Biosynthesis of the D2-cell adhesion molecule: post-translational modifications, intracellular transport, and developmental changes
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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.
Original language | English |
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Journal | Journal of Cell Biology |
Volume | 99 |
Issue number | 6 |
Pages (from-to) | 2082-91 |
Number of pages | 9 |
ISSN | 0021-9525 |
Publication status | Published - 1984 |
Bibliographical note
Keywords: Animals; Antigens, Surface; Biological Transport; Brain; Cell Adhesion Molecules; Cells, Cultured; Cerebral Cortex; Electrophoresis, Polyacrylamide Gel; Kinetics; Molecular Weight; Neurons; Organ Culture Techniques; Protein Processing, Post-Translational; Rats
ID: 21607225