title: Effects of the Pit1 mutation on the insulin signaling pathway: implications on the longevity of the long-lived Snell dwarf mouse.
abstract: Mutations in Caenorhabditis elegans and mice have identified candidate genes that increase their lifespan via hormonal signal transduction, i.e. the insulin/IGF-1-like pathway. In this study we propose that longevity of the Snell dwarf (Pit1(dw)/Pit1(dw)) mouse is associated with a decrease of the insulin/IGF-1 signaling pathway caused by the Pit1 mutation. We recently demonstrated that the growth hormone deficiency of the dwarf mouse alters circulating insulin levels, thereby resulting in a decreased activity of the insulin/IGF-1 signaling pathway, which is a determining factor in the increased nematode lifespan. The decreased activity of the insulin/IGF-1 signaling pathway is indicated by decrease of (a) IRS-two pool levels; (b) docking of p85 alpha to IRS-2; (c) docking of p 85 alpha to p110 alpha or p110 beta, and (d) IRS-2-associated PI3K activity. In this study we present data suggesting that the InR beta-IRS-1-PI3K pathway is attenuated in the Snell dwarf mouse liver. Our data show that the PI3K activity associated with IRS-1, the docking of IRS-1 to InR beta and the docking of p85 alpha to IRS-1 are attenuated in the aged Snell dwarf. Our studies suggest that the Pit1 mutation results in a decreased activity of the insulin/IGF-1 pathway; that this plays a key role in the longevity of the Snell dwarf mouse and conforms to the nematode longevity paradigm.
authors.affiliation: Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, 613 Basic Science Building, Rt.0643, Galveston, TX 77550-0643, USA.
authors.forename: Ching-Chyuan
authors.initials: CC
authors.lastname: Hsieh
authors.forename: James H
authors.initials: JH
authors.lastname: DeFord
authors.forename: Kevin
authors.initials: K
authors.lastname: Flurkey
authors.forename: David E
authors.initials: DE
authors.lastname: Harrison
authors.forename: John
authors.initials: J
authors.lastname: Papaconstantinou
mesh_terms: D000375:Aging; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D004393:Dwarfism, Pituitary / Q000235:genetics; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008136:Longevity / Q000235:genetics*; D051379:Mice; D008817:Mice, Mutant Strains; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism; D015398:Signal Transduction; D050817:Transcription Factor Pit-1; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology
chemical_list: D004268:DNA-Binding Proteins; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D011972:Receptor, Insulin; D050817:Transcription Factor Pit-1; D014157:Transcription Factors; C526295:Irs1 protein, mouse; C494185:Pou1f1 protein, mouse