The Identity of Proteins Associated with a Small Heat Shock Protein during Heat Stress in Vivo Indicates That These Chaperones Protect a Wide Range of Cellular Functions

Authors

Eman Basha, University of Arizona
Garrett J. Lee, University of Arizona
Linda A. Breci, University of Arizona
Andrew C. Hausrath, University of Arizona
Nicole R. Buan, University of Nebraska-LincolnFollow
Kim C. Giese, University of Arizona
Elizabeth Vierling, University of ArizonaFollow

Date of this Version

2-27-2004

Citation

Basha,E., Lee, G.J., Breci, L.A., Hausrath, A.C., Buan, N.R., Giese, K.C., and E. Vierling. 2004. The identity of proteins associated with a small heat shock protein during heat stress in vivo indicates that these chaperones protect a wide range of cellular functions. J. Biol. Chem. 279: 7566-75. PMID: 14662763

DOI 10.1074/jbc.M310684200

Comments

This is an Open Access article under the CC BY license.

Abstract

The small heat shock proteins (sHSPs) are a ubiquitous class of ATP-independent chaperones believed to prevent irreversible protein aggregation and to facilitate subsequent protein renaturation in cooperation with ATP-dependent chaperones. Although sHSP chaperone activity has been studied extensively in vitro, understanding the mechanism of sHSP function requires identification of proteins that are sHSP substrates in vivo. We have used both immunoprecipitation and affinity chromatography to recover 42 proteins that specifically interact with Synechocystis Hsp16.6 in vivo during heat treatment. These proteins can all be released from Hsp16.6 by the ATP-dependent activity of DnaK and cochaperones and are heat-labile. Thirteen of the putative substrate proteins were identified by mass spectrometry and reveal the potential for sHSPs to protect cellular functions as diverse as transcription, translation, cell signaling, and secondary metabolism. One of the putative substrates, serine esterase, was purified and tested directly for interaction with purified Hsp16.6. Hsp16.6 effectively formed soluble complexes with serine esterase in a heat-dependent fashion, thereby preventing formation of insoluble serine esterase aggregates. These data offer critical insights into the characteristics of native sHSP substrates and extend and provide in vivo support for the chaperone model of sHSP function.