Fig. 7

Conserved and absent elements of anti-viral signaling in Aplysia californica. In vertebrates, pattern recognition receptors for viral nucleotides signal through two major adapter proteins, Stimulator of Interferon Genes (STING) in the case of viral DNA and Mitochondrial Antiviral Signaling protein (MAVS) in the case of viral RNA. Both adapters facilitate the activation of Tank Binding Kinase 1 (TBK1) which activates Interferon Regulatory Factors (IRFs) that upregulate the transcription of Type 1 Interferons (IFN) to martial an antiviral response. Aplysia californica appears to lack orthologs of both STING and MAVS, as well as several viral DNA sensors found in vertebrates (grey filled boxes), suggesting possible divergent signaling pathways. Viral DNA sensors: DNA-dependent activator of IFN regulatory factors (DAI); Pyrin and hematopoietic interferon-inducible nuclear (HIN) domain (PYHIN) such as IFI16 and AIM2; DExD/H-box helicase 41 (DDX41); Cyclic GMP–AMP synthase (cGAS); DNA protein Kinase complex (DNAPK) comprised of DNAPK catalytic subunit (DNAKPKc), Lupus Ku autoantigen protein p70 (Ku70), and Lupus Ku autoantigen protein p80 (Ku80); and the complex made up of Meiotic recombination 11 (MRE11) and DNA repair protein RAD50. RNA sensors are RIG-I-like Receptors (RLR)