An embryonic myosin isoform enables stretch activation and cyclical power in Drosophila jump muscle.
An embryonic myosin isoform enables stretch activation and cyclical power in Drosophila jump muscle.
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DOI：
10.1016/j.bpj.2013.04.057
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发表时间：
2013-06
影响因子：
3.4
通讯作者：
Cuiping Zhao;D. Swank
中科院分区：
文献类型：
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作者：
Cuiping Zhao;D. Swank
牵张激活（SA）是一种增加肌肉力量和振荡发电的机械特性，其背后的机制尚不清楚。我们使用果蝇转基因技术和我们的新肌肉制备，跳跃肌，以确定是否肌球蛋白重链亚型影响SA力产生的幅度和速率。我们发现果蝇跳跃肌在pCa 5.0的振荡条件下显示出很低的SA力，不能产生正功率。然而，我们通过用胚胎同种型（EMB）取代其肌球蛋白同种型，将跳跃肌转变为中度拉伸激活。表达EMB后，跳跃肌SA力增加163%，产生净正功率。EMB的表达使SA力的形成率降低了58%。发电是Pi依赖性的，因为来自EMB的正功率需要> 4mM Pi。Pi增加EMB SA力，但不增加野生型SA力。我们的数据表明，当表达EMB的肌肉被拉伸时，EMB比野生型跳跃肌肉更容易被向后驱动到弱束缚状态。这增加了可用于快速结合肌动蛋白并有助于SA力产生的肌球蛋白头的数量。我们得出结论，肌球蛋白重链亚型影响SA动力学和SA力，这可以确定肌肉是否能够在固定的钙浓度下产生振荡功率。
The mechanism behind stretch activation (SA), a mechanical property that increases muscle force and oscillatory power generation, is not known. We usedDrosophilatransgenic techniques and our new muscle preparation, the jump muscle, to determine if myosin heavy chain isoforms influence the magnitude and rate of SA force generation. We found thatDrosophilajump muscles show very low SA force and cannot produce positive power under oscillatory conditions at pCa 5.0. However, we transformed the jump muscle to be moderately stretch-activatable by replacing its myosin isoform with an embryonic isoform (EMB). Expressing EMB, jump muscle SA force increased by 163% and it generated net positive power. The rate of SA force development decreased by 58% with EMB expression. Power generation is Pi dependent as >4 mM Pi was required for positive power from EMB. Pi increased EMB SA force, but not wild-type SA force. Our data suggest that when muscle expressing EMB is stretched, EMB is more easily driven backward to a weakly bound state than wild-type jump muscle. This increases the number of myosin heads available to rapidly bind to actin and contribute to SA force generation. We conclude that myosin heavy chain isoforms influence both SA kinetics and SA force, which can determine if a muscle is capable of generating oscillatory power at a fixed calcium concentration.