The preparation of cell fusion-inducing proteoliposomes from purified glycoproteins of HVJ (Sendai virus) and chemically defined lipids.

Abstract

Cell fusion-inducing (fusogenic) proteoliposomes of defined chemical composition were reconstituted from purified glycoproteins of hemagglutinating virus of Japan (Sendai virus) either with lipids extracted from the virus particles or with a chemically defined lipid mixture. Cell fusion reactions induced by the reconstituted system have several important characteristics similar to the virus-induced fusion reaction: fusogenic activity of the proteoliposomes depends on the presence of active fusion protein in the vesicles and, in the case of Ehrlich tumor cells, the fusion is almost completely inhibited by adding cytochalasin D to a final concentration of 4 microgram/ml. The only known difference between the original and reconstituted systems is that a greater amount of the latter is necessary for the same degree of fusogenic activity. Thus, the reconstituted system can be used as a model for the Sendai virus-induced fusion reaction. A lipid mixture (phosphatidylcholine:phosphatidylethanolamine:phosphatidylserine:sphingomyelin = 1:2:1:1, by weight, and cholesterol equimolar to the total phospholipids) similar to that of the virion was active for reconstitution, whereas a mixture containing the same composition of phospholipids but no cholesterol, and ones containing cholesterol with only a single species of phospholipid were not reconstitutively active.