Genetic ablation of calcium-independent phospholipase A(2)γ (iPLA(2)γ) attenuates calcium-induced opening of the mitochondrial permeability transition pore and resultant cytochrome c release.
Herein, we demonstrate that calcium-independent phospholipase A(2)γ (iPLA(2)γ) is a critical mechanistic participant in the calcium-induced opening of the mitochondrial permeability transition pore (mPTP). Liver mitochondria from iPLA(2)γ(-/-) mice were markedly resistant to calcium-induced swelling in the presence or absence of phosphate in comparison with wild-type littermates. Furthermore, the iPLA(2)γ enantioselective inhibitor (R)-(E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one ((R)-BEL) was markedly more potent than (S)-BEL in inhibiting mPTP opening in mitochondria from wild-type liver in comparison with hepatic mitochondria from iPLA(2)γ(-/-) mice. Intriguingly, low micromolar concentrations of long chain fatty acyl-CoAs and the non-hydrolyzable thioether analog of palmitoyl-CoA markedly accelerated Ca(2+)-induced mPTP opening in liver mitochondria from wild-type mice. The addition of l-carnitine enabled the metabolic channeling of acyl-CoA through carnitine palmitoyltransferases (CPT-1/2) and attenuated the palmitoyl-CoA-mediated amplification of calcium-induced mPTP opening. In contrast, mitochondria from iPLA(2)γ(-/-) mice were insensitive to fatty acyl-CoA-mediated augmentation of calcium-induced mPTP opening. Moreover, mitochondria from iPLA(2)γ(-/-) mouse liver were resistant to Ca(2+)/t-butyl hydroperoxide-induced mPTP opening in comparison with wild-type littermates. In support of these findings, cytochrome c release from iPLA(2)γ(-/-) mitochondria was dramatically decreased in response to calcium in the presence or absence of either t-butyl hydroperoxide or phenylarsine oxide in comparison with wild-type littermates. Collectively, these results identify iPLA(2)γ as an important mechanistic component of the mPTP, define its downstream products as potent regulators of mPTP opening, and demonstrate the integrated roles of mitochondrial bioenergetics and lipidomic flux in modulating mPTP opening promoting the activation of necrotic and necroapoptotic pathways of cell death.
Department of Medicine, Division of Bioorganic Chemistry and Molecular Pharmacology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Sung Ho
SH
Moon
Christopher M
CM
Jenkins
Michael A
MA
Kiebish
Harold F
HF
Sims
David J
DJ
Mancuso
Richard W
RW
Gross
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002331:Carnitine / Q000235:genetics / Q000378:metabolism; D002334:Carnitine O-Palmitoyltransferase / Q000235:genetics / Q000378:metabolism; D016923:Cell Death; D045304:Cytochromes c / Q000235:genetics / Q000378:metabolism; D004734:Energy Metabolism / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D054522:Group VI Phospholipases A2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D050356:Lipid Metabolism / Q000187:drug effects / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008930:Mitochondria, Liver / Q000235:genetics / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D010171:Palmitoyl Coenzyme A / Q000235:genetics / Q000378:metabolism; D011817:Rabbits
D004791:Enzyme Inhibitors; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D010171:Palmitoyl Coenzyme A; D045304:Cytochromes c; D002334:Carnitine O-Palmitoyltransferase; D054522:Group VI Phospholipases A2; C516476:Pla2g6 protein, mouse; D002331:Carnitine; D002118:Calcium