31 Torii, S. Saito, N. Kawano, A. Hou, N. Ueki, K. Kulkarni, R. N. Takeuchi, T. 2009 Diabetes 58 3 682-92 Mar 1939-327X (Electronic) 19073770 Animals Autoantibodies Cell Division Gene Silencing Genetic Vectors Glucose/*pharmacology Insulin/secretion Insulin-Secreting Cells/cytology/drug effects/*physiology/secretion Membrane Proteins/*genetics/immunology Mice Promoter Regions, Genetic RNA Polymerase III/genetics Rabbits Rats Receptor-Like Protein Tyrosine Phosphatases, Class 8/analysis/*genetics/immunology Reverse Transcriptase Polymerase Chain Reaction OBJECTIVE: Phogrin and IA-2, autoantigens in insulin-dependent diabetes, have been shown to be involved in insulin secretion in pancreatic beta-cells; however, implications at a molecular level are confusing from experiment to experiment. We analyzed biological functions of phogrin in beta-cells by an RNA interference technique. RESEARCH DESIGN AND METHODS: Adenovirus-mediated expression of short hairpin RNA specific for phogrin (shPhogrin) was conducted using cultured beta-cell lines and mouse islets. Both glucose-stimulated insulin secretion and cell proliferation rate were determined in the phogrin-knockdown cells. Furthermore, protein expression was profiled in these cells. To see the binding partner of phogrin in beta-cells, coimmunoprecipitation analysis was carried out. RESULTS: Adenoviral expression of shPhogrin efficiently decreased its endogenous expression in pancreatic beta-cells. Silencing of phogrin in beta-cells abrogated the glucose-mediated mitogenic effect, which was accompanied by a reduction in the level of insulin receptor substrate 2 (IRS2) protein, without any changes in insulin secretion. Phogrin formed a complex with insulin receptor at the plasma membrane, and their interaction was promoted by high-glucose stimulation that in turn led to stabilization of IRS2 protein. Corroboratively, phogrin knockdown had no additional effect on the proliferation of beta-cell line derived from the insulin receptor-knockout mouse. CONCLUSIONS: Phogrin is involved in beta-cell growth via regulating stability of IRS2 protein by the molecular interaction with insulin receptor. We propose that phogrin and IA-2 function as an essential regulator of autocrine insulin action in pancreatic beta-cells. R01-DK-67536/DK/NIDDK NIH HHS/United StatesJournal ArticleResearch Support, N.I.H., ExtramuralResearch Support, Non-U.S. Gov'tUnited States http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=19073770