3zni

Structural highlights

Disease

[ZAP70_HUMAN] Defects in ZAP70 are the cause of selective T-cell defect (STCD) [MIM:269840]. A form of severe combined immunodeficiency characterized by a selective absence of CD8+ T cells.^{[1] [2] [3] [4] [5]}

Function

[UBC_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.^{[6] [7]} [CBLB_HUMAN] E3 ubiquitin-protein ligase which accepts ubiquitin from specific E2 ubiquitin-conjugating enzymes, and transfers it to substrates, generally promoting their degradation by the proteasome. Negatively regulates TCR (T-cell receptor), BCR (B-cell receptor) and FCER1 (high affinity immunoglobulin epsilon receptor) signal transduction pathways. In naive T-cells, inhibits VAV1 activation upon TCR engagement and imposes a requirement for CD28 costimulation for proliferation and IL-2 production. Also acts by promoting PIK3R1/p85 ubiquitination, which impairs its recruitment to the TCR and subsequent activation. In activated T-cells, inhibits PLCG1 activation and calcium mobilization upon restimulation and promotes anergy. In B-cells, acts by ubiquitinating SYK and promoting its proteasomal degradation. May also be involved in EGFR ubiquitination and internalization.^{[8] [9] [10] [11]} [UB2D2_HUMAN] Accepts ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. In vitro catalyzes 'Lys-48'-linked polyubiquitination. Mediates the selective degradation of short-lived and abnormal proteins. Functions in the E6/E6-AP-induced ubiquitination of p53/TP53. Mediates ubiquitination of PEX5 and autoubiquitination of STUB1 and TRAF6. Involved in the signal-induced conjugation and subsequent degradation of NFKBIA, FBXW2-mediated GCM1 ubiquitination and degradation, MDM2-dependent degradation of p53/TP53 and the activation of MAVS in the mitochondria by DDX58/RIG-I in response to viral infection. Essential for viral activation of IRF3.^{[12] [13] [14] [15] [16] [17] [18] [19]} [ZAP70_HUMAN] Tyrosine kinase that plays an essential role in regulation of the adaptive immune response. Regulates motility, adhesion and cytokine expression of mature T-cells, as well as thymocyte development. Contributes also to the development and activation of primary B-lymphocytes. When antigen presenting cells (APC) activate T-cell receptor (TCR), a serie of phosphorylations lead to the recruitment of ZAP70 to the doubly phosphorylated TCR component CD247/CD3Z through ITAM motif at the plasma membrane. This recruitment serves to localization to the stimulated TCR and to relieve its autoinhibited conformation. Release of ZAP70 active conformation is further stabilized by phosphorylation mediated by LCK. Subsequently, ZAP70 phosphorylates at least 2 essential adapter proteins: LAT and LCP2. In turn, a large number of signaling molecules are recruited and ultimately lead to lymphokine production, T-cell proliferation and differentiation. Furthermore, ZAP70 controls cytoskeleton modifications, adhesion and mobility of T-lymphocytes, thus ensuring correct delivery of effectors to the APC. ZAP70 is also required for TCR-CD247/CD3Z internalization and degradation through interaction with the E3 ubiquitin-protein ligase CBL and adapter proteins SLA and SLA2. Thus, ZAP70 regulates both T-cell activation switch on and switch off by modulating TCR expression at the T-cell surface. During thymocyte development, ZAP70 promotes survival and cell-cycle progression of developing thymocytes before positive selection (when cells are still CD4/CD8 double negative). Additionally, ZAP70-dependent signaling pathway may also contribute to primary B-cells formation and activation through B-cell receptor (BCR).^{[20] [21] [22] [23] [24]}

See Also

• 3D structures of ubiquitin
• 3D structures of ubiquitin conjugating enzyme

References

1. ↑ Arpaia E, Shahar M, Dadi H, Cohen A, Roifman CM. Defective T cell receptor signaling and CD8+ thymic selection in humans lacking zap-70 kinase. Cell. 1994 Mar 11;76(5):947-58. PMID:8124727
2. ↑ Chan AC, Kadlecek TA, Elder ME, Filipovich AH, Kuo WL, Iwashima M, Parslow TG, Weiss A. ZAP-70 deficiency in an autosomal recessive form of severe combined immunodeficiency. Science. 1994 Jun 10;264(5165):1599-601. PMID:8202713
3. ↑ Toyabe S, Watanabe A, Harada W, Karasawa T, Uchiyama M. Specific immunoglobulin E responses in ZAP-70-deficient patients are mediated by Syk-dependent T-cell receptor signalling. Immunology. 2001 Jun;103(2):164-71. PMID:11412303
4. ↑ Elder ME, Skoda-Smith S, Kadlecek TA, Wang F, Wu J, Weiss A. Distinct T cell developmental consequences in humans and mice expressing identical mutations in the DLAARN motif of ZAP-70. J Immunol. 2001 Jan 1;166(1):656-61. PMID:11123350
5. ↑ Turul T, Tezcan I, Artac H, de Bruin-Versteeg S, Barendregt BH, Reisli I, Sanal O, van Dongen JJ, van der Burg M. Clinical heterogeneity can hamper the diagnosis of patients with ZAP70 deficiency. Eur J Pediatr. 2009 Jan;168(1):87-93. doi: 10.1007/s00431-008-0718-x. Epub 2008, May 29. PMID:18509675 doi:10.1007/s00431-008-0718-x
6. ↑ 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
7. ↑ 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
8. ↑ Elly C, Witte S, Zhang Z, Rosnet O, Lipkowitz S, Altman A, Liu YC. Tyrosine phosphorylation and complex formation of Cbl-b upon T cell receptor stimulation. Oncogene. 1999 Feb 4;18(5):1147-56. PMID:10022120 doi:10.1038/sj.onc.1202411
9. ↑ Ettenberg SA, Keane MM, Nau MM, Frankel M, Wang LM, Pierce JH, Lipkowitz S. cbl-b inhibits epidermal growth factor receptor signaling. Oncogene. 1999 Mar 11;18(10):1855-66. PMID:10086340 doi:10.1038/sj.onc.1202499
10. ↑ Fang D, Wang HY, Fang N, Altman Y, Elly C, Liu YC. Cbl-b, a RING-type E3 ubiquitin ligase, targets phosphatidylinositol 3-kinase for ubiquitination in T cells. J Biol Chem. 2001 Feb 16;276(7):4872-8. Epub 2000 Nov 21. PMID:11087752 doi:10.1074/jbc.M008901200
11. ↑ Fang D, Liu YC. Proteolysis-independent regulation of PI3K by Cbl-b-mediated ubiquitination in T cells. Nat Immunol. 2001 Sep;2(9):870-5. PMID:11526404 doi:10.1038/ni0901-870
12. ↑ Gonen H, Bercovich B, Orian A, Carrano A, Takizawa C, Yamanaka K, Pagano M, Iwai K, Ciechanover A. Identification of the ubiquitin carrier proteins, E2s, involved in signal-induced conjugation and subsequent degradation of IkappaBalpha. J Biol Chem. 1999 May 21;274(21):14823-30. PMID:10329681
13. ↑ Saville MK, Sparks A, Xirodimas DP, Wardrop J, Stevenson LF, Bourdon JC, Woods YL, Lane DP. Regulation of p53 by the ubiquitin-conjugating enzymes UbcH5B/C in vivo. J Biol Chem. 2004 Oct 1;279(40):42169-81. Epub 2004 Jul 26. PMID:15280377 doi:10.1074/jbc.M403362200
14. ↑ Windheim M, Peggie M, Cohen P. Two different classes of E2 ubiquitin-conjugating enzymes are required for the mono-ubiquitination of proteins and elongation by polyubiquitin chains with a specific topology. Biochem J. 2008 Feb 1;409(3):723-9. PMID:18042044 doi:10.1042/BJ20071338
15. ↑ Chiang MH, Chen LF, Chen H. Ubiquitin-conjugating enzyme UBE2D2 is responsible for FBXW2 (F-box and WD repeat domain containing 2)-mediated human GCM1 (glial cell missing homolog 1) ubiquitination and degradation. Biol Reprod. 2008 Nov;79(5):914-20. doi: 10.1095/biolreprod.108.071407. Epub 2008, Aug 13. PMID:18703417 doi:10.1095/biolreprod.108.071407
16. ↑ Grou CP, Carvalho AF, Pinto MP, Wiese S, Piechura H, Meyer HE, Warscheid B, Sa-Miranda C, Azevedo JE. Members of the E2D (UbcH5) family mediate the ubiquitination of the conserved cysteine of Pex5p, the peroxisomal import receptor. J Biol Chem. 2008 May 23;283(21):14190-7. doi: 10.1074/jbc.M800402200. Epub 2008 , Mar 22. PMID:18359941 doi:10.1074/jbc.M800402200
17. ↑ Zeng W, Xu M, Liu S, Sun L, Chen ZJ. Key role of Ubc5 and lysine-63 polyubiquitination in viral activation of IRF3. Mol Cell. 2009 Oct 23;36(2):315-25. doi: 10.1016/j.molcel.2009.09.037. PMID:19854139 doi:10.1016/j.molcel.2009.09.037
18. ↑ Zeng W, Sun L, Jiang X, Chen X, Hou F, Adhikari A, Xu M, Chen ZJ. Reconstitution of the RIG-I pathway reveals a signaling role of unanchored polyubiquitin chains in innate immunity. Cell. 2010 Apr 16;141(2):315-30. doi: 10.1016/j.cell.2010.03.029. PMID:20403326 doi:10.1016/j.cell.2010.03.029
19. ↑ David Y, Ziv T, Admon A, Navon A. The E2 ubiquitin conjugating enzymes direct polyubiquitination to preferred lysines. J Biol Chem. 2010 Jan 8. PMID:20061386 doi:M109.089003
20. ↑ Chan AC, Iwashima M, Turck CW, Weiss A. ZAP-70: a 70 kd protein-tyrosine kinase that associates with the TCR zeta chain. Cell. 1992 Nov 13;71(4):649-62. PMID:1423621
21. ↑ Arpaia E, Shahar M, Dadi H, Cohen A, Roifman CM. Defective T cell receptor signaling and CD8+ thymic selection in humans lacking zap-70 kinase. Cell. 1994 Mar 11;76(5):947-58. PMID:8124727
22. ↑ Bubeck Wardenburg J, Fu C, Jackman JK, Flotow H, Wilkinson SE, Williams DH, Johnson R, Kong G, Chan AC, Findell PR. Phosphorylation of SLP-76 by the ZAP-70 protein-tyrosine kinase is required for T-cell receptor function. J Biol Chem. 1996 Aug 16;271(33):19641-4. PMID:8702662
23. ↑ Zhang W, Sloan-Lancaster J, Kitchen J, Trible RP, Samelson LE. LAT: the ZAP-70 tyrosine kinase substrate that links T cell receptor to cellular activation. Cell. 1998 Jan 9;92(1):83-92. PMID:9489702
24. ↑ Wang HY, Altman Y, Fang D, Elly C, Dai Y, Shao Y, Liu YC. Cbl promotes ubiquitination of the T cell receptor zeta through an adaptor function of Zap-70. J Biol Chem. 2001 Jul 13;276(28):26004-11. Epub 2001 May 15. PMID:11353765 doi:10.1074/jbc.M010738200
25. ↑ Dou H, Buetow L, Sibbet GJ, Cameron K, Huang DT. Essentiality of a non-RING element in priming donor ubiquitin for catalysis by a monomeric E3. Nat Struct Mol Biol. 2013 Jul 14. doi: 10.1038/nsmb.2621. PMID:23851457 doi:10.1038/nsmb.2621