Meeting Abstract
Innate immunity pathways are shared among all animals to detect conserved surface molecular motifs used by pathogenic microbes. In animals, the Toll-like receptor (TLR) pathway is defined by Toll/interleukin receptor (TIR) domains to bind these pathogens. The TLR pathway has several highly conserved TIR domain-containing proteins that have been well characterized in model organisms. In this study, we analyze one such TIR domain-containing protein, SARM1, in Deuterostomia and Lophotrochozoa. In jawed vertebrates, SARM1 inhibits the MYD88-independent TCAM1-dependent pathway via a negative regulator loop. In other lineages, SARM1 function is unknown. Although a TCAM1 homolog is absent in many invertebrate lineages, SARM1 is present and has been hypothesized to play a role in neuron physiology, innate immunity, or both. Our results confirm the hypothesis that SARM1 is indeed a conserved protein. SARM1 is characterized by two N-terminal sterile alpha motif (SAM) domains and a single C-terminal TIR domain. SARM1 is present in all sampled taxa, but has variability in total length, domain placement, and domain characterization. These findings emphasize the importance of sampling across all taxonomic groups to reveal evolutionary patterns, novel function, and protein composition. Given that SARM1 is conserved across a broad range of Metazoa, future work is needed to understand how this protein is functionally utilized in invertebrate taxa.
