Abstract
The transcription factor PDX-1 (pancreatic duodenal homeobox-1) is required for normal pancreatic development and for the function of insulin-producing islet beta-cells in mammals. We have shown previously that glucose regulates insulin gene expression in part through the activation and translocation of PDX-1 from the nuclear periphery to the nucleoplasm. We have also found that PASK [PAS (Per-Arnt-Sim) kinase], a member of the nutrient-regulated family of protein kinases, is activated in response to glucose challenge in beta-cells and is involved in the regulation of expression of PDX-1. Purified PASK efficiently phosphorylated recombinant PDX-1 in vitro on a single site (Thr-152). To determine the impact of phosphorylation at this site, we generated wild-type and mutant (T152A, T152D and T152E) forms of PDX-1 and examined the distribution of each of these in clonal MIN6 beta-cells by immunocytochemical analysis. Unexpectedly, only the T152D mutation significantly affected subcellular distribution, increasing the ratio of nuclear/cytosolic labelling at low and high glucose concentrations, suggesting that phosphorylation at Thr-152 inhibits nuclear uptake in response to glucose. Based on these results, experiments to examine the contribution of Thr-152 to the overall phosphorylation of PDX-1 in intact cells will be undertaken.
Original language | English |
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Pages (from-to) | 791-3 |
Number of pages | 3 |
Journal | Biochemical Society Transactions |
Volume | 34 |
Issue number | 5 |
DOIs | |
Publication status | Published - Nov 2006 |
Keywords
- Cell Nucleus/metabolism
- Duodenum/physiology
- Homeodomain Proteins/genetics
- Homeostasis
- Humans
- Insulin-Secreting Cells/physiology
- Mutation
- Pancreas/physiology
- Protein Transport
- Protein-Serine-Threonine Kinases/metabolism
- Trans-Activators/genetics