WbuB, a glycosyltransferase family 4 protein, regulates the activation of NLRP3 inflammasome and contributes to the virulence of Aeromonas hydrophila CCL1

Abstract

Aeromonas hydrophila is an opportunistic pathogen of fishes and aquatic animals. A. hydrophila has a strong ability to disrupt gut integrity and cause inflammation and septicemia in fish, however, the mechanism is not fully understood. In this study, we identified the function of a galactosaminogalactan (GAG) synthase (named WbuB) in the pathogenic A. hydrophila CCL1. WbuB belongs to the family 4 of glycosyltransferases (GT4) and is composed of 407 amino acids (aa). For virulence analysis, the mutant which has an in-frame deletion of the WbuB gene in CCL1 was created (named ΔWbuB). ΔWbuB had the decreased biofilm formation, as well as adhesion ability and cytotoxicity. Animal infection study in crucian carps showed that, compared to CCL1, ΔWbuB caused the decreased expression levels of ASC, NLRP3, caspase-1 and IL-1β in gut. Moreover, the expression levels of ZO-1 and Occludin were increased by ΔWbuB infection. In line with the results, the intestinal permeability and tissue dissemination capacity of ΔWbuB were attenuated significantly. These lost virulence capacities of ΔWbuB were restored by complementation with the WbuB gene. Taken together, these results indicate that WbuB is essential for the activation of NLRP3 inflammasome and is a novel virulent factor for tight junction barrier during A. hydrophila infection.