This Article Full Text Full Text (PDF) All Versions of this Article: 16/10/2371    most recent Author Manuscript (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ishihara, H. Articles by Kobayashi, M. Search for Related Content PubMed PubMed Citation Articles by Ishihara, H. Articles by Kobayashi, M. Pubmed/NCBI databases Protein Compound via MeSH Substance via MeSH Hazardous Substances DB L-SERINE L-TYROSINE

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

First Department of Internal Medicine (H.I., M.I., T.W., H.H.,M.K.) and the Department of Clinical Pharmacology (T.S., S.K.), Toyama Medical & Pharmaceutical University, Toyama 930-0194, Japan; and the Sainou Hospital (H.I.), Toyama 930-0887, Japan

Address all correspondence and requests for reprints to: Toshiyasu Sasaoka, M.D., Ph.D., Department of Clinical Pharmacology, Toyama Medical& Pharmaceutical University, 2630 Sugitani, Toyama 930-0194, Japan. E-mail: tsasaoka-tym{at}umin.ac.jp.

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 Thr³⁰⁸ and Ser⁴⁷³ 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 (IP-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.

This article has been cited by other articles:

				W.-H. Leung and S. Bolland The Inositol 5'-Phosphatase SHIP-2 Negatively Regulates IgE-Induced Mast Cell Degranulation and Cytokine Production J. Immunol., July 1, 2007; 179(1): 95 - 102. [Abstract] [Full Text] [PDF]

				B. Ananthanarayanan, Q. Ni, and J. Zhang Signal propagation from membrane messengers to nuclear effectors revealed by reporters of phosphoinositide dynamics and Akt activity PNAS, October 18, 2005; 102(42): 15081 - 15086. [Abstract] [Full Text] [PDF]

				S. Kagawa, T. Sasaoka, S. Yaguchi, H. Ishihara, H. Tsuneki, S. Murakami, K. Fukui, T. Wada, S. Kobayashi, I. Kimura, et al. Impact of Src Homology 2-Containing Inositol 5'-Phosphatase 2 Gene Polymorphisms Detected in a Japanese Population on Insulin Signaling J. Clin. Endocrinol. Metab., May 1, 2005; 90(5): 2911 - 2919. [Abstract] [Full Text] [PDF]

				S. Murakami, T. Sasaoka, T. Wada, K. Fukui, K. Nagira, H. Ishihara, I. Usui, and M. Kobayashi Impact of Src Homology 2-Containing Inositol 5'-Phosphatase 2 on the Regulation of Insulin Signaling Leading to Protein Synthesis in 3T3-L1 Adipocytes Cultured with Excess Amino Acids Endocrinology, July 1, 2004; 145(7): 3215 - 3223. [Abstract] [Full Text] [PDF]

				T. Sasaoka, T. Wada, K. Fukui, S. Murakami, H. Ishihara, R. Suzuki, K. Tobe, T. Kadowaki, and M. Kobayashi SH2-containing Inositol Phosphatase 2 Predominantly Regulates Akt2, and Not Akt1, Phosphorylation at the Plasma Membrane in Response to Insulin in 3T3-L1 Adipocytes J. Biol. Chem., April 9, 2004; 279(15): 14835 - 14843. [Abstract] [Full Text] [PDF]