Genomic instability induced by mutant succinate dehydrogenase subunit D (SDHD) is mediated by O2-• and H2O2

Abstract

SDHD mutations are associated with human cancers but the mechanisms that may contribute to transformation are unknown. The hypothesis that mutations in SDHD increase levels of superoxide leading to genomic instability was tested using site-directed mutagenesis to generate a truncated SDHD cDNA that was expressed in Chinese hamster fibroblasts. Stable expression of mutant SDHD resulted in 2-fold increases in steady-state levels of superoxide that were accompanied by a significantly increased mutation rate as well as a 70-fold increase in mutation frequency at the hprt locus. Over expression of MnSOD or treatment with polyethylene glycol conjugated (PEG)-catalase suppressed mutation frequency in SDHD mutant cells by 50% (p < 0.05). Simultaneous treatment with PEG-catalase and PEG-SOD suppressed mutation frequency in SDHD mutant cells by 90% (p < 0.0005). Finally, 95% depletion of glutathione using L-buthionine-[S,R]-sulfoximine (BSO) in SDHD mutant cells caused a 4-fold increase in mutation frequency (p < 0.05). These results demonstrate that mutations in SDHD cause increased steady-state levels of superoxide which significantly contributed to increases in mutation rates and frequency mediated by superoxide and hydrogen peroxide. These results support the hypothesis that mutations in SDHD may contribute to carcinogenesis by increasing genomic instability mediated by increased steady-state levels of reactive oxygen species.

Manganese ions induce H2O2 generation at the ubiquinone binding site of mitochondrial complex II

“…Based on studies in Saccharomyces cerevisiae [52,53] the Q-site has been proposed as the site for ROS production and a mixed contribution of sites II F and II Q was suggested for complex II from the parasitic nematode Ascaris suum [54]. While site II Q as the main ROS source seems likely for some mutants [55][56][57][58], mechanistic studies and considerations support the view that the bound reduced flavin (FADH 2 ), i.e. site II F , is the main ROS generator in SQRs and QFRs [24,31,51,59].…”

Epithelial To Mesenchymal Transition in Breast Cancer Metastasis: Mitochondria Take the Center Stage

“…Defects in mitochondrial enzymes, Succinate Dehydrogenase (SDH) [72][73][74][75][76][77][78][79][80][81][82][83][84] fumarate hydratase (fumarase) [85][86][87][88][89][90][91] (IDH) [92][93][94][95][96][97][98][99][100][101][102][103][104][105][106][107][108] account for deregulated bioenergetics and tumor cells' mitochondrial dysfunction favoring tumor progression. Moreover accumulation of these metabolites has been shown to cause epigenetic alterations by influencing the activities of histone and DNA methylases [109][110][111].…”

Models of parent-of-origin tumorigenesis in hereditary paraganglioma

“…In the former role it oxidizes succinate to fumarate, while in the latter it reduces ubiquinone to ubiquinol, contributing to the generation of ATP by oxidative phosphorylation. SDH inactivation induces an accumulation of succinate [14][15][16] or the generation of reactive oxygen species (ROS) [17][18][19][20][21][22][23], leading to inhibition of ␣-ketoglutaratedependent HIF prolyl hydroxylases and the activation of hypoxia inducible factor (HIF).…”