Role of phosphorylation in cardiac muscle myosin

肌球蛋白的调节轻链（RLC）的磷酸化在许多形式的心脏疾病中改变，包括遗传性（HCM和DCM）和获得性（衰竭、梗塞和糖尿病）。RLC的磷酸化通过影响钙敏感性、力、功率和缩短速度来改变肌肉力学。目前，我们还不清楚这些对肌肉的影响是如何在分子水平上产生的。为此，我们从猪内皮细胞中分离出全长心肌肌球蛋白，并在体外改变其磷酸化水平。我们比较了具有完全（100%）RLC磷酸化、中间磷酸化（40%和50%）和根除磷酸化（0%）的肌球蛋白群体。因此，我们可以关联酶和运动的变化与RLC磷酸化。我们发现，当肌球蛋白具有100%磷酸化RLCs，ATP酶速率加快，肌动蛋白滑行速度在假定的卸载和加载（存在-辅肌动蛋白）的条件下加速。 这些结果与RLC磷酸化对跨桥运动动力学的影响是一致的。RLC磷酸化减少了肌动球蛋白附着的寿命，如在光阱三珠测定中所测量的。这些结果表明RLC磷酸化在调节心肌肌球蛋白功能中具有重要作用。- 结果与RLC磷酸化正常水平降低可能导致心血管疾病和心力衰竭的假设一致。

Phosphorylation of the regulatory light chain of myosin (RLC) is altered in many forms of cardiac diseases, both inherited (HCM and DCM) and acquired (failure, infarction and diabetes). Phosphorylation of the RLC alters muscle mechanics by influencing calcium sensitivity, force, power and shortening velocity. Currently we do not understand how these effects on muscle are created at the molecular level of the cross-bridge. To this end, we isolated full-length cardiac myosin from porcine endocardium and altered its phosphorylation level in-vitro. We compare populations of myosins with complete (100%) RLC phosphorylation, intermediate phosphorylation (40% & 50%), and eradicated phosphorylation (0%). We could thereby correlate enzymatic and motility changes produced with RLC phosphorylation. We find that when myosin possesses 100% phosphorylated RLCs, the ATPase rate is accelerated and actin gliding velocities in putative unloaded and loaded (in presence of -actinin) conditions are accelerated. These results are consistent with the influence of RLC phosphorylation on the kinetics of the cross-bridge motor kinetics. RLC phosphorylation reduced the lifetime of actomyosin attachment as measured in the optical trap three-bead assay. These results suggest an important role for RLC phosphorylation in regulating the function of cardiac myosin. - The results are consistent with the hypothesis that reductions in normal levels of RLC phosphorylation may precipitate cardiovascular disorders and heart failure.