26S multicatalytic proteinase complexes decrease during the differentiation of murine erythroleukemia cells.

Changes in multicatalytic proteinase activity during differentiation were investigated using Me2SO-induced differentiation of murine erythroleukemia cells as a model. The apparent ATP-dependent multicatalytic proteinase activity decreased in the Me2SO-treated cells with ATP-dependent incorporation of [3H]diisopropyl fluorophosphate decreasing notably after Me2SO-treatment. This decrease in activity does not seem to arise from a cessation of cell-proliferation, because no significant changes in proteinase activity were observed under different culture conditions. Hydroxyapatite column chromatography was employed to analyze the form of multicatalytic proteinase. It was clearly demonstrated that the 26S form of the proteinase decrease in the differentiated cells relative to normal cells. Multicatalytic proteinase-associated proteins that bind to the proteinase in an ATP-dependent manner were purified on an anti-multicatalytic proteinase IgG conjugated column. Only a small amount of protein was recovered from the differentiated cells. These results suggest that the decrease in multicatalytic proteinase-associated proteins that occurs upon cell-differentiation abolishes the ATP-dependent activity of the proteinase.