In:
American Journal of Physiology-Endocrinology and Metabolism, American Physiological Society, Vol. 300, No. 5 ( 2011-05), p. E824-E836
Kurzfassung:
The identity of specific serine phosphorylation residues of insulin receptor substrate (IRS)-2 and their impact on insulin signal transduction are largely unknown. Ser 675 and Ser 907 of mouse IRS-2 are adjacent to PI 3-kinase or Grb2 binding domains, respectively. Using monoclonal phosphosite-specific antibodies, we demonstrated the phosphorylation of both serines after stimulation of Fao hepatoma cells with insulin, anisomycin, or phorbol esters. Phosphorylation of both sites was a late and prolonged event during insulin treatment and was also detected in liver tissue of insulin-treated as well as refed mice. Inhibition and siRNA-mediated knockdown of ERK1/2 indicated that the insulin-induced phosphorylation of Ser 907 was ERK dependent. Phosphorylation of Ser 907 did not prevent the insulin-induced association of IRS-2 with Grb2, but phosphorylation of the adjacent Tyr 911 was proved to be crucial in HEK 293 cells expressing IRS-2 Ala mutants. The insulin-induced phosphorylation of Ser 675 was prevented by inhibition and siRNA-mediated knockdown of mTOR but not of p70 S6K1 . Mutation of Ser 675 to Ala did not affect downstream insulin signaling but increased the half-life of the protein, suggesting an involvement of phospho-Ser 675 in an accelerated degradation of IRS-2. Moreover, the insulin-induced degradation of IRS-2 was blocked by inhibition of mTOR. We conclude that the two novel insulin-dependent serine phosphorylation sites of IRS-2 were not involved in the regulation of the adjacent PI 3-kinase and Grb2 binding domains but might be implicated in the ERK- and mTOR-mediated negative feedback control.
Materialart:
Online-Ressource
ISSN:
0193-1849
,
1522-1555
DOI:
10.1152/ajpendo.00409.2010
Sprache:
Englisch
Verlag:
American Physiological Society
Publikationsdatum:
2011
ZDB Id:
1477331-4
SSG:
12
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