Research Papers: Gerotarget (Focus on Aging):
IGF-1 mediated phosphorylation of specific IRS-1 serines in Ames dwarf fibroblasts is associated with longevity
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John Papaconstantinou1 and Ching-Chyuan Hsieh1
1 The Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, USA
John Papaconstantinou, email:
Keywords: IGF-1, dermal fibroblasts, Ames dwarf mouse, IRS-1 serine phosphorylation, longevity, Gerotarget
Received: September 10, 2015 Accepted: September 22, 2015 Published: October 14, 2015
Insulin/IGF-1 signaling involves phosphorylation/dephosphorylation of serine/threonine or tyrosine residues of the insulin receptor substrate (IRS) proteins and is associated with hormonal control of longevity determination of certain long-lived mice. The stimulation of serine phosphorylations by IGF-1 suggests there is insulin/IGF-1 crosstalk that involves the phosphorylation of the same serine residues. By this mechanism, insulin and IGF-1 mediated phosphorylation of specific IRS-1 serines could play a role in longevity determination.
We used fibroblasts from WT and Ames dwarf mice to examine whether: (a) IGF-1 stimulates phosphorylation of IRS-1 serines targeted by insulin; (b) the levels of serine phosphorylation differ in WT vs. Ames fibroblasts; and (c) aging affects the levels of these serine phosphorylations which are altered in the Ames dwarf mutant. We have shown that IRS-1 is a substrate for IGF-1 induced phosphorylation of Ser307, Ser612, Ser636/639, and Ser1101; that the levels of phosphorylation of these serines are significantly lower in Ames vs. WT cells; that IGF-1 mediated phosphorylation of these serines increases with age in WT cells. We propose that insulin/IGF-1 cross talk and level of phosphorylation of specific IRS-1 serines may promote the Ames dwarf longevity phenotype.
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