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Crystal Structure of Interleukin-2 Inducible T-cell Kinase Itk Catalytic Domain with Thienopyrazolylindole Inhibitor 469Crystal Structure of Interleukin-2 Inducible T-cell Kinase Itk Catalytic Domain with Thienopyrazolylindole Inhibitor 469
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] Publication Abstract from PubMedBeginning with a screening hit, unique thienopyrazole-indole inhibitors of Itk (interleukin-2-inducible tyrosine kinase) were designed, synthesized, and crystallized in the target kinase. Although initial compounds were highly active in Itk, they were not selective. Increasing the steric bulk around a tertiary alcohol at the 5-indole position dramatically improved selectivity toward Lyk and Syk, but not Txk. Substitutions at the 3- and 4-indole positions gave less active compounds that remained poorly selective. A difluoromethyl substitution at the 5-position of the thienopyrazole led to a highly potent and selective compound. Phenyl at this position reduced activity and selectivity while pushing the side-chains of Lys-391 and Asp-500 away from the binding pocket. Novel and selective thienopyrazole inhibitors of Itk were designed as a result of combining structure-based design and medicinal chemistry. X-ray crystallographic structure-based design of selective thienopyrazole inhibitors for interleukin-2-inducible tyrosine kinase.,McLean LR, Zhang Y, Zaidi N, Bi X, Wang R, Dharanipragada R, Jurcak JG, Gillespy TA, Zhao Z, Musick KY, Choi YM, Barrague M, Peppard J, Smicker M, Duguid M, Parkar A, Fordham J, Kominos D Bioorg Med Chem Lett. 2012 May 1;22(9):3296-300. Epub 2012 Mar 11. PMID:22464456[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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