Translocation of a Bak C-Terminus Mutant from Cytosol to Mitochondria to Mediate Cytochrome c Release: Implications for Bak and Bax Apoptotic Function
- Author(s)
- Ferrer, PE; Frederick, P; Gulbis, JM; Dewson, G; Kluck, RM;
- Details
- Publication Year 2012-03-19,Volume 7,Issue #3,Page e31510
- Journal Title
- PLOS ONE
- Publication Type
- Journal Article
- Abstract
- Background: One of two proapoptotic Bcl-2 proteins, Bak or Bax, is required to permeabilize the mitochondrial outer membrane during apoptosis. While Bax is mostly cytosolic and translocates to mitochondria following an apoptotic stimulus, Bak is constitutively integrated within the outer membrane. Membrane anchorage occurs via a C-terminal transmembrane domain that has been studied in Bax but not in Bak, therefore what governs their distinct subcellular distribution is uncertain. In addition, whether the distinct subcellular distributions of Bak and Bax contributes to their differential regulation during apoptosis remains unclear. Methodology/Principal Findings: To gain insight into Bak and Bax targeting to mitochondria, elements of the Bak C-terminus were mutated, or swapped with those of Bax. Truncation of the C-terminal six residues (C-segment) or substitution of three basic residues within the C-segment destabilized Bak. Replacing the Bak C-segment with that from Bax rescued stability and function, but unexpectedly resulted in a semi-cytosolic protein, termed Bak/BaxCS. When in the cytosol, both Bax and Bak/BaxCS sequestered their hydrophobic transmembrane domains in their hydrophobic surface groove. Upon apoptotic signalling, Bak/BaxCS translocated to the mitochondrial outer membrane, inserted its transmembrane domain, oligomerized, and released cytochrome c. Despite this Bax-like subcellular distribution, Bak/BaxCS retained Bak-like regulation following targeting of Mcl-1. Conclusions/Significance: Residues in the C-segment of Bak and of Bax contribute to their distinct subcellular localizations. That a semi-cytosolic form of Bak, Bak/BaxCS, could translocate to mitochondria and release cytochrome c indicates that Bak and Bax share a conserved mode of activation. In addition, the differential regulation of Bak and Bax by Mcl-1 is predominantly independent of the initial subcellular localizations of Bak and Bax.
- Publisher
- PUBLIC LIBRARY SCIENCE
- Keywords
- PROSURVIVAL BCL-2 PROTEINS; TAIL-ANCHORED PROTEINS; BH3-ONLY PROTEINS; OUTER-MEMBRANE; BH3 DOMAINS; CELL-DEATH; OLIGOMERIZATION; ACTIVATION; INSERTION; LOCALIZATION
- Research Division(s)
- Structural Biology; Cell Signalling And Cell Death; Molecular Genetics Of Cancer
- Publisher's Version
- https://doi.org/10.1371/journal.pone.0031510
- Open Access at Publisher's Site
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3307716/- Terms of Use/Rights Notice
- Copyright: ß 2012 Ferrer et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Creation Date: 2012-03-19 12:00:00