Shared and unique functions of the DExD/H-box helicases RIG-I, MDA5, and LGP2 in antiviral innate immunity - PubMed (original) (raw)

. 2005 Sep 1;175(5):2851-8.

doi: 10.4049/jimmunol.175.5.2851.

Mika Kikuchi, Kanae Matsumoto, Tadaatsu Imaizumi, Makoto Miyagishi, Kazunari Taira, Eileen Foy, Yueh-Ming Loo, Michael Gale Jr, Shizuo Akira, Shin Yonehara, Atsushi Kato, Takashi Fujita

Affiliations

Shared and unique functions of the DExD/H-box helicases RIG-I, MDA5, and LGP2 in antiviral innate immunity

Mitsutoshi Yoneyama et al. J Immunol. 2005.

Abstract

The cellular protein retinoic acid-inducible gene I (RIG-I) senses intracellular viral infection and triggers a signal for innate antiviral responses including the production of type I IFN. RIG-I contains a domain that belongs to a DExD/H-box helicase family and exhibits an N-terminal caspase recruitment domain (CARD) homology. There are three genes encoding RIG-I-related proteins in human and mouse genomes. Melanoma differentiation associated gene 5 (MDA5), which consists of CARD and a helicase domain, functions as a positive regulator, similarly to RIG-I. Both proteins sense viral RNA with a helicase domain and transmit a signal downstream by CARD; thus, these proteins share overlapping functions. Another protein, LGP2, lacks the CARD homology and functions as a negative regulator by interfering with the recognition of viral RNA by RIG-I and MDA5. The nonstructural protein 3/4A protein of hepatitis C virus blocks the signaling by RIG-I and MDA5; however, the V protein of the Sendai virus selectively abrogates the MDA5 function. These results highlight ingenious mechanisms for initiating antiviral innate immune responses and the action of virus-encoded inhibitors.

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