title: Maturation of human lactase-phlorizin hydrolase. Proteolytic cleavage of precursor occurs after passage through the Golgi complex.
abstract: Maturation of human intestinal lactase-phlorizin hydrolase (LPH) requires that a precursor (pro-LPH) be proteolytically processed to the mature microvillus membrane enzyme (m-LPH). The subcellular site of this processing is unknown. Using low-temperature experiments and brefeldin A (BFA), intracellular transport was blocked in intestinal epithelial cells. In Caco-2 cells incubated at 18 degrees C, pro-LPH was complex-glycosylated but not cleaved, while at 20 degrees C small amounts of proteolytically processed LPH were observed. These data exclude a pre-Golgi proteolytic event. BFA completely blocked proteolytic maturation of LPH and lead to an aberrant form of pro-LPH in both Caco-2 cells and intestinal explants. Therefore, proteolytic processing of LPH is a post-Golgi event, occurring either in the trans-Golgi network, transport vesicles, or after insertion of pro-LPH into the microvillus membrane.
authors.affiliation: Institute of Biochemistry and Molecular Biology, Faculty of Medicine, University of Berne, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: Lottaz
authors.forename: T
authors.initials: T
authors.lastname: Oberholzer
authors.forename: P
authors.initials: P
authors.lastname: Bähler
authors.forename: G
authors.initials: G
authors.lastname: Semenza
authors.forename: E E
authors.initials: EE
authors.lastname: Sterchi
mesh_terms: D020126:Brefeldin A; D002478:Cells, Cultured; D003517:Cyclopentanes / Q000494:pharmacology; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000201:enzymology; D043322:Lactase; D010694:Lactase-Phlorizin Hydrolase / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008871:Microvilli / Q000201:enzymology; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D013696:Temperature; D000515:alpha 1-Antitrypsin / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism*
chemical_list: D003517:Cyclopentanes; D008562:Membrane Glycoproteins; D009097:Multienzyme Complexes; D011498:Protein Precursors; D000515:alpha 1-Antitrypsin; D020126:Brefeldin A; D043322:Lactase; D001616:beta-Galactosidase; D010694:Lactase-Phlorizin Hydrolase