title: Activating transcription factor 3 regulates canonical TGFβ signalling in systemic sclerosis.
abstract: BACKGROUND
  Activating transcription factor 3 (ATF3), a member of the ATF/cAMP-responsive element binding (CREB) family of transcription factors, regulates cellular response to stress including oxidative stress. The aim of this study was to analyse the role of ATF3 in fibroblast activation in systemic sclerosis (SSc).
  
  
  METHODS
  ATF3 was analysed by reverse transcription quantitative PCR, western blot and immunohistochemistry. ATF3 knockout fibroblasts and mice were used to study the functional role of ATF3. Knockdown experiments, reporter assays and coimmunoprecipitation were performed to study the effects of ATF3 on Smad and activation protein 1 (AP-1) signalling. The role of c-Jun was analysed by costaining, specific inactivation and coimmunoprecipitation.
  
  
  RESULTS
  Transforming growth factor-β (TGFβ) upregulates the expression of ATF3 in SSc fibroblasts. ATF3-deficient fibroblasts were less sensitive to TGFβ, whereas ectopic expression of ATF3 enhanced the profibrotic effects of TGFβ. Mechanistically, ATF3 interacts with Smad3 directly on stimulation with TGFβ and regulates Smad activity in a c-Jun-dependent manner. Knockout of ATF3 protected mice from bleomycin-induced fibrosis and fibrosis induced by overexpression of a constitutively active TGFβ receptor I. Reporter assays and analyses of the expression of Smad target genes demonstrated that binding of ATF3 regulates the transcriptional activity of Smad3.
  
  
  CONCLUSIONS
  We demonstrate for the first time a key role for ATF3 in fibrosis. Knockout of the ATF3 gene reduced the stimulatory effect of TGFβ on fibroblasts by interfering with canonical Smad signalling and protected the mice from experimental fibrosis in two different models. ATF3 might thus be a candidate for molecular targeted therapies for SSc.
authors.affiliation: Department of Internal Medicine 3, Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Tatjana
authors.initials: T
authors.lastname: Mallano
authors.affiliation: Department of Internal Medicine 3, Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Palumbo-Zerr
authors.affiliation: Department of Internal Medicine 3, Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Pawel
authors.initials: P
authors.lastname: Zerr
authors.affiliation: Department of Internal Medicine 3, Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ramming
authors.affiliation: Department of Internal Medicine 3, Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Zeller
authors.affiliation: Department of Internal Medicine 3, Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Beyer
authors.affiliation: Department of Internal Medicine 3, Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Clara
authors.initials: C
authors.lastname: Dees
authors.affiliation: Department of Internal Medicine 3, Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Jingang
authors.initials: J
authors.lastname: Huang
authors.affiliation: Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Tsonwin
authors.initials: T
authors.lastname: Hai
authors.affiliation: Rheumaklinik, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Oliver
authors.initials: O
authors.lastname: Distler
authors.affiliation: Department of Internal Medicine 3, Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Schett
authors.affiliation: Department of Internal Medicine 3, Institute for Clinical Immunology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Jörg H W
authors.initials: JH
authors.lastname: Distler
mesh_terms: D051700:Activating Transcription Factor 3 / Q000235:genetics*; D000328:Adult; D000368:Aged; D000818:Animals; D015153:Blotting, Western; D016022:Case-Control Studies; D020405:Dermis / Q000166:cytology; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D005355:Fibrosis / Q000235:genetics; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D017346:Protein Serine-Threonine Kinases; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012595:Scleroderma, Systemic / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D051900:Smad3 Protein / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D055815:Young Adult
chemical_list: C490449:ATF3 protein, human; D051700:Activating Transcription Factor 3; C103002:Atf3 protein, mouse; D016755:Proto-Oncogene Proteins c-jun; D018125:Receptors, Transforming Growth Factor beta; D051900:Smad3 Protein; D018808:Transcription Factor AP-1; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I
keywords: Fibroblasts; Systemic Sclerosis; Treatment