title: SIRT1 inhibits transforming growth factor beta-induced apoptosis in glomerular mesangial cells via Smad7 deacetylation.
abstract: SIRT1, a class III histone deacetylase, is considered a key regulator of cell survival and apoptosis through its interaction with nuclear proteins. In this study, we have examined the likelihood and role of the interaction between SIRT1 and Smad7, which mediates transforming growth factor beta (TGFbeta)-induced apoptosis in renal glomerular mesangial cells. Immunoprecipitation analysis revealed that SIRT1 directly interacts with the N terminus of Smad7. Furthermore, SIRT1 reversed acetyl-transferase (p300)-mediated acetylation of two lysine residues (Lys-64 and -70) on Smad7. In mesangial cells, the Smad7 expression level was reduced by SIRT1 overexpression and increased by SIRT1 knockdown. SIRT1-mediated deacetylation of Smad7 enhanced Smad ubiquitination regulatory factor 1 (Smurf1)-mediated ubiquitin proteasome degradation, which contributed to the low expression of Smad7 in SIRT1-overexpressing mesangial cells. Stimulation by TGFbeta or overexpression of Smad7 induced mesangial cell apoptosis, as assessed by morphological apoptotic changes (nuclear condensation) and biological apoptotic markers (cleavages of caspase3 and poly(ADP-ribose) polymerase). However, TGFbeta failed to induce apoptosis in Smad7 knockdown mesangial cells, indicating that Smad7 mainly mediates TGFbeta-induced apoptosis of mesangial cells. Finally, SIRT1 overexpression attenuated both Smad7- and TGFbeta-induced mesangial cell apoptosis, whereas SIRT1 knockdown enhanced this apoptosis. We have concluded that Smad7 is a new target molecule for SIRT1 and SIRT1 attenuates TGFbeta-induced mesangial cell apoptosis through acceleration of Smad7 degradation. Our results suggest that up-regulation of SIRT1 deacetylase activity is a potentially useful therapeutic strategy for prevention of TGFbeta-related kidney disease through its effect on cell survival.
authors.affiliation: Department of Medicine, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Kume
authors.forename: Masakazu
authors.initials: M
authors.lastname: Haneda
authors.forename: Keizo
authors.initials: K
authors.lastname: Kanasaki
authors.forename: Toshiro
authors.initials: T
authors.lastname: Sugimoto
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Araki
authors.forename: Keiji
authors.initials: K
authors.lastname: Isshiki
authors.forename: Motohide
authors.initials: M
authors.lastname: Isono
authors.forename: Takashi
authors.initials: T
authors.lastname: Uzu
authors.forename: Leonard
authors.initials: L
authors.lastname: Guarente
authors.forename: Atsunori
authors.initials: A
authors.lastname: Kashiwagi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Koya
mesh_terms: D000818:Animals; D017209:Apoptosis; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D004247:DNA / Q000737:chemistry; D005920:Glomerular Mesangium / Q000166:cytology*; D007668:Kidney / Q000378:metabolism; D051379:Mice; D011485:Protein Binding; D012190:Retroviridae / Q000235:genetics; D056564:Sirtuin 1; D037761:Sirtuins / Q000737:chemistry / Q000502:physiology*; D051906:Smad7 Protein / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D051906:Smad7 Protein; D053773:Transforming Growth Factor beta1; D004247:DNA; C470545:Sirt1 protein, mouse; D056564:Sirtuin 1; D037761:Sirtuins