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Apical transport and folding of prostate-specific membrane antigen occurs independent of glycan processing.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 2006 Feb 10; Vol. 281 (6), pp. 3505-12. Date of Electronic Publication: 2005 Oct 12. - Publication Year :
- 2006
-
Abstract
- Prostate-specific membrane antigen (PSMA) is an integral cell-surface membrane glycoprotein that is overexpressed in prostate carcinomas rendering it an appropriate target for antibody-based therapeutic strategies. The biosynthesis of PSMA in transfected COS-1 cells reveals a slow conversion of mannose-rich to complex glycosylated PSMA compatible with slow transport kinetics from the endoplasmic reticulum to the Golgi. Importantly, mannose-rich PSMA persists as a trypsin-sensitive protein throughout its entire life cycle, and only Golgi-located PSMA glycoforms acquire trypsin resistance. This resistance, used here as a tool to examine correct folding, does not depend on the type of glycosylation, because different PSMA glycoforms generated in the presence of inhibitors of carbohydrate processing in the Golgi are also trypsin resistant. The conformational transition of PSMA to a correctly folded molecule is likely to occur in the Golgi and does not implicate ER molecular chaperones, such as BiP. We show here that PSMA is not only heavily N-but also O-glycosylated. The question arising is whether glycans, which do not play a role in folding of PSMA, are implicated in its transport to the cell surface. Neither the cell-surface expression of PSMA nor its efficient apical sorting in polarized Madin-Darby canine kidney cells are influenced by modulators of N- and O-glycosylation. The acquisition of folding determinants in the Golgi, therefore, is an essential prerequisite for protein trafficking and sorting of PSMA and suggests that altered or aberrant glycosylation often occurring during tumorigenesis has no regulatory effect on the cell-surface expression of PSMA.
- Subjects :
- Amino Acid Motifs
Animals
Biological Transport
Biotinylation
Blotting, Western
COS Cells
Calnexin chemistry
Cell Line
Cell Line, Tumor
Cell Membrane metabolism
Chlorocebus aethiops
Cloning, Molecular
DNA, Complementary metabolism
Dogs
Endoplasmic Reticulum metabolism
Fluorescent Antibody Technique, Indirect
Glycosylation
Golgi Apparatus metabolism
Humans
Immunoprecipitation
Kinetics
Male
Mannose chemistry
Neoplasm Metastasis
Prostatic Neoplasms metabolism
Protein Binding
Protein Folding
Protein Isoforms
Transfection
Trypsin chemistry
Antigens, Surface biosynthesis
Antigens, Surface chemistry
Glutamate Carboxypeptidase II biosynthesis
Glutamate Carboxypeptidase II chemistry
Polysaccharides chemistry
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 281
- Issue :
- 6
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 16221666
- Full Text :
- https://doi.org/10.1074/jbc.M509460200