Steroid receptors form soluble heterocomplexes with the 90-kDa heat-shock protein (Hsp90) and other chaperones and co-chaperones. The assembly and composition of the oligomer is influenced by the presence and nature of the bound steroid. Although these receptors shuttle dynamically in and out of the nucleus, their primary localization in the absence of steroid can be mainly cytoplasmic, mainly nuclear, or partitioned into both cellular compartments. Upon steroid binding, receptors become localized to the nucleus via the transportosome, a retrotransport molecular machinery that comprises Hsp90, a high-molecular-weight immunophilin, and dynein motors. This molecular machinery, first evidenced in steroid receptors, can also be used by other soluble proteins. In this review, we dissect the complete model of this transport machinery system.

类固醇受体与 90-kDa 热休克蛋白 (Hsp90) 和其他伴侣和共同伴侣形成可溶性异质复合物。低聚物的组装和组成受结合类固醇的存在和性质的影响。尽管这些受体动态穿梭进出细胞核，但在没有类固醇的情况下，它们的主要定位可能主要是细胞质的，主要是细胞核的，或者分为两个细胞区室。类固醇结合后，受体通过转运体定位于细胞核，转运体是一种逆向转运分子机制，包括 Hsp90、高分子量亲免蛋白和动力蛋白马达。这种分子机制，首先在类固醇受体中得到证实，也可以被其他可溶性蛋白质使用。在这篇评论中，我们剖析了这个运输机械系统的完整模型。