Pancreatic and duodenal homeobox 1 (PDX1) phosphorylation at serine-269 is HIPK2-dependent and affects PDX1 subnuclear localization.
Bottom Line: Silencing of HIPK2 led to a 51+/-0.2% decrease in Ser-269 phosphorylation in MIN6 beta-cells.Mutation of Ser-269 to phosphomimetic residue glutamic acid (S269E) or de-phosphomimetic residue alanine (S269A) exerted no effect on PDX1 half-life.Our results suggest that HIPK2-mediated phosphorylation of PDX1 at Ser-269 might be a regulatory mechanism connecting signals generated by changes in extracellular glucose concentration to downstream effectors via changes in subnuclear localization of PDX1, thereby influencing islet cell differentiation and function.
Affiliation: Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London SW7 2AZ, UK.Show MeSH
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Mentions: PDX1 Ser-269 was identified as a potential phosphorylation site by mass spectrometry (Supplementary Fig. 1). We, therefore, explored the possibility that phosphorylation of PDX1 at Ser-269 may be regulated by glucose in living β-cells and, thus, may, at least potentially, contribute to the regulation of PDX1 function by the sugar. After treatment at low glucose concentrations (3 mM) for 16 (MIN6 β-cells) or 1 h (islets), we further incubated islets (Fig. 1A) or MIN6 β-cells (Fig. 1B) in medium containing 16.7 or 30 mM glucose, respectively, for varying times.
Affiliation: Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London SW7 2AZ, UK.