title: Inhibition of human insulin gene transcription and MafA transcriptional activity by the dual leucine zipper kinase.
abstract: Insulin biosynthesis is an essential β-cell function and inappropriate insulin secretion and biosynthesis contribute to the pathogenesis of diabetes mellitus type 2. Previous studies showed that the dual leucine zipper kinase (DLK) induces β-cell apoptosis. Since β-cell dysfunction precedes β-cell loss, in the present study the effect of DLK on insulin gene transcription was investigated in the HIT-T15 β-cell line. Downregulation of endogenous DLK increased whereas overexpression of DLK decreased human insulin gene transcription. 5'- and 3'-deletion human insulin promoter analyses resulted in the identification of a DLK responsive element that mapped to the DNA binding-site for the β-cell specific transcription factor MafA. Overexpression of DLK wild-type but not its kinase-dead mutant inhibited MafA transcriptional activity conferred by its transactivation domain. Furthermore, in the non-β-cell line JEG DLK inhibited MafA overexpression-induced human insulin promoter activity. Overexpression of MafA and DLK or its kinase-dead mutant into JEG cells revealed that DLK but not its mutant reduced MafA protein content. Inhibition of the down-stream DLK kinase c-Jun N-terminal kinase (JNK) by SP600125 attenuated DLK-induced MafA loss. Furthermore, mutation of the serine 65 to alanine, shown to confer MafA protein stability, increased MafA-dependent insulin gene transcription and prevented DLK-induced MafA loss in JEG cells. These data suggest that DLK by activating JNK triggers the phosphorylation and degradation of MafA thereby attenuating insulin gene transcription. Given the importance of MafA for β-cell function, the inhibition of DLK might preserve β-cell function and ultimately retard the development of diabetes mellitus type 2.
authors.affiliation: Department of Pharmacology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Marie-Jeannette
authors.initials: MJ
authors.lastname: Stahnke
authors.affiliation: Department of Pharmacology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Corinna
authors.initials: C
authors.lastname: Dickel
authors.affiliation: Institute of Clinical Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Schröder
authors.affiliation: Institute of Clinical Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Diana
authors.initials: D
authors.lastname: Kaiser
authors.affiliation: Department of Pharmacology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Blume
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, USA.
authors.forename: Roland
authors.initials: R
authors.lastname: Stein
authors.affiliation: Institut Curie, CNRS UMR 3347, INSERM U1021, Paris Sud University Centre de Recherche, Orsay, France.
authors.forename: Celio
authors.initials: C
authors.lastname: Pouponnot
authors.affiliation: Department of Pharmacology, University Medical Center Göttingen, Göttingen, Germany; Institute of Clinical Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; DZHK (German Centre for Cardiovascular Research) partner site Hamburg/Kiel/Lübeck, Hamburg, Germany; Institute of Pharmacy, University of Hamburg, Hamburg, Germany. Electronic address: e.oetjen@uke.uni-hamburg.de.
authors.forename: Elke
authors.initials: E
authors.lastname: Oetjen
mesh_terms: D000873:Anthracenes / Q000494:pharmacology; D002460:Cell Line; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D007328:Insulin / Q000235:genetics* / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051473:Maf Transcription Factors, Large / Q000235:genetics* / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011401:Promoter Regions, Genetic; D034622:RNA Interference
chemical_list: D000873:Anthracenes; D007328:Insulin; C485159:MAFA protein, human; D051473:Maf Transcription Factors, Large; C432165:pyrazolanthrone; D048031:JNK Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases
keywords: DLK; Diabetes mellitus; Insulin gene transcription; MafA
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