Required for innate immune defense against viruses (PubMed:24037184). Acts downstream of DHX33, DDX58/RIG-I and IFIH1/MDA5, which detect intracellular dsRNA produced during viral replication, to coordinate pathways leading to the activation of NF-kappa-B, IRF3 and IRF7, and to the subsequent induction of antiviral cytokines such as IFN-beta and RANTES (CCL5) (PubMed:24037184). Peroxisomal and mitochondrial MAVS act sequentially to create an antiviral cellular state (By similarity). Upon viral infection, peroxisomal MAVS induces the rapid interferon-independent expression of defense factors that provide short-term protection, whereas mitochondrial MAVS activates an interferon-dependent signaling pathway with delayed kinetics, which amplifies and stabilizes the antiviral response (By similarity). May activate the same pathways following detection of extracellular dsRNA by TLR3 (By similarity). May protect cells from apoptosis (By similarity). Self-associates and polymerizes (via CARD domains) to form 400 nM long three-stranded helical filaments on mitochondria, filament nucleation requires interaction with DDX58/RIG-I whose CARD domains act as a template for filament assembly (By similarity). Interacts with DDX58/RIG-I, IFIH1/MDA5, TRAF2, TRAF6 and C1QBP (By similarity). May interact with FADD, RIPK1, IKBKE, CHUK and IKBKB (By similarity). Interacts (when phosphorylated) with IRF3; following activation and phosphorylation on the pLxIS motif by TBK1, recruits IRF3 (By similarity). Interacts with NLRX1 (By similarity). Interaction with NLRX1 requires the CARD domain (By similarity). Interacts with PSMA7 (By similarity). Interacts with TRAFD1 (PubMed:18849341). Interacts (via C-terminus) with PCBP2 in a complex containing MAVS/IPS1, PCBP2 and ITCH (By similarity). Interacts with CYLD (By similarity). Interacts with SRC (By similarity). Interacts with DHX58/LGP2 and IKBKE (By similarity). Interacts with STING1 (By similarity). Interacts with IFIT3 (via N-terminus) (By similarity). Interacts with TBK1 only in the presence of IFIT3 (By similarity). Interacts with TTLL12; the interaction prevents MAVS binding to TBK1 and IKBKE (By similarity). Interacts with MUL1 (By similarity). Interacts with ANKRD17 (By similarity). Interacts with NDFIP1 (By similarity). Interacts with SMURF1; the interaction is mediated by NDFIP1 and leads to MAVS ubiquitination and degradation (PubMed:23087404). Interacts (via C-terminus) with GPATCH3; the interaction is markedly increased upon viral infection (By similarity). Directly interacts (via CARD domain) with ATG5 and ATG12, either as ATG5 and ATG12 monomers or as ATG12-ATG5 conjugates (By similarity). Interacts with DHX33 (via the helicase C-terminal domain) (PubMed:24037184). Interacts with DDX3X (via C-terminus); this interaction may occur rapidly, but transiently after viral infection (By similarity). The interaction with DDX3X potentiates MAVS-mediated IFNB induction (By similarity). Conversely inhibition of this interaction prevents MAVS-mediated IFNB induction (By similarity). Transiently interacts with TRAF3 early during viral infection (By similarity). Interacts with CLPB (By similarity). Interacts with TRAF3IP3 (By similarity). Interacts with TOMM70; the interaction is enhanced by virus infection (By similarity). Interacts with ZNFX1 (PubMed:31685995). Interacts with DHX15 (By similarity). Interacts with N4BP3; this interaction promotes the polyubiquitination of MAVS (By similarity). Both CARD and transmembrane domains are essential for antiviral function. The CARD domain is responsible for interaction with DDX58/RIG-I and IFIH1/MDA5 (By similarity). The transmembrane domain and residues 285-420 are essential for its interaction with DHX58/LGP2. The pLxIS motif constitutes an IRF3-binding motif: following phosphorylation by TBK1, the phosphorylated pLxIS motif of MAVS recruits IRF3. IRF3 is then phosphorylated and activated by TBK1 to induce type-I interferons and other cytokines. Both CARD and transmembrane domains are essential for antiviral function. The CARD domain is responsible for interaction with DDX58/RIG-I and IFIH1/MDA5. The transmembrane domain and residues 300-444 are essential for its interaction with DHX58/LGP2. Following activation, phosphorylated by TBK1 at Ser-418 in the pLxIS motif. The phosphorylated pLxIS motif constitutes an IRF3-binding motif, leading to recruitment of the transcription factor IRF3 to induce type-I interferons and other cytokines. Ubiquitinated. Undergoes 'Lys-48'-linked polyubiquitination catalyzed by ITCH; ITCH-dependent polyubiquitination is mediated by the interaction with PCBP2 and leads to MAVS/IPS1 proteasomal degradation. Ubiquitinated by RNF125, leading to its degradation by the proteasome. Undergoes 'Lys-48'-linked ubiquitination catalyzed by SMURF1. Undergoes 'Lys-63'-linked ubiquitination leading to enhanced interaction between MAVS and TRAF2. Proteolytically cleaved by apoptotic caspases during apoptosis, leading to its inactivation. Cleavage by CASP3 during virus-induced apoptosis inactivates it, preventing cytokine overproduction.