Microinjection of arginase into enzyme-deficient cells with the isolated glycoproteins of Sendai virus as fusogen

A method of introducing enzymes into the cytoplasm of fibroblasts in culture is described. Erythrocytes obtained from normal and arginase-deficient individuals were loaded with arginase in vitro and fused to arginase-deficient mouse and human fibroblasts. Erythrocyte ghost-fibroblast fusion was quantified by a 14C-radioactive assay for arginase in solubilized fibroblasts. Fusion was successfully induced by Sendai virus and also by the isolated glycoproteins of Sendai virus. After fusion the arginase activity associated with the Fibroblasts was 700--1500 U of arginase/mg of cell protein; this enzyme activity was 5- to 10-times higher than that normally found in the fibroblasts. The enrichment in arginase activity indicated that between four and ten ghosts had fused per fibroblast. The use of isolated viral proteins to mediate the transfer of enzymes into cells in vivo might alleviate clinical complications inherent in the use of whole virions. The enzyme replacement technique described in this report for a hyperargininemic model cell system should be applicable to the group of inborn errors of metabolism characterized by deficiency of an enzyme normally localized in the cytoplasmic compartment of cells.