2. Academic Validation
  3. Humanin induces conformational changes in the apoptosis regulator BAX and sequesters it into fibers, preventing mitochondrial outer-membrane permeabilization

Humanin induces conformational changes in the apoptosis regulator BAX and sequesters it into fibers, preventing mitochondrial outer-membrane permeabilization

  • J Biol Chem. 2019 Dec 13;294(50):19055-19065. doi: 10.1074/jbc.RA119.011297.
Daniel L Morris 1,  David W Kastner 1,  Sabrina Johnson 1,  Marie-Paule Strub 1 2,  Yi He 1 2,  Christopher K E Bleck 3,  Duck-Yeon Lee 4,  Nico Tjandra 5
Affiliations

Affiliations

  • 1 Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20814.
  • 2 Protein Expression Facility, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20814.
  • 3 Electron Microscopy Core Facility, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
  • 4 Biochemistry Core Facility, NHLBI, National Institutes of Health, Bethesda, Maryland 20814.
  • 5 Laboratory of Molecular Biophysics, Biochemistry and Biophysics Center, NHLBI, National Institutes of Health, Bethesda, Maryland 20814 tjandran@nhlbi.nih.gov.
PMID: 31690630 DOI: 10.1074/jbc.RA119.011297
Abstract

The mitochondrial, or intrinsic, Apoptosis pathway is regulated mainly by members of the B-cell lymphoma 2 (Bcl-2) protein family. BCL-2-associated X Apoptosis regulator (Bax) plays a pivotal role in the initiation of mitochondria-mediated Apoptosis as one of the factors causing mitochondrial outer-membrane permeabilization (MOMP). Of current interest are endogenous Bax ligands that inhibit its MOMP activity. Mitochondrial-derived Peptides (MDPs) are a recently identified class of mitochondrial retrograde signaling molecules and are reported to be potent Apoptosis inhibitors. Among them, humanin (HN) has been shown to suppress Apoptosis by inhibiting Bax translocation to the mitochondrial outer membrane, but the molecular mechanism of this interaction is unknown. Here, using recombinant protein expression, along with light-scattering, CD, and fluorescence spectroscopy, we report that HN and Bax can form fibers together in vitro Results from negative stain EM experiments suggest that Bax undergoes secondary and tertiary structural rearrangements and incorporates into the fibers, and that its membrane-associating C-terminal helix is important for the fibrillation process. Additionally, HN mutations known to alter its anti-apoptotic activity affect fiber morphology. Our findings reveal for the first time a potential mechanism by which Bax can be sequestered by fibril formation, which can prevent it from initiating MOMP and committing the cell to Apoptosis.

Keywords

B-cell lymphoma 2 (Bcl-2) family; BCL-2-associated X apoptosis regulator (BAX); Bax; apoptosis; conformational change; electron microscopy; fibers; fibril; fibrillation; humanin; mitochondrial apoptosis; protein aggregation; β-sheet.

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