Association of mitochondria with intermediate filaments and of polyribosomes with cytoplasmic actin.

Anti-mitochondrial autoantibody and fluorescent derivatives of insulin stain phase-dense mitochondria in acetone fixed monolayers of fibroblasts. Double fluorochrome studies show mitochondria in close topographic association with intermediate filaments. In cells treated with vinblastine or colchicine, mitochondria are relocated in sites closely associated with coils of perinuclear intermediate filaments. In contrast, autoantibody to polyribosomes stains granules aligned in the long axis of well spread embryonic cells, in the direction of actin-containing fibrils, an arrangement that is lost in cells pretreated with the actin filament disrupting drug cytochalasin B. In more mature fibroblasts, antiribosomal antibody reacts with phase-dense rough endoplasmic reticulum and this staining pattern is not affected by cytochalasin B. The observations suggest that mitochondria are associated with intermediate filaments and that free polyribosomes, but not polyribosomes attached to rough endoplasmic reticulum, are associated with cytoplasmic actin.