Characterization of interferon-alpha binding sites on human cell lines.

The binding sites for human interferon-alpha (IFN-alpha) have been characterized on human lymphoblastoid, melanoma, rhabdomyosarcoma, and cervical carcinoma cells. Crosslinking of iodinated-recombinant DNA-derived IFN-alpha-Con1, an analog of the known IFN-alpha subtypes, to the cell surface with disuccinimidyl suberate yielded four IFN-receptor complexes of 118, 138, 159, and 260 kD on all cell lines that specifically bind IFN-alpha. Since IFN-alpha exists in solution as monomers, dimers, and trimers, and the three lower molecular weight IFN-alpha-receptor complexes differ by the molecular weight of IFN-alpha (20 kD), this suggests that the human IFN-alpha receptor of 100 kD binds more than one molecule of IFN-alpha. The higher molecular weight complex of 260 kD may result from dimerization of the receptor. None of these complexes was observed in a rhabdomyosarcoma subclone that does not specifically bind IFN-alpha. Pretreatment of cells with trypsin abolished the formation of these complexes. Pretreatment of cells with neuraminidase did not reduce IFN-alpha binding, but increased the electrophoretic mobility of all four IFN-alpha-receptor complexes. Other glycosidases (i.e., mannosidase, beta-galactosidase, and endoglycosidase F) had no effects on IFN-alpha binding or mobility of complexes. Thus, although the IFN-alpha receptor is a glycoprotein, the glycosylated portion is apparently not part of the IFN-alpha-binding domain. The formation of IFN-alpha-receptor complexes is independent of the duration of incubation with IFN (from 5 min to 1 h at 15 degrees C).(ABSTRACT TRUNCATED AT 250 WORDS)