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Structural highlights

Disease

[ITK_HUMAN] Defects in ITK are the cause of lymphoproliferative syndrome EBV-associated autosomal type 1 (LPSA1) [MIM:613011]. LPSA1 is a rare immunodeficiency characterized by extreme susceptibility to infection with Epstein-Barr virus (EBV). Inadequate immune response to EBV can have a fatal outcome. Clinical features include splenomegaly, lymphadenopathy, anemia, thrombocytopenia, pancytopenia, recurrent infections. There is an increased risk for lymphoma.^[1]

Function

[ITK_HUMAN] Tyrosine kinase that plays an essential role in regulation of the adaptive immune response. Regulates the development, function and differentiation of conventional T-cells and nonconventional NKT-cells. When antigen presenting cells (APC) activate T-cell receptor (TCR), a series of phosphorylation lead to the recruitment of ITK to the cell membrane, in the vicinity of the stimulated TCR receptor, where it is phosphorylated by LCK. Phosphorylation leads to ITK autophosphorylation and full activation. Once activated, phosphorylates PLCG1, leading to the activation of this lipase and subsequent cleavage of its substrates. In turn, the endoplasmic reticulum releases calcium in the cytoplasm and the nuclear activator of activated T-cells (NFAT) translocates into the nucleus to perform its transcriptional duty. Phosphorylates 2 essential adapter proteins: the linker for activation of T-cells/LAT protein and LCP2. Then, a large number of signaling molecules such as VAV1 are recruited and ultimately lead to lymphokine production, T-cell proliferation and differentiation.^{[2] [3] [4]}

References

1. ↑ Huck K, Feyen O, Niehues T, Ruschendorf F, Hubner N, Laws HJ, Telieps T, Knapp S, Wacker HH, Meindl A, Jumaa H, Borkhardt A. Girls homozygous for an IL-2-inducible T cell kinase mutation that leads to protein deficiency develop fatal EBV-associated lymphoproliferation. J Clin Invest. 2009 May;119(5):1350-8. PMID:19425169
2. ↑ Perez-Villar JJ, Whitney GS, Sitnick MT, Dunn RJ, Venkatesan S, O'Day K, Schieven GL, Lin TA, Kanner SB. Phosphorylation of the linker for activation of T-cells by Itk promotes recruitment of Vav. Biochemistry. 2002 Aug 27;41(34):10732-40. PMID:12186560
3. ↑ Grasis JA, Browne CD, Tsoukas CD. Inducible T cell tyrosine kinase regulates actin-dependent cytoskeletal events induced by the T cell antigen receptor. J Immunol. 2003 Apr 15;170(8):3971-6. PMID:12682224
4. ↑ Sela M, Bogin Y, Beach D, Oellerich T, Lehne J, Smith-Garvin JE, Okumura M, Starosvetsky E, Kosoff R, Libman E, Koretzky G, Kambayashi T, Urlaub H, Wienands J, Chernoff J, Yablonski D. Sequential phosphorylation of SLP-76 at tyrosine 173 is required for activation of T and mast cells. EMBO J. 2011 Jul 1;30(15):3160-72. doi: 10.1038/emboj.2011.213. PMID:21725281 doi:10.1038/emboj.2011.213
5. ↑ Pastor RM, Burch JD, Magnuson S, Ortwine DF, Chen Y, De La Torre K, Ding X, Eigenbrot C, Johnson A, Liimatta M, Liu Y, Shia S, Wang X, Wu LC, Pei Z. Discovery and optimization of indazoles as potent and selective interleukin-2 inducible T cell kinase (ITK) inhibitors. Bioorg Med Chem Lett. 2014 Jun 1;24(11):2448-52. doi: 10.1016/j.bmcl.2014.04.023., Epub 2014 Apr 16. PMID:24767842 doi:http://dx.doi.org/10.1016/j.bmcl.2014.04.023