title: Inhibition of SIRT1 impairs the accumulation and transcriptional activity of HIF-1α protein under hypoxic conditions.
abstract: Sirtuins and hypoxia-inducible transcription factors (HIF) have well-established roles in regulating cellular responses to metabolic and oxidative stress. Recent reports have linked these two protein families by demonstrating that sirtuins can regulate the activity of HIF-1 and HIF-2. Here we investigated the role of SIRT1, a NAD+-dependent deacetylase, in the regulation of HIF-1 activity in hypoxic conditions. Our results show that in hepatocellular carcinoma (HCC) cell lines, hypoxia did not alter SIRT1 mRNA or protein expression, whereas it predictably led to the accumulation of HIF-1α and the up-regulation of its target genes. In hypoxic models in vitro and in in vivo models of systemic hypoxia and xenograft tumor growth, knockdown of SIRT1 protein with shRNA or inhibition of its activity with small molecule inhibitors impaired the accumulation of HIF-1α protein and the transcriptional increase of its target genes. In addition, endogenous SIRT1 and HIF-1α proteins co-immunoprecipitated and loss of SIRT1 activity led to a hyperacetylation of HIF-1α. Taken together, our data suggest that HIF-1α and SIRT1 proteins interact in HCC cells and that HIF-1α is a target of SIRT1 deacetylase activity. Moreover, SIRT1 is necessary for HIF-1α protein accumulation and activation of HIF-1 target genes under hypoxic conditions.
authors.affiliation: Clinic of Visceral Surgery and Medicine, Visceral and Transplantation Surgery, University Hospital Bern and University of Bern, Bern, Switzerland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Laemmle
authors.forename: Antje
authors.initials: A
authors.lastname: Lechleiter
authors.forename: Vincent
authors.initials: V
authors.lastname: Roh
authors.forename: Christa
authors.initials: C
authors.lastname: Schwarz
authors.forename: Simone
authors.initials: S
authors.lastname: Portmann
authors.forename: Cynthia
authors.initials: C
authors.lastname: Furer
authors.forename: Adrian
authors.initials: A
authors.lastname: Keogh
authors.forename: Mario P
authors.initials: MP
authors.lastname: Tschan
authors.forename: Daniel
authors.initials: D
authors.lastname: Candinas
authors.forename: Stephan A
authors.initials: SA
authors.lastname: Vorburger
authors.forename: Deborah
authors.initials: D
authors.lastname: Stroka
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D056945:Hep G2 Cells; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D008819:Mice, Nude; D009281:Naphthalenes / Q000494:pharmacology; D009284:Naphthols / Q000494:pharmacology; D011485:Protein Binding; D011744:Pyrimidinones / Q000494:pharmacology; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D056564:Sirtuin 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014183:Transplantation, Heterologous; D047368:Tumor Burden / Q000187:drug effects
chemical_list: D001549:Benzamides; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009281:Naphthalenes; D009284:Naphthols; D011744:Pyrimidinones; C510718:cambinol; C439060:sirtinol; C447939:SIRT1 protein, human; D056564:Sirtuin 1