A novel invertebrate toll-like receptor is involved in TLR mediated signal pathway of thick shell mussel Mytilus coruscus. (August 2019) - Xu, Kaida
Abstract: Toll-like receptors (TLRs) are the most well studied pattern recognition receptors (PRRs) that play a crucial role in both innate and adaptive immunity in animals. In the present study, a novel toll-like receptor ( Mc TLRj) was identified and characterised in thick shell mussel Mytilus coruscus. Mc TLRj possessed a signal peptide, a transmembrane domain, leucine-rich repeats and an intracellular Toll/interleukin-1 receptor domain that were conserved in typical TLRs. Mc TLRj transcripts were constitutively expressed in all of the examined tissues with high expression level in immune-related tissues, and significantly induced in haemocytes upon live Vibrio alginolyticus, lipopolysaccharide, polyinosinic-polycytidylic acid and peptidoglycans challenge. The overexpression of the Mc TLRj TLR fragment in Drosophila S2 cells could induce the expression of Drosophila attacin A, drosomycin, cecropin A, and metchnikowin expression. The expression of Mc TLRj was obviously repressed by dsRNA-mediated RNA interference, and downstream TLR pathway factors, such as MyD88a, IRAK4, and TRAF6 were significantly repressed in Mc TLRj-silenced mussels upon LPS challenge. These results collectively indicated that Mc TLRj is a TLR family member that may play a potential PRR role in TLR-mediated signalling pathway. This research contributed to the clarification of innate immune response in molluscs. Highlights: One novel TLR molecule Mc TLRj first characterised in M. coruscus. Mc TLRj could be induced by diverse PAMPs. Mc TLRj TLR fragment regulates anti-microbial peptides expression in S2 cells. Mc TLRj could activate the downstream TLR signalling pathway.