CONCOMITANT CHANGES IN MITOCHONDRIA AND INTERMEDIATE FILAMENTS DURINGHEAT-SHOCK AND RECOVERY OF CHICKEN-EMBRYO FIBROBLASTS

Utilizing video-enhanced differential interference contrast microscopy of chicken embryo fibroblasts, we observed dramatic changes in the lo calization and morphology of mitochondria shortly after cells were sub jected to a mild heat shock. At normal temperatures mitochondria were distributed in the cell cytoplasm as elongated, tubular, and dynamic o rganelles but upon heat shock they moved to the perinuclear region and formed a tight ring of short swollen and-in some cases-fused vesicles . Vital dye staining of mitochondria with rhodamine 123 and indirect i mmunofluorescence staining with antibodies against the mitochondrial-m atrix protein, HSP 60, confirmed these results. Using cells double lab eled with antibodies to vimentin and the HSP 60 protein, we found that the changes in mitochondria were accompanied by perturbations of the intermediate filament network that we and others have reported previou sly for heat shocked cells. Microtubules remained largely unaltered by our heat shock treatment and the redistribution of intermediate filam ents and mitochondria occurred even in the presence of taxol, a microt ubule stabilizing drug. The effects of heat shock on mitochondria were reversed when cells were returned to normal temperatures and their re covery to their normal state coincided with return of normal intermedi ate filament morphology. This recovery was blocked in cells treated wi th actinomycin D during heat shock, a result indicating that a heat sh ock protein may be required for recovery. These data are consistent wi th previously published observations that mitochondria are associated with the intermediate filament network but they extend this interactio n to a cell system responding to a physiological stress normally exper ienced by the intact organism. (C) 1993 Wiley-Liss, Inc.