Biosynthesis of L-selectin ligands: sulfation of sialyl Lewis x-related oligosaccharides by a family of GlcNAc-6-sulfotransferases.
The leukocyte adhesion molecule L-selectin mediates lymphocyte homing to secondary lymphoid organs and to certain sites of inflammation. The cognate ligands for L-selectin possess the unusual sulfated tetrasaccharide epitope 6-sulfo sialyl Lewis x (Siaalpha2-->3Galbeta1-->4[Fucalpha1-->3][SO(3)-->6]GlcNAc). Sulfation of GlcNAc within sialyl Lewis x is a crucial modification for L-selectin binding, and thus, the underlying sulfotransferase may be a key modulator of lymphocyte trafficking. Four recently discovered GlcNAc-6-sulfotransferases are the first candidate contributors to the biosynthesis of 6-sulfo sLex in the context of L-selectin ligands. Here we report the in vitro activity of the four GlcNAc-6-sulfotransferases on a panel of synthetic oligosaccharide substrates that comprise structural motifs derived from sialyl Lewis x. Each enzyme preferred a terminal GlcNAc residue, and was impeded by the addition of a beta1,4-linked Gal residue (i.e., terminal LacNAc). Surprisingly, for three of the enzymes, significant activity was observed with sialylated LacNAc, and two of the enzymes were capable of detectable sulfation of GlcNAc in the context of sialyl Lewis x. On the basis of these results, we propose possible pathways for 6-sulfo sialyl Lewis x biosynthesis and suggest that sulfation may be an early committed step.
Bowman
K G
KG
Departments of Chemistry and Molecular and Cell Biology and Howard Hughes Medical Institute, University of California, Berkeley 94720, USA.
Cook
B N
BN
de Graffenried
C L
CL
Bertozzi
C R
CR
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002240:Carbohydrate Sequence; D005822:Genetic Vectors / Q000138:chemical synthesis; D006801:Humans; D019041:L-Selectin / Q000378:metabolism*; D007983:Lewis Blood Group Antigens / Q000096:biosynthesis / Q000378:metabolism; D016256:Lewis X Antigen / Q000096:biosynthesis / Q000378:metabolism; D008024:Ligands; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017386:Sequence Homology, Amino Acid; D000080506:Sialyl Lewis X Antigen; D013379:Substrate Specificity / Q000235:genetics; D015238:Sulfotransferases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D000097811:Carbohydrate Sulfotransferases
D019041:L-Selectin; D007983:Lewis Blood Group Antigens; D016256:Lewis X Antigen; D008024:Ligands; D009844:Oligosaccharides; D000080506:Sialyl Lewis X Antigen; D015238:Sulfotransferases; D000097811:Carbohydrate Sulfotransferases