Artificial Accelerators of the Molecular Chaperone Hsp90 Facilitate Rate‐Limiting Conformational Transitions

Abstract

The molecular chaperone Hsp90 undergoes an ATP-driven cycle of conformational changes in which large structural rearrangements precede ATP hydrolysis. Well-established small-molecule inhibitors of Hsp90 compete with ATP-binding. We wondered whether compounds exist that can accelerate the conformational cycle. In a FRET-based screen reporting on conformational rearrangements in Hsp90 we identified compounds. We elucidated their mode of action and showed that they can overcome the intrinsic inhibition in Hsp90 which prevents these rearrangements. The mode of action is similar to that of the co-chaperone Aha1 which accelerates the Hsp90 ATPase. However, while the two identified compounds influence conformational changes, they target different aspects of the structural transitions. Also, the binding site determined by NMR spectroscopy is distinct. This study demonstrates that small molecules are capable of triggering specific rate-limiting transitions in Hsp90 by mechanisms similar to those in protein cofactors.

Activation of Hsp90 Enzymatic Activity and Conformational Dynamics through Rationally Designed Allosteric Ligands

“…Analysis of the interaction of compounds 4-16 with Hsp90 revealed that most of them act as stimulators, rather than inhibitors, of the ATPase activity, a feature that was totally unprecedented, until very recently [27] activators were found by large scale screening. We would like to underline that the case we present here is the first one where these results are obtained using a rational design approach .…”

Chaperones and chaperone–substrate complexes: Dynamic playgrounds for NMR spectroscopists

“…To investigate the interaction of Tah1 with the C-terminus of Hsp90, the structure of the complex was solved by solution NMR methods to medium [202] and high resolution [203]. Hsp90's role in the interaction with cancer related proteins makes it an attractive target for small molecule inhibitors, which were screened for by NMR spectroscopy [204,205].…”

Allosteric Regulation of Hsp90α’s Activity by Small Molecules Targeting the Middle Domain of the Chaperone

“…Multiple exogenous small molecules targeting the different structural domains of Hsp90 have been developed. They regulate Hsp90's function mainly via five ways: ATP competitive inhibitors, which block the access of ATP to the Hsp90's NTD (Prodromou, 2009;Roe et al, 1999;Sidera and Patsavoudi, 2014;Verma et al, 2016); inhibitors binding to the Hsp90's NTD and interfering with the interactions between Hsp90 and co-chaperones such as p23 and Cdc37 (Li et al, 2009(Li et al, , 2018Verma et al, 2016); compounds interacting with Hsp90's CTD and inhibiting its dimerization (Garg et al, 2016;Verma et al, 2016); allosteric activators binding to either the N-terminal domain or the interface region in between the middle domain and the C-terminal domain of Hsp90 (Bassanini et al, 2018;D'Annessa et al, 2017;Ferraro et al, 2019;Sattin et al, 2015;Yokoyama et al, 2015;Zierer et al, 2016;Zierer et al, 2014); and small molecules covalently bonding to the cysteine residue in the middle domain of Hsp90 (Li et al, 2016;Nakamoto et al, 2018;Zhang et al, 2018). Among the reported chemical compounds targeting Hsp90, ATP competitive inhibitors form a dominant group, and quite a few compounds from this group are undergoing clinical trials for the treatment of cancer (Nabi et al, 2018;Sidera and Patsavoudi, 2014;Tatokoro et al, 2015).…”