title: Molecular and functional characterization of the gilthead seabream β-defensin demonstrate its chemotactic and antimicrobial activity.
abstract: Antimicrobial peptides (AMPs) are important mediators of the innate immune response against bacteria and viruses. We have found a β-defensin (BD) gene searching the expressed sequence tags (ESTs) of the teleost fish gilthead seabream (Sparus aurata). The clone contains an open reading frame of 201 bp mRNA that encodes a putative seabream β-defensin (saBD) propeptide of 66 amino acids containing the six conserved cysteines as the main signature of this AMP. The phylogenetic tree shows that saBD, and its fish orthologues, are closely related to the human BD-4. Transcripts of the saBD gene were mainly detected by real-time PCR in the skin, peritoneal leucocytes and head-kidney but scarcely expressed in the peripheral blood. Interestingly, head-kidney leucocytes incubation with synthetic unmethylated CpG oligodeoxynucleotides and bacterial DNA up-regulated the saBD gene expression. Recombinant protein (saBD-V5-His) was expressed in the HEK293 cell line and its functional activity determined. First, seabream head-kidney leucocytes showed chemotactic activity towards supernatants containing saBD-V5-His whilst failed to do so to human recombinant BD-1 y BD-4. Moreover, both cell lysates and supernatants containing saBD-V5-His showed strong antimicrobial activity against Vibrio anguillarum (a seabream pathogenic bacterium) and Bacillus subtilis whilst little on other fish pathogens such as Vibrio harvey and Photobacterium damselae. Further studies will elucidate the existence of other BD genes and their implications on the seabream defense against bacteria and virus.
authors.affiliation: Fish Innate Immune System Group, Department of Cell Biology and Histology, Faculty of Biology, University of Murcia, 30100 Murcia, Spain. alcuesta@um.es
authors.forename: Alberto
authors.initials: A
authors.lastname: Cuesta
authors.forename: José
authors.initials: J
authors.lastname: Meseguer
authors.forename: Maria Ángeles
authors.initials: MÁ
authors.lastname: Esteban
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000890:Anti-Infective Agents / Q000276:immunology / Q000378:metabolism*; D001412:Bacillus subtilis / Q000254:growth & development; D001483:Base Sequence; D002633:Chemotaxis; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D057809:HEK293 Cells; D006801:Humans; D007962:Leukocytes / Q000378:metabolism; D008969:Molecular Sequence Data; D010776:Photobacterium / Q000254:growth & development; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000378:metabolism; D021541:Sea Bream / Q000235:genetics* / Q000382:microbiology / Q000821:virology; D017422:Sequence Analysis, DNA; D014733:Vibrio / Q000254:growth & development; D023083:beta-Defensins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000890:Anti-Infective Agents; D029941:Fish Proteins; D011994:Recombinant Proteins; D023083:beta-Defensins