title: Asynchronous transport to the cell surface of intestinal brush border hydrolases is not due to differential trimming of N-linked oligosaccharides.
abstract: Intestinal brush border enzyme glycoproteins are transported to the microvillar membrane at different rates in the differentiated intestinal cell line Caco-2. This asynchronism is due to at least two rate-limiting events, a pre- and an intra-Golgi step (Stieger B., Matter, K., Baur, B., Bucher, K., Höchli, M., and Hauri, H.P. (1988) J. Cell Biol. 106, 1853-1861). A possible cause for the asynchronous protein transport might be differential trimming of N-linked oligosaccharide side chains. The effects of two trimming inhibitors on the intracellular transport of sucrase-isomaltase, a slowly migrating hydrolase, and dipeptidylpeptidase IV, a rapidly migrating hydrolase, are described. 1-Deoxymannojirimycin, an inhibitor of Golgi alpha-mannosidase I, had no influence on the rate of appearance of these hydrolases in the brush border membrane as assessed by subcellular fractionation. In the presence of N-methyl-1-deoxynojirimycin, an inhibitor of glucosidase I, 30-40% of the newly synthesized molecules appeared at the cell surface, and half-time for appearance of this pool was identical to that found in control cells. The reduced maximal transport to the cell surface observed with N-methyl-1-deoxynojirimycin may suggest that proper glycosylation is necessary for an efficient transport from the Golgi apparatus to the microvillar membrane. Inhibition of glucosidase I does not prevent the acquisition of endoglycosidase H resistance. Furthermore, evidence is presented that the processing in the presence of N-methyl-1-deoxynojirimycin leads to glycosylated endoglycosidase H-resistant glycoproteins.
authors.affiliation: Department of Pharmacology, University of Basel, Switzerland.
authors.forename: K
authors.initials: K
authors.lastname: Matter
authors.forename: W
authors.initials: W
authors.lastname: McDowell
authors.forename: R T
authors.initials: RT
authors.lastname: Schwartz
authors.forename: H P
authors.initials: HP
authors.lastname: Hauri
mesh_terms: D017485:1-Deoxynojirimycin / Q000031:analogs & derivatives; D000118:Acetylglucosaminidase / Q000096:biosynthesis; D001692:Biological Transport / Q000187:drug effects; D003208:Concanavalin A / Q000378:metabolism; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000096:biosynthesis / Q000378:metabolism; D005944:Glucosamine / Q000031:analogs & derivatives / Q000494:pharmacology; D065089:Glycoside Hydrolase Inhibitors; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D006867:Hydrolases / Q000378:metabolism*; D007421:Intestine, Small / Q000187:drug effects / Q000201:enzymology*; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008871:Microvilli / Q000187:drug effects / Q000201:enzymology; D009844:Oligosaccharides / Q000378:metabolism*; D013393:Sucrase / Q000037:antagonists & inhibitors; D013394:Sucrase-Isomaltase Complex / Q000096:biosynthesis / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000201:enzymology; D000520:alpha-Glucosidases
chemical_list: D065089:Glycoside Hydrolase Inhibitors; D009844:Oligosaccharides; D003208:Concanavalin A; D017485:1-Deoxynojirimycin; D006867:Hydrolases; D013394:Sucrase-Isomaltase Complex; C042059:glucosidase I; D000520:alpha-Glucosidases; D013393:Sucrase; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D005944:Glucosamine; C033424:N-methyldeoxynojirimycin