The autoimmune regulator (AIRE) is a protein that in humans is encoded by the AIREgene.[1] AIRE is a transcription factor expressed in the medulla (inner part) of the thymus. It is part of the mechanism which eliminates self-reactive T cells that would cause autoimmune disease. It exposes T cells to normal, healthy proteins from all parts of the body, and T cells that react to those proteins are destroyed.
Each T cell recognizes a specific antigen when it is presented in complex with a MHC molecule by an antigen presenting cell. This recognition is accomplished by the T cell receptors expressed on the cell surface. T cells receptors are generated by randomly shuffled gene segments which results in a highly diverse population of T cells - each with a unique antigen specificity. Subsequently, T cells with receptors that recognize the body's own proteins need to be eliminated while still in the thymus. Through the action of AIRE, medullary thymic epithelial cells (mTEC) express major proteins from elsewhere in the body (so called "tissue-restricted antigens" - TRA) and T cells that respond to those proteins are eliminated through cell death (apoptosis). Thus AIRE drives negative selection of self-recognizing T cells.[2] When AIRE is defective, T cells that recognize antigens normally produced by the body can exit the thymus and enter circulation. This can result in a variety of autoimmune diseases.
In the thymus, the AIRE causes transcription of a wide selection of organ-specific genes that create proteins that are usually only expressed in peripheral tissues, creating an "immunological self-shadow" in the thymus.[3][4] It is important that self-reactive T cells that bind strongly to self-antigen are eliminated in the thymus (via the process of negative selection), otherwise they may later encounter and bind to their corresponding self-antigens and initiate an autoimmune reaction. So the expression of non-local proteins by AIRE in the thymus reduces the threat of autoimmunity by promoting the elimination of auto-reactive T cells that bind antigens not normally found in the thymus. Furthermore, it has been found that AIRE is expressed in a population of stromal cells located in secondary lymphoid tissues, however these cells appear to express a distinct set of TRAs compared to mTECs[5]
Research in knockout mice has demonstrated that AIRE functions through initiating the transcription of a diverse set of self-antigens, such as insulin, in the thymus.[3] This expression then allows maturing thymocytes to become tolerant towards peripheral organs, thereby suppressing autoimmune disease.[4]
The AIRE gene is expressed in many other tissues as well.[6] AIRE gene is also expressed in the 33D1+ subset of dendritic cells in mouse and in human dendritic cells.[7]
Pathology
The AIRE gene is mutated in the rare autoimmune syndrome Autoimmune Polyendocrinopathy Syndrome type 1 (APS-1), also known as Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy (APECED). Disruption of AIRE results in the development of a range of autoimmune diseases, the most common clinical conditions in the syndrome are hypoparathyroidism, primary adrenocortical failure and chronic mucocutaneous candidiasis.[8]
↑"An autoimmune disease, APECED, caused by mutations in a novel gene featuring two PHD-type zinc-finger domains". Nat. Genet. 17 (4): 399–403. December 1997. doi:10.1038/ng1297-399. PMID9398840.
↑ 3.03.1Anderson MS, Venanzi ES, Klein L, Chen Z, Berzins SP, Turley SJ, von Boehmer H, Bronson R, Dierich A, Benoist C, Mathis D (November 2002). "Projection of an immunological self shadow within the thymus by the aire protein". Science. 298 (5597): 1395–401. doi:10.1126/science.1075958. PMID12376594.
↑ 4.04.1Liston A, Lesage S, Wilson J, Peltonen L, Goodnow CC (April 2003). "Aire regulates negative selection of organ-specific T cells". Nat. Immunol. 4 (4): 350–4. doi:10.1038/ni906. PMID12612579.
↑Ramsey C, Winqvist O, Puhakka L, Halonen M, Moro A, Kämpe O, Eskelin P, Pelto-Huikko M, Peltonen L (2002). "Aire deficient mice develop multiple features of APECED phenotype and show altered immune response". Hum. Mol. Genet. 11 (4): 397–409. doi:10.1093/hmg/11.4.397. PMID11854172.
↑Pitkänen J, Doucas V, Sternsdorf T, Nakajima T, Aratani S, Jensen K, Will H, Vähämurto P, Ollila J, Vihinen M, Scott HS, Antonarakis SE, Kudoh J, Shimizu N, Krohn K, Peterson P (June 2000). "The autoimmune regulator protein has transcriptional transactivating properties and interacts with the common coactivator CREB-binding protein". J. Biol. Chem. 275 (22): 16802–9. doi:10.1074/jbc.M908944199. PMID10748110.
↑Iioka T, Furukawa K, Yamaguchi A, Shindo H, Yamashita S, Tsukazaki T (August 2003). "P300/CBP acts as a coactivator to cartilage homeoprotein-1 (Cart1), paired-like homeoprotein, through acetylation of the conserved lysine residue adjacent to the homeodomain". J. Bone Miner. Res. 18 (8): 1419–29. doi:10.1359/jbmr.2003.18.8.1419. PMID12929931.
Further reading
Björses P, Aaltonen J, Horelli-Kuitunen N, et al. (1998). "Gene defect behind APECED: a new clue to autoimmunity". Hum. Mol. Genet. 7 (10): 1547–53. doi:10.1093/hmg/7.10.1547. PMID9735375.
Heino M, Peterson P, Kudoh J, Shimizu N, Antonarakis SE, Scott HS, Krohn K (September 2001). "APECED mutations in the autoimmune regulator (AIRE) gene". Hum. Mutat. 18 (3): 205–11. doi:10.1002/humu.1176. PMID11524731.
Sato K, Nakajima K, Imamura H, Deguchi T, Horinouchi S, Yamazaki K, Yamada E, Kanaji Y, Takano K (December 2002). "A novel missense mutation of AIRE gene in a patient with autoimmune polyendocrinopathy, candidiasis and ectodermal dystrophy (APECED), accompanied with progressive muscular atrophy: case report and review of the literature in Japan". Endocr. J. 49 (6): 625–33. doi:10.1507/endocrj.49.625. PMID12625412.
Ruan QG, She JX (March 2004). "Autoimmune polyglandular syndrome type 1 and the autoimmune regulator". Clin. Lab. Med. 24 (1): 305–17. doi:10.1016/j.cll.2004.01.008. PMID15157567.
Holmdahl R (March 2007). "Aire-ing self antigen variability and tolerance". Eur. J. Immunol. 37 (3): 598–601. doi:10.1002/eji.200737152. PMID17323409.
Aaltonen J, Björses P, Sandkuijl L, Perheentupa J, Peltonen L (September 1994). "An autosomal locus causing autoimmune disease: autoimmune polyglandular disease type I assigned to chromosome 21". Nat. Genet. 8 (1): 83–7. doi:10.1038/ng0994-83. PMID7987397.
Aaltonen J, Horelli-Kuitunen N, Fan JB, Björses P, Perheentupa J, Myers R, Palotie A, Peltonen L (August 1997). "High-resolution physical and transcriptional mapping of the autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy locus on chromosome 21q22.3 by FISH". Genome Res. 7 (8): 820–9. doi:10.1101/gr.7.8.820. PMID9267805.
Nagamine K, Peterson P, Scott HS, Kudoh J, Minoshima S, Heino M, Krohn KJ, Lalioti MD, Mullis PE, Antonarakis SE, Kawasaki K, Asakawa S, Ito F, Shimizu N (December 1997). "Positional cloning of the APECED gene". Nat. Genet. 17 (4): 393–8. doi:10.1038/ng1297-393. PMID9398839.
Scott HS, Heino M, Peterson P, Mittaz L, Lalioti MD, Betterle C, Cohen A, Seri M, Lerone M, Romeo G, Collin P, Salo M, Metcalfe R, Weetman A, Papasavvas MP, Rossier C, Nagamine K, Kudoh J, Shimizu N, Krohn KJ, Antonarakis SE (August 1998). "Common mutations in autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy patients of different origins". Mol. Endocrinol. 12 (8): 1112–9. doi:10.1210/me.12.8.1112. PMID9717837.
Heino M, Scott HS, Chen Q, Peterson P, Mäebpää U, Papasavvas MP, Mittaz L, Barras C, Rossier C, Chrousos GP, Stratakis CA, Nagamine K, Kudoh J, Shimizu N, Maclaren N, Antonarakis SE, Krohn K (1999). "Mutation analyses of North American APS-1 patients". Hum. Mutat. 13 (1): 69–74. doi:10.1002/(SICI)1098-1004(1999)13:1<69::AID-HUMU8>3.0.CO;2-6. PMID9888391.
Björses P, Pelto-Huikko M, Kaukonen J, Aaltonen J, Peltonen L, Ulmanen I (February 1999). "Localization of the APECED protein in distinct nuclear structures". Hum. Mol. Genet. 8 (2): 259–66. doi:10.1093/hmg/8.2.259. PMID9931333.
Rinderle C, Christensen HM, Schweiger S, Lehrach H, Yaspo ML (February 1999). "AIRE encodes a nuclear protein co-localizing with cytoskeletal filaments: altered sub-cellular distribution of mutants lacking the PHD zinc fingers". Hum. Mol. Genet. 8 (2): 277–90. doi:10.1093/hmg/8.2.277. PMID9931335.
Pitkänen J, Doucas V, Sternsdorf T, Nakajima T, Aratani S, Jensen K, Will H, Vähämurto P, Ollila J, Vihinen M, Scott HS, Antonarakis SE, Kudoh J, Shimizu N, Krohn K, Peterson P (June 2000). "The autoimmune regulator protein has transcriptional transactivating properties and interacts with the common coactivator CREB-binding protein". J. Biol. Chem. 275 (22): 16802–9. doi:10.1074/jbc.M908944199. PMID10748110.
Pitkänen J, Vähämurto P, Krohn K, Peterson P (June 2001). "Subcellular localization of the autoimmune regulator protein. characterization of nuclear targeting and transcriptional activation domain". J. Biol. Chem. 276 (22): 19597–602. doi:10.1074/jbc.M008322200. PMID11274163.
Saugier-Veber P, Drouot N, Wolf LM, Kuhn JM, Frébourg T, Lefebvre H (April 2001). "Identification of a novel mutation in the autoimmune regulator (AIRE-1) gene in a French family with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy". Eur. J. Endocrinol. 144 (4): 347–51. doi:10.1530/eje.0.1440347. PMID11275943.
