Intracellular acidification during apoptosis can occur in the absence of anucleus

During apoptosis, DNA fragmentation and intracellular acidification occur c oncurrently, Previous results have shown that intracellular acidification i s not required for DNA fragmentation, while the alternative, that acidifica tion is a consequence of DNA fragmentation was analyzed here. To obviate th e requirement of any nuclear function in acidification, apoptosis was induc ed by staurosporine in cytoplasts made from the breast tumor cell line MDA- MB-468. Both cells and cytoplasts demonstrated externalization of phosphati dylserine that was prevented by the pan-caspase inhibitor zVAD-fluoromethyl ketone or by expression of Bcl-2, Intracellular acidification was observed in both cells and cytoplasts and this was also inhibited by both zVAD-fluor omethylketone and Bcl-2, These results show that intracellular acidificatio n and DNA fragmentation are independent consequences of caspase action duri ng apoptosis, (C) 1999 Academic Press.