Fig. 4.

H₂O₂ mediates Zn²⁺-induced elevation in cytosolic but not mitochondrial glutathione redox potential. BEAS-2B cells expressing roGFP2 in the cytosol (A–G) or mitochondria (H–N), and either over expressing catalase (Cyto-catalse) or targeted-ectopic catalase expression in the mitochondria (Mito-catalase) were exposed to 50 µM Zn²⁺/1 µM PYRI at the indicated time (arrow). Ratiometric fluorescence values normalized as for sensor response utilizing the baseline and stimulus to 1 mM H₂O₂ as the minimum and maximum responses, respectively, in either the cytosol (A) or mitochondria (H) are shown. Values are presented as mean±SE (n≥3, where n consists of an average of 10 distinct cells' responses), ^⁎ indicates statistical significant change compared to control by linear regression. Representative cells expressing basal catalase levels (B, E, I, L), Cyto-catalase (C, F, J, M), or Mito-catalase (D, G, K, N) shown at baseline (min 4; B–D, I–K) and following Zn²⁺ stimulation (min 14; E–G, L–N). Fluorescence intensity color is shown as a function of increasing E_GSH, also interpreted as an increase in GSSG to GSH: lowE_GSHhighE_GSH.