Article

Diabetologia

, Volume 56, Issue 6, pp 1327-1338

Imatinib mesilate-induced phosphatidylinositol 3-kinase signalling and improved survival in insulin-producing cells: role of Src homology 2-containing inositol 5′-phosphatase interaction with c-Abl

  • D. MokhtariAffiliated withScience for Life Laboratory, Department of Medical Cell Biology, Uppsala University
  • , A. Al-AminAffiliated withScience for Life Laboratory, Department of Medical Cell Biology, Uppsala University
  • , K. TurpaevAffiliated withVavilov Institute of General Genetics, Russian Academy of SciencesCenter for Theoretical Problems of Physicochemical Pharmacology, Russian Academy of Sciences
  • , T. LiAffiliated withScience for Life Laboratory, Department of Medical Cell Biology, Uppsala University
  • , O. Idevall-HagrenAffiliated withDepartment of Medical Cell Biology, Uppsala University, Biomedicum
  • , J. LiAffiliated withDepartment of Medical Cell Biology, Uppsala University, Biomedicum
  • , A. WuttkeAffiliated withDepartment of Medical Cell Biology, Uppsala University, Biomedicum
  • , R. G. FredAffiliated withScience for Life Laboratory, Department of Medical Cell Biology, Uppsala University
  • , P. RavassardAffiliated withInstitut du Cerveau et de la Moelle, CRICM CNRS UMR7225, Inserm, Université Pierre et Marie Curie, Hôpital Pitié-Salpêtrière
    • , R. ScharfmannAffiliated withInserm U845, Research Centre for Growth and Signalling, Faculty-Institute Cochin
    • , A. TengholmAffiliated withDepartment of Medical Cell Biology, Uppsala University, Biomedicum
    • , N. WelshAffiliated withScience for Life Laboratory, Department of Medical Cell Biology, Uppsala University Email author 

Abstract

Aims/hypothesis

It is not clear how small tyrosine kinase inhibitors, such as imatinib mesilate, protect against diabetes and beta cell death. The aim of this study was to determine whether imatinib, as compared with the non-cAbl-inhibitor sunitinib, affects pro-survival signalling events in the phosphatidylinositol 3-kinase (PI3K) pathway.

Methods

Human EndoC-βH1 cells, murine beta TC-6 cells and human pancreatic islets were used for immunoblot analysis of insulin receptor substrate (IRS)-1, Akt and extracellular signal-regulated kinase (ERK) phosphorylation. Phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] plasma membrane concentrations were assessed in EndoC-βH1 and MIN6 cells using evanescent wave microscopy. Src homology 2-containing inositol 5′-phosphatase 2 (SHIP2) tyrosine phosphorylation and phosphatase and tensin homologue deleted on chromosome 10 (PTEN) serine phosphorylation, as well as c-Abl co-localisation with SHIP2, were studied in HEK293 and EndoC-βH1 cells by immunoprecipitation and immunoblot analysis. Gene expression was assessed using RT-PCR. Cell viability was measured using vital staining.

Results

Imatinib stimulated ERK(thr202/tyr204) phosphorylation in a c-Abl-dependent manner. Imatinib, but not sunitinib, also stimulated IRS-1(tyr612), Akt(ser473) and Akt(thr308) phosphorylation. This effect was paralleled by oscillatory bursts in plasma membrane PI(3,4,5)P3 levels. Wortmannin induced a decrease in PI(3,4,5)P3 levels, which was slower in imatinib-treated cells than in control cells, indicating an effect on PI(3,4,5)P3-degrading enzymes. In line with this, imatinib decreased the phosphorylation of SHIP2 but not of PTEN. c-Abl co-immunoprecipitated with SHIP2 and its binding to SHIP2 was largely reduced by imatinib but not by sunitinib. Imatinib increased total β-catenin levels and cell viability, whereas sunitinib exerted negative effects on cell viability.

Conclusions/interpretation

Imatinib inhibition of c-Abl in beta cells decreases SHIP2 activity, which results in enhanced signalling downstream of PI3 kinase.

Keywords

c-Abl Cell death EndoC-βH1 cells Imatinib mesilate Insulin-producing cells PIP3 signalling SHIP2