Sequential disassembly of the cytoskeleton in BHK21 cells infected with vesicular stomatitis virus.

The cytopathic effects of vesicular stomatitis virus (VSV) that result in the rounding of BHK21 cells have been studied. The results indicate that they are mediated by a sequential alteration in the distribution of the components of the cytoskeleton, an effect that requires the expression of the viral L protein. The constituents of the cytoskeleton of BHK21 cells were analyzed by fluorescence microscopy. Actin filaments were the first component to become disorganized, so that disassembly of stress fibers were detected 1 hr after infection. The distribution of microtubules and intermediate filaments was unchanged at 2 hr after infection; however, both these cytoskeletal elements exhibited an altered distribution at 3-4 hr after infection. Actinomycin D and cycloheximide did not cause the same effects as infection with VSV, suggesting that inhibition of host-cell gene expression was not responsible. However, viral gene expression was required, since cells infected with uv-irradiated VSV showed the same distribution of cytoskeletal constituents as mock-infected controls. Cells infected at 39.5 degrees (the nonpermissive temperature) with mutants of VSV temperature sensitive in the viral NS (ts G22), N(ts G41), M(ts 0 23), and G(ts 0 45) proteins showed the same changes in the cytoskeleton as those detected with wild-type virus. In contrast, cells infected with ts G11 (L-) showed the characteristic effect of VSV on the cytoskeleton when incubated at 34 degrees (the permissive temperature), but not when incubated at 39.5 degrees. The T-1026 R1 mutant of VSV, which has a much less dramatic effect on cell morphology than wild-type virus, also caused a less marked disruption of the cytoskeleton.