Covalent oligomerization of rat gastric mucin occurs in the rough endoplasmic reticulum, is N-glycosylation-dependent, and precedes initial O-glycosylation.
Rat gastric mucin undergoes extensive modifications during biosynthesis, including oligomerization, N- and O-glycosylation, and sulfation. We characterized the events in the rough endoplasmic reticulum (RER) and Golgi complex and studied how these steps are interrelated, using specific inhibitors of cellular processes. The mucin precursors oligomerize in the RER by forming intermolecular disulfide bonds. The oligomers comprise a mixture of predominantly di- and trimers of molar ratio 3:2. The oligomerized precursors are transported to the Golgi complex to form mature, oligomeric mucin by extensive O-glycosylation, and sulfation. N-Glycosylation of the precursor is required for efficient oligomerization. Brefeldin A, which inhibits protein transport between RER and Golgi complex, allows oligomerization and concomitantly induces initial O-glycosylation. Oligomerization and egrees from the RER precedes initial O-glycosylation and are therefore independent of the latter process.
Department of Cell Biology, State University of Utrecht, School of Medicine, The Netherlands.
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Dekker
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Strous
D000818:Animals; D001692:Biological Transport; D020126:Brefeldin A; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D003517:Cyclopentanes / Q000494:pharmacology; D004220:Disulfides; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005753:Gastric Mucosa / Q000378:metabolism*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008970:Molecular Weight; D008985:Monensin / Q000494:pharmacology; D009077:Mucins / Q000096:biosynthesis*; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D051381:Rats; D013329:Structure-Activity Relationship; D013431:Sulfates / Q000378:metabolism; D013696:Temperature
D003517:Cyclopentanes; D004220:Disulfides; D046911:Macromolecular Substances; D009077:Mucins; D011498:Protein Precursors; D013431:Sulfates; D020126:Brefeldin A; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D008985:Monensin