title: Human dendritic cells contain cell surface sialyltransferase activity.
abstract: Human monocyte-derived dendritic cells (mo-DCs) express highly sialylated structures, with recognized but poorly understood function in maturation, immunogenicity and endocytosis capacity. We have previously shown that mo-DCs surface sialylation is changeable upon different stimuli, which led us to hypothesise the existence of cell surface (non-intracellular) sialyltransferases, rapidly restoring or altering mo-DC surface sialylation, thus modulating specific functions. Here, we demonstrate that, in the presence of exogenous CMP-Neu5Ac, mo-DCs incorporate considerable amounts of sialic acids into cell surface, predominantly when mo-DCs were previously desialylated or matured. This is a genuine sialyltransferase activity, confirmed by specific inhibition assays, which is not influenced by secreted enzymes. Functionally, the ecto-sialyltransferase activity causes a significant down-regulation of mo-DCs endocytic capacity, without affecting the maturation state. These findings suggest that ecto-sialyltransferases participate in a dynamic control of mo-DC sialylation, with functional repercussions. This activity is possibly related with specific physiological and pathological conditions, as inflammation and infection, contributing to protection and homeostasis regulation.
authors.affiliation: CEDOC, Departamento de Imunologia, Faculdade de Ciências Médicas, FCM, Universidade Nova de Lisboa, Campo Mártires da Pátria 130, Lisbon, Portugal.
authors.forename: M Guadalupe
authors.initials: MG
authors.lastname: Cabral
authors.forename: A Rita
authors.initials: AR
authors.lastname: Piteira
authors.forename: Zélia
authors.initials: Z
authors.lastname: Silva
authors.forename: Dário
authors.initials: D
authors.lastname: Ligeiro
authors.forename: Reinhard
authors.initials: R
authors.lastname: Brossmer
authors.forename: Paula A
authors.initials: PA
authors.lastname: Videira
mesh_terms: D002462:Cell Membrane / Q000201:enzymology*; D003713:Dendritic Cells / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D004705:Endocytosis; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006801:Humans; D018613:Microscopy, Confocal; D009000:Monocytes / Q000166:cytology; D012794:Sialic Acids / Q000378:metabolism; D012799:Sialyltransferases / Q000235:genetics / Q000378:metabolism*
chemical_list: D012794:Sialic Acids; D012799:Sialyltransferases