Inhibition of Pro-Apoptotic BAX by a Noncanonical Interaction Mechanism

Lauren A. Barclay, Thomas E. Wales, Thomas P. Garner, Franziska Wachter, Susan Lee, Rachel M. Guerra, Michelle L. Stewart, Craig R. Braun, Gregory H. Bird, Evripidis Gavathiotis, John R. Engen, Loren D. Walensky

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Abstract

BCL-2 is a negative regulator of apoptosis implicated in homeostatic and pathologic cell survival. The canonical anti-apoptotic mechanism involves entrapment of activated BAX by a groove on BCL-2, preventing BAX homo-oligomerization and mitochondrial membrane poration. The BCL-2 BH4 domain also confers anti-apoptotic functionality, but the mechanism is unknown. We find that a synthetic α-helical BH4 domain binds to BAX with nanomolar affinity and independently inhibits the conformational activation of BAX. Hydrogen-deuterium exchange mass spectrometry demonstrated that the N-terminal conformational changes in BAX induced by a triggering BIM BH3 helix were suppressed by the BCL-2 BH4 helix. Structural analyses localized the BH4 interaction site to a groove formed by residues of α1, α1-α2 loop, and α2-α3 and α5-α6 hairpins on the BAX surface. These data reveal a previously unappreciated binding site for targeted inhibition of BAX and suggest that the BCL-2 BH4 domain may participate in apoptosis blockade by a noncanonical interaction mechanism.

Original languageEnglish (US)
Pages (from-to)873-886
Number of pages14
JournalMolecular Cell
Volume57
Issue number5
DOIs
StatePublished - Mar 5 2015

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ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

Cite this

Barclay, L. A., Wales, T. E., Garner, T. P., Wachter, F., Lee, S., Guerra, R. M., Stewart, M. L., Braun, C. R., Bird, G. H., Gavathiotis, E., Engen, J. R., & Walensky, L. D. (2015). Inhibition of Pro-Apoptotic BAX by a Noncanonical Interaction Mechanism. Molecular Cell, 57(5), 873-886. https://doi.org/10.1016/j.molcel.2015.01.014