Eléonore Lepvrier, Daniel Thomas and Cyrille Garnier* Pages 5 - 11 ( 7 )
Proposed models of the function of Hsp90 are characterised by high flexibility of the dimeric state and conformational changes regulated by both nucleotide binding and hydrolysis, and by co-chaperone interactions. In addition to its dimeric state, Hsp90 self-associates upon particular stimuli. The Hsp90 dimer is the building block up to the hexamer that we named “cosy nest”, and the dodecamer results from the association of two hexamers. Oligomers exhibit chaperone activity, but their exact mechanism of action has not yet been determined. One of the best ways to elucidate how oligomers might operate is to study their interactions with co-chaperone proteins known to regulate the Hsp90 chaperone cycle, such as p23 and Aha1. In this review, we summarise recent results and conclude that Hsp90 oligomers are key players in the chaperone cycle. Crucible-shaped quaternary structures likely provide an ideal environment for client protein accommodation and folding, as is the case for other Hsp families. Confirmation of the involvement of Hsp90 oligomers in the chaperone cycle and a better understanding of their functionality will allow us to address some of the more enigmatic aspects of Hsp90 activity. Utilising this knowledge, future work will highlight how Hsp90 oligomers and co-chaperones cooperate to build the structures required to fold or refold numerous different client proteins.
Hsp90, chaperone cycle, oligomers, co-chaperone regulation, self-association, protein flexibility.
Structure et Dynamique des Macromolecules, UMR-CNRS 6026, Interactions Cellulaires et Moleculaires Universite de Rennes 1, Campus Beaulieu, 35042 Rennes Cedex, Structure et Dynamique des Macromolecules, UMR-CNRS 6026, Interactions Cellulaires et Moleculaires Universite de Rennes 1, Campus Beaulieu, 35042 Rennes Cedex, Mecanismes Moleculaires dans les Demences Neurodegeneratives Universite de Montpellier, EPHE, INSERM, U1198, F-34095 Montpellier