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Role of poly(ADP-ribose) polymerase in rapid intracellular acidification induced by alkylating DNA damage

By El Bachir Affar, Rashmi G. Shah, Annie-Karine Dallaire, Vincent Castonguay and Girish M. Shah

Abstract

In response to high levels of DNA damage, catalytic activation of the nuclear enzyme poly(ADP-ribose) polymerase (PARP) triggers necrotic death because of rapid consumption of its substrate β-nicotinamide adenine dinucleotide and consequent depletion of ATP. We examined whether there are other consequences of PARP activation that could contribute to cell death. Here, we show that PARP activation reaction in vitro becomes acidic with release of protons during hydrolysis of β-nicotinamide adenine dinucleotide. In the cellular context, we show that Molt 3 cells respond to DNA damage by the alkylating agent N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) with a dose-dependent acidification within 30 min. Whereas acidification by 0.15 pH units induced by 10 μM MNNG is reversed within 1 h, 100 μM MNNG-induced acidification by 0.5–0.6 pH units is persistent up to 7 h. Acidification is a general DNA damage response because H2O2 exposure also acidifies Molt 3 cells, and MNNG causes acidification in Jurkat, U937, or HL-60 leukemia cells and in PARP+/+ fibroblasts. Acidification is significantly decreased in the presence of PARP inhibitors or in PARP−/− fibroblasts, suggesting a major role for PARP activation in acidification. Inhibition of proton export through ATP-dependent Na+/H+ exchanger is another major cause of acidification. Using the pH clamp method to either suppress or introduce changes in cellular pH, we show that brief acidification by 0.5–0.6 pH units may be a negative regulator of apoptosis while permitting necrotic death of cells with extensively damaged DNA

Topics: Biological Sciences
Publisher: The National Academy of Sciences
Year: 2001
DOI identifier: 10.1073/pnas.012460399
OAI identifier: oai:pubmedcentral.nih.gov:117546
Provided by: PubMed Central
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