Overexpression of glutaredoxin 2 attenuates apoptosis by preventing cytochrome c release

Human mitochondrial glutaredoxin 2 (Grx2) catalyzes glutathione-dependent dithiol reaction mechanisms, reducing protein disulfides, and monothiol reactions, reducing mixed disulfides between proteins and GSH (de-/glutathionylation). Here, we have overexpressed Grx2 in HeLa cells in its mitochondrial form (mGrx2-HeLa) as well as a truncated cytosolic form, lacking the mitochondrial translocation signal (tGrx2-HeLa). The resulting clones were less susceptible to apoptosis induced by 2-deoxy-d-glucose (2-DG) or doxorubicin (Dox). Overexpression of Grx2 inhibited cytochrome c release and caspase activation induced by both agents. In addition, Grx2 prevented 2-DG- and Dox-induced loss of cardiolipin, the phospholipid anchoring cytochrome c to the inner mitochondrial membrane. Overexpression of mGrx2 provided better protection than tGrx2 overexpression, especially after treatment with 2-DG. We propose that Grx2 facilitates the maintenance of cellular redox homeostasis upon treatment with apoptotic agents, thereby preventing cardiolipin oxidation and cytochrome c release.