Fyn and JAK2 Mediate Ras Activation by Reactive Oxygen Species

doi:10.1074/jbc.274.30.21003

Fyn and JAK2 Mediate Ras Activation by Reactive Oxygen Species*

Jun-ichi Abe and
Bradford C. Berk‡

From the Center for Cardiovascular Research, University of Rochester, Rochester, New York 14642

Abstract

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. H₂O₂ 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−/−). H₂O₂-stimulated JAK2 activity was completely inhibited in Fyn−/− cells. Shc tyrosine phosphorylation and Ras activation by H₂O₂ 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 H₂O₂ stimulated Shc and Ras activation. H₂O₂-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.

Footnotes

↵* This work was supported by a grant from the Japanese Heart Foundation and Bayer Yakuhin Research Grant Abroad (to J. A.), and Grants HL44721 and HL49192 from National Institutes of Health (to B. C. B.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵‡ To whom correspondence should be addressed: Cardiology Unit, Box 679, 601 Elmwood Ave., University of Rochester School of Medicine and Dentistry, Rochester, NY 14642. Tel.: 716-273-1947; Fax: 716-473-1573; E-mail: bradford_berk@urmc.rochester.edu.
↵2 J. Abe and B. C. Berk, submitted.
Abbreviations:

ROS

reactive oxygen species

ERK

extracellular signal-regulated kinase

JAK

Janus kinase

RBD

Raf-binding domain

GST

glutathioneS-transferase
- Received March 29, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.