| Abstract: | The effect of microtubule disruption on intracellular protein translocation and secretion of cultured human fibroblasts was studied. Experiments with fluorochrome-labeled wheat germ agglutinin showed that treatments with demecolcine or vinblastine sulfate rapidly brought about dispersal of Golgi organization. Similarly, monoclonal tubulin antibodies revealed in immunofluorescence a complete disappearance of microtubules under these conditions. Cells exposed to demecolcine or vinblastine sulfate appeared to secrete both fibronectin and other polypeptides similar to the control cells, as judged by electrophoretic analysis of the culture medium. In line with this, immunofluorescence studies of the cells, treated with the antimitotic drugs and then exposed to puromycin, showed a rapid depletion of intracellular fibronectin and collagen type III-specific staining. On the contrary, cells exposed first to monensin and then to demecolcine or vinblastine sulfate and puromycin, showed an accumulation of these proteins in vesicles in the Golgi region. The results suggest that in cultured fibroblasts microtubules do not have a direct permissive role in the intracellular translocation of the secreted proteins although they are involved in the maintenance of the Golgi apparatus. The secretory processes, however, appear to continue also in cells with dispersed Golgi organization and lacking microtubules. |
