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Antimycin A mimics a cell-death-inducing Bcl-2 homology domain 3
S P Tzung1, K M Kim, G Basañez
1Division of Gastroenterology, Department of Medicine, University of Washington, Seattle, Washington, 98195 USA.
Abstract:
The Bcl-2-related survival proteins confer cellular resistance to a wide range of agents. Bcl-xL-expressing hepatocyte cell lines are resistant to tumour necrosis factor and anti-cancer drugs, but are more sensitive than isogenic control cells to antimycin A, an inhibitor of mitochondrial electron transfer. Computational molecular docking analysis predicted that antimycin A interacts with the Bcl-2 homology domain 3 (BH3)-binding hydrophobic groove of Bcl-xL. We demonstrate that antimycin A and a Bak BH3 peptide bind competitively to recombinant Bcl-2. Antimycin A and BH3 peptide both induce mitochondrial swelling and loss of DeltaPsim on addition to mitochondria expressing Bcl-xL. The 2-methoxy derivative of antimycin A3 is inactive as an inhibitor of cellular respiration but still retains toxicity for Bcl-xL+ cells and mitochondria. Finally, antimycin A inhibits the pore-forming activity of Bcl-x L in synthetic liposomes, demonstrating that a small non-peptide ligand can directly inhibit the function of Bcl-2-related proteins.
Insights
The anti-cancer drug antimycin A targets Bcl-xL proteins, which are involved in cell survival. This study shows antimycin A can directly inhibit Bcl-xL function, offering new therapeutic strategies.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Bcl-2-related proteins regulate cell survival and resistance to various agents.
- Bcl-xL enhances resistance to tumor necrosis factor and chemotherapy but increases sensitivity to antimycin A.
Purpose of the Study:
- To investigate the interaction between antimycin A and Bcl-xL.
- To determine if antimycin A can directly inhibit Bcl-xL function.
Main Methods:
- Computational molecular docking to predict binding sites.
- Competitive binding assays with recombinant Bcl-2 and Bak BH3 peptide.
- Mitochondrial assays measuring swelling and membrane potential (DeltaPsim).
- Liposome-based assays to assess pore-forming activity.
Main Results:
- Antimycin A predicted to bind to the BH3-binding groove of Bcl-xL.
- Antimycin A and Bak BH3 peptide bind competitively to Bcl-2.
- Both antimycin A and BH3 peptide induce mitochondrial swelling and loss of DeltaPsim in Bcl-xL+ mitochondria.
- A non-respiratory inhibiting derivative of antimycin A3 retains toxicity for Bcl-xL+ cells and mitochondria.
- Antimycin A inhibits Bcl-xL pore-forming activity in synthetic liposomes.
Conclusions:
- Antimycin A directly interacts with and inhibits the function of Bcl-xL.
- Small molecule ligands can directly target and inhibit Bcl-2 family proteins.
- Findings suggest novel therapeutic approaches targeting Bcl-xL in cancer treatment.