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J. Cell Biol.,
Volume 143, Number 6, December 14, 1998 1691-1703


* Center for Neuronal Survival and Naturally occurring sympathetic neuron
death is the result of two apoptotic signaling events:
one normally suppressed by NGF/TrkA survival signals, and a second activated by the p75 neurotrophin receptor. Here we demonstrate that the p53 tumor suppressor protein, likely as induced by the MEKK-JNK
pathway, is an essential component of both of these
apoptotic signaling cascades. In cultured neonatal sympathetic neurons, p53 protein levels are elevated in
response to both NGF withdrawal and p75NTR activation. NGF withdrawal also results in elevation of a
known p53 target, the apoptotic protein Bax. Functional ablation of p53 using the adenovirus E1B55K
protein inhibits neuronal apoptosis as induced by either
NGF withdrawal or p75 activation. Direct stimulation
of the MEKK-JNK pathway using activated MEKK1
has similar effects; p53 and Bax are increased and the
subsequent neuronal apoptosis can be rescued by
E1B55K. Expression of p53 in sympathetic neurons indicates that p53 functions downstream of JNK and upstream of Bax. Finally, when p53 levels are reduced or
absent in p53+/
Brain Tumor Center, Montreal Neurological Institute, McGill University, Montreal,
Quebec, Canada H3A 2B4
or p53
/
mice, naturally occurring sympathetic neuron death is inhibited. Thus, p53 is an
essential common component of two receptor-mediated signal transduction cascades that converge on the
MEKK-JNK pathway to regulate the developmental
death of sympathetic neurons.
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