Binding of sialyl Lewis X antigen to lectin-like receptors on NK cells induces cytotoxicity and tyrosine phosphorylation of a 17-kDa protein

Abstract

Background: Natural killer (NK) cells mediate cytotoxicity through cell-surface receptors including lectin-like receptors. We have investigated whether sialyl Lewis X (sLe X) antigen, Neu5Acα2,3Galβ1,4(Fucα1,3) GlcNAc-R, can bind to the lectin-like receptors on human NK-derived KHYG cells, using transferrin secreted by human hepatoma-derived HepG2 cells (Hep-TF), whose N-glycans are rich in α1,3-fucosylated bi-, tri-, and tetra-antennary type complexes, and commercially available human transferrin (Nor-TF), which is comprised of bi-antennary N-glycans without α1,3-fucosylation. Results: High sLeX-expressing erythroleukemia-derived K562 cells isolated from fucosyltransferase-3-transfected cells were 2.5-fold more susceptible than wild-type K562 cells to KHYG cells. Fluorescein isothiocyanate (FITC)-labeled Hep-TF bound 1.8-fold more strongly to KHYG cells than did FITC-labeled Nor-TF; the binding was suppressed by treatment with anti-NKG2D, anti-NKG2C, anti-CD94 and anti-CD161 antibodies. FITC-labeled Hep-TF bound more strongly to human monocyte-derived U937 cells transfected with NKG2D and CD94 than to wild-type U937 cells. Moreover, tyrosine phosphorylation of a 17-kDa protein in the KHYG cells was enhanced by incubation on a Hep-TF coated plate and treatment with an anti-NKG2D antibody, but not by a Nor-TF coated plate and an anti-CD94 antibody. Conclusion: The interaction of sLe X antigen with lectin-like receptors on NK cells induces cytotoxicity that is mediated through a tyrosine-phosphorylated 17-kDa protein.