Structures of human Bruton's tyrosine kinase in active and inactive conformations suggest a mechanism of activation for TEC family kinases

Abstract

Bruton's tyrosine kinase (BTK), a member of the TEC family of kinases, plays a crucial role in B-cell maturation and mast cell activation. Although the structures of the unphosphorylated mouse BTK kinase domain and the unphosphorylated and phosphorylated kinase domains of human ITK are known, understanding the kinase selectivity profiles of BTK inhibitors has been hampered by the lack of availability of a high resolution, ligand-bound BTK structure. Here, we report the crystal structures of the human BTK kinase domain bound to either Dasatinib (BMS-354825) at 1.9 Å resolution or to 4-amino-5-(4-phenoxyphenyl)-7H-pyrrolospyrimidin-7-yl-cyclopentane at 1.6 Å resolution. This data provides information relevant to the development of small molecule inhibitors targeting BTK and the TEC family of nonreceptor tyrosine kinases. Analysis of the structural differences between the TEC and Src families of kinases near the Trp-Glu-Ile motif in the N-terminal region of the kinase domain suggests a mechanism of regulation of the TEC family members.

Quick Evaluation of Kinase Inhibitors by Surface Plasmon Resonance Using Single-Site Specifically Biotinylated Kinases

“…There are at least six substituted residues in EGFR compared with BTK in the dasatinib binding site that are thought to be responsible for lowering the affinity. 17 In the present study, the difference of affinity against dasatinib between BTK and EGFR (8.50 × 10 -10 M and 1.74 × 10 -8 M, respectively) is well correlated with the difference of dissociation rate (4.17 × 10 -4 s -1 and 0.01 s -1 , respectively). CSF1R also showed an interaction with dasatinib, whereas kinases that have other residues than threonine (leucine for ALK and PLK1, methionine for IGF1R, respectively) did not show any interaction with dasatinib.…”

The Bruton tyrosine kinase inhibitor PCI-32765 blocks B-cell activation and is efficacious in models of autoimmune disease and B-cell malignancy

“…BCR stimulation recruits Btk to the cell membrane via interactions between the N-terminal PH domain and cell membrane phosphoinositides and membrane-associated Btk is then phosphorylated at Tyr-551 in the activation loop by Src family kinases (3). Subsequent Btk autophosphorylation at Tyr-223 stabilizes the active conformation and fully activates Btk kinase activity (18). Activated Btk phosphorylates PLCγ (5), initiating calcium mobilization and generating diacylglycerol as secondary signals, eventually leading to NF-κB transcriptional activation and amplification of BCR stimulation.…”

Ibrutinib is an irreversible molecular inhibitor of ITK driving a Th1-selective pressure in T lymphocytes

“…[19][20][21][22] Intriguingly, ITK shares significant sequence and functional homology with BTK and both contain an ibrutinib inhibition motif consisting of an SH3 autophosphorylatable tyrosine (Tyr) and a covalent binding cysteine (Cys) residue within the hinge region connecting the C and N lobes of the active site. 23 ITK had previously been discounted as a relevant target of ibrutinib given a lack of sufficient in vitro evidence; not long after, however, Herman et al noted effects on T-cell cytokine production, reigniting the inquiry. 16,18 The striking homology between BTK and ITK combined with intriguing in silico docking led to the hypothesis that ibrutinib is the first clinically viable ITK inhibitor.…”