Novel Nuclear Nesprin-2 Variants Tether Active Extracellular Signal-regulated MAPK1 and MAPK2 at Promyelocytic Leukemia Protein Nuclear Bodies and Act to Regulate Smooth Muscle Cell Proliferation*
Novel Nuclear Nesprin-2 Variants Tether Active Extracellular Signal-regulated MAPK1 and MAPK2 at Promyelocytic Leukemia Protein Nuclear Bodies and Act to Regulate Smooth Muscle Cell Proliferation*
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DOI：
10.1074/jbc.m109.032557
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发表时间：
2009-10
期刊：
影响因子：
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通讯作者：
D. Warren;T. Tajsic;J. Mellad;R. Searles;Qiuping Zhang;C. Shanahan
中科院分区：
文献类型：
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作者：
D. Warren;T. Tajsic;J. Mellad;R. Searles;Qiuping Zhang;C. Shanahan
核和细胞质支架蛋白已被证明对于 MAPK 信号通路的时间和空间组织以及保真度至关重要。在这项研究中，我们表明，nesprin-2 是一种新型细胞外信号调节 MAPK1 和 2 (ERK1/2) 支架蛋白，通过将这些激酶束缚在早幼粒细胞白血病蛋白核体 (PML NB) 上来调节核信号传导。使用免疫荧光显微镜、GST 下拉和免疫沉淀，我们发现 nesprin-2、ERK1/2 和 PML 共定位并结合形成核复合物。通过 siRNA 介导的敲低或显性负性 nesprin-2 片段的过表达来干扰 nesprin-2 功能，增强了 ERK1/2 核信号传导，表现为 SP1 活性增加和 ELK1 磷酸化。 Nesprin-2 破坏和由此产生的持续 ERK1/2 信号的功能结果是增殖增加。重要的是，这些活性不是由先前识别的核膜 (NE) 靶向的 nesprin-2 同工型诱导的，而是由缺乏 KASH 结构域的新型核同工型介导的。综上所述，这项研究表明，nesprin-2 是一种新型核内支架，对于核 ERK1/2 信号保真度和细胞周期进展至关重要。
Nuclear and cytoplasmic scaffold proteins have been shown to be essential for temporal and spatial organization, as well as the fidelity, of MAPK signaling pathways. In this study we show that nesprin-2 is a novel extracellular signal-regulated MAPK1 and 2 (ERK1/2) scaffold protein that serves to regulate nuclear signaling by tethering these kinases at promyelocytic leukemia protein nuclear bodies (PML NBs). Using immunofluorescence microscopy, GST pull-down and immunoprecipitation, we show that nesprin-2, ERK1/2, and PML colocalize and bind to form a nuclear complex. Interference of nesprin-2 function, by either siRNA-mediated knockdown or overexpression of a dominant negative nesprin-2 fragment, augmented ERK1/2 nuclear signaling shown by increased SP1 activity and ELK1 phosphorylation. The functional outcome of nesprin-2 disruption and the resultant sustained ERK1/2 signal was increased proliferation. Importantly, these activities were not induced by previously identified nuclear envelope (NE)-targeted nesprin-2 isoforms but rather were mediated by novel nuclear isoforms that lacked the KASH domain. Taken together, this study suggests that nesprin-2 is a novel intranuclear scaffold, essential for nuclear ERK1/2 signaling fidelity and cell cycle progression.