Nebulette is a powerful cytolinker organizing desmin and actin in mouse hearts
Nebulette is a powerful cytolinker organizing desmin and actin in mouse hearts
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DOI：
10.1091/mbc.e16-04-0237
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发表时间：
2016-12-01
影响因子：
3.3
通讯作者：
Conover, Gloria M.
中科院分区：
文献类型：
--
作者：
Hernandez, Daniel A.;Bennett, Christina M.;Conover, Gloria M.
在携带neblette突变的患者的心脏中，经常观察到肌节外结蛋白中间丝系统的心肌细胞中的严重的一般性紊乱。然而，结蛋白细胞骨架和含雾化粒的肌节之间的分子和功能关系仍不清楚。在这里，我们报告了一个高亲和力的体外相互作用之间的neblette和结蛋白丝。一个主要的相互作用位点已被映射到结蛋白α-螺旋杆域，表明丝核心直接参与结合的nebulette。疾病突变的结蛋白变体E245 D和T453 I表现出增加的结合亲和力，延迟丝组装动力学，并导致网络的显着削弱。在离体鸡心肌细胞和犬心脏切片中，我们通过基态耗竭和共聚焦显微镜发现，模块5的nebulette从Z盘相关的结蛋白丝向外延伸到肌节的中心。因此，在Des（-/-）小鼠的心肌中，心肌肌动蛋白水平升高与雾化片分布的改变相关。我们的数据表明，需要一个组织良好的结蛋白网络，以适应最佳构象的肌节上的雾化结合和招募心脏α-肌动蛋白。因此，我们提出，nebulette与nebulin协同作用，以加强和时间微调横纹肌松弛-收缩周期。
In the hearts of patients bearing nebulette mutations, a severe general disorganization in cardiomyocytes of the extrasarcomeric desmin intermediate filament system is frequently observed. However, the molecular and functional relationship between the desmin cytoskeleton and nebulette-containing sarcomeres is still unclear. Here we report a high-affinity in vitro interaction between nebulette and desmin filaments. A major interaction site has been mapped to the desmin a-helical rod domain, indicating that the filament core is directly involved in the binding of nebulette. The disease-mutant desmin variants E245D and T453I exhibited increased binding affinity for nebulette, delayed filament assembly kinetics, and caused significant weakening of networks. In isolated chick cardiomyocytes and sections from canine heart, we revealed by ground-state depletion and confocal microscopies that module 5 of nebulette extends outward from Z-disk-associated desmin filaments toward the center of the sarcomere. Accordingly, in the myocardium of Des(-/-) mice, elevated levels of cardiac actin correlated with alterations in the distribution of nebulette. Our data suggest that a well-organized desmin network is required to accommodate an optimal conformation of nebulette on sarcomeres to bind and recruit cardiac a-actin. Hence we propose that nebulette acts in synergy with nebulin to reinforce and temporally fine-tune striated muscle relaxation-contraction cycles.