Characterization of Ran-driven cargo transport and the RanGTPase system by kinetic measurements and computer simulation
Characterization of Ran-driven cargo transport and the RanGTPase system by kinetic measurements and computer simulation
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DOI：
10.1093/emboj/cdg113
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发表时间：
2003-03-03
期刊：
影响因子：
11.4
通讯作者：
Ribbeck, K
中科院分区：
文献类型：
--
作者：
Görlich, D;Seewald, MJ;Ribbeck, K
在这里，我们分析了RanGTdR系统及其耦合受体介导的核运输。我们的模拟预测在HeLa细胞核RanGTP水平是非常敏感的细胞能量电荷和超过细胞质浓度约1000倍。RanGTP梯度的陡度似乎受到细胞质RanGAP浓度和核孔复合物（NPC）对核RanGTP的不完善保留的限制，但不受RCC1的核苷酸交换活性的限制。RanBP1和RanGAP的NPC定位对RanGTP梯度都没有显著的直接影响。NTF2介导的Ran输入似乎是Ran驱动的核运输的最大容量的瓶颈。我们表明，单向核运输可以忠实地模拟没有一个矢量NPC通道的假设，运输受体只需要可逆地跨越NPC和开关的RanGTP梯度响应货物的亲和力。一个显着的RanGTP梯度核膜（NE）破裂后，显然只能存在于大的细胞质。这表明RanGTP梯度可以提供有丝分裂纺锤体和NE组装在早期胚胎细胞的位置信息，但几乎没有任何在小的体细胞。
Here, we analyse the RanGTPase system and its coupling to receptor-mediated nuclear transport. Our simulations predict nuclear RanGTP levels in HeLa cells to be very sensitive towards the cellular energy charge and to exceed the cytoplasmic concentration approximate to1000-fold. The steepness of the RanGTP gradient appears limited by both the cytoplasmic RanGAP concentration and the imperfect retention of nuclear RanGTP by nuclear pore complexes (NPCs), but not by the nucleotide exchange activity of RCC1. Neither RanBP1 nor the NPC localization of RanGAP has a significant direct impact on the RanGTP gradient. NTF2-mediated import of Ran appears to be the bottleneck for maximal capacity of Ran-driven nuclear transport. We show that unidirectional nuclear transport can be faithfully simulated without the assumption of a vectorial NPC passage; transport receptors only need to reversibly cross NPCs and switch their affinity for cargo in response to the RanGTP gradient. A significant RanGTP gradient after nuclear envelope (NE) breakdown can apparently exist only in large cytoplasm. This indicates that RanGTP gradients can provide positional information for mitotic spindle and NE assembly in early embryonic cells, but hardly any in small somatic cells.