Molecular cloning and characterization of a novel adenylate kinase 3 gene from Clonorchis sinensis

Recombinant adenylate kinase 3 from liver fluke Clonorchis sinensis for histochemical analysis and serodiagnosis of clonorchiasis

Due to the lack of an effective prophylactic intervention and diagnosis, human liver fluke Clonorchis sinensis continues to afflict a large human population, causing a chronic inflammatory bile duct disease. With an aim to identify target antigens for sensitive serodiagnosis, adenylate kinase 3 of C. sinensis (CsAK3) was successfully expressed in soluble form in Escherichia coli by fusion to an RNA-interacting domain derived from human Lys-tRNA synthetase and purified by Ni2+-affinity chromatography. Anti-CsAK3 serum was raised by immunization of mice, and Western blotting confirmed that CsAK3 was expressed in adult-stage C. sinensis. Histochemical analysis showed that CsAK3 was localized to the subtegumental tissue of C. sinensis and was excreted into the bile duct of the host. When tested against sera from various parasite-infected patients by enzyme-linked immunosorbent assay, the recombinant CsAK3 elicited a specific response to C. sinensis-infected sera. The results suggest that CsAK3, either alone or in combination with other antigens, could be used for improving the clinical diagnosis of clonorchiasis.

Toxicological effects of benzo(a)pyrene, DDT and their mixture on the green mussel Perna viridis revealed by proteomic and metabolomic approaches

Benzo(a)pyrene (BaP) and dichlorodiphenyltrichloroethane (DDT) are persistent organic pollutants and environmental estrogens (EEs) with known toxicity towards the green mussel, Perna viridis. In this study, the toxic effects of BaP (10 µg/L) and DDT (10 µg/L) and their mixture were assessed in green mussel gills with proteomic and metabolomic approaches. Metabolic responses indicated that BaP mainly caused disturbance in osmotic regulation by significantly decrease in branched chain amino acids, dimethylamine and dimethylglycine in gills of male green mussels after exposure for 7 days. DDT mainly caused disturbance in osmotic regulation and energy metabolism by differential alteration of betaine, dimethylamine, dimethylglycine, amino acids, and succinate in gills of male green mussels. However, the mixture of BaP and DDT didn't show obvious metabolite changes. Proteomic analysis showed different protein expression profiles between different treatment groups, which demonstrated that BaP, DDT and their mixture may have different modes of action. Proteomic responses revealed that BaP induced cell apoptosis, disturbance in protein digestion and energy metabolism in gills of green mussels, whereas DDT exposure altered proteins that were associated with oxidative stress, cytoskeleton and cell structure, protein digestion and energy metabolism. However, the mixture of BaP and DDT affected proteins related to the oxidative stress, cytoskeleton and cell structure, protein biosynthesis and modification, energy metabolism, growth and apoptosis.

Identification and biochemical characterization of adenylate kinase 1 from Clonorchis sinensis

Adenylate kinase 1 is responsible for the conversion of AMP into ADP involved in purine metabolism. In the present study, adenylate kinase 1 gene (CsADK1) was isolated from an adult cDNA library of Clonorchis sinensis, and the recombinant protein was expressed in Escherichia coli. Bioinformatics analysis implied that the putative protein contained 197 amino acids, and some residues in conservative binding sites of CsADK1 were substituted. The structure modeling analysis showed that CsADK1 was composed of a core domain, an NMP-binding domain, and a LID domain, which was just a small loop. It demonstrated that CsADK1 was a short isoform of ADKs. Moreover, CsADK1 was identified as an excretory/secretory product by western blot analysis. Real-time quantitative PCR showed that expression level of CsADK1 at the stage of excysted metacercaria was higher than those of adult worm (18.8-folds, P<0.01), metacercariae (1.5-folds, P<0.01), and eggs (5.6-folds, P<0.01). In addition, histochemistry analysis showed that CsADK1 was extensively distributed in metacercariae and in the vitellaria and eggs of adult worms. The Km and Vmax value for substrate ADP were 2.2 mM and 0.9 mM/min, respectively. The optimal temperature and pH value were 37 °C and from 7.5 to 8.0, respectively. The enzyme activity was highly dependent on Mg2+, and the optimal concentration of Mg2+ was 2 mM. However, the enzyme activity was slightly activated by Ca2+, and Mn2+ has no effect on activity. For monovalent ions, activity was highly activated by K+ and NH4+, but slightly by Li+. Taken together, CsADK1 was a metal ion-dependent enzyme involved in purine metabolism, which was important for development and reproduction, and might be a potential candidate for drug target for clonorchiasis.

Identification and characterization of myophilin-like protein: a life stage and tissue-specific antigen of Clonorchis sinensis

Clonorchiasis, caused by Clonorchis sinensis infection, has been an important public health problem in China. More messages about biology and pathogenicity of C. sinensis will be better for development of new strategies for clonorchiasis control. In the current study, using data from the published genomic and cDNA sequences for C. sinensis, we identify a gene encoding a myophilin-like protein (Cs myophilin-like). The cDNA sequence is 573 bp in length which encoded a protein of 190 amino acids. DNA sequence of Cs myophilin-like consists of four extrons and three introns. By mapping the draft genome of C. sinensis, single copy of myophilin-like gene is annotated. Bioinformatic analysis shows Cs myophilin-like comprises a calponin homology domain and three actin binding surfaces. It expresses at the life stage of adult worm and metacercaria but not in eggs. It intensively distributes in muscular locations such as oral sucker and pharynx of adult worm and sucker of metacercaria. The transcript level of Cs myophilin-like in oral sucker and pharynx is significantly higher than that in the rest of adult worm. Moreover, recombinant Cs myophilin-like is obtained and of antigenicity and immunoreactivity. It can be probed by sera from patients infected with trematode or cestode. Our data suggests that Cs myophilin-like may be involved in the host tissue invasion besides regulating the contraction of smooth muscle and movement of worm body. Taken together, the stable and soluble expression in Escherichia coli and immunogenicity of recombinant Cs myophilin-like proteins suggest that Cs myophilin-like may be a potential candidate for vaccine and drug target for clonorchiasis.

41.5-kDa Cathepsin L protease from Clonorchis sinensis: expression, characterization, and serological reactivity of one excretory-secretory antigen

Cysteine proteases (CPs) were associated with the pathogenicity and excystment of Clonorchis sinensis. Most of them were potential antigens for the immunodiagnosis of clonorchiasis. More researches on CPs will let us know more about their functions, and further employ them for the development of more efficient diagnostic reagent and prevention strategies. In the current study, a full-length sequence encoding cathepsin L from C. sinensis (CsCL41.5) was identified from our adult cDNA library. Bioinformatic analysis showed that CsCL41.5 included typical motifs of cathepsin L (ERFNIN and GNFD motifs) and conserved amino acid positions which constituted the active center of the enzyme. The identity of its amino acid sequence with the cathepsin L of Schistosoma japonicum was 49.6 %. Recombinant CsCL41.5 (rCsCL41.5) was highly expressed in the form of inclusion body in Escherichia coli, and soluble rCsCL41.5 was obtained after purification and renaturation. Western blotting analysis indicated that CsCL41.5 is an excretory-secretory antigen of C. sinensis adult. Immunolocalization demonstrated that CsCL41.5 is distributed in the intestine and eggs in the uterus of adult worm, tegument of metacercaria, oral suck, and tail of cercaria. ELISA assays showed that IgG4 was the predominant IgG isotype responding to rCsCL41.5 in sera from clonorchiasis patients. The sensitivity and specificity of specific IgG4 detection with rCsCL41.5 was 62.5 % (15/24) and 81.7 % (49/60), respectively. It was concluded that there were differences in biological function, efficiency of serodiagnosis, and characterization of immune reactivity between CsCL41.5 and other CPs of C. sinensis, combining with previous studies.

High-throughput screening identifies CHMP4A associated with hypoxia-inducible factor 1

AIMS

Tumor hypoxia is a common phenomenon and hypoxia-inducible factor-1 is the transcription factor that is most closely associated with hypoxia. Hypoxia-inducible factor-1 is overexpressed in most solid tumors and plays a vital role in hypoxic acclimatization, energy metabolism, tumor angiogenesis, tumor invasion, and drug tolerance in cancer cells. We aimed to identify novel human genes associated with the stability and transcriptional activity of hypoxia-inducible factor-1.

MAIN METHODS

A cell-based dual luciferase reporter system based on a hypoxia responsive element luciferase reporter gene was constructed to screen 409 novel human genes cloned in our lab. Western blot analysis was used to examine the changes in the expression level of hypoxia-inducible factor-1 α, and RT-PCR analysis was used to detect the transcription level of adenylate kinase 3.

KEY FINDINGS

Our results demonstrated that chromatin-modifying protein 4A could significantly up-regulate the hypoxia responsive element luciferase activity under both normoxic and cobalt chloride-induced hypoxic environment in HeLa cells. Moreover, Chromatin-modifying protein 4A could increase the expression of hypoxia-inducible factor-1 α protein under normoxic condition, and enhance the transcription level of adenylate kinase 3, which is one of the target genes of hypoxia-inducible factor-1.

SIGNIFICANCE

The functional screening platform therefore can be applied for the high-throughput screening of hypoxia-inducible factor-1-related genes, which would provide new insights into underlying molecular mechanisms that may regulate hypoxia in mammalian cells.

Dinucleotide polyphosphates contribute to purinergic signalling via inhibition of adenylate kinase activity

Dinucleoside polyphosphates are well described as direct vasoconstrictors and as mediators with strong proliferative properties, however, less is known about their effects on nucleotide-converting pathways. Therefore, the present study investigates the effects of Ap(4)A (diadenosine tetraphosphate), Up(4)A (uridine adenosine tetraphosphate) and Ap(5)A (diadenosine pentaphosphate) and the non-selective P2 antagonist suramin on human serum and endothelial nucleotide-converting enzymes. Human serum and HUVECs (human umbilical vein endothelial cells) were pretreated with various concentrations of dinucleotide polyphosphates and suramin. Adenylate kinase and NDP kinase activities were then quantified radiochemically by TLC analysis of the ATP-induced conversion of [(3)H]AMP and [(3)H]ADP into [(3)H]ADP/ATP and [(3)H]ATP respectively. Endothelial NTPDase (nucleoside triphosphate diphosphohydrolase) activity was additionally determined using [(3)H]ADP and [(3)H]ATP as preferred substrates. Dinucleoside polyphosphates and suramin have an inhibitory effect on the serum adenylate kinase [pIC(50) values (-log IC(50)): Ap(4)A, 4.67+/-0.03; Up(4)A, 3.70+/-0.10; Ap(5)A, 6.31+/-0.03; suramin, 3.74+/-0.07], as well as on endothelial adenylate kinase (pIC(50) values: Ap(4)A, 4.17+/-0.07; Up(4)A, 2.94+/-0.02; Ap(5)A, 5.97+/-0.04; suramin, 4.23+/-0.07), but no significant effects on serum NDP kinase, emphasizing the selectivity of these inhibitors. Furthermore, Ap(4)A, Up(4)A, Ap(5)A and suramin progressively inhibited the rates of [(3)H]ADP (pIC(50) values: Ap(4)A, 3.38+/-0.09; Up(4)A, 2.78+/-0.06; Ap(5)A, 4.42+/-0.11; suramin, 4.10+/-0.07) and [(3)H]ATP (pIC(50) values: Ap(4)A, 3.06+/-0.06; Ap(5)A, 3.05+/-0.12; suramin, 4.14+/-0.05) hydrolyses by cultured HUVECs. Up(4)A has no significant effect on the endothelial NTPDase activity. Although the half-lives for Ap(4)A, Up(4)A and Ap(5)A in serum are comparable with the incubation times of the assays used in the present study, secondary effects of the dinucleotide metabolites are not prominent for these inhibitory effects, since the concentration of metabolites formed are relatively insignificant compared with the 800 mumol/l ATP added as a phosphate donor in the adenylate kinase and NDP kinase assays. This comparative competitive study suggests that Ap(4)A and Ap(5)A contribute to the purinergic responses via inhibition of adenylate-kinase-mediated conversion of endogenous ADP, whereas Up(4)A most likely mediates its vasoregulatory effects via direct binding-mediated mechanisms.

A new type of metal-binding site in cobalt- and zinc-containing adenylate kinases isolated from sulfate-reducers Desulfovibrio gigas and Desulfovibrio desulfuricans ATCC 27774

Adenylate kinase (AK) mediates the reversible transfer of phosphate groups between the adenylate nucleotides and contributes to the maintenance of their constant cellular level, necessary for energy metabolism and nucleic acid synthesis. The AK were purified from crude extracts of two sulfate-reducing bacteria (SRB), Desulfovibrio (D.) gigas NCIB 9332 and Desulfovibrio desulfuricans ATCC 27774, and biochemically and spectroscopically characterised in the native and fully cobalt- or zinc-substituted forms. These are the first reported adenylate kinases that bind either zinc or cobalt and are related to the subgroup of metal-containing AK found, in most cases, in Gram-positive bacteria. The electronic absorption spectrum is consistent with tetrahedral coordinated cobalt, predominantly via sulfur ligands, and is supported by EPR. The involvement of three cysteines in cobalt or zinc coordination was confirmed by chemical methods. Extended X-ray absorption fine structure (EXAFS) indicate that cobalt or zinc are bound by three cysteine residues and one histidine in the metal-binding site of the "LID" domain. The sequence 129Cys-X5-His-X15-Cys-X2-Cys of the AK from D. gigas is involved in metal coordination and represents a new type of binding motif that differs from other known zinc-binding sites of AK. Cobalt and zinc play a structural role in stabilizing the LID domain.

A novel tegumental protein 31.8 kDa of Clonorchis sinensis: sequence analysis, expression, and immunolocalization

The complementary DNA (cDNA) plasmid libraries of adult worm, metacercariae and egg of Clonorchis sinensis (C. sinensis) were constructed for researches on genomics and proteomics of C. sinensis. The full-length cDNA sequence encoding tegumental protein 31.8 kDa (CsTP31.8) was identified from the adult cDNA library. The cDNA sequence has been submitted to the GeneBank Database with accession number ABK60086. This novel cDNA sequence contains 828 bp with a putative open reading frame of 275 amino acids. The deduced amino acid sequence shows identity to membrane-associate antigens or tegumental antigens of other species. There were conserved calcium-binding EF hand and dynein light chain type 1 in the sequence. CsTP31.8 transcripts were detected in cDNA libraries of adult worm and metacercariae but not in that of egg. Recombinant CsTP31.8 was expressed and purified from Escherichia coli BL21 (DE3). CsTP31.8 was immunolocalized at the tegument of adult C. sinensis by using antirecombinant CsTP31.8 sera.

Molecular cloning and identification of a novel Clonorchis sinensis gene encoding a tegumental protein

The tegumental membrane of platyhelminth parasites is of crucial importance for modulation of the host response and parasite survival. A cDNA encoding a novel tegumental protein 20.8 kDa (TP20.8) was found by large-scale sequencing of a Clonorchis sinensis cDNA library. This new cDNA was 755 bp long containing an open reading frame of 555 bp, which encoded a 20.8-kDa protein with an isoelectric point of 4.33. The deduced amino acid sequence exhibits 40 and 37% identity to Schistosoma japonicum sj20.8 and Schistosoma mansoni Sm 20.8, respectively. TP20.8 transcripts were detected in the adult worm and metacercariae cDNA libraries of C. sinensis but not in the egg. Recombinant C. sinensis TP20.8 protein was produced and purified from Escherichia coli BL21. Using specific anti-recombinant TP20.8 protein sera, the TP20.8 protein was immunohistochemically localized to the outer-surface membrane of C. sinensis. The specificity and sensitivity of the recombinant antigen for serologic diagnosis was assessed by enzyme-linked immunosorbent assay using serum from 100 patients with clonorchiasis, 20 patients with schistosomiasis, and 30 negative controls. The sensitivity was 68%, and the specificity was 84%. The antigen was less useful for the serodiagnosis of clonorchiasis with IgG.

Molecular characterization and serodiagnosis analysis of a novel lysophospholipase from Clonorchis sinensis

A cDNA clone encoding a novel lysophospholipase with a predicted molecular weight of 25.2 kDa was isolated from a Clonorchis sinensis adult cDNA library. The enzyme activity of the recombinant protein expressed in Escherichia coli was determined using phosphatidylcholine and lysophosphatidylcholine as substrates. Western blotting analysis indicated that it belonged to excretory/secretory proteins of the adults. The sensitivity and specificity of the recombinant antigen for serodiagnosis were evaluated with immunoglobulin enzyme-linked immunosorbent assay using serum samples from 20 patients with clonorchiasis and 20 patients with schistosomiasis. The sensitivity (75%) and specificity (80%) of the recombinant protein were comparable to those of crude extracts, at 65 and 82.5%, respectively. The sensitivity of the recombinant protein was 77% using 100 serum samples of clonorchiasis patients with various parasite burden. The results suggested that the recombinant lysophospholipase protein was not a satisfactory candidate for diagnosis of clonorchiasis, although it might be an excretory/secretory protein.

Clonorchis sinensis: molecular cloning and functional expression of a novel cytosolic glutathione transferase

Glutathione transferases (GSTs) represent a large family of enzymes. In the high throughput sequencing of the cDNA library constructed from the adult stage of Clonorchis sinensis (Cs), we isolate another cDNA clone encoding a novel cytosolic GST enzyme. To discriminate with our former reported CsGST, we designated this GST as CsGST1. This new cDNA contains 744 bp with a putative open reading frame of 213 amino acids. The deduced amino acid sequence exhibits 88% identity to Opisthorchis viverrini 28GST (Ov28GST), 60 and 52% identity to C. sinensis cytosolic 28-kDa GST (Cs28GST) and CsGST, respectively. The CsGST1 was expressed in Escherichia coli BL21(DE3) as a His-tag fusion protein and was purified by Ni-NTA agarose. The recombinant CsGST1 showed moderate GST activity of 0.79 U mg(-1). The average K (m) of the CsGST1 for 1-chloro-2, 4-dinitrobenzene is 150 microM. Cibacron blue F3GA and albendazole inhibited the CsGST1 activity with average IC(50) values of 9.1 and 265.4 muM, respectively. The nucleotide sequence reported in this paper was submitted to the GenBank Database with accession number DQ342327.

Molecular cloning and characterization of a novel lactate dehydrogenase gene from Clonorchis sinensis

From a Clonorchis sinensis adult worm cDNA library, we isolated a cDNA clone encoding a novel lactate dehydrogenase (LDH) gene which encoded a putative protein with a predicted molecular weight of 35.6 kDa. The optimum pH and temperature for the enzyme were 7.5 and 50 degrees C in the pyruvate reduction while 11 and 80 degrees C in the lactate oxidation reaction, respectively. CsLDH showed no substrate inhibition by high lactate and NAD(+) concentration, and the optimal pyruvate and optimal NADH concentrations were 10 and 0.5 mmol/l, respectively. The relative activities of these 2-oxocarboxylic acids were pyruvic acid>2-ketobutyrate>oxalacetic acid>alpha-ketoglutaric acid>phenylpyruvate. The cofactor 3-acetylpyridine adenine dinucleotide was much more effective than NAD(+). The cofactor analogs in which the nicotinamide ring is replaced by 3-pyridinealdehyde were lower activity cofactors, while the nicotinamide ring is replaced by nicotinic acid or thionicotinamide which is not a cofactor to CsLDH. The succinic acid and malic acid are not substrates of CsLDH. Cu(2+), Fe(2+), and Zn(2+) greatly inhibited the CsLDH activity both in the direction of pyruvate reduction and in the direction of lactate oxidation. The inhibition of CsLDH by gossypol may make gossypol a potential therapy drug or a lead compound for C. sinensis. Accordingly, the CsLDH may be a novel potential drug target.

Molecular cloning and characterization of cDNA encoding a novel cytosolic glutathione transferase from Clonorchis sinensis

Glutathione transferases (GSTs) are a group of multifunction isoenzymes coded by many genes. A cDNA encoding a novel cytosolic GST enzyme was cloned from a Clonorchis sinensis (Cs) adult worm cDNA library by large-scale sequencing. This new cDNA contains 786 bp with a putative open reading frame of 212 amino acids. The deduced amino acid sequence exhibits 61% identity to C. sinensis cytosolic 28-kDa GST. Recombinant CsGST was overexpressed in Escherichia coli BL21(DE3) and was purified by Ni-NTA Agarose. Enzymatic assays showed that the recombinant CsGST had a high activity of 22.7 U mg(-1). The average K (m) of the CsGST for 1-chloro-2,4-dinitrobenzene is 111 microM. Cibacron blue F3GA and albendazole inhibited the CsGST activity with respective average IC(50) of 1.1 and 247.1 microM. It provides a model for the structure and physiological function analysis on CsGST. The nucleotide sequence reported in this paper has been submitted to the GenBank Database with accession number DQ179264.