2. Academic Validation
  3. Bad is essential for Bcl-xL-enhanced Bax shuttling between mitochondria and cytosol

Bad is essential for Bcl-xL-enhanced Bax shuttling between mitochondria and cytosol

  • Int J Biochem Cell Biol. 2023 Feb;155:106359. doi: 10.1016/j.biocel.2022.106359.
Zihao Mai 1,  Han Sun 1,  Fangfang Yang 1,  Mengyan Du 1,  Xuecheng Cheng 1,  Hongce Chen 1,  Beini Sun 1,  Junlin Wen 2,  Xiaoping Wang 3,  Tongsheng Chen 4
Affiliations

Affiliations

  • 1 MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
  • 2 Department of Pain Management, the First Affiliated Hospital of Jinan University, Guangzhou 510632, China.
  • 3 Department of Pain Management, the First Affiliated Hospital of Jinan University, Guangzhou 510632, China. Electronic address: [email protected].
  • 4 MOE Key Laboratory of Laser Life Science & Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China. Electronic address: [email protected].
PMID: 36586532 DOI: 10.1016/j.biocel.2022.106359
Abstract

Although Bcl-xL has been shown to retrotranslocate Bax from mitochondria to cytosol, other studies have found that Bcl-xL also stabilizes the mitochondrial localization of Bax. It is still unclear what causes the difference in Bcl-xL-regulated Bax localization. Bad, a BH3-only protein with a high affinity for Bcl-xL, may play an important role in Bcl-xL-regulated Bax shuttling. Here, we found that Bcl-xL enhanced both translocalization and retrotranslocation of mitochondrial Bax, as evidenced by quantitative co-localization, western blots and fluorescence loss in photobleaching (FLIP) analyses. Notably, Bad knockdown prevented Bcl-xL-mediated Bax retrotranslocation, indicating Bad was essential for this process. Quantitative fluorescence resonance energy transfer (FRET) imaging in living cells and co-immunoprecipitation analyses showed that the interaction of Bcl-xL with Bad was stronger than that with Bax. The Bad mimetic ABT-737 dissociated Bax from Bcl-xL on isolated mitochondria, suggesting that mitochondrial Bax was directly liberated to cytosol due to Bad binding to Bcl-xL. In addition, MK-2206, an Akt Inhibitor, decreased Bad phosphorylation while increasing cytosolic Bax proportion. Our data firmly demonstrate a notion that Bad binds to mitochondrial Bcl-xL to release Bax, resulting in retrotranslocation of Bax to cytosol, and that the amount of Bad involved is regulated by Akt signaling.

Keywords

Akt; Bad; Bax; Bcl-xL; Retrotranslocation; Translocation.

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