title: The Src tyrosine kinase Lck binds to CD2, CD4-1, and CD4-2 T cell co-receptors in channel catfish, Ictalurus punctatus.
abstract: The binding of the lymphocyte specific protein tyrosine kinase (Lck) to T cell co-receptors is required for T cell development and activation. In mammals, Lck initiates signal transduction by binding to CD4 and CD8 co-receptors and phosphorylating ITAMs in the cytoplasmic tail of the CD3 molecules and the ζ chains. In addition, Lck can also bind to the adhesion molecule CD2 and trigger T cell activation. In this study, Lck and CD2 homologs were identified and characterized in channel catfish, Ictalurus punctatus. Lck and CD2 mRNAs were specifically expressed by clonal T cell lines, including both CD4(+) and CD4(-)CD8(-) CTL lines, and in mixed lymphocyte cultures (MLC). Western blot analyses using anti-trout Lck and anti-human p-Lck antibodies demonstrated that Lck protein is expressed in catfish clonal CTL and is phosphorylated at a conserved tyrosine residue. Because of the lack of CD8(+) CTL lines as well as the absence of CD8 message in MLC, we performed magnetic bead binding assays to correlate CD2, CD4, and CD8 co-receptor expression with Lck binding ability. Recombinant Lck reproducibly bound to CD2, CD4-1, and CD4-2, but not to CD8α or CD8β. These data provide one possible explanation for the apparent low numbers of CD8(+) CTL and the presence of CD4(+) and CD4(-)CD8(-)CD2(+) CTL in catfish.
authors.affiliation: Department of Microbiology, University of Mississippi Medical Center, Jackson, MS 39216, United States.
authors.forename: Erin B
authors.initials: EB
authors.lastname: Taylor
authors.affiliation: Department of Microbiology, University of Mississippi Medical Center, Jackson, MS 39216, United States.
authors.forename: Melanie
authors.initials: M
authors.lastname: Wilson
authors.affiliation: Department of Microbiology, University of Mississippi Medical Center, Jackson, MS 39216, United States. Electronic address: ebengten@umc.edu.
authors.forename: Eva
authors.initials: E
authors.lastname: Bengten
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018801:CD2 Antigens / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015704:CD4 Antigens / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D016827:CD8 Antigens / Q000235:genetics / Q000276:immunology; D002999:Clone Cells; D029941:Fish Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007059:Ictaluridae / Q000145:classification / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010802:Phylogeny; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology / Q000276:immunology*; D014337:Trout / Q000276:immunology
chemical_list: D018801:CD2 Antigens; D015704:CD4 Antigens; D016827:CD8 Antigens; D029941:Fish Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
keywords: CD2; Catfish; Co-receptors; Lck; T cell signaling; T lymphocytes