AUTOCRINE REGULATION OF APOPTOSIS AND BCL-2 EXPRESSION BY NERVE GROWTH-FACTOR IN EARLY DIFFERENTIATING CEREBELLAR GRANULE NEURONS INVOLVES LOW-AFFINITY NEUROTROPHIN RECEPTOR
Y. Muller et al., AUTOCRINE REGULATION OF APOPTOSIS AND BCL-2 EXPRESSION BY NERVE GROWTH-FACTOR IN EARLY DIFFERENTIATING CEREBELLAR GRANULE NEURONS INVOLVES LOW-AFFINITY NEUROTROPHIN RECEPTOR, Neurochemistry international, 31(2), 1997, pp. 177-191
Cerebellar granule neurons produce homogenous cultures that provide a
unique opportunity for quantifying the apoptosis by propidium iodide-
and deoxynucleotidyl transferase-flow cytometry combined analysis and
for studying its regulation by neurotrophins. Nerve growth factor (NGF
) was found to promote postmitotic survival by preventing apoptosis of
newly formed and early differentiated granule neurons. This regulatio
n could be through protein bcl-2, which was underexpressed in apoptoti
c granule neurons and up-regulated by NGF in a dose-dependent manner.
Antibodies against low affinity NGF receptors (p75(NTR)) mimicked the
effects of NGF, suggesting that this receptor, which is transiently ex
pressed al high levels in postmitotic granule neurons, is involved in
apoptosis signaling. Since these neurons constitutively produce NGF, t
his is the first demonstration of an autocrine regulation of apoptosis
in the CNS. Preliminary results strongly suggestg that neurotrophin-3
(NT-3) and brain derived neurotrophic factor (BDNF) are also involved
in the regulation of cell death, by first promoting necrosis and then
protecting the remaining cells from apoptosis. In contrast, NGF may p
rotect against two forms of cell death and act preferentially at early
stages of granule neuron development. The possibility that these neur
otrophins may act in parallel and/or in sequence to regulate survival
of developing granule neurons through different mechanisms is discusse
d in the light of findings on neurotrophin and p75(NTR) patterns, and
p75(NTR)/high affinity Trk receptor coexpression. (C) 1997 Elsevier Sc
ience Ltd.