title: ADAM15 adds to apoptosis resistance of synovial fibroblasts by modulating focal adhesion kinase signaling.
abstract: OBJECTIVE
  To study the contribution of ADAM15, a disintegrin metalloproteinase that is up-regulated in the rheumatoid arthritis (RA) synovial membrane, to the characteristic resistance of RA synovial fibroblasts (RASFs) to apoptosis induction by genotoxic stress or stimulation with proapoptotic FasL, which is present at high concentrations in RA synovial fluid.
  
  
  METHODS
  Caspase 3/7 activity and the total apoptosis rate in RASFs upon exposure to the DNA-damaging agent camptothecin or FasL were determined using enzyme assays and annexin V staining. Phosphorylated signaling proteins were analyzed by immunoblotting. RNA interference was used to silence ADAM15 expression. NF-κB activity was determined by enzyme-linked immunosorbent assay.
  
  
  RESULTS
  RASFs displayed significantly higher caspase 3/7 activity upon camptothecin and FasL exposure when ADAM15 had been down-regulated by specific small interfering RNAs. Upon FasL stimulation, RASFs phosphorylated focal adhesion kinase (FAK) and c-Src (Src), and activated phosphatidylinositol 3-kinase as well as the transcription factor NF-κB. This ADAM15-dependent, FasL-induced activation of antiapoptotic kinases and NF-κB was demonstrated by a marked reduction of apoptosis upon knockdown of ADAM15 protein expression. Inhibitors specifically interfering with FAK and Src signaling, such as FAK inhibitor 14 and dasatinib, potently induce apoptosis in RASFs, with significant enhancement by the silencing of ADAM15.
  
  
  CONCLUSIONS
  ADAM15 contributes to apoptosis resistance in RASFs by activating the Src/FAK pathway upon FasL exposure, rendering the FAK/Src signaling pathway an interesting target for potential therapeutic intervention in RA.
authors.affiliation: Johann Wolfgang Goethe University, Frankfurt am Main, Germany.
authors.forename: Beate B
authors.initials: BB
authors.lastname: Böhm
authors.forename: Isabell
authors.initials: I
authors.lastname: Freund
authors.forename: Kristin
authors.initials: K
authors.lastname: Krause
authors.forename: Raimund W
authors.initials: RW
authors.lastname: Kinne
authors.forename: Harald
authors.initials: H
authors.lastname: Burkhardt
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001172:Arthritis, Rheumatoid / Q000378:metabolism* / Q000473:pathology*; D001706:Biopsy; D002166:Camptothecin / Q000494:pharmacology; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D053222:Fas Ligand Protein / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013583:Synovial Membrane / Q000378:metabolism / Q000473:pathology; D015854:Up-Regulation / Q000502:physiology
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D053222:Fas Ligand Protein; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; C505407:CASP3 protein, human; C505520:CASP7 protein, human; D053148:Caspase 3; D053179:Caspase 7; D051722:ADAM Proteins; C098660:ADAM15 protein, human; D002166:Camptothecin