Regulation of Jak2 function by phosphorylation of Tyr317 and Tyr637 during cytokine signaling.
Jak2, the cognate tyrosine kinase for numerous cytokine receptors, undergoes multisite phosphorylation during cytokine stimulation. To understand the role of phosphorylation in Jak2 regulation, we used mass spectrometry to identify numerous Jak2 phosphorylation sites and characterize their significance for Jak2 function. Two sites outside of the tyrosine kinase domain, Tyr(317) in the FERM domain and Tyr(637) in the JH2 domain, exhibited strong regulation of Jak2 activity. Mutation of Tyr(317) promotes increased Jak2 activity, and the phosphorylation of Tyr(317) during cytokine signaling requires prior activation loop phosphorylation, which is consistent with a role for Tyr(317) in the feedback inhibition of Jak2 kinase activity after receptor stimulation. Comparison to several previously identified regulatory phosphorylation sites on Jak2 revealed a dominant role for Tyr(317) in the attenuation of Jak2 signaling. In contrast, mutation of Tyr(637) decreased Jak2 signaling and activity and partially suppressed the activating JH2 V617F mutation, suggesting a role for Tyr(637) phosphorylation in the release of JH2 domain-mediated suppression of Jak2 kinase activity during cytokine stimulation. The phosphorylation of Tyr(317) and Tyr(637) act in concert with other regulatory events to maintain appropriate control of Jak2 activity and cytokine signaling.
Department of Internal Medicine, University of Michigan Medical School, 5560 MSRB II, MSP5678, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA.
Scott A
SA
Robertson
Rositsa I
RI
Koleva
Lawrence S
LS
Argetsinger
Christin
C
Carter-Su
Jarrod A
JA
Marto
Edward P
EP
Feener
Martin G
MG
Myers
D000595:Amino Acid Sequence; D001665:Binding Sites; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism*; D025461:Feedback, Physiological; D006801:Humans; D053614:Janus Kinase 2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D053719:Tandem Mass Spectrometry; D014443:Tyrosine / Q000737:chemistry
D016207:Cytokines; D011994:Recombinant Proteins; D014443:Tyrosine; C507924:JAK2 protein, human; D053614:Janus Kinase 2