Human dendritic cells contain cell surface sialyltransferase activity.
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.
Cabral
M Guadalupe
MG
CEDOC, Departamento de Imunologia, Faculdade de Ciências Médicas, FCM, Universidade Nova de Lisboa, Campo Mártires da Pátria 130, Lisbon, Portugal.
Piteira
A Rita
AR
Silva
Zélia
Z
Ligeiro
Dário
D
Brossmer
Reinhard
R
Videira
Paula A
PA
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*
D012794:Sialic Acids; D012799:Sialyltransferases