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.
Original language | English |
---|---|
Pages (from-to) | 155-61 |
Number of pages | 7 |
Journal | Biochemical and Biophysical Research Communications |
Volume | 399 |
Issue number | 2 |
DOIs | |
Publication status | Published - 20 Aug 2010 |
Keywords
- Animals
- Carrier Proteins/metabolism
- Cell Differentiation
- Cell Line
- Cell Nucleus/metabolism
- Glucose/metabolism
- Homeodomain Proteins/genetics
- Humans
- Insulin-Secreting Cells/cytology
- Mice
- Phosphorylation
- Protein Stability
- Protein-Serine-Threonine Kinases/metabolism
- Serine/genetics
- Trans-Activators/genetics