Fyn and JAK2 mediate Ras activation by reactive oxygen species.
Reactive oxygen species (ROS) activate Ras and the extracellular signal-regulated kinase (ERK) cascade. Because JAK2 is a critical mediator for Ras/Raf/ERK activation by several hormones, we examined the role of JAK2 in ROS signal events. H(2)O(2) stimulated JAK2 activity in fibroblasts with peak at 2-5 min. To determine the specific role of Src and Fyn as mediators of JAK2 activation and its downstream events, we used fibroblasts derived from transgenic mice deficient in Src (Src-/-) or Fyn (Fyn-/-). H(2)O(2)-stimulated JAK2 activity was completely inhibited in Fyn-/- cells. Shc tyrosine phosphorylation and Ras activation by H(2)O(2) were also significantly reduced in Fyn-/- cells, but not altered in Src-/- cells. Activation of JAK2 was restored when Fyn-/- cells were transfected with B-Fyn but not with Src. Inhibiting JAK2 activity with the specific inhibitor AG-490 prevented H(2)O(2) stimulated Shc and Ras activation. H(2)O(2)-mediated ERK1/2 activation in Fyn-/- cells and AG-490 treated cells was completely inhibited at an early time (5 min), but not at late times (20-40 min) after stimulation. These results define a new redox-sensitive pathway for Ras activation and rapid ERK1/2 activation, which is mediated by Fyn and JAK2.
Center for Cardiovascular Research, University of Rochester, Rochester, New York 14642, USA.
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D000818:Animals; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism*; D053614:Janus Kinase 2; D051379:Mice; D010084:Oxidation-Reduction; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051076:Proto-Oncogene Proteins c-fyn; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction; D018631:ras Proteins / Q000378:metabolism*
D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; D011505:Protein-Tyrosine Kinases; C494960:Fyn protein, mouse; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D051076:Proto-Oncogene Proteins c-fyn; D018631:ras Proteins