Localization and quantitation of hsp84 in mammalian cells.

In order to investigate the function of heat shock protein 84 (hsp84) we have isolated the protein from mouse neuroblastoma cells and raised a polyclonal antiserum which was affinity-purified. The specificity of the antibody was established by immunoprecipitation and immunoblotting. Immunofluorescence studies revealed both a cytoplasmic and a nuclear localization of hsp84 in five different mammalian cell lines (mouse neuroblastoma cells and fibroblasts, rat hepatoma cells, and HeLa cells). In none of the five cell lines were found significant differences in the total cellular levels of hsp84 before and immediately after a heat shock (4 h, 42 degrees C) by immunoblot quantification. Furthermore after heat shock the fluorescence of anti-hsp84-labeled nuclei was increased relative to that of the surrounding cytoplasm. The increased fluorescence disappeared upon reincubation at 37 degrees C. The heat-induced increase in contrast between cytoplasmic and nuclear fluorescence could be explained by a combination of three factors: (a) decrease in nuclear projection area, (b) increase in cytoplasmic projection area, and (c) translocation of hsp84. The contribution of these factors to the increase after heat treatment was different for the cell lines.