MOLECULAR-CLONING OF PC3, A PUTATIVELY SECRETED PROTEIN WHOSE MESSENGER-RNA IS INDUCED BY NERVE GROWTH-FACTOR AND DEPOLARIZATION

PC3 is an immediate early gene induced by nerve growth factor in PC12 cells, a cell line derived from a tumor of the adrenal medulla that undergoes neuronal differentiation in the presence of nerve growth factor. This induction is independent of new protein synthesis as it can occur in the presence of cycloheximide. PC3 is also induced with similar kinetics, but at lower levels, by membrane depolarization (both in vivo and in vitro) and epidermal growth factor. It is induced at much lower levels by fibroblast growth factor and interleukin 6. In vivo it is found expressed in tissues, such as brain at embryonic day 13.5, placenta, amnion, and spleen, which are proliferating and/or differentiating. The deduced protein sequence from the cDNA indicates the presence of a signal peptide, suggesting that PC3 is secreted.