Putative association of mitochondria with a subpopulation of intermediate-sized filaments in cultured human skin fibroblasts.

Cultured cell Triton cytoskeletons enriched in intermediate filaments by extraction in high and low salt show, in addition to known intermediate-filament proteins and actin, a few other tenaciously bound polypeptides. An antibody raised against one of these polypeptides (IEF 24) is shown to react specifically with mitochondria of different cell types. With methanol-acetone fixation, required for the antibody reaction, the characteristically long mitochondria of human skin fibroblasts fragment into strings of beads, as identified by antibody staining in the light microscope and whole-mount electron microscopy. From the colinear organization of these beads, their codistribution with the intermediate-filament network and their retention in salt-extracted cytoskeletons, it is suggested that a subpopulation of the intermediate filaments can serve as an anchorage site for mitochondria.