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Duic I, Tadakuma H, Harada Y, Yamaue R, Deguchi K, Suzuki Y, Yoshimura SH, Kato H, Takeyasu K, Fujita T. Viral RNA recognition by LGP2 and MDA5, and activation of signaling through step-by-step conformational changes. Nucleic Acids Res 2021; 48:11664-11674. [PMID: 33137199 PMCID: PMC7672446 DOI: 10.1093/nar/gkaa935] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 10/03/2020] [Accepted: 10/20/2020] [Indexed: 12/20/2022] Open
Abstract
Cytoplasmic RIG-I-like receptor (RLR) proteins in mammalian cells recognize viral RNA and initiate an antiviral response that results in IFN-β induction. Melanoma differentiation-associated protein 5 (MDA5) forms fibers along viral dsRNA and propagates an antiviral response via a signaling domain, the tandem CARD. The most enigmatic RLR, laboratory of genetics and physiology (LGP2), lacks the signaling domain but functions in viral sensing through cooperation with MDA5. However, it remains unclear how LGP2 coordinates fiber formation and subsequent MDA5 activation. We utilized biochemical and biophysical approaches to observe fiber formation and the conformation of MDA5. LGP2 facilitated MDA5 fiber assembly. LGP2 was incorporated into the fibers with an average inter-molecular distance of 32 nm, suggesting the formation of hetero-oligomers with MDA5. Furthermore, limited protease digestion revealed that LGP2 induces significant conformational changes on MDA5, promoting exposure of its CARDs. Although the fibers were efficiently dissociated by ATP hydrolysis, MDA5 maintained its active conformation to participate in downstream signaling. Our study demonstrated the coordinated actions of LGP2 and MDA5, where LGP2 acts as an MDA5 nucleator and requisite partner in the conversion of MDA5 to an active conformation. We revealed a mechanistic basis for LGP2-mediated regulation of MDA5 antiviral innate immune responses.
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Affiliation(s)
- Ivana Duic
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan.,Laboratory of Molecular Genetics, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto 606-8397, Japan
| | - Hisashi Tadakuma
- Division of Protein Chemistry, Institute for Protein Research, Osaka University, Osaka 565-0871, Japan.,School of Life Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Yoshie Harada
- Division of Protein Chemistry, Institute for Protein Research, Osaka University, Osaka 565-0871, Japan
| | - Ryo Yamaue
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan.,Laboratory of Molecular Genetics, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto 606-8397, Japan
| | - Katashi Deguchi
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Yuki Suzuki
- Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan
| | - Shige H Yoshimura
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Hiroki Kato
- Laboratory of Molecular Genetics, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto 606-8397, Japan.,Institute for Cardiovascular Immunology, University Hospital Bonn, University of Bonn, Bonn 53127, Germany
| | - Kunio Takeyasu
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Takashi Fujita
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan.,Laboratory of Molecular Genetics, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto 606-8397, Japan.,Institute for Cardiovascular Immunology, University Hospital Bonn, University of Bonn, Bonn 53127, Germany
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