Fig. 6.

The JNK-signaling pathway mediates neurotrophin-induced death of hippocampal neurons. a, NGF induces JNK phosphorylation in hippocampal neurons. Neurons were treated with NGF (100 ng/ml) for the times indicated. b, JNK phosphorylation was also induced by BDNF and NT3 (100 ng/ml) treatment of hippocampal neurons, but not by mutant NGF (tri-NGF) that lacks p75 binding. Shown is a 20 min time point. c, Cultures were treated with NGF for 20 min in the presence or absence of CEP-1347/KT7515 (CEP). Incubation of cells with 200 nm CEP-1347/KT7515 prevented JNK phosphorylation by NGF, whereas CEP-1347/KT7515 by itself had no effect. d, Phosphorylation of JNK by NGF was prevented by anti-p75 (9651). Cells were pretreated for 1 hr with anti-p75 and then exposed to NGF (100 ng/ml). A 20 min time point is shown. Blots shown ina–d were probed for P-JNK (top panels) and stripped and reprobed for JNK (bottom panels).e, Prevention of JNK activation with CEP-1347/KT7515 blocked neurotrophin-induced death. Cultures were treated with neurotrophins overnight in the absence (open bars) or presence (hatched bars) of 200 nmCEP-1347/KT7515. Data are expressed relative to the control number of cells in the absence of added neurotrophins. An asteriskindicates values different from control at p < 0.01. Data are from triplicate samples from three independent experiments (n = 9).