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Distinct mechanisms of neuronal apoptosis are triggered by antagonism of Bcl‐2/Bcl‐x(L) versus induction of the BH3‐only protein Bim
Author(s) -
Zimmermann Angela K.,
Loucks F. Alexandra,
Le Shoshona S.,
Butts Brent D.,
FlorezMcClure Maria L.,
Bouchard Ron J.,
Heidenreich Kim A.,
Linseman Daniel A.
Publication year - 2005
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2005.03156.x
Subject(s) - apoptosis , programmed cell death , depolarization , microbiology and biotechnology , cytochrome c , biology , bcl 2 associated x protein , glutathione , chemistry , caspase 3 , biochemistry , biophysics , enzyme
Primary cerebellar granule neurons (CGNs) require depolarizing extracellular potassium for their survival. Removal of depolarizing potassium triggers CGN apoptosis that requires induction of Bim, a BH3‐only Bcl‐2 family member. Bim is classically thought to promote apoptosis by neutralizing pro‐survival Bcl‐2 proteins. To determine if this is the principal function of Bim in CGNs, we contrasted Bim‐mediated apoptosis to neuronal death induced by HA14‐1, a BH3‐domain mimetic that antagonizes Bcl‐2 and Bcl‐x(L). HA14‐1 elicited CGN apoptosis characterized by caspase 3 and 9 activation, cytochrome c release, conformational activation of Bax, and mitochondrial depolarization. HA14‐1 provoked CGN apoptosis in the absence of Bim induction and negative regulators of Bim transcription did not prevent HA14‐1‐induced cell death. However, the antioxidant glutathione and its precursor, N ‐acetyl‐ l ‐cysteine, suppressed HA14‐1‐induced apoptosis. Similarly, apoptosis induced by either a structurally distinct Bcl‐2/Bcl‐x(L) inhibitor (compound 6) or Bcl‐2 antisense oligonucleotides was diminished by glutathione. In contrast, antioxidants had no effect on CGN apoptosis provoked by either removal of depolarizing potassium or overexpression of a GFP–Bim fusion protein, two models of Bim‐dependent death. These data show that antagonism of Bcl‐2/Bcl‐x(L) function elicits oxidative stress‐dependent CGN apoptosis that is mechanistically distinct from Bim‐mediated cell death. These results further indicate that, although Bcl‐2/Bcl‐x(L) antagonism is sufficient to induce neuronal apoptosis, Bim likely promotes neuronal death by interacting with additional proteins besides Bcl‐2/Bcl‐x(L).