Article

Interaction between O-GlcNAc Modification and Tyrosine Phosphorylation of Prohibitin: Implication for a Novel Binary Switch

Department of Internal Medicine, University of Manitoba, Winnipeg, Manitoba, Canada.
PLoS ONE (Impact Factor: 3.23). 02/2009; 4(2):e4586. DOI: 10.1371/journal.pone.0004586
Source: PubMed

ABSTRACT

Prohibitin (PHB or PHB1) is an evolutionarily conserved, multifunctional protein which is present in various cellular compartments including the plasma membrane. However, mechanisms involved in various functions of PHB are not fully explored yet. Here we report for the first time that PHB interacts with O-linked beta-N-acetylglucosamine transferase (O-GlcNAc transferase, OGT) and is O-GlcNAc modified; and also undergoes tyrosine phosphorylation in response to insulin. Tyrosine 114 (Tyr114) and tyrosine 259 (Tyr259) in PHB are in the close proximity of potential O-GlcNAc sites serine 121 (Ser121) and threonine 258 (Thr258) respectively. Substitution of Tyr114 and Tyr259 residues in PHB with phenylalanine by site-directed mutagenesis results in reduced tyrosine phosphorylation as well as reduced O-GlcNAc modification of PHB. Surprisingly, this also resulted in enhanced tyrosine phosphorylation and activity of OGT. This is attributed to the presence of similar tyrosine motifs in PHB and OGT. Substitution of Ser121 and Thr258 with alanine and isoleucine respectively resulted in attenuation of O-GlcNAc modification and increased tyrosine phosphorylation of PHB suggesting an association between these two dynamic modifications. Sequence analysis of O-GlcNAc modified proteins having known O-GlcNAc modification site(s) or known tyrosine phosphorylation site(s) revealed a strong potential association between these two posttranslational modifications in various proteins. We speculate that O-GlcNAc modification and tyrosine phosphorylation of PHB play an important role in tyrosine kinase signaling pathways including insulin, growth factors and immune receptors signaling. In addition, we propose that O-GlcNAc modification and tyrosine phosphorylation is a novel previously unidentified binary switch which may provide new mechanistic insights into cell signaling pathways and is open for direct experimental examination.

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Available from: Sudharsana Rao Ande
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    • "In many ways, O-GlcNAcylation is similar to O-phosphorylation: for instance, like phosphate, N-acetylglucosamine moiety can be attached and removed rapidly in response to internal or environmental changes [4,20,21]; and both O-GlcNAcylation and O-phosphorylation occur on Ser and/or Thr residues, which hints O-GlcNAcylation has a direct competition with O-phosphorylation [1]. Furthermore recent studies have revealed that besides phosphorylation on serine/threonine, also about 68.02% of the O-GlcNAcylated proteins are known to be tyrosine phosphorylated [22-24]. Thus, an increasing number of phosphorylated proteins have been found in mitochondria, and the site-specific interplay between O-phosphorylation and O-GlcNAcylation has been widely recognized. "
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    • "mSin3A and HDAC1 are O-GlcNAcylated in HepG2 liver carcinoma cells, and are recruited to gene loci by the OGT enzyme [35], which also O-GlcNAcylates itself [30]. The activity of OGT is regulated by cellular concentrations of UDP-GlcNAc substrate [36,37], which is increased in the diabetic heart [38]. "
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    • "Most probably the detected band at 40 kDa represents a larger post-translationalmodified protein. Many studies have indicated that prohibitin undergoes multiple post-translational modifications, such as phosphorylation, glycosylation, palmitoylation, ubiquitination and others505152. Such modifications could explain the shift in molecular weight of the two spots and admits to speculate about the consequences. "
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