Reduction of transferrin receptor expression by interferon gamma in a human cell line sensitive to its...

Interferon gamma (IFN gamma) reduced 125I-transferrin binding to WISH cells which are sensitive to its antiproliferative effect. IFN gamma did not affect transferrin binding to Daudi cells or phytohemagglutinin-stimulated human lymphocytes, neither of which respond to its antigrowth action. Scatchard analyses of the equilibrium binding of 125I-transferrin to WISH cells exposed to IFN gamma revealed a decrease in the number of cell surface receptors but no change in the apparent association constant compared with control cells. When 125I-transferrin binding was measured using detergent-extracted cells, the IFN-induced reduction of binding was smaller than with intact cells. This suggests that in WISH cells, IFN gamma not only reduced the total number of transferrin receptors, but also modified the process of receptor internalization and recycling. Labeling of newly synthesized receptors with [35S]-methionine indicated that a reduction in the biosynthesis might account for the decrease in the total number of transferrin receptors in IFN gamma-treated cells. Our results suggest that the antigrowth effect of IFN gamma is at least partly due to its inhibitory action on transferrin receptor expression leading to iron starvation.