4kio | pdb_00004kio
Kinase domain mutant of human Itk in complex with a covalently-binding inhibitor
Structural highlights
DiseaseITK_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] FunctionITK_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 PubMedIL-2 inducible tyrosine kinase (Itk) plays a key role in antigen receptor signalling in T cells and is considered an important target for anti-inflammatory drug discovery. In order to generate inhibitors with the necessary potency and selectivity, a compound that targeted Cysteine442 in the ATP binding pocket and with an envisaged irreversible mode of action was designed. We incorporated a high degree of molecular recognition and specific design features making the compound suitable for inhaled delivery. This study confirms the irreversible covalent binding of the inhibitor to the kinase by X-ray crystallography and enzymology, whilst demonstrating potency, selectivity, and prolonged duration of action in in vitro biological assays. The biosynthetic turnover of the kinase was also examined as a critical factor when designing irreversible inhibitors for extended duration of action. The exemplified Itk inhibitor demonstrated inhibition of both TH1 and TH2 cytokines, was additive with fluticasone propionate and inhibited cytokine release from human lung fragments. Finally, we describe an in vivo pharmacodynamic assay that allows rapid preclinical development without animal efficacy models. Discovery of novel irreversible inhibitors of IL-2 inducible tyrosine kinase (Itk) by targeting cysteine 442 in the ATP pocket.,Harling JD, Deakin AM, Campos S, Grimley R, Chaudry L, Nye C, Polyakova O, Bessant CM, Barton N, Somers D, Barrett J, Graves RH, Hanns L, Kerr WJ, Solari R J Biol Chem. 2013 Aug 9. PMID:23935099[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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