Fig. 4.
Reduction of tetrameric p66CH2-CB by Trxs and GSH and model for the redox-mediated regulation of p66Shc. (a) Nonreducing SDS/PAGE of tetrameric p66CH2-CB incubated with a 2-fold molar excess of Trx1 and Trx2, 5 mM GSH, 5 mM cysteine, or 5 mM DTT. (b) Pretreatment of the p66CH2-CB tetramer with Trx2 reduces its apoptosis inducing activity. (c) Model of the redox-mediated regulation of p66Shc. After cellular stress dimeric p66Shc translocates to mitochondria. Under conditions of lower stress the Trx and GSH systems reduce tetrameric p66Shc and prevent apoptosis, whereas excessive oxidative stress leads to an overload of the redox systems and accumulation of active, tetrameric p66Shc. p66Shc-generated ROS then activate the PTP, which results in rupture of the mitochondria and release of apoptotic factors. MC, metal chaperone; TOM, translocase of the outer membrane.