Effect of vinblastine on distribution of murine leukemia virus-derived membrane-associated antigens

The effect of vinblastine on the distribution of murine leukemia virus-derived membrane-associated antigens was examined by using the indirect immunofluorescence of 3.7% formaldehyde-fixed MJD-54 (Moloney murine leukemia virus-infected) cells. On fixed, non-drug-treated cells, p30 antigen was distributed homogeneously and diffusely over the cell membrane. When cells were incubated with 10 microM vinblastine for 1 hr before fixation, the distribution of p30 antigen was greatly changed, fluorescence now being collected into poles (cap-like formation). In contrast to this distribution pattern for p30 antigen, gp70 antigen was distributed in a micropunctate pattern on the cell surface, with or without vinblastine pretreatment. These observations indicate that the distribution patterns of p30 and gp70 membrane antigens are completely different and that they are differently controlled by cytoplasmic microtubules. In addition, because the p30 membrane antigen visualized in these studies most likely represents viral Pr65gag precursor molecules which are localized directly under and associated with the plasma membrane, these results suggest that, under special conditions of fixation, it is possible to obtain a cap-like phenomenon for cytoplasmic (internal) membrane-oriented proteins.