ATP-dependent regulation of cytoplasmic microtubule disassembly.

Indirect immunofluorescent staining with an antitubulin antibody was used for studying the role of ATP in the regulation of cytoplasmic microtubule disassembly. Depletion of the cellular ATP pool in cultured mouse fibroblasts with various inhibitors of energy metabolism leads to inhibition of the microtubule disassembly induced by colcemid or vinblastine. Glucose added to the inhibitor-containing incubation medium partially restores the cellular ATP content and abolishes the inhibition of microtubule disassembly. The metabolic inhibitors did not change 3Hcolcemid uptake by the cells; therefore, their action on the microtubule disassembly was not caused by the reduction in intracellular colcemid. Addition of ATP to the cytoskeleton preparations obtained by Triton X-100 treatment of the cells markedly stimulates microtubule depolymerization. This effect was specific for ATP; it was not observed in the presence of GTP, UTP, CTP, ADP, AMP, adenosine 5'-(beta, gamma-methylene)triphosphate (a nonhydrolyzable analogue of ATP), or inorganic pyrophosphate or tripolyphosphate. Therefore, depletion of the cellular ATP pool reduces the rate of microtubule disassembly whereas addition of ATP increases it. These results suggest that a certain ATP-dependent reaction most probably, phosphorylation of some of the microtubule protein(s) controls microtubule disassembly in the cells.