Oxidation of ER resident proteins upon oxidative stress: effects of altering cellular redox/antioxidant status and implications for protein maturation.

Previous work showed that from all cellular proteins, the endoplasmic reticulum (ER) resident proteins are most sensitive to oxidative stress [hydrogen peroxide (H(2)O(2))], as determined using the oxidation-sensitive, membrane-permeable, acetylTyrFluo probe. Because of the importance of these proteins in proper cellular functioning, we studied (a) whether modifying the cellular redox state/antioxidant status alters the susceptibility of those proteins toward H(2)O(2) oxidative stress and (b) whether H(2)O(2) affects ER function with regard to protein folding. The cellular redox and/or antioxidative capacity was modified in several ways.

Endoplasmic reticulum resident proteins of normal human dermal fibroblasts are the major targets for oxidative stress induced by hydrogen peroxide.

The membrane-permeable fluorescein-labelled tyramine conjugate (acetylTyrFluo) was used to identify the proteins of normal human dermal fibroblasts most susceptible to oxidation by hydrogen peroxide [Van der Vlies, Wirtz and Pap (2001) Biochemistry 40, 7783-7788]. By exposing the cells to H(2)O(2) (0.1 mM for 10 min), TyrFluo was covalently linked to target proteins.