Volume 21, No 4, Apr 2011

ISSN: 1001-0602 
EISSN: 1748-7838 2018 
impact factor 17.848* 
(Clarivate Analytics, 2019)

Volume 21 Issue 4, April 2011: 627-641

ORIGINAL ARTICLES

Evidence that inhibition of BAX activation by BCL-2 involves its tight and preferential interaction with the BH3 domain of BAX

Bonsu Ku^1,*, Chengyu Liang^2,*, Jae U Jung² and Byung-Ha Oh¹

¹Department of Biological Sciences, KAIST Institute for the Biocentury, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea

²Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA Correspondence: Byung-Ha Oh(bhoh@kaist.ac.kr)

Interactions between the BCL-2 family proteins determine the cell's fate to live or die. How they interact with each other to regulate apoptosis remains as an unsettled central issue. So far, the antiapoptotic BCL-2 proteins are thought to interact with BAX weakly, but the physiological significance of this interaction has been vague. Herein, we show that recombinant BCL-2 and BCL-w interact potently with a BCL-2 homology (BH) 3 domain-containing peptide derived from BAX, exhibiting the dissociation constants of 15 and 23 nM, respectively. To clarify the basis for this strong interaction, we determined the three-dimensional structure of a complex of BCL-2 with a BAX peptide spanning its BH3 domain. It revealed that their interactions extended beyond the canonical BH3 domain and involved three nonconserved charged residues of BAX. A novel BAX variant, containing the alanine substitution of these three residues, had greatly impaired affinity for BCL-2 and BCL-w, but was otherwise indistinguishable from wild-type BAX. Critically, the apoptotic activity of the BAX variant could not be restrained by BCL-2 and BCL-w, pointing that the observed tight interactions are critical for regulating BAX activation. We also comprehensively quantified the binding affinities between the three BCL-2 subfamily proteins. Collectively, the data show that due to the high affinity of BAX for BCL-2, BCL-w and A1, and of BAK for BCL-X_L, MCL-1 and A1, only a subset of BH3-only proteins, commonly including BIM, BID and PUMA, could be expected to free BAX or BAK from the antiapoptotic BCL-2 proteins to elicit apoptosis.

Cell Research (2011) 21:627-641. doi:10.1038/cr.2010.149; published online 9 November 2010

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