The Role of Heat-Shock Proteins in the Regulation of Steroid Receptor Function
It has been known for almost three decades that steroid aporeceptors exist in a large complex sedimenting at 9S which becomes reduced to about 4S upon ligand binding. Ever-improving tools have helped to provide overwhelming evidence that steroid receptors form hormone-reversible complexes with the heat-shock protein 90 (Hsp90) plus several Hsp90 accessory proteins (Pratt 1993, Smith and Toft 1993, Pratt and Toft 1997, Toft 1997). The protein components of the aporeceptor complex have been characterized and cloned. Assembly can now be recapitulated in vitro with purified components. The vast majority of the evidence that this heterocomplex exists and is relevant to the regulation of steroid receptor activity in cells is based on biochemical experiments in cell-free systems. In the last few years, a variety of experiments including genetic experiments, both in mammalian tissue culture cells and in budding yeast, have begun to fill in this gap. In this review, I will focus on the progress that has been achieved with in vivo experiments.
KeywordsProgesterone Receptor Glucocorticoid Receptor Steroid Receptor Hsp90 Function Hsp90 Complex
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