Inhibition of [125I]epidermal growth factor binding to murine fibroblasts and keratinocytes by irradiation with UV-B light. Evidence for a protein kinase C-independent mechanism.

Treatment of murine Swiss 3T3 fibroblasts and XB/2 keratinocytes with UV-B light (302 nm) resulted in a dose-dependent inhibition of [125I]epidermal growth factor (EGF) binding. The light dose required to achieve 50% inhibition of binding in both cell types was 80-85 J/m2. Decreased [125I]platelet-derived growth factor binding was not evoked even by light doses of up to 280 J/m2. UV-B irradiation did not stimulate phosphorylation of the 80 kd protein substrate for protein kinase C. Furthermore, its effect on [125I]EGF binding was not altered as a consequence of protein kinase C down-regulation following prolonged exposure of cells to phorbol esters. These results indicate that UV-B-induced transmodulation of the epidermal growth factor receptor is a specific event mediated through a protein kinase C-independent pathway. Transfer of culture medium from irradiated cells to untreated control cells showed this effect was not induced as a result of transforming growth factor alpha release and subsequent binding to the EGF receptor in these cells.