1. Contrasting functions of ATP hydrolysis by MDA5 and LGP2 in viral RNA sensing.
- Author
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Singh R, Wu Y, Herrero Del Valle A, Leigh KE, Mong S, Cheng MTK, Ferguson BJ, and Modis Y
- Subjects
- Adenosine Triphosphate metabolism, Hydrolysis, Immunity, Innate, Nucleoside-Triphosphatase genetics, Nucleoside-Triphosphatase metabolism, Humans, DEAD-box RNA Helicases metabolism, Interferon-Induced Helicase, IFIH1 genetics, Interferon-Induced Helicase, IFIH1 metabolism, RNA Helicases metabolism, RNA, Double-Stranded metabolism, RNA, Viral genetics, RNA, Viral metabolism
- Abstract
Cytosolic long dsRNA, among the most potent proinflammatory signals, is recognized by melanoma differentiation-associated protein 5 (MDA5). MDA5 binds dsRNA cooperatively forming helical filaments. ATP hydrolysis by MDA5 fulfills a proofreading function by promoting dissociation of shorter endogenous dsRNs from MDA5 while allowing longer viral dsRNAs to remain bound leading to activation of interferon-β responses. Here, we show that adjacent MDA5 subunits in MDA5-dsRNA filaments hydrolyze ATP cooperatively, inducing cooperative filament disassembly. Consecutive rounds of ATP hydrolysis amplify the filament footprint, displacing tightly bound proteins from dsRNA. Our electron microscopy and biochemical assays show that LGP2 binds to dsRNA at internal binding sites through noncooperative ATP hydrolysis. Unlike MDA5, LGP2 has low nucleic acid selectivity and can hydrolyze GTP and CTP as well as ATP. Binding of LGP2 to dsRNA promotes nucleation of MDA5 filament assembly resulting in shorter filaments. Molecular modeling identifies an internally bound MDA5-LGP2-RNA complex, with the LGP2 C-terminal tail forming the key contacts with MDA5. These contacts are specifically required for NTP-dependent internal RNA binding. We conclude that NTPase-dependent binding of LGP2 to internal dsRNA sites complements NTPase-independent binding to dsRNA ends, via distinct binding modes, to increase the number and signaling output of MDA5-dsRNA complexes., Competing Interests: Conflict of interest Y. M. is a consultant for Related Sciences LLC and has profits interests in Danger Bio LLC. B. J. F. is an Editorial Board Member for the Journal of Biological Chemistry and was not involved in the editorial review or the decision to publish this article. None of the other authors have any conflicts of interest with the contents of this article., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2024
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