Biosynthesis of the D2-Cell Adhesion Molecule: Post-Translational Modifications, Intracellular Transport, and Developmental Changes

• Published in: The Journal of cell biology 1984-12, Vol.99 (6), p.2082-2091
• Main Authors: Lyles, Joan M., Linnemann, Dorte, Bock, Elisabeth
• Format: Article
• Language: English
• Subjects: Animals; Antigens, Surface - genetics; Antigens, Surface - isolation & purification; Biological and medical sciences; Biological Transport; Biosynthesis; Brain - cytology; Brain - embryology; Cell adhesion; Cell Adhesion Molecules; Cell interactions, adhesion; Cells, Cultured; Cerebral Cortex - cytology; Cerebral Cortex - embryology; Electrophoresis, Polyacrylamide Gel; Fundamental and applied biological sciences. Psychology; Gels; Kinetics; Molecular and cellular biology; Molecular Weight; Molecules; Neurons; Neurons - cytology; Neurons - physiology; Oligosaccharides; Organ Culture Techniques; Phosphorylation; Protein Processing, Post-Translational; Radioactive decay; Rats; Sulfation
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.99.6.2082

Posttranslational modifications and intracellular transport of the D2-cell adhesion molecule (D2-CAM) were examined in cultured fetal rat neuronal cells. Developmental changes in biosynthesis were studied in rat forebrain explant cultures. Two D2-CAM polypeptides with Mr of 187,000-210,000 (A) and 131,000-158,000 (B) were synthesized using radiolabeled precursors in cultured neurons. A and B were found to contain only N-linked complex oligosaccharides, and both polypeptides appeared to be polysialated as determined by [14C]mannosamine incorporation and precipitation with anti-polysialic acid antibody. The two polypeptides were sulfated in the trans-Golgi compartment and phosphorylated at the plasma membrane. D2-CAM underwent rapid intracellular transport, appearing at the cell surface within 35 min of synthesis. A and B were shown to be integral membrane proteins as seen by radioiodination by photoactivation employing a hydrophobic labeling reagent. In rat forebrain explant cultures, D2-CAM was synthesized as four polypeptides: A (195,000 Mr), B (137,000 Mr), C (115,000 Mr), and a group of polypeptides in the high molecular weight region (HMr) between 250,000 and 350,000. Peptide maps of the four polypeptides yielded similar patterns. Biosynthesis of C and HMr increased with age, relative to A and B. A and B were sulfated in embryonic brain, however, sulfation was not noticeable at postnatal ages. Phosphorylation, on the other hand, of A and B was observed at all ages examined. We suggest that D2-CAM function may be modified during development by changes in the relative synthesis of the different polypeptides, as well as by changes in their glycosylation and sulfation.