Ran & Energy Requirements for Nuclear Protein Import

描述(由申请人提供)： 大分子在细胞核和细胞质之间的运输是由核质穿梭受体介导的，核质穿梭受体通过与一系列核孔蛋白结合将货物转移到核孔复合体(NPC)。小的GTP酶RAN通过调节货物与这些转运受体的相互作用，在核进口中发挥关键作用。几个小组已经证明，在没有RAN和/或NTP水解的情况下，通过Importinα/Importinβ和Transportin受体途径在体外可以发生某些小货物的核进口。相比之下，Gerace实验室最近的工作表明，通过这些途径有效地进口某些大型货物既需要RAN，也需要可水解性GTP。为了适应这些发现，提出了一个模型，其中货物-受体复合体在核进口中对RAN和能量的需求由该复合体的扩散速度和该复合体对核孔素的亲和力控制。这项提案的目的是通过检查货物大小和核孔素与Importinα/Importinβ、Snurportin/Importinβ和Transportin受体通路中核孔素的亲和力的影响来详细测试这一模型。这些研究有望为深入了解鼻咽癌易位的基本机制和这一过程中RAN的需求提供依据。这是一个基本的过程，在广泛的正常条件下对细胞的生物学很重要，在某些病理状态下可能会改变。

DESCRIPTION (provided by applicant): Trafficking of macromolecules between the nucleus and cytoplasm is mediated by nucleocytoplasmic shuttling receptors, which translocate cargo through the nuclear pore complex (NPC) by binding to a series of nucleoporins. The small GTPase Ran plays a critical role in nuclear import by modulating the interaction of cargo with these transport receptors. Several groups have shown that in vitro nuclear import of certain small cargoes by the importin alpha/importin beta and transportin receptor pathways can occur in the absence of Ran and/or NTP hydrolysis. By contrast, recent work from the Gerace lab has shown that both Ran and hydrolyzable GTP are needed for the efficient import of certain large cargoes by these pathways. To accommodate these findings, a model is proposed where the requirements for Ran and energy in nuclear import of a cargo-receptor complex is governed by the diffusion rate of the complex and by the affinity of the complex for nucleoporins. The aims of this proposal are directed at testing this model in detail by examining the effects of cargo size and affinity of the transport complex for nucleoporins in the importin alpha/importin beta, snurportin/importin beta, and the transportin receptor pathways. These studies are expected to provide insight on the basic mechanism of translocation through the NPC and the Ran requirement in this process. This is a fundamental process that is important for the biology of the cell in a wide range of normal conditions and may be altered in certain pathological states.