摘要：Natural cytotoxicity receptor 2 (NCR2 or natural killer (NK)p44) and NCR3 (NKp30) bind to heparin and heparin sulfate; however, other natural ligands have yet to be identified. We previously reported that NCR1 (NKp46) can bind to multimeric NeuNAc-containing N -glycans and sulfated glycans. In this study, we investigated whether NKp44 and NKp30 can bind to NeuNAc-containing glycans using their common recombinant extracellular domain tagged with 6×His (NKp44-H6 and NKp30-H6). NKp44-H6, but not NKp30-H6, bound multimeric sialyl Lewis X expressing transferrin secreted by HepG2 cells (HepTF) with a K d of 420 n M . Competitive and direct binding assays revealed that NKp44-H6 mainly recognizes α2,3-NeuNAc residues on non-reducing ends of N -glycans on HepTF. Moreover, site-directed mutants of NKp44-H6, such as R47Q, R55Q, R92Q, R95Q, K103Q, and R106Q, had reduced binding to α2,3-sialylated N -glycans. These results suggest that NKp44 binds to α2,3-sialylated N -glycans through ionic interactions, and that these binding sites might have some overlap with heparin binding sites.
关键词：natural killer p44;natural killer p30;sialyl Lewis X;natural cytotoxicity receptor;mutagenesis
