The interaction and cellular localization of HSP27 and ERβ are modulated by 17β-estradiol and HSP27 phosphorylation

Recently, we identified heat shock protein 27 (HSP27) as an estrogen receptor-β (ERβ) associated protein that acts as a co-repressor of estrogen signaling and serves as a biomarker of atherosclerosis. In this study, we sought to further characterize the subcellular interaction of HSP27 and ERβ, as well as explore the factors that may modulate this interaction. In vitro we determined that phosphorylated HSP27 is retained in the cytoplasm after treatment with 17β-estradiol and to a lesser extent with heat shock. Under all experimental conditions ERβ was found to be slightly more abundant in the cytoplasm compared to the nucleus. HSP27 and ERβ associate in both the cytoplasm and nucleus, however, co-localization studies reveal that in the presence of 17β-estradiol, a significant portion of this interaction occurs outside of the nucleus. These data highlight an extranuclear interaction between ERβ and HSP27 that may be of potential importance in modulating estrogen signaling.