Nebulin stiffens the thin filament and augments cross-bridge interaction in skeletal muscle.
Nebulin stiffens the thin filament and augments cross-bridge interaction in skeletal muscle.
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DOI：
10.1073/pnas.1804726115
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发表时间：
2018-10-09
影响因子：
11.1
通讯作者：
Granzier HL
中科院分区：
文献类型：
--
作者：
Kiss B;Lee EJ;Ma W;Li FW;Tonino P;Mijailovich SM;Irving TC;Granzier HL
NeBulin是骨骼肌中一种巨大的肌动蛋白结合蛋白，定位于细丝的大部分长度上。基因的改变或星云蛋白表达水平的降低伴随着肌肉力量的急剧丧失，导致肌肉无力和严重的骨骼肌病。利用一种可诱导的、组织特异性的、在骨骼肌中不表达的烟雾素基因敲除小鼠模型，我们用X射线衍射仪研究了生理条件下被动肌肉和收缩肌肉中细丝的超微结构。研究发现，在星云蛋白敲除肌肉中，细丝僵硬程度降低了三倍，细丝调节蛋白和跨桥行为受到损害。星云蛋白使细丝变硬，并负责产生生理水平的力。NeBulin是一种巨大的肌小节蛋白，它沿着骨骼肌中的肌动蛋白细丝，从Z盘到细丝尖端附近。星云蛋白的突变会导致线虫肌病患者的肌肉无力，这表明星云蛋白在力量产生中发挥着重要作用，但人们对星云蛋白对细丝结构和功能的影响知之甚少。在这里，我们使用了小角X射线衍射，并比较了缺乏星云蛋白的完整肌肉(使用条件性星云蛋白基因敲除，Neb CKO)和对照(Ctrl)肌肉。当肌肉被激活时，两种基因的肌动蛋白亚单位重复间隔(27ä)增加；当转换为细丝硬度时，Ctrl肌的值为30pN/nm，Neb CKO肌的值为10pN/nm；即当存在星云蛋白时，细丝的硬度大约增加了三倍。相反，粗丝硬度在不同的基因型之间没有差异。在被动和收缩的Neb CKO肌肉以及原肌球蛋白和肌钙蛋白运动受损的患者中，发现左手(59？)细丝螺旋节距显著缩短。此外，在收缩Neb CKO肌肉时，肌球蛋白向细丝的质量转移减少，这表明跨桥相互作用减少。我们得出结论，星云蛋白对生理力水平至关重要，因为它极大地使骨骼肌细丝变硬，并有助于细丝激活和跨桥招募。
Nebulin is a giant actin-binding protein in skeletal muscle which localizes along most of the length of the thin filament. Genetic alterations or reduction in the expression level of nebulin are accompanied by dramatic loss in muscle force, resulting in muscle weakness and severe skeletal muscle myopathy. Using an inducible and tissue-specific nebulin-knockout mouse model in which nebulin is not expressed in skeletal muscle, we investigated the ultrastructure of thin filaments in passive and contracting muscle under physiological conditions using X-ray diffraction. Thin filaments were found to be threefold less stiff in nebulin-knockout muscle, and thin filament regulatory protein and cross-bridge behavior was impaired. Nebulin stiffens the thin filaments and is responsible for generating physiological levels of force. Nebulin is a giant sarcomeric protein that spans along the actin filament in skeletal muscle, from the Z-disk to near the thin filament pointed end. Mutations in nebulin cause muscle weakness in nemaline myopathy patients, suggesting that nebulin plays important roles in force generation, yet little is known about nebulin’s influence on thin filament structure and function. Here, we used small-angle X-ray diffraction and compared intact muscle deficient in nebulin (using a conditional nebulin-knockout, Neb cKO) with control (Ctrl) muscle. When muscles were activated, the spacing of the actin subunit repeat (27 Å) increased in both genotypes; when converted to thin filament stiffness, the obtained value was 30 pN/nm in Ctrl muscle and 10 pN/nm in Neb cKO muscle; that is, the thin filament was approximately threefold stiffer when nebulin was present. In contrast, the thick filament stiffness was not different between the genotypes. A significantly shorter left-handed (59 Å) thin filament helical pitch was found in passive and contracting Neb cKO muscles, as well as impaired tropomyosin and troponin movement. Additionally, a reduced myosin mass transfer toward the thin filament in contracting Neb cKO muscle was found, suggesting reduced cross-bridge interaction. We conclude that nebulin is critically important for physiological force levels, as it greatly stiffens the skeletal muscle thin filament and contributes to thin filament activation and cross-bridge recruitment.
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影响因子：
4.8
作者：
Chandra, Murali;Mamidi, Ranganath;Granzier, Henk
通讯作者：
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影响因子：
3.5
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TRINICK, J
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通讯作者：
Granzier, Henk
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通讯作者：
CARLIER, MF