Non-receptor tyrosine-protein kinase TYK2 is an enzyme that in humans is encoded by the TYK2gene.[1][2]
Tyk2 was the first member of the JAK family that was described (the other members are JAK1, JAK2, and JAK3).[3] It has been implicated in IFN-α, IL-6, IL-10 and IL-12 signaling.
This gene encodes a member of the tyrosine kinase and, to be more specific, the Janus kinases (JAKs) protein families. This protein associates with the cytoplasmic domain of type I and type II cytokine receptors and promulgate cytokine signals by phosphorylating receptor subunits. It is also component of both the type I and type III interferon signaling pathways. As such, it may play a role in anti-viral immunity.[2]
Cytokines play pivotal roles in immunity and inflammation by regulating the survival, proliferation, differentiation, and function of immune cells, as well as cells from other organ systems.[4] Hence, targeting cytokines and their receptors is an effective means of treating such disorders. Type I and II cytokine receptors associate with Janus family kinases (JAKs) to affect intracellular signaling. Cytokines including interleukins, interferons and hemopoietins activate the Janus kinases, which associate with their cognate receptors.[5]
The mammalian JAK family has four members: JAK1, JAK2, JAK3 and tyrosine kinase 2 (TYK2).[3] The connection between Jaks and cytokine signaling was first revealed when a screen for genes involved in interferon type I (IFN-1) signaling identified Tyk2 as an essential element, which is activated by an array of cytokine receptors.[6] Tyk2 has broader and profound functions in humans than previously appreciated on the basis of analysis of murine models, which indicate that Tyk2 functions primarily in IL-12 and type I-IFN signaling. Tyk2 deficiency has more dramatic effects in human cells than in mouse cells. However, in addition to IFN-α and -β and IL-12 signaling, Tyk2 has major effects on the transduction of IL-23, IL-10, and IL-6 signals. Since, IL-6 signals through the gp-130 receptor-chain that is common to a large family of cytokines, including IL-6, IL-11, IL-27, IL-31, oncostatin M (OSM), ciliary neurotrophic factor, cardiotrophin 1, cardiotrophin-like cytokine, and LIF, Tyk2 might also affect signaling through these cytokines. Recently, it has been recognized that IL-12 and IL-23 share ligand and receptor subunits that activate Tyk2. IL-10 is a critical anti-inflammatory cytokine, and IL-10−/− mice suffer from fatal, systemic autoimmune disease.
Tyk2 is activated by IL-10, and its deficiency affects the ability to generate and respond to IL-10.[7] Under physiological conditions, immune cells are, in general, regulated by the action of many cytokines and it has become clear that cross-talk between different cytokine-signalling pathways is involved in the regulation of the JAK–STAT pathway.[8]
Role in inflammation
It is now widely accepted that atherosclerosis is a result of cellular and molecular events characteristic of inflammation.[9] Vascular inflammation can be caused by upregulation of Ang-II, which is produced locally by inflamed vessels and induces synthesis and secretion of IL-6, a cytokine responsible for induction of angiotensinogen synthesis in liver through JAK/STAT3 pathway, which gets activated through high affinity membrane protein receptors on target cells, termed IL-6R-chain recruiting gp-130 that is associated with tyrosine kinases (Jaks 1/2, and Tyk2 kinase).[10] Cytokines IL-4 and IL-13 gets elevated in lungs of chronically suffered asthmatics. Signalling through IL-4/IL-13 complexes is thought to occur through IL-4Rα-chain, which is responsible for activation of JAK-1 and Tyk2 kinases.[11] A role of Tyk2 in rheumatoid arthritis is directly observed in Tyk2-deficient mice that were resistant to experimental arthritis.[12] Tyk2−/− mice displayed a lack of responsiveness to a small amount of IFN-α, but they respond normally to a high concentration of IFN-α/β.[8][13] In addition, these mice respond normally to IL-6 and IL-10, suggesting that Tyk2 is dispensable for mediating for IL-6 and IL-10 signaling and does not play a major role in IFN-α signaling. Although Tyk2−/− mice are phenotypically normal, they exhibit abnormal responses to inflammatory challenges in a variety of cells isolated from Tyk2−/− mice.[14] The most remarkable phenotype observed in Tyk2-deficient macrophages was lack of nitric oxide production upon stimulation with LPS. Further elucidation of molecular mechanisms of LPS signaling, showed that Tyk2 and IFN-β deficiency leads resistance to LPS-induced endotoxin shock, whereas STAT1-deficient mice are susceptible.[15] Development of a Tyk2 inhibitor appears to be a rational approach in the drug discovery.[16]
↑Krolewski JJ, Lee R, Eddy R, Shows TB, Dalla-Favera R (April 1990). "Identification and chromosomal mapping of new human tyrosine kinase genes". Oncogene. 5 (3): 277–82. PMID2156206.
↑Nicola, Nicos (1994). Guidebook to cytokines and their receptors. Oxford [Oxfordshire]: Oxford University Press. ISBN0-19-859947-1.
↑Kubo M, Hanada T, Yoshimura A (December 2003). "Suppressors of cytokine signaling and immunity". Nat. Immunol. 4 (12): 1169–76. doi:10.1038/ni1012. PMID14639467.
↑Velazquez L, Fellous M, Stark GR, Pellegrini S (July 1992). "A protein tyrosine kinase in the interferon alpha/beta signaling pathway". Cell. 70 (2): 313–22. doi:10.1016/0092-8674(92)90105-L. PMID1386289.
↑Brasier AR, Recinos A, Eledrisi MS (August 2002). "Vascular inflammation and the renin-angiotensin system". Arterioscler. Thromb. Vasc. Biol. 22 (8): 1257–66. doi:10.1161/01.ATV.0000021412.56621.A2. PMID12171785.
↑Wills-Karp M (July 2000). "Murine models of asthma in understanding immune dysregulation in human asthma". Immunopharmacology. 48 (3): 263–8. doi:10.1016/S0162-3109(00)00223-X. PMID10960667.
↑Karaghiosoff M, Steinborn R, Kovarik P, Kriegshäuser G, Baccarini M, Donabauer B, Reichart U, Kolbe T, Bogdan C, Leanderson T, Levy D, Decker T, Müller M (May 2003). "Central role for type I interferons and Tyk2 in lipopolysaccharide-induced endotoxin shock". Nat. Immunol. 4 (5): 471–7. doi:10.1038/ni910. PMID12679810.
↑Minegishi Y, Karasuyama H (December 2007). "Hyperimmunoglobulin E syndrome and tyrosine kinase 2 deficiency". Curr Opin Allergy Clin Immunol. 7 (6): 506–9. doi:10.1097/ACI.0b013e3282f1baea. PMID17989526.
↑Uddin, S; Sher D A; Alsayed Y; Pons S; Colamonici O R; Fish E N; White M F; Platanias L C (June 1997). "Interaction of p59fyn with interferon-activated Jak kinases". Biochem. Biophys. Res. Commun. United States. 235 (1): 83–8. doi:10.1006/bbrc.1997.6741. ISSN0006-291X. PMID9196040.
↑Yetter, A; Uddin S; Krolewski J J; Jiao H; Yi T; Platanias L C (August 1995). "Association of the interferon-dependent tyrosine kinase Tyk-2 with the hematopoietic cell phosphatase". J. Biol. Chem. United States. 270 (31): 18179–82. doi:10.1074/jbc.270.31.18179. ISSN0021-9258. PMID7629131.
↑Richter, M F; Duménil G; Uzé G; Fellous M; Pellegrini S (September 1998). "Specific contribution of Tyk2 JH regions to the binding and the expression of the interferon alpha/beta receptor component IFNAR1". J. Biol. Chem. United States. 273 (38): 24723–9. doi:10.1074/jbc.273.38.24723. ISSN0021-9258. PMID9733772.
↑Adam, L; Bandyopadhyay D; Kumar R (January 2000). "Interferon-alpha signaling promotes nucleus-to-cytoplasmic redistribution of p95Vav, and formation of a multisubunit complex involving Vav, Ku80, and Tyk2". Biochem. Biophys. Res. Commun. United States. 267 (3): 692–6. doi:10.1006/bbrc.1999.1978. ISSN0006-291X. PMID10673353.
↑Usacheva, Anna; Tian Xinyong; Sandoval Raudel; Salvi Debra; Levy David; Colamonici Oscar R (September 2003). "The WD motif-containing protein RACK-1 functions as a scaffold protein within the type I IFN receptor-signaling complex". J. Immunol. United States. 171 (6): 2989–94. doi:10.4049/jimmunol.171.6.2989. ISSN0022-1767. PMID12960323.
Further reading
Firmbach-Kraft I, Byers M, Shows T, et al. (1990). "tyk2, prototype of a novel class of non-receptor tyrosine kinase genes". Oncogene. 5 (9): 1329–36. PMID2216457.
Novak U, Harpur AG, Paradiso L, et al. (1995). "Colony-stimulating factor 1-induced STAT1 and STAT3 activation is accompanied by phosphorylation of Tyk2 in macrophages and Tyk2 and JAK1 in fibroblasts". Blood. 86 (8): 2948–56. PMID7579387.
Domanski P, Yan H, Witte MM, et al. (1995). "Homodimerization and intermolecular tyrosine phosphorylation of the Tyk-2 tyrosine kinase". FEBS Lett. 374 (3): 317–22. doi:10.1016/0014-5793(95)01094-U. PMID7589562.
Yetter A, Uddin S, Krolewski JJ, et al. (1995). "Association of the interferon-dependent tyrosine kinase Tyk-2 with the hematopoietic cell phosphatase". J. Biol. Chem. 270 (31): 18179–82. doi:10.1074/jbc.270.31.18179. PMID7629131.
Maruyama K, Sugano S (1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1–2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID8125298.
Trask B, Fertitta A, Christensen M, et al. (1993). "Fluorescence in situ hybridization mapping of human chromosome 19: cytogenetic band location of 540 cosmids and 70 genes or DNA markers". Genomics. 15 (1): 133–45. doi:10.1006/geno.1993.1021. PMID8432525.
Platanias LC, Uddin S, Yetter A, et al. (1996). "The type I interferon receptor mediates tyrosine phosphorylation of insulin receptor substrate 2". J. Biol. Chem. 271 (1): 278–82. doi:10.1074/jbc.271.1.278. PMID8550573.
Gauzzi MC, Velazquez L, McKendry R, et al. (1996). "Interferon-alpha-dependent activation of Tyk2 requires phosphorylation of positive regulatory tyrosines by another kinase". J. Biol. Chem. 271 (34): 20494–500. doi:10.1074/jbc.271.34.20494. PMID8702790.
Uddin S, Gardziola C, Dangat A, et al. (1996). "Interaction of the c-cbl proto-oncogene product with the Tyk-2 protein tyrosine kinase". Biochem. Biophys. Res. Commun. 225 (3): 833–8. doi:10.1006/bbrc.1996.1259. PMID8780698.
Zou J, Presky DH, Wu CY, Gubler U (1997). "Differential associations between the cytoplasmic regions of the interleukin-12 receptor subunits beta1 and beta2 and JAK kinases". J. Biol. Chem. 272 (9): 6073–7. doi:10.1074/jbc.272.9.6073. PMID9038232.
Miyakawa Y, Oda A, Druker BJ, et al. (1997). "Thrombopoietin and thrombin induce tyrosine phosphorylation of Vav in human blood platelets". Blood. 89 (8): 2789–98. PMID9108397.
Uddin S, Sher DA, Alsayed Y, et al. (1997). "Interaction of p59fyn with interferon-activated Jak kinases". Biochem. Biophys. Res. Commun. 235 (1): 83–8. doi:10.1006/bbrc.1997.6741. PMID9196040.
Burfoot MS, Rogers NC, Watling D, et al. (1997). "Janus kinase-dependent activation of insulin receptor substrate 1 in response to interleukin-4, oncostatin M, and the interferons". J. Biol. Chem. 272 (39): 24183–90. doi:10.1074/jbc.272.39.24183. PMID9305869.
Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, et al. (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID9373149.
Ahmad S, Alsayed YM, Druker BJ, Platanias LC (1997). "The type I interferon receptor mediates tyrosine phosphorylation of the CrkL adaptor protein". J. Biol. Chem. 272 (48): 29991–4. doi:10.1074/jbc.272.48.29991. PMID9374471.