Tyrosine kinase | EPFL Graph Search

A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions. Tyrosine kinases belong to a larger class of enzymes known as protein kinases which also attach phosphates to other amino acids such as serine and threonine. Phosphorylation of proteins by kinases is an important mechanism for communicating signals within a cell (signal transduction) and regulating cellular activity, such as cell division. Protein kinases can become mutated, stuck in the "on" position, and cause unregulated growth of the cell, which is a necessary step for the development of cancer. Therefore, kinase inhibitors, such as imatinib and osimertinib, are often effective cancer treatments. Most tyrosine kinases have an associated protein tyrosine phosphatase, which removes the phosphate group. Reaction Protein kinases are a group of enzymes that possess a

Allosteric regulation and targeting of Bruton's tyrosine kinase (Btk) in B-cell lymphoma

Daniel Pereira Duarte

Bruton's tyrosine kinase (Btk) is a key component of BCR signaling required for B-cell maturation and activation. Loss-of-function mutations throughout the Btk protein cause human X-linked agammaglobulinemia (XLA), a heritable genetic disorder characterized by the absence of mature B-cells and lack of adaptive immune response. In contrast, Btk signaling sustains the growth of several B-cell neoplasms, which may be treated with small-molecule tyrosine kinase inhibitors (TKIs) targeting the ATP-site of the kinase. No alternative targeted therapy is available for patients who acquire resistance to current Btk inhibitors. Whereas a number of intramolecular interactions amongst the PH, SH3, SH2, and kinase domain (KD) are well resolved and stabilize a compact autoinhibited conformation, the molecular mechanisms governing Btk activation are not fully understood. Using a combination of in silico, structural, cellular, and molecular approaches, we discovered an allosteric interface between the SH2 and the N-lobe of the KD that is critical for kinase activation in vitro and cells. In contrast to the low Btk activity of the KD alone, the presence of the SH2 domain is sufficient to increase Btk phosphorylation at Y551 and multiple other sites. This provides the structural mechanism by which a subset of XLA mutations mapped to the SH2 domain near the interface region strongly perturbs Btk activation, even though the SH2 canonical function is preserved. Furthermore, we demonstrated that the active Btk SH2-kinase adopts an elongated conformation with a dynamic contact interface structurally distinct than to the ones observed for other tyrosine kinases, such as Abl, Fes, and Csk. As allosteric interactions provide unique targeting opportunities far from the ATP-site, we developed an engineered repebody protein binding to the human Btk SH2 domain. The crystal structure of the SH2-repebody complex combined with other structural approaches demonstrated that the repebody disrupts the SH2-kinase interaction. The repebody prevented activation of wild-type and TKI-resistant Btk in vitro and cells seen by a significant decrease in Btk phosphorylation. In parallel, sole allosteric targeting inhibited Btk-dependent signaling and reduced proliferation of malignant B-cells dependent on the BCR signaling. Therefore, the SH2-kinase interface is critical for Btk activation and is the first targetable site able to trigger allosteric inhibition. As Btk targeted therapy has a great impact on several conditions, including B-cell malignancies and autoimmune diseases, this study provides a rationale to support the development of alternative Btk inhibitors. This approach for targeted inhibition could particularly benefit patients with current therapy-resistant Btk variants.

EPFL2020

The Multi-kinase Inhibitor Debio 0617B Reduces Maintenance and Self-renewal of Primary Human AML CD34(+) Stem/Progenitor Cells

Michel Aguet, Andres McAllister, Maximilien Murone, Stefania Rigotti

Acute myelogenous leukemia (AML) is initiated and maintained by leukemia stem cells (LSC). LSCs are therapy-resistant, cause relapse, and represent a major obstacle for the cure of AML. Resistance to therapy is often mediated by aberrant tyrosine kinase (TK) activation. These TKs primarily activate downstream signaling via STAT3/STAT5. In this study, we analyzed the potential to therapeutically target aberrant TK signaling and to eliminate LSCs via the multi-TK inhibitor Debio 0617B. Debio 0617B has a unique profile targeting key kinases upstream of STAT3/STAT5 signaling such as JAK, SRC, ABL, and class III/V receptor TKs. We demonstrate that expression of phospho-STAT3 (pSTAT3) inAML blasts is an independent prognostic factor for overall survival. Furthermore, phospho-STAT5 (pSTAT5) signaling is increased in primary CD34(+) AML stem/progenitors. STAT3/STAT5 activation depends on tyrosine phosphorylation, mediated by several upstream TKs. Inhibition of single upstream TKs did not eliminate LSCs. In contrast, the multi-TK inhibitor Debio 0617B reduced maintenance and self-renewal of primary human AML CD34(+) stem/progenitor cells in vitro and in xenotransplantation experiments resulting in long-term elimination of human LSCs and leukemia. Therefore, inhibition of multiple TKs upstream of STAT3/5 may result in sustained therapeutic efficacy of targeted therapy in AML and prevent relapses. (C)2017 AACR.

Amer Assoc Cancer Research2017

Novel irreversible covalent BTK inhibitors discovered using DNA-encoded chemistry

Sevan Mleh Habeshian, Ying Zhang

Libraries of DNA-Encoded small molecules created using combinatorial chemistry and synthetic oligonucleotides are being applied to drug discovery projects across the pharmaceutical industry. The majority of reported projects describe the discovery of reversible, i.e. non-covalent, target modulators. We synthesized multiple DNAencoded chemical libraries terminated in electrophiles and then used them to discover covalent irreversible inhibitors and report the successful discovery of acrylamide- and epoxide-terminated Bruton's Tyrosine Kinase (BTK) inhibitors. We also demonstrate their selectivity, potency and covalent cysteine engagement using a range of techniques including X-ray crystallography, thermal transition shift assay, reporter displacement assay and intact protein complex mass spectrometry. The epoxide BTK inhibitors described here are the first ever reported to utilize this electrophile for this target.

PERGAMON-ELSEVIER SCIENCE LTD2021

Allosteric regulation and targeting of Bruton's tyrosine kinase (Btk) in B-cell lymphoma

Daniel Pereira Duarte

EPFL2020