[Functional interaction of HSP90 with steroid receptors]

Hsp90 (Heat Shock Protein 90) is a component of the inactive and metastable hetero-oligomeric structure of steroid receptors. Recent data on Hsp90 structure and function as a stress protein and dedicated molecular chaperone are here reviewed with a particular focus on Hsp90 chaperone cycle interfering with steroid receptor action. The dual role of Hsp90 as a positive and negative modulator of steroid receptor function is considered along the activation-desactivation process of the receptors. It is proposed that Hsp90 chaperone machinery assists the receptor during its synthesis thus avoiding collapse and facilitating an open structure able to bind ligand efficiently. Moreover, it is suggested that Hsp90 may help the folding of the hydrophobic core of the receptor around the ligand and finally Hsp90 may chaperone the receptor after the dissociation of the ligand.