p75, a Member of the Heat Shock Protein Family, Undergoes Tyrosine Phosphorylation in Response to Oxidative Stress

doi:10.1074/jbc.272.1.657

p75, a Member of the Heat Shock Protein Family, Undergoes Tyrosine Phosphorylation in Response to Oxidative Stress*

From the ^‡ Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel and
^§ IV Abteilung Medizinische Klinik und Poliklinik, Eberhard-Karis Universitat, Otfried-Muller Strasse 10, 72076 Tubingen, Germany

^¶ Incumbent of the Philip Harris and Gerald Ronson Career Development Chair in Diabetes Research. To whom correspondence should be addressed. Tel.: 972-89-342-380; Fax: 972-89-344-125; E-mail: lizick{at}weizmann.weizmann.ac.il.

Abstract

The combination of H₂O₂ and vanadate generates aqueous peroxovanadium (pV) species, which are effective cell-permeable oxidants, and potent inhibitors of protein-tyrosine phosphatases. As a result, treatment of intact cells with pV compounds significantly enhances protein Tyr phosphorylation. Here we demonstrate that treatment of intact rat hepatoma Fao cells with pV markedly enhances Tyr phosphorylation of a 75-kDa protein, termed pp75. Amino-terminal sequencing of pp75 revealed that this protein is a member of the 70-75-kDa heat shock protein family, which includes PBP-74, glucose-related protein (GRP)-75, and mortalin. Tyr phosphorylation of pp75 is selective, because other proteins that belong to the heat shock protein 70 family, such as GRP-72, Bip (GRP-78), and HSC-70 fail to undergo Tyr phosphorylation when cells are treated with pV. Our findings suggest that heat shock proteins such as pp75 may undergo tyrosine phosphorylation when intact cells are subjected to oxidative stress induced by pV compounds.

Footnotes

↵* This work was supported by Grant I-160-054.02/90 from the German-Israeli Foundation and a grant from the Kekst Foundation. 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.
↵¹ The abbreviations used are:

pV

peroxovanadium

PTK

protein-tyrosine kinase

PTP

protein-tyrosine phosphatase

IRS

insulin receptor substrate

GRP

glucose-regulated protein

hsp

heat shock protein

PAGE

polyacrylamide gel electrophoresis
- Received September 3, 1996.