β-Catenin is O-GlcNAc glycosylated at Serine 23: Implications for β-catenin's subcellular localization and transactivator function

•β-Catenin is O-GlcNAc modified at Serine 23 at the N-Terminal domain of β-catenin.•O-GlcNAcylation at Serine 23 is an important regulatory post-translational modification of β-catenin.•O-GlcNAcylation at Serine 23 regulates the subcellular localization of β-catenin.•O-GlcNAcylation at Serine 23 regulates the transcritional activity of β-catenin.•O-GlcNAcylation at Serine 23 may be significant in β-catenin's role as an oncoprotein.

BackgroundWe have previously reported that β-catenin is post-translationally modified with a single O-linked attachment of β-N-acetyl-glucosamine (O-GlcNAc). We showed that O-GlcNAc regulated β-catenin's subcellular localization and transcriptional activity.ObjectiveThe objectives of this investigation were to identify the putative O-GlcNAc sites of β-catenin and the relevance of identified sites in the regulation of β-catenin's localization and transcriptional activity.MethodMissense mutations were introduced to potential O-GlcNAc sites of pEGFP-C2-N-Terminal- or pEGFP-C2-Wild Type-β-catenin by site-directed mutagenesis. We determined the levels of O-GlcNAc-β-catenin, subcellular localization, interaction with binding partners and transcriptional activity of the various constructs.ResultsSerine 23 of β-catenin was determined as a site for O-GlcNAc modification which regulated its subcellular distribution, its interactions with cellular partners and consequently its transcriptional activity.SignificanceO-GlcNAcylation of Serine 23 is a novel regulatory modification for β-catenin's subcellular localization and transcriptional activity. This study is the first report to characterize site specific regulation of β-catenin by the O-GlcNAc modification.