Intracellular Type A Retrovirus Movement Associated with an Intact Microtubule System

Abstract

Intracytoplasmic type A particles known to be precursors to type B retroviruses in murine, hamster and marsupial cells are closely associated with microtubules and microtubule organizing centers. The active participation of microtubules in the intracellular transport of the particles to the cell surface was examined in NIH 3T3 cells infected with M432 virus using vincristine sulfate (VCR) as inhibitor of microtubule polymerization. The release of virus at different times after exposure to VCR was quantified by reverse transcriptase determinations of cell supernatants and by EM quantification of the number of virions at the cell surface using freeze-dried whole cell replicas. These studies indicate that VCR inhibits both microtubule polymerization and virus release, and thus suggest that intact cytoplasmic microtubules are necessary for intracellular transport and release of virus.