Abstract
WldS is a fusion protein with NAD synthesis activity, and has been reported to protect axonal and synaptic compartments of neurons from various mechanical, genetic and chemical insults. However, whether WldS can protect non-neuronal cells against toxic chemicals is largely unknown. Here we found that WldS significantly reduced the cytotoxicity of bipyridylium herbicides paraquat and diquat in mouse embryonic fibroblasts, but had no effect on the cytotoxicity induced by chromium (VI), hydrogen peroxide, etoposide, tunicamycin or brefeldin A. WldS also slowed down the death of mice induced by intraperitoneal injection of paraquat. Further studies demonstrated that WldS markedly attenuated mitochondrial injury including disruption of mitochondrial membrane potential, structural damage and decline of ATP induced by paraquat. Disruption of the NAD synthesis activity of WldS by an H112A or F116S point mutation resulted in loss of its protective function against paraquat-induced cell death. Furthermore, WldS delayed the decrease of intracellular NAD levels induced by paraquat. Similarly, treatment with NAD or its precursor nicotinamide mononucleotide attenuated paraquat-induced cytotoxicity and decline of ATP and NAD levels. In addition, we showed that SIRT1 was required for both exogenous NAD and WldS-mediated cellular protection against paraquat. These findings suggest that NAD and SIRT1 mediate the protective function of WldS against the cytotoxicity induced by paraquat, which provides new clues for the mechanisms underlying the protective function of WldS in both neuronal and non-neuronal cells, and implies that attenuation of NAD depletion may be effective to alleviate paraquat poisoning.
Highlights
The Wallerian degeneration slow (WldS) mice, a spontaneous mutant mouse strain, exhibit significant neuroprotection of axons and synapses from various neurodegenerative stimuli including mechanical, genetic or chemical injury [1,2,3,4]
We found that WldS failed to alleviate reactive oxygen species (ROS) upregulation induced by paraquat, which is consistent with our observation that WldS could not protect the cytotoxicity induced by the oxidative stress inducer chromium (VI) or hydrogen peroxide
Cell viability was determined by MTT assay. **p,0.01 versus SIRT1+/+WldS-/- mouse embryonic fibroblasts (MEFs) treated without nicotinamide adenine dinucleotide (NAD) for 20 h, ##p,0.01 versus SIRT1+/+WldS-/- MEFs treated with NAD for 20 h, Student’s t-test. (B) Exogenous NAD attenuated the decline of ATP levels caused by paraquat through SIRT1
Summary
The Wallerian degeneration slow (WldS) mice, a spontaneous mutant mouse strain, exhibit significant neuroprotection of axons and synapses from various neurodegenerative stimuli including mechanical, genetic or chemical injury [1,2,3,4]. Genetic analysis has attributed this protective activity to the expression of a fusion protein, named WldS, which is composed of the N-terminal 70 amino acids of ubiquitin fusion degradation protein 2a (Ufd2a, E6.3.2.19), a ubiquitin assembly protein, and the full length of nicotinamide mononucleotide adenylyltransferase 1 (Nmnat, E2.7.7.1), an enzyme that can directly catalyze the synthesis of nicotinamide adenine dinucleotide (NAD) [5,6]. Both Nmnat activity and the short N-terminal were shown to have contributions to WldS-mediated full axon protective effect [3,7]. Whether exogenously provided NAD or overexpression of NAD biosynthetic enzymes can reduce paraquat-induced cytotoxicity is still unclear
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
