Intracellular delivery of poly(I:C) induces apoptosis of fibroblast-like synoviocytes via an unknown dsRNA sensor

• DOI: 10.1016/j.bbrc.2016.06.104
• Publication Date: 2016-06-23T08:51:00Z
• Authors: Olga N. Karpus; Cheng-Chih Hsiao; Hanneke de Kort; Paul P. Tak; Jörg Hamann
• Keywords: 0301 basic medicine; 03 medical and health sciences; Interferon-Induced Helicase, IFIH1; Poly I-C; Gene Knockdown Techniques; Humans; Apoptosis; Synoviocytes; RNA, Double-Stranded

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.