The common 90-kd protein component of non-transformed ‘8S’ steroid receptors is a heat-shock protein.

Abstract

Non‐transformed steroid receptors have an approximately 8S sedimentation coefficient that corresponds to an oligomeric structure of 250‐300 kd which includes a non‐hormone binding 90‐kd protein. A monoclonal antibody BF4 raised against the purified, molybdate‐stabilized, 8S progesterone receptor (8S‐PR) from chick oviduct, recognizes 8S forms of all steroid hormone receptors. BF4 was found specific for a 90‐kd protein present in great abundance in all chicken tissues, including that present in 8S‐forms of steroid receptors. Here, using immunological and biochemical techniques, we demonstrate that this ubiquitous BF4‐positive 90‐kd protein is in fact the chicken 90 kd heat‐shock protein (hsp 90): it increased in heat‐shocked chick embryo fibroblasts, and displayed identical migration in two‐dimensional gel electrophoresis and the same V8 peptide map as the already described hsp 90. We discuss the possibility that the interaction between hsp 90 and steroid hormone‐binding subunits may play a role in keeping the receptor in an inactive form.

Heat shock proteins: the search for functions.

“…A comparison of the HSP90 and kinaseassociated P90 by proteolytic digestion indicated the two were identical and this was confirmed when the P90 showed a positive response to our antibodies specific to the HSP90 (57). These results set the stage for the more recent revelations that HSP90 also forms a complex with steroid receptors (7,66,69). Both the receptor and kinase undergo intracellular translocations; in one case from cytoplasm to the nucleus and in the other (the kinase), from polysome to the cell's plasma membrane.…”

Different expression time of the 105‐kDa protein and 90‐kDa heat‐shock protein in rat testis

“…Among the heat-shock proteins, HSP90 is a cytoplasmic protein in unstressed cells. It has been shown that HSPBO is associated with steroid hormone receptors and regulates their activation mechanisms [2]. However, the physiological roles of heat shock proteins including HSP90 still remain to be elucidated.…”

Tetrameric structure of the nonactivated glucocorticoid receptor in cell extracts and intact cells

“…It contains only one hormone-binding potypeptide of Mr -I00000 per complex [7,8]. We now know that the heat shock protein hsp90 is a constituent of the heteromeric gtucocorticoid receptor structure [4,6,9,10]: it may be present as Abbreviations: DMS, dimethyl suberimidate; nt i, receptor of 'increased nuclear transfer'; PAGE, polyacrylamide gel electrophoresis a dimer [5,11,12]. The involvement of other molecular components is less clear.…”