Progesterone Receptor and the hsp90 Chaperone Pathway

孕激素受体与热休克蛋白90分子伴侣通路。当在细胞质提取物中处于非活性形式时，禽类孕酮受体（PR）与大多数类固醇受体和几种其他细胞信号蛋白一样，与热休克蛋白hsp90复合。 这种复合物不是通过简单的结合形成的，而是通过一个需要ATP水解和几种额外蛋白质的过程形成的。 参与受体复合物形成的其他蛋白质是hsp70、三种hsp70共分子伴侣、hsp40、Hip和Hop、四种hsp90结合TPR蛋白和p23。 我们已经开发了一个化学定义的系统与纯化的蛋白质，有能力组装PR复合物与热休克蛋白90。 这种体外组装过程仅需要上述蛋白质中的五种，其似乎通过三个步骤进行以产生具有激素结合活性的PR。 这些研究的目的是进一步了解受体复合物的组装、激素结合后的解离以及受体相关蛋白的功能意义。这将通过广泛使用体外定义的组装系统来实现。 PR复合物形成的每个步骤的事件将根据蛋白质相互作用的动力学和ATP的利用来表征。 将对该系统进行修改，以允许研究PR从hsp90的激素依赖性解离。 这可能需要鉴定解离过程所需的新因素。 最后，我们将表征PR的结构域或元件，这些结构域或元件是结合热休克蛋白70和热休克蛋白90的相互作用位点，并研究促进热休克蛋白识别的性质。 这些研究应导致对类固醇受体激活过程的机制描述，并应提供有价值的信息，了解分子伴侣热休克蛋白70和热休克蛋白90的作用机制。

Progesterone receptor and the hsp90 chaperone pathway. When in its inactive form in cytosol extracts, the avian progesterone receptor (PR), like most steroid receptors and several other cell signaling proteins, is complexed with the heat shock protein hsp90. This complex does not form through a simple association, but through a process that requires ATP hydrolysis and several additional proteins. Other proteins involved in receptor complex formation are hsp70, three hsp70 co-chaperones, hsp40, Hip and Hop, four hsp90-binding TPR proteins and p23. We have developed a chemically defined system with purified proteins that has the capacity to assemble PR complexes with hsp90. Only five of the above proteins are needed for this in vitro assembly process which appears to proceed through three steps to generate PR with hormone binding activity. The objective of the proposed studies is to further our understanding on the assembly of receptor complexes, their dissociation upon hormone binding, and the functional significance of the receptor-associated proteins. This will be accomplished by extensive use of the in vitro defined assembly system. Events at each step of PR complex formation will be characterized in terms of the dynamics of protein interactions and the utilization of ATP. Modifications in the system will be made that allow the study of hormone- dependent dissociation of PR from hsp90. This will probably require the identification of new factors needed for the dissociation process. Finally, we will characterize the domains or elements of the PR that are interaction sites for binding hsp70 and hsp90 and investigate the properties which promote heat shock protein recognition. These studies should lead toward a mechanistic description of the steroid receptor activation process and should provide valuable information for understanding the mechanisms of action of the molecular chaperones hsp70 and hsp90.