A novel Toll receptor from Pacific white shrimp Penaeus vannamei is involved in immune defense against Vibrio parahaemolyticus infection

Tolls/Toll-like receptors (TLRs) are a group of pattern recognition receptors (PRRs) that play central roles in the regulation of immune responses by sensing invading pathogens and initiating the downstream signaling pathways. In this study, a novel Toll (Toll10) from pacific white shrimp Penaeus vannamei has been identified and functionally studied in the context of immunity to bacterial infection. Toll10 has a series of tandem leucine-rich repeats (LRR) in the extracellular region but not a Toll/interleukin-1(IL-1) receptor homologous region (TIR) in the intracellular region. The Toll10 protein mainly locates on the cell membrane and its expression is upregulated upon bacterial infection. The recombinant Toll10 protein can directly bind bacteria, and silencing of Toll10 increases the susceptibility of shrimp to Vibrio parahaemolyticus infection and inhibits the phagocytosis of V. parahaemolyticus by hemocytes. Moreover, Toll10 promotes the phosphorylation and nuclear translocation of the NF-KB family member Dorsal and positively regulates the expression of Dorsal-targeted antimicrobial peptide genes. This indicates that Toll10 mediates a signaling pathway to activate Dorsal and is important for antibacterial immune response in P. vannamei. The current study is helpful for the revelation of the regulatory mechanism of immune defense in shrimp against V. parahaemolyticus infection.