Abstract
Type I interferons (IFNs) bind and signal through cell surface receptors that share at least one common component. One candidate for such a component is the interfero-α receptor (IFNAR). Genetic studies have shown that the IFNAR gene product is required for response to many type I interferons. However, these studies also suggest that the IFNAR protein interacts with an additional receptor component(s) to form functionally complete type I IFN receptors. Although these genetic studies have contributed significantly to understanding the type I IFN receptors, little biochemical characterization of IFNAR and its function has been reported. To facilitate biochemical studies of the IFNAR gene product, a monoclonal antibody, GB8, recognizing the extracellular domain of IFNAR was prepared. The epitope for GB8 maps to the second extracellular domain of IFNAR between amino acids 278 and 293. GB8 identifies IFNAR in western blots of cell membranes as a broad band with molecular mass ranging from 100 to 150 kD in membranes from CHO cells overexpressing the human IFNAR gene to 136-150 kD in Daudi cell membranes. Such variations in the mean value and the range of molecular mass between IFNAR in different cell lines suggest differences in glycosylation. The majority of glycosylation is N-linked, although there may also be a small amount O-linked oligosaccharide. Deglycosylation of IFNAR in Daudi cell membranes results in a 70 kD IFNAR species, indicating that nearly half of the apparent molecular mass of Daudi cell IFNAR is contributed by carbohydrate moieties.
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