title: Bass hepcidin synthesis, solution structure, antimicrobial activities and synergism, and in vivo hepatic response to bacterial infections.
abstract: Bass hepcidin was purified from the gill of hybrid striped bass (Morone chrysops x Morone saxatilis) based on antimicrobial activity against Escherichia coli. This 21-amino acid peptide has 8 cysteines engaged in 4 disulfide bonds and is very similar to human hepcidin, an antimicrobial peptide with iron regulatory properties. To gain insight into potential role(s) of bass hepcidin in innate immunity in fish, we synthesized the peptide, characterized its antimicrobial activities in vitro, determined its solution structure by NMR, and quantified hepatic gene expression in vivo following infection of bass with the fish pathogens, Streptococcus iniae or Aeromonas salmonicida. Its structure is very similar to that of human hepcidin, including the presence of an antiparallel beta-sheet, a conserved disulfide-bonding pattern, and a rare vicinal disulfide bond. Synthetic bass hepcidin was active in vitro against Gram-negative pathogens and fungi but showed no activity against key Gram-positive pathogens and a single yeast strain tested. Hepcidin was non-hemolytic at microbicidal concentrations and had lower specific activity than moronecidin, a broad spectrum, amphipathic, alpha-helical, antimicrobial peptide constitutively expressed in bass gill tissue. Good synergism between the bacterial killing activities of hepcidin and moronecidin was observed in vitro. Hepcidin gene expression in bass liver increased significantly within hours of infection with Gram-positive (S. iniae) or Gram-negative (A. salmonicida) pathogens and was 4-5 orders of magnitude above base-line 24-48 h post-infection. Our results suggest that hepcidin plays a key role in the antimicrobial defenses of bass and that its functions are potentially conserved between fish and human.
authors.affiliation: Department of Pediatrics, University of California San Diego, School of Medicine, San Diego, California 92093, USA.
authors.forename: Xavier
authors.initials: X
authors.lastname: Lauth
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Babon
authors.forename: Jason A
authors.initials: JA
authors.lastname: Stannard
authors.forename: Satendra
authors.initials: S
authors.lastname: Singh
authors.forename: Victor
authors.initials: V
authors.lastname: Nizet
authors.forename: James M
authors.initials: JM
authors.lastname: Carlberg
authors.forename: Vaughn E
authors.initials: VE
authors.lastname: Ostland
authors.forename: Michael W
authors.initials: MW
authors.lastname: Pennington
authors.forename: Raymond S
authors.initials: RS
authors.lastname: Norton
authors.forename: Mark E
authors.initials: ME
authors.lastname: Westerman
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000096:biosynthesis* / Q000737:chemistry* / Q000494:pharmacology; D001424:Bacterial Infections / Q000517:prevention & control; D001483:Base Sequence; D001492:Bass / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D017931:DNA Primers; D004220:Disulfides / Q000032:analysis; D005393:Fish Diseases / Q000517:prevention & control; D064451:Hepcidins; D008099:Liver / Q000382:microbiology*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D023181:Antimicrobial Cationic Peptides; D017931:DNA Primers; D004220:Disulfides; C578702:HAMP protein, human; D064451:Hepcidins