To image redox signaling during HIV-1 infection, we created stably transfected promonocytic U1 cells that express either a cytosolic (U1-Grx1-roGFP2) or a mitochondrial (U1-mito-Grx1-roGFP2) EGSH bioprobe (Fig. 1, A and B). The gene discussed is GLRX; the disease is HIV-1 infection.