Activation of in situ tissue transglutaminase by intracellular reactive oxygen species

We have investigated the novel function of intracellular reactive oxygen species (ROS) in the activation of in situ tissue transglutaminase (tTGase) by lysophosphatidic acid (LPA) and transforming growth factor-beta (TGF-beta) in Swiss 3T3 fibroblasts. LPA induced a transient increase of intracellular ROS with a maximal increase at 10 min, which was blocked by ROS scavengers, N-acetyl-L-cysteine and catalase. LPA activated tTGase with a maximal increase at I It, which was inhibited by cystamine and ROS scavengers. Incubation with exogenous H2O2 activated tTGase. TGF-beta also activated tTGase with a maximal activation at 2 h and the tTGase activation was inhibited by the ROS scavengers. Scrape-loading of C3 transferase inhibited the ROS production and in situ tTGase activation by LPA and TGF-beta, and the inhibitory effect of C3 transferase was reversed by exogenous H2O2. Microinjection of GTPgammaS inhibited transamidating activity of tTGase stimulated by LPA, TGF-beta, and maitotoxin. These results suggested that intracellular ROS was essential for the activation of in situ tTGase in response to LPA and TGF-beta. (C) 2003 Elsevier Science (USA). All rights reserved.