Microtubule involvement in the intracellular dynamics for gene transfection mediated by cationic liposomes

The effects of microtubule polymerization on liposome-mediated gene transfe ction were investigated by confocal laser scanning microscopy in target liv ing cells. Both nocodazole and taxol apparently increased the efficiency of gene transfection. Lipofection with fluorescence-labeled cationic liposome s in a COS-7 cell expressing yellow fluorescent protein (YFP)-tagged tubuli n revealed that the liposomes were transported along microtubules to lysoso mes which are colocalized with the microtubule organizing center (MTOC). No codazole disrupted microtubules and produced a uniform distribution of YFP- tagged tubulin in the cytoplasm. Under these conditions, both liposomes and lysosomes were scattered throughout the cytoplasm and they did not colocal ize. In the presence of taxol, microtubules were stabilized and several foc al regions, like the MTOC, were formed. Lysosomes resided around the nucleu s, while liposomes were trapped in microtubules. Under these conditions, ne ither liposomes nor DNA colocalized with lysosomes. These results demonstra ted that the liposome-DNA complexes are transported to lysosomes by a micro tubule-mediated pathway, and the effects of nocodazole and taxol on transfe ction efficiency can be explained by failure of the transport of the liposo me-DNA complexes to lysosomes where DNAs are degraded.