Nuclear accumulation of epidermal growth factor in cultured bovine corneal endothelial and granulosa cells.

Abstract

Intracellular accumulation of intact 125I-labeled epidermal growth factor (125I-EGF) in corneal or granulosa cell cultures exposed to either chloroquine or leupeptin can be 10-fold higher than that observed in cultures not exposed to the lysosomal inhibitors. This has made it possible to study the translocation and accumulation of 125I-EGF in a nuclear fraction of both cell types. The accumulation of 125I-EGF was found to be dependent on the inhibitor's concentrations. Chloroquine at a concentration of 5 X 10(-5) M yielded a maximal nuclear accumulation which amounted to 18% of the total 125I-EGF present within the bovine corneal endothelial cells exposed to chloroquine. Nuclear accumulation could be detected in that cell type as early as 4 h after cultures were exposed to both chloroquine and 125I-EGF and was maximal by 24 h. Saturation of nuclear accumulation of 125I-EGF in corneal endothelial and granulosa cell cultures was observed at 20 and 10 ng/ml of 125I-EGF, respectively. After 24 h, 1.06 X 10(4) and 1.4 X 10(4) 125I-EGF molecules were found associated with granulosa or corneal endothelial nuclei, respectively. In corneal endothelial cell cultures exposed to chloroquine, a small fraction (0.6%) of 125I-EGF associated with the cell was found to be irreversibly found to a polypeptide with a molecular weight of 185,000, and 50% of these irreversible 125I-EGF . receptor complexes were found to be associated with the nuclei.