Systematic Proteomic Identification of the Heat Shock Proteins (Hsp) that Interact with Estrogen Receptor Alpha (ERα) and Biochemical Characterization of the ERα-Hsp70 Interaction

Abstract

Heat shock proteins (Hsps) are known to associate with estrogen receptors (ER) and regulate ER-mediated cell proliferation. Historically, the studies in this area have focused on Hsp90. However, some critical aspects of the Hsp-ERα interactions remain unclear. For example, we do not know which Hsps are the major or minor ERα interactants and whether or not different Hsp isoforms associate equally with ERα. In the present study, through a quantitative proteomic method we found that 21 Hsps and 3 Hsp cochaperones were associated with ERα in human 293T cells that were cultured in a medium containing necessary elements for cell proliferation. Four Hsp70s (Hsp70-1, Hsc70, Grp75, and Grp78) were the most abundant Hsps identified to associate with ERα, followed by two Hsp90s (Hsp90α and Hsp90β) and three Hsp110s (Hsp105, HspA4, and HspA4L). Hsp90α was found to be 2–3 times more abundant than Hsp90β in the ERα-containing complexes. Among the reported Hsp cochaperones, we detected prostaglandin E synthase 3 (p23), peptidyl-prolyl cis-trans isomerase FKBP5 (FKBP51), and E3 ubiquitin-protein ligase CHIP (CHIP). Studies with the two most abundant ERα-associated Hsps, Hsp70-1 and Hsc70, using human breast cancer MCF7 cells demonstrate that the two Hsps interacted with ERα in both the cytoplasm and nucleus when the cells were cultured in a medium supplemented with fetal bovine serum and phenol red. Interestingly, the ERα-Hsp70-1/Hsc70 interactions were detected only in the cytoplasm but not in the nucleus under hormone starvation conditions, and stimulation of the starved cells with 17β-estradiol (E2) did not change this. In addition, E2-treatment weakened the ERα-Hsc70 interaction but had no effect on the ERα-Hsp70-1 interaction. Further studies showed that significant portions of Hsp70-1 and Hsc70 were associated with transcriptionally active chromatin and inactive chromatin, and the two Hsps interacted with ERα in both forms of the chromatins in MCF7 cells.

The androgen receptor antagonist enzalutamide induces apoptosis, dysregulates the heat shock protein system, and diminishes the androgen receptor and estrogen receptor β1 expression in prostate cancer cells

“…Within the superfamily of HSPs, there are several receptor-associated members including HSP27, HSP40, HOP, HSP70, and HSP90. 55,56 Our data showed reduced levels of HSP27, HSP40, and HSP90β in the presence of enzalutamide, which may contribute to observed inhibition of AR and ERβ1 expression. HOP was suppressed only in LNCaP cells, potentially reflecting an individual cell-type response to enzalutamide.…”

Gender differences in trauma, shock and sepsis

“…The beneficial effects may be explained by the altered expression levels of heat shock proteins (HSPs) following estrogen administration. The main role of HSPs is to protect cells, and they therefore play an important role in protein folding, apoptosis and signaling [ 64 ]. Expression of HSP70 is increased in response to severe blood loss, subsequently leading to a reduced rate of myocardial necrosis [ 65 ].…”

FKBP4 is a malignant indicator in luminal A subtype of breast cancer

“…FK506-binding protein (FKBP) family in Homo sapiens (human) genomes has included 18 FKBPs up to date, which can target on various pathways in embryonic development, stress response, cardiac function, cancer tumorigenesis and neuronal function [15]. In breast cancer, FKBP5 is the most extensively studied protein among identified human FKBPs, which is demonstrated to interact with HSP90 to affect steroid hormone receptor function [16]. In colorectal cancer, silencing FKBP3 has been found to attenuate oxaliplatin resistance by regulation of the PTEN/AKT axis [17].…”