Open AccessThe multidomain proapoptotic molecules Bax and Bak are directly activated by heat
Author(s) -
Lisa J. Pagliari,
Tomomi Kuwana,
Christine Bonzon,
Donald D. Newmeyer,
S. Sean Tu,
Helen M. Beere,
Douglas R. Green
Publication year - 2005
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0506712102
Subject(s) - cytochrome c , cytosol , mitochondrion , mitochondrial apoptosis induced channel , microbiology and biotechnology , bcl 2 family , apoptosis , apoptosome , biology , cytochrome , inner mitochondrial membrane , bcl 2 associated x protein , intermembrane space , chemistry , programmed cell death , bacterial outer membrane , biochemistry , caspase , caspase 3 , escherichia coli , gene , enzyme
During apoptosis, engagement of the mitochondrial pathway involves a decisive event characterized by the release of mitochondrial intermembrane space proteins, such as cytochromec . This permeabilization of the mitochondrial outer membrane depends on activation and oligomerization of multidomain Bcl-2-family proteins Bax or Bak. Although specific members of the Bcl-2 family can activate these proapoptotic proteins, we found that heat directly activated Bax or Bak to induce cytochromec release. A preparation of mitochondria heated at 43°C released cytochromec in association with Bak oligomerization, and Bcl-xL prevented these events. Similarly, heat induced the oligomerization of recombinant Bax, conferring an ability to permeabilize mitochondria. Compared with wild-type cells,bax –/– bak –/– mouse embryonic fibroblasts and mitochondria isolated from these cells were resistant to heat-induced cytochromec release. Cytosol from untreated cells inhibited heat-activated Bax or Bak; however, depletion of cytosolic Bcl-xL ablated this protection. Although mitochondria heated in the presence of cytosol did not release cytochromec , they displayed a dramatic increase in sensitivity to permeabilization by the BH3-only protein Bid. Additionally, a peptide corresponding to the BH3 domain of Puma counteracted the inhibitory effect of cytosol and permitted heat-activated Bak to permeabilize the mitochondria. Therefore, heat represents a condition under which multidomain proapoptotic proteins are activated, and this activation is regulated by both antiapoptotic and BH3-only members of the Bcl-2 family. Our results support an emerging paradigm, wherein the activation of Bax or Bak and the blockade of antiapoptotic Bcl-2 proteins are pivotal steps in the mitochondrial pathway of apoptosis.