NTF2 mediates nuclear import of Ran
NTF2 mediates nuclear import of Ran
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DOI：
10.1093/emboj/17.22.6587
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发表时间：
1998-11-16
期刊：
影响因子：
11.4
通讯作者：
Görlich, D
中科院分区：
文献类型：
--
作者：
Ribbeck, K;Lipowsky, G;Görlich, D
输入蛋白β家族转运受体在细胞核和细胞质之间穿梭，并介导大分子通过核孔复合物（NPC）的转运。这些受体与其货物之间的相互作用是通过结合 RanGTP 来调节的；所有受体都可能离开与 RanGTP 复合的细胞核，因此应该从细胞核中不断耗尽 RanGTP。我们在此描述了体外系统的开发，以研究核 Ran 的补充方式。 Ran 的核输入并不依赖于 Ran 较小尺寸所允许的简单扩散，而是受到可溶性转运因子的刺激。这种促进导入是细胞质 RanGDP 特有的，并采用核转运因子 2 (NTF2) 作为实际载体。 NTF2 最初将 RanGDP 与 NPC 结合，并且可能还介导 NTF2-RanGDP 复合物易位到 NPC 的核侧。直接的 NTF2-RanGDP 相互作用对于此过程至关重要，因为干扰 RanGDP-NTF2 相互作用的点突变也会干扰 Ran 输入。随后Ran的核积累也需要GTP，但不需要GTP水解。 Ran从NTF2释放到细胞核中，以及Ran输入的方向性，可能涉及核苷酸交换以生成RanGTP，NTF2对其没有可检测到的亲和力，随后RanGTP与输入蛋白β家族转运受体结合。
Importin beta family transport receptors shuttle between the nucleus and the cytoplasm and mediate transport of macromolecules through nuclear pore complexes (NPCs). The interactions between these receptors and their cargoes are regulated by binding RanGTP; all receptors probably exit the nucleus complexed with RanGTP, and so should deplete RanGTP continuously from the nucleus. We describe here the development of an in vitro system to study how nuclear Ran is replenished. Nuclear import of Ran does not rely on simple diffusion as Ran's small size would permit, but instead is stimulated by soluble transport factors. This facilitated import is specific for cytoplasmic RanGDP and employs nuclear transport factor 2 (NTF2) as the actual carrier. NTF2 binds RanGDP initially to NPCs and probably also mediates translocation of the NTF2-RanGDP complex to the nuclear side of the NPCs, A direct NTF2-RanGDP interaction is crucial for this process, since point mutations that disturb the RanGDP-NTF2 interaction also interfere with Ran import. The subsequent nuclear accumulation of Ran also requires GTP, but not GTP hydrolysis. The release of Ran from NTF2 into the nucleus, and thus the directionality of Ran import, probably involves nucleotide exchange to generate RanGTP, for which NTF2 has no detectable affinity, followed by binding of the RanGTP to an importin beta family transport receptor.