The cardiolipin-binding domain of Bid affects mitochondrial respiration and enhances cytochrome c release.
Bid is cleaved by caspase 8 during apoptosis and the truncated Bid (tBid) translocates to mitochondria by targeting cardiolipin. Amino acids 103-162 of Bid were reported as the cardiolipin-binding domain (CBD). The EGFP-CBD fusion protein targets to mitochondria and induces apoptosis. Using [(3)H]cardiolipin, we proved that recombinant CBD binds cardiolipin similar to tBid and tBid(G94E), a mutant with a defective BH3 domain. CBD could induce cytochrome c release from isolated mitochondria, but much less potent than tBid. Free cardiolipin inhibited the CBD-induced cytochrome c release, suggesting that it may be mediated by interfering with mitochondrial cardiolipin, especially with the interaction between cytochrome c and cardiolipin. This is consistent with the findings that CBD induced cytochrome c release in Bax-deficient cells, and that CBD suppressed mitochondrial respiration through directly interfering with cardiolipin, a critical lipid involved in oxidative phosphorylation. These results indicate the functional importance of CBD in tBid-induced apoptosis.
Huntsman Cancer Institute, Department of Internal Medicine, University of Utah, Salt Lake City, UT 84112, USA.
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Liu
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Weiss
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Durrant
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Chi
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Lee
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein; D001665:Binding Sites; D002308:Cardiolipins / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D002474:Cell-Free System; D045304:Cytochromes c / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D010101:Oxygen Consumption / Q000502:physiology*; D011994:Recombinant Proteins / Q000378:metabolism; D051025:bcl-Associated Death Protein
C494819:BAD protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; C494814:BID protein, human; C494820:Bad protein, mouse; C494815:Bid protein, mouse; D002308:Cardiolipins; D002352:Carrier Proteins; D011994:Recombinant Proteins; D051025:bcl-Associated Death Protein; D045304:Cytochromes c