Affiliations 

  • 1 Molecular Biology Course, Graduate School of Science and Engineering, Saitama University, Saitama, Japan nakamoto@mail.saitama-u.ac.jp
  • 2 Molecular Biology Course, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
  • 3 Biomolecular Characterization Unit, RIKEN Center for Sustainable Resource Science, Wako, Japan
  • 4 Drug and Herbal Research Centre, Faculty of Pharmacy, Universiti Kebangsaan Malaysia, Kuala Lumpur, Malaysia
  • 5 Department of Cell and Developmental Biology, Graduate School of Biostudies, Kyoto University, Kyoto, Japan
Biochem. J., 2018 08 16;475(15):2559-2576.
PMID: 30045873 DOI: 10.1042/BCJ20180230

Abstract

Hsp90 is an ATP-dependent molecular chaperone that assists folding and conformational maturation/maintenance of many proteins. It is a potential cancer drug target because it chaperones oncoproteins. A prokaryotic homolog of Hsp90 (HtpG) is essential for thermo-tolerance in some bacteria and virulence of zoonotic pathogens. To identify a new class of small molecules which target prokaryotic and eukaryotic Hsp90s, we studied the effects of a naturally occurring cyclic sesquiterpene, zerumbone, which inhibits proliferation of a wide variety of tumor cells, on the activity of Hsp90. Zerumbone enhanced the ATPase activity of cyanobacterial Hsp90 (Hsp90SE), yeast Hsp90, and human Hsp90α. It also enhanced the catalytic efficiency of Hsp90SE by greatly increasing kcat Mass analysis showed that zerumbone binds to cysteine side chains of Hsp90SE covalently. Mutational studies identified 3 cysteine residues (one per each domain of Hsp90SE) that are involved in the enhancement, suggesting the presence of allosteric sites in the middle and C-terminal domains of Hsp90SE Treatment of cyanobacterial cells with zerumbone caused them to become very temperature-sensitive, a phenotype reminiscent of cyanobacterial Hsp90 mutants, and also decreased the cellular level of linker polypeptides that are clients for Hsp90SE Zerumbone showed cellular toxicity on cancer-derived mammalian cells by inducing apoptosis. In addition, zerumbone inhibited the binding of Hsp90/Cdc37 to client kinases. Altogether, we conclude that modification of cysteine residues of Hsp90 by zerumbone enhances its ATPase activity and inhibits physiological Hsp90 function. The activation of Hsp90 may provide new strategies to inhibit its chaperone function in cells.

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.