title: Intracellular delivery of poly(I:C) induces apoptosis of fibroblast-like synoviocytes via an unknown dsRNA sensor.
abstract: Fibroblast-like synoviocytes (FLS) express functional membranous and cytoplasmic sensors for double-stranded (ds)RNA. Notably, FLS undergo apoptosis upon transfection with the synthetic dsRNA analog poly(I:C). We here studied the mechanism of intracellular poly(I:C) recognition and subsequent cell death in FLS. FLS responded similarly to poly(I:C) or 3pRNA transfection; however, only intracellular delivery of poly(I:C) induced significant cell death, accompanied by upregulation of pro-apoptotic proteins Puma and Noxa, caspase 3 cleavage, and nuclear segregation. Knockdown of the DExD/H-box helicase MDA5 did not affect the response to intracellular poly(I:C); in contrast, knockdown of RIG-I abrogated the response to 3pRNA. Knockdown of the downstream adaptor proteins IPS, STING, and TRIF or inhibition of TBK1 did not affect the response to intracellular poly(I:C), while knockdown of IFNAR blocked intracellular poly(I:C)-mediated signaling and cell death. We conclude that a so far unknown intracellular sensor recognizes linear dsRNA and induces apoptosis in FLS.
authors.affiliation: Departments of Experimental Immunology and Internal Medicine, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Olga N
authors.initials: ON
authors.lastname: Karpus
authors.affiliation: Departments of Experimental Immunology and Internal Medicine, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Cheng-Chih
authors.initials: CC
authors.lastname: Hsiao
authors.affiliation: Departments of Experimental Immunology and Internal Medicine, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Hanneke
authors.initials: H
authors.lastname: de Kort
authors.affiliation: Departments of Experimental Immunology and Internal Medicine, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Paul P
authors.initials: PP
authors.lastname: Tak
authors.affiliation: Departments of Experimental Immunology and Internal Medicine, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands. Electronic address: j.hamann@amc.uva.nl.
authors.forename: Jörg
authors.initials: J
authors.lastname: Hamann
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D055785:Gene Knockdown Techniques; D006801:Humans; D000072640:Interferon-Induced Helicase, IFIH1 / Q000235:genetics; D011070:Poly I-C / Q000008:administration & dosage* / Q000494:pharmacology; D012330:RNA, Double-Stranded / Q000008:administration & dosage*; D000070918:Synoviocytes / Q000166:cytology / Q000187:drug effects*
chemical_list: D012330:RNA, Double-Stranded; C452815:IFIH1 protein, human; D000072640:Interferon-Induced Helicase, IFIH1; D011070:Poly I-C
keywords: Cell death; DExD/H-box helicases; Fibroblast-like synoviocytes; dsRNA