Hsp70 Prevents Activation of Stress Kinases

doi:10.1074/jbc.272.29.18033

Hsp70 Prevents Activation of Stress Kinases

A NOVEL PATHWAY OF CELLULAR THERMOTOLERANCE*

From the ^‡Boston Biomedical Research Institute, Boston, Massachusetts 02114, the ^§Medical Radiology Research Center, 249020 Obninsk, Russia, ^‖Biotechnology Research Institute, Montreal H4P 2R2, Quebec, Canada, and the ^**Dana Farber Cancer Institute, Boston, Massachusetts 02115

Abstract

Harmful conditions including heat shock, oxidative stress, UV, and so forth cause programmed cell death, whose triggering requires activation of the Jun N-terminal kinase, JNK. High levels of Hsp72, a heat-inducible member of Hsp70 family, protect cells against a variety of stresses by a mechanism that is unclear at present. Here we report that elevated levels of Hsp72 inhibit a signal transduction pathway leading to programmed cell death by preventing stress-induced activation of JNK. Stress-induced activation of another stress-kinase, p38 (HOG1), is also blocked when the level of Hsp72 is increased. Similarly, addition of a purified recombinant Hsp72 to a crude cell lysate reduced p38 kinase activation, while depletion of the whole family of Hsp70 proteins with a monoclonal antibody enhanced such activation. In addition, we have found that accumulation of abnormal proteins in cells upon incubation with amino acid analogs causes activation of JNK and p38 kinases, which can be prevented by overproduction of Hsp72. Taken together, these data suggest that, in regulation of JNK and p38 kinases, Hsp70 serves as a “sensor” of the build-up of abnormal proteins after heat shock and other stresses. The inhibitory effect of an increased level of Hsp70 on JNK appears to be a major contributor to acquired thermotolerance in mammalian cells.

Footnotes

↵* This work was supported in part by National Institutes of Health Grant RO1 (to M. Y. S.), by a Medical Foundation Grant (to M. Y. S.), and by the Yamagiva-Yoshida Grant from UICC (to V. L. G.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¶ Contributed equally to this study.
↵‡ To whom correspondence should be addressed: Boston Biomedical Research Institute, 20 Stanford St., Boston, MA 02114. Tel.: 617-742-2010 (ext. 312); Fax: 617-523-6649; E-mail:sherman{at}bbri.harvard.edu.
↵1 The abbreviations used are: JNK, Jun N-terminal kinase; MTT, 3-[4,5-dimethylthiasol-2-yl]-2,5-diphenyltetrasolium bromide; PARP, poly(ADP-ribose) polymerase; TNF, tumor necrosis factor; GFP, green fluorescent protein; IL, interleukin.
↵2 D. D. Mosser, submitted for publication.
↵3 S. Rits, unpublished data.
↵4 V. L. Gabai, manuscript in preparation.
- Received March 14, 1997.
- Revision received April 17, 1997.