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Protein ubiquitination is modulated by O-GlcNAc glycosylation

Céline Guinez1, Anne-Marie Mir, Vanessa Dehennaut

  • 1UMR USTL/CNRS 8576, Laboratoire de Glycobiologie Structurale et Fonctionnelle, IFR 147, 59655 Villeneuve d'Ascq, France.

FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology
|April 25, 2008
PubMed

Insights

O-linked N-acetylglucosamine (O-GlcNAc) modification regulates protein ubiquitination, not just protects against degradation. This study reveals O-GlcNAc influences ubiquitination, with the E1 enzyme potentially linking these crucial post-translational modifications.

Area of Science:

  • Cellular Biology
  • Biochemistry
  • Post-Translational Modifications

Background:

  • O-linked N-acetylglucosamine (O-GlcNAc) is a dynamic post-translational modification on cytosolic and nuclear proteins.
  • Its precise biological functions, particularly its relationship with other modifications like ubiquitination, remain largely elusive.
  • Speculation suggests O-GlcNAc may protect proteins from proteasomal degradation.

Purpose of the Study:

  • To investigate the interplay between O-GlcNAc modification and the ubiquitin-proteasome system.
  • To determine if O-GlcNAc influences protein stability or ubiquitination pathways.
  • To identify potential molecular links between O-GlcNAc and ubiquitination.

Main Methods:

  • Analysis of O-GlcNAc and ubiquitinated protein levels under thermal stress and proteasome inhibition.
  • Pharmacological manipulation of O-GlcNAc levels using glucosamine, PUGNAc, forskolin, and glucose deprivation.
  • Targeted RNA interference to knockdown O-GlcNAc transferase.
  • Investigation of O-GlcNAc modification on the ubiquitin-activating enzyme E1 and its interaction with Hsp70.

Main Results:

  • Both O-GlcNAc and ubiquitination increased after thermal stress, but O-GlcNAc-modified proteins were not stabilized by proteasome inhibition.
  • Elevated O-GlcNAc levels enhanced ubiquitination, while reduced levels decreased it.
  • Knockdown of O-GlcNAc transferase decreased ubiquitination and cell thermotolerance.
  • The ubiquitin-activating enzyme E1 was found to be O-GlcNAc modified, with its glycosylation and Hsp70 interaction varying with culture conditions.

Conclusions:

  • O-GlcNAc and ubiquitin are not antagonistic but rather O-GlcNAc appears to regulate ubiquitination.
  • The ubiquitin-activating enzyme E1 is a potential molecular link between O-GlcNAc and ubiquitination pathways.
  • These findings provide new insights into the regulatory roles of O-GlcNAc in cellular stress responses and protein turnover.

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