SMAC Negatively Regulates the Anti-apoptotic Activity of Melanoma Inhibitor of Apoptosis (ML-IAP)

• Published in: The Journal of biological chemistry Vol. 277; no. 14; pp. 12275 - 12279
• Main Authors: Vucic, Domagoj, Deshayes, Kurt, Ackerly, Heidi, Pisabarro, Maria Teresa, Kadkhodayan, Saloumeh, Fairbrother, Wayne J., Dixit, Vishva M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05-04-2002; American Society for Biochemistry and Molecular Biology
• Subjects: Adaptor Proteins, Signal Transducing; Amino Acid Sequence; Apoptosis; Carrier Proteins - metabolism; Caspase 9; Caspases - metabolism; Cell Line; Complement Membrane Attack Complex; Complement System Proteins; Dose-Response Relationship, Drug; Escherichia coli - metabolism; Glycoproteins - metabolism; Humans; Immunoblotting; Inhibitor of Apoptosis Proteins; Models, Molecular; Molecular Sequence Data; Mutation; Neoplasm Proteins - metabolism; Nucleosomes - metabolism; Peptides - chemistry; Plasmids - metabolism; Precipitin Tests; Protein Binding; Protein Conformation; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Time Factors; Transfection; Tumor Cells, Cultured
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112045200

Inhibitors of apoptosis (IAPs) physically interact with a variety of pro-apoptotic proteins and inhibit apoptosis induced by diverse stimuli. X-linked IAP (X-IAP) is a prototype IAP family member that inhibits several caspases, the effector proteases of apoptosis. The inhibitory activity of X-IAP is regulated by SMAC, a protein that is processed to its active form upon receipt of a death stimulus. Cleaved SMAC binds X-IAP and antagonizes its anti-apoptotic activity. Here we show that melanoma IAP (ML-IAP), a potent anti-cell death protein and caspase inhibitor, physically interacts with SMAC through its BIR (baculovirus IAP repeat) domain. In addition to binding full-length SMAC, ML-IAP BIR associates with SMAC peptides that are derived from the amino terminus of active, processed SMAC. This high affinity interaction is very specific and can be completely abolished by single amino acid mutations either in the amino terminus of active SMAC or in the BIR domain of ML-IAP. In cells expressing ML-IAP and X-IAP, SMAC coexpression or addition of SMAC peptides abrogates the ability of the IAPs to inhibit cell death. These results demonstrate the feasibility of using SMAC peptides as a way to sensitize IAP-expressing cells to pro-apoptotic stimuli such as chemotherapeutic agents.