Microinjected antibodies against the cytoplasmic domain of vesicular stomatitis virus glycoprotein block its transport to the cell surface.

Polyclonal and monoclonal antibodies were raised against a synthetic peptide containing the 15 carboxy-terminal amino acids (497-511) of vesicular stomatitis virus glycoprotein (VSV-G). The polyclonal antibodies (alpha P4) reacted with epitopes distributed along the 15-residue peptide, whereas the monoclonal antibody (P5D4) reacted with one epitope containing the five carboxy-terminal amino acids. Both types of antibodies recognized the cytoplasmic domain of VSV-G synthesized by tissue culture cells infected with the temperature-sensitive 045-VSV mutant (ts045-VSV). They recognized immature forms of VSV-G in the rough endoplasmic reticulum (RER) and Golgi complex, as well as mature VSV-G at the cell surface and in budding virus. The effect of these antibodies on intracellular transport and maturation of VSV-G was studied by microinjection. Both divalent antibodies (alpha P4 and P5D4) blocked transport of VSV-G to the cell surface. Monovalent Fab' fragments of alpha P4 (alpha P4-Fabs) also interfered with the appearance of VSV-G at the cell surface; Fab fragments of P5D4 (P5D4-Fabs), however, had no inhibitory effect. These results suggest that accessibility of a cytoplasmic domain, located within the sequence of amino acids 497-506 of the carboxy-terminal tail, is essential for transport of VSV-G to the cell surface.