Mcl-1 Interacts with Truncated Bid and Inhibits Its Induction of Cytochrome c Release and Its Role in Receptor-mediated Apoptosis

• Published in: The Journal of biological chemistry 2006-03, Vol.281 (9), p.5750-5759
• Main Authors: Clohessy, John G., Zhuang, Jianguo, de Boer, Jasper, Gil-Gómez, Gabriel, Brady, Hugh J.M.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Apoptosis Regulatory Proteins - metabolism; bcl-2 Homologous Antagonist-Killer Protein - genetics; bcl-2 Homologous Antagonist-Killer Protein - metabolism; bcl-2-Associated X Protein - genetics; bcl-2-Associated X Protein - metabolism; BH3 Interacting Domain Death Agonist Protein - genetics; BH3 Interacting Domain Death Agonist Protein - metabolism; Cytochromes c - metabolism; HeLa Cells; Humans; Membrane Glycoproteins - metabolism; Mice; Mutagenesis, Site-Directed; Myeloid Cell Leukemia Sequence 1 Protein; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; Protein Binding; Protein Structure, Tertiary; Proto-Oncogene Proteins c-bcl-2 - genetics; Proto-Oncogene Proteins c-bcl-2 - metabolism; RNA Interference; TNF-Related Apoptosis-Inducing Ligand; Tumor Necrosis Factor-alpha - metabolism; Two-Hybrid System Techniques
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M505688200

Engagement of death receptors such as tumor necrosis factor-R1 and Fas brings about the cleavage of cytosolic Bid to truncated Bid (tBid), which translocates to mitochondria to activate Bax/Bak, resulting in the release of cytochrome c. The mechanism underlying the activation, however, is not fully understood. Here, we have identified the anti-apoptotic Bcl-2 family member Mcl-1 as a potent tBid-binding partner. Site-directed mutagenesis reveals that the Bcl-2 homology (BH)3 domain of tBid is essential for binding to Mcl-1, whereas all three BH domains (BH1, BH2, and BH3) of Mcl-1 are required for interaction with tBid. In vitro studies using isolated mitochondria and recombinant proteins demonstrate that Mcl-1 strongly inhibits tBid-induced cytochrome c release. In addition to its ability to interact directly with Bax and Bak, tBid also binds Mcl-1 and displaces Bak from the Mcl-1-Bak complex. Importantly, overexpression of Mcl-1 confers resistance to the induction of apoptosis by both TRAIL and tumor necrosis factor-α in HeLa cells, whereas targeting Mcl-1 by RNA interference sensitizes HeLa cells to TRAIL-induced apoptosis. Therefore, our study demonstrates a novel regulation of tBid by Mcl-1 through protein-protein interaction in apoptotic signaling from death receptors to mitochondria.