Phosphorylation status of glucocorticoid receptor, heat shock protein 70, cytochrome c and Bax in lymphocytes of euthymic, depressed and manic bipolar patients

Abstract

Bipolar disorder (BD), a severe mental illness, has been correlated with alterations in glucocorticoid receptor (GR) signaling. Since it is phosphorylated GR that contributes to receptor function and determines its transcriptional activity, the Ser211 being a biomarker for activated GR in vivo, it is pertinent that we seek to determine the putative role of the total phosphorylation status of GR and site-specific phosphorylation at serine 211 (S211) in BD and their possible association with parameters of apoptosis. In lymphocytes from 48 BD patients under multiple psychotropic therapy and 20 healthy subjects, we measured whole cell GR, total GR phosphorylation, and phosphorylation of GR at serine 211 in nucleus, using immunoprecipitation, phosphospecific antibody and Western-blot analysis. Cytosolic cytochrome c and Bax and whole cell HSP70 were determined by immunoblot analysis. One-way ANOVA statistical analysis was carried out. Total phosphorylated GR was lower (P<0.001) while the GR S211 was higher (P<0.001) in all BD patients as compared to healthy subjects. HSP70 was reduced in euthymic (P<0.05), depressed (P<0.001) and manic (P<0.001) as compared to healthy subjects. Cytochrome c was higher in all-patient groups as compared to healthy subjects, however without reaching statistical significance (P>0.05). Bax levels were lower in the cytosolic fraction of all three BD groups. We provide the first evidence of altered GR phosphorylation joined with signs of apoptosis in lymphocytes of BD patients and suggest that the phosphorylation status of GR may play a role in the pathophysiology of bipolar disorder.