Genetic variations of heat shock protein 84 in mice mediate cellular glucocorticoid response

Heat shock protein 90 (Hsp90), encoded by hsp84 and hsp86 in mice, has been confirmed to modulate glucocorticoid receptor (GR) function; however, the contribution of Hsp90 in glucocorticoid (GC) sensibility/resistance has received less attention. Previously, we found that genetic variations of Hsp84 are related to differences in the in vivo GC-GR responses between BALB/c and C57BL/6 mice suffering from traumatic injury. To evaluate the modulation of Hsp84 polymorphisms on the GC response, we used a cellular heat-stress injury (HSI) model combined with a transgene-plasmid infection approach and assessed HSI-induced cellular damage and GR nuclear translocation, with or without dexamethasone pretreatment. We demonstrated that after HSI, fibroblasts from the C57BL/6 line exhibit higher cellular survival, higher nuclear GR levels and lower lactate dehydrogenase activity compared to those from the BALB/c line. We showed that dexamethasone-rescued HSI-induced damage is accompanied by increasing nuclear GR levels in both lines. Importantly, this protection against HSI was greater in C57BL/6 fibroblasts and was resistant to geldanamycin, a selective inhibitor of Hsp90. Importantly, transfection of the hsp84-transgene from C57BL/6 mice increased the nuclear GR levels and lessened HSI-induced damage in BALB/c fibroblasts. Our data thereby demonstrate that Hsp84 from C57BL/6 mice modulates higher cellular GC-GR responsiveness.