The extent of involvement of carbohydrate structures in the mechanism of action of a and [j-interferon (IFN-a, IFN-P) is undefined. In this report we examine the role of complex-type N-linked oligosaccharides in the response to these interferons. The response of mouse leukemia L1210S cells, grown in the prcsence of swainsonine, an inhibitor of Golgi mannosidase I1 [Tulsiani, D. R. P., Harris, T. M. and Touster, 0. (1982) J . Bid. Clzern. 257, 7936-7939; Elbein A. D., Solf, R., Dorling, P. R. and Vosbeck, K. (1981) Proc. Nut1 Acud. Sci. USA 78, 7393-73971, to mouse IFN-a/& both with respect to antiviral and antigrowth effects, remains intact in spite of the total absence of complex-type N-linked oligosaccharides. Also, there is no difference in the response to human I F N -j of a parental Chinese hamster ovary cell line and a mutant lacking P-N-acetylglucosaminyltransferase 1 and therefore unable to synthesize complex-type N-linked oligosaccharides [Stanley, P., Callibot, V. and Siminovitch, L. (1975) CeIf 6, 121 -1281. These results are significant in permitting the conclusion that the carbohydratespecific binding of IFN-a and IFN-/3 to gangliosides cannot be due to a similarity of the ganglioside carbohydrate to that of a glycoprotein containing a complex-type N-liked oligosaccharide.Action of a-interferon (IFN-a) and /%interferon (IFN-fi) appears to be initiated at the surface of target cells. The nature of the interaction between the cell surface and these interferons, that results in a biological response, remains unclarified. Target cells have been shown to have saturable, high-affinity binding sites, which recognize both IFN-a and IFN-[j [l -81. Additional evidence suggests that high-affinity binding is due to an IFNalP-specific protein receptor on the cell surface [9 -1 I]. Other components of the plasma membrane, gangliosides, bind IFN-a and IFN-P 112 -141. In order to test whether the binding of IFN-a and IFN-p to gangliosides could be attributed to a similarity of carbohydrate structure between the gangliosides and a glycoprotein receptor for interferon, we have investigated the role of complex-type N-linked oligosaccharides in the interferon response. Our approach was to examine the activity of IFN-a/J on target cells which lack N-linked complex-typc oligosaccharides. We have used mouse L 1210s cells grown in the presence of swainsonine, an inhibitor of Golgi mannosidase 11 [I 5, 161, which are completely inhibited in the biosynthesis of this class of oligosaccharides, and a mutant Chinese hamster ovary cell line, which lacks N-acetylglucosaminyltransferase I, the enzyme essential for the synthesis of these oligosaccharides [37].
EXPERIMENTAL PROCEDURE
Muter i u Is
Ce/l lines und cell cullurcThe L1210 mouse leukemia cell line was clone S6 from Dr. Ion Gresser (Institut de Recherches Scientifiques sur le Cancer, Villejuif, France). This cell line was recloned in soft agar and a freshly isolated clone was used for all experiments. The L1210S cell line was maintained in culture by periodically res...