title: Tauroursodeoxycholic acid prevents Bax-induced membrane perturbation and cytochrome C release in isolated mitochondria.
abstract: Bax is a potent pro-apoptotic member of the Bcl-2 protein family that localizes to the mitochondrial membrane during apoptosis. Tauroursodeoxycholic acid (TUDCA) modulates the apoptotic threshold, in part, by preventing Bax translocation both in vitro and in vivo. The mechanisms by which Bax induces and TUDCA inhibits release of cytochrome c are unclear. We show here that recombinant Bax protein induced cytochrome c release in isolated mitochondria without detectable swelling. Co-incubation with TUDCA prevented efflux of mitochondrial factors and proteolytic processing of caspases in cytosolic extracts. Spectroscopic analyses of mitochondria exposed to Bax revealed increased polarity and fluidity of the membrane lipid core as well as altered protein order, indicative of Bax binding, together with loss of spin-label paramagnetism, characteristic of oxidative damage. TUDCA markedly abrogated the Bax-induced membrane perturbation. In conclusion, our results indicate that Bax protein directly induces cytochrome c release from mitochondria through a mechanism that does not require the permeability transition. Rather, it is accompanied by changes in the organization of membrane lipids and proteins. TUDCA is a potent inhibitor of Bax association with mitochondria. Thus, TUDCA modulates apoptosis by suppressing mitochondrial membrane perturbation through pathways that are also independent of the mitochondrial permeability transition.
authors.affiliation: Centro de Patogénese Molecular, Faculty of Pharmacy, University of Lisbon, Lisbon 1600-083, Portugal. cmprodrigues@ff.ul.pt
authors.forename: Cecília M P
authors.initials: CM
authors.lastname: Rodrigues
authors.forename: Susana
authors.initials: S
authors.lastname: Solá
authors.forename: Juanita C
authors.initials: JC
authors.lastname: Sharpe
authors.forename: José J G
authors.initials: JJ
authors.lastname: Moura
authors.forename: Clifford J
authors.initials: CJ
authors.lastname: Steer
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007425:Intracellular Membranes / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008563:Membrane Lipids / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008930:Mitochondria, Liver / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology*; D008933:Mitochondrial Swelling / Q000187:drug effects / Q000502:physiology; D010084:Oxidation-Reduction / Q000187:drug effects; D010539:Permeability / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000502:physiology; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D013655:Taurochenodeoxycholic Acid / Q000494:pharmacology / Q000502:physiology*; D051028:bcl-2-Associated X Protein
chemical_list: C494826:BAX protein, human; C494828:Bax protein, rat; D003574:Cytochrome c Group; D008563:Membrane Lipids; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D051028:bcl-2-Associated X Protein; D013655:Taurochenodeoxycholic Acid; C031655:ursodoxicoltaurine; D020169:Caspases