Interaction of a Cyclic, Bivalent Smac Mimetic with the X-Linked Inhibitor of Apoptosis Protein

Journal Article · Wed Feb 25 04:00:00 EST 2009 · Biochemistry-US

DOI:https://doi.org/10.1021/bi800785y· OSTI ID:1006992

Nikolovska-Coleska, Zaneta; Meagher, Jennifer L; Jiang, Sheng; Yang, Chao-Yie; Qiu, Su; Roller, Peter P; Stuckey, Jeanne A; Wang, Shaomeng ^[1]

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1. Michigan

We have designed and synthesized a cyclic, bivalent Smac mimetic (compound 3) and characterized its interaction with the X-linked inhibitor of apoptosis protein (XIAP). Compound 3 binds to XIAP containing both BIR2 and BIR3 domains with a biphasic dose-response curve representing two binding sites with IC{sub 50} values of 0.5 and 406 nM, respectively. Compound 3 binds to XIAPs containing the BIR3-only and BIR2-only domain with K{sub i} values of 4 nM and 4.4 {mu}M, respectively. Gel filtration experiments using wild-type and mutated XIAPs showed that 3 forms a 1:2 stoichiometric complex with XIAP containing the BIR3-only domain. However, it forms a 1:1 stoichiometric complex with XIAP containing both BIR2 and BIR3 domains, and both BIR domains are involved in the binding. Compound 3 efficiently antagonizes inhibition of XIAP in a cell-free functional assay and is >200 times more potent than its corresponding monovalent compound 2. Determination of the crystal structure of 3 in complex with the XIAP BIR3 domain confirms that 3 induces homodimerization of the XIAP BIR3 domain and provides a structural basis for the cooperative binding of one molecule of compound 3 to two XIAP BIR3 molecules. On the basis of this crystal structure, a binding model of XIAP containing both BIR2 and BIR3 domains and 3 was constructed, which sheds light on the ability of 3 to relieve the inhibition of XIAP with not only caspase-9 but also caspase-3/-7. Compound 3 is cell-permeable, effectively activates caspases in whole cells, and potently inhibits cancer cell growth. Compound 3 is a useful biochemical and pharmacological tool for further elucidating the role of XIAP in regulation of apoptosis and represents a promising lead compound for the design of potent, cell-permeable Smac mimetics for cancer treatment.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: USDOE
• OSTI ID: 1006992
• Journal Information: Biochemistry-US, Journal Name: Biochemistry-US Journal Issue: (37) ; 2008 Vol. 47; ISSN 0006-2960; ISSN BICHAW
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
APOPTOSIS
CRYSTAL STRUCTURE
DESIGN
DIAGRAMS
FILTRATION
FUNCTIONALS
GELS
GROWTH
INHIBITION
INTERACTIONS
MOLECULES
NEOPLASMS
PROTEINS