Expression of the Shrimp wap gene in Drosophila elicits defense responses and protease inhibitory activity

A triple WAP domain containing protein acts in antibacterial immunity of weather loach, Misgurnus anguillicaudatus

Whey acidic protein domain (WAPD) occurs in a variety of proteins in animals and many of WAPD-containing proteins are involved in immunity. In the present study, a novel protein containing three WAPDs was identified from the weather loach, Misgurnus anguillicaudatus, designated as MaTWD. MaTWD share high identity with TWDs from fish but low identity with TWDs from other animal phyla. MaTWD transcripts mainly distributed in gills and head kidney responded to bacterial challenge with significant upregulation. In vitro assay with recombinant MaTWD protein revealed that MaTWD had antiprotease activity against bacterial proteases. Moreover, MaTWD exhibited bacterial binding capacity and antimicrobial activity. Most importantly, exogenous MaTWD protected loach against bacterial infection by reducing loach mortality. We infer that MaTWD participates in the antibacterial immunity of loach via its antiprotease and antimicrobial activities.