Host defence peptide LEAP2 contributes to antimicrobial activity in a mustache toad (Leptobrachium liui)

The liver-expressed antimicrobial peptide 2 (LEAP2) is an essential molecule in host immunity against harmful pathogens. In this study, LEAP2 gene (Ll-LEAP2) cDNA was cloned and sequenced from the Chong’an Moustache Toad (Leptobrachium liui). The predicted amino acid sequence of Ll-LEAP2 comprises a signal peptide, a mature peptide, and a prodomain. From sequence analysis, it was revealed that Ll-LEAP2 belongs to the cluster of amphibian LEAP2 and displays high similarity to the Tropical Clawed Frog (Xenopus tropicalis)’s LEAP2. Our study revealed that Ll-LEAP2 mRNA transcripts were expressed in various tissues with the kidney having the highest mRNA expression level. As a result of Aeromonas hydrophila infection, Ll-LEAP2 underwent a noticeable up-regulation in the skin while down-regulated in the intestines of X. tropicalis. The chemically synthesized Ll-LEAP2 mature peptide was selective in its antimicrobial activity against several in vitro bacteria. Additionally, Ll-LEAP2 can kill specific bacteria by disrupting bacterial membrane and hydrolyzing bacterial gDNA. This study is the first report on the antibacterial activity and mechanism of amphibian LEAP2.