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Evidence for carboxyl-terminal processing and glycolipid-anchoring of human carcinoembryonic antigen.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 1988 Sep 05; Vol. 263 (25), pp. 12716-20. - Publication Year :
- 1988
-
Abstract
- We have investigated the post-translational modification of carcinoembryonic antigen (CEA) for membrane-anchoring in QGP-1 cells derived from a human pancreatic carcinoma. Pulse-chase experiments with [3H]leucine demonstrated that CEA was initially synthesized as a precursor form with Mr 150,000 having N-linked high-mannose-type oligosaccharides, which was then converted to a mature form with Mr 200,000 containing the complex type sugar chains. The mature protein thus labeled was found to be released from the cell surface by treatment with phosphatidylinositol-specific phospholipase C, suggesting that CEA is a phosphatidylinositol-linked membrane protein. This was confirmed by metabolic incorporation into CEA of 3H-labeled compounds such as ethanolamine, myo-inositol, palmitic acid, and stearic acid. The 3H-labeled fatty acids incorporated were specifically removed from the protein by nitrous acid deamination as well as by phosphatidylinositol-specific phospholipase C treatment. Since the available cDNA sequence predicts that CEA contains a single methionine residue only in its carboxyl-terminal hydrophobic domain, processing of the carboxyl terminus was examined by pulse-chase experiments with [35S]methionine. It was found that CEA with Mr 150,000 was initially labeled with [35S]methionine but its radioactivity was immediately lost with chase. Taken together, these results suggest that CEA is anchored to the membrane by simultaneously occurring proteolysis of the carboxyl terminus and replacement by the glycophospholipid immediately after the synthesis.
- Subjects :
- Carcinoma immunology
Cell Membrane immunology
Electrophoresis, Polyacrylamide Gel
Fatty Acids metabolism
Glycolipids immunology
Hexosaminidases pharmacology
Humans
Immunosorbent Techniques
Mannose analysis
Membrane Proteins immunology
Methionine metabolism
Molecular Weight
Nitrous Acid
Oligosaccharides analysis
Pancreatic Neoplasms immunology
Phosphatidylinositol Diacylglycerol-Lyase
Phosphatidylinositols metabolism
Phosphoinositide Phospholipase C
Phosphoric Diester Hydrolases metabolism
Tumor Cells, Cultured
Tunicamycin pharmacology
Carcinoembryonic Antigen analysis
Glycolipids metabolism
Protein Processing, Post-Translational
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 263
- Issue :
- 25
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 2842340