Dataset Information

The Conformational Stability of Pro-apoptotic BAX is Dictated by Discrete Residues of the Protein Core

ABSTRACT: BAX is a pro-apoptotic member of the BCL-2 family, which regulates the balance between cellular life and death. During homeostasis, BAX predominantly resides in the cytosol as a latent monomer but, in response to stress, transforms into an oligomeric protein that permeabilizes the mitochondria, leading to cell death. Because renegade BAX activation poses a grave risk to the cell, the architecture of BAX must ensure monomeric stability yet simultaneously enable conformational change upon stress signaling. The specific structural features that afford both stability and dynamic flexibility remain ill-defined and represent a critical control point of BAX regulation. Here, we identified a nexus of interactions involving four discrete residues of the BAX core α5 helix that are individually essential to maintaining the structure and latency of monomeric BAX and are collectively required for dimeric assembly. We compared the HDX MS profile of full-length recombinant wild-type BAX in solution with that of the BAX L113A, F114A, Y115A, and F116A single point mutants. In each case, we observed striking, regiospecific consequences of replacing the bulky hydrophobic residue with alanine. We also compared HDX in a construct of α2-α5 for the wt protein as well as mutants. The dual yet distinct roles of these residues reveals the intricacy of BAX conformational regulation and opportunities for therapeutic modulation.

INSTRUMENT(S): Synapt MS

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: John R. Engen

LAB HEAD: John R. Engen

PROVIDER: PXD024479 | Pride | 2021-08-26

REPOSITORIES: Pride

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Publications

The conformational stability of pro-apoptotic BAX is dictated by discrete residues of the protein core.

Bloch Noah B NB Wales Thomas E TE Prew Michelle S MS Levy Hannah R HR Engen John R JR Walensky Loren D LD

Nature communications 20210813 1

BAX is a pro-apoptotic member of the BCL-2 family, which regulates the balance between cellular life and death. During homeostasis, BAX predominantly resides in the cytosol as a latent monomer but, in response to stress, transforms into an oligomeric protein that permeabilizes the mitochondria, leading to apoptosis. Because renegade BAX activation poses a grave risk to the cell, the architecture of BAX must ensure monomeric stability yet enable conformational change upon stress signaling. The sp ...[more]

PMID: 34389733

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Project description:Src family kinases are often overexpressed and constitutively active in cancer cells, where they represent promising targets for therapeutic intervention. In myeloid hematopoietic cells, Hck, Lyn, and Fgr are associated with both chronic and acute forms of myeloid leukemia. All three of these kinases are expressed in acute myeloid leukemia (AML), where high-level expression correlates with poor survival. The pyrrolopyrimidine Src-family kinase inhibitor A-419259 (also known as RK-20449) has been shown to significantly inhibit patient-derived AML bone marrow cell growth in immunocompromised mice. Recent work has identified an N-phenylbenzamide kinase inhibitor, known as TL02-59, which potently inhibited Fgr kinase activity in vitro and reversed orthotopic engraftment of AML cells in the bone marrow and spleen of immunocompromised mice following oral administration. The inhibitory mechanism of this compound with Fgr or other Src-family members has not been reported. Both wild-type Fgr and a tail mutant (i.e., replacement of Tyr527 with Phe) were shown to produce equal numbers of transformed colonies when expressed in rodent fibroblasts, whereas wild-type Hck transforming activity was completely repressed. In both Hck and Fgr, however, the tail tyrosine residue was shown to be phosphorylated, and hydrogen deuterium exchange mass spectrometry (HDX MS) of near-full-length Fgr was consistent with the closed conformation in solution, with the SH3 domain bound to the SH2-kinase linker and the tail bound to SH2. Here we present the first X-ray crystal structures of near-full-length Fgr bound to the ATP site inhibitors A-419259 and TL02-59. Structural changes induced by the inhibitors in the crystalline state were validated in solution using HDX MS, with A-419259 stabilizing the closed conformation and TL02-59 enhancing exposure of the SH3 domain to solvent. These new structures help to explain the constitutive activity of wild-type Fgr in cells as well as its unique sensitivity to TL02-59, which is currently in development for AML and other maladies.

Dataset Information

The Conformational Stability of Pro-apoptotic BAX is Dictated by Discrete Residues of the Protein Core

Publications

The conformational stability of pro-apoptotic BAX is dictated by discrete residues of the protein core.

Similar Datasets

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