Heat Shock Protein 84 Forms a Complex with Mutant p53 Protein Predominantly within a Cytoplasmic Compartment of the Cell

Bahman Sepehrnia; I. Benjamin Paz; Gargi Dasgupta; Jamil Momand

doi:10.1074/jbc.271.25.15084

Heat Shock Protein 84 Forms a Complex with Mutant p53 Protein Predominantly within a Cytoplasmic Compartment of the Cell*

From the Department of Cell and Tumor Biology, City of Hope National Medical Center, Duarte, California 91010-0269

↵^‡ Edward Livingston Trudeau Scholar of the American Lung Association. To whom correspondence should be addressed. Tel.: 818-301-8878; Fax: 818-301-8972; E-mail, jmomand{at}smtplink.coh.org

Abstract

Cellular DNA damage results in the increased expression and accumulation of the p53 tumor suppressor protein within the nucleus which leads to cell cycle arrest or apoptosis. In some cases, however, wild-type p53 and some mutant forms of p53 reside in the cytoplasm of cancer cells. To understand the mechanism responsible for its cytoplasmic retention, studies were undertaken to determine if unique proteins form a complex with mutant p53 within the cytoplasm of transformed cells. One protein, with an apparent molecular mass of 92 kDa (p92), was observed to form a complex with a temperature-sensitive mutant p53 (TSp53^Val-135) in the cytoplasm of transformed rat embryo fibroblasts at the non-permissive temperature. p92 copurified with TSp53^Val-135 on a p53-specific immunoaffinity column and a gel filtration column. The protein was purified to homogeneity and identified as hsp84 by partial amino acid sequence analysis. hsp84 is a member of the hsp90 class of proteins. At the non-permissive temperature, TSp53^Val-135 and hsp84 colocalized in the cytoplasm near the nuclear envelope. At the permissive temperature, TSp53^Val-135 resides in the nucleus and expresses a “wild-type like” conformation. Under these conditions hsp84 continued to reside in the cytoplasm and little or no hsp84 formed a complex with p53. The results suggest that hsp84 binds mutant p53 in a spatial and/or conformation dependent manner.

Footnotes

↵* This project was funded by grants from the American Lung Association (RG 121) and the City of Hope Breast Cancer Initiative. 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.