A family of novel, acidic N-glycans in Bowes melanoma tissue plasminogen activator have L2/HNK-1-bearing antennae, many with sulfation of the fucosylated chitobiose core.
A family of about 20 novel acidic bi- and tri-antennary N-glycans, amounting to almost half those expressed on Bowes melanoma tissue-plasminogen activator (t-PA) were found to possess Galbeta1-->4GlcNAcbeta1-->, sulfated and sialylated GalNAcbeta1-->4GlcNAcbeta1--> or sulfated GlcAbeta1--> 3Galbeta1-->4GlcNAcbeta1--> antennae, of which those containing sulfated GlcA, depicting the L2/HNK-1 carbohydrate epitope, were preferentially located on the 6 arm. A proportion of the glycans were highly charged, because of multiple and variously distributed sulfation, some of which was located on the fucosylated chitobiose core. Multiple expression of the L2/HNK-1 epitope on a single glycan was observed. The most abundant compound was a biantennary glycan carrying sulfated GlcA on the 6-branched antenna and an alpha2-->6 sialylated GalNAc on the other. The N-glycosylation sequon containing Asn448, which is known to express all of the sulfate-carrying N-glycans contains, unusually, an arginine residue. An electrostatic interaction between this cationic amino acid and the core-sulfate group of the N-glycan is proposed to reduce mobility of the carbohydrate in the region of the t-PA active site. Because of the 'brain-type' nature of the N-glycans described in this neuro-ectodermal cell line, the possibility of neural t-PA interacting with the L2/HNK-1-recognizing molecule, laminin, of the central nervous system extracellular matrix is discussed.
Zamze
S
S
Oxford Glycobiology Institute, Department of Biochemistry, South Parks Road, Oxford, UK.
Wing
D R
DR
Wormald
M R
MR
Hunter
A P
AP
Dwek
R A
RA
Harvey
D J
DJ
D015295:Antigens, Tumor-Associated, Carbohydrate / Q000737:chemistry*; D018959:CD57 Antigens / Q000737:chemistry*; D002240:Carbohydrate Sequence; D004187:Disaccharides; D000939:Epitopes / Q000737:chemistry; D005643:Fucose; D006801:Humans; D008545:Melanoma / Q000737:chemistry* / Q000276:immunology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009417:Nerve Tissue / Q000254:growth & development; D013463:Sulfuric Acid Esters; D010959:Tissue Plasminogen Activator / Q000737:chemistry* / Q000276:immunology
D015295:Antigens, Tumor-Associated, Carbohydrate; D018959:CD57 Antigens; D004187:Disaccharides; D000939:Epitopes; D013463:Sulfuric Acid Esters; D005643:Fucose; C032438:chitobiose; D010959:Tissue Plasminogen Activator