A non-filamentous configuration of intermediate-sized filament proteins in Drosophila Kc tissue culture cells.

Using monoclonal antibodies against the major intermediate filament (10 nm) cytoskeletal proteins of Drosophila tissue culture cells, we showed by indirect immunofluorescence and immuno-electron microscopy that this cytoskeletal material also occurs in a non-filamentous configuration. Patches of fine granular material are detected in the cytoplasm of Kc cells but are absent in another Drosophila cell line (Schneider, line 2). These patches are surrounded by membranes with bound ribosomes, resembling endoplasmic reticulum, and are found throughout the cytoplasm. We suggest that these aggregates are caused by overproduction of intermediate filament material in the Kc cell line.