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Glycobiology Advance Access published online on September 21, 2005
Glycobiology, doi:10.1093/glycob/cwj041
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© The Author 2005. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org
Received May 4, 2005
Revised September 7, 2005
Accepted September 14, 2005

Article

Modulation of HSP70 GlcNAc-directed lectin activity by glucose availability and utilisation

Céline Guinez 1, Marie-Estelle Losfeld 1, René Cacan 1, Jean-Claude Michalski 1, and Tony Lefebvre 1*

1 UMR 8576/CNRS, « Glycobiologie Structurale et Fonctionnelle », IFR 118, bâtiment C9, 59655 Villeneuve d’Ascq, France

* To whom correspondence should be addressed.
Tony Lefebvre, E-mail: tony.lefebvre{at}univ-lille1.fr


  Abstract

It is well-accepted that protein quality control (occurring either after protein synthesis or after cell damage) is mainly ensured by Heat Shock Proteins (HSP), but the mechanism by which HSP decides if the protein will be degraded or not is poorly understood. Within this framework, it has been hypothesized that O-GlcNAc, a cytosolic and nuclear-specific glycosylation whose functions remain unclear, could take a part in the protection of proteins against degradation by modifying both the proteins themselves and proteasome. Since the synthesis of O-GlcNAc is tightly correlated to glucose metabolism and Hsp70 was endowed with GlcNAc-binding property, we studied the relationship between GlcNAc-binding activity of both Hsp70 and Hsc70 (the nucleocytoplasmic forms of HSP70 family) and glucose availability and utilization. We thus demonstrated that low glucose concentration, inhibition of glucose utilisation with 2-deoxyglucose or inhibition of glucose transport with cytochalasin B led to an increase of Hsp70 and Hsc70 lectin activities. Interestingly the response of Hsp70 and Hsc70 lectin activities towards variations of glucose concentration appeared different: Hsp70 lost its lectin activity when glucose concentration was higher than 5 mM (i. e. physiological glucose concentration) in contrast to Hsc70 that exhibited a maximal lectin activity for glucose concentration nearby 5 mM and at high glucose concentrations. This work also demonstrates that HSP70 does not regulate its GlcNAc-binding properties through its own O-GlcNAc glycosylation.

Keywords: glucose/heat shock proteins/hexosamine biosynthetic pathway/lectin/O-GlcNAc.
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