Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 112, Issue 15, Pages 4642-4647Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1423201112
Keywords
JAK; pseudokinase domain; nucleotide binding; cytokine; myeloid neoplasia
Categories
Funding
- Medical Research Council of the Academy of Finland
- Sigrid Juselius Foundation
- Medical Research Fund of Tampere University Hospital
- Finnish Cancer Foundation
- Novo Nordisk Foundation
- Tampere Tuberculosis Foundation
- National Institutes of Health Grant [R21 AI095808]
- Swiss National Science Foundation Grants [310000-120724/1, 32003BB_135712/1]
- Swiss Cancer League Grant [KLS-2950-02-2012]
- Swiss National Science Foundation (SNF) [32003BB_135712] Funding Source: Swiss National Science Foundation (SNF)
- Cancer Foundation Finland sr [140164, 100141] Funding Source: researchfish
- Novo Nordisk Fonden [NNF13SA0008469] Funding Source: researchfish
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Pseudokinases lack conserved motifs typically required for kinase activity. Nearly half of pseudokinases bind ATP, but only few retain phosphotransfer activity, leaving the functional role of nucleotide binding in most cases unknown. Janus kinases (JAKs) are nonreceptor tyrosine kinases with a tandem pseudokinase-kinase domain configuration, where the pseudokinase domain (JAK homology 2, JH2) has important regulatory functions and harbors mutations underlying hematological and immunological diseases. JH2 of JAK1, JAK2, and TYK2 all bind ATP, but the significance of this is unclear. We characterize the role of nucleotide binding in normal and pathogenic JAK signaling using comprehensive structure-based mutagenesis. Disruption of JH2 ATP binding in wildtype JAK2 has only minor effects, and in the presence of type I cytokine receptors, the mutations do not affect JAK2 activation. However, JH2 mutants devoid of ATP binding ameliorate the hyperactivation of JAK2 V617F. Disrupting ATP binding in JH2 also inhibits the hyperactivity of other pathogenic JAK2 mutants, as well as of JAK1 V658F, and prevents induction of erythrocytosis in a JAK2 V617F myeloproliferative neoplasm mouse model. Molecular dynamic simulations and thermal-shift analysis indicate that ATP binding stabilizes JH2, with a pronounced effect on the C helix region, which plays a critical role in pathogenic activation of JAK2. Taken together, our results suggest that ATP binding to JH2 serves a structural role in JAKs, which is required for aberrant activity of pathogenic JAK mutants. The inhibitory effect of abrogating JH2 ATP binding in pathogenic JAK mutants may warrant novel therapeutic approaches.
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