Cloning and expression analysis of Drosophila extracellular Cu Zn superoxide dismutase

Therapeutic potential of Lingjiao Gouteng decoction in acute alcohol intoxication and alcohol-induced brain injury involving the RhoA/ROCK2/NF-κB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Alcohol misuse persists as a prevalent societal concern and precipitates diverse deleterious consequences, entailing significant associated health hazards including acute alcohol intoxication (AAI). Binge drinking, a commonplace pattern of alcohol consumption, may incite neurodegeneration and neuronal dysfunction. Clinicians tasked with managing AAI confront a dearth of pharmaceutical intervention alternatives. In contrast, natural products have garnered interest due to their compatibility with the human body and fewer side effects. Lingjiao Gouteng decoction (LGD), a classical traditional Chinese medicine decoction, represents a frequently employed prescription in cases of encephalopathy, although its efficacy in addressing acute alcoholism and alcohol-induced brain injury remains inadequately investigated.

AIM OF THE STUDY

To investigate the conceivable therapeutic benefits of LGD in AAI and alcohol-induced brain injury, while delving into the underlying fundamental mechanisms involved.

MATERIALS AND METHODS

We established an AAI mouse model through alcohol gavage, and LGD was administered to the mice twice at the 2 h preceding and 30 min subsequent to alcohol exposure. The study encompassed the utilization of the loss of righting reflex assay, histopathological analysis, enzyme-linked immunosorbent assays, and cerebral tissue biochemical assays to investigate the impact of LGD on AAI and alcohol-induced brain injury. These assessments included a comprehensive evaluation of various biomarkers associated with the inflammatory response and oxidative stress. Finally, RT-qPCR, Western blot, and immunofluorescence staining were carried out to explore the underlying mechanisms through which LGD exerts its therapeutic influence, potentially through the regulation of the RhoA/ROCK2/NF-κB signaling pathway.

RESULTS

Our investigation underscores the therapeutic efficacy of LGD in ameliorating AAI, as evidenced by discernible alterations in the loss of righting reflex assay, pathological analysis, and assessment of inflammatory and oxidative stress biomarkers. Furthermore, the results of RT-qPCR, Western blot, and immunofluorescence staining manifest a noteworthy regulatory effect of LGD on the RhoA/ROCK2/NF-κB signaling pathway.

CONCLUSIONS

The present study confirmed the therapeutic potential of LGD in AAI and alcohol-induced brain injury, and the protective effects of LGD against alcohol-induced brain injury may be intricately linked to the RhoA/ROCK2/NF-κB signaling pathway.

Orthologs of NOX5 and EC-SOD/SOD3: dNox and dSod3 Impact Egg Hardening Process and Egg Laying in Reproductive Function of Drosophila melanogaster

The occurrence of ovarian dysfunction is often due to the imbalance between the formation of reactive oxygen species (ROS) and the ineffectiveness of the antioxidative defense mechanisms. Primary sources of ROS are respiratory electron transfer and the activity of NADPH oxidases (NOX) while superoxide dismutases (SOD) are the main key regulators that control the levels of ROS and reactive nitrogen species intra- and extracellularly. Because of their central role SODs are the subject of research on human ovarian dysfunction but sample acquisition is low. The high degree of cellular and molecular similarity between Drosophila melanogaster ovaries and human ovaries provides this model organism with the best conditions for analyzing the role of ROS during ovarian function. In this study we clarify the localization of the ROS-producing enzyme dNox within the ovaries of Drosophila melanogaster and by a tissue-specific knockdown we show that dNox-derived ROS are involved in the chorion hardening process. Furthermore, we analyze the dSod3 localization and show that reduced activity of dSod3 impacts egg-laying behavior but not the chorion hardening process.

Superoxide dismutase: a key target for the neuroprotective effects of curcumin

Over the past few years, the prevalence of neurodegenerative diseases (NDD) has increased dramatically. The community health system is burdened by the high healthcare costs associated with NDD. Superoxide dismutase (SOD) is a type of metalloenzyme that possesses a distinct characteristic of protecting the body from oxidative stress through antioxidants. In this way, SOD supplementation may activate the endogenous antioxidant mechanism in various pathological conditions and could be used to neutralize free radical excess. Several factors are responsible for damaging DNA and RNA in the body, including the overproduction of reactive species, particularly reactive oxygen species (ROS) and reactive nitrogen species (RNS). Excessive ROS/RNS have deleterious effects on mitochondria and their metabolic processes, mainly through increased mitochondrial proteins, lipids and DNA oxidation. Studies have shown that oxidative stress is implicated in the etiology of many diseases, including NDD. It is thought that anti-inflammatory compounds, particularly phytochemicals, can interfere with these pathways and regulate inflammation. Extensive experimental and clinical research has proven that curcumin (Cur) has anti-inflammatory and anti-neurologic properties. In this review, we have compiled the available data on Cur's anti-inflammatory properties, paying special attention to its therapeutic impact on NDD through SOD.

Assessing Curcumin Uptake and Clearance and Their Influence on Superoxide Dismutase Activity in Drosophila melanogaster

While normal levels of reactive oxygen and nitrogen species (RONS) are required for proper organismal function, increased levels result in oxidative stress. Oxidative stress may be managed via the scavenging activities of antioxidants (e.g., curcumin) and the action of enzymes, including superoxide dismutase (SOD). In this work, the uptake and clearance of dietary curcuminoids (consisting of curcumin, demethoxycurcumin, and bisdemethoxycurcumin) was assessed in Drosophila melanogaster larvae following chronic or acute exposure. High levels of curcuminoid uptake and loss were observed within a few hours and leveled off within eight hours post treatment onset. The addition or removal of curcuminoids from media resulted in corresponding changes in SOD activity, and the involvement of each of the three SOD genes was assessed for their contribution to total SOD activity. Taken together, these data provide insight into the uptake and clearance dynamics of curcuminoids and indicate that, while SOD activity generally increases following curcuminoid treatment, the individual SOD genes appear to contribute differently to this response.

Activation of the Cap'n'collar C pathway (Nrf2 pathway in vertebrates) signaling in insulin pathway compromised Drosophila melanogaster flies ameliorates the diabetic state upon pro-oxidant conditions

The insulin pathway is a crucial central system for metabolism and growth. The Nrf2 signaling pathway functions to counteract oxidative stress. Here we sought to study the consequences of an oxidative stress challenge to insulin compromised and control adult flies of different ages, varying the activation state of the Nrf2 pathway in flies, the Cap'n'collar C pathway. For this, we employed two different pro-oxidative conditions: 3 % hydrogen peroxide or 20 mM paraquat laced in the food. In both cases, wild type (control) flies die within a few days, yet there are significant differences between males and females, and also within flies of different ages (seven versus thirty days old flies). We repeated the same conditions with young (seven days old) flies that were heterozygous for a loss-of-function mutation in Keap1. There were no significant differences. We then tested two hypomorphic viable conditions of the insulin pathway (heteroallelic combination for the insulin receptor and the S6 Kinase), challenged in the same way: Whereas they also die in the pro-oxidant conditions, they fare significantly better when heterozygous for Keap1, in contrast to controls. We also monitored locomotion in all of these conditions, and, in general, found significant differences between flies without and with a mutant allele (heterozygous) for Keap1. Our results point to altered oxidative stress conditions in diabetic flies. These findings suggest that modest activation of the Cap'n'collar C pathway may be a treatment for diabetic symptoms.

A Reliable and Consistent Method to Quantify Percent Lethality and Life Span in Drosophila melanogaster

Drosophila melanogaster is a classic model organism to study gene function as well as toxicological effects. To study gene function, the expression of a particular gene of interest is disrupted by using the widely explorable Drosophila genetic toolkit, whereas to study toxicological effects the flies are exposed to a particular toxicant through diet. These experiments often require the quantification of lethality from embryonic to adult stages, as well as the assessment of the life span in order to check the role of the gene/toxicant of interest in Drosophila. Here, we propose an experimental protocol that enables a consistent and rigorous assessment of lethality and life span of cadmium chloride (CdCl₂)-exposed or genetically perturbed flies [downregulation and overexpression of the cytosolic Cu, Zn superoxide dismutase (SOD1) gene], consecutively. The protocol insists upon the requirement of one single experimental setup that is unique, distinctive, and cost-effective as it engages minimal laboratory equipment and resources. The described methods lead to the smooth observation of the embryos, their successive stagewise transition, and life span of the adult flies post eclosion. Additionally, these methods also facilitate the assessment of crawling and climbing behavioral parameters of the larvae and adults, respectively, and allow the calculation of lethal concentration (LC₅₀) for the mentioned toxicant as well as median survival of the flies, which can be a determining factor in proceeding with further stages of experiments. Graphical abstract.

Copper Chaperone for Superoxide Dismutase FoCCS1 in Frankliniella occidentalis May Be Associated with Feeding Adaptation after Host Shifting

Western flower thrips (Frankliniella occidentalis) pose a serious threat to the global vegetable and flower crop production. The regulatory mechanism for superoxide dismutase (SOD) in the feeding adaptation of F. occidentalis after host shifting remains unclear. In this study, the copper chaperone for SOD (CCS) and manganese SOD (MnSOD) genes in F. occidentalis were cloned, and their expression levels at different developmental stages was determined. The mRNA expression of FoCCS1 and FoMnSOD2 in F. occidentalis second-instar larvae and adult females of F₁, F₂, and F₃ generations was analyzed after shifting the thrips to kidney bean and broad bean plants, respectively. The F₂ and F₃ second-instar larvae and F₂ adult females showed significantly upregulated FoCCS1 mRNA expression after shifting to kidney bean plants. The F₁ second-instar larvae and F₂ adult females showed significantly upregulated FoCCS1 mRNA expression after shifting to broad bean plants. The RNA interference significantly downregulated the FoCCS1 mRNA expression levels and adult females showed significantly inhibited SOD activity after shifting to kidney bean and broad bean plants. F. occidentalis adult females subjected to RNA interference and released on kidney bean and broad bean leaves for rearing, respectively, significantly reduced the survival rate and fecundity. These findings suggest that FoCCS1 plays an active role in regulating the feeding adaptation ability of F. occidentalis after host shifting.

Genome-wide identification and characterization of superoxide dismutases in four oyster species reveals functional differentiation in response to biotic and abiotic stress

Background

Oysters inhabit in the intertidal zone and may be suffered from environmental stresses, which can increase the production of reactive oxygen species (ROS), resulting in mass mortality. Superoxide dismutases (SODs) protect oysters from ROS damage through different mechanisms compared with vertebrates. However, the molecular and functional differentiation in oyster SODs were rarely analyzed.

Result

In this study, a total of 13, 13, 10, and 8 candidate SODs were identified in the genome of Crassostrea gigas, Crassostrea virginica, Crassostrea hongkongensis, and Saccostrea glomerata respectively. The domain composition, gene structure, subcellular locations, conserved ligands, and cis-elements elucidated the SODs into five groups (Mn-SODs, Cu-only-SODs, Cu/Zn ion ligand Cu/Zn-SOD with enzyme activity, Zn-only-SODs, and no ligand metal ions Cu/Zn-SODs). For single domain Cu/Zn-SODs, only one cytosolic Cu/Zn-SOD (cg_XM_034479061.1) may conserve enzymatic activity while most extracellular Cu/Zn-SOD proteins appeared to lose SOD enzyme activity according to conserved ligand amino acid analysis and expression pattern under biotic and abiotic stress in C. gigas. Further, multi-domain-SODs were identified and some of them were expressed in response to biotic and abiotic stressors in C. gigas. Moreover, the expression patterns of these genes varied in response to different stressors, which may be due to the cis-elements in the gene promoter.

Conclusion

These findings revealed the most extracellular Cu/Zn-SOD proteins appeared to lose SOD enzyme activity in oysters. Further, our study revealed that only one cytosolic Cu/Zn-SOD (cg_XM_034479061.1) may conserve enzymatic activity of SOD. Moreover, the expression patterns of these genes varied in response to different stressors, which may be due to the cis-elements in the promoter. This study provides important insights into the mechanisms through which oysters adapt to harsh intertidal conditions, as well as potential biomarkers of stress response in related species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08610-9.

Old dogs, new tricks: New insights into the iron/manganese superoxide dismutase family

Superoxide dismutases (SODs) are ancient enzymes of widespread importance present in all domains of life. Many insights have been gained into these important enzymes over the 50 years since their initial description, but recent studies in the context of microbial pathogenesis have resulted in findings that challenge long established dogmas. The repertoire of SODs that bacterial pathogens encode is diverse both in number and in metal dependencies, including copper, copper and zinc, manganese, iron, and cambialistic enzymes. Other bacteria also possess nickel dependent SODs. Compartmentalization of SODs only partially explains their diversity. The need for pathogens to maintain SOD activity across distinct hostile environments encountered during infection, including those limited for essential metals, is also a driver of repertoire diversity. SOD research using pathogenic microbes has also revealed the apparent biochemical ease with which metal specificity can change within the most common family of SODs. Collectively, these studies are revealing the dynamic nature of SOD evolution, both that of individual SOD enzymes that can change their metal specificity to adapt to fluctuating cellular metal availability, and of a cell's repertoire of SOD isozymes that can be differentially expressed to adapt to fluctuating environmental metal availability in a niche.

Four alternative splicing transcripts of intracellular copper/zinc superoxide dismutase 1 in Oxya chinensis

In this study, we obtained four alternative splicing transcripts of intracellular copper/zinc superoxide dismutase 1 (icCuZnSOD1) in Oxya chinensis. OcicCuZnSOD1a has all common characteristics of CuZnSOD family and is a canonical CuZnSOD. OcicCuZnSOD1b is missing a Zn binding site. OcicCuZnSOD1c lacks Zn ion and is a Cu-only SOD. OcicCuZnSOD1d is missing a CuZnSOD conserved sequence and lacks the E-loop, a conserved disulfide bond, and an active site arginine. OcicCuZnSOD1a was the most heat-resistant and OcicCuZnSOD1c was the most unstable at high temperatures above 55 °C. They were stable at a wide pH range, especially in alkaline conditions. The four variants expressed at the throughout developmental stages and had various tissue expression patterns. OcicCuZnSOD1a and OcicCuZnSOD1d were significantly induced by 8.79 mM CuCl₂ and OcicCuZnSOD1b was significantly up-regulated by 14.67 mM CuCl₂. OcicCuZnSOD1a was significantly inhibited by 19.13 mM ZnSO₄ while OcicCuZnSOD1d were significantly induced by 22.61 mM ZnSO₄. Disc diffusion assay showed that the four isoforms of OcicCuZnSOD1 made the killing zones smaller surrounding the CdCl₂-soaked filter discs. However, the reduction ratios of OcicCuZnSOD1a were the highest. These results implied that the four transcripts played roles in defense against CdCl₂-induced oxidative stress while OcicCuZnSOD1a had stronger antioxidant capacity.

Characterization of Superoxide Dismutase from the Potato Cyst Nematode, Globodera pallida

Potato cyst nematodes (PCNs), such as Globodera pallida and Globodera rostochiensis, are some of the most agriculturally and economically important pests of potato. Upon nematode infection, a principal component of plant defense is the generation of the reactive oxygen species (ROSs). ROSs are highly toxic molecules that cause damage to pathogens and host alike. To infect the plant, nematodes protect themselves from ROSs by activating their own antioxidant processes and ROS scavenging enzymes. One of these enzymes is a superoxide dismutase (SOD; EC 1.15.1.1), which prevents cellular damage by catalyzing conversion of the superoxide radical (O₂^-·) to hydrogen peroxide (H₂O₂) and molecular oxygen (O₂). We have isolated a putatively secreted isoform of a Cu-Zn SOD (SOD-3) from G. pallida and localized the expression of this gene in the posterior region of the nematode. Furthermore, we studied the expression of the SOD-3 gene during early parasitic stages of infection (24 to 72 h) in the susceptible potato cultivar Desiree, the resistant potato cultivar Innovator, and an immune host, Solanum sisymbriifolium. The SOD-3 gene was significantly upregulated, regardless of the host type; however, the expression pattern differed between the susceptible and the resistant or immune hosts. This finding suggests that SOD-3 gene is responding to infection in plant roots differently depending on whether the nematode is experiencing a compatible or an incompatible interaction.

Genetic repression of the antioxidant enzymes reduces the lifespan in Drosophila melanogaster

Aging is a biological process associated with gradual loss of function caused by cellular and molecular damages ultimately leading to mortality. Free radicals are implicated in oxidative damage which affects the longevity of organisms. Natural cellular defenses involving antioxidant enzymes delay or prevent oxidative damage and, therefore, influence the aging process and longevity has been shown in many species including Drosophila. We and others have shown that oxidative resistance is an important mechanism in the aging process in Drosophila. Therefore, we hypothesized that repressing endogenous antioxidant defenses shortens longevity in Drosophila. To study the influence of natural defense mechanisms against oxidative stress in aging, we have investigated the effect of genetic repression of the antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), on longevity in Drosophila using transgenic RNAi flies and in vivo inhibition of the enzymes with chemical inhibitors. RNAi lines of Drosophila viz., UAS-sod1-IR and UAS-cat-IR, are driven ubiquitously using Act5C-Gal4 and Tubulin-Gal4 to achieve the suppression of SOD1 and CAT activities, respectively. We show that genetic repression of SOD1 and CAT by RNAi in transgenic flies led to drastically reduced longevity (SOD1, 77%; CAT, 83%), presenting the evidence for the role of endogenous antioxidant defenses in lifespan extension in Drosophila. Further, our study shows that the enzyme inhibitors, diethyldithiocarbamate and 3-amino-1,2,4-triazole, although lower the enzyme activities in vivo in flies, but did not affect longevity, which could be attributed to the factors such as bioavailability and metabolism of the inhibitors and adaptive mechanisms involving de novo synthesis of the enzymes. Our study of genetic repression using transgenic RNAi provides experimental evidence that extended longevity is associated with endogenous antioxidant defenses and aging is correlated with oxidative stress resistance.

Duox-generated reactive oxygen species activate ATR/Chk1 to induce G2 arrest in Drosophila tracheoblasts

Progenitors of the thoracic tracheal system of adult Drosophila (tracheoblasts) arrest in G2 during larval life and rekindle a mitotic program subsequently. G2 arrest is dependent on ataxia telangiectasia mutated and rad3-related kinase (ATR)-dependent phosphorylation of checkpoint kinase 1 (Chk1) that is actuated in the absence of detectable DNA damage. We are interested in the mechanisms that activate ATR/Chk1 (Kizhedathu et al., 2018; Kizhedathu et al., 2020). Here we report that levels of reactive oxygen species (ROS) are high in arrested tracheoblasts and decrease upon mitotic re-entry. High ROS is dependent on expression of Duox, an H₂O₂ generating dual oxidase. ROS quenching by overexpression of superoxide dismutase 1, or by knockdown of Duox, abolishes Chk1 phosphorylation and results in precocious proliferation. Tracheae deficient in Duox, or deficient in both Duox and regulators of DNA damage-dependent ATR/Chk1 activation (ATRIP/TOPBP1/claspin), can induce phosphorylation of Chk1 in response to micromolar concentrations of H₂O₂ in minutes. The findings presented reveal that H₂O₂ activates ATR/Chk1 in tracheoblasts by a non-canonical, potentially direct, mechanism.

Reactive Oxygen Species in intestinal stem cell metabolism, fate and function

Long dismissed as merely harmful respiratory by-products, Reactive Oxygen Species (ROS) have emerged as critical intracellular messengers during cell growth and differentiation. ROS's signaling roles are particularly prominent within the intestine, whose high regenerative capacity is maintained by Intestinal Stem Cells (ISCs). In this review, we outline roles for ROS in ISCs as revealed by studies using Drosophila and mouse model systems. We focus particularly on recent studies highlighting how ROS ties to metabolic adaptations, which ensure energy supply matches demand during ISC activation and differentiation. We describe how declines in these adaptive mechanisms, through aging or pathology, promote reciprocal changes in ISC metabolism and ROS signaling. These changes ultimately contribute to aberrant ISC function, a loss of tissue homeostasis, and a shortened lifespan.

Characterizing the genetic basis of copper toxicity in Drosophila reveals a complex pattern of allelic, regulatory, and behavioral variation

A range of heavy metals are required for normal cell function and homeostasis. However, the anthropogenic release of metal compounds into soil and water sources presents a pervasive health threat. Copper is one of many heavy metals that negatively impacts diverse organisms at a global scale. Using a combination of quantitative trait locus (QTL) mapping and RNA sequencing in the Drosophila Synthetic Population Resource, we demonstrate that resistance to the toxic effects of ingested copper in D. melanogaster is genetically complex and influenced by allelic and expression variation at multiple loci. QTL mapping identified several QTL that account for a substantial fraction of heritability. Additionally, we find that copper resistance is impacted by variation in behavioral avoidance of copper and may be subject to life-stage specific regulation. Gene expression analysis further demonstrated that resistant and sensitive strains are characterized by unique expression patterns. Several of the candidate genes identified via QTL mapping and RNAseq have known copper-specific functions (e.g., Ccs, Sod3, CG11825), and others are involved in the regulation of other heavy metals (e.g., Catsup, whd). We validated several of these candidate genes with RNAi suggesting they contribute to variation in adult copper resistance. Our study illuminates the interconnected roles that allelic and expression variation, organism life stage, and behavior play in copper resistance, allowing a deeper understanding of the diverse mechanisms through which metal pollution can negatively impact organisms.

Molecular cloning, expression, and characterization of BmSOD3 in silkworm (Bombyx mori)

Superoxide dismutases (SODs) play an essential role in eliminating excess reactive oxygen species and maintaining the redox balance of the immune system. To study the function of BmSOD3 in silkworm, 543-bp full-length complementary DNA-encoding BmSOD3 was cloned from silkworm. The BmSOD3 amino acids were compared to their homologs, and several highly conserved regions were analyzed. We also carried out phylogenetic analyses of the SOD gene. Our results showed that the BmSOD3 gene belonged with the ecCu/Zn SOD gene. The BmSOD3 gene was transformed into the pET28a vector for functional expression in Escherichia coli. The sodium salt-polyacrylamide gel electrophoresis results showed that the molecular weight of recombinant BmSOD3 was about 22 kDa. The recombinant protein BmSOD3 was purified to detect its properties. After purification analyses, the enzyme activity showed Cu/Zn SOD activity, and the specific activity of the purified enzyme was 0.51 U/mg. The BmSOD3 transcripts showed tissue-specific expression in the midgut and malpighian tubule. The immune microarray data for BmSOD3 showed an expression signal that had a strong response to the induction of four pathogens (Bacillus bombyseptieus, Beauveria bassiana, E. coli, and nuclear polyhedrosis virus), particularly after infection for 24 h, which indicates that the BmSOD3 gene plays a key role in response to bacterial, fungal, and viral invasion. The fusion protein also showed antibacterial activity against E. coli in vitro. Thus, the fusion protein BmSOD3 exhibits antibacterial activity and may be used in production to combat diseases caused by bacteria in silkworm.

SOD1, more than just an antioxidant

During cellular respiration, radicals, such as superoxide, are produced, and in a large concentration, they may cause cell damage. To combat this threat, the cell employs the enzyme Cu/Zn Superoxide Dismutase (SOD1), which converts the radical superoxide into molecular oxygen and hydrogen peroxide, through redox reactions. Although this is its main function, recent studies have shown that the SOD1 has other functions that deviates from its original one including activation of nuclear gene transcription or as an RNA binding protein. This comprehensive review looks at the most important aspects of human SOD1 (hSOD1), including the structure, properties, and characteristics as well as transcriptional and post-translational modifications (PTM) that the enzyme can receive and their effects, and its many functions. We also discuss the strategies currently used to analyze it to better understand its participation in diseases linked to hSOD1 including Amyotrophic Lateral Sclerosis (ALS), cancer, and Parkinson.

Loss of Oxidation Resistance 1, OXR1, Is Associated with an Autosomal-Recessive Neurological Disease with Cerebellar Atrophy and Lysosomal Dysfunction

We report an early-onset autosomal-recessive neurological disease with cerebellar atrophy and lysosomal dysfunction. We identified bi-allelic loss-of-function (LoF) variants in Oxidative Resistance 1 (OXR1) in five individuals from three families; these individuals presented with a history of severe global developmental delay, current intellectual disability, language delay, cerebellar atrophy, and seizures. While OXR1 is known to play a role in oxidative stress resistance, its molecular functions are not well established. OXR1 contains three conserved domains: LysM, GRAM, and TLDc. The gene encodes at least six transcripts, including some that only consist of the C-terminal TLDc domain. We utilized Drosophila to assess the phenotypes associated with loss of mustard (mtd), the fly homolog of OXR1. Strong LoF mutants exhibit late pupal lethality or pupal eclosion defects. Interestingly, although mtd encodes 26 transcripts, severe LoF and null mutations can be rescued by a single short human OXR1 cDNA that only contains the TLDc domain. Similar rescue is observed with the TLDc domain of NCOA7, another human homolog of mtd. Loss of mtd in neurons leads to massive cell loss, early death, and an accumulation of aberrant lysosomal structures, similar to what we observe in fibroblasts of affected individuals. Our data indicate that mtd and OXR1 are required for proper lysosomal function; this is consistent with observations that NCOA7 is required for lysosomal acidification.

Characterization and Expression of Genes Encoding Superoxide Dismutase in the Oriental Armyworm, Mythimna separata (Lepidoptera: Noctuidae)

Superoxide dismutase (SOD) is an antioxidant metalloenzyme that catalyzes the dismutation of the superoxide anion O2- to O2 and H2O2. Many studies have focused on the role of SOD in response to abiotic stress, but its role during biotic stress, such as changes in organismal population density, has rarely been investigated. The oriental armyworm, Mythimna separata, is an economically important pest that exhibits phenotypic changes in response to population density. Solitary and gregarious phases occur at low and high population density, respectively. To examine the role of SODs in response to population density stress, we cloned two genes encoding SOD, MsCuZnSOD and MsMnSOD, and compared their expression in solitary and gregarious phases of M. separata. The MsCuZnSOD and MsMnSOD ORFs were 480 and 651 bp and encoded predicted protein products of 159 and 216 amino acids, respectively. The two SODs contained motifs that are typical of orthologous proteins. Real-time PCR indicated that the two SOD genes were expressed throughout developmental stages and were significantly upregulated in more mature stages of gregarious M. separata. Expression of the two SOD genes in various tissues of sixth-instar larvae was higher in gregarious versus solitary insects. Furthermore, expression of the SOD genes was significantly upregulated in response to crowding in solitary individuals, but suppressed in gregarious insects subjected to isolation. Collectively, these results suggest that population density may be key factor in the induction of SOD genes in M. separata.

Comparative analysis of seven types of superoxide dismutases for their ability to respond to oxidative stress in Bombyx mori

Insects are well adapted to changing environmental conditions. They have unique systems for eliminating reactive oxygen species (ROS). Superoxide dismutase (SOD) is a key enzyme that plays a primary role in removing ROS. Bombyx mori is a lepidopteran insect, whose body size is larger than the model insect Drosophila melanogaster, which enabled us to more easily examine gene expression at the tissue level. We searched B. mori SOD (BmSOD) genes using genome database, and we analyzed their function under different type of oxidative stress. Consequently, we identified four new types of BmSODs in addition to the three types already known. Two of the seven types had a unique domain architecture that has not been discovered previously in the SOD family, and they were expressed in different tissues and developmental stages. Furthermore, these BmSODs responded differently to several kinds of stressors. Our results showed that the seven types of BmSODs are likely to play different roles in B. mori; therefore, B. mori could be used to distinguish the functions of each SOD for resistance to oxidative stress that changes with the environmental conditions.

NADPH oxidase-generated reactive oxygen species in mature follicles are essential for Drosophila ovulation

Ovarian reactive oxygen species (ROS) are believed to regulate ovulation in mammals, but the details of ROS production in follicles and the role of ROS in ovulation in other species remain underexplored. In Drosophila ovulation, matrix metalloproteinase 2 (MMP2) is required for follicle rupture by degradation of posterior follicle cells surrounding a mature oocyte. We recently demonstrated that MMP2 activation and follicle rupture are regulated by the neuronal hormone octopamine (OA) and the octopamine receptor in mushroom body (OAMB). In the current study, we investigated the role of the superoxide-generating enzyme NADPH oxidase (NOX) in Drosophila ovulation. We report that Nox is highly enriched in mature follicle cells and that Nox knockdown in these cells leads to a reduction in superoxide and to defective ovulation. Similar to MMP2 activation, NOX enzymatic activity is also controlled by the OA/OAMB-Ca²⁺ signaling pathway. In addition, we report that extracellular superoxide dismutase 3 (SOD3) is required to convert superoxide to hydrogen peroxide, which acts as the key signaling molecule for follicle rupture, independent of MMP2 activation. Given that Nox homologs are expressed in mammalian follicles, the NOX-dependent hydrogen peroxide signaling pathway that we describe could play a conserved role in regulating ovulation in other species.

Superoxide dismutases: Dual roles in controlling ROS damage and regulating ROS signaling

Wang et al. review the dual role of superoxide dismutases in controlling reactive oxygen species (ROS) damage and regulating ROS signaling across model systems as well as their involvement in human diseases.

Superoxide dismutases (SODs) are universal enzymes of organisms that live in the presence of oxygen. They catalyze the conversion of superoxide into oxygen and hydrogen peroxide. Superoxide anions are the intended product of dedicated signaling enzymes as well as the byproduct of several metabolic processes including mitochondrial respiration. Through their activity, SOD enzymes control the levels of a variety of reactive oxygen species (ROS) and reactive nitrogen species, thus both limiting the potential toxicity of these molecules and controlling broad aspects of cellular life that are regulated by their signaling functions. All aerobic organisms have multiple SOD proteins targeted to different cellular and subcellular locations, reflecting the slow diffusion and multiple sources of their substrate superoxide. This compartmentalization also points to the need for fine local control of ROS signaling and to the possibility for ROS to signal between compartments. In this review, we discuss studies in model organisms and humans, which reveal the dual roles of SOD enzymes in controlling damage and regulating signaling.

Elevated expression of ageing and immunity genes in queens of the black garden ant

Studies in model organisms have identified a variety of genes whose expression can be experimentally modulated to produce changes in longevity, but whether these genes are the same as those involved in natural variation in lifespan remains unclear. Social insects boast some of the largest lifespan differences known between plastic phenotypes, with queen and worker lifespans differing by an order of magnitude despite no systematic nucleotide sequence differences between them. The contrasting lifespans of queens and workers are thus the result of differences in gene expression. We used RNA sequencing of brains and legs in 1-day-old and 2-month-old individuals of the ant Lasius niger to determine whether genes with queen-biased expression are enriched for genes linked to ageing in model organisms. Because the great longevity of queens may require investment into immune processes, we also investigated whether queen-biased genes are enriched for genes with known roles in immunity. Queen-biased genes in legs were enriched for ageing genes and for genes associated with increasing rather than decreasing lifespan. Queen-biased genes in legs were also enriched for immune genes, but only in 1-day-old individuals, perhaps linked to the changing roles of workers with age. Intriguingly, the single most differentially expressed gene between 1-day-old queen and worker brains was an extra-cellular form of CuZn Superoxide Dismutase (SOD3), raising the possibility of an important role of anti-oxidant genes in modulating lifespan.

A common theme in extracellular fluids of beetles: extracellular superoxide dismutases crucial for balancing ROS in response to microbial challenge

Extracellular Cu/Zn superoxide dismutases (SODs) are critical for balancing the level of reactive oxygen species in the extracellular matrix of eukaryotes. In the present study we have detected constitutive SOD activity in the haemolymph and defensive secretions of different leaf beetle species. Exemplarily, we have chosen the mustard leaf beetle, Phaedon cochleariae, as representative model organism to investigate the role of extracellular SODs in antimicrobial defence. Qualitative and quantitative proteome analyses resulted in the identification of two extracellular Cu/Zn SODs in the haemolymph and one in the defensive secretions of juvenile P. cochleariae. Furthermore, quantitative expression studies indicated fat body tissue and defensive glands as the main synthesis sites of these SODs. Silencing of the two SODs revealed one of them, PcSOD3.1, as the only relevant enzyme facilitating SOD activity in haemolymph and defensive secretions in vivo. Upon challenge with the entomopathogenic fungus, Metarhizium anisopliae, PcSOD3.1-deficient larvae exhibited a significantly higher mortality compared to other SOD-silenced groups. Hence, our results serve as a basis for further research on SOD regulated host-pathogen interactions. In defensive secretions PcSOD3.1-silencing affected neither deterrent production nor activity against fungal growth. Instead, we propose another antifungal mechanism based on MRJP/yellow proteins in the defensive exudates.