Inhibition of Bcl-xL prevents pro-death actions of ΔN-Bcl-xL at the mitochondrial inner membrane during glutamate excitotoxicity.

Abstract

ABT-737 is a pharmacological inhibitor of the anti-apoptotic activity of B-cell lymphoma-extra large (Bcl-xL) protein; it promotes apoptosis of cancer cells by occupying the BH3-binding pocket. We have shown previously that ABT-737 lowers cell metabolic efficiency by inhibiting ATP synthase activity. However, we also found that ABT-737 protects rodent brain from ischemic injury in vivo by inhibiting formation of the pro-apoptotic, cleaved form of Bcl-xL, ΔN-Bcl-xL. We now report that a high concentration of ABT-737 (1 μM), or a more selective Bcl-xL inhibitor WEHI-539 (5 μM) enhances glutamate-induced neurotoxicity while a low concentration of ABT-737 (10 nM) or WEHI-539 (10 nM) is neuroprotective. High ABT-737 markedly increased ΔN-Bcl-xL formation, aggravated glutamate-induced death and resulted in the loss of mitochondrial membrane potential and decline in ATP production. Although the usual cause of death by ABT-737 is thought to be related to activation of Bax at the outer mitochondrial membrane due to sequestration of Bcl-xL, we now find that low ABT-737 not only prevents Bax activation, but it also inhibits the decline in mitochondrial potential produced by glutamate toxicity or by direct application of ΔN-Bcl-xL to mitochondria. Loss of mitochondrial inner membrane potential is also prevented by cyclosporine A, implicating the mitochondrial permeability transition pore in death aggravated by ΔN-Bcl-xL. In keeping with this, we find that glutamate/ΔN-Bcl-xL-induced neuronal death is attenuated by depletion of the ATP synthase c-subunit. C-subunit depletion prevented depolarization of mitochondrial membranes in ΔN-Bcl-xL expressing cells and substantially prevented the morphological change in neurites associated with glutamate/ΔN-Bcl-xL insult. Our findings suggest that low ABT-737 or WEHI-539 promotes survival during glutamate toxicity by preventing the effect of ΔN-Bcl-xL on mitochondrial inner membrane depolarization, highlighting ΔN-Bcl-xL as an important therapeutic target in injured brain.

• Authors: Han-A Park, Pawel Licznerski, Nelli Mnatsakanyan, Yulong Niu, Silvio Sacchetti, Jing Wu, Brian M Polster, Kambiz N Alavian, Elizabeth A Jonas
• Journal: Cell death and differentiation (Cell Death Differ) Vol. 24 Issue 11 Pg. 1963-1974 (11 2017) ISSN: 1476-5403 [Electronic] England
• PMID: 28777375 (Publication Type: Journal Article)

Chemical References

• ABT-737
• Biphenyl Compounds
• Mutant Proteins
• Neurotoxins
• Nitrophenols
• Piperazines
• Protein Subunits
• Rhodamines
• Sulfonamides
• bcl-X Protein
• tetramethylrhodamine methyl ester
• Glutamic Acid
• Cyclosporine
• Adenosine Triphosphate
• Mitochondrial Proton-Translocating ATPases

Topics

• Adenosine Triphosphate (metabolism)
• Animals
• Biphenyl Compounds (pharmacology)
• Cell Death (drug effects)
• Cyclosporine (pharmacology)
• Glutamic Acid (toxicity)
• Membrane Potential, Mitochondrial (drug effects)
• Mitochondrial Membranes (drug effects, metabolism)
• Mitochondrial Proton-Translocating ATPases (metabolism)
• Models, Biological
• Mutant Proteins (metabolism)
• Neurites (drug effects, metabolism)
• Neurotoxins (toxicity)
• Nitrophenols (pharmacology)
• Piperazines (pharmacology)
• Protein Subunits (metabolism)
• Rats, Sprague-Dawley
• Rhodamines (metabolism)
• Sulfonamides (pharmacology)
• bcl-X Protein (antagonists & inhibitors, metabolism)