Influence of zinc on protein metabolism in various lung cell lines

Abstract

Toxic cellular effects after exposure to elevated zinc concentrations affect protein metabolism. We separated proteins by 2D-PAGE after cellular zinc exposure in order to decide whether changes in protein metabolism of specific proteins by elevated zinc might be a main critical cellular effect. The investigation was performed with fibroblast-like (11Lu, 16Lu) and alveolar epithelial (L2, A549) lung cell lines. Silver staining and autoradiography after radiolabelled methionine incorporation of 2D gels of cellular proteins was executed in order to look for specific changes in protein content. Methionine incorporation decreased in a concentration- and time-dependent manner to values of 10% with 100 μ mzinc chloride for 3 hr in the non-malignant cell lines, while about 20% was reached with 200 μ m after 4 hr of incubation in the malignant A549 cells. In silver stained 2D gels of zinc-exposed cells only few differences as compared to controls were detectable. Autoradiograms of 2D gels after methionine incorporation showed few additional spots that could be heat shock proteins in alveolar epithelial cell lines after zinc exposure. Autoradiographically detectable methionine in 2D-gels obtained after exposure of cells to high zinc concentrations for time intervals greater than 1 hr showed a time-dependent decrease in all cell lines. This decrease was accompanied by an increase of three characteristic spots at 28/9 (kDa/pI), 32/8 and 42/7.5 respectively, amounting to 15–30% of all incorporated radioactivity after 2–4 hr of zinc exposure. When cells were allowed to recover from zinc poisoning, similar 2D gel spot patterns as compared to controls without zinc exposure were obtained in all cell lines tested.