Nature of the Sendai virus receptor: glycoprotein versus ganglioside

Gangliosides were compared with glycoproteins as potential receptors for Sendai virus by incorporating measured amounts of the glycoconjugates into lecithin-cholesterol liposomes and measuring binding by a hemagglutination assay with sheep erythrocytes. HeLa cell gangliosides showed no binding activity toward the virus up to 15 micrograms of sialic acid per 5 mumol of lecithin-cholesterol, whereas HeLa cell glycoproteins incorporated into similar liposomes caused avid virus binding below 1 microgram of sialic acid. These sialoglycoproteins could be separated from the bulk of cell proteins by multiple chloroform-methanol extractions. Purified rat brain gangliosides at a level of 120 micrograms of sialic acid in liposomes did not bind virus, whereas chloroform-methanol-extracted rat brain proteins caused only marginal binding. Bovine brain gangliosides differed slightly from the rat brain mixture in showing weak binding properties. Our results thus indicate that glycoproteins, rather than gangliosides, are the natural receptors for Sendai virus and that tissues differ as to the quantity of such protein receptors.