Differential effects of brefeldin A on sialylation of N- and O-linked oligosaccharides in low density lipoprotein receptor and epidermal growth factor receptor.
Low density lipoprotein receptor (LDL-R) is a membrane glycoprotein carrying both N- and O-linked oligosaccharides, processing of which is reflected in conversion from a precursor to mature form during its synthesis and intracellular transport. Treatment with brefeldin A (BFA) of mouse macrophage-like J774 cells, Chinese hamster ovary cells, and two human cancer cell lines (A431 and IMC-2) resulted in production of LDL-R with a molecular size 5-10 kDa smaller than that of the mature form in the control cells. Treatment with sialidase caused apparent reduction in the molecular size of LDL-R synthesized in all BFA-treated J774, Chinese hamster ovary, A431, and IMC-2 cell lines as observed for the mature form of the control cells. Thus, O-linked sugar chains of LDL-R were apparently sialylated in the BFA-treated cells. We also examined the effect of BFA on the processing of another membranous glycoprotein, epidermal growth factor receptor (EGF-R) carrying only N-linked oligosaccharides. EGF-R synthesized in the presence of BFA was found to have no response to sialidase treatment, suggesting that the drug blocks the sialylation of EGF-R. The results indicate that BFA causes different effects on the sialylation of LDL-R and EGF-R depending upon linkage types of their oligosaccharides.
Department of Biochemistry, Oita Medical School, Japan.
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S
Shite
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Seguchi
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Mizoguchi
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Ono
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M
Kuwano
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D020126:Brefeldin A; D002460:Cell Line; D003517:Cyclopentanes / Q000494:pharmacology*; D066246:ErbB Receptors / Q000096:biosynthesis* / Q000187:drug effects / Q000302:isolation & purification; D006801:Humans; D007700:Kinetics; D009844:Oligosaccharides / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D011973:Receptors, LDL / Q000096:biosynthesis* / Q000187:drug effects / Q000302:isolation & purification; D012799:Sialyltransferases / Q000378:metabolism*; D014415:Tunicamycin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D003517:Cyclopentanes; D009844:Oligosaccharides; D011973:Receptors, LDL; D014415:Tunicamycin; D020126:Brefeldin A; D012799:Sialyltransferases; D066246:ErbB Receptors