A JAK2 Interdomain Linker Relays Epo Receptor Engagement Signals to Kinase Activation*
AUTOR(ES)
Zhao, Lequn
FONTE
American Society for Biochemistry and Molecular Biology
RESUMO
JAK2 (Janus kinase 2) is essential for cytokine receptor signaling, and several lines of evidence support a causal role of an activating JAK2 mutation in myeloproliferative disorders. JAK2 activity is autoinhibited by its pseudokinase domain in the basal state, and the inhibition is released by cytokine stimulation; how engagement of the cognate receptor triggers this release is unknown. From a functional screen for gain-of-function JAK2 mutations, we discovered 13 missense mutations, nine in the pseudokinase domain and four in the Src homology 2 (SH2)-pseudokinase domain linker. These mutations identified determinants for autoinhibition and inducible activation in JAK2. Two of the mutants, K539I and N622I, resulted in erythrocytosis in mice. Scanning mutagenesis of the SH2-pseudokinase domain linker indicated that its N-terminal part was essential for interaction of JAK2 with the Epo receptor, whereas certain mutations in the C-terminal region conferred constitutive activation. We further showed that substitutions for Glu543-Asp544 in this linker or Leu611, Arg683, or Phe694 in the hinge proximal region of the pseudokinase domain resulted in activated JAK2 mutants that could not be further stimulated by Epo. These results suggest that the SH2-pseudokinase domain linker acts as a switch that relays cytokine engagement to JAK2 activation by flexing the pseudokinase domain hinge.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2785384Documentos Relacionados
- Tyrosine 813 Is a Site of JAK2 Autophosphorylation Critical for Activation of JAK2 by SH2-Bβ
- Activation of Jak2 catalytic activity requires phosphorylation of Y1007 in the kinase activation loop.
- Activation of JAK2 kinase mediated by the interleukin 6 signal transducer gp130.
- Activation of JAK2 tyrosine kinase by prolactin receptors in Nb2 cells and mouse mammary gland explants.
- Phosphorylation and internalization of gp130 occur after IL-6 activation of Jak2 kinase in hepatocytes.