title: Bax assembly into rings and arcs in apoptotic mitochondria is linked to membrane pores.
abstract: Bax is a key regulator of apoptosis that, under cell stress, accumulates at mitochondria, where it oligomerizes to mediate the permeabilization of the mitochondrial outer membrane leading to cytochrome c release and cell death. However, the underlying mechanism behind Bax function remains poorly understood. Here, we studied the spatial organization of Bax in apoptotic cells using dual-color single-molecule localization-based super-resolution microscopy. We show that active Bax clustered into a broad distribution of distinct architectures, including full rings, as well as linear and arc-shaped oligomeric assemblies that localized in discrete foci along mitochondria. Remarkably, both rings and arcs assemblies of Bax perforated the membrane, as revealed by atomic force microscopy in lipid bilayers. Our data identify the supramolecular organization of Bax during apoptosis and support a molecular mechanism in which Bax fully or partially delineates pores of different sizes to permeabilize the mitochondrial outer membrane.
authors.affiliation: Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany Max Planck Institute for Intelligent Systems, Stuttgart, Germany.
authors.forename: Raquel
authors.initials: R
authors.lastname: Salvador-Gallego
authors.affiliation: European Molecular Biology Laboratory, Heidelberg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Mund
authors.affiliation: Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany Max Planck Institute for Intelligent Systems, Stuttgart, Germany.
authors.forename: Katia
authors.initials: K
authors.lastname: Cosentino
authors.affiliation: German Cancer Research Center, Heidelberg, Germany.
authors.forename: Jale
authors.initials: J
authors.lastname: Schneider
authors.affiliation: Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany Max Planck Institute for Intelligent Systems, Stuttgart, Germany.
authors.forename: Joseph
authors.initials: J
authors.lastname: Unsay
authors.affiliation: Core Facility for Electron Microscopy Section for Experimental Vitreoretinal Surgery, Universitätsklinikum Tübingen, Tübingen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schraermeyer
authors.affiliation: German Cancer Research Center, Heidelberg, Germany.
authors.forename: Johann
authors.initials: J
authors.lastname: Engelhardt
authors.affiliation: European Molecular Biology Laboratory, Heidelberg, Germany ana.garcia@uni-tuebingen.de jonas.ries@embl.de.
authors.forename: Jonas
authors.initials: J
authors.lastname: Ries
authors.affiliation: Interfaculty Institute of Biochemistry, University of Tübingen, Tübingen, Germany Max Planck Institute for Intelligent Systems, Stuttgart, Germany ana.garcia@uni-tuebingen.de jonas.ries@embl.de.
authors.forename: Ana J
authors.initials: AJ
authors.lastname: García-Sáez
mesh_terms: D017209:Apoptosis; D045304:Cytochromes c / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D046529:Microscopy, Electron, Transmission; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000201:enzymology*; D051336:Mitochondrial Membranes / Q000378:metabolism* / Q000502:physiology; D010539:Permeability; D052899:Pore Forming Cytotoxic Proteins / Q000378:metabolism*; D055503:Protein Multimerization; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
chemical_list: C494826:BAX protein, human; D052899:Pore Forming Cytotoxic Proteins; D051028:bcl-2-Associated X Protein; D045304:Cytochromes c
keywords: AFM; Bcl‐2; apoptosis; pore‐forming protein; super‐resolution microscopy