Nesprins comprise a family of multi-isomeric scaffolding proteins, forming the linker of nucleoskeleton-and-cytoskeleton complex with lamin A/C, emerin and SUN1/2 at the nuclear envelope. Mutations in nesprin-1/-2 are associated with Emery-Dreifuss muscular dystrophy (EDMD) with conduction defects and dilated cardiomyopathy (DCM). We have previously observed sarcomeric staining of nesprin-1/-2 in cardiac and skeletal muscle, but nesprin function in this compartment remains unknown. In this study, we show that specific nesprin-2 isoforms are highly expressed in cardiac muscle and localize to the Z-disc and I band of the sarcomere. Expression of GFP-tagged nesprin-2 giant spectrin repeats 52 to 53, localized to the sarcomere of neonatal rat cardiomyocytes. Yeast two-hybrid screening of a cardiac muscle cDNA library identified telethonin and four-and-half LIM domain (FHL)-2 as potential nesprin-2 binding partners. GST pull-down and immunoprecipitation confirmed the individual interactions between nesprin-2/telethonin and nesprin-2/FHL-2, and showed that nesprin-2 and telethonin binding was dependent on telethonin phosphorylation status. Importantly, the interactions between these binding partners were impaired by mutations in nesprin-2, telethonin, and FHL-2 identified in EDMD with DCM and hypertrophic cardiomyopathy patients. These data suggest that nesprin-2 is a novel sarcomeric scaffold protein that may potentially participate in the maintenance and/or regulation of sarcomeric organization and function.

中文翻译：

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Nesprin-2 是心肌细胞肌节中 telethonin 和 FHL-2 的新型支架蛋白


Nesprins 包含一个多异构体支架蛋白家族，与核膜上的核纤层蛋白 A/C、emerin 和 SUN1/2 形成核骨架和细胞骨架复合物的连接体。 nesprin-1/-2 突变与伴有传导缺陷的 Emery-Dreifuss 肌营养不良症 (EDMD) 和扩张型心肌病 (DCM) 相关。我们之前在心肌和骨骼肌中观察到了 Nesprin-1/-2 的肌节染色，但 Nesprin 在该区室中的功能仍然未知。在这项研究中，我们发现特定的 nesprin-2 亚型在心肌中高表达，并定位于肌节的 Z 盘和 I 带。 GFP 标记的 nesprin-2 巨型血影蛋白重复序列​​ 52 至 53 的表达，定位于新生大鼠心肌细胞的肌节。心肌 cDNA 文库的酵母二杂交筛选确定了 telethonin 和四半 LIM 结构域 (FHL)-2 作为潜在的 nesprin-2 结合伴侣。 GST 下拉和免疫沉淀证实了 nesprin-2/telethonin 和 nesprin-2/FHL-2 之间的个体相互作用，并表明 nesprin-2 和 telethonin 结合依赖于 telethonin 磷酸化状态。重要的是，这些结合伙伴之间的相互作用因在扩张型心肌病和肥厚型心肌病患者的 EDMD 中发现的 nesprin-2、telethonin 和 FHL-2 突变而受到损害。这些数据表明，nesprin-2 是一种新型肌节支架蛋白，可能参与肌节组织和功能的维持和/或调节。