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Single high affinity binding of interferon α2 to receptors on human lymphoblastoid cells: Internalization and inactivation of receptors

✍ Scribed by Connie R. Faltynek; Sarah McCandless; Corrado Baglioni

Publisher
John Wiley and Sons
Year
1985
Tongue
English
Weight
901 KB
Volume
123
Category
Article
ISSN
0021-9541

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✦ Synopsis

The interaction of human recombinant interferon (rlFN) a2 with its receptor on lymphoblastoid cells was studied using competitive displacement binding. The data were analysed with the LIGAND program, which tests their fit to one-site or multiple binding site models. The binding at 4 O and 37OC fits a one-site model, with a similar KD for both IFN-sensitive and resistant cells. Binding at 37OC to Daudi cells at high density fits artifactually a two-site model only when t h e receptor concentration is close to that of the KD. The binding of IFN to its receptor, therefore, follows a simple bimolecular interaction. Furthermore, IFN-sensitive and resistant cells internalize IFN at similar rates. We have examined whether IFN receptors are also internalized and whether they subsequently recycle to the cell surface. By measuring cell surface and total receptors, we have observed that after 2 h treatment with IFN total receptors remain constant whereas cell surface receptors decrease. After prolonged treatment with IFN, however, there is a loss of total receptors. By inactivating cell surface receptors with proteinase K, we have shown that a fraction of cell surface receptors becomes resistant to inactivation and is apparently internalized. Moreover, experiments which measure IFN receptors either during incubation in the presence of IFN or after IFN has been removed from the medium, show that receptors do not recycle to the cell surface after internalization. The addition of monensin, a drug which has been shown to inhibit receptor recycling, has no effect on the loss of IFN receptors.

The initial event in the mechanism of action of interferon (IFN) is its binding to cell surface receptors (for reviews see Aguet and Mogensen, 1983; Faltynek and Baglioni, 1984). The binding of labeled human IFN-a to

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