IL-22 is an α-helical cytokine. IL-22 binds to a heterodimeric cell surface receptor composed of IL-10R2 and IL-22R1 subunits.[3] IL-22R is expressed on tissue cells, and it is absent on immune cells.[4]
Crystallization is possible if the N-linked glycosylation sites are removed in mutants of IL-22 bound with high-affinity cell-surface receptor sIL-22R1. The crystallographic asymmetric unit contained two IL-22-sIL-22R1 complexes.[3]
Function
IL-22 a member of a group of cytokines called the IL-10 family or IL-10 superfamily (including IL-19, IL-20, IL-24, and IL-26),[5] a class of potent mediators of cellular inflammatory responses. It shares use of IL-10R2 in cell signaling with other members of this family, IL-10, IL-26, IL-28A/B and IL-29.[6] IL-22 is produced by activated NK and T cells and initiates innate immune responses against bacterial pathogens especially in epithelial cells such as respiratory and gut epithelial cells. IL-22 along with IL-17 is rapidly produced by splenic LTi-like cells [7] and also produced by Th17 cells and likely plays a role in the coordinated response of both adaptive innate immune systems, autoimmunity and tissue regeneration.[8]
IL-22 biological activity is initiated by binding to a cell-surface complex composed of IL-22R1 and IL-10R2 receptor chains and further regulated by interactions with a soluble binding protein, IL-22BP, which shares sequence similarity with an extracellular region of IL-22R1 (sIL-22R1). IL-22 and IL-10 receptor chains play a role in cellular targeting and signal transduction to selectively initiate and regulate immune responses.[3] IL-22 can contribute to immune disease through the stimulation of inflammatory responses, S100s and defensins. IL-22 also promotes hepatocyte survival in the liver and epithelial cells in the lung and gut similar to IL-10.[9] In some contexts, the pro-inflammatory versus tissue-protective functions of IL-22 are regulated by the often co-expressed cytokine IL-17A [10]
IL-22, signals through the interferon receptor-related proteins CRF2-4 and IL-22R.[2] It forms cell surface complexes with IL-22R1 and IL-10R2 chains resulting in signal transduction through receptor, IL-10R2. The IL-22/IL-22R1/IL-10R2 complex activates intracellular kinases (JAK1, Tyk2, and MAP kinases) and transcription factors, especially STAT3. It can induce IL-20 and IL-24 signaling when IL-22R1 pairs with IL-20R2.
↑ 2.02.1Xie MH, Aggarwal S, Ho WH, Foster J, Zhang Z, Stinson J, Wood WI, Goddard AD, Gurney AL (Oct 2000). "Interleukin (IL)-22, a novel human cytokine that signals through the interferon receptor-related proteins CRF2-4 and IL-22R". The Journal of Biological Chemistry. 275 (40): 31335–9. doi:10.1074/jbc.M005304200. PMID10875937.
↑Wolk K, Kunz S, Witte E, Friedrich M, Asadullah K, Sabat R (Aug 2004). "IL-22 increases the innate immunity of tissues". Immunity. 21 (2): 241–54. doi:10.1016/j.immuni.2004.07.007. PMID15308104.
↑Moore KW, de Waal Malefyt R, Coffman RL, O'Garra A (2001). "Interleukin-10 and the interleukin-10 receptor". Annual Review of Immunology. 19: 683–765. doi:10.1146/annurev.immunol.19.1.683. PMID11244051..
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Wong CK, Lun SW, Ko FW, Wong PT, Hu SQ, Chan IH, Hui DS, Lam CW (2009). "Activation of peripheral Th17 lymphocytes in patients with asthma". Immunological Investigations. 38 (7): 652–64. doi:10.1080/08820130903062756. PMID19811428.
Shen H, Goodall JC, Hill Gaston JS (Jun 2009). "Frequency and phenotype of peripheral blood Th17 cells in ankylosing spondylitis and rheumatoid arthritis". Arthritis and Rheumatism. 60 (6): 1647–56. doi:10.1002/art.24568. PMID19479869.
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Pan HF, Zhao XF, Yuan H, Zhang WH, Li XP, Wang GH, Wu GC, Tang XW, Li WX, Li LH, Feng JB, Hu CS, Ye DQ (Mar 2009). "Decreased serum IL-22 levels in patients with systemic lupus erythematosus". Clinica Chimica Acta; International Journal of Clinical Chemistry. 401 (1–2): 179–80. doi:10.1016/j.cca.2008.11.009. PMID19046958.
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Dhiman R, Indramohan M, Barnes PF, Nayak RC, Paidipally P, Rao LV, Vankayalapati R (Nov 2009). "IL-22 produced by human NK cells inhibits growth of Mycobacterium tuberculosis by enhancing phagolysosomal fusion". Journal of Immunology. 183 (10): 6639–45. doi:10.4049/jimmunol.0902587. PMID19864591.