title: Increasing GLP-1-induced beta-cell proliferation by silencing the negative regulators of signaling cAMP response element modulator-alpha and DUSP14.
abstract: OBJECTIVE
  Glucagon-like peptide-1 (GLP-1) is a growth and differentiation factor for mature beta-cells and their precursors. However, the overall effect of GLP-1 on increasing beta-cell mass in both in vivo and in vitro conditions is relatively small, and augmenting this effect would be beneficial for the treatment or prevention of type 1 and type 2 diabetes. Here, we searched for cellular mechanisms that may limit the proliferative effect of GLP-1 and tested whether blocking them could increase beta-cell proliferation.
  
  
  METHODS
  We examined GLP-1-regulated genes in beta TC-Tet cells by cDNA microarrays. To assess the effect of some of these gene on cell proliferation, we reduced their expression using small heterogenous RNA in beta-cell lines and primary mouse islets and measured [(3)H]thymidine or 5'-bromo-2'-deoxyuridine incorporation.
  
  
  RESULTS
  We identified four negative regulators of intracellular signaling that were rapidly and strongly activated by GLP-1: the regulator of G-protein-signaling RGS2; the cAMP response element-binding protein (CREB) antagonists cAMP response element modulator (CREM)-alpha and ICERI; and the dual specificity phosphatase DUSP14, a negative regulator of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase 1/2 (ERK1/2) pathway. We show that knockdown of CREMalpha or DUSP14 or expression of a dominant-negative form of DUSP14 increased beta-cell line proliferation and enhanced the GLP-1-induced proliferation of primary beta-cells.
  
  
  CONCLUSIONS
  Together, our data show that 1) the cAMP/protein kinase A/CREB and MAPK/ERK1/2 pathways can additively control beta-cell proliferation, 2) beta-cells have evolved several mechanisms limiting GLP-1-induced cellular proliferation, and 3) blocking these mechanisms increases the positive effect of GLP-1 on beta-cell mass.
authors.affiliation: Institute of Physiology, University of Lausanne, Lausanne, Switzerland.
authors.forename: Sonia
authors.initials: S
authors.lastname: Klinger
authors.forename: Carine
authors.initials: C
authors.lastname: Poussin
authors.forename: Marie-Bernard
authors.initials: MB
authors.lastname: Debril
authors.forename: Wanda
authors.initials: W
authors.lastname: Dolci
authors.forename: Philippe A
authors.initials: PA
authors.lastname: Halban
authors.forename: Bernard
authors.initials: B
authors.lastname: Thorens
mesh_terms: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D051786:Cyclic AMP Response Element Modulator / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D054637:Dual-Specificity Phosphatases / Q000235:genetics / Q000378:metabolism*; D000077270:Exenatide; D020869:Gene Expression Profiling; D020868:Gene Silencing; D052216:Glucagon-Like Peptide 1 / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D050417:Insulin-Secreting Cells / Q000166:cytology* / Q000187:drug effects*; D008297:Male; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D010455:Peptides / Q000494:pharmacology; D020710:RGS Proteins / Q000235:genetics / Q000378:metabolism; D014688:Venoms / Q000494:pharmacology
chemical_list: D010455:Peptides; D020710:RGS Proteins; C105345:Rgs2 protein, mouse; D014688:Venoms; D051786:Cyclic AMP Response Element Modulator; D052216:Glucagon-Like Peptide 1; D000077270:Exenatide; D054637:Dual-Specificity Phosphatases; C498844:Dusp14 protein, mouse; D005947:Glucose