Phosphoregulation of Cardiac Inotropy via Myosin Binding Protein-C During Increased Pacing Frequency or β1-Adrenergic Stimulation
Phosphoregulation of Cardiac Inotropy via Myosin Binding Protein-C During Increased Pacing Frequency or β1-Adrenergic Stimulation
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DOI：
10.1161/circheartfailure.114.001585
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发表时间：
2015-05-01
影响因子：
9.7
通讯作者：
Moss, Richard L.
中科院分区：
文献类型：
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作者：
Tong, Carl W.;Wu, Xin;Moss, Richard L.
哺乳动物心脏对-肾上腺素能刺激表现出正性肌力反应，这是蛋白激酶a介导的磷酸化或心跳频率增加的结果（鲍迪奇效应）。在这些条件下，一些膜蛋白和肌纤维蛋白被磷酸化，但它们对收缩性增加的相对贡献尚不清楚。蛋白激酶A磷酸化心肌肌球蛋白结合蛋白c （cMyBP-C）加速了渗透性心肌的力发展动力学，但其在体内的作用尚不清楚。这样的理解是重要的，因为心脏的肾上腺素能反应和鲍迪奇效应在心力衰竭中都受到抑制。方法和结果研究了cMyBP-C磷酸化的作用，在cMyBP-C零背景下，小鼠WT和非磷酸化形式的cMyBP-C [ser273ala， ser282ala, ser302ala: cMyBP-C(t3SA)]表达水平相似。孤立乳头状肌的力和[Ca2+]（in）测量显示，cMyBP-C（t3SA）心肌由于起搏增加或(1)肾上腺素能刺激而增加的力和抽搐动力学几乎不存在，尽管每种情况下的[Ca2+]（in）瞬态与WT相似。生化测量证实，蛋白激酶A磷酸化了WT cMyBP-C的ser273， ser282和ser302。相比之下，CaMKII主要磷酸化ser302， ser282的磷酸化程度较低，ser273则完全不磷酸化。结论cMyBP-C的磷酸化可增加活体心肌的抽搐力和动力学。此外，cMyBP-C是由于cMyB-C的蛋白激酶a和CaMKII磷酸化而引起的-肾上腺素能刺激或起搏增加的收缩性增加的主要介质。
Background Mammalian hearts exhibit positive inotropic responses to -adrenergic stimulation as a consequence of protein kinase A-mediated phosphorylation or as a result of increased beat frequency (the Bowditch effect). Several membrane and myofibrillar proteins are phosphorylated under these conditions, but the relative contributions of these to increased contractility are not known. Phosphorylation of cardiac myosin-binding protein-C (cMyBP-C) by protein kinase A accelerates the kinetics of force development in permeabilized heart muscle, but its role in vivo is unknown. Such understanding is important because adrenergic responsiveness of the heart and the Bowditch effect are both depressed in heart failure.Methods and Results The roles of cMyBP-C phosphorylation were studied using mice in which either WT or nonphosphorylatable forms of cMyBP-C [ser273ala, ser282ala, ser302ala: cMyBP-C(t3SA)] were expressed at similar levels on a cMyBP-C null background. Force and [Ca2+](in) measurements in isolated papillary muscles showed that the increased force and twitch kinetics because increased pacing or (1)-adrenergic stimulation were nearly absent in cMyBP-C(t3SA) myocardium, even though [Ca2+](in) transients under each condition were similar to WT. Biochemical measurements confirmed that protein kinase A phosphorylated ser273, ser282, and ser302 in WT cMyBP-C. In contrast, CaMKII, which is activated by increased pacing, phosphorylated ser302 principally, ser282 to a lesser degree, and ser273 not at all.Conclusions Phosphorylation of cMyBP-C increases the force and kinetics of twitches in living cardiac muscle. Further, cMyBP-C is a principal mediator of increased contractility observed with -adrenergic stimulation or increased pacing because of protein kinase A and CaMKII phosphorylations of cMyB-C.