Cyclophilin 40 : an Hsp90-cochaperone associated with apo-steroid receptors

Tom Ratajczak, B.K. Ward, Carmel Cluning, Rudi Allan

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


Cyclophilin 40, a divergent loop cyclophilin first identified in association with the estrogen receptor α, contains a C-terminal tetratricopeptide repeat domain through which it shares structural identity with FK506-binding protein 52 (FKBP52) and other partner cochaperones in steroid receptor-heat shock protein 90 (Hsp90) complexes. By dynamically competing for Hsp90 interaction, the cochaperones allow the receptors to establish distinct Hsp90-chaperone complexes, with the potential to exert tissue-specific control over receptor activity. Cyclophilin 40 regulates Hsp90 ATPase activity during receptor-Hsp90 assembly. Functional deletion of the cyclophilin 40 yeast homologue, Cpr7, adversely affected estrogen receptor α and glucocorticoid receptor activity that could be fully restored, either with wild type Cpr7 or Cpr7 with a cyclophilin domain lacking isomerase activity. We draw parallels with the mechanism already established for FKBP52 and propose that the cyclophilin 40 divergent loop interfaces with a contact surface on the steroid receptor ligand-binding domain to achieve an optimal orientation for receptor activity.
Original languageEnglish
Pages (from-to)1652-1655
JournalThe International Journal of Biochemistry & Cell Biology
Issue number8-9
Publication statusPublished - 2009


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