title: SIRT1 overexpression antagonizes cellular senescence with activated ERK/S6k1 signaling in human diploid fibroblasts.
abstract: Sir2, a NAD-dependent deacetylase, modulates lifespan in yeasts, worms and flies. The SIRT1, mammalian homologue of Sir2, regulates signaling for favoring survival in stress. But whether SIRT1 has the function to influence cell viability and senescence under non-stressed conditions in human diploid fibroblasts is far from unknown. Our data showed that enforced SIRT1 expression promoted cell proliferation and antagonized cellular senescence with the characteristic features of delayed Senescence-Associated beta-galactosidase (SA-beta-gal) staining, reduced Senescence-Associated Heterochromatic Foci (SAHF) formation and G1 phase arrest, increased cell growth rate and extended cellular lifespan in human fibroblasts, while dominant-negative SIRT1 allele (H363Y) did not significantly affect cell growth and senescence but displayed a bit decreased lifespan. Western blot results showed that SIRT1 reduced the expression of p16(INK4A) and promoted phosphorylation of Rb. Our data also exposed that overexpression of SIRT1 was accompanied by enhanced activation of ERK and S6K1 signaling. These effects were mimicked in both WI38 cells and 2BS cells by concentration-dependent resveratrol, a SIRT1 activator. It was noted that treatment of SIRT1-.transfected cells with Rapamycin, a mTOR inhibitor, reduced the phosphorylation of S6K1 and the expression of Id1, implying that SIRT1-induced phosphorylation of S6K1 may be partly for the decreased expression of p16(INK4A) and promoted phosphorylation of Rb in 2BS. It was also observed that the expression of SIRT1 and phosphorylation of ERK and S6K1 was declined in senescent 2BS. These findings suggested that SIRT1-promoted cell proliferation and antagonized cellular senescence in human diploid fibroblasts may be, in part, via the activation of ERK/ S6K1 signaling.
authors.affiliation: Peking University Research Center on Aging, Beijing, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Huang
authors.forename: Qini
authors.initials: Q
authors.lastname: Gan
authors.forename: Limin
authors.initials: L
authors.lastname: Han
authors.forename: Jian
authors.initials: J
authors.lastname: Li
authors.forename: Hai
authors.initials: H
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Sun
authors.forename: Zongyu
authors.initials: Z
authors.lastname: Zhang
authors.forename: Tanjun
authors.initials: T
authors.lastname: Tong
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D015153:Blotting, Western; D002453:Cell Cycle / Q000502:physiology; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000502:physiology*; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D004171:Diploidy; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D010766:Phosphorylation; D016160:Retinoblastoma Protein / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism*; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D056564:Sirtuin 1; D037761:Sirtuins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D000903:Antibiotics, Antineoplastic; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016160:Retinoblastoma Protein; D019893:Ribosomal Protein S6 Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D001616:beta-Galactosidase; C447939:SIRT1 protein, human; D056564:Sirtuin 1; D037761:Sirtuins; D020123:Sirolimus