Effect of suramin on human interferon alpha binding to cell receptors

Radioiodinated human recombinant interferon alpha 88 (125I-HuIFN-alpha 88) binds to high affinity receptors of IFN sensitive Daudi cells (Burkitt lymphoma cell line). Suramin, a low molecular weight (1429), polyanionic compound at concentrations 105-175 microM completely abolished 125I-IFN-alpha 88 binding to Daudi cells at low temperature (4 degrees C). At 37 degrees C, however, its effect was only partial and depended on incubation time. Suramin also dissociated IFN-alpha 88-receptor complexes but, upon incubation of cells with IFN at 37 degrees C IFN-receptor complexes, became gradually less sensitive to suramin action. Dissociation by suramin IFN-alpha 88-receptor complexes prevented induction of (2-5)A synthetase activity and inhibited down-regulation of IFN receptors on Daudi cells. We suppose that the first reaction which represents IFN binding to the surface receptors is inhibited and dissociated by suramin, but when IFN is transferred to a tight activation complexes on the cell membrane or internalized, such complexes cannot be dissociated by suramin.