Leukemia Inhibitory Factor Requires Concurrent
p75LNTR Signaling to Induce Apoptosis of Cultured
Sympathetic Neurons
Sean I.
Savitz and
John A.
Kessler
Departments of Neurology and Neuroscience, Albert Einstein College
of Medicine, Bronx, New York 10461
Apoptosis may result either from positive induction by ligand
binding to a plasma membrane receptor or from negative induction attributable to loss of a suppressor signal. For example, apoptosis of
developing sympathetic neurons may be induced in culture either by
exposure to leukemia inhibitory factor (LIF) or by deprivation of nerve
growth factor. This study compared the cell death pathways activated in sympathetic neurons by these two different stimuli. Both
types of cell death were developmentally regulated; both were maximal
in the immediate postnatal period and disappeared over the next 2 weeks. Both types of cell death were reduced by genetic deletion of Bax
or by virally mediated overexpression of Bcl-2. Similarly both were
reduced by inhibition of caspase activity or by inhibition of
Nedd-2 synthesis with antisense oligonucleotides. Finally, both
involved activation of c-Jun N-terminal kinase (JNK) signaling. Nedd-2
expression by sympathetic neurons declined in parallel with the
developmental loss of LIF-mediated cell death, suggesting that
downregulation of the caspase during development may underlie the loss
of cytokine-mediated apoptosis. Treatment of sympathetic neurons with
an antibody that blocks the function of the low-affinity neurotrophin
receptor (p75LNTR) prevented LIF-induced cell
death. Similarly genetic deletion of p75LNTR
prevented apoptosis after LIF treatment. These observations suggest that concurrent p75LNTR signaling is necessary for
LIF-induced cell death and that cytokine-mediated cell death and growth
factor deprivation appear to activate the same intracellular pathways
involving JNK signaling.
Key words:
apoptosis; c-JUN N-terminal kinase; gp130; leukemia inhibitory factor; p75; sympathetic neuron
Copyright © 2000 Society for Neuroscience 0270-6474/00/20114198-08$05.00/0