NERVE GROWTH FACTOR-INDUCED NEURONAL DIFFERENTIATION IS ACCOMPANIED BY DIFFERENTIAL INDUCTION AND LOCALIZATION OF THE AMYLOID PRECURSOR PROTEIN (APP) IN PC12-CELLS AND VARIANT PC12S-CELLS

PC12 cells and the morphological variant PC12S cells in culture were examined by immunochemical methods for the presence of the amyloid precursor protein (APP), before and after treatment with the nerve growth factor (NGF). In untreated PC12, untreated PC12S and in NGF-treated PC12 cells, APP was localized in the cytoplasm, whereas in NGF-treated PC12S cells, APP was localized at growth cones, processes and cytoplasm. In PC12 cells, three major forms of APP (695 and 751/770) were detected by Western blot. After NGF treatment, only the level of APP 695 was increased. Immunoprecipitation studies in PC12 cells revealed six protein species, corresponding to immature and mature forms of each of the three APP 695, 751 and 770 proteins. Addition of NGF increased the synthesis of the immature and mature forms of APP695. In PC12S cells, only the higher molecular weight forms of AP-P (751/770) were detected by both Western blot and immunoprecipitation. Addition of NGF had no effect on their levels. In both cell types, the level of the secreted form of APP showed a significant transient increase after NGF treatment. These results suggest that NGF can differentially regulate the molecular forms of APP and the localization of APP within the cell.