Reactive Oxygen Species

ROS Activation of Gα

Science's STKE  19 Mar 2002:
Vol. 2002, Issue 124, pp. tw108
DOI: 10.1126/stke.2002.124.tw108

Although treatment of myocytes with the reactive oxygen species (ROS) H2O2 activates the heterotrimeric GTP-binding proteins Gi and Go in a receptor-independent manner, the mechanismic detail of this effect has not been clear. Nishida et al. report that H2O2 is converted to a more reactive hydroxyl radical in the presence of Fe2+. Myocytes treated with a cell-permeable Fe2+ chelator inhibited the effect of H2O2 and subsequent activation of mitogen-activated protein kinase. This highly reactive ROS modified two specific cyteine resideus present only in Gαi and Gαo in vitro. The modification caused dissociation of Gαi from the Gβγ subunit and increased GTP binding. Mutation of the cysteines in Gαi inhibited subunit dissociation and the activating effect of the ROS radical. Treatment of Gαi with UV light in vitro, which generates ROS from O2 dissolved in solution, also required the presence of the critical cysteines, suggesting that such cellular stress can activate G proteins through ROS generation.

M. Nishida, K. L. Schey, S. Takagahara, K. Kontani, T. Katada, Y. Urano, T. Nagano, T. Nagao, H. Kurose, Activation mechanism of Gi and Go by reactive oxygen species. J. Biol. Chem. 277, 9036-9042 (2002). [Abstract] [Full Text]