Nebulin interacts with CapZ and regulates thin filament architecture within the Z-disc
Nebulin interacts with CapZ and regulates thin filament architecture within the Z-disc
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DOI：
10.1091/mbc.e07-07-0690
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发表时间：
2008-05-01
影响因子：
3.3
通讯作者：
Gregorio, Carol C.
中科院分区：
文献类型：
--
作者：
Pappas, Christopher T.;Bhattacharya, Nandini;Gregorio, Carol C.
横纹肌中肌动蛋白丝的倒刺末端锚定在Z盘内并被CapZ覆盖;这种蛋白质在体外阻断肌动蛋白聚合和解聚。细丝的成熟长度很可能是由巨大的“分子统治者”星云蛋白决定的，它跨越了细丝的长度。在这里，我们报告CapZ特异性相互作用的C末端的星云蛋白（模块160-164）的印迹覆盖，固相结合，色氨酸荧光，和SPOTs膜测定。星云蛋白模块160-164与CapZ的结合不影响CapZ在体外给肌动蛋白丝加帽的能力，这与我们的观察一致，即CapZ的两个C-末端肌动蛋白结合区域对于其与星云蛋白的相互作用都不是必需的。使用小干扰RNA敲除鸡骨骼肌管中的nebulin导致组装的CapZ减少，并且引人注目的是，肌动蛋白丝的倒刺末端的均匀对齐的损失。这些数据表明，星云蛋白通过与CapZ的直接相互作用，限制了细丝倒刺末端在Z盘上的位置。我们提出了一种新的Z盘结构的分子模型，其中星云蛋白与CapZ从相邻肌节的细丝相互作用，从而提供了肌节之间的结构联系。
The barbed ends of actin filaments in striated muscle are anchored within the Z-disc and capped by CapZ; this protein blocks actin polymerization and depolymerization in vitro. The mature lengths of the thin filaments are likely specified by the giant "molecular ruler" nebulin, which spans the length of the thin filament. Here, we report that CapZ specifically interacts with the C terminus of nebulin (modules 160-164) in blot overlay, solid-phase binding, tryptophan fluorescence, and SPOTs membrane assays. Binding of nebulin modules 160-164 to CapZ does not affect the ability of CapZ to cap actin filaments in vitro, consistent with our observation that neither of the two C-terminal actin binding regions of CapZ is necessary for its interaction with nebulin. Knockdown of nebulin in chick skeletal myotubes using small interfering RNA results in a reduction of assembled CapZ, and, strikingly, a loss of the uniform alignment of the barbed ends of the actin filaments. These data suggest that nebulin restricts the position of thin filament barbed ends to the Z-disc via a direct interaction with CapZ. We propose a novel molecular model of Z-disc architecture in which nebulin interacts with CapZ from a thin filament of an adjacent sarcomere, thus providing a structural link between sarcomeres.