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Insulin signaling through Akt/protein kinase B analyzed by small interfering RNA-mediated gene silencing.

ABSTRACT: Glucose homeostasis is controlled by insulin in part through the translocation of intracellular glucose transporter 4 to the plasma membrane in muscle and fat cells. Akt/protein kinase B downstream of phosphatidylinositol 3-kinase has been implicated in this insulin-signaling pathway, but results with a variety of reagents including Akt1-/- and Akt2-/- mice have been equivocal. Here we report the application of small interfering RNA-directed gene silencing to deplete both Akt1 and Akt2 in cultured 3T3-L1 adipocytes. Loss of Akt1 alone slightly impaired insulin-mediated hexose transport activity but had no detectable effect on glycogen synthase kinase (GSK)-3 phosphorylation. In contrast, depletion of Akt2 alone by 70% inhibited approximately half of the insulin responsiveness. Combined depletions of Akt1 plus Akt2 in these cells even more markedly attenuated insulin action on glucose transporter 4 movements, hexose transport activity, and GSK-3 phosphorylation. These data demonstrate a primary role of Akt2 in insulin signaling, significant functional redundancy of Akt1 and Akt2 isoforms in this pathway, and an absolute requirement of Akt protein kinases for regulation of glucose transport and GSK-3 in cultured adipocytes.

SUBMITTER: Jiang ZY

PROVIDER: S-EPMC164627 | biostudies-literature | 2003 Jun

REPOSITORIES: biostudies-literature

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Insulin signaling through Akt/protein kinase B analyzed by small interfering RNA-mediated gene silencing.

Jiang Zhen Y ZY Zhou Qiong L QL Coleman Kerri A KA Chouinard My M Boese Queta Q Czech Michael P MP

Proceedings of the National Academy of Sciences of the United States of America 20030613 13

Glucose homeostasis is controlled by insulin in part through the translocation of intracellular glucose transporter 4 to the plasma membrane in muscle and fat cells. Akt/protein kinase B downstream of phosphatidylinositol 3-kinase has been implicated in this insulin-signaling pathway, but results with a variety of reagents including Akt1-/- and Akt2-/- mice have been equivocal. Here we report the application of small interfering RNA-directed gene silencing to deplete both Akt1 and Akt2 in cultur ...[more]

PMID: 12808134

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Project description:The genesis and progression of cervical cancer involve the mutation or deviant expression of numerous genes, including the activation of oncogenes (Ha-ras, C-myc, C-erbB2 and Bcl-2) and inactivation of tumor-suppressor genes (p53 and Rb). Previous studies showed that small-interfering RNAs (siRNAs) targeting the MAPK p42 gene partly inhibit proliferation and increase apoptosis in human cervical carcinoma HeLa cells. Results of a microarray analysis showed that MAPK p42 siRNA inhibited cell growth through the regulation of cell cycle control and apoptosis and induced interferon-like response in HeLa cells. In order to confirm the dual effects of MAPK p42 siRNA, we compared the roles of siRNA and U0126, an inhibitor of MAPK p42, in HeLa cells. Short 21-mer double-stranded/siRNAs were synthesized to target MAPK p42 mRNA in HeLa cells. The siRNAs were transfected into HeLa cells using Lipofectamine. The cells were treated with siRNA or U0126 at different concentrations for a period of 48 h. The biological effect of siRNA and U0126 on HeLa cells was measured by MTT and flow cytometry. MAPK1, NUP188, P38, STAT1, STAT2, PML and OAS1 were analyzed by real-time quantitative PCR. HeLa cell growth was inhibited by siRNA or U0126, and the effect of siRNA inhibition was greater than that of U0126. Cell cycle phases were different for siRNA or U0126, but HeLa cell growth was arrested at the S phase by siRNA and at G1 phase by U0126. A down-regulation in MAPK p42 expression by siRNA and up-regulation by U0126 were noted. The results of real-time quantitative PCR showed that P38 was up-regulated and NUP188 was down-regulated by siRNA in comparison with the control groups, and the results were consistent with those of U0126. Expression levels of STAT1, STAT2, PML and OAS1 induced by siRNA differed from those induced by U0126. siRNA-mediated silencing and deactivation induced by U0126 in MAPK p42 led to growth inhibition in the HeLa cells. The effects of siRNA on HeLa cell growth were different from those of U0126. Dual effects of MAPK p42 siRNA-2 on HeLa cell growth were noted: one consisted of a specific effect induced by siRNA-mediated p42 MAPK silencing and the other exhibited a non-specific interferon-like response.

Dataset Information

Insulin signaling through Akt/protein kinase B analyzed by small interfering RNA-mediated gene silencing.

Publications

Insulin signaling through Akt/protein kinase B analyzed by small interfering RNA-mediated gene silencing.

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