title: Siglec-9, a novel sialic acid binding member of the immunoglobulin superfamily expressed broadly on human blood leukocytes.
abstract: Here we characterize the properties and expression pattern of Siglec-9 (sialic acid-binding Ig-like lectin-9), a new member of the Siglec subgroup of the immunoglobulin superfamily. A full-length cDNA encoding Siglec-9 was isolated from a dibutyryl cAMP-treated HL-60 cell cDNA library. Siglec-9 is predicted to contain three extracellular immunoglobulin-like domains that comprise an N-terminal V-set domain and two C2-set domains, a transmembrane region and a cytoplasmic tail containing two putative tyrosine-based signaling motifs. Overall, Siglec-9 is approximately 80% identical in amino acid sequence to Siglec-7, suggesting that the genes encoding these two proteins arose relatively recently by gene duplication. Binding assays showed that, similar to Siglec-7, Siglec-9 recognized sialic acid in either the alpha2,3- or alpha2, 6-glycosidic linkage to galactose. Using a specific mAb, Siglec-9 was found to be expressed at high or intermediate levels by monocytes, neutrophils, and a minor population of CD16(+), CD56(-) cells. Weaker expression was observed on approximately 50% of B cells and NK cells and minor subsets of CD8(+) T cells and CD4(+) T cells. These results show that despite their high degree of sequence similarity, Siglec-7 and Siglec-9 have distinct expression profiles.
authors.affiliation: Wellcome Trust Biocentre, Department of Biochemistry, University of Dundee, Dundee DD1 5EH, Scotland, United Kingdom.
authors.forename: J Q
authors.initials: JQ
authors.lastname: Zhang
authors.forename: G
authors.initials: G
authors.lastname: Nicoll
authors.forename: C
authors.initials: C
authors.lastname: Jones
authors.forename: P R
authors.initials: PR
authors.lastname: Crocker
mesh_terms: D000595:Amino Acid Sequence; D015703:Antigens, CD / Q000235:genetics* / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D007136:Immunoglobulins / Q000235:genetics* / Q000378:metabolism*; D037102:Lectins / Q000235:genetics* / Q000378:metabolism*; D007962:Leukocytes / Q000378:metabolism*; D008969:Molecular Sequence Data; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D016415:Sequence Alignment; D063265:Sialic Acid Binding Immunoglobulin-like Lectins
chemical_list: D015703:Antigens, CD; D018076:DNA, Complementary; D007136:Immunoglobulins; D037102:Lectins; C412227:SIGLEC9 protein, human; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; D019158:N-Acetylneuraminic Acid