Chaperones, immunophilins and nuclear receptor shuttling

描述（由申请人提供）：尽管已知囊泡中包含的蛋白质的移动发生在细胞骨架束上，但非囊泡相关蛋白质的移动是未知的。可溶性蛋白质如MAPK、STAT、p53、NFkB、类固醇受体、细胞周期蛋白等不以静态方式局限于细胞质或细胞核，而是能够动态地穿梭通过核孔，即使当给定隔室中的分子数量压倒性地大于位于另一隔室中的少量分子时。此外，人们一直认为可溶性蛋白质通过扩散移动。蛋白质错误启动具有可怕的细胞后果，并导致多种病理，包括癌症。在这方面，超过200种疾病与蛋白质的运输失败或错误定位有关。因此，一个涉及所有信号通路的主要未解决的问题涉及蛋白质如何移动到它们的作用位点。皮质类固醇受体是研究蛋白质运动的一个极好的系统。它们在没有配体的情况下主要位于细胞质中，并与配体一起迅速向细胞核移动。经典模型支持的概念，即类固醇结合后，热休克蛋白90-亲免蛋白（IMM）-异源复合物从受体上解离，这允许其核转位。在这里，我们挑战这个未经证实的模型，并假设热休克蛋白90-IMM复合物是通过细胞质的受体运动所需的，也影响其在细胞核中的功能。由于配体-受体复合物是一个功能单位，因此也将研究配体结合对受体运动调节的影响。因此，本项目的具体目的是确定：a）与受体-hsp 90异源复合物相关的蛋白质如何调节受体运动，B）类固醇受体通过核孔复合物的核转位步骤是否需要属于hsp 90-IMM异源复合物的蛋白质，c）可以调节受体锚定到核基质和核输出步骤的因子。

DESCRIPTION (provided by applicant): Although movement of proteins comprised in vesicles is known to occur on cytoskeletal tracts, the movement of non-vesicle associated proteins is unknown. Soluble proteins such as MAPKs, STATs, p53, NFkB, steroid receptors, cyclins, etc. are not confined to the cytoplasm or the nucleus in a static manner, but are capable of shuttling dynamically through the nuclear pore even when the number of molecules in a given compartment is overwhelmingly larger than the small number located in the other compartment. Moreover, it has always been posited that soluble proteins move by diffusion. Protein mistargeting has dire cellular consequences and leads to a large variety of pathologies, including cancer. In this regard, more than 200 diseases have been related with failures in the transport or mislocalization of proteins. Therefore, a major unsolved problem that pertains to all signaling pathways relates to how proteins move to their sites of action. Corticosteroid receptors constitute an excellent system for studying protein movement. They are primarily located in the cytoplasm in the absence of ligand and rapidly move towards the nucleus with ligand. The classical model supports the notion that, upon steroid binding, the hsp90-immunophilin (IMM)-heterocomplex dissociates from the receptor, which permits its nuclear translocation. Here, we challenge this unproven model and postulate that the hsp90-IMM complex is required for receptor movement through the cytoplasm and also affects its function in the nucleus. Inasmuch as the ligand-receptor complex is a functional unit, the effect of ligand-binding on the regulation of receptor movement will also be studied. Therefore, the specific aims of this project are to determine: a) how proteins associated to the receptor-hsp90 heterocomplex regulate receptor movement, b) if proteins that belong to the hsp90-IMM heterocomplex are required for the nuclear translocation step of steroid receptors through the nuclear pore complex, c) the factor/s that can regulate the receptor anchorage to the nuclear matrix and the nuclear export step.