title: 78 kDa receptor for Man6P-independent lysosomal enzyme targeting: biosynthetic transport from endoplasmic reticulum to "high-density vesicles".
abstract: Recent work has shown that the cation-independent mannose 6-phosphate and the 78 kDa receptors for lysosomal enzyme targeting are located in different cell compartments. While the mannose 6-phosphate receptor is enriched in the Percoll fractions that contain Golgi apparatus, most of the 78 kDa receptor is localized in a heavy fraction at the bottom of the Percoll gradient. This report presents the biosynthetic transport of the 78 kDa receptor. Newly synthesized 78 kDa receptor was transported to Golgi from endoplasmic reticulum with a half life of 5 min. From the Golgi apparatus, the receptor takes two routes; about 15-25% is transported to the plasma membrane, and the rest migrates to late endosomes, subsequently to prelysosomes and finally to the dense vesicles. The 78 kDa receptor starts appearing at the dense vesicles 120 min after biosynthesis and reaches a maximum of 40-50% of the total receptor. Treatment of cells with NH4Cl causes depletion of the receptor from the dense vesicles and prelysosomes and corresponding augmentation in endosomes and plasma membrane. These results suggest that the 78 kDa receptor cycles between compartments and that the dense vesicles seem to represent the most distal compartment in the biosynthetic pathway of this receptor.
authors.affiliation: Department of Cell Biology and Physiology, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, PO Box 70228, 04510 México, DF, Mexico. gonor@biomedicas.unam.mx
authors.forename: Alfonso
authors.initials: A
authors.lastname: González-Noriega
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Ortega Cuellar
authors.forename: Colette
authors.initials: C
authors.lastname: Michalak
mesh_terms: D000643:Ammonium Chloride; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D004721:Endoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*; D022781:Hepatocytes / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D007700:Kinetics; D008247:Lysosomes / Q000201:enzymology* / Q000378:metabolism; D008360:Mannosephosphates / Q000378:metabolism*; D008970:Molecular Weight; D017830:Octoxynol; D011205:Povidone; D021381:Protein Transport / Q000502:physiology; D017527:Receptor, IGF Type 2 / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism*; D012822:Silicon Dioxide
chemical_list: D008360:Mannosephosphates; D017527:Receptor, IGF Type 2; D000643:Ammonium Chloride; C027693:mannose-6-phosphate; C016039:Percoll; D012822:Silicon Dioxide; D017830:Octoxynol; D011205:Povidone