Control of bisecting GlcNAc addition to N-linked sugar chains.
In the present study, experimental control of the formation of bisecting GlcNAc was investigated, and the competition between beta-1,4-GalT (UDP-galactose:N-acetylglucosamine beta-1, 4-galactosyltransferase) and GnT-III (UDP-N-acetylglucosamine:beta-d-mannoside beta-1, 4-N-acetylglucosaminyltransferase) was examined. We isolated a beta-1,4-GalT-I single knockout human B cell clone producing monoclonal IgM and several transfectant clones that overexpressed beta-1,4-GalT-I or GnT-III. In the beta-1,4-GalT-I-single knockout cells, the extent of bisecting GlcNAc addition to the sugar chains of IgM was increased, where beta-1,4-GalT activity was reduced to about half that in the parental cells, and GnT-III activity was unaltered. In the beta-1,4-GalT-I transfectants, the extent of bisecting GlcNAc addition was reduced although GnT-III activity was not altered significantly. In the GnT-III transfectants, the extent of bisecting GlcNAc addition increased along with the increase in levels of GnT-III activity. The extent of bisecting GlcNAc addition to the sugar chains of IgM was significantly correlated with the level of intracellular beta-1,4-GalT activity relative to that of GnT-III. These results were interpreted as indicating that beta-1, 4-GalT competes with GnT-III for substrate in the cells.
Fukuta
K
K
Life Science Laboratory, Mitsui Chemicals, Inc., 1144 Togo, Mobara, Chiba 297-0017, Japan.
Abe
R
R
Yokomatsu
T
T
Omae
F
F
Asanagi
M
M
Makino
T
T
D000117:Acetylglucosamine / Q000378:metabolism*; D000911:Antibodies, Monoclonal / Q000096:biosynthesis; D001402:B-Lymphocytes / Q000378:metabolism*; D002240:Carbohydrate Sequence; D002999:Clone Cells; D006031:Glycosylation; D006801:Humans; D007075:Immunoglobulin M / Q000096:biosynthesis* / Q000737:chemistry*; D008969:Molecular Sequence Data; D009154:Mutation; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism*; D009237:N-Acetyllactosamine Synthase / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D014162:Transfection
D000911:Antibodies, Monoclonal; D007075:Immunoglobulin M; D017351:N-Acetylglucosaminyltransferases; C054599:beta-1,4-mannosyl-glycoprotein beta-1,4-N-acetylglucosaminyltransferase; D009237:N-Acetyllactosamine Synthase; D000117:Acetylglucosamine