Purification of two glycoproteins expressing beta 1-6 branched Asn-linked oligosaccharides from metastatic tumour cells.
Increased branching at the trimannosyl core of 'complex-type' Asn-linked oligosaccharides has been observed in both human and murine tumour cells, and appears to be associated with enhanced metastatic potential in several murine tumour models [Dennis, Laferte, Waghorne, Breitman & Kerbel (1987), Science 236, 582-585]. The lectin leucoagglutinin (L-PHA) requires the-GlcNAc beta 1-6Man alpha 1-6Man-linked lactosamine antenna in complex-type oligosaccharides for high-affinity binding and can be used to detect these structures in glycoproteins separated on SDS/polyacrylamide-gel electrophoresis. The major L-PHA-binding glycoproteins in the highly metastatic lymphoid tumour cell line called MDAY-D2 were purified and resolved into two major species, termed P2A (110 kDa) and P2B (130 kDa). P2A had L-PHA-reactive Asn-linked oligosaccharides with polylactosamine sequences as well as a large component of sialylated O-linked carbohydrates. The glycoprotein showed structural characteristics similar to those of leukosialin (i.e. CD43), a glycoprotein previously identified on the surface of leukocytes. Based on monosaccharide compositional analysis and glycosidase digestions, P2B was found to be 50-60% Asn-linked oligosaccharide containing polylactosamine sequences and sialic acid. The N-terminal peptide sequence of P2B was determined to be very similar to that of murine lysosomal membrane glycoprotein (LAMP-1), a ubiquitous glycoprotein found largely in the lysosomal membranes but also in the plasma membrane of several murine and human tumour cell lines.
Laferte
S
S
Department of Biochemistry, University of Saskatchewan, Saskatoon, Canada.
Dennis
J W
JW
D000595:Amino Acid Sequence; D000818:Animals; D006023:Glycoproteins / Q000302:isolation & purification*; D008223:Lymphoma / Q000032:analysis / Q000556:secondary*; D051379:Mice; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000302:isolation & purification*; D014407:Tumor Cells, Cultured / Q000032:analysis
D006023:Glycoproteins; D009844:Oligosaccharides