The paradigm that all oxygen-respiring eukaryotes have cytosolic CuZn-superoxide dismutase and that Mn-superoxide dismutase is localized to the mitochondria does not apply to a large group of marine arthropods

Functional characterization of a manganese superoxide dismutase from Avicennia marina: insights into its role in salt, hydrogen peroxide, and heavy metal tolerance

Avicennia marina is a salt-tolerance plant with high antioxidant and antibacterial potential. In the present work, a gene encoding MnSOD from Avicennia marina (AmSOD2) was cloned in the expression vectors pET28a. The resulting constructs were transformed into Escherichia coli strains Rosetta (DE3). Following the induction with Isopropyl β-D-1-thiogalactopyranoside, the protein His-AmSOD2 was expressed but dominantly found in the insoluble fraction of strain R-AmSOD2. Due to detection of mitochondrial transit peptide in the amino acid sequence of AmSOD2, the transit peptide was removed and AmSOD2 without transit peptide (tAmSOD2) was expressed in E. coli and dominantly found in the soluble fraction. The enzyme His-tAmSOD2 exhibited a molecular mass of 116 kDa in native condition. Nevertheless, in reducing conditions the molecular mass is 28 kDa indicating the enzyme His-tAmSOD2 is a tetramer protein. As shown by ICP analysis there is one mole Mn2+ in each monomer. The Pure His-tAmSOD2 was highly active in vitro, however the activity was almost three-fold lower than His-AmSOD1. Whereas the high stability of the recombinant His-AmSOD1was previously shown after incubation in a broad range pH and high temperature, His-tAmSOD2 was stable up to 50 °C and pH 6 for 1 h. The gene expression analysis showed that the gene encoding AmSOD2 is expressed in root, shoot and leaves of A. marina. In addition, the results show that the expression in the leaves was enhanced after treatment of plant with NaCl, H2O2, Cd2+ and Ni2+ indicating the important role of MnSOD in the resistant mechanism of mangroves.

The study of acidic/basic nature of metallothioneins and other metal-binding biomolecules in the soluble hepatic fraction of the northern pike (Esox lucius)

Since fish metalloproteins are still not thoroughly characterized, the aim of this study was to investigate the acidic/basic nature of biomolecules involved in the sequestration of twelve selected metals in the soluble hepatic fraction of an important aquatic bioindicator organism, namely the fish species northern pike (Esox lucius). For this purpose, the hyphenated system HPLC-ICP-MS was applied, with chromatographic separation based on anion/cation-exchange principle at physiological pH (7.4). The results indicated predominant acidic nature of metal-binding peptides/proteins in the studied hepatic fraction. More than 90 % of Ag, Cd, Co, Cu, Fe, Mo, and Pb were eluted with negatively charged biomolecules, and >70 % of Bi, Mn, and Zn. Thallium was revealed to bind equally to negatively and positively charged biomolecules, and Cs predominantly to positively charged ones. The majority of acidic (negatively charged) metalloproteins/peptides were coeluted within the elution time range of applied standard proteins, having pIs clustered around 4-6. Furthermore, binding of several metals (Ag, Cd, Cu, Zn) to two MT-isoforms was assumed, with Cd and Zn preferentially bound to MT1 and Ag to MT2, and Cu evenly distributed between the two. The results presented here are the first of their kind for the important bioindicator species, the northern pike, as well as one of the rare comprehensive studies on the acidic/basic nature of metal-binding biomolecules in fish, which can contribute significantly to a better understanding of the behaviour and fate of metals in the fish organism, specifically in liver as main metabolic and detoxification organ.

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.

A second intracellular copper/zinc superoxide dismutase and a manganese superoxide dismutase in Oxya chinensis: Molecular and biochemical characteristics and roles in chlorpyrifos stress

A second intracellular copper/zinc superoxide dismutase (icCuZnSOD2) and manganese SOD (MnSOD) were cloned and characterized in Oxya chinensis. The open reading frame (ORF) of OcicCuZnSOD2 and OcMnSOD are 462 and 672 bp encoding 153 and 223 amino acids, respectively. OcicCuZnSOD2 contains two signature sequences, one potential N-glycosylation site, and seven copper/zinc binding sites. OcMnSOD includes a mitochondria targeting sequence of 7 amino acids at N-terminal, one signature sequence, two N-glycosylation sites, and four manganese binding sites. The secondary structure and homology model of OcicCuZnSOD2 include nine β sheets, two Greek-key motifs, and one electrostatic loop. OcMnSOD contains nine α-helices and three β-sheets. Phylogenetic analysis shows that OcMnSOD is evolutionarily conserved while OcicCuZnSOD2 may be gene duplication and is paralogous to OcicCuZnSOD1. OcMnSOD expressed widely in all tissues and developmental stages. OcicCuZnSOD2 showed testis-specific expression and expressed highest in the 5th-instar nymph and the adult. The optimum temperatures and pH values of the recombinant OcicCuZnSOD2 and OcMnSOD were 40 °C and 8.0. They were stable at 25-55 °C and at pH 5.0-12.0 and pH 6.0-12.0, respectively. The activity and mRNA expression of each OcSOD were assayed after chlorpyrifos treatments. Total SOD and CuZnSOD activities first increased then declined under chlorpyrifos stress. Chlorpyrifos induced the mRNA expression and activity of OcMnSOD as a dose-dependent manner and inhibited OcicCuZnSOD2 transcription. The role of each OcSOD gene in chlorpyrifos stress was investigated using RNAi and disc diffusion assay with Escherichia coli overexpressing OcSOD proteins. Silencing of OcMnSOD significantly increased ROS content in chlorpyrifos-exposed grasshoppers. Disc diffusion assay showed that the plates with E. coli overexpressing OcMnSOD had the smaller inhibition zones around the chlorpyrifos-soaked filter discs. These results implied that OcMnSOD played a significant role in defense chlorpyrifos-induced oxidative stress.

Mitochondrial manganese superoxide dismutase from the shrimp Litopenaeus vannamei: Molecular characterization and effect of high temperature, hypoxia and reoxygenation on expression and enzyme activity

Climate warming has been increasing ocean water temperature and decreasing oxygen concentrations, exposing aquatic organisms to environmental stress conditions. The shrimp Litopenaeus vannamei manages to survive these harsh environmental conditions by enhancing their antioxidant defenses, among other strategies. In this study, we report the mitochondrial manganese superoxide dismutase (mMnSOD) nucleotide and deduced amino acid sequences and its gene expression in L. vannamei tissues. The deduced protein has 220 amino acids with a signal peptide of 20 amino acids. Expression of mMnSOD was analyzed in hepatopancreas, gills and muscle, where gills had highest expression in normoxic conditions. In addition, shrimp were subjected to high temperature, hypoxia and reoxygenation to analyze the effect on the expression of mMnSOD and SOD activity in mitochondria. High temperature and hypoxia showed a synergistic effect in the up-regulation on expression of mMnSOD in gills and hepatopancreas. Moreover, induction in SOD activity was found in the mitochondrial fraction from gills of normoxia at high temperature, probably due to an overproduction of reactive oxygen species caused by an elevated metabolic rate due to the stress temperature. These results suggest that the combined stress conditions of hypoxia and high temperature trigger molecularly the antioxidant response in L. vannamei in a higher degree than only one stressor.

Genome-Wide Identification and Characterization of SODs in Zhikong Scallop Reveals Gene Expansion and Regulation Divergence after Toxic Dinoflagellate Exposure

As filter-feeding animals mainly ingesting microalgae, bivalves could accumulate paralytic shellfish toxins (PSTs) produced by harmful algae through diet. To protect themselves from the toxic effects of PSTs, especially the concomitant oxidative damage, the production of superoxide dismutase (SOD), which is the only eukaryotic metalloenzyme capable of detoxifying superoxide, may assist with toxin tolerance in bivalves. To better understand this process, in the present study, we performed the first systematic analysis of SOD genes in bivalve Chlamys farreri, an important aquaculture species in China. A total of six Cu/Zn-SODs (SOD1-6) and two Mn-SODs (SOD7, SOD8) were identified in C. farreri, with gene expansion being revealed in Cu/Zn-SODs. In scallops exposed to two different PSTs-producing dinoflagellates, Alexandrium minutum and A. catenella, expression regulation of SOD genes was analyzed in the top ranked toxin-rich organs, the hepatopancreas and the kidney. In hepatopancreas, which mainly accumulates the incoming PSTs, all of the six Cu/Zn-SODs showed significant alterations after A. minutum exposure, with SOD1, 2, 3, 5, and 6 being up-regulated, and SOD4 being down-regulated, while no significant change was detected in Mn-SODs. After A. catenella exposure, up-regulation was observed in SOD2, 4, 6, and 8, and SOD7 was down-regulated. In the kidney, where PSTs transformation occurs, SOD4, 5, 6, and 8 were up-regulated, and SOD7 was down-regulated in response to A. minutum feeding. After A. catenella exposure, all the Cu/Zn-SODs except SOD1 were up-regulated, and SOD7 was down-regulated in kidney. Overall, in scallops after ingesting different toxic algae, SOD up-regulation mainly occurred in the expanded Cu/Zn-SOD group, and SOD6 was the only member being up-regulated in both toxic organs, which also showed the highest fold change among all the SODs, implying the importance of SOD6 in protecting scallops from the stress of PSTs. Our results suggest the diverse function of scallop SODs in response to the PST-producing algae challenge, and the expansion of Cu/Zn-SODs might be implicated in the adaptive evolution of scallops or bivalves with respect to antioxidant defense against the ingested toxic algae.

Effects of UV-B radiation on the survival, egg hatchability and transcript expression of antioxidant enzymes in a high-temperature adapted strain of Neoseiulus barkeri

Biological control of spider mites in hot and dry weather is a serious technical issue. A high-temperature adapted strain (HTAS) of the predatory mite Neoseiulus barkeri Hughes was selected from its conventional strain (CS), via long-term heat acclimation and frequent heat hardenings in our previous studies. However, the environment of high temperature is usually associated with enhanced ultraviolet (UV) radiation. In the present study, the physiological effects of UV-B radiation on survival rate and egg damage of N. barkeri were investigated, as well as the activities and expression profiles of antioxidant enzymes to UV-B radiation stress. UV-B radiation had deleterious effects on egg hatchability and survival of N. barkeri. Adults of the HTAS strain were less UV-B resistant than those of the CS strain; they also had lower levels of enzymatic activity of superoxide dismutase (SOD) and catalase against oxidative damage and weaker upregulation of SOD genes. The mRNA expression of three SOD genes of CS adult females immediately increased whereas that of HTAS showed almost no difference under UV-B stress for 1 h. The results showed the HTAS of N. barkeri had lower fitness under UV-B stress compared with the CS of N. barkeri. These results suggested that long-term heat acclimation may exert a profound impact on the developmental physiology of N. barkeri.

Ontogenetic changes in the expression of immune related genes in response to immunostimulants and resistance against white spot syndrome virus in Litopenaeus vannamei

In recent years, researchers have focused on viral and plant immunostimulants which could have beneficial effects in disease prevention and control in shrimp culture. At present, the application of the recombinant VP28 protein (r-VP28) and herbal immunostimulant has been considered as a more effective approach to prevent white spot syndrome (WSS) by enhancing the immune response in shrimp. In the present study, expression of selected immune related genes in response to r-VP28 and herbal immunostimulant mix (HIM) were separately studied qualitatively and quantitatively by RT-PCR and real time PCR, respectively during ontogenetic development from nauplius to juvenile stage in Litopenaeus vannamei. The mRNA expression level of immune related genes such as anti-lipopolysaccharides (ALF), Lysozyme, cMnSOD, Crustin, Prophenoloxidase, Tumor necrosis factor receptor-associated factor 6 (TRAF6) and Haemocyanin were found to be up-regulated significantly in different ontogenetic development stages of shrimp fed with r-VP28 and HIM formulated diets. Relative percent survival (RPS) was determined in shrimp fed with immunostimulants formulated diets after oral challenge with WSSV. The survival of WSSV challenged shrimp was found to be higher in immunostimulants treated groups when compared to untreated group. The results of PCR, ELISA and real time PCR revealed the absence of WSSV in WSSV-challenged shrimp after 20 days of treatment with immunostimulants. Among these immunostimulants, HIM was found to be more effective when compared to r-VP28. After a survey of literature, we are of the opinion that this might be the first report on the expression of immune genes during ontogenetic development of L. vannamei in response to immunostimulants.

Overexpression of Mn-superoxide dismutase in Oxya chinensis mediates increased malathion tolerance

Superoxide dismutase (SOD) is the first line of defense against oxidative damage. Malathion is an organophosphate insecticide and can induce the production of reactive oxygen species (ROS) and cause the intracellular oxidative stress. The present study was undertaken to examine the effects of malathion on SODs activity and their transcriptional levels in Oxya chinensis (Thunberg) (Orthoptera: Acrididae). The results showed that total SOD and MnSOD activities increased as a dose-dependent manner while CuZnSOD activity has no significant changes after malathion treatments. Total SOD and MnSOD activities were the highest at the concentration of 0.8 μg μL^-1 malathion treatment and increased significantly about 1.81- and 2.48-fold compared with the control, respectively. Increased mRNA expression of MnSOD, ecCuZnSOD1, and ecCuZnSOD2 were observed after malathion treatments. Moreover, the alteration of MnSOD transcript was similar to the profiles of MnSOD activity. These results suggested that the up-regulation expression of MnSOD transcript led to the increase of MnSOD activity in order to eliminate the excessive ROS caused by malathion. In addition, we evaluated the role of individual SOD gene in malathion stress by using RNAi and recombinant SOD proteins. The results showed that ROS contents increased significantly after the silencing of MnSOD and ecCuZnSOD1 genes. The OD values of the E. coli cells transformed with pET-28a-OcMnSOD plasmid were 1.13-1.31-fold and 1.08-1.33-fold higher than those of cells with pET-28a plasmids under 0.4 and 0.8 μg μL^-1 malathion treatments, respectively. These findings indicated that MnSOD exerted an important role in defense oxidative stress caused by malathion.

Elevated water temperature increases the levels of reo-like virus and selected innate immunity genes in hemocytes and hepatopancreas of adult female blue crab, Callinectes sapidus

Seasonal changes in water temperature directly affect the aquatic ecosystem. The blue crab, Callinectes sapidus, inhabiting the Chesapeake Bay has been adapted to seasonal changes of the environmental conditions. In this, the animals halt their physiological process of the growth and reproduction during colder months while they resume these processes as water temperatures increase. We aimed to understand the effect of the elevated temperatures on a disease progression of reo-like virus (CsRLV) and innate immunity of adult female C. sapidus. Following a rise in water temperature from 10 to 23 °C, CsRLV levels in infected crabs rose significantly in hemocytes and multiple organs. However, in hemocytes, the elevated temperature had no effect on the levels of three innate immune genes: Cas-ecCuZnSOD-2, CasPPO and CasLpR three carbohydrate metabolic genes: CasTPS, CasGlyP; and CasTreh and the total hemocyte counts (THC). Interestingly, the hemocytes of CsRLV infected animals exposed to 23 °C for 10 days had significantly elevated levels of Cas-ecCuZnSOD-2 and CasTPS, compared to those of the uninfected ones also exposed to the same condition and compared to hatchery-raised females kept at 23 °C. Despite the lack of changes in THC, the types of hemocytes from the animals with high CsRLV levels differed from those of uninfected ones and from hatchery animals kept at 23 °C: CsRLV-infected crabs had hemocytes of smaller size with less cytosolic complexity than uninfected crabs. It therefore appears that the change in temperature influences rapid replication of CsRLV in all internal tissues examined. This implies that CsRLV may have broad tissue tropism. Interestingly, the digestive tract (mid- and hindgut) contains significantly higher levels of CsRLV than hemocytes while hepatopancreas and ovary have lower levels than hemocytes. Innate immune responses differ by tissue: midgut and hepatopancreas with upregulated Cas-ecCuZnSOD-2 similar to that found in hemocytes. By contrast, hepatopancreas showed a down-regulated CasTPS, suggesting carbohydrate stress during infection.

Effects of copper and cadmium on development and superoxide dismutase levels in horseshoe crab (Limulus polyphemus) embryos

Pollution by metals may adversely affect organisms through the generation of reactive oxygen species (ROS). In this study, we examined the sublethal effects of two metals, copper and cadmium, on horseshoe crab (Limulus polyphemus) embryos. Exposure to copper or cadmium at concentrations of 0.01-10 mg/L for periods of 4, 8, 16 and 24 h had minimal effect on embryo survival except at 100 mg/L Cu. However, metal-exposed embryos took significantly longer to hatch into first instar ("trilobite") larvae than seawater controls. Levels of superoxide dismutase (SOD), believed to be important in the response to oxidative stress, were determined by Western blotting. Both the Cu/Zn and Mn cofactor forms of SOD tended to be somewhat elevated in metal-exposed embryos, but the increases were neither dose nor time-dependent. Likewise, SOD enzymatic activity showed no significant differences comparing embryos exposed to metals with seawater controls. We conclude that the protective role of SOD's against ROS produced in response to metal exposure appears to be limited in horseshoe crab embryos, at least under our experimental conditions.

Investigating the Conformational Structure and Potential Site Interactions of SOD Inhibitors on Ec-SOD in Marine Mud Crab Scylla serrata: A Molecular Modeling Approach

Superoxide dismutases (SODs) act as a first line of the enzymatic antioxidant defense system to control cellular superoxide anion toxicity. Previously, several inhibitors have been widely identified and catalogued for inhibition of SOD activity; however, still the information about the mechanism of interaction and points toward the inhibitor interactions in structures of SODs in general and in extracellular (Ec)-SOD in particular is still in naive. In the present research, we present an insight to elucidate the molecular basis of interactions of SOD inhibitors with Ec-SOD in mud crab Scylla serrata using molecular modeling and docking approaches. Different inhibitors of SOD such as hydrogen peroxide [Formula: see text], potassium cyanide, sodium dodecyl sulfate (SDS), [Formula: see text]-mercaptoethanol and dithiocarbamate were screened to understand the potential sites that may act as sites for cleavage or blocking in the protein. SOD-SDS and [Formula: see text] complex interactions indicate residues Pro72 and Asp102 of the predicted crab Ec-SOD as common targets. The GOLD result indicates that Pro72, Asp102 and Thr103 are commonly acting as the site of interaction in Ec-SOD of S. serrata with SOD inhibitors. For the first time, the results of this study provide an insight into the structural properties of Ec-SOD of S. serrata and define the possible involvements between the amino acids present in its active sites, i.e., in the regions from 70 to 84 and from 101 to 103 and different inhibitors.

Cloning of a putative extracellular Cu/Zn superoxide dismutase and functional differences of superoxide dismutases in invasive and indigenous whiteflies

Superoxide dismutases (SODs) are a group of important antioxidant defense enzymes. In this study, a putative extracellular Cu/Zn superoxide dismutase (ecCuZnSOD) complementary DNA was cloned and characterized from the whitefly, Bemisia tabaci. Quantitative polymerase chain reaction analysis showed that the expression level of BtecCuZnSOD was more than 10-fold higher in the invasive Middle East Asia Minor 1 (MEAM1) than in the native Asia II 3 species of the B. tabaci species complex. After exposure to low temperature (4 °C), the expression of Bt-ecCuZnSOD gene was significantly up-regulated in MEAM1 but not in Asia II 3. Furthermore, the expression level of B. tabaci intracellular CuZnSOD (Bt-icCuZnSOD), Bt-ecCuZnSOD and mitochondrial MnSOD (Bt-mMnSOD) was compared after transferring MEAM1 and Asia II 3 whiteflies from favorable (cotton) to unfavorable host plants (tobacco). On cotton, both CuZnSOD genes were expressed at a higher level in MEAM1 compared with Asia II 3. Interestingly, after transferring onto tobacco, the expression of Bt-ecCuZnSOD was significantly induced in Asia II 3 but not in MEAM1. On the other hand, while Bt-mMnSOD was expressed equally in both species on cotton, Bt-mMnSOD messenger RNA was up-regulated in MEAM1 on tobacco. Consistently, enzymatic activity assays of CuZnSOD and MnSOD demonstrated that CuZnSOD might play an important protective role against oxidative stress in Asia II 3, whereas MnSOD activation was critical for MEAM1 whiteflies during host adaptation. Taken together, our results suggest that the successful invasion of MEAM1 is correlated with its constitutive high activity of CuZnSOD and inducible expression of MnSOD under stress conditions.

A novel murrel Channa striatus mitochondrial manganese superoxide dismutase: gene silencing, SOD activity, superoxide anion production and expression

We have reported the molecular characterization including gene silencing, superoxide activity, superoxide anion production, gene expression and molecular characterization of a mitochondrial manganese superoxide dismutase (mMnSOD) from striped murrel Channa striatus (named as CsmMnSOD). The CsmMnSOD polypeptide contains 225 amino acids with a molecular weight of 25 kDa and a theoretical isoelectric point of 8.3. In the N-terminal region, CsmMnSOD carries a mitochondrial targeting sequence and a superoxide dismutases (SOD) Fe domain (28-109), and in C-terminal region, it carries another SOD Fe domain (114-220). The CsmMnSOD protein sequence shared significant similarity with its homolog of MnSOD from rock bream Oplegnathus fasciatus (96%). The phylogenetic analysis showed that the CsmMnSOD fell in the clade of fish mMnSOD group. The monomeric structure of CsmMnSOD possesses 9 α-helices (52.4%), 3 β-sheets (8.8%) and 38.8% random coils. The highest gene expression was noticed in liver, and its expression was inducted with fungal (Aphanomyces invadans) and bacterial (Aeromonas hydrophila) infections. The gene silencing results show that the fish that received dsRNA exhibited significant (P < 0.05) changes in expression when compared to their non-injected and fish physiological saline-injected controls. The SOD activity shows that the activity increases with the spread of infection and decreases once the molecule controls the pathogen. The capacity of superoxide anion production was determined by calculating the granular blood cell count during infection in murrel. It shows that the infection influenced the superoxide radical production which plays a major role in killing the pathogens. Overall, this study indicated the defense potentiality of CsmMnSOD; however, further research is necessary to explore its capability at protein level.

Identification of novel copper/zinc superoxide dismutase (Cu/ZnSOD) genes in kuruma shrimp Marsupenaeus japonicus

Superoxide dismutases (SODs) protect cells from superoxides, but in invertebrates, they also have role in the innate immune system. In this study, the genes for five isoforms of copper/zinc superoxide dismutase (MjCu/ZnSOD) gene were identified and sequenced in kuruma shrimp, Marsupenaeus japonicus. The coding parts of the genes ranged from 516 to 585 bp in length and encoded from 172 to 194 amino acids. Structure, phylogenetic and BLAST analyses indicated that MjCu/ZnSOD isoform_3 and _5 belonged to extracellular Cu/ZnSOD (ecSOD) group while the other three isoforms belong to the intracellular Cu/ZnSOD family. In healthy shrimp, the highest expressions of isoform 2, 3 and 4 were in the gills, whereas the expression of isoform 5 was highest in hemocytes. Challenging the shrimp with WSSV and Vibrio penaeicida up-regulated the mRNA expressions of isoforms 3 and 5, suggesting that these isoforms have roles in the innate immune system of kuruma shrimp.

Development of a non-denaturing 2D gel electrophoresis protocol for screening in vivo uranium-protein targets in Procambarus clarkii with laser ablation ICP MS followed by protein identification by HPLC-Orbitrap MS

Limited knowledge about in vivo non-covalent uranium (U)-protein complexes is largely due to the lack of appropriate analytical methodology. Here, a method for screening and identifying the molecular targets of U was developed. The approach was based on non-denaturing 1D and 2D gel electrophoresis (ND-PAGE and ND-2D-PAGE (using ND-IEF as first dimension previously described)) in conjunction with laser ablation inductively coupled plasma mass spectrometry (LA-ICP MS) for the detection of U-containing proteins. The proteins were then identified by µbore HPLC-Orbitrap MS/MS. The method was applied to the analysis of cytosol of hepatopancreas (HP) of a model U-bioaccumulating organism (Procambarus clarkii). The imaging of uranium in 2D gels revealed the presence of 11 U-containing protein spots. Six protein candidates (i.e. ferritin, glyceraldehyde-3-phosphate dehydrogenase, triosephosphate isomerase, cytosolic manganese superoxide dismutase (Mn-SOD), glutathione S transferase D1 and H3 histone family protein) were then identified by matching with the data base of crustacea Decapoda species (e.g. crayfish). Among them, ferritin was the most important one. This strategy is expected to provide an insight into U toxicology and metabolism.

Genomic structure, characterization and expression analysis of a manganese superoxide dismutase from pearl oyster Pinctada fucata

Manganese superoxide dismutase (MnSOD) is a major component of the cellular defense mechanisms against oxidative damage. We cloned and analyzed the expression pattern and genomic structure of the MnSOD gene of pearl oyster Pinctada fucata, hereafter designated as PoMnSOD. The full-length PoMnSOD cDNA was 1080 bp in length and consisted of a 5'-untranslated region (UTR) of 222 bp, a 3'-UTR of 318 bp with a polyadenylation signal (AATAAA) at 15 nucleotides upstream of the poly (A) tail, and an open reading frame (ORF) of 540 bp encoding a polypeptide of 180 amino acids with an estimated molecular mass of 20.4 kDa and a predicted pI of 6.72. Sequence analysis showed that PoMnSOD contained MnSOD family signatures F(44)NGGGHLNH(52), I(97)QGSGWGWLA(106) and D(138)VWEHAYY(145), four conserved residues for manganese metal binding (H(4), H(52), D(138) and H(142)), and two potential N-glycosylation sites (N(33) and N(51)). Homology analysis revealed that PoMnSOD shared 47.6-55.9% identity and 57.4-65.6% similarity to the other known PoMnSOD amino acid sequences. PoMnSOD genomic DNA was 5040 bp in length and contained three exons and two introns, which was a tripartite organization and coincided with the consensus GT-AG splicing rule. PoMnSOD promoter contained the various transcription factors associated with the immune modulation and stress responses. Quantitative RT-PCR analysis demonstrated that PoMnSOD was constitutively expressed in all detected tissues, and PoMnSOD mRNA expression was significantly up-regulated in intestine, mantle, gills, digestive gland and haemocytes after Vibrio alginolyticus injection. These results suggested that PoMoSOD was an acute-response protein involved in the innate immune responses of pearl oyster, and provided general information about the mechanisms of innate immune defense against bacterial infection in pearl oyster.

Genomic organization of the cytosolic manganese superoxide dismutase gene from the Pacific white shrimp, Litopenaeus vannamei, and its response to thermal stress

Cytosolic manganese superoxide dismutase (cMnSOD) is an important antioxidant enzyme which catalyzes the conversion of superoxides to oxygen and hydrogen peroxide in several organisms. In the Pacific white shrimp, Litopenaeus vannamei, three cMnSOD genes (LvcMnSOD1-3) have previously been characterized. Here, the genomic structure of LvcMnSOD2 and its mRNA expression in response to thermal stress was examined. Analysis of the nucleotide sequence demonstrated that LvcMnSOD2 is comprised of 2392 bp spanning from the ATG translation start site to the stop codon and contains six exons interrupted by five introns. The 5' region upstream of the LvcMnSOD2 gene contains several putative regulatory elements but lacks the accepted TATA sequence. The putative transcription factor binding elements that may be involved in LvcMnSOD2 mRNA expression level include activator protein-1 (AP-1), cAMP response element binding protein (CREB), upstream stimulatory factor (USF), CAAT-enhancer binding protein (C/EBP), nuclear factor-κB (NF-κB) and heat shock regulatory element (HSE). In addition, we compared the 5' upstream sequences of the LvcMnSOD2 gene between two shrimp strains that are resistant or susceptible to Taura syndrome virus (TSV), respectively, which revealed the absence of the USF and C/EBP elements at positions -2125 and -1986, respectively, in the TSV-susceptible shrimp line. Moreover, genomic variations between the two shrimp strains were detected in some of the putative C/EBP, USF, HSE and NF-κB transcription factor binding elements. That these genomic variations might be involved in the TSV resistance as well as in stress responses remains to be evaluated. The presence of 15 putative HSEs suggests that the expression of LvcMnSOD2 is regulated under thermal stress. Here, we found that in response to a 1 or 3 h thermal stress (35 °C), the mRNA expression levels of LvcMnSOD2 were significantly increased and then gradually decreased in the recovering phase at room temperature (25 °C) to control levels by 3 h after the heat shock. Thus, the antioxidant system may be induced to protect cells from the oxidative damage caused by thermal stress. The genomic organization of LvcMnSOD2 likely provides a clue to the mechanisms that might regulate the antioxidant defense pathway in shrimps and so potentially in marine invertebrates.

Field study of cyclic hypoxic effects on gene expression in grass shrimp hepatopancreas

Grass shrimp, Palaemonetes pugio, are widely used for ecological and toxicological research. They commonly experience cyclic hypoxia in their natural habitats. The response of grass shrimp to laboratory-controlled cyclic hypoxia has been studied in detail, but little is known about how field acclimatized grass shrimp regulate the gene expression and response to cyclic hypoxia. In this study we examined morphometric parameters, relative fecundity and gene expression of grass shrimp collected from two areas in Weeks Bay (Mobile, Alabama). One is a traditionally normoxic location (WBM), and the other is a traditionally cyclic hypoxic location (WC). In the week preceding grass shrimp collection dissolved oxygen (DO) at the field sites was measured continuously. DO was <2 (mg/L DO) and between 2 and 3 (mg/L DO) for 0 and 255min at WBM, and for 285 and 1035min at WC, respectively. Weight and length of WBM grass shrimp were significantly greater than weight and length of WC shrimp. WBM shrimp had more eggs than WC shrimp, but the difference was not significant. Shrimp from WC had a significant higher number of parasites than those from WBM. A cDNA microarray was utilized to investigate the changes in gene expression in grass shrimp hepatopancreas. Five genes, previously identified as hypoxia/cyclic hypoxia-responsive genes in laboratory exposure studies, were significantly up-regulated in WC shrimp relative to WBM. A total of 5 genes were significantly down-regulated in the field study. Only one of those genes, vitellogenin, has been previously found in chronic and cyclic hypoxic studies. Up and down-regulation of 7 selected genes was confirmed by qPCR. The overall pattern of gene expression in wild shrimp from cyclic DO sites in Weeks Bay showed only weak correlations with gene expression in shrimp from chronic and cyclic hypoxic laboratory studies. It appears therefore that transcriptome profiles of laboratory acclimated animals are of limited utility for understanding responses in field acclimatized animals that are exposed to a broader array of environmental variables.

In silico prediction of 3D structure of Mn superoxide dismutase of Scylla serrata and its binding properties with inhibitors

In the present study, we used computational methods to model crab and rat MnSOD using the crystal structure of MnSOD from Homo sapiens (PDB code: 1MSD) as template by comparative modeling approach. We performed molecular dynamics simulations to study dynamic behavior of the crab MnSOD. The modeled proteins were validated and subjected to molecular docking analyses. Molecular docking tool was used to elucidate a comparative binding mode of the crab and rat SOD with potent inhibitors of SOD such as hydrogen peroxide (H2O2), potassium cyanide (KCN) and sodium dodecyl sulphate (SDS). The predicted valid structure of crab MnSOD did not show any interaction with KCN but close interaction with H2O2 and SDS. A possible inhibitory mechanism of SDS and H2O2 due to their interaction with the amino acids present in the active site of the MnSOD of the above two animals are elucidated. This allowed us to predict the binding modes of the proteins to elucidate probable mode of action and sites of interference.

Cloning, expression and characterization of mitochondrial manganese superoxide dismutase from the Whitefly, Bemisia tabaci

A mitochondrial manganese superoxide dismutase from an invasive species of the whitefly Bemisia tabaci complex (Bt-mMnSOD) was cloned and analyzed. The full length cDNA of Bt-mMnSOD is 1210 bp with a 675 bp open reading frame, corresponding to 224 amino acids, which include 25 residues of the mitochondrial targeting sequence. Compared with various vertebrate and invertebrate animals, the MnSOD signature (DVWEHAYY) and four conserved amino acids for manganese binding (H54, H102, D186 and H190) were observed in Bt-mMnSOD. Recombinant Bt-mMnSOD was overexpressed in Escherichia coli, and the enzymatic activity of purified mMnSOD was assayed under various temperatures. Quantitative real-time PCR analysis with whiteflies of different development stages showed that the mRNA levels of Bt-mMnSOD were significantly higher in the 4th instar than in other stages. In addition, the in vivo activities of MnSOD in the whitefly were measured under various conditions, including exposure to low (4 °C) and high (40 °C) temperatures, transfer from a favorable to an unfavorable host plant (from cotton to tobacco) and treatment with pesticides. Our results indicate that the whitefly MnSOD plays an important role in cellular stress responses and anti-oxidative processes and that it might contribute to the successful worldwide distribution of the invasive whitefly.

Cytosolic manganese superoxide dismutase genes from the white shrimp Litopenaeus vannamei are differentially expressed in response to lipopolysaccharides, white spot virus and during ontogeny

Manganese superoxide dismutase (MnSOD) is an antioxidant enzyme usually located in mitochondria. There are only a few examples of cytosolic MnSOD (cMnSOD). In the shrimp Litopenaeus vannamei, we have previously characterized three cMnSOD cDNAs and their differential tissue-specific expression. To obtain insights about their genomic organization, we characterized the three corresponding cMnSOD genes, named them cMnsod1, cMnsod2, and cMnsod3 and studied their specific expression during ontogeny, response to lipopolysaccharides (LPS) and white spot virus infection (WSSV) in hemocytes from shrimp. The first two genes contain five introns flanked by canonical 5'-GT-AG-3' intron splice-site junctions, while the third one is intron-less. We analyzed 995 nucleotides upstream cMnsod2, but no classical promoter sequences were found. The deduced products of the three cMnSOD genes differ in two amino acids and there are four silent changes. cMnsod3 expression is modulated by WSSV and cMnsod2 by LPS. cMnsod2 is expressed from eggs to post larval stage during ontogeny. This is the first report of crustacean cMnSOD multigenes that are differently induced during the defense response and ontogeny.

A novel putative lipoprotein receptor (CasLpR) in the hemocytes of the blue crab, Callinectes sapidus: cloning and up-regulated expression after the injection of LPS and LTA

The full-length cDNA encoding a putative lipoprotein receptor (CasLpR) was isolated from the hemocytes of Callinectes sapidus using 5' and 3' RACEs. The open reading frame for CasLpR contains a precursor of putative CasLpR consisting of 1710 amino acid residues including 22 amino acid residues of the signal peptide (22 amino acids). Mature CasLpR (1688 amino acids with 5.6% of phosphorylation sites) has multiple, putative functional domains: five low-density lipoprotein receptor domains in the N-terminus, and a G-protein-coupled receptor proteolysis site domain and a 7 transmembrane receptor (secretin family) domain in the C-terminus. To date, there are no proteins with a similar domain structure in the GenBank. The expression pattern of CasLpR was exclusive in hemocytes among all tested tissues obtained from a juvenile female at intermolt stage: brain, eyestalk ganglia, pericardial organs, and thoracic ganglia complex (nervous system); hepatopancreas (digestive system); heart, artery and hemocytes (circulatory system); gill and antennal gland (excretory system), hypodermis; and Y-organ (endocrine organ). There was no CasLpR expression in the ovary of an adult female. A putative function of CasLpR was examined after challenges of lipopolysaccharides (LPS) and lipoteichoic acid (LTA) in vivo using qRT-PCR assays. Animals at 24 h after injection of LPS or LTA up-regulated the expression of CasLpR in hemocytes by ∼3.5 and 1.4 folds, respectively, compared to the controls that received saline injection. LPS challenge also caused the greatest increment (∼55 folds) of heat shock protein 90 (Hsp90) expression in these samples. These data indicate that putative CasLpR and CasHsp90 may be involved in the defense system or the stress response of C. sapidus.

A second copper zinc superoxide dismutase (CuZnSOD) in the blue crab Callinectes sapidus: cloning and up-regulated expression in the hemocytes after immune challenge

The full-length cDNA (1362 nucleotides, GenBank JF736621) encoding an extracellular copper zinc superoxide dismutase initially isolated from an EST library of the blue crab Callinectes sapidus was characterized using 3' RACE and named Cas-ecCuZnSOD-2. The open reading frame of Cas-ecCuZnSOD-2 contains 203 deduced amino acids with the conserved active catalytic center for copper and zinc binding and the post-translational modification at two putative N-glycosylation and nine phosphorylation sites. Overall, the deduced amino acids of Cas-ecCuZnSOD-2 shared only 35% sequence identity with that of Cas-ecCuZnSOD (GenBank AF264031) which was previously found in C. sapidus, while it showed ∼75% sequence identity to Scylla paramamosain ecCuZnSOD (GenBank FJ774661). The expression profile of Cas-ecCuZnSOD-2 and the other three C. sapidus SODs: ecCuZn, cytMn- and mitMn SODs was largely ubiquitous among the tested tissues obtained from a juvenile female at intermolt: brain, eyestalk ganglia, pericardial organs, and thoracic ganglia complex (nervous system); hepatopancreas (digestive system); heart, artery and hemocytes (circulatory system); gill and antennal gland (excretory system), hypodermis, and Y-organ (endocrine organ). Our study reports, for the first time in the crustaceans, expression analyses for all four Cas-SODs in hemocytes after immune challenges. Crabs challenged with lipopolysaccharides (LPS) injection had a remarkable induction of Cas-ecCuZnSOD-2 expression along with three other SODs in hemocytes, suggesting that Cas-SODs including Cas-ecCuZnSOD-2 are involved in the defense system, possibly innate immunity and immunocompetency of C. sapidus.

A tandem duplication of manganese superoxide dismutase in Nosema bombycis and its evolutionary origins

Microsporidia are a group of obligate intracellular eukaryotic parasites with small genomes. They infect animals from a wide variety of phyla, including humans. Two manganese superoxide dismutase (MnSOD) genes, designated NbMnSOD1 and NbMnSOD2, were found to be organized in a tandem array within the Nosema bombycis genome. The genes, both 678 bp in length, were found to be more similar to each other than they are to homologous genes of other Microsporidia, suggesting that the tandem duplication occurred subsequent to the development of this lineage. Reverse transcript PCR shows that mRNA for both genes is present in the spores. Analysis of the primary structure, hydrophobic cluster analysis, target signal analysis, and phylogenetic analysis all indicate that NbMnSOD1 is dimeric and targeted to the cytosol. NbMnSOD2 seems to have changed more rapidly and is under less evolutionary constraint than NbMnSOD1 suggesting that NbMnSOD2 may function under different conditions or in different tissues of its host rather than simply resulting in an increase in expression. A phylogenetic analysis of MnSOD sequences from eukaryotes, Archaea, and bacteria shows the microsporidial MnSODs to be grouped with the bacteria suggesting a possible horizontal gene transfer.

Expression of immune-related genes in the digestive organ of shrimp, Penaeus monodon, after an oral infection by Vibrio harveyi

In all previous studies, to study shrimp immune response, bacteria were directly injected into the shrimp body and as a consequence the initial step of a natural interaction was omitted. In this study we have instead used an immersion technique, which is a more natural way of establishing an infection, to study immune responses in black tiger shrimp (Penaeus monodon). Normally, Vibrio harveyi (Vh) is highly pathogenic to post-larval shrimp, but not to juveniles which usually resist an infection. In post-larvae, Vh causes a massive destruction of the digestive system, especially in the hepatopancreas and in the anterior gut. We have therefore investigated changes in transcription levels of fifteen immune-related genes and morphological changes in juvenile shrimp following an immersion of shrimp in Vh suspension. We found that a pathogenic bacterium, Vh, has the capacity to induce a local expression of some immune-related genes in shrimp after such a bacterial immersion. Our results show that in the juvenile gut small changes in expression of the antimicrobial peptide (AMP) genes such as antilipopolysaccharide factor isoform 3, crustin and penaeidin were observed. However some other genes were more strongly induced in their expression compared to the AMP genes. C-type lectin, Tachylectin 5a1 and mucin-like peritrophic membrane were increased in their expression and the C-type lectin was affected most in its expression. Several other examined genes did not change their expression levels. By performing histology studies it was found that Vh infection induced a strong perturbation of the midgut epithelium in some regions. As a consequence, the epithelial cells and basement membrane of the infected site were completely damaged and necrotic and massive hemocyte infiltration occurred underneath the affected tissue to combat the infection.

Molecular cloning, characterization, and the response of manganese superoxide dismutase from the Antarctic bivalve Laternula elliptica to PCB exposure

Manganese superoxide dismutase (leMnSOD) cDNA was cloned from the Antarctic bivalve Laternula elliptica. The full-length cDNA of leMnSOD is 1238 bp in length and contains an open reading frame of 681 bp encoding 226 amino acid residues including a putative mitochondrial targeting peptide of 26 amino acids in the N-terminal region. The calculated molecular mass is 24.8 kDa with an estimated isoelectric point of 6.75. leMnSOD signatures from 185 to 192 (DVWEHAYY) and four conserved amino acids (H52, H11, D185, and H192) responsible for binding manganese were observed. Sequence comparison showed that leMnSOD had high levels of identity with MnSOD from Haliotis discus discus, Mizuhopecten yessoensis, and Crassostrea gigas (68%, 66%, and 59%, respectively). RT-PCR analysis revealed the presence of leMnSOD transcripts in all tissues examined. Quantitative real-time RT-PCR assay indicated that treatment with polychlorinated biphenyls (PCBs) significantly increased leMnSOD mRNA expression in an organ-, time-, and dose-dependent manner. The mRNA expression with exposure to PCBs at 0.1 and 10 ppb reached the highest level at 6 h and then recovered slightly from 6 to 48 h in the gill. In contrast, the expression of leMnSOD mRNA showed a different expression pattern related to PCB concentration in the digestive gland. The mRNA expression at 0.1 ppb PCBs increased up to 12 h and then decreased by 48 h, but increased immediately at 10 ppb PCBs. The leMnSOD was overproduced in Escherichia coli and purified. The recombinant leMnSOD showed maximum activity at pH 9.0, and it retained more than 50% of its original activity after incubation for 30 min at 40 degrees C.

Antioxidant defence enzyme activities in hepatopancreas, gills and muscle of Spiny cheek crayfish (Orconectes limosus) from the River Danube

The aim of our study was to determine the activity of antioxidant defence (AD) enzymes: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and the phase II biotransformation enzyme glutathione-S-transferase (GST) in the hepatopancreas, the gills and muscle of Spiny cheek crayfish (Orconectes limosus) from the River Danube and to compare tissue specificities of investigated enzymes. Our results indicated that both specific and total SOD activities in the hepatopancreas were lower compared to the gills and muscle. Total SOD activity in the gills was lower with respect to that in muscle. CAT and GSH-Px (both specific and total) activities were higher in the hepatopancreas compared to those in the gills and muscle. In the gills the specific and total GR activities were higher than in the hepatopancreas and muscle. The specific and total GST activities were higher in the hepatopancreas compared with the gills and muscle. Our study represents the first comprehensive report of AD enzymes in tissues of O. limosus caught in the River Danube. The noted tissue distributions of the investigated AD enzyme activities most likely reflected different metabolic activities and different responses to environmental conditions in the examined tissues.

Tissue expressions of nine genes important to immune defence of the Pacific white shrimp Litopenaeus vannamei

The tissue expressions of nine immune related genes in apparently healthy Pacific white shrimp Litopenaeus vannamei were analyzed by conventional RT-PCR, quantitative real time PCR (qPCR) and in situ hybridisation. The nine genes were beta-glucan binding protein-high density lipoprotein (BGBP-HDL), lipopolysaccharide-beta-glucan binding protein (LGBP), haemocyanin, prophenoloxidase (proPO), transglutaminase (TGase), crustins, penaeidins (PEN), cytosolic manganese superoxide dismutase (cMnSOD), and lysozyme. Transcripts of all nine genes were detected in all tissues with differential expression levels when examined by RT-PCR and qPCR. BGBP-HDL, LGBP and haemocyanin were mainly expressed in the hepatopancreas and their expressions levels were about 1/10-1/3 those of beta-actin. Their expressions in other tissues were relatively limited. ProPO, TGase, crustins, PEN-3, and lysozyme showed the highest levels of expression in haemocytes and the lowest in hepatopancreas. Their expression levels in the haemocytes were 3 (PEN-3) to 10(-2) (proPO) times those of beta-actin. In contrast to the other genes, cMnSOD showed higher expression levels in haemolymph related organ, stomach and muscle; and lower expression levels in haemocyte, migut, neural ganglion and hepatopancreas. When examined by in situ hybridisation, hepatopancreatic F cells were found to be the major cell type that produced transcripts of BGBP-HDL, LGBP and haemocyanin. On the other hand, circulatory haemocytes and haemocytes infiltrated in various tissues contributed to the expressions of proPO, TGase, crustins, PEN-3 and lysozyme. Both hepatopancreatic F cell and haemocyte generated cMnSOD transcripts. Using in situ hybridisation, the present study is the first to show the tissue distributions of BGBP-HDL, LGBP, haemocyanin, TGase, crustins and cMnSOD in healthy white shrimp. The present results provide a baseline data of physiological expressions for the genes that are important in immune activation and modulation in Pacific white shrimp and a guideline of tissue or organ sampling for effective gene expression analyses for future immunological studies.

The mitochondrial manganese superoxide dismutase gene in Chinese shrimp Fenneropenaeus chinensis: cloning, distribution and expression

Manganese superoxide dismutase (MnSOD) plays an important role in crustacean immune defense reaction by eliminating oxidative stress. Knowledge on MnSOD at molecular level allows us to understand its regulatory mechanism in crustacean immune system. A novel mitochondrial manganese superoxide dismutase (mMnSOD) was cloned from hepatopancreas of Chinese shrimp Fenneropenaeus chinensis by 3' and 5' rapid amplification of cDNA ends (RACE) PCR. The full-length cDNA consists of 1185bp with a 660bp open reading frame, encoding 220 amino acids. The deduced amino acid sequence contains a putative signal peptide of 20 amino acids. Sequence comparison showed that the mMnSOD of F. chinensis shares 88% and 82% identity with that of giant freshwater prawn Macrobrachium rosenbergii and blue crab Callinectes sapidus, respectively. mMnSOD transcripts were detected in hepatopancreas, hemocytes, lymphoid organ, intestine, ovary, muscle and gill by Northern blotting. RT-PCR analysis indicated that mMnSOD showed different expression profiles in shrimp hemocytes and hepatopancreas after artificial infection with white spot syndrome virus (WSSV). In addition, a fusion protein containing mMnSOD was produced in vitro. LC-ESI-MS analysis showed that two peptide fragments (-GDVNTVISLAPALK- and -NVRPDYVNAIWK-) of the recombinant protein were identical to the corresponding sequence of M. rosenbergii mMnSOD, and the enzyme activity of the refolded recombinant protein was also measured.

Tissue-specific expression and molecular modeling of cytosolic manganese superoxide dismutases from the white shrimp Litopenaeus vannamei

Manganese superoxide dismutases (MnSODs) are usually mitochondrial enzymes, although there are few examples of cytosolic MnSODs (cMnSOD). We have previously characterized a cMnSOD cDNA from Litopenaeus vannamei hemocytes, and to obtain new insights into the tissue specific expression and the protein structure, we characterized three more different cMnSOD transcripts (cMnsod1, cMnsod2 and cMnsod3) and modeled the three-dimensional protein structure using human MnSOD as a template. The nucleotide sequences differ in seven positions. Four differences are silent; while three produce changes in amino acid sequence. cMnsod1, cMnsod2 and cMnsod3 are differentially expressed in nervous system, hepatopancreas and hemocytes. The structural protein model predicts bona fide MnSODs with proper coordination for the enzymatic activity.

Cloning and characterisation of mitochondrial manganese superoxide dismutase (mtMnSOD) from the giant freshwater prawn Macrobrachium rosenbergii

A cDNA encoding a mitochondrial manganese superoxide dismutase (mtMnSOD) was cloned from the hepatopancreas of giant freshwater prawn Macrobrachium rosenbergii using reverse transcription polymerase chain reaction (RT-PCR) by degenerate primers. Both 3'- and 5'-regions were isolated by rapid amplification of cDNA end (RACE) PCR method. Analysis of nucleotide sequence revealed that the mtMnSOD full-length cDNA consists of 1202bp containing an open reading frame of 654bp, which encodes a protein consisting of 218 amino acids including a signal peptide of 16 amino acid residues. The calculated molecular mass of the mature proteins (202 amino acids) is 24kDa with an estimated pI of 7.12. Two putative N-glycosylation sites, NXT and NXS were observed in the mtMnSOD. Manganese superoxide dismutase signatures from 180 to 187 (DVWEHAYY), and four conserved amino acids responsible for binding manganese were observed (H48, H96, D180 and H184). Sequence comparison showed that the mtMnSOD deduced amino acid sequence of Macrobrachium rosenbergii has similarity of 88%, 78%, 56%, 54% and 46% to that of blue crab Callinectes sapidus, crucifix crab Charybdis feriatus, brown shrimp Farfantepenaeus aztecus, European lobster Palinurus vulgaris, and grass shrimp Palaemontes pugio, respectively, and has similarity of 45%, 44%, 43%, 26% and 25% to cytMnSOD (cytosolic MnSOD) deduced amino acid sequence of blue crab C. sapidus, prawn M. rosenbergii, tiger shrimp Penaeus monodon, grass shrimp P. pugio and brown shrimp F. aztecus, respectively. Quantitative real-time RT-PCR analysis showed that levels of mtMn-SOD transcripts in hepatopancreas and haemocytes were not significantly different between the M. rosenbergii injected with Lactococcus garvieae, and that injected with saline after 3h to 24h.

Molecular cloning and characterisation of copper/zinc superoxide dismutase (Cu,Zn-SOD) from the giant freshwater prawn Macrobrachium rosenbergii

A copper/zinc superoxide dismutase (Cu,Zn-SOD) cDNA was cloned from the hepatopancreas of giant freshwater prawn Macrobrachium rosenbergii using reverse transcription-polymerase chain reaction (RT-PCR) by degenerate primers. Both 3'- and 5'-regions were isolated by the rapid amplification of cDNA ends method. Analysis of nucleotide sequence revealed that the Cu,Zn-SOD cDNA clone consists of 845 bp with an open reading frame of 603 bp encoding a protein of 201 amino acids with a 22 amino acid signal peptide. The calculated molecular mass of the mature proteins (179 amino acids) is 21 kDa with an estimated pI of 4.75. Two putative N-glycosylation sites, NXT and NXS, were observed in the Cu,Zn-SOD. Four conserved amino acids responsible for binding copper (H86, H89, H106 and H163) and four conserved amino acids responsible for binding zinc (H106, H114, H123 and D126) were observed. Sequence comparison showed that the Cu,Zn-SOD deduced amino acid sequence of M. rosenbergii has similarity of 60% and 64% to that of freshwater crayfish Pacifastacus leniusculus ecCu,Zn-SOD and blue crab Callinectes sapidus ecCu,Zn-SOD, respectively. Quantitative real-time RT-PCR analysis showed that Cu,Zn-SOD transcripts in haemocytes of M. rosenbergii increased 3h and 6h after injection of Lactococcus garvieae, whereas Cu,Zn-SOD transcripts decreased in the hepatopancreas 3h after L. garvieae injection.

Oxidative balance and immunodetection of antioxidant enzymes in the hepatopancreas of the crabChasmagnathus granulatasubjected to anoxia and reoxygenation

The present study shows the activities and concentrations of the antioxidant enzymes superoxide dismutase (SOD) and glutathione S-transferase (GST) in the hepatopancreas of the crab Chasmagnathus granulata (Dana, 1851) (Decapoda, Brachyura) when exposed to periods of anoxia (8 h) and aerobic recovery (20 and 40 min post anoxia). Exposure to anoxia did not cause any change in the activities of the enzymes analyzed. The activities of these enzymes did not change with a decrease in environmental oxygen concentration. During reoxygenation, enzyme activities returned to control levels. The concentrations and activities of SOD and GST presented different response profiles. Exposure to anoxia caused increased lipoperoxidation (conjugated dienes and thiobarbituric acid reactive substances), whereas aerobic recovery reduced lipoperoxidation. The results of this study showed that C. granulata adjusts its antioxidant defense systems in an attempt to reduce and (or) avoid damage resulting from the reintroduction of oxygen.

Lipid rafts in Cryptococcus neoformans concentrate the virulence determinants phospholipase B1 and Cu/Zn superoxide dismutase

Lipid rafts have been identified in the membranes of mammalian cells, the yeast Saccharomyces cerevisiae, and the pathogenic fungus Candida albicans. Formed by a lateral association of sphingolipids and sterols, rafts concentrate proteins carrying a glycosylphosphatidylinositol (GPI) anchor. We report the isolation of membranes with the characteristics of rafts from the fungal pathogen Cryptococcus neoformans. These characteristics include insolubility in Triton X-100 (TX100) at 4 degrees C, more-buoyant density within a sucrose gradient than the remaining membranes, and threefold enrichment with sterols. The virulence determinant phospholipase B1 (PLB1), a GPI-anchored protein, was highly concentrated in raft membranes and could be displaced from them by treatment with the sterol-sequestering agent methyl-beta-cyclodextrin (MbetaCD). Phospholipase B enzyme activity was inhibited in the raft environment and increased 15-fold following disruption of rafts with TX100 at 37 degrees C. Treatment of viable cryptococcal cells in suspension with MbetaCD also released PLB1 protein and enzyme activity, consistent with localization of PLB1 in plasma membrane rafts prior to secretion. The antioxidant virulence factor Cu/Zn superoxide dismutase (SOD1) was concentrated six- to ninefold in raft membrane fractions compared with nonraft membranes, whereas the cell wall-associated virulence factor laccase was not detected in membranes. We hypothesize that raft membranes function to cluster certain virulence factors at the cell surface to allow efficient access to enzyme substrate and/or to provide rapid release to the external environment.

Molecular cloning and characterisation of cytosolic manganese superoxide dismutase (cytMn-SOD) from the giant freshwater prawn Macrobrachium rosenbergii

A cytosolic manganese superoxide dismutase (cytMn-SOD) cDNA was cloned from the hepatopancreas of giant freshwater prawn Macrobrachium rosenbergii using reverse transcription polymerase chain reaction (RT-PCR) by degenerate primers. Both 3'- and 5'-regions were isolated by rapid amplification of cDNA end RACE method. Analysis of nucleotide sequence revealed that the cytMn-SOD cDNA clone consists of 1339 bp with an open reading frame of 858 bp encoding a protein of 286 amino acids. The calculated molecular mass of the mature proteins (286 amino acids) is 31 kDa with an estimated pI of 5.52. Two putative N-glycosylation sites, NXT and NXS were observed in the cytMn-SOD. Four conserved amino acids responsible for binding manganese were observed (H110, H158, D243 and H247). Sequence comparison showed that the cytMn-SOD deduced amino acid sequence of M. rosenbergii has an overall similarity of 77% and 54% to that of blue crab Callinectes sapidus and tiger shrimp Penaeus monodon, respectively. Quantitative real-time RT-PCR analysis showed that cytMn-SOD transcript in hepatopancreas of M. rosenbergii decreased 3h after Lactococcus garvieae injection, but no significant change in cytMn-SOD transcript was observed in the haemocytes 3-24 h after L. garvieae injection.

Primary structure and properties of Mn-superoxide dismutase from scallop adductor muscle

Manganese-superoxide dismutase was purified to homogeneity from scallop adductor muscle using DEAE-Sephacel, Buthyl-Cellulofine and Superdex 200 pg column chromatographies. The molecular weights of the purified enzyme were calculated to be 22,321.4 according to time-of-flight mass spectrometry, and to be approximately 95,000 and 93,000 on Superdex 200 pg column chromatography and non-denatured PAGE, respectively, and were calculated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 24,000 and 25,000 in the absence and 25,000 in the presence of beta-mercaptoethanol. These findings suggested that the native enzyme is composed of four identical subunits. Other properties of scallop adductor muscle manganese-superoxide dismutase, including pH stability and heat stability, were also determined. We determined the partial amino acid sequences of purified manganese-superoxide dismutase using digestions by bromocyan and lysyl endopeptidase and also determined the manganese-superoxide dismutase cDNA structure. The amino acid sequence of the enzyme obtained using both methods showed homology to those of vertebrates such as human, bovine, chicken, Xenopus and zebrafish manganese-superoxide dismutases (64.91, 65.35, 64.47, 63.27 and 64.60%, respectively). We also predicted the 3D structure of scallop adductor muscle manganese-superoxide dismutase using molecular operating environment and compared its structure with those of other manganese-superoxide dismutases. The overall structure of scallop adductor muscle manganese-superoxide dismutase was very similar to those of other species, including human and Aspergillus.

OXIDATIVE STRESS IN MARINE ENVIRONMENTS: Biochemistry and Physiological Ecology

Oxidative stress-the production and accumulation of reduced oxygen intermediates such as superoxide radicals, singlet oxygen, hydrogen peroxide, and hydroxyl radicals-can damage lipids, proteins, and DNA. Many disease processes of clinical interest and the aging process involve oxidative stress in their underlying etiology. The production of reactive oxygen species is also prevalent in the world's oceans, and oxidative stress is an important component of the stress response in marine organisms exposed to a variety of insults as a result of changes in environmental conditions such as thermal stress, exposure to ultraviolet radiation, or exposure to pollution. As in the clinical setting, reactive oxygen species are also important signal transduction molecules and mediators of damage in cellular processes, such as apoptosis and cell necrosis, for marine organisms. This review brings together the voluminous literature on the biochemistry and physiology of oxidative stress from the clinical and plant physiology disciplines with the fast-increasing interest in oxidative stress in marine environments.

Characterisation of manganese superoxide dismutase from Phytophthora nicotianae

Three polypeptides with manganese superoxide dismutase (MnSOD) activity were found in mycelium, zoospores and germinated cysts of Phytophthora nicotianae. Their relative molecular weights in non-denaturing gels were approximately 34.5, 36 and 50 kDa. No evidence for the presence of either iron or copper/zinc SODs was detected at any of the developmental stages examined. The level of activity of the MnSOD polypeptides was similar in mycelia and spores. Degenerate PCR was used to amplify partial genes of two different MnSODs, designated PnMnSODI and PnMnSOD2, from P. nicotianae. Southern blot analysis indicated that there are two PnMnSOD1 genes in the P. nicotianae genome. Full length sequence was obtained for one of these genes, PnMnSOD1a, from a P. nicotianae bacterial artificial chromosome (BAC) library. RNA blots probed with PnMnSOD1 showed similar levels of expression in vegetative and sporulating hyphae, lower levels in germinated cysts and no detectable expression in zoospores. PnMnSOD1a had 96%, 97 % and 99 % amino acid identity with homologous genes from P. ramorum, P. infestans and P. sojae, respectively. The second gene cloned from P. nicotianae, PnMnSOD2, had only 38 % amino acid identity with PnMnSOD1a and was homologous to MnSODs that possessed an N-terminal mitochondrial targeting sequence in Phytophthora species and other eukaryotes. Southern blots indicated that there is one copy of PnMnSOD2 in the P. nicotianae genome. PnMnSOD2 was expressed at similar levels in mycelia and germinated cysts but PnMnSOD2 transcripts were not detectable in zoospores.

Effects of hypoxia on gene and protein expression in the blue crab, Callinectes sapidus

Increases in hypoxic conditions are one of the major factors responsible for declines in estuarine habitat quality, yet to date there are no indicators for recognizing populations of estuarine organisms that are suffering from chronic hypoxic stress. Here we test the hypothesis that alterations in gene and protein expression of antioxidant enzymes and other stress-specific proteins can be used as molecular indicators of hypoxic stress. Blue crabs, Callinectes sapidus, were exposed to 2-3 ppm DO for 5 days. Gene expression was measured using macroarrays constructed from cDNA of 10 partial gene transcripts cloned from blue crab hepatopancreas. Significant (p< or =0.05) down-regulation of gene expression was found for MnSOD, hemocyanin, ribosomal S15 and L23. Subtractive hybridization using RNA from control and hypoxic hepatopancreas tissues also indicated down-regulation of hemocyanin transcription. In contrast, Western blotting showed a significant (p< or =0.05) increase of hemocyanin protein in the hepatopancreas and cross-linking of MnSOD proteins in hypoxia-exposed crabs. Thus, hypoxia-responsive cDNA arrays and Westerns may be useful diagnostic tools for monitoring effects of hypoxia in estuarine crustacea.

Replacement of a cytosolic copper/zinc superoxide dismutase by a novel cytosolic manganese superoxide dismutase in crustaceans that use copper (haemocyanin) for oxygen transport

The blue crab, Callinectes sapidus, which uses the copper-dependent protein haemocyanin for oxygen transport, lacks the ubiquitous cytosolic copper-dependent enzyme copper/zinc superoxide dismutase (Cu,ZnSOD) as evidenced by undetectable levels of Cu,ZnSOD activity, protein and mRNA in the hepatopancreas (the site of haemocyanin synthesis) and gills. Instead, the crab has an unusual cytosolic manganese SOD (cytMnSOD), which is retained in the cytosol, because it lacks a mitochondrial transit peptide. A second familiar MnSOD is present in the mitochondria (mtMnSOD). This unique phenomenon occurs in all Crustacea that use haemocyanin for oxygen transport. Molecular phylogeny analysis suggests the MnSOD gene duplication is as old as the origin of the arthropod phylum. cytMnSOD activity in the hepatopancreas changes during the moulting cycle of the crab. Activity is high in intermoult crabs and non-detectable in postmoult papershell crabs. mtMnSOD is present in all stages of the moulting cycle. Despite the lack of cytCu,ZnSOD, crabs have an extracellular Cu,ZnSOD (ecCu,ZnSOD) that is produced by haemocytes, and is part of a large, approx. 160 kDa, covalently-linked protein complex. ecCu,ZnSOD is absent from the hepatopancreas of intermoult crabs, but appears in this tissue at premoult. However, no ecCu,ZnSOD mRNA can be detected, suggesting that the protein is recruited from the haemolymph. Screening of different taxa of the arthropod phylum for Cu,ZnSOD activity shows that those crustaceans that use haemoglobin for oxygen transport have retained cytCu,ZnSOD. It appears, therefore, that the replacement of cytCu,ZnSOD with cytMnSOD is part of an adaptive response to the dynamic, haemocyanin-linked, fluctuations in copper metabolism that occur during the moulting cycle of the crab.