Sialic Acid Binding Ig Like Lectin 9 (SIGLEC9)

SIGLEC9 has 8 potential N-linked glycosylation sites and a cytoplasmic tail with 94 residues. Unlike SIGLEC7, COS cells expressing SIGLEC9 required sialidase treatment before binding to red cells, which must not be treated with the enzyme. Northern blot analysis detected clear expression in spleen and placenta, with low or undetectable expression in liver, colon, stomach, and testis. Flow cytometric analysis demonstrated expression on monocytes and neutrophils, as well as on a subpopulation of lymphocytes, but not on eosinophils.SIGLEC9 binding to erythrocytes could be abolished by sialidase treatment of the red cells. SIGLEC9 was found to bind to both alpha-2-3- and alpha-2-6-linked sialic acids. Unlike other Ig-like genes, no SIGLEC homologs were identified in the C. elegans and fruit fly databases.