Tyrosine Kinase 2-mediated Signal Transduction in T Lymphocytes Is Blocked by Pharmacological Stabilization of Its Pseudokinase Domain

J Biol Chem. 2015 Apr 24;290(17):11061-74. doi: 10.1074/jbc.M114.619502. Epub 2015 Mar 11.


Inhibition of signal transduction downstream of the IL-23 receptor represents an intriguing approach to the treatment of autoimmunity. Using a chemogenomics approach marrying kinome-wide inhibitory profiles of a compound library with the cellular activity against an IL-23-stimulated transcriptional response in T lymphocytes, a class of inhibitors was identified that bind to and stabilize the pseudokinase domain of the Janus kinase tyrosine kinase 2 (Tyk2), resulting in blockade of receptor-mediated activation of the adjacent catalytic domain. These Tyk2 pseudokinase domain stabilizers were also shown to inhibit Tyk2-dependent signaling through the Type I interferon receptor but not Tyk2-independent signaling and transcriptional cellular assays, including stimulation through the receptors for IL-2 (JAK1- and JAK3-dependent) and thrombopoietin (JAK2-dependent), demonstrating the high functional selectivity of this approach. A crystal structure of the pseudokinase domain liganded with a representative example showed the compound bound to a site analogous to the ATP-binding site in catalytic kinases with features consistent with high ligand selectivity. The results support a model where the pseudokinase domain regulates activation of the catalytic domain by forming receptor-regulated inhibitory interactions. Tyk2 pseudokinase stabilizers, therefore, represent a novel approach to the design of potent and selective agents for the treatment of autoimmunity.

Keywords: Allosteric Regulation; Janus Kinase (JAK); Molecular Pharmacology; Pseudokinase; Signal Transduction; Structural Biology.

MeSH terms

  • Crystallography, X-Ray
  • Enzyme Stability
  • Humans
  • Janus Kinase 1 / genetics
  • Janus Kinase 1 / metabolism
  • Janus Kinase 3 / genetics
  • Janus Kinase 3 / metabolism
  • Models, Molecular*
  • Protein Structure, Tertiary
  • Receptors, Interleukin-2 / genetics
  • Receptors, Interleukin-2 / metabolism
  • Receptors, Thrombopoietin / genetics
  • Receptors, Thrombopoietin / metabolism
  • Signal Transduction*
  • T-Lymphocytes / enzymology*
  • TYK2 Kinase / chemistry*
  • TYK2 Kinase / genetics


  • Receptors, Interleukin-2
  • Receptors, Thrombopoietin
  • MPL protein, human
  • JAK1 protein, human
  • JAK3 protein, human
  • Janus Kinase 1
  • Janus Kinase 3
  • TYK2 Kinase
  • TYK2 protein, human