title: Caspase-8 binding to cardiolipin in giant unilamellar vesicles provides a functional docking platform for bid.
abstract: Caspase-8 is involved in death receptor-mediated apoptosis in type II cells, the proapoptotic programme of which is triggered by truncated Bid. Indeed, caspase-8 and Bid are the known intermediates of this signalling pathway. Cardiolipin has been shown to provide an anchor and an essential activating platform for caspase-8 at the mitochondrial membrane surface. Destabilisation of this platform alters receptor-mediated apoptosis in diseases such as Barth Syndrome, which is characterised by the presence of immature cardiolipin which does not allow caspase-8 binding. We used a simplified in vitro system that mimics contact sites and/or cardiolipin-enriched microdomains at the outer mitochondrial surface in which the platform consisting of caspase-8, Bid and cardiolipin was reconstituted in giant unilamellar vesicles. We analysed these vesicles by flow cytometry and confirm previous results that demonstrate the requirement for intact mature cardiolipin for caspase-8 activation and Bid binding and cleavage. We also used confocal microscopy to visualise the rupture of the vesicles and their revesiculation at smaller sizes due to alteration of the curvature following caspase-8 and Bid binding. Biophysical approaches, including Laurdan fluorescence and rupture/tension measurements, were used to determine the ability of these three components (cardiolipin, caspase-8 and Bid) to fulfil the minimal requirements for the formation and function of the platform at the mitochondrial membrane. Our results shed light on the active functional role of cardiolipin, bridging the gap between death receptors and mitochondria.
authors: Université Paris-Descartes, Centre de recherche des Saint-Pères, UMR S-747, Toxicology, Pharmacologie et Signalisation cellulaire, Paris, France.
authors: Olivier
authors: O
authors: Jalmar
authors: Liberty
authors: L
authors: François-Moutal
authors: Ana-Jesus
authors: AJ
authors: García-Sáez
authors: Mark
authors: M
authors: Perry
authors: Thierry
authors: T
authors: Granjon
authors: François
authors: F
authors: Gonzalvez
authors: Eyal
authors: E
authors: Gottlieb
authors: Jesus
authors: J
authors: Ayala-Sanmartin
authors: Beate
authors: B
authors: Klösgen
authors: Petra
authors: P
authors: Schwille
authors: Patrice X
authors: PX
authors: Petit
mesh_terms: D017209:Apoptosis / Q000502:physiology; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism*; D001665:Binding Sites; D002308:Cardiolipins / Q000378:metabolism*; D053181:Caspase 8 / Q000378:metabolism*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D011485:Protein Binding; D053835:Unilamellar Liposomes / Q000378:metabolism*
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; D002308:Cardiolipins; D053835:Unilamellar Liposomes; D053181:Caspase 8