Signaling events induced by lipopolysaccharide-activated Toll in response to bacterial infection in shrimp.

Toll-like receptors (TLR) play a crucial role in the detection of microbial infections in vertebrates and invertebrates. Mammalian TLRs directly recognize a variety of structurally conserved microbial components. However, invertebrates such as Drosophila indirectly recognize microbial products by binding to the cytokine-like ligand Spätzle, which activates signaling cascades that are not completely understood. In this study, we investigated the signaling events triggered by Toll in response to lipopolysaccharide (LPS), a cell wall component of gram-negative bacteria, and infection in the arthropod shrimp . We found that five of the nine Tolls from bound to LPS and the RNAi of LvToll1, LvToll2, LvToll3, LvToll5, and LvToll9 weakened LvDorsal-L phosphorylation induced by . All nine Tolls combined with MyD88 the TIR domain, thereby conferring signals to the tumor necrosis factor receptor-associated factor 6 (TRAF6)-transforming growth factor-β activated kinase 1 binding protein 2 (TAB2)-transforming growth factor-β activated kinase 1 (TAK1) complex. Further examination revealed that the LvTRAF6-LvTAB2-LvTAK1 complex contributes to Dorsal-L phosphorylation and nuclear translocation during infection. Overall, shrimp Toll1/2/3/5/9-TRAF6/TAB2/TAK1-Dorsal cascades protect the host from infection, which provides a better understanding of how the innate immune system recognizes and responds to bacterial infections in invertebrates.