title: Molecular insights into a molluscan transferrin homolog identified from disk abalone (Haliotis discus discus) evidencing its detectable role in host antibacterial defense.
abstract: The basic function of transferrin is to bind iron (III) ions in the medium and to deliver them to the locations where they are required for metabolic processes. It also takes part in the host immune defense mainly via its ability to bind to iron (III) ions. Hence, transferrin is also identified as an important acute-phase protein in host immunity. Abalones are major shellfish aquaculture crops that are susceptible to a range of marine microbial infections. Since transferrin is known to be a major player in innate immunity, in the present study we sought to identify, and molecularly and functionally characterize a transferrin-like gene from disk abalone (Haliotis discus discus) named as AbTrf. AbTrf consisted of a 2187-bp open reading frame (ORF) which encodes a 728 amino acid (aa) protein. The putative amino acid sequence of AbTrf harbored N- and C-terminal transferrin-like domains, active sites for iron binding, and conserved cysteine residues. A constitutive tissue specific AbTrf expression pattern was detected by qPCR in abalones where mantle and muscle showed high AbTrf expression levels. Three immune challenge experiments were conducted using Vibrio parahaemolyticus, Listeria monocytogenes and LPS as stimuli and, subsequently, AbTrf mRNA expression levels were quantified in gill and hemocytes in a time-course manner. The mRNA expression was greatly induced in both tissues in response to both challenges. Evidencing the functional property of transferrins, recombinant AbTrf N-terminal domain (AbTrf-N) showed dose-dependent iron (III) binding activity detected by chrome azurol S (CAS) assay system. Moreover, recombinant AbTrf-N could significantly inhibit the growth of iron-dependent bacterium, Escherichia coli in a dose-dependent manner. However, AbTrf-N was unable to show any detectable bacteriostatic activity against iron-independent bacterium Lactobacillus plantarum (L. plantarum) even at its highest concentration. Collectively, our results suggest that AbTrf might play a significant role in the host innate immunity, possibly by withholding iron from pathogens.
authors.affiliation: Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea.
authors.forename: H M L P B
authors.initials: HM
authors.lastname: Herath
authors.affiliation: Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea.
authors.forename: Don Anushka Sandaruwan
authors.initials: DA
authors.lastname: Elvitigala
authors.affiliation: Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea.
authors.forename: G I
authors.initials: GI
authors.lastname: Godahewa
authors.affiliation: Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea.
authors.forename: Ilson
authors.initials: I
authors.lastname: Whang
authors.affiliation: Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea. Electronic address: jehee@jejunu.ac.kr.
authors.forename: Jehee
authors.initials: J
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000254:growth & development; D049851:Gastropoda / Q000276:immunology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D005880:Gills / Q000276:immunology; D006434:Hemocytes / Q000276:immunology; D007113:Immunity, Innate / Q000276:immunology*; D007501:Iron / Q000378:metabolism*; D048191:Lactiplantibacillus plantarum / Q000254:growth & development; D008070:Lipopolysaccharides / Q000276:immunology; D008089:Listeria monocytogenes / Q000276:immunology; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D014168:Transferrin / Q000031:analogs & derivatives / Q000235:genetics* / Q000276:immunology*; D014736:Vibrio parahaemolyticus / Q000276:immunology
chemical_list: D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014168:Transferrin; D007501:Iron
keywords: Abalone; Antibacterial activity; Iron binding; Transcriptional analysis; Transferrin