Phosphorylation of a high molecular weight (approximately 600 kDa) protein regulates catch in invertebrate smooth muscle.
Phosphorylation of a high molecular weight (approximately 600 kDa) protein regulates catch in invertebrate smooth muscle.
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高分子量（约 600 kDa）蛋白质的磷酸化可调节无脊椎动物平滑肌的捕获。
DOI：
10.1023/a:1018683823020
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发表时间：
1997
影响因子：
2.7
通讯作者：
Butler,TM
中科院分区：
文献类型：
--
作者：
Siegman,MJ;Mooers,SU;Li,C;Narayan,S;Trinkle-Mulcahy,L;Watabe,S;Hartshorne,DJ;Butler,TM
平滑肌的一个独特特性是它能够以非常低的能量消耗来维持力量。这一特征在软体动物平滑肌中高度表达，例如贻贝的前足丝牵拉肌（ABRM），在称为“捕获”的收缩状态下。卡顿发生在肌肉最初激活后，其特点是在低 [Ca2+]i、高瞬时刚度、非常慢的跨桥循环速率和低 ATP 使用情况下长时间维持力。在完整的肌肉中，快速松弛（捕获物的释放）由血清素启动，并由 cAMP 的增加和蛋白激酶 A 的激活介导。我们试图确定哪些蛋白质在与透化 ABRM 中捕获物的释放相对应的时间过程中经历磷酸化的变化。只有一种蛋白质始终满足这一标准。这种蛋白质的分子量约为 600 kDa，摩尔浓度比肌球蛋白重链低约 30 倍，在捕获物释放过程中显示出磷酸化的增加。在研究的机械条件下（静止、激活、捕获和捕获释放），所有其他蛋白质（包括肌球蛋白轻链、肌球蛋白重链和副肌球蛋白）的磷酸化变化与 cAMP 诱导的 ~600 kDa 蛋白质磷酸化相比是最小的。在这些条件下，每摩尔~600 kDa 蛋白质掺入略少于一摩尔的磷酸盐。抑制 A 激酶可阻断 cAMP 诱导的蛋白质磷酸化增加和捕获物的释放。此外，蛋白质的不可逆硫代磷酸化阻止了捕获的发生。在完整的肌肉中，当捕获物与血清素一起释放时，蛋白质的磷酸化程度显着增加。在用血清素预处理的肌肉中，当肌肉随后被捕获时，蛋白质会发生净去磷酸化。我们得出结论，~600 kDa 蛋白的磷酸化状态调节捕获
A unique property of smooth muscle is its ability to maintain force with a very low expenditure of energy. This characteristic is highly expressed in molluscan smooth muscles, such as the anterior byssus retractor muscle (ABRM) of Mytilus edulis, during a contractile state called ‘catch’. Catch occurs following the initial activation of the muscle, and is characterized by prolonged force maintenance in the face of a low [Ca2+]i, high instantaneous stiffness, a very slow cross-bridge cycling rate, and low ATP usage. In the intact muscle, rapid relaxation (release of catch) is initiated by serotonin, and mediated by an increase in cAMP and activation of protein kinase A. We sought to determine which proteins undergo a change in phosphorylation on a time-course that corresponds to the release of catch in permeabilized ABRM. Only one protein consistently satisfied this criterion. This protein, having a molecular weight of ∼600 kDa and a molar concentration about 30 times lower than the myosin heavy chain, showed an increase in phosphorylation during the release of catch. Under the mechanical conditions studied (rest, activation, catch, and release of catch), changes in phosphorylation of all other proteins, including myosin light chains, myosin heavy chain and paramyosin, are minimal compared with the cAMP-induced phosphorylation of the ∼600 kDa protein. Under these conditions, somewhat less than one mole of phosphate is incorporated per mole of ∼600 kDa protein. Inhibition of A kinase blocked both the cAMP-induced increase in phosphorylation of the protein and the release of catch. In addition, irreversible thiophosphorylation of the protein prevented the development of catch. In intact muscle, the degree of phosphorylation of the protein increases significantly when catch is released with serotonin. In muscles pre-treated with serotonin, a net dephosphorylation of the protein occurs when the muscle is subsequently put into catch. We conclude that the phosphorylation state of the ∼600 kDa protein regulates catch