Vimentin in cultured chromaffin cells: an immunofluorescent, biochemical and functional study.

In tile present study we seek the presence and possible function of the intermediate filament protein vimentin in adrenomedullary chromaffin cells. Vimentin which is not present in the adrenal medulla was clearly showed up after collagenase digestion of the gland in the cultured chromaffin cells by using an immunofluorescent analysis with double cell labeling with monoclonal antibodies against vimentin and dopamine-beta-hydroxylase. Vimentin was also shown to be phosphorylated in a calcium-dependent manner by acetylcholine. The specific protein phosphatase inhibitor calyculin-A, that has been previously shown to increase vimentin phosphorylation, caused a change in the distribution of vimentin which moved from the Triton X-100 insoluble cytoskeletal preparation to the detergent soluble fraction probably as a result of modifications in filament integrity. The possible role of vimentin in secretion was in addition investigated using digitonin-permeabilized cells, in which the specific antibody for vimentin partially inhibited calcium-induced catecholamine release. These results demonstrate the induction of vimentin expression after collagenase digestion in cultured chromaffin cells and suggest that in these conditions this protein is possibly implicated in the regulation of the secretory process through a phosphorylation-dependent mechanism.