TY - JOUR
T1 - A JAK2 interdomain linker relays epo receptor engagement signals to kinase activation
AU - Zhao, Lequn
AU - Dong, Hongyun
AU - Zhang, Chengcheng
AU - Kinch, Lisa
AU - Osawa, Mitsujiro
AU - Iacovino, Michelina
AU - Grishin, Nick V
AU - Kyba, Michael
AU - Huang, Jun-Shen
PY - 2009/9/25
Y1 - 2009/9/25
N2 - 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. Twoof 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.
AB - 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. Twoof 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.
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U2 - 10.1074/jbc.M109.011387
DO - 10.1074/jbc.M109.011387
M3 - Article
C2 - 19638629
AN - SCOPUS:70350351539
SN - 0021-9258
VL - 284
SP - 26988
EP - 26991
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 39
ER -