2vsl | pdb_00002vsl
Crystal Structure of XIAP BIR3 with a Bivalent Smac Mimetic
Structural highlights
Disease[XIAP_HUMAN] Defects in XIAP are the cause of lymphoproliferative syndrome X-linked type 2 (XLP2) [MIM:300635]. XLP is a rare immunodeficiency characterized by extreme susceptibility to infection with Epstein-Barr virus (EBV). Symptoms include severe or fatal mononucleosis, acquired hypogammaglobulinemia, pancytopenia and malignant lymphoma.[1] Function[XIAP_HUMAN] Multi-functional protein which regulates not only caspases and apoptosis, but also modulates inflammatory signaling and immunity, copper homeostasis, mitogenic kinase signaling, cell proliferation, as well as cell invasion and metastasis. Acts as a direct caspase inhibitor. Directly bind to the active site pocket of CASP3 and CASP7 and obstructs substrate entry. Inactivates CASP9 by keeping it in a monomeric, inactive state. Acts as an E3 ubiquitin-protein ligase regulating NF-kappa-B signaling and the target proteins for its E3 ubiquitin-protein ligase activity include: RIPK1, CASP3, CASP7, CASP8, CASP9, MAP3K2/MEKK2, DIABLO/SMAC, AIFM1, CCS and BIRC5/survivin. Ubiquitinion of CCS leads to enhancement of its chaperone activity toward its physiologic target, SOD1, rather than proteasomal degradation. Ubiquitinion of MAP3K2/MEKK2 and AIFM1 does not lead to proteasomal degradation. Plays a role in copper homeostasis by ubiquitinationg COMMD1 and promoting its proteasomal degradation. Can also function as E3 ubiquitin-protein ligase of the NEDD8 conjugation pathway, targeting effector caspases for neddylation and inactivation. Regulates the BMP signaling pathway and the SMAD and MAP3K7/TAK1 dependent pathways leading to NF-kappa-B and JNK activation. Acts as an important regulator of innate immune signaling via regulation of Nodlike receptors (NLRs). Protects cells from spontaneous formation of the ripoptosome, a large multi-protein complex that has the capability to kill cancer cells in a caspase-dependent and caspase-independent manner. Suppresses ripoptosome formation by ubiquitinating RIPK1 and CASP8. Acts as a positive regulator of Wnt signaling and ubiquitinates TLE1, TLE2, TLE3, TLE4 and AES. Ubiquitination of TLE3 results in inhibition of its interaction with TCF7L2/TCF4 thereby allowing efficient recruitment and binding of the transcriptional coactivator beta-catenin to TCF7L2/TCF4 that is required to initiate a Wnt-specific transcriptional program.[2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedWe 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 50 values of 0.5 and 406 nM, respectively. Compound 3 binds to XIAPs containing the BIR3-only and BIR2-only domain with K i values of 4 nM and 4.4 muM, 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. Interaction of a Cyclic, Bivalent Smac Mimetic with the X-Linked Inhibitor of Apoptosis Protein.,Nikolovska-Coleska Z, Meagher JL, Jiang S, Yang CY, Qiu S, Roller PP, Stuckey JA, Wang S Biochemistry. 2008 Aug 22. PMID:18717598[14] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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