Increasing interest is being focused on the role of protein kinase C (PKC) in the mode of action of interferons (IFNs). Here we report that IFN-α induced a transient translocation of PKC from the cytosol to the particulate fraction of U937 cells. In contrast, after IFN-γ treatment, no significant change in PKC activity could be observed. IFN-induced changes in membrane potential were also examined by means of a potential sensitive oxonol dye and flow cytometry. Hyperpolarization was induced by both IFN-α and IFN-γ. The protein kinase inhibitor H-7 blocked the hyperpolarization induced by IFN-α but not by IFN-γ. These concordant results suggest that PKC is involved in the early signals of IFN-α but not of IFN-γ in U937 cells.
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