Identification and Functional Characterization of an Ancestral Hepcidin-Like Antimicrobial Peptide in the Lamprey (Lethenteron camtschaticum).

Hepcidin, also known as LEAP-1 (liver-expressed antimicrobial peptide), is a cysteine-rich, cationic antimicrobial peptide found in vertebrates that plays a key role in iron transport and immune response. Although hepcidin has been characterized in various vertebrates, including fish and mammals, its evolutionary origin remains unclear. In this study, the ancestral hepcidin gene (named Lc-HAMP) was cloned and characterized from the liver of the primitive jawless vertebrate Lethenteron camtschaticum (lamprey). The gene encodes a 25-amino-acids signal peptide and a mature 23-amino- acids peptide. Despite relatively low sequence similarity with other species, the mature Lc-HAMP peptide retains eight conserved cysteine residues that form a core structure of four disulfide bonds. Lc-HAMP expression is significantly upregulated upon multiple immune challenges, and the mature peptide exhibits dose-dependent in vitro antimicrobial activity against a wide range of bacteria, including Staphylococcus aureus, Staphylococcus epidermidis, and Aeromonas, but shows no activity against Escherichia coli and Pseudomonas aeruginosa. Lc-HAMP induces bacterial membrane damage and triggers reactive oxygen species (ROS) bursts in bacteria. Transcriptomic and metabolomic analyses indicate that overexpression of Lc-HAMP in HEK293T cells affects endoplasmic reticulum stress and glutathione metabolism, similarly to observations in higher vertebrates. These findings shed light on the evolutionary origin of hepcidin, a key antimicrobial peptide, and suggest potential strategies for preventing and controlling immunosuppression in lower vertebrates such as fish.