Identification of a chicken CLEC-2 homologue, an activating C-type lectin expressed by thrombocytes.
Receptors on natural killer (NK) cells are classified as C-type lectins or as Ig-like molecules, and many of them are encoded by two genomic clusters designated natural killer gene complex (NKC) and leukocyte receptor complex, respectively. Here, we describe the analysis of an NKC-encoded chicken C-type lectin, previously annotated as homologue to CD94 and NKG2 and thus designated chicken CD94/NKG2. To further elucidate its potential function on NK cells, we produced a specific mab by immunizing with stably transfected HEK293 cells expressing this lectin. Staining of various chicken tissues revealed minimal reactivity with bursal, or thymus cells. In peripheral blood mononuclear cell and spleen, however, the mab reacted with virtually all thrombocytes, whereas most NK cells in organs such as embryonic spleen, lung and intestine were found to be negative. These findings indicate that the gene may not resemble CD94/NKG2, but rather a CLEC-2 homologue, a claim further supported by sequence features such as an additional extracellular cysteine residue and the presence of a cytoplasmic motif known as a hem immunoreceptor tyrosine-based activation motif, found in C-type lectins such as Dectin-1, CLEC-2, but not CD94/NKG2. The biochemical analyses demonstrated that CLEC-2 is present on the cell surface as heavily glycosylated homodimer, which upon mab crosslinking induced thrombocyte activation, as measured by CD107 expression. These analyses reveal that the chicken NKC may not encode NK cell receptor genes, in particular not CD94 or NKG2 genes, and identifies a chicken CLEC-2 homologue.
Institute for Animal Physiology, Department of Veterinary Sciences, University of Munich, Veterinärstr. 13, 80539, Munich, Germany.
Marie-Luise
ML
Neulen
Thomas W
TW
Göbel
D000595:Amino Acid Sequence; D000818:Animals; D058846:Antibodies, Monoclonal, Murine-Derived / Q000276:immunology; D001483:Base Sequence; D001792:Blood Platelets / Q000276:immunology*; D002645:Chickens / Q000235:genetics* / Q000276:immunology*; D017931:DNA Primers / Q000235:genetics; D019281:Dimerization; D006031:Glycosylation; D057809:HEK293 Cells; D006801:Humans; D055261:Immunogenetic Phenomena; D007694:Killer Cells, Natural / Q000276:immunology; D037181:Lectins, C-Type / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D015539:Platelet Activation / Q000235:genetics / Q000276:immunology; D010974:Platelet Aggregation / Q000235:genetics / Q000276:immunology; D055607:Receptors, Natural Killer Cell / Q000235:genetics / Q000276:immunology; D017386:Sequence Homology, Amino Acid
D058846:Antibodies, Monoclonal, Murine-Derived; D017931:DNA Primers; D037181:Lectins, C-Type; D055607:Receptors, Natural Killer Cell