A Genetic Analysis of the Caenorhabditis elegans Detoxification Response

Abstract

Oxidative damage contributes to human diseases of aging including diabetes, cancer, and cardiovascular disorders. Reactive oxygen species resulting from xenobiotic and endogenous metabolites are sensed by a poorly understood process, triggering a cascade of regulatory factors and leading to the activation of the transcription factor Nrf2 (Nuclear factor-erythroid-related factor 2, SKN-1 in ). Nrf2/SKN-1 activation promotes the induction of the phase II detoxification system that serves to limit oxidative stress. We have extended a previous genetic approach to explore the mechanisms by which a phase II enzyme is induced by endogenous and exogenous oxidants. The () mutants were isolated as defective in their ability to properly regulate the induction of a glutathione -transferase (GST) reporter. The gene was previously identified as , which encodes a homolog of the mammalian β-propeller repeat-containing protein WDR-23 Here, we identify and confirm the mutations in ,, and The gene is , an ortholog of a human gene mutated in familial hyperprolinemia. The mutation is a gain-of-function allele of The gene is , which encodes a F-box-containing protein. We demonstrate that alters the stability of WDR-23 (), a key regulator of SKN-1 (). Epistatic relationships among the mutants and their interacting partners allow us to propose an ordered genetic pathway by which endogenous and exogenous stressors induce the phase II detoxification response.

Protein Sequence Editing of SKN-1A/Nrf1 by Peptide:N-Glycanase Controls Proteasome Gene Expression

“…Upregulation of gst-4 p ::gfp during oxidative stress caused by juglone or depletion of transketolase (TKT-1) is not affected in skn-1a(mg570) mutant animals ( Figures 4A and 4B). wdr-23 negatively regulates skn-1-dependent oxidative stress responses (Choe et al, 2009;Fukushige et al, 2017;Tang and Choe, 2015), but activation of gst-4 p ::gfp by wdr-23(RNAi) is unaltered in skn-1a(mg570) mutants ( Figure 4C). These data indicate that the transcriptional response to oxidative stress does not require SKN-1A.…”

“…Expression of truncated SKN-1A[cut] causes strong upregulation of gst-4 p ::gfp, reminiscent of the induction caused by loss of WDR-23, a negative regulator of the skn-1-dependent oxidative stress response (Choe et al, 2009). Analysis of skn-1 gainof-function alleles suggests that inhibition by WDR-23 requires an N-terminal region of SKN-1C (Fukushige et al, 2017;Tang and Choe, 2015). The SKN-1A[cut] protein, which lacks this N-terminal domain, likely drives constitutive activation of gst-4 p ::gfp by escaping inhibition by WDR-23.…”

Transcriptome Analysis of the Nematode Caenorhabditis elegans in Acidic Stress Environments

“…It was reported that exposure of C. elegans to hyperosmotic conditions can also lead to upregulation of the transcriptome of the detoxification pathway genes (glycosyltransferase, cytochrome P450, glutathione S-transferase, and ABC transporters), and their upregulations were partially dependent on SKN-1 (Dodd et al, 2018). skn-1 (RNAi) reduces the expression of many phase II detoxification genes, especially within the gst gene class (Fukushige et al, 2017;Dodd et al, 2018). There are also substances that induce upregulation of the detoxification pathway genes independent of skn-1, for example, t-BOOH (tert-Butyl hydroperoxide), a stable lipid-soluble hydrogen peroxide that attacks lipids and proteins (Oliveira et al, 2009).…”

Transcriptome analysis of the NematodeCaenorhabditis elegansin acidic stress environments

“…It was reported that exposure of C. elegans to hyperosmotic conditions can also lead to up-regulation of the transcriptome of the detoxification pathway gene (glycosyltransferase, cytochrome P450, glutathione S-transferase, and ABC transporters), and their up-regulation were partially dependent on SKN-1 (Dodd et al, 2018). skn-1 (RNAi) reduces the expression of many phase II detoxification genes, especially within the gst gene class (Dodd et al, 2018;Fukushige et al, 2017).There are also substances that induce upregulation of the detoxification pathway genes independently of skn-1, for example, t-BOOH (tert-Butyl hydroperoxide), a stable lipid-soluble hydrogen peroxide that attacks lipids and proteins (Oliveira et al, 2009). In our study, the expression level of skn-1 do not show significantly difference among different pH conditions ( Supplementary Figure 3).…”