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

Hsp90 is a molecular chaperone of pivotal importance
for multiple cell pathways. ATP-regulated internal dynamics
are critical for its function and current pharmacological
approaches block the chaperone with ATP-competitive
inhibitors. Herein, a general approach to perturb Hsp90
through design of new allosteric ligands aimed at modulating
its functional dynamics is proposed. Based on the characterization
of a first set of 2-phenylbenzofurans showing
stimulatory effects on Hsp90 ATPase and conformational dynamics,
new ligands were developed that activate Hsp90 by
targeting an allosteric site, located 65 æ from the active site.
Specifically, analysis of protein responses to first-generation
activators was exploited to guide the design of novel derivatives
with improved ability to stimulate ATP hydrolysis. The
molecules’ effects on Hsp90 enzymatic, conformational, cochaperone
and client-binding properties were characterized
through biochemical, biophysical and cellular approaches.
These designed probes act as allosteric activators of the
chaperone and affect the viability of cancer cell lines for
which proper functioning of Hsp90 is necessary.