Journal Article

Increasing GLP-1–Induced β-Cell Proliferation by Silencing the Negative Regulators of Signaling cAMP Response Element Modulator-α and DUSP14

Sonia Klinger, Wanda Dolci, Philippe A. Halban, Marie-Bernard Debril, Carine Poussin, Bernard Thorens

2008

Overview

Increasing GLP-1–Induced β-Cell Proliferation by Silencing the Negative Regulators of Signaling cAMP Response Element Modulator-α and DUSP14 Sonia Klinger 1 , 2 , Carine Poussin 1 , 2 , Marie-Bernard Debril 1 , 2 , Wanda Dolci 1 , 2 , Philippe A. Halban 3 and Bernard Thorens 1 , 2 1 Institute of Physiology, University of Lausanne, Lausanne, Switzerland 2 Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland 3 Department of Genetic Medicine and Development, University Medical Center, University Hospital, Geneva, Switzerland Address correspondence and reprint requests to Bernard Thorens, University of Lausanne, Center for Integrative Genomics, Génopode Building, 1015 Lausanne, Switzerland. E-mail: bernard.thorens{at}unil.ch Abstract OBJECTIVE —Glucagon-like peptide-1 (GLP-1) is a growth and differentiation factor for mature β-cells and their precursors. However, the overall effect of GLP-1 on increasing β-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 β-cell proliferation. RESEARCH DESIGN AND METHODS —We examined GLP-1–regulated genes in βTC-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 β-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)-α 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 CREMα or DUSP14 or expression of a dominant-negative form of DUSP14 increased β-cell line proliferation and enhanced the GLP-1–induced proliferation of primary β-cells. CONCLUSIONS —Together, our data show that 1 ) the cAMP/protein kinase A/CREB and MAPK/ERK1/2 pathways can additively control β-cell proliferation, 2 ) β-cells have evolved several mechanisms limiting GLP-1–induced cellular proliferation, and 3 ) blocking these mechanisms increases the positive effect of GLP-1 on β-cell mass. CREB, cAMP response element-binding protein CREM, cAMP response element modulator DMEM, Dulbecco's modified Eagle's medium ERK1/2, extracellular signal-regulated kinase 1/2 FACS, fluorescence-activated cell sorter FBS, fetal bovine serum GAPDH, glyceraldehyde-3-phosphate dehydrogenase GFP, green fluorescent protein GLP-1, glucagon-like peptide-1 MAPK, mitogen-activated protein kinase PI 3-kinase, phosphatidylinositol 3-kinase PKA, protein kinase A Footnotes Published ahead of print at http://diabetes.diabetesjournals.org on 19 November 2007. DOI: 10.2337/db07-1414. Additional information for this article can be found in an online appendix at http://dx.doi.org/10.2337/db07-1414 . The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Received October 4, 2007. Accepted November 13, 2007. DIABETES

• Publisher: American Diabetes Association
• Subject: Animals / Care and treatment / Cell Line / Cell proliferation / Cell Proliferation - drug effects / Cells, Cultured / Cyclic AMP Response Element Modulator - genetics / Cyclic AMP Response Element Modulator - metabolism / Diabetes / Diabetes mellitus / Dose-Response Relationship, Drug / Dual-Specificity Phosphatases - genetics / Dual-Specificity Phosphatases - metabolism / Gene Expression Profiling / Gene Silencing / Genetic aspects / Genetic regulation / Glucagon-Like Peptide 1 - pharmacology / Glucose - metabolism / Glucose - pharmacology / Humans / Insulin-Secreting Cells - cytology / Insulin-Secreting Cells - drug effects / Male / Mice / Oligonucleotide Array Sequence Analysis / Peptides - pharmacology / RGS Proteins - genetics / RGS Proteins - metabolism / Venoms - pharmacology