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

Sudharsana R Ande,Suresh Mishra,Saby Moulik,Bostjan Kobe

doi:10.1371/journal.pone.0004586

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 β-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.

Highlights

Prohibitin (PHB, known as PHB1) and its homologue PHB2 are evolutionarily conserved proteins and have been shown to be involved in cell cycle progression, cell differentiation, gene transcription and mitochondrial functions [1]
PHB interacts with O-GlacNAc transferase (OGT) and is an O-GlcNAc modified Because PHB and OGT both interact with insulin receptor and undergo tyrosine phosphorylation [15,21], we examined whether PHB could interact with OGT
We provide evidence that PHB interacts with OGT in response to insulin and undergoes O-GlcNAc modification (Fig. 1)

Summary

Introduction

Prohibitin (PHB, known as PHB1) and its homologue PHB2 are evolutionarily conserved proteins and have been shown to be involved in cell cycle progression, cell differentiation, gene transcription and mitochondrial functions [1]. Lipid rafts has been known to serve as platforms for receptor tyrosine kinase signaling including insulin and B cell receptor signaling [6]. This involves tyrosine phosphorylation of various signaling intermediates and tyrosine phosphorylation dependent protein-protein interactions [7,8]. Central and C-terminus part of PHB contain tyrosine residues (Tyr114 and Tyr259) which exist within a motif similar to tyrosine known to be phosphorylated in the epidermal growth factor and insulin receptors [10], in beta integrins [11] and in B cell receptors [12]. Tyr114 and Tyr259 residues in PHB are highly conserved across species suggesting a functional role for these residues [1]

Methods

Results

Conclusion