title: Membrane localization of Src homology 2-containing inositol 5'-phosphatase 2 via Shc association is required for the negative regulation of insulin signaling in Rat1 fibroblasts overexpressing insulin receptors.
abstract: Lipid phosphatase SHIP2 [Src homology 2 (SH2)-containing inositol 5'-phosphatase 2] has been shown to be a physiologically critical negative regulator of insulin signaling. We investigated the molecular mechanism by which SHIP2 negatively regulates insulin-induced phosphorylation of Akt, a key downstream molecule of phosphatidylinositol 3-kinase important for the biological action of insulin. Overexpression of wild-type SHIP2 (WT-SHIP2) inhibited insulin-induced phosphorylation of Akt at both Thr(308) and Ser(473) in Rat1 fibroblasts expressing insulin receptors. The degree of inhibition was less in the cells expressing either a mutant SHIP2 with R47Q change (R/Q-SHIP2) in the SH2 domain, or a mutant SHIP2 with Y987F change (Y/F-SHIP2) in the C-terminal tyrosine phosphorylation site. However, on addition of a myristoylation signal, WT-SHIP2, R/Q-SHIP2, and Y/F-SHIP2 all efficiently inhibited insulin-induced Akt phosphorylation at both residues, whereas a 5'-phosphatase-defective mutant SHIP2 (deltaIP-SHIP2) with the myristoylation signal did not. Interestingly, the degree of inhibition of Akt phosphorylation by R/Q-SHIP2 and Y/F-SHIP2 is well correlated with the extent of their association with Shc. In addition, overexpression of WT-Shc increased the insulin-induced association of SHIP2 with Shc, whereas a decrease in the amount of Shc on expression of antisense Shc mRNA led to a reduction in the SHIP2-Shc association. Furthermore, the inhibitory effect on insulin-induced Akt phosphorylation by WT-SHIP2 was decreased in antisense-Shc cells. These results indicate that the membrane localization of SHIP2 with its 5'-phosphatase activity is required for negative regulation of insulin-induced Akt phosphorylation and that the localization is regulated, at least in part, by the association of SHIP2 with Shc in Rat1 fibroblasts.
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D016375:Antisense Elements (Genetics); D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D025461:Feedback, Physiological; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D008969:Molecular Sequence Data; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017354:Point Mutation; D017346:Protein Serine-Threonine Kinases; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D016375:Antisense Elements (Genetics); D007328:Insulin; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; C528035:Shc1 protein, rat; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014443:Tyrosine; D012694:Serine; D011972:Receptor, Insulin; C494918:AKT1 protein, human; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D010744:Phosphoric Monoester Hydrolases; C098706:INPPL1 protein, human; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases