title: Pancreatic and duodenal homeobox 1 (PDX1) phosphorylation at serine-269 is HIPK2-dependent and affects PDX1 subnuclear localization.
abstract: Pancreatic and duodenal homeobox 1 (PDX1) regulates pancreatic development and mature beta-cell function. We demonstrate by mass spectrometry that serine residue at position 269 in the C-terminal domain of PDX1 is phosphorylated in beta-cells. Besides we show that the degree of phosphorylation, assessed with a phospho-Ser-269-specific antibody, is decreased by elevated glucose concentrations in both MIN6 beta-cells and primary mouse pancreatic islets. Homeodomain interacting protein kinase 2 (HIPK2) phosphorylates PDX1 in vitro; phosphate incorporation substantially decreases in PDX1 S269A mutant. 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. Instead, PDX1 S269E mutant displayed abnormal changes in subnuclear localization in response to high glucose. 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.
authors.affiliation: Section of Cell Biology, Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, Imperial College London, London SW7 2AZ, UK.
authors.forename: Rong
authors.initials: R
authors.lastname: An
authors.forename: Gabriela
authors.initials: G
authors.lastname: da Silva Xavier
authors.forename: Francesca
authors.initials: F
authors.lastname: Semplici
authors.forename: Saharnaz
authors.initials: S
authors.lastname: Vakhshouri
authors.forename: Huai-Xiang
authors.initials: HX
authors.lastname: Hao
authors.forename: Jared
authors.initials: J
authors.lastname: Rutter
authors.forename: Mario A
authors.initials: MA
authors.lastname: Pagano
authors.forename: Flavio
authors.initials: F
authors.lastname: Meggio
authors.forename: Lorenzo A
authors.initials: LA
authors.lastname: Pinna
authors.forename: Guy A
authors.initials: GA
authors.lastname: Rutter
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D055550:Protein Stability; D012694:Serine / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D018398:Homeodomain Proteins; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein; D012694:Serine; C492003:Hipk2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D005947:Glucose