期刊
BIOCHEMICAL JOURNAL
卷 458, 期 -, 页码 395-405出版社
PORTLAND PRESS LTD
DOI: 10.1042/BJ20131516
关键词
V617F JAK2; Janus kinase; phosphorylation; pseudokinase; small-angle X-ray scattering (SAXS)
资金
- NHMRC (National Health and Medical Research Council) [1011 804, 1016647]
- National Institutes of Health [CA-22556]
- Leukaemia Foundation
- Australian Stem Cell Centre scholarships
- NHMRC fellowship
- ARC (Australian Research Council) fellowships [FT110100169, FT100100100]
- Medical Research Council of Academy of Finland
- Sigrid Juselius Foundation
- Medical Research Fund of Tampere University Hospital
- Finnish Cancer Foundation and the Tampere Tuberculosis Foundation
- Victorian State Government Operational Infrastructure Support
- NHMRC IRIISS (Victorian State Government Operational Infrastructure Support) [361646]
- Cancer Foundation Finland sr [100141, 140164] Funding Source: researchfish
- Novo Nordisk Fonden [NNF13SA0008469] Funding Source: researchfish
- Australian Research Council [FT110100169] Funding Source: Australian Research Council
JAK2 (Janus kinase 2) initiates the intracellular signalling cascade downstream of cell surface receptor activation by cognate haemopoietic cytokines, including erythropoietin and thrombopoietin. The pseudokinase domain (JH2) of JAK2 negatively regulates the catalytic activity of the adjacent tyrosine kinase domain (JH1) and mutations within the pseudokinase domain underlie human myeloproliferative neoplasms, including polycythaemia vera and essential thrombocytosis. To date, the mechanism of JH2-mediated inhibition of JH1 kinase activation as well as the susceptibility of pathological mutant JAK2 to inhibition by the physiological negative regulator SOCS3 (suppressor of cytokine signalling 3) have remained unclear. In the present study, using recombinant purified JAK2(JH1-JH2) proteins, we demonstrate that, when activated, wild-type and myeloproliferative neoplasm-associated mutants of JAK2 exhibit comparable enzymatic activity and inhibition by SOCS3 in in vitro kinase assays. SAXS (small-angle X-ray scattering) showed that JAK2(JH1-JH2) exists in an elongated configuration in solution with no evidence for interaction between JH1 and JH2 domains in cis. Collectively, these data are consistent with a model in which JAK2's pseudokinase domain does not influence the activity of JAK2 once it has been activated. Our data indicate that, in the absence of the N-terminal FERM domain and thus cytokine receptor association, the wild-type and pathological mutants of JAK2 are enzymatically equivalent and equally susceptible to inhibition by SOCS3.
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