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Modulation of HSP70 GlcNAc-directed lectin activity by glucose availability and utilization
Céline Guinez1, Marie-Estelle Losfeld, René Cacan
1UMR 8576/CNRS, Glycobiologie Structurale et Fonctionnelle, IFR 118, Bâtiment C9, 59655 Villeneuve d'Ascq, France.
Glycobiology
|September 24, 2005
Summary
Heat shock proteins (HSPs) like Hsp70 and Hsc70 bind O-GlcNAc, a sugar modification. Their binding activity changes with glucose levels, impacting protein quality control.
Area of Science:
- Molecular Biology
- Cellular Biology
- Biochemistry
Background:
- Protein quality control is crucial for cellular health, primarily mediated by heat shock proteins (HSPs).
- The precise mechanisms by which HSPs regulate protein degradation remain incompletely understood.
- O-GlcNAc glycosylation, a post-translational modification in the cytosol and nucleus, is linked to glucose metabolism and its role in protein stability is under investigation.
Purpose of the Study:
- To investigate the relationship between the O-GlcNAc binding activity of Hsp70 and Hsc70 and glucose availability.
- To elucidate the role of glucose metabolism in modulating the lectin activity of HSP70 family members.
- To determine if Hsp70's O-GlcNAc binding is regulated by its own glycosylation.
Main Methods:
- Assessed the GlcNAc-binding (lectin) activity of Hsp70 and Hsc70 under varying glucose concentrations.
- Utilized glucose utilization inhibitors (2DG) and glucose transport inhibitors (CytB) to manipulate cellular glucose levels.
- Examined the O-GlcNAc modification status of HSP70 family members.
Main Results:
- Low glucose concentrations, or inhibition of glucose utilization/transport, significantly increased Hsp70 and Hsc70 lectin activities.
- Hsp70 lost its lectin activity at physiological glucose concentrations (>5 mM), while Hsc70 maintained maximal activity around 5 mM and at high glucose levels.
- HSP70 family members do not appear to regulate their GlcNAc-binding properties via self-O-GlcNAc glycosylation.
Conclusions:
- Glucose availability dynamically regulates the O-GlcNAc binding activity of Hsp70 and Hsc70, suggesting a role in glucose-dependent protein quality control.
- Differential responses of Hsp70 and Hsc70 to glucose levels indicate distinct regulatory roles in cellular proteostasis.
- The findings highlight a novel link between glucose metabolism, HSP lectin activity, and protein degradation pathways.
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