Cardiolipin deficiency leads to decreased cardiolipin peroxidation and increased resistance of cells to apoptosis.
Cardiolipin (CL), a unique mitochondrial phospholipid synthesized by CL synthase (CLS), plays important, yet not fully understood, roles in mitochondria-dependent apoptosis. We manipulated CL levels in HeLa cells by knocking down CLS using RNA interference and selected a clone of CL-deficient cells with approximately 45% of its normal content. ESI-MS analysis showed that the CL molecular species were the same in CL-deficient and CL-sufficient cells. CL deficiency did not change mitochondrial functions (membrane potential, reactive oxygen species generation, cellular ATP levels) but conferred resistance to apoptosis induced by actinomycin D (ActD), rotenone, or gamma-irradiation. During ActD-induced apoptosis, decreased CL peroxidation along with suppressed cytochrome (cyt) c release was observed in CL-deficient cells, whereas Bax translocation to mitochondria remained similar to that in CL-sufficient HeLa cells. The amounts of loosely bound cyt c (releasable under high ionic strength conditions) were the same in CL-deficient and CL-sufficient cells. Given that CL peroxidation during apoptosis is catalyzed by CL/cyt c complexes and CL oxidation products are essential for cyt c release from mitochondria, our results suggest that CL deficiency prevents adequate assembly of productive CL/cyt c complexes and CL peroxidation, resulting in increased resistance to apoptosis.
Huang
Zhentai
Z
Center for Free Radical and Antioxidant Health, Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15219, USA.
Jiang
Jianfei
J
Tyurin
Vladimir A
VA
Zhao
Qing
Q
Mnuskin
Alexandra
A
Ren
Jin
J
Belikova
Natalia A
NA
Feng
Weihong
W
Kurnikov
Igor V
IV
Kagan
Valerian E
VE
D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D002308:Cardiolipins / Q000502:physiology*; D045304:Cytochromes c / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D015227:Lipid Peroxidation; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013347:Subcellular Fractions
D002308:Cardiolipins; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; D045304:Cytochromes c