Interferon receptor interaction

Studies reported earlier [Joshi et al. (1982) J. Biol. Chem. 257 , 13884–13887] have indicated that human interferon‐ α 2 (HuIFN‐ α 2 ) binds to a specific macromolecular receptor on human cells as identified by cross‐linking with bifunctional cross‐linking reagents and analysis by polyacrylamide gel electrophoresis. We have carried out experiments to investigate the fate of the interferon‐receptor complex on the cell surface under conditions which lead to cellular response. As analyzed by cross‐linking and gel electrophoresis, the interferon‐receptor complex, formed on incubation with 125 I‐IFN‐ α 2 at 4 °C, persisted at the cell surface for several hours at 4 °C; however, if the cells were switched to 37 °C, there was a rapid decline in the complex, apparently due to a loss of the interferon receptors from the cell surface. This was associated with an internalization of the 125 I‐interferon as indicated by the fact that, on incubation at 37 °C, an appreciable fraction of the cell‐associated interferon (∼ 50%) became resistant to trypsin digestion, or dissociation on incubation in growth medium or low‐pH buffer. A large fraction of the trypsin‐resistant (internalized) 125 I‐labeled material migrated as intact interferon in polyacrylamide gels, and it was immunoprecipitated by anti‐(HuIFN‐ α )antibodies but not by anti‐(HuIFN‐ β )antibodies. The bulk of the internalized 125 I‐interferon was recovered in a particulate fraction and, on cross‐linking with disuccinimidyl suberate, a 150000‐ M r complex could be detected. The results suggest that interferon may be internalized as a complex with the receptor, which may account for the loss of the interferon‐receptors on the cell surface. This modulation of the IFN‐ α / β receptors was induced by HuIFN‐ α and HuIFN‐ β but not by HuIFN‐ γ . The recovery of the IFN‐ α / β receptors, lost upon incubation with HuIFN‐ α , took several hours and required protein synthesis. The significance of the results is discussed.