Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0042961 (volvulus)
 4,305 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glutathione metabolism represents a potential target for anti-parasite drug design. The central role of glutathione reductase (GR) in maintenance of the thiol redox state and in anti-oxidative defence has to be evaluated in more detail in order to establish the essential function of this enzyme for the survival of the filarial parasite Onchocerca volvulus. The O. volvulus GR (OvGR) gene was cloned and sequenced. The gene is composed of 13 exons and 12 introns and spans 4065 bp. The first intron is located within the 5'-untranslated region of the gene, 16 nucleotides upstream of the translation initiation codon. Southern-blot analysis and structural characterization of the genomic sequence indicate that OvGR is encoded by a single-copy gene. Isolation of various cDNA clones revealed a polymorphism of polyadenylation initiation with no consensus polyadenylation sites in any of the cDNAs analysed. The entire cDNA is 1977 bp long and carries the nematode-specific spliced leader sequence SL1 at its 5' end, 236 nucleotides upstream of the first in-frame methionine. The cDNA codes for a polypeptide of 462 amino acids with 53.5% sequence identity with human GR (HsGR). A total of 18 out of 19 residues contributing to glutathione binding are identical in OvGR and HsGR. However, one of the arginine residues (Arg-224 in HsGR) involved in discrimination between NADPH and NADH in all known GRs is substituted by tryptophan (Trp-207 in OvGR). The coding region of OvGR was expressed in Escherichia coli as a histidine-fusion protein, and it was established that the parasite protein still favours the binding of NADPH (Km 10.9 microM) over NADH (Km 108 microM). The histidine-fusion protein has a subunit size of 54 kDa and is active as a homodimer of 110 kDa.
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PMID:Molecular characterization and expression of Onchocerca volvulus glutathione reductase. 927 Oct 84

The gene encoding the cytoplasmic copper/zinc superoxide dismutase (AVSOD1) from the filarial parasite Acanthocheilonema viteae was isolated from a genomic DNA library using a degenerate oligonucleotide probe. Additionally, cDNAs of the AVSOD1 and the secreted extracellular SOD (AVSOD2) were both cloned by RT-PCR, and the AVSOD2 was expressed at high levels in E. coli. The amino acid sequence of the AVSOD1 is 89.5 and 87.5% identical to that of the corresponding enzymes of Brugia pahangi and Onchocerca volvulus, respectively. In contrast, the AVSOD2 shows a lower degree of identity to the other filarial SODs and is extensively glycosylated. RT-PCR studies demonstrate the expression of both SOD subtypes in all developmental stages of A. viteae and indicate up-regulation of the AVSOD2 expression after transmission from the vector to the definitive host. This suggests an enhanced requirement for SOD activity in post-infective larval stages and adults of A. viteae. ELISAs performed with purified recombinant AVSOD2 show that the AVSOD2 is not a major target for the immune system in naturally infected jirds.
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PMID:Up-regulation of extracellular copper/zinc superoxide dismutase mRNA after transmission of the filarial parasite Acanthocheilonema viteae in the vertebrate host Meriones unguiculatus. 1057 30

Glutathione reductase (GR) plays an essential role in cell defense against reactive oxygen metabolites by sustaining the reduced status of an important antioxidant, glutathione. To address the effect of oxidative stresses on the intertidal copepod Tigriopus japonicus, we exposed specimens to hydrogen peroxide, heavy metals and different salinity levels, cloned and sequenced the oxidative stress-related GR gene. T. japonicus GR gene (Tigriopus GR) cDNA contained 1526 bp including an open reading frame (ORF) encoding 458 amino acids with a theoretical pI of 6.58 and a calculated molecular weight of 49.6 kDa. Tigriopus GR showed a high similarity to frog Xenopus laevis GR (identity 57%) and the filarial parasite, Onchocerca volvulus GR (identity 57%). Specific motifs such as flavin adenine dinucleotide-binding site (LVLGGGSGGIASARRAAEF), pyridine nucleotide-disulphide oxidoreductases class-I active site (GGTCVNVGCVP), and NADPH binding motif (GxGYIAx18Rx5R) were highly conserved in the deduced amino acid sequence of Tigriopus GR. Interestingly, its expression and enzyme characteristics were different from GR homologue of filarial parasite O. volvulus. To investigate the biochemical and enzymatic characteristics of Tigriopus GR protein, we constructed the expression vector, pCRT7/TOPO NT containing Tigriopus GR. Tigriopus pCRT7/TOPO NT/GR was expressed in Escherichia coli, and the soluble protein was purified by 6x His-tag chromatography. The recombinant Tigriopus GR enzyme was found to make homodimer complexes of approximately 108 kDa on 12% native gel electrophoresis and showed enzymatic activity with NADPH and oxidized glutathione (GSSG) as substrates. To analyze the gene expression of Tigriopus GR against different environmental stresses (hydrogen peroxide, salinity, and heavy metals), we performed real-time reverse transcriptase-polymerase chain reaction (real-time RT-PCR). Slight down-regulation in the expression of Tigriopus GR at the initial stage was observed upon exposure to hydrogen peroxide. The expression recovered in 2h, while there were significant changes upon heavy metal (Cu and Mn) exposures in a time-dependent manner. Also, Tigriopus GR expression was significantly increased with moderately high salt stress (24 and 40 ppt). In the case of low salt stress (0 and 12 ppt) the expression was found to be down-regulated. These findings provide a better understanding of cellular protection mechanisms in the intertidal copepod T. japonicus against the environmental stressors caused by non-optimal salt levels.
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PMID:Environmental stressors (salinity, heavy metals, H2O2) modulate expression of glutathione reductase (GR) gene from the intertidal copepod Tigriopus japonicus. 1707 28

Onchocerca volvulus is a human pathogenic filarial nematode causing chronic onchocerciasis, a disease characterized by chronic skin and eye lesions. Despite attempts to control this infection from many perspectives, it still remains a threat to public health because of adverse effects of available drugs and recent reports of drug resistance. Under control of an intact immune system, O. volvulus survives for a long time in the host by employing a variety of strategies including the utility of antioxidant enzymes. In the present study, we focus on the extracellular superoxide dismutase from O. volvulus (OvEC-SOD) found in the excretory/secretory products of adult worms. Contrary to previous studies, the OvEC-SOD was found to have a 19 amino acid long signal peptide that is cleaved off during the process of maturation. To validate this result, we designed a novel method based on Caenorhabditis elegans cup5(ar465) mutants to specifically evaluate signal peptide-mediated secretion of nematodal proteins. Following purification, the recombinant OvEC-SOD was active as a dimer. Site-directed mutagenesis of the three cysteines present in the OvEC-SOD shows that enzyme activity is markedly reduced in the Cys-192 mutant. A homology model of the OvEC-SOD underlines the importance of Cys-192 for the stabilization of the adjacent active site channel. The generation of a humoral immune response to secretory OvEC-SOD was indicated by demonstrating IgG reactivity in sera from patients infected with O. volvulus while the cross-reactivity of IgG in plasma samples from cows, infected with the most closely related parasite Onchocerca ochengi, occurred only marginally. High IgG1 and IgM titres were recorded in sera from mice infected with the filaria Litomosoides sigmodontis, however, low or no cellular proliferative responses were observed. Thus, the present data suggest that secretory OvEC-SOD is a target of the humoral immune response in human onchocerciasis and induced strongest IgG responses in hyperreactive onchocerciasis. Furthermore, humoral response during murine infection induced SOD-specific IgG that cross-reacted with OvEC-SOD.
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PMID:Functional characterization and immune recognition of the extracellular superoxide dismutase from the human pathogenic parasite Onchocerca volvulus (OvEC-SOD). 2267