The regulatory domain of the RIG-I family ATPase LGP2 senses double-stranded RNA.
RIG-I and MDA5 sense cytoplasmic viral RNA and set-off a signal transduction cascade, leading to antiviral innate immune response. The third RIG-I-like receptor, LGP2, differentially regulates RIG-I- and MDA5-dependent RNA sensing in an unknown manner. All three receptors possess a C-terminal regulatory domain (RD), which in the case of RIG-I senses the viral pattern 5'-triphosphate RNA and activates ATP-dependent signaling by RIG-I. Here we report the 2.6 A crystal structure of LGP2 RD along with in vitro and in vivo functional analyses and a homology model of MDA5 RD. Although LGP2 RD is structurally related to RIG-I RD, we find it rather binds double-stranded RNA (dsRNA) and this binding is independent of 5'-triphosphates. We identify conserved and receptor-specific parts of the RNA binding site. Latter are required for specific dsRNA binding by LGP2 RD and could confer pattern selectivity between RIG-I-like receptors. Our data furthermore suggest that LGP2 RD modulates RIG-I-dependent signaling via competition for dsRNA, another pattern sensed by RIG-I, while a fully functional LGP2 is required to augment MDA5-dependent signaling.
Pippig
Diana A
DA
Department of Chemistry and Biochemistry, Gene Center, Ludwig-Maximilians University Munich, Munich, Germany.
Hellmuth
Johannes C
JC
Cui
Sheng
S
Kirchhofer
Axel
A
Lammens
Katja
K
Lammens
Alfred
A
Schmidt
Andreas
A
Rothenfusser
Simon
S
Hopfner
Karl-Peter
KP
D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D018360:Crystallography, X-Ray; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D000072640:Interferon-Induced Helicase, IFIH1; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011122:Polyphosphates / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000737:chemistry* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry*; D011971:Receptors, Immunologic; D053838:Scattering, Small Angle; D015398:Signal Transduction; D014961:X-Ray Diffraction
D011122:Polyphosphates; D012330:RNA, Double-Stranded; D016601:RNA-Binding Proteins; D011971:Receptors, Immunologic; C520569:DHX58 protein, human; C452820:RIGI protein, human; C452815:IFIH1 protein, human; D000071457:DEAD Box Protein 58; D053487:DEAD-box RNA Helicases; D000072640:Interferon-Induced Helicase, IFIH1; D020365:RNA Helicases; C005692:triphosphoric acid