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Mol Med. 2002 Nov;8(11):695-704.

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

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1
Department of Medical Cell Biology, Uppsala University, Sweden. Nils.Welsh@medcellbiol.uu.se

Abstract

BACKGROUND:

Overexpression of the Src homology 2 domain protein Shb in beta-cells of transgenic mice has been shown to promote an increased beta-cell mass. To investigate the mechanisms by which Shb controls the beta-cell mass, we have presently studied the effects of Shb overexpression on the IRS-1-induced signaling pathway in mouse islet beta-cells and in insulin-producing RINm5F cells and correlated these effects to growth and death patterns.

MATERIALS AND METHODS:

Shb 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.

RESULTS:

Transient 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.

CONCLUSION:

It 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.

PMID:
12520086
PMCID:
PMC2039954
[Indexed for MEDLINE]
Free PMC Article

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