Protein Kinase B Activation by Reactive Oxygen Species Is Independent of Tyrosine Kinase Receptor Phosphorylation and Requires Src Activity

Franca Esposito, Giuseppa Chirico, Nicola Montesano Gesualdi, Inmaculada Posadas, Rosario Ammendola, Tommaso Russo, Giuseppe Cirino, Filiberto Cimino
2003 Journal of Biological Chemistry  
Reactive oxygen species (ROS) participate as second messengers in the mitogenic signal transduction. Most of the experimental data supporting the role of ROS as signaling molecules have been obtained by using H 2 O 2 . Exposure of cells to H 2 O 2 rapidly increases tyrosine phosphorylation of tyrosine kinase receptors (TKRs) in the absence of growth factor binding, thus inducing the activation of downstream signaling cascades, like that of protein kinase B (AKT). Another molecule able to induce
more » ... cule able to induce an increase of intracellular ROS levels is diethylmaleate (DEM), which acts by depleting the ROS scavenger reduced glutathione (GSH). A comparison of the effects exerted by H 2 O 2 and DEM shows that the latter induces redox modifications milder than those generated by H 2 O 2 . We also demonstrated that DEM-induced redox modifications are not accompanied by platelet-derived growth factor-receptor (PDGF-R) and epidermal growth factor-receptor Tyr phosphorylation, although they are able to activate ERKs and AKT, with kinetics different from those observed following H 2 O 2 treatment. The activation of these two pathways is not blocked by AG1296, a selective inhibitor of PDGF-R Tyr kinase, thus confirming that the effects of DEM are not mediated by the TKR phosphorylation. On the contrary, PP2 (4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazole[3,4-d]pyrimidine), an inhibitor of Src kinase, completely prevents DEM-and H 2 O 2 -induced AKT activation but has no effect on the pathway of ERKs. Finally, nitration of Tyr residues in PDGF-R is observed in DEM-treated cells, thus suggesting that ROS-induced modifications different from Tyr phosphorylation can occur at the growth factor-receptor level and can be involved in the regulation of signaling pathways.
doi:10.1074/jbc.m211841200 pmid:12682076 fatcat:bccrv4zyvzeizbwstadbmearju