些结果证明了RLC磷酸化增加在心肌功能上调中的重要性，并表明RLC磷酸化降低是病变心肌收缩功能受损的一个关键方面。

Understanding how cardiac myosin regulatory light chain (RLC) phosphorylation alters cardiac muscle mechanics is important because it is often altered in cardiac disease. The effect this protein phosphorylation has on muscle mechanics during a physiological range of shortening velocities, during which the heart generates power and performs work, has not been addressed. We have expressed and phosphorylated recombinant Rattus norvegicus left ventricular RLC. In vitro we have phosphorylated these recombinant species with cardiac myosin light chain kinase and zipper-interacting protein kinase. We compare rat permeabilized cardiac trabeculae, which have undergone exchange with differently phosphorylated RLC species. We were able to enrich trabecular RLC phosphorylation by 40% compared with controls and, in a separate series, lower RLC phosphorylation to 60% of control values. Compared with the trabeculae with a low level of RLC phosphorylation, RLC phosphorylation enrichment increased isometric force by more than 3-fold and peak power output by more than 7-fold and approximately doubled both maximum shortening speed and the shortening velocity that generated peak power. We augmented these measurements by observing increased RLC phosphorylation of human and rat HF samples from endocardial left ventricular homogenate. These results demonstrate the importance of increased RLC phosphorylation in the up-regulation of myocardial performance and suggest that reduced RLC phosphorylation is a key aspect of impaired contractile function in the diseased myocardium. We are currently using optical trapping and in vitro motility assays to explore the effect of phosphorylation on purified cardiac muscle myosin.