BAX is a critical effector of the mitochondrial cell death pathway in response to a diverse range of stimuli in physiological and disease contexts. Upon binding by BH3-only proteins, cytosolic BAX undergoes conformational activation and translocation, resulting in mitochondrial outer-membrane permeabilization. Efforts to rationally target BAX and develop inhibitors have been elusive, despite the clear therapeutic potential of inhibiting BAX-mediated cell death in a host of diseases. Here, we describe a class of small-molecule BAX inhibitors, termed BAIs, that bind directly to a previously unrecognized pocket and allosterically inhibit BAX activation. BAI binding around the hydrophobic helix α5 using hydrophobic and hydrogen bonding interactions stabilizes key areas of the hydrophobic core. BAIs inhibit conformational events in BAX activation that prevent BAX mitochondrial translocation and oligomerization. Our data highlight a novel paradigm for effective and selective pharmacological targeting of BAX to enable rational development of inhibitors of BAX-mediated cell death.
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We thank B. Agianian and A. Haimowitz for assistance with MST controls and BAX C62S/C126S/S3C mutant preparation. Studies were supported by an American Heart Association Collaborative Science Award (15CSA26240000) to E.G. and R.N.K. Support was also provided by NIH award 1R01CA178394 to E.G. and the Fondation Leducq Transatlantic Network of Excellence grant (RA15CVD04) to E.G. and R.N.K. E.G. is supported by the Pershing Square Sohn Cancer Research Alliance and the Irma T. Hirschl Trust Career Award. NMR data were collected with support from NIH awards 1S10OD016305, P30 CA013330 a grant from NYSTAR.
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Nature Chemical Biology (2019)