title: 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.
abstract: OBJECTIVE
  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
  Imatinib inhibition of c-Abl in beta cells decreases SHIP2 activity, which results in enhanced signalling downstream of PI3 kinase.
authors: Science for Life Laboratory, Department of Medical Cell Biology, Uppsala University, Biomedicum, PO Box 571, 751 23 Uppsala, Sweden.
authors: D
authors: D
authors: Mokhtari
authors: A
authors: A
authors: Al-Amin
authors: K
authors: K
authors: Turpaev
authors: T
authors: T
authors: Li
authors: O
authors: O
authors: Idevall-Hagren
authors: J
authors: J
authors: Li
authors: A
authors: A
authors: Wuttke
authors: R G
authors: RG
authors: Fred
authors: P
authors: P
authors: Ravassard
authors: R
authors: R
authors: Scharfmann
authors: A
authors: A
authors: Tengholm
authors: N
authors: N
authors: Welsh
mesh_terms: D001549:Benzamides / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured; D049452:Green Fluorescent Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D000068877:Imatinib Mesylate; D007211:Indoles / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology*; D011485:Protein Binding; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D016315:Proto-Oncogene Proteins c-abl / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology*; D011758:Pyrroles / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D000077210:Sunitinib; D013997:Time Factors
chemical_list: D001549:Benzamides; D007211:Indoles; D007328:Insulin; D018129:Phosphatidylinositol Phosphates; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D011758:Pyrroles; C060974:phosphatidylinositol 3,4,5-triphosphate; D049452:Green Fluorescent Proteins; D000068877:Imatinib Mesylate; D019869:Phosphatidylinositol 3-Kinases; D016315:Proto-Oncogene Proteins c-abl; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C098706:INPPL1 protein, human; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D000077210:Sunitinib