Novel nicotinic acetylcholine receptor involved in immune regulation in pearl oyster (Pinctada fucata martensii).

The cholinergic anti-inflammatory pathway has been identified as a reflex monitoring system that contributes to the physiological and pathological regulation of cytokines. Nicotinic acetylcholine receptor (nAChR) plays an important role in immune regulation as a key molecule in neuronal communication. In this work, we investigated the characteristics and functions of a novel nAChR β gene identified from the pearl oyster Pinctada fucata martensii (PmnAChR-β). PmnAChR-β displays structural similarities to nAChR molecules described in mammals, including a typical neurotransmitter-gated ion-channel ligand binding domain (LBD) and transmembrane (TM) domain. The result of phylogenetic analysis speculated that nAChR-β in Mollusca, Chordata and Arthropoda were separated into three branches. The LBD of PmnAChR-β was highly conserved, but its TM was variable. PmnAChR-β was highly expressed in eggs and fertilized eggs and had the most abundant mRNA expression in the gills of pearl oyster. The expression of PmnAChR-β mRNA was dramatically upregulated 12 h after lipopolysaccharide stimulation. Furthermore, PmnAChR-β was highly expressed at 12 h and 6-18 d after transplantation in hemocytes. Pm-miR-516b-5p was identified as the regulatory microRNA of PmnAChR-β. These results indicated that PmnAChR-β may be an important component of the cholinergic anti-inflammatory pathway and participates in the immune regulation process of pearl oysters.