Stimulation of the biosynthesis of lactosamine repeats in glycoproteins in differentiating U937 cells and its suppression in the presence of NH4Cl.
We prepared a mouse monoclonal antibody, 2D5, which recognized a highly glycosylated human lysosomal membrane antigen. The apparent molecular mass of this antigen was cell type dependent and ranged between 100 kDa and 130 kDa. The difference was due to a variation in the carbohydrate moiety, since upon removal of the N-linked oligosaccharides the size of the glycoprotein was reduced to approximately 50 kDa in all cases. The high carbohydrate contents, subcellular localization and N-terminal sequence indicated a high similarity or identity of this antigen with the lamp-2 protein. In U937 cells several agents known to elicit differentiation induced synthesis of a larger form of the lamp antigen. Thus, treatment of cells with calcitriol resulted in a shift in its average molecular mass from 115 kDa to 130 kDa. The difference was due to an increase in the contents of lactosamine repeats. In subcellular membranes from calcitriol-treated cells the specific activity of the UDP-N-acetylglucosamine: N-acetyllactosamine N-acetylglucosaminyltransferase was enhanced 3-fold. The enhancement was accompanied with an elongation of lactosamine repeats in N-linked oligosaccharides in the 46 kDa mannose 6-phosphate receptor and the homing receptor, the leucocyte antigen CD44. In contrast, the apparent size of the leucocyte antigen CD43 which bears numerous O-linked oligosaccharides was not changed indicating a selectivity in the modulation of the formation of lactosamine repeats in N- and O-linked carbohydrates. It is shown further that the synthesis of lactosamine repeats in U937 cells is impeded in the presence of NH4Cl.
Radons
J
J
Institut für Physiologische Chemie und Pathobiochemie der Universität, Münster/Germany.
Faber
V
V
Buhrmester
H
H
Völker
W
W
Horejsí
V
V
Hasilik
A
A
D000595:Amino Acid Sequence; D000606:Amino Sugars / Q000096:biosynthesis*; D000643:Ammonium Chloride / Q000494:pharmacology*; D000818:Animals; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D002117:Calcitriol / Q000494:pharmacology; D002454:Cell Differentiation / Q000502:physiology; D005964:Glucosyltransferases / Q000378:metabolism; D006801:Humans; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases; D012091:Repetitive Sequences, Nucleic Acid; D014407:Tumor Cells, Cultured
D000606:Amino Sugars; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D051907:Lysosomal Membrane Proteins; D008562:Membrane Glycoproteins; D000643:Ammonium Chloride; C032233:lactosamine; D005964:Glucosyltransferases; D017351:N-Acetylglucosaminyltransferases; C037649:N-acetyllactosaminide beta-1,6-N-acetylglucosaminyltransferase; D002117:Calcitriol