Inhibition of nuclear factor-kappaB activation induces apoptosis in cerebellar granule cells.
The nuclear factor (NF)-kappaB family of transcription factors plays important roles in the regulation of many activities of neuronal cells, such as synaptic transmission, inflammation, neuroprotection, and neurotoxicity. In resting cells, NF-kappaB activity is present both in the cytoplasm, as an inducible-inactive complex, and in the nucleus, as a constitutive form. Regulation of its inducible activity relies on processing of IkappaB(s), which occurs through the proteasome. Here we show that in cerebellar granule cells (CGC) the induction of apoptosis, by potassium withdrawal (5 mM KCl), decreases the amount of nuclear NF-kappaB. To understand whether NF-kappaB was required for CGC survival, these cells, maintained under depolarizing conditions (25 mM KCl and serum), were treated with proteasome inhibitors. The results show that these treatments reduce the nuclear amount of NF-kappaB and increase p65 cytoplasmic levels, a process partially regulated via IkappaBalpha degradation. These events are also associated with an impairment in CGC survival, with changes in nuclear morphology, induction of DNA laddering, and oligonucleosome formation, consistent with apoptosis. According to the K+ deprivation model, PSI-induced apoptosis is reversed by inhibitors of transcription and translation as well as by specific caspase inhibitors. Together our results show an important role for NF-kappaB in maintaining CGC survival. Indeed, under conditions of mild depolarization (K25) necessary for CGC survival, NF-kappaB is distributed between cytosol and nucleus, whereas, under apoptotic conditions (K5), it is depleted from the nucleus, such as after proteasome inhibitor treatment. Therefore, NF-kappaB nuclear deprivation is involved in the induction of CGC apoptosis.
Piccioli
P
P
Section of Pharmacology and Neuroscience, National Institute for Cancer Research (IST), c/o Advanced Biotechnology Center (CBA), Largo Rosanna Benzi 10, 16132 Genoa, Italy.
Porcile
C
C
Stanzione
S
S
Bisaglia
M
M
Bajetto
A
A
Bonavia
R
R
Florio
T
T
Schettini
G
G
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002490:Central Nervous System / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D002531:Cerebellum / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011191:Potassium Deficiency / Q000378:metabolism / Q000503:physiopathology; D046988:Proteasome Endopeptidase Complex; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D051996:Transcription Factor RelA; D014157:Transcription Factors / Q000378:metabolism
D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D016328:NF-kappa B; D051996:Transcription Factor RelA; D014157:Transcription Factors; D020169:Caspases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex