ATP release channel Pannexin1 is a novel immune response gene in Japanese flounder Paralichthys olivaceus.

Extracellular ATP is an important damage-associated molecular pattern molecule that plays key roles in innate immunity. In fish, however, the mechanism for extracellular ATP release remains largely undefined. Pannexin1 (Panx1) is a newly discovered extracellular ATP release channel with a wide tissue distribution and diverse biological functions in mammals. In the present study, we identified and characterized a Panx1 homolog cDNA, termed poPanx1, from Japanese flounder Paralichthys olivaceus, which is one of the most important economic mariculture fish species in China. PoPanx1 is a membrane protein that is composed of 437 amino acids with an estimated molecular mass of 48.7 kDa and an isoelectric point of 6.46. The poPanx1 mRNA ubiquitously expresses in all examined tissues but with predominant expression in hepatopancreas in unstimulated healthy adult Japanese flounder. In Japanese flounder head kidney primary cells, poPanx1 gene expression could be significantly induced by pathogen-associated molecular patterns (PAMPs; polyinosinic-polycytidylic acid and bacterial endotoxin LPS) stimulations. In vivo experiments revealed that poPanx1 mRNA expression was significantly up-regulated upon immune challenges with Edwardsiella tarda and Vibrio anguillarum. Furthermore, we showed that poPanx1 is an important channel protein for PAMP-induced extracellular ATP release that is required for activation of purinergic signaling in fish innate immunity. Taken together, our findings suggest that the ATP release channel, poPanx1, is a novel immune response gene in purinergic signaling of Japanese flounder P. olivaceus.