Binding of myosin binding protein-C to myosin subfragment S2 affects contractility independent of a tether mechanism
Binding of myosin binding protein-C to myosin subfragment S2 affects contractility independent of a tether mechanism
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DOI：
10.1161/01.res.0000147312.02673.56
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发表时间：
2004-10-29
影响因子：
20.1
通讯作者：
Moss, RL
中科院分区：
文献类型：
--
作者：
Harris, SP;Rostkova, E;Moss, RL
心肌肌球蛋白结合蛋白-C 基因 (cMyBP-C) 突变是遗传性肥厚型心肌病最常见的原因之一。尽管大多数 cMyBP-C 突变会导致阅读移码，预计会编码截短的肽，但尚不清楚这些肽的表达是否或如何导致疾病。一种可能性是，由于 N 末端含有肌球蛋白 S2 亚片段的独特结合位点，缩短的 cMyBP-C 肽可以通过与 S2 结合直接影响肌球蛋白收缩。为了检验这一假设，我们比较了含有肌球蛋白 S2 结合位点的 C1C2 蛋白对野生型和 cMyBP-C 敲除小鼠的透化肌细胞收缩特性的影响。在野生型肌细胞中，C1C2 蛋白可逆地增加肌丝 Ca2+ 对张力的敏感性，但对静息张力没有影响。在 cMyBP-C 敲除肌细胞中观察到相同的结果，其中 C1C2 增加了张力的 Ca2+ 敏感性，并在大约 5 mumol/L C1C2 时引发了半最大反应。最大力不受 C1C2 的影响。然而，cAMP 依赖性蛋白激酶对 C1C2 的磷酸化降低了其增加 Ca2+ 敏感性的能力。这些结果表明，C1C2 肽与 S2 的单独结合足以影响肌球蛋白收缩功能，并表明通过磷酸化调节 cMyBP-C 与肌球蛋白 S2 的结合直接影响肌丝 Ca2+ 敏感性。
Mutations in the cardiac myosin binding protein-C gene (cMyBP-C) are among the most prevalent causes of inherited hypertrophic cardiomyopathy. Although most cMyBP-C mutations cause reading frameshifts that are predicted to encode truncated peptides, it is not known if or how expression of these peptides causes disease. One possibility is that because the N-terminus contains a unique binding site for the S2 subfragment of myosin, shortened cMyBP-C peptides could directly affect myosin contraction by binding to S2. To test this hypothesis, we compared the effects of a C1C2 protein containing the myosin S2 binding site on contractile properties in permeablized myocytes from wild-type and cMyBP-C knockout mice. In wild-type myocytes, the C1C2 protein reversibly increased myofilament Ca2+ sensitivity of tension, but had no effect on resting tension. Identical results were observed in cMyBP-C knockout myocytes where C1C2 increased Ca2+ sensitivity of tension with the half-maximal response elicited at approximate to5 mumol/L C1C2. Maximum force was not affected by C1C2. However, phosphorylation of C1C2 by cAMP-dependent protein kinase reduced its ability to increase Ca2+ sensitivity. These results demonstrate that binding of the C1C2 peptide to S2 alone is sufficient to affect myosin contractile function and suggest that regulated binding of cMyBP-C to myosin S2 by phosphorylation directly influences myofilament Ca2+ sensitivity.