title: p38 MAP kinase interacts with and stabilizes pancreatic and duodenal homeobox-1.
abstract: Pancreatic and duodenal homeobox-1 (PDX-1) is a homeodomain-containing transcription factor that plays a critical role in pancreatic development, β-cell differentiation, maintenance of normal β-cell function and tumorigenesis. PDX-1 is subjected to extensive post-translational modifications for its stability, subcellular location and transactivity. We report here that PDX-1 expression is up-regulated by p38 MAP kinase. Antibody array screen identified p38 as a candidate PDX-1-interacting protein in GFP-PDX-1 stable HEK293 cells. The p38-PDX-1 interaction was confirmed by immunoprecipitation/Western blotting analysis in both transient transfection system of HEK293 cells and endogenous system of β-TC-6 cells stimulated by glucagon-like peptide 1 (GLP-1). Co-transfection of p38 with PDX-1 resulted in increased PDX-1 expression in HEK293 cells, which was accompanied by a decreased PDX-1 ubiquitination. Mass spectrometry analysis showed that Ser 268 of human PDX-1 was phosphorylated in GFP-PDX-1 stable HEK293 cells. Functional mutagenesis analysis showed that mutation of Ser 269 of mouse PDX-1 (corresponding to Ser 268 of human PDX-1) into nonphosphorylatable alanine abolished the stabilizing effect of p38 on PDX-1, which was in line with enhanced PDX-1 ubiquitination and shortened half-life of PDX-1. p38 showed kinase activity towards PDX-1 in vitro, suggesting that Ser 269 is a potential p38-regulated phosphorylation site within PDX-1. GLP-1-stimulated PDX-1 expression was accompanied by p38 kinase activation in mouse insulinoma β-TC-6 cells and p38 inhibitor SB202190 inhibited GLP-1-stimulated PDX-1 expression with accompanied inhibition of p38 kinase activation. Taken together, our studies indicated that p38 MAP kinase is a positive regulator of PDX-1 stability and that p38 exerts its stabilizing effect on PDX-1 through a phosphorylation-dependent inhibition of PDX-1 ubiquitination.
authors: Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
authors: G
authors: G
authors: Zhou
authors: H
authors: H
authors: Wang
authors: S-H
authors: SH
authors: Liu
authors: K M
authors: KM
authors: Shahi
authors: X
authors: X
authors: Lin
authors: J
authors: J
authors: Wu
authors: X-H
authors: XH
authors: Feng
authors: J
authors: J
authors: Qin
authors: T-H
authors: TH
authors: Tan
authors: F C
authors: FC
authors: Brunicardi
mesh_terms: D002460:Cell Line; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression; D005786:Gene Expression Regulation; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism; D049452:Green Fluorescent Proteins; D057809:HEK293 Cells; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D010766:Phosphorylation; D055550:Protein Stability; D011725:Pyridines / Q000494:pharmacology; D015534:Trans-Activators / Q000378:metabolism*; D054875:Ubiquitination; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D018398:Homeodomain Proteins; D007093:Imidazoles; D011725:Pyridines; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein; D049452:Green Fluorescent Proteins; D052216:Glucagon-Like Peptide 1; D048051:p38 Mitogen-Activated Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole