Proteasome-dependent degradation of oxidized proteins in MRC-5 fibroblasts.

Fibroblasts were exposed to various concentrations of hydrogen peroxide and the removal of oxidized proteins was followed by determining protein-bound carbonyls. Fibroblasts are able to increase the turnover of metabolically radiolabeled proteins after treatment with hydrogen peroxide. It was demonstrated for the first time, that the increased protein turnover was accompanied by a removal of protein-bound carbonyl groups. The proteasome-specific inhibitor lactacystin was able to inhibit the elimination of protein-bound carbonyl groups. Therefore, the key role of the proteasome in the degradation of oxidized proteins in fibroblasts could be demonstrated.