Overexpression of the Shb SH2 domain-protein in insulin-producing cells leads to altered signaling through the IRS-1 and IRS-2 proteins

• BackgroundOverexpression of the Src homology 2 domain protein Shb in _-cells of transgenic mice has been shown to promote an increased _-cell mass. To investigate the mechanisms by which Shb controls the _-cell mass, we have presently studied the effects of Shb overexpression on the IRS-1–induced signaling pathway in mouse islet _-cells and in insulin-producing RINm5F cells and correlated these effects to growth and death patterns.Materials and MethodsShb overexpression was achieved in RINm5F cells by selection of stable clones or by FACS purification of transiently transfected cells. For Shb overexpression in primary mouse islet cells, a Shb-transgene mouse was used. Cell proliferation and death rates were determined using flow cytometry. Serum-, insulin-, and IGF-1-stimulated signaling events were studied by immunoblot, immunoprecipitation, and in vitro kinase procedures.ResultsTransient Shb overexpression in RINm5F cells resulted in increased proliferation. Both Shb-overexpressing RINm5F cells and islet cells from transgenic mice (islet Shb) exhibited increased basal tyrosine phosphorylation of IRS-1. Shb overexpression resulted also in the assembly and activation of a multiunit complex consisting of at least Shb, IRS-1, IRS-2, FAK, and PI3K. Consequently, the phosphorylation of Akt was enhanced under basal conditions in Shb overexpressing cells. Finally, Shb overexpression did not affect insulin-induced phosphorylation of the PI3K-antagonist PTEN.ConclusionIt is concluded that the Shb-induced alterations in the IRS-1/PI3K/Akt pathway may be relevant to the understanding of growth and death patterns of insulin-producing cells.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine (hsv//eng)

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Cellforskning

Cell Research

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