Passive stiffness in Drosophila indirect flight muscle reduced by disrupting paramyosin phosphorylation, but not by embryonic myosin S2 hinge substitution.
Passive stiffness in Drosophila indirect flight muscle reduced by disrupting paramyosin phosphorylation, but not by embryonic myosin S2 hinge substitution.
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DOI：
10.1529/biophysj.106.088492
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发表时间：
2006-12
影响因子：
3.4
通讯作者：
Yudong Hao;Mark S. Miller;D. Swank;Hongjun Liu;S. Bernstein;D. Maughan;G. Pollack
中科院分区：
文献类型：
--
作者：
Yudong Hao;Mark S. Miller;D. Swank;Hongjun Liu;S. Bernstein;D. Maughan;G. Pollack
高被动刚度是果蝇等昆虫的异步间接飞行肌（IFM）的特征之一。为了评估两个粗丝蛋白结构域对被动肌节刚度的影响，并研究它们与IFM功能的相关性，我们使用微制造的杠杆和高分辨率成像系统来研究两组转基因果蝇系的被动IFM肌原纤维刚度。一组（铰链开关突变体）的内源性S2铰链区的一部分被胚胎版本取代;另一组（副肌球蛋白突变体）有一个或多个假定的磷酸化位点附近的N-末端的副肌球蛋白残疾。两个转基因组都表现出严重受损的飞行能力。在这项研究中，我们发现铰链开关组的被动弹性模量没有差异（与对照组相比），但副肌球蛋白突变体减少了15%。所有的结果都证实了肌肉纤维力学实验上进行相同的线路。肌原纤维弹性不受铰链转换影响的事实意味着替代S2铰链不会严重影响被动肌节刚度。相反，在果蝇中破坏副肌球蛋白磷酸化位点后观察到的机械缺陷表明，副肌球蛋白磷酸化对维持IFM肌原纤维的高被动刚度很重要，可能是通过影响副肌球蛋白与其他肌节蛋白的相互作用。
High passive stiffness is one of the characteristic properties of the asynchronous indirect flight muscle (IFM) found in many insects like Drosophila. To evaluate the effects of two thick filament protein domains on passive sarcomeric stiffness, and to investigate their correlation with IFM function, we used microfabricated cantilevers and a high resolution imaging system to study the passive IFM myofibril stiffness of two groups of transgenic Drosophila lines. One group (hinge-switch mutants) had a portion of the endogenous S2 hinge region replaced by an embryonic version; the other group (paramyosin mutants) had one or more putative phosphorylation sites near the N-terminus of paramyosin disabled. Both transgenic groups showed severely compromised flight ability. In this study, we found no difference (compared to the control) in passive elastic modulus in the hinge-switch group, but a 15% reduction in the paramyosin mutants. All results were corroborated by muscle fiber mechanics experiments performed on the same lines. The fact that myofibril elasticity is unaffected by hinge switching implies alternative S2 hinges do not critically affect passive sarcomere stiffness. In contrast, the mechanical defects observed upon disrupting paramyosin phosphorylation sites in Drosophila suggests that paramyosin phosphorylation is important for maintaining high passive stiffness in IFM myofibrils, probably by affecting paramyosin's interaction with other sarcomeric proteins.