NERVE GROWTH-FACTOR INHIBITS APOPTOSIS INDUCED BY S-100 BINDING IN NEURONAL PC12 CELLS

When grown for seven days in a medium containing nerve growth factor ( 100 ng/ml), 10% horse serum and 5% fetal bovine serum PC12 cells stopp ed dividing, extended neurites and assumed a neuronal phenotype. Withd rawal of nerve growth factor from these cells resulted in loss of neur ites and apoptotic changes in many cells. The apoptotic changes were e xacerbated if the cells were also exposed to 1-2 mu M S-100, a calcium binding protein purified from bovine brain. After exposure to S-100, the PC12 cells underwent characteristic apoptotic changes. Within 2 h neurites retracted, the cell body shrunk and submembranous accumulatio n of condensed cytoplasmic material was observed. DNA ladders were pre sent after 24-48 h and 60% of the cells became hypodiploid after 72 h. S-100 induced apoptosis by binding to specific sites (K-d=189 nM) on PC12 cells and this caused a rise in [Ca2+](i) due to a transmembrane capacitative flux followed by the depletion of internal stores. This i ncrease was reversed if 5 mu M nifedipine, a specific L-type Ca2+ chan nel inhibitor, was added to the medium after S-100 and completely abol ished if the cells were pretreated with 5 mM thapsigargin, an inhibito r of endoplasmic reticulum Ca2+-ATPase. The presence of nerve growth f actor in the culture medium completely blocked the apoptotic changes i nduced by S-100, probably due to interaction of nerve growth factor an d S-100 at the same binding sites. These data indicate that nerve grow th factor not only prevents apoptosis during cell development, but als o apoptosis induced by endogenous substances such as S-100. Copyright 1996 IBRO.