HSCARG Inhibits NADPH Oxidase Activity through Regulation of the Expression of p47phox

Abstract

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase catalyzes the transfer of electrons from NADPH to O2, which is the main source of reactive oxygen species (ROS) in nonphagocytic cells. Excess ROS are toxic; therefore, keeping ROS in homeostasis in cells can protect cells from oxidative damage. It is meaningful to further understand the molecular mechanism by which ROS homeostasis is mediated. Human protein HSCARG is a newly identified oxidative sensor and a negative regulator of NF-κB. Here, we find that HSCARG represses the cellular ROS generation through inhibiting mRNA and protein expression of p47phox, a subunit of NADPH oxidase. In contrast, shRNA-mediated HSCARG knockdown increases endogenous p47phox expression level. And HSCARG has no obvious effect on ROS production in p47phox-depleted cells. Furthermore, HSCARG regulates p47phox through inhibition of NF-κB activity. Our findings identify HSCARG as a novel regulator in regulation of the activity of NADPH oxidase and ROS homeostasis.

Cellular redox sensor HSCARG negatively regulates the translesion synthesis pathway and exacerbates mammary tumorigenesis

“…Previous studies revealed that HSCARG inhibits cellular ROS generation, suggesting a potential tumor suppressor role of HSCARG. Mechanistically, HSCARG impairs the expression of NCF1, a subunit of NADPH oxidase, through repressing NF-kappaB activity in the cytoplasm (21). Here we found that in contrast to WT HSCARG, the NES mutant 272A4, which accumulated in the nucleus and down-regulated the TLS pathway more efficiently, had no significant suppressive effects on ROS and NCF1 levels (SI Appendix, Fig.…”

“…S10 A and B and S12E). Apart from regulating the TLS pathway, HSCARG has also been reported to prevent overproduction of NO and ROS, which promote cell resistance against oxidative stress (20,21). As these functions of HSCARG depend on its interaction with AS and inhibition of NF-kappaB activity in the cytoplasm, the nuclear accumulated HSCARG NES mutant 272A4 had no significant influence on ROS generation (SI Appendix, Fig.…”

“…Decreases in the NADPH/NADP + ratio lead to disaggregation of HSCARG dimers into monomers and promote the nuclear localization of HSCARG (15,18), while a nuclear export signal (NES) in the C terminus of HSCARG mediates its transport from the nucleus to the cytoplasm (19). As a cellular redox sensor protein, HSCARG prevents overproduction of nitric oxide (NO) and reactive oxygen species (ROS) through inhibiting the catalytic activity of argininosuccinate synthetase (AS) and down-regulating the expression of NADPH oxidase subunit NCF1 (p47phox) (20,21). Recently, it has been revealed that HSCARG also functions in innate immunity and DDR.…”

The regulation of the oxidative phase of the pentose phosphate pathway: New answers to old problems

“…In this way, the possibility to form more potent ROS, such as peroxynitrite, is reduced. This would contribute to reduce the effectiveness of NO synthesis, as commented above, which would be diverted to other metabolic actions . Therefore, the reductive power is preserved and, at the same time, possible NO actions are enhanced.…”

“…AS release from HSCARG allows its activation and the rise of NO production. A blocking of NADPH oxidase (p47phox) takes place simultaneously, reducing the synthesis of the superoxide ion . [Color figure can be viewed in the online issue, which is available at http://wileyonlinelibrary.com.…”