Opposite effects of microtubule-stabilizing and microtubule-destabilizing drugs on biogenesis of mitochondria in mammalian cells

Distribution of mitochondria as well as other intracellular organelles in m ammalian cells is regulated by interphase microtubules. Here, we demonstrat e a role of microtubules in the mitochondrial biogenesis using various micr otubule-active drugs and human osteosarcoma cell line 143B cells and rat li ver-derived RL-34 cells. Depolymerization of microtubules by nocodazole or colchicine, as well as 2-methoxyestradiol, a natural estrogen metabolite, a rrested asynchronously cultured cells in G(2)/M phase of cell cycle and at the same time inhibited the mitochondrial mass increase and mtDNA replicati on, These drugs also inhibited the mitochondrial mass increase in the cells that were synchronized in cell cycle, which should occur during G(1) to G( 2) phase progression in normal conditions. However, stabilization of microt ubules by taxol did not affect the proliferation of mitochondria during the cell cycle, yet a prolonged incubation of cells with taxol induced an abno rmal accumulation of mitochondria in cells arrested in G(2)/M phase of cell cycle. Taxol-induced accumulation of mitochondria was not only demonstrate d by mitochondria-specific fluorescent dyes but also evidenced by the exami nation of cells transfected with yellow fluorescent protein fused with mito chondrial targeting sequence from subunit VIII of human cytochrome c oxidas e (pEYFP) and by enhanced mtDNA replication, Two subpopulations of mitochon dria were detected in taxol-treated cells: mitochondria with high Delta Psi (m), detectable either by Mito Tracker Red CMXRos or by Green FM, and thos e with low Delta Psim, detectable only by Green FM. However, taxol-induced increases in the mitochondrial mass and in the level of acetylated a-tubuli n were abrogated by a cotreatment,vith taxol and nocodazole or taxol and co lchicine. These data strongly suggest that interphase microtubules may be e ssential for the regulation of mitochondrial biogenesis in mammalian cells.