FK506-binding Proteins 51 and 52 Differentially Regulate Dynein Interaction and Nuclear Translocation of the Glucocorticoid Receptor in Mammalian Cells

Abstract

We used a cellular system to elucidate the molecular determinants of the large immunophilin FK506-binding proteins (FKBP)51 and -52 for their action on the glucocorticoid receptor in mammalian cells. Increasing the levels of FKBP51 reduced the transcriptional activity of the receptor, as reported. Elevated levels of FKBP52 per se showed no effect but mitigated the inhibition of the receptor induced by FKBP51. We discovered that nuclear translocation of the glucocorticoid receptor was delayed by FKBP51. This correlates with the reduced interaction of FKBP51 with the motor protein dynein compared with FKBP52. From mutational analyses, we concluded that three features of the immunophilins are required for efficient receptor signaling in mammalian cells: hsp90 interaction, dynein association, and peptidylprolyl isomerase (PPIase) enzyme activity. The relevance of dynein for receptor function was substantiated by several experiments: 1) coexpression of dynamitin, which disrupts the transport complex and reduces receptor activity; 2) coexpression of the PPIase domain fragment of FKBP52, which is known to disrupt interaction of the receptor to dynein and reduce glucocorticoid receptor function, in contrast to the corresponding fragment of FKBP51; and 3) swapping of the PPIase domains FKBP51 and FKBP52, which reverses the respective activity. We concluded from our results that the mechanisms of the regulatory system FKBP51/FKBP52 discovered in yeast also operate in mammals to modulate hormone binding of the receptor. In addition, differential regulation of dynein association and nuclear translocation contributes to the effects of the two immunophilins on the glucocorticoid receptor in mammals.

Hpa Axis Related Genes and Response to Psychological Therapies: Genetics and Epigenetics

“…Termination of this response involves binding of glucocorticoids (i.e., cortisol) at the glucocorticoid receptor. FK506‐binding protein 51( FKBP5 ) acts as a functional negative regulator of glucocorticoid receptor sensitivity by reducing binding affinity4 and restricting nuclear translocation 5…”

The activity of the glucocorticoid receptor is regulated by SUMO conjugation to FKBP51

“…32 Upon hormone stimulation, there is a switch from FKBP51 to the closely related TPR protein, FKBP52, which positively regulates GR activity. 5,7,8 Therefore, we analyzed whether impairment of SUMO conjugation to FKBP51 alters the cochaperone composition of this complex. Figure 5d shows that wt FKBP51 and not K422R mutant is associated to the GR, thus corroborating our previous results.…”

“…5,32 Therefore, the fact that impairment of FKBP51 SUMOylation prevents both FKBP51 binding to Hsp90 and its inhibitory effect on GR activity while promotes FKBP52 recruitment and GR nuclear translocation provides a mechanistic explanation, suggesting that SUMO conjugation to FKBP51 underlies its preferential recruitment to the GR chaperone complex, which in turn determines the final outcome of GR signaling. Interestingly, we found through in silico analysis that FKBP52 has SUMO conjugation consensus and non-consensus sites.…”

“…3,4 Through its interaction with Hsp90, FKBP51 is recruited to the GR heterocomplex to finally inhibit GR activity. 5 Therefore, FKBP51 is critical for GR in vivo function and a key mediator during stress. 6 Ligand binding to the GR induces an exchange between FKBP51 and the closely related TPR protein FKBP52, 7 which in turn enhances GR activity.…”

Dissecting the molecular mechanisms of gene x environment interactions: implications for diagnosis and treatment of stress-related psychiatric disorders

“…It is part of the GR complex (Grad & Picard, 2007). When FKBP5 is bound to the complex, the GR has low affinity to cortisol and does not translocate readily to the nucleus (Davies, Ning, & Sanchez, 2002; Wochnik et al, 2005). FKBP5 is also a target of GR activation, and its mRNA and protein are induced by cortisol.…”