5o6t

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]} [UBB_HUMAN] Ubiquitin exists either covalently attached to another protein, or free (unanchored). When covalently bound, it is conjugated to target proteins via an isopeptide bond either as a monomer (monoubiquitin), a polymer linked via different Lys residues of the ubiquitin (polyubiquitin chains) or a linear polymer linked via the initiator Met of the ubiquitin (linear polyubiquitin chains). Polyubiquitin chains, when attached to a target protein, have different functions depending on the Lys residue of the ubiquitin that is linked: Lys-6-linked may be involved in DNA repair; Lys-11-linked is involved in ERAD (endoplasmic reticulum-associated degradation) and in cell-cycle regulation; Lys-29-linked is involved in lysosomal degradation; Lys-33-linked is involved in kinase modification; Lys-48-linked is involved in protein degradation via the proteasome; Lys-63-linked is involved in endocytosis, DNA-damage responses as well as in signaling processes leading to activation of the transcription factor NF-kappa-B. Linear polymer chains formed via attachment by the initiator Met lead to cell signaling. Ubiquitin is usually conjugated to Lys residues of target proteins, however, in rare cases, conjugation to Cys or Ser residues has been observed. When polyubiquitin is free (unanchored-polyubiquitin), it also has distinct roles, such as in activation of protein kinases, and in signaling.^{[14] [15]}

References

1. ↑ Rigaud S, Fondaneche MC, Lambert N, Pasquier B, Mateo V, Soulas P, Galicier L, Le Deist F, Rieux-Laucat F, Revy P, Fischer A, de Saint Basile G, Latour S. XIAP deficiency in humans causes an X-linked lymphoproliferative syndrome. Nature. 2006 Nov 2;444(7115):110-4. PMID:17080092 doi:nature05257
2. ↑ Deveraux QL, Takahashi R, Salvesen GS, Reed JC. X-linked IAP is a direct inhibitor of cell-death proteases. Nature. 1997 Jul 17;388(6639):300-4. PMID:9230442 doi:10.1038/40901
3. ↑ Suzuki Y, Nakabayashi Y, Takahashi R. Ubiquitin-protein ligase activity of X-linked inhibitor of apoptosis protein promotes proteasomal degradation of caspase-3 and enhances its anti-apoptotic effect in Fas-induced cell death. Proc Natl Acad Sci U S A. 2001 Jul 17;98(15):8662-7. Epub 2001 Jul 10. PMID:11447297 doi:10.1073/pnas.161506698
4. ↑ MacFarlane M, Merrison W, Bratton SB, Cohen GM. Proteasome-mediated degradation of Smac during apoptosis: XIAP promotes Smac ubiquitination in vitro. J Biol Chem. 2002 Sep 27;277(39):36611-6. Epub 2002 Jul 16. PMID:12121969 doi:10.1074/jbc.M200317200
5. ↑ Burstein E, Ganesh L, Dick RD, van De Sluis B, Wilkinson JC, Klomp LW, Wijmenga C, Brewer GJ, Nabel GJ, Duckett CS. A novel role for XIAP in copper homeostasis through regulation of MURR1. EMBO J. 2004 Jan 14;23(1):244-54. Epub 2003 Dec 18. PMID:14685266 doi:10.1038/sj.emboj.7600031
6. ↑ Dan HC, Sun M, Kaneko S, Feldman RI, Nicosia SV, Wang HG, Tsang BK, Cheng JQ. Akt phosphorylation and stabilization of X-linked inhibitor of apoptosis protein (XIAP). J Biol Chem. 2004 Feb 13;279(7):5405-12. Epub 2003 Nov 25. PMID:14645242 doi:10.1074/jbc.M312044200
7. ↑ Wilkinson JC, Wilkinson AS, Galban S, Csomos RA, Duckett CS. Apoptosis-inducing factor is a target for ubiquitination through interaction with XIAP. Mol Cell Biol. 2008 Jan;28(1):237-47. Epub 2007 Oct 29. PMID:17967870 doi:MCB.01065-07
8. ↑ Van Themsche C, Leblanc V, Parent S, Asselin E. X-linked inhibitor of apoptosis protein (XIAP) regulates PTEN ubiquitination, content, and compartmentalization. J Biol Chem. 2009 Jul 31;284(31):20462-6. doi: 10.1074/jbc.C109.009522. Epub 2009, May 27. PMID:19473982 doi:10.1074/jbc.C109.009522
9. ↑ Broemer M, Tenev T, Rigbolt KT, Hempel S, Blagoev B, Silke J, Ditzel M, Meier P. Systematic in vivo RNAi analysis identifies IAPs as NEDD8-E3 ligases. Mol Cell. 2010 Dec 10;40(5):810-22. doi: 10.1016/j.molcel.2010.11.011. PMID:21145488 doi:10.1016/j.molcel.2010.11.011
10. ↑ Brady GF, Galban S, Liu X, Basrur V, Gitlin JD, Elenitoba-Johnson KS, Wilson TE, Duckett CS. Regulation of the copper chaperone CCS by XIAP-mediated ubiquitination. Mol Cell Biol. 2010 Apr;30(8):1923-36. doi: 10.1128/MCB.00900-09. Epub 2010 Feb, 12. PMID:20154138 doi:10.1128/MCB.00900-09
11. ↑ Lewis EM, Wilkinson AS, Davis NY, Horita DA, Wilkinson JC. Nondegradative ubiquitination of apoptosis inducing factor (AIF) by X-linked inhibitor of apoptosis at a residue critical for AIF-mediated chromatin degradation. Biochemistry. 2011 Dec 27;50(51):11084-96. doi: 10.1021/bi201483g. Epub 2011 Dec , 2. PMID:22103349 doi:10.1021/bi201483g
12. ↑ Hanson AJ, Wallace HA, Freeman TJ, Beauchamp RD, Lee LA, Lee E. XIAP monoubiquitylates Groucho/TLE to promote canonical Wnt signaling. Mol Cell. 2012 Mar 9;45(5):619-28. doi: 10.1016/j.molcel.2011.12.032. Epub 2012, Feb 1. PMID:22304967 doi:10.1016/j.molcel.2011.12.032
13. ↑ Lu M, Lin SC, Huang Y, Kang YJ, Rich R, Lo YC, Myszka D, Han J, Wu H. XIAP induces NF-kappaB activation via the BIR1/TAB1 interaction and BIR1 dimerization. Mol Cell. 2007 Jun 8;26(5):689-702. PMID:17560374 doi:http://dx.doi.org/10.1016/j.molcel.2007.05.006
14. ↑ Huang F, Kirkpatrick D, Jiang X, Gygi S, Sorkin A. Differential regulation of EGF receptor internalization and degradation by multiubiquitination within the kinase domain. Mol Cell. 2006 Mar 17;21(6):737-48. PMID:16543144 doi:S1097-2765(06)00120-1
15. ↑ Komander D. The emerging complexity of protein ubiquitination. Biochem Soc Trans. 2009 Oct;37(Pt 5):937-53. doi: 10.1042/BST0370937. PMID:19754430 doi:10.1042/BST0370937
16. ↑ Gabrielsen M, Buetow L, Nakasone MA, Ahmed SF, Sibbet GJ, Smith BO, Zhang W, Sidhu SS, Huang DT. A General Strategy for Discovery of Inhibitors and Activators of RING and U-box E3 Ligases with Ubiquitin Variants. Mol Cell. 2017 Oct 19;68(2):456-470.e10. doi: 10.1016/j.molcel.2017.09.027. PMID:29053960 doi:http://dx.doi.org/10.1016/j.molcel.2017.09.027