To study early changes in angiotensin II (Ang II)-induced signaling with post-translational modifications, we analyzed proteins from cultured human coronary smooth muscle cells stimulated with Ang II, using two-dimensional difference gel electrophoresis (2D-DIGE) combined with ProQ Diamond and SYPRO Ruby staining, followed by mass spectrometry or Western blotting. Among 40 proteins identified, peroxiredoxin 2 (Prx2) was oxidized and 58 kDa glucose-regulated protein (GRP58) was phosphorylated after 5 min of Ang II (1 mu M) stimulation. Valsartan, a selective Ang II type 1 (AT1) receptor blocker, and N-acetylcysteine, an antioxidant, inhibited both of these modifications, indicating the contribution of AT1 receptor and reactive oxygen species to oxidation of Prx2 and phosphorylation of GRP58 by Ang II. (C) 2007 Elsevier Inc. All rights reserved.