Estrogenic regulation of murine uterine 90-kilodalton heat shock protein gene expression

Regulation of glucose responsive protein (GRP) gene expression by insulin

While screening for insulin-induced genes, we identified two members of a family of stress-induced genes referred to as glucose-regulated proteins (GRPs). GRPs are members of the stress-responsive superfamily of genes which also includes heat shock proteins (HSPs). The GRP proteins are not normally heat-inducible, but are overproduced when cells are starved of glucose. The two major GRP proteins, GRP78 and GRP94, are highly conserved among vertebrates. We have found that physiological concentrations of insulin stimulate the transcription of GRP78 and GRP94 in rat H4IIE hepatoma cells. The regulation of GRP78 transcription was rapid, with the first induction within minutes, and a further induction after several hours, and both occurred in the presence of glucose. GRP78 transcription was more greatly induced by insulin in the presence of SB202190, a specific p38-MAPK inhibitor. Transcription of GRP94 was also induced, but only after several hours. Calcimycin (A23187) and anisomycin were used to induce endoplasmic reticulum (ER)/cellular stress, and both induced GRP78 and GRP94 transcription.

Do heat shock proteins have a role in breast cancer?

It is clear therefore that hsps are overexpressed in patients with malignant tumours compared with healthy controls and this overexpression does show some correlation with disease features. Furthermore, expression of hsps has been reported on the cell surface of tumour cell lines. This could be associated with the immune response which has been reported with hsp90 and which also correlates with some disease features. It now appears that hsps may be involved in the presentation of tumour antigens leading to the possibility of hsps being used as a means of therapy. Hsp65 expression has not been investigated in patients with breast cancer. However, transfection of bacterial hsp65 into a tumour cell line resulted in the hsp65-expressing tumour cells losing their tumorigenicity in mice (Lukacs et al., 1993). Thus, hsps and the immune response to them are of interest as diagnostic and prognostic tools as well as a novel form of immunotherapy.

Steroid hormone regulation of the Achlya ambisexualis 85-kilodalton heat shock protein, a component of the Achlya steroid receptor complex

The steroid hormone antheridiol regulates sexual development in the fungus Achlya ambisexualis. Analyses of in vivo-labeled proteins from hormone-treated cells revealed that one of the characteristic antheridiol-induced proteins appeared to be very similar to the Achyla 85-kilodalton (kDa) heat shock protein. Analysis of in vitro translation products of RNA isolated from control, heat-shocked, or hormone-treated cells demonstrated an increased accumulation of mRNA encoding a similar 85-kDa protein in both the heat-shocked and hormone-treated cells. Northern (RNA) blot analyses with a Drosophila melanogaster hsp83 probe indicated that a mRNA species of approximately 2.8 kilobases was substantially enriched in both heat-shocked and hormone-treated cells. The monoclonal antibody AC88, which recognizes the non-hormone-binding component of the Achyla steroid receptor, cross-reacted with Achlya hsp85 in cytosols from heat-shocked cells. This monoclonal antibody also recognized both the hormone-induced and heat shock-induced 85-kDa in vitro translation products. Taken together, these data suggest that similar or identical 85-kDa proteins are independently regulated by the steroid hormone antheridiol and by heat shock and that this protein is part of the Achyla steroid receptor complex. Our results demonstrate that the association of hsp90 family proteins with steroid receptors observed in mammals and birds extends also to the eucaryotic microbes and suggest that this association may have evolved early in steroid-responsive systems.

Steroid hormone regulation of the Achlya ambisexualis 85-kilodalton heat shock protein, a component of the Achlya steroid receptor complex

The steroid hormone antheridiol regulates sexual development in the fungus Achlya ambisexualis. Analyses of in vivo-labeled proteins from hormone-treated cells revealed that one of the characteristic antheridiol-induced proteins appeared to be very similar to the Achyla 85-kilodalton (kDa) heat shock protein. Analysis of in vitro translation products of RNA isolated from control, heat-shocked, or hormone-treated cells demonstrated an increased accumulation of mRNA encoding a similar 85-kDa protein in both the heat-shocked and hormone-treated cells. Northern (RNA) blot analyses with a Drosophila melanogaster hsp83 probe indicated that a mRNA species of approximately 2.8 kilobases was substantially enriched in both heat-shocked and hormone-treated cells. The monoclonal antibody AC88, which recognizes the non-hormone-binding component of the Achyla steroid receptor, cross-reacted with Achlya hsp85 in cytosols from heat-shocked cells. This monoclonal antibody also recognized both the hormone-induced and heat shock-induced 85-kDa in vitro translation products. Taken together, these data suggest that similar or identical 85-kDa proteins are independently regulated by the steroid hormone antheridiol and by heat shock and that this protein is part of the Achyla steroid receptor complex. Our results demonstrate that the association of hsp90 family proteins with steroid receptors observed in mammals and birds extends also to the eucaryotic microbes and suggest that this association may have evolved early in steroid-responsive systems.