Long-term effect of cyclic AMP on N-glycosylation is caused by an increase in the activity of the cis-prenyltransferase.
Previously we have shown that long-term pretreatment of JEG-3 choriocarcinoma cells with 8-bromo-cAMP increases the capacity for N-glycosylation that was caused by an 8-10-fold enlargement of the dolichol pyrophosphoryl oligosaccharide (Dol-PP-oligosaccharide) pool [Konrad and Merz (1994) J. Biol. Chem. 269, 8659-8666]. The factors involved in the effect of cAMP on synthesis of Dol-PP-oligosaccharide are investigated here. The GlcNAc transfer to dolichol phosphate (Dol-P) was found to be unaffected by pretreatment with 8-bromo-cAMP. By measuring the uptake of [3H]mevalonate, a 20-fold increase in the incorporation of the label into Dol-P was observed in the cells treated with 8-bromo-cAMP. Under the same conditions, the synthesis of dolichol was enhanced 60-fold. However, the incorporation of the radioactivity into cholesterol was not increased in the JEG-3 cells pretreated with 8-bromo-cAMP, which suggests a specific stimulation of the dolichol/Dol-P pathway by cAMP. The cis-prenyltransferase activity was found to be increased 10-fold in cells pretreated with 8-bromo-cAMP. Dolichol kinase activity was unaffected by stimulation with 8-bromo-cAMP. The present study suggests that the larger glycosylation capacity in JEG-3 cells treated with 8-bromo-cAMP is caused by an increase in the microsomal cis-prenyltransferase activity.
Konrad
M
M
Department of Biochemistry II, University of Heidelberg, Federal Republic of Germany.
Merz
W E
WE
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D002499:Centrifugation, Density Gradient; D002784:Cholesterol / Q000096:biosynthesis; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D004122:Dimethylallyltranstransferase / Q000378:metabolism*; D004288:Dolichol Phosphates / Q000096:biosynthesis; D004286:Dolichols / Q000096:biosynthesis; D006031:Glycosylation / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D008358:Mannose / Q000378:metabolism; D008798:Mevalonic Acid / Q000378:metabolism; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011103:Polyisoprenyl Phosphate Monosaccharides / Q000378:metabolism; D011104:Polyisoprenyl Phosphate Oligosaccharides / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
D004288:Dolichol Phosphates; D004286:Dolichols; D011103:Polyisoprenyl Phosphate Monosaccharides; D011104:Polyisoprenyl Phosphate Oligosaccharides; C024962:dolichyl diphosphate oligosaccharides; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; C018439:N-acetylglucosaminylpyrophosphoryldolichol; D002784:Cholesterol; D000242:Cyclic AMP; D017351:N-Acetylglucosaminyltransferases; C035783:UDP-N-acetylglucosamine-dolichyldiphosphate N-acetylglucosamine, N-acetylglucosamine transferase; D004122:Dimethylallyltranstransferase; D017853:Phosphotransferases (Alcohol Group Acceptor); C020087:dolichol kinase; D008358:Mannose; D008798:Mevalonic Acid