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Expression of N-acetylglucosamine 6-O-sulfotransferases (GlcNAc6STs)-1 and -4 in human monocytes: GlcNAc6ST-1 is implicated in the generation of the 6-sulfo N-acetyllactosamine/Lewis x epitope on CD44 and is induced by TNF-alpha.
Sulfation at the 6-O position of N-acetylglucosamine (GlcNAc) in the context of sialyl 6-sulfo Lewis x occurs constitutively on specific glycoproteins present on high-walled endothelial venules (HEV) and is important for L-selectin dependent homing of lymphocytes. Here, the proinflammatory cytokine, TNF-alpha, induced the expression of 6-sulfo N-acetyllactosamine (LacNAc)/Lewis x on human peripheral blood monocytes (PBM). This epitope was detected by monoclonal antibody (mAb) AG107 after neuraminidase treatment suggesting a sialylated epitope, which was present on the cell adhesion molecule, CD44. Treatment of human PBM with TNF-alpha up-regulated the expression of N-acetylglucosamine 6-O-sulfotransferase-1 (GlcNAc6ST-1) and GlcNAc6ST-4, as determined by reverse transcriptase polymerase chain reaction (RT-PCR). However, only GlcNAc6ST-1 was induced by TNF-alpha in the human SR91 cell line, which also up-regulated the AG107 epitope. In ECV304 cells, the expression of GlcNAc6ST-4 alone was insufficient to generate the AG107 epitope. However, the transfection of GlcNAc6ST-1 resulted in significant sulfate incorporation into CD44 and generated the 6-sulfo LacNAc/Lewis x epitope on CD44, which was present largely on N-linked glycans. This demonstrates the induction of GlcNAc6STs in human monocytes in response to TNF-alpha and implicates GlcNAc6ST-1 in the generation of the 6-sulfo LacNAc/Lewis x epitope on CD44.
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