Paramyxovirus cell fusion activity

It has been known for some time that different viruses have different effects on cell membranes. In particular, the enveloped viruses can cause early cell fusion as they enter the host cell or late cell fusion after replication of the virus. These phenomena apply particularly to the paramyxoviruses and have been dubbed fusion from without and fusion from within (Bratt and Gallaher, 1969). Other enveloped viruses can produce similar but usually less striking effects on cell fusion. Nonenveloped viruses can also cause drastic changes in cell membranes, usually resulting in alteration in the permeability barrier of the cell membrane. Still other viruses, or the same viruses under different conditions, can alter in a more subtle way the active or passive transport mechanisms of cells. Under some conditions, some viruses even stimulate the formation of cell membranes by inducing augmented synthesis of cellular membrane lipids. 

The paramyxoviruses, largely because of their profound cell-fusing activity, have served as an important model of membrane perturbation by viruses. During Sendai virus-mediated fusion of mouse ascites cells, Pasternak and Micklem (1973) detected loss of intracellular metabolites coincident with inhibition of their accumulation from the medium. This failure to maintain selective permeability did not occur at 0°C and was unaffected by cytochalasin B which inhibits fusion by the virus. Chick embryo fibroblasts infected with Newcastle disease virus were found to release cellular enzymes, such as lactate dehydrogenase, glutamic oxaloacetic transaminase, and lysosomal enzymes (Katzman and Wilson, 1974). These cells also became... 

Scheid, A., and Choppin, P. W., 1974, Identification of biological activities of paramyxovirus glycoproteins. Activation of cell fusion, hemolysis and infectivity by proteolytic cleavage of an inactive precursor protein of Sendai virus. Virology 57 475. 

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