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. Author manuscript; available in PMC: 2009 Aug 1.
Published in final edited form as: Clin Liver Dis. 2008 Aug;12(3):675–x. doi: 10.1016/j.cld.2008.03.003

Figure 3. Intracytoplasmic viral recognition and antiviral pathways.

Figure 3

The RNA derived from virions is recognized at the helicase domain of the RIG-I, MDA5 or LPG2 helicases. Upon ligand interaction, the tandem caspase activation and recruitment (CARD) domains of RIG-I and MDA5 engage the CARD domain of mitochondria-bound IPS-1 and trigger activation of a series of kinases including IKKα, IKKβ, IKKε and TBK1. These signaling events activate TRAF3, NFκB and IRF, leading to their translocation to the nucleus and initiation of the type 1 IFN production. LPG2 is CARD-less and does not trigger the signaling events, however it modulates the activity of RIG-I by blocking RIG-I self-association, owed to disrupting homotypic CARD/helicase domain and/or C terminus interactions, by disrupting assembly of the RIG-I-containing signaling complex on IPS-1 and by sequestering the viral dsRNA.