An Oxidized Purine Nucleoside Triphosphatase, MTH1, Suppresses Cell Death Caused by Oxidative Stress

Abstract

MTH1 hydrolyzes oxidized purine nucleoside triphosphates such as 8-oxo-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP) and 2-hydroxy-2'-deoxyadenosine 5'-triphosphate (2-OH-dATP) and thus protects cells from damage caused by their misincorporation into DNA. In the present study, we established MTH1-null mouse embryo fibroblasts that were highly susceptible to cell dysfunction and death caused by exposure to H2O2, with morphological features of pyknosis and electron-dense deposits accumulated in mitochondria. The cell death observed was independent of both poly(ADP-ribose) polymerase and caspases. A high performance liquid chromatography tandem mass spectrometry analysis and immunofluorescence microscopy revealed a continuous accumulation of 8-oxo-guanine both in nuclear and mitochondrial DNA after exposure to H2O2. All of the H2O2-induced alterations observed in MTH1-null mouse embryo fibroblasts were effectively suppressed by the expression of wild type human MTH1 (hMTH1), whereas they were only partially suppressed by the expression of mutant hMTH1 defective in either 8-oxo-dGTPase or 2-OH-dATPase activity. Human MTH1 thus protects cells from H2O2-induced cell dysfunction and death by hydrolyzing oxidized purine nucleotides including 8-oxo-dGTP and 2-OH-dATP, and these alterations may be partly attributed to a mitochondrial dysfunction.

Suppression of mutagenesis by 8-hydroxy-2′-deoxyguanosine 5′-triphosphate (7,8-dihydro-8-oxo-2′-deoxyguanosine 5′-triphosphate) by human MTH1, MTH2, and NUDT5

“…Nakabeppu and his colleagues reported that both the 8-OH-dGTPase and 2-OH-dATPase activities of MTH1 contributed to the suppression of H 2 O 2 -induced mitochondrial dysfunction and cell death [37].…”

Two distinct pathways of cell death triggered by oxidative damage to nuclear and mitochondrial DNAs

“…Z-VAD-fmk efficiently suppressed staurosporine-induced cell death, which is dependent on caspases (Yoshimura et al, 2003), but did not suppress menadione-induced death (Supplementary Figure S4). We thus concluded that the menadione-induced cell death was independent of caspase activity.…”

“…No alteration in the nuclear structure was observed (data not shown), whereas mitochondrial cristae in OGG1-null and Nu-hOGG1 MEFs were highly degenerated and electron-dense deposits (EDDs), which are the hallmark of mitochondrial dysfunction under oxidative damage (Yoshimura et al, 2003), had accumulated in À/À MEFs, with a P-value o0.05. (B) Structural comparison of hOGG1 proteins.…”

“…MTH1-null mice exhibited a strong accumulation of 8-oxoG in mtDNA of striatal nerve terminals of dopamine neurons, accompanied by the increased degeneration of these terminals after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration (Yamaguchi et al, 2006). Furthermore, in MTH1-null mouse embryonic fibroblasts (MEFs), accumulation of 8-oxoG in cellular DNA was induced by H 2 O 2 , resulting in mitochondrial dysfunction and finally cell death (Yoshimura et al, 2003). However, it is not known which form of DNA was responsible for such cell death, whether nDNA or mtDNA or both, nor is it known how the death order was executed.…”

Proteomic profiling of small-molecule inhibitors reveals dispensability of MTH1 for cancer cell survival

“…3b), even though these compounds displayed the same degree of MTH1-inhibitory activities as NPD7155 and NPD9948 in vitro (Supplementary Table S1). It has been reported that MTH1 plays a crucial role in preventing incorporation of oxidized nucleotides into nuclear and mitochondrial DNA, allaying subsequent DNA damage 35 . Therefore, we examined the effects of our MTH1 inhibitors on 8-oxo-2ʹ -deoxyguanosine (8-oxo-dG) levels in DNA.…”