title: Introduction of missing enzymes into the cytoplasm of cultured mammalian cells by means of fusion-prone liposomes.
abstract: It is therefore possible to introduce enzyme-laden liposomes into two sites within the cytoplasm of cells previously lacking such enzymes. The first site is gained after enzyme-laden liposomes are phagocytosed into the lysosomal apparatus. Liposomes coated with immunoglobulins engender their own uptake by inducing the Fc receptor of phagocytic cells to launch ingestion of the vector as if it were an opsonized bacteria or virus against which the host had mounted an immune response. As for the second site, described here, involving enzyme deficiencies of the free cytosol, these may be corrected when liposomes have lysolecithin incorporated as a fusogen. The fusogen induces merger of the liposomal membrane with that of the plasma membrane presumably by virtue of the capacity of lysolecithin to engender mixed, fusion-prone micelles. Introjection of enzymes or other sequestered molecules is accomplished without access of these to external solutes, such as calcium. Consequently, uptake of enzyme cannot be due to trivial factors such as pinocytosis induced by lysolecithin or to phagocytosis per se. These two new techniques of cellular engineering now render it possible to introduce either into phagocytic or into non-phagocytic cells, enzymes or macromolecules in which these cells are genetically deficient.
mesh_terms: D002459:Cell Fusion; D002463:Cell Membrane Permeability; D003593:Cytoplasm / Q000201:enzymology*; D006801:Humans; D008081:Liposomes / Q000008:administration & dosage*; D008214:Lymphocytes / Q000201:enzymology; D010544:Peroxidases / Q000008:administration & dosage / Q000172:deficiency*; D010587:Phagocytosis
chemical_list: D008081:Liposomes; D010544:Peroxidases