The nucleo-cytoplasmic actin-binding protein CapG lacks a nuclear export sequence present in structurally related proteins
The nucleo-cytoplasmic actin-binding protein CapG lacks a nuclear export sequence present in structurally related proteins
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DOI：
10.1074/jbc.m209946200
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发表时间：
2003-05-16
影响因子：
4.8
通讯作者：
Gettemans, J
中科院分区：
文献类型：
--
作者：
Van Impe, K;De Corte, V;Gettemans, J
尽管进行了深入的结构和功能分析，但CAPG是一种普遍存在的F-肌动蛋白带刺末端封端蛋白，控制细胞中肌动蛋白微丝的转换，但CAPG如何能够驻留在细胞核和细胞质中，而结构相关的肌动蛋白结合蛋白主要是细胞质，目前仍不清楚。在这里，我们报告了CAPG、Severin和FragminP不同亚细胞定位的分子基础。绿色荧光蛋白标记的FragminP和Severin在用CRM1抑制剂Leptomycin B处理后在细胞核中积聚。我们在Serverin和FraminP中发现了一个核输出序列，而CAPG中没有这个序列。氨基酸Met(1)-Leu(27)的缺失导致Severin和FraminP的核积累。将该序列标记到CAPG可触发核输出，而输出序列中单个亮氨酸残基(Leu(17)、Leu(21)和Leu(27))的突变则抑制核输出。基于这些发现，在肌肉特异性肌动蛋白结合蛋白myopodin和一种类似RecQ的解旋酶Bloom综合征蛋白中发现了核输出信号。Myopodin核输出序列的缺失阻止了瞬时过表达myopodin的C2C12细胞对I型胶原的侵袭。我们的发现解释了不同类别的肌动蛋白结合蛋白的调节亚细胞靶向。
Despite thorough structure-function analyses, it remains unclear how CapG, a ubiquitous F-actin barbed end capping protein that controls actin microfilament turnover in cells, is able to reside in the nucleus and cytoplasm, whereas structurally related actin-binding proteins are predominantly cytoplasmic. Here we report the molecular basis for the different subcellular localization of CapG, severin, and fragminP. Green fluorescent protein-tagged fragminP and severin accumulate in the nucleus upon treatment of transfected cells with the CRM1 inhibitor leptomycin B. We identified a nuclear export sequence in severin and fragminP, which is absent in CapG. Deletion of amino acids Met(1)-Leu(27) resulted in nuclear accumulation of severin and fragminP. Tagging this sequence to CapG triggered nuclear export, whereas mutation of single leucine residues (Leu(17), Leu(21), and Leu(27)) in the export sequence inhibited nuclear export. Based on these findings, a nuclear export signal was identified in myopodin, a muscle-specific actin-binding protein, and the Bloom syndrome protein, a RecQ-like helicase. Deletion of the myopodin nuclear export sequence blocked invasion into collagen type I of C2C12 cells transiently overexpressing myopodin. Our findings explain regulated subcellular targeting of distinct classes of actin-binding proteins.