Chaperones, immunophilins and nuclear receptor shuttling

描述(申请人提供)：尽管已知囊泡中的蛋白质运动发生在细胞骨架束上，但非囊泡相关蛋白质的运动尚不清楚。可溶性蛋白质如MAPKs、STATS、P53、NFkB、类固醇受体、细胞周期蛋白等不是静态地局限于细胞质或细胞核，而是能够动态地穿梭于核孔中，即使在一个隔室中的分子数量远远大于另一个隔室中的少数分子数量时也是如此。此外，人们一直认为，可溶性蛋白质是通过扩散运动的。蛋白质的错误定位会导致可怕的细胞后果，并导致包括癌症在内的多种病理现象。在这方面，200多种疾病与蛋白质运输失败或定位错误有关。因此，与所有信号通路有关的一个主要未解决的问题是蛋白质如何移动到它们的作用部位。皮质类固醇受体构成了研究蛋白质运动的极佳系统。在没有配体的情况下，它们主要定位于细胞质中，并在有配体的情况下迅速向细胞核移动。经典模型支持这样的观点，即当类固醇结合时，HSP90-免疫亲和素(IMM)-异源复合体从受体上解离，从而允许其核转位。在这里，我们挑战这个未经证实的模型，并假设HSP90-IMM复合体是受体通过细胞质移动所必需的，也影响其在核中的功能。由于配体-受体复合体是一个功能单位，因此也将研究配体结合对受体运动调节的影响。因此，本项目的具体目标是确定：a)与受体-HSP90异源复合体相关的蛋白质如何调节受体的运动，b)类固醇受体通过核孔复合体的核转位步骤是否需要属于HSP90-IMM异源复合体的蛋白质，c)调节受体与核基质的结合和核输出步骤的因子/S。

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.