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Reactive oxygen species activate p90 ribosomal S6 kinase via Fyn and Ras
1Center for Cardiovascular Research, University of Rochester, Rochester, New York 14642, USA.
Abstract:
Reactive oxygen species and growth factors stimulate similar intracellular signal transduction events including activation of Src kinase family members and extracellular signal-regulated kinases (ERK1/2). A potentially important downstream effector of Src and ERK1/2 is p90 ribosomal S6 kinase (p90RSK), which plays an important role in cell growth by activating several transcription factors as well as the Na(+)/H(+) exchanger. In the present study, we determined whether H(2)O(2) activates p90RSK to gain insight into signal transduction mechanisms activated by reactive oxygen species. H(2)O(2) (200 microM) stimulated ERK1/2 and p90RSK activity in lymphocytes, endothelial cells, and fibroblasts. The MEK-1 inhibitor, PD98059 (30 microM), inhibited H(2)O(2)-mediated activation of ERK1/2 but not of p90RSK. An essential role for Fyn and Ras in p90RSK activation was suggested by five findings. 1) The tyrosine kinase inhibitor, herbimycin A, and the specific Src kinase family inhibitor, PP1, blocked p90RSK activation by H(2)O(2) in a concentration-dependent manner. 2) p90RSK activation by H(2)O(2) was significantly reduced in fibroblasts derived from transgenic mice deficient in Fyn, but not c-Src. 3) H(2)O(2) rapidly activated Ras (peak at 2-5 min), which preceded p90RSK activation (peak at 20 min). 4) Dominant negative Ras completely blocked H(2)O(2)-induced activation of p90RSK. 5) In Fyn-/- fibroblasts, activation of Ras by H(2)O(2) was significantly attenuated. These results show essential roles for Fyn and Ras in H(2)O(2)-mediated activation of p90RSK and establish redox-sensitive regulation of Ras and p90RSK as a new function for Fyn.
Insights
Hydrogen peroxide (H2O2) activates p90 ribosomal S6 kinase (p90RSK) through the Fyn and Ras signaling pathways. This study reveals a novel mechanism for reactive oxygen species in regulating cell growth signaling.
Area of Science:
- Cellular signaling
- Biochemistry
- Molecular biology
Background:
- Reactive oxygen species (ROS) and growth factors activate similar intracellular signaling pathways.
- p90 ribosomal S6 kinase (p90RSK) is a key downstream effector involved in cell growth.
- Understanding ROS-mediated signaling is crucial for various biological processes.
Purpose of the Study:
- To investigate whether hydrogen peroxide (H2O2) activates p90RSK.
- To elucidate the signal transduction mechanisms involved in ROS-activated pathways.
- To identify the specific kinases and signaling molecules mediating H2O2 effects on p90RSK.
Main Methods:
- Stimulation of various cell types (lymphocytes, endothelial cells, fibroblasts) with H2O2.
- Use of specific inhibitors: MEK-1 inhibitor (PD98059), tyrosine kinase inhibitor (herbimycin A), and Src kinase family inhibitor (PP1).
- Employing genetic approaches: fibroblasts from Fyn-deficient mice and dominant-negative Ras expression.
Main Results:
- H2O2 stimulated both ERK1/2 and p90RSK activity in multiple cell types.
- PD98059 inhibited H2O2-mediated ERK1/2 activation but not p90RSK activation.
- p90RSK activation by H2O2 was dependent on Fyn kinase and Ras.
- H2O2 rapidly activated Ras, preceding p90RSK activation, and this was attenuated in Fyn-deficient cells.
Conclusions:
- Fyn and Ras play essential roles in H2O2-induced p90RSK activation.
- Redox-sensitive regulation of Ras and p90RSK represents a new function for Fyn.
- This study uncovers a novel signaling pathway initiated by reactive oxygen species.