Role Of Glutathione S-transferases Research Articles

Role of glutathione transferase in phase separation of FUS and TAF15 in neurons

Role of glutathione transferase in phase separation of FUS and TAF15 in neurons

Role of glutathione S-transferases in the mode of action of herbicides that inhibit amino acid synthesis in Amaranthus palmeri

Acetolactate synthase inhibitors (ALS inhibitors) and glyphosate are two classes of herbicides that act by inhibiting an enzyme in the biosynthetic pathway of branched-chain or aromatic amino acids, respectively. Besides amino acid synthesis inhibition, both herbicides trigger similar physiological effects in plants. The main aim of this study was to evaluate the role of glutathione metabolism, with special emphasis on glutathione S-transferases (GSTs), in the mode of action of glyphosate and ALS inhibitors in Amaranthus palmeri. For that purpose, plants belonging to a glyphosate-sensitive (GLS) and a glyphosate-resistant (GLR) population were treated with different doses of glyphosate, and plants belonging to an ALS-inhibitor sensitive (AIS) and an ALS-inhibitor resistant (AIR) population were treated with different doses of the ALS inhibitor nicosulfuron. Glutathione-related contents, GST activity, and related gene expressions (glutamate-cysteine ligase, glutathione reductase, Phi GST and Tau GST) were analysed in leaves. According to the results of the analytical determinations, there were virtually no basal differences between GLS and GLR plants or between AIS and AIR plants. Glutathione synthesis and turnover did not follow a clear pattern in response to herbicides, but GST activity and gene expression (especially Phi GSTs) increased with both herbicides in treated sensitive plants, possibly related to the rocketing H2O2 accumulation. As GSTs offered the clearest results, these were further investigated with a multiple resistant (MR) population, compressing target-site resistance to both glyphosate and the ALS inhibitor pyrithiobac. As in single-resistant plants, measured parameters in the MR population were unaffected by herbicides, meaning that the increase in GST activity and expression occurs due to herbicide interactions with the target enzymes.

Biochemical alterations in cotton leafworm, Spodoptera littoralis (Boisd.) related to emamectin benzoate and fipronil compared to their joint action

Cotton leafworm, Spodoptera littoralis (Boisduval), is one of the major destructive pests of ornamental, industrial, and vegetable crops. The efficacy of technical emamectin benzoate (EMB) and fipronil (FPR) was assessed against the 4th larval instar using leaf-dip bioassay method. EMB was more efficient than FPR based on 96 h LC50 values of 0.004 and 0.023 μg/ml, respectively. Joint toxic action of the dual exposure in sequence with time interval 24 h and in mix were evaluated at LC10:LC10, LC25:LC25 and LC50:LC50 after 96 h posttreatment, as well. Their impacts on detoxification enzymes, esterases (ESTs); alkaline phosphatase (ALP); and glutathione S-transferase (GST) as well as acetylcholine esterase (AChE) were also determined. The sequential exposure of EMB after FPR (S1) produced antagonism, potentiation, and potentiation effects, respectively while sequential exposure of FPR after EMB (S2) interacted as addition, potentiation, and potentiation respectively. The rest of binary mixtures (Mix) revealed antagonistic effect regardless of concentration. Orthogonal contrast analysis showed that the highest elevations of AChE, α-EST, β- EST and ALP enzymes were obtained from Mix at LC50:LC50 (181.6%, 288.4, 229.2 and 460.9%, respectively), LC25:LC25 (131.5%, 252.8, 205.60 and 252.0, respectively) and LC10:LC10 (106.6%, 215.6%, 201.8% and 170.0%, respectively). Differently, the greatest elevation of GST activity (157.7%) resulted from S1 at LC50:LC50, while it was significantly lower at LC25:LC25 and LC10:LC10 as well as Mix and S2 at all concentrations than corresponding concentrations of FPR. These findings shed some light on the role of GST in FPR toxicity and clarified the risk of these dual exposures in elevating detoxification enzymes dangerously compared to their individual insecticides. These dual exposures should be carefully handled. Although rotational exposure at low concentrations may enhance performance and mitigate resistance risk, rotational exposure at high concentrations and Mix may indirectly contribute to the evolution of cross-resistance to other insecticides.

MRNA Sequencing Reveals Upregulation of Glutathione S-Transferase Genes during Acanthamoeba Encystation.

Some members of the genus Acanthamoeba are facultative pathogens typically with a biphasic lifestyle: trophozoites and cysts. Acanthamoeba is capable of infecting the cornea, resulting in Acanthamoeba keratitis. The cyst is one of the key components for the persistence of infection. Gene expression during Acanthamoeba encystation showed an upregulation of glutathione S-transferase (GST) genes and other closely related proteins. mRNA sequencing showed GST, and five genes with similar sequences were upregulated after 24 h of inducing encystation. GST overexpression was verified with qPCR using the HPRT and the cyst-specific protein 21 genes as controls. The GST inhibitor ethacrynic acid was found to decrease cell viability by 70%. These results indicate a role of GST in successful encystation, possibly by maintaining redox balance. GST and associated processes could be targets for potential treatments alongside regular therapies to reduce relapses of Acanthamoeba infection.

Susceptibility to acaricides and detoxifying enzyme activity in Tetranychus gloveri Banks (Acari: Tetranychidae) populations from India

ABSTRACT Tetranychus gloveri, a recently introduced mite species in Kerala, India has now established in the state as a predominant mite pest on ornamental plants. In this study, the status of acaricide resistance and the activity of detoxification enzymes were investigated in the populations of T. gloveri collected on Adenium plants from six different commercial horticultural nurseries of Thrissur district, Kerala, India. Adulticidal bioassays were performed for fenazaquin and dicofol, while nymphicidal bioassays were conducted for spiromesifen to estimate the LC50. The field populations showed resistance ratios in the range of 1.66–14.38-fold for fenazaquin, 1.06–27.31-fold for spiromesifen and 1.22–3.65-fold for dicofol, compared to the laboratory-maintained reference population. Enzyme assays of detoxifying enzymes revealed enhanced activity of carboxylesterase by 1.03–3.52-fold and cytochrome P450 monooxygenase by 1.01–2.08-fold in the field populations. However, the role of glutathione S-transferase in the development of resistance in different field populations was insignificant. The study recorded the development of resistance in the spider mite, T. gloveri to new generation acaricides spiromesifen and fenazaquin for the first time and also confirmed the significant role of the carboxylesterases and cytochrome P450 monooxygenases in imparting resistance in T. gloveri.

Overexpression of Maize Glutathione S-Transferase ZmGST26 Decreases Drought Resistance of Arabidopsis

Drought stress critically endangers the growth and development of crops. Glutathione S-transferase plays a vital role in response to abiotic stress. However, there are few studies on the role of glutathione S-transferase in maize drought stress. In this study, the significantly downregulated expression of ZmGST26 in roots under drought stress was analyzed by qRT-PCR. Promoter analyses showed that there were several cis-acting elements related to drought stress and that were involved in oxidative response in the promoter region of ZmGST26. Subcellular localization results showed that ZmGST26 was localized in the nucleus. The transgenic lines of the Arabidopsis over-expressing ZmGST26 were more sensitive to drought stress and ABA in seed germination and inhibited ABA-mediated stomatal closure. Under drought stress, phenotypic analyses showed that the germination rate, root length and survival rate of ZmGST26 overexpressing lines were significantly lower than those of wild-type lines. The determination of physiological and biochemical indexes showed that the water loss rate, malondialdehyde, O2− and H2O2 of the overexpression lines significantly increased compared with wild-type Arabidopsis, but the antioxidant enzyme activities (CAT, SOD and POD), and proline and chlorophyll contents were significantly reduced. Subsequently, the qRT-PCR analysis of drought stress-related gene expression showed that, under drought stress conditions, the expression levels of DREB2A, RD29A, RD29B and PP2CA genes in ZmGST26 overexpression lines were significantly lower than those in wild-type Arabidopsis. In summary, ZmGST26 reduced the drought resistance of plants by aggravating the accumulation of reactive oxygen species in Arabidopsis.

Glutathione-S-Transferases as Potential Targets for Modulation of Nitric Oxide-Mediated Vasodilation.

Glutathione-S-transferases (GSTs) are highly promiscuous in terms of their interactions with multiple proteins, leading to various functions. In addition to their classical detoxification roles with multi-drug resistance-related protein-1 (MRP1), more recent studies have indicated the role of GSTs in cellular nitric oxide (NO) metabolism. Vasodilation is classically induced by NO through its interaction with soluble guanylate cyclase. The ability of GSTs to biotransform organic nitrates such as nitroglycerin for NO generation can markedly modulate vasodilation, with this effect being prevented by specific GST inhibitors. Recently, other structurally distinct pro-drugs that generate NO via GST-mediated catalysis have been developed as anti-cancer agents and also indicate the potential of GSTs as suitable targets for pharmaceutical development. Further studies investigating GST biochemistry could enhance our understanding of NO metabolism and lead to the generation of novel and innovative vasodilators for clinical use.

Genome-Wide Identification of Glutathione S-Transferase and Expression Analysis in Response to Anthocyanin Transport in the Flesh of the New Teinturier Grape Germplasm 'Zhongshan-HongYu'.

Anthocyanins are synthesized in the endoplasmic reticulum and then transported to the vacuole in plants. Glutathione S-transferases (GSTs) are thought to play a key role in anthocyanin transport. To clarify the mechanism of GST genes in the accumulation and transport of anthocyanin in the early fruit stage, we analyzed and characterized the GST family in the flesh of ‘Zhongshan-HongYu’ (ZS-HY) based on the transcriptome. In this study, the 92 GST genes identified through a comprehensive bioinformatics analysis were unevenly present in all chromosomes of grapes, except chromosomes 3, 9 and 10. Through the analysis of the chromosomal location, gene structure, conserved domains, phylogenetic relationships and cis-acting elements of GST family genes, the phylogenetic tree divided the GST genes into 9 subfamilies. Eighteen GST genes were screened and identified from grape berries via a transcriptome sequencing analysis, of which 4 belonged to the phi subfamily and 14 to the tau subfamily, and the expression levels of these GST genes were not tissue-specific. The phylogenetic analysis indicated that VvGST4 was closely related to PhAN9 and AtTT19. This study provides a foundation for the analysis of the GST gene family and insight into the roles of GSTs in grape anthocyanin transport.

The Role of Glutathione S-Transferases in Pleomorphic Adenomas of the Salivary Glands

The aim of this study is to determine the expression levels of GST isoenzymes in salivary gland pleomorphic adenoma from 26 patients. In this study, we investigated the immunohistochemical staining characteristics of the Glutathione-S-transferase alpha (GSTA-1), sigma (GSTS-1), theta (GSTT-1), kappa (GSTK-1), mu (GSTM-1), omega (GSTO-1) isoenzymes in tumor and surrounding tumor-free (normal) salivary gland tissues from 26 patients. For immunohistochemical studies, tissues were obtained from 26 patients with salivary gland pleomorphic adenoma (PA). Tumor and control tissues of patients were compared according to their staining intensity. The correlations between GST expressions in PA tissue were analyzed by Spearman’s rho and the clinicopathological data were examined by Mann Whitney-U test and Spearman’s rho. Considering the differences in the expressions of GST isoenzymes between tumor tissues and normal tissues of the patients; No differences in GSTT1 and GSTS1 isoenzymes expression were found between tumor and normal tissues (p>0.05). GSTM1 and GSTO1 expression were significantly higher in tumor tissues than in normal tissue. However, GSTK1 and GSTA1 expressions were found to be significantly higher in the normal tissues of the patients compared to the tumor tissues. GSTM1 and GSTO1 expressions were increased in salivary gland PAs. These results should be confirmed with a larger series and different enzyme subtypes.

18S rRNA gene sequencing for environmental aflatoxigenic fungi and risk of hepatic carcinoma among exposed workers

Aspergillus exposure causes an increase in aflatoxin (AF) levels among exposed workers thereby increasing their risk of developing hepatocellular carcinoma (HCC). This study attempted to determine the presence of airborne aflatoxigenic fungi in environment of waste water treatment plant (WWTP); and study the hepatic cancer risks among exposed workers, emphasizing the role of glutathione S-transferases (GST) gene polymorphism protecting against the risk of hepatic cancer development due to exposure to AFs. The study isolated and identified different Aspergillus species producing AFs in air samples from WWTP sites using 18S ribosomal ribonucleic acid (18S rRNA) gene sequencing technique. GST gene polymorphisms were genotyped using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP). A significant increase in blood AF levels was found among WWTP exposed workers. The occurrence of GSTT1& M1 gene polymorphism in 6% of the workers was accompanied by significant decrease in the levels of AFs and alpha fetoprotein (AFP). In conclusion, Aspergillus-producing AFs were found in air of WWTP. Continuous exposure to AF-producing fungi caused elevated AF-levels in exposed workers. However only workers with heterozygous GSTT1& M1 genotypes can detoxify AFs, thereby decreasing the risk of HCC development among exposed workers.

The Role of Glutathione-S Transferase in Psoriasis and Associated Comorbidities and the Effect of Dimethyl Fumarate in This Pathway.

Psoriasis vulgaris is a chronic inflammatory skin disease characterized by well-demarcated scaly plaques. Oxidative stress plays a crucial role in the psoriasis pathogenesis and is associated with the disease severity. Dimethyl fumarate modulates the activity of the pro-inflammatory transcription factors. This is responsible for the downregulation of inflammatory cytokines and an overall shift from a pro-inflammatory to an anti-inflammatory/regulatory response. Both steps are necessary for the amelioration of psoriatic inflammation, although additional mechanisms have been proposed. Several studies reported a long-term effectiveness and safety of dimethyl fumarate monotherapy in patients with moderate-to-severe psoriasis. Furthermore, psoriasis is a chronic disease often associated to metabolic comorbidities, as obesity, diabetes, and cardiovascular diseases, in which glutathione-S transferase deregulation is present. Glutathione-S transferase is involved in the antioxidant system. An increase of its activity in psoriatic epidermis in comparison with the uninvolved and normal epidermal biopsies has been reported. Dimethyl fumarate depletes glutathione-S transferase by formation of covalently linked conjugates. This review investigates the anti-inflammatory role of dimethyl fumarate in oxidative stress and its effect by reducing oxidative stress. The glutathione-S transferase regulation is helpful in treating psoriasis, with an anti-inflammatory effect on the keratinocytes hyperproliferation, and in modulation of metabolic comorbidities.

Structural and Functional Characterization of One Unclassified Glutathione S-Transferase in Xenobiotic Adaptation of Leptinotarsa decemlineata.

Arthropod Glutathione S-transferases (GSTs) constitute a large family of multifunctional enzymes that are mainly associated with xenobiotic or stress adaptation. GST-mediated xenobiotic adaptation takes place through direct metabolism or sequestration of xenobiotics, and/or indirectly by providing protection against oxidative stress induced by xenobiotic exposure. To date, the roles of GSTs in xenobiotic adaptation in the Colorado potato beetle (CPB), a notorious agricultural pest of plants within Solanaceae, have not been well studied. Here, we functionally expressed and characterized an unclassified-class GST, LdGSTu1. The three-dimensional structure of the LdGSTu1 was solved with a resolution up to 1.8 Å by X-ray crystallography. The signature motif VSDGPPSL was identified in the “G-site”, and it contains the catalytically active residue Ser14. Recombinant LdGSTu1 was used to determine enzyme activity and kinetic parameters using 1-chloro-2, 4-dinitrobenzene (CDNB), GSH, p-nitrophenyl acetate (PNA) as substrates. The enzyme kinetic parameters and enzyme-substrate interaction studies demonstrated that LdGSTu1 could catalyze the conjugation of GSH to both CDNB and PNA, with a higher turnover number for CDNB than PNA. The LdGSTu1 enzyme inhibition assays demonstrated that the enzymatic conjugation of GSH to CDNB was inhibited by multiple pesticides, suggesting a potential function of LdGSTu1 in xenobiotic adaptation.

Regulation of GSTu1-mediated insecticide resistance in Plutella xylostella by miRNA and lncRNA.

The evolution of resistance to insecticides is well known to be closely associated with the overexpression of detoxifying enzymes. Although the role of glutathione S-transferase (GST) genes in insecticide resistance has been widely reported, the underlying regulatory mechanisms are poorly understood. Here, one GST gene (GSTu1) and its antisense transcript (lnc-GSTu1-AS) were identified and cloned, and both of them were upregulated in several chlorantraniliprole-resistant Plutella xylostella populations. GSTu1 was confirmed to be involved in chlorantraniliprole resistance by direct degradation of this insecticide. Furthermore, we demonstrated that lnc-GSTu1-AS interacted with GSTu1 by forming an RNA duplex, which masked the binding site of miR-8525-5p at the GSTu1-3′UTR. In summary, we revealed that lnc-GSTu1-AS maintained the mRNA stability of GSTu1 by preventing its degradation that could have been induced by miR-8525-5p and thus increased the resistance of P. xylostella to chlorantraniliprole. Our findings reveal a new noncoding RNA-mediated pathway that regulates the expression of detoxifying enzymes in insecticide-resistant insects and offer opportunities for the further understanding of the mechanisms of insecticide and drug resistance.

Glutathione S-Transferases in Marine Copepods

The glutathione S-transferase (GST) is a complex family of phase II detoxification enzymes, known for their ability to catalyze the conjugation of the reduced form of glutathione (GSH) to a wide variety of endogenous and exogenous electrophilic compounds for detoxification purposes. In marine environments, copepods are constantly exposed to multiple exogenous stressors, thus their capability of detoxification is key for survival. Full identification of the GST family in copepods has been limited only to few species. As for insects, the GST family includes a wide range of genes that, based on their cellular localization, can be divided in three classes: cytosolic, microsomal, and mitochondrial. The role of GSTs might have class-specific features, thus understanding the nature of the GST family has become crucial. This paper covers information of the GST activity in marine copepods based on studies investigating gene expression, protein content, and enzymatic activity. Using published literature and mining new publicly available transcriptomes, we characterized the multiplicity of the GST family in copepods from different orders and families, highlighting the possible role of these genes as biomarker for ocean health status monitoring.

Near-infrared frequency upconversion probe for revealing the relationship between glutathione S-transferase and drug-resistance

Drug resistance poses an enormous challenge for successful chemotherapy. Glutathione S-transferase (GST) has been confirmed to be involved in the progression of drug resistance to some anticancer drugs, thus revealing that the role of GST in anticancer drug resistance is necessary. Herein, by taking advantage of frequency upconversion luminescence (FUCL) technology, we reported an FUCL probe (NRh-NDs) that can detect GST based on a rhodamine derivative structure decorated with a 2,4-dinitrobenzenesulfonyl group (NDs). The NRh-NDs showed excellent sensitivity and high selectivity for GST and released the emissive dye NRh–NH2, which showed emission and excitation wavelengths in vitro of 820 nm and 850 nm, respectively. The NRh-NDs probe successfully tested endogenic GST in U87, MCF-7 and A549 cells. The cell data showed that the increased levels of GST were positively related to cisplatin resistance but not to 5-fluorouracil resistance. These results suggested that the probe could be used as a visual tool to reveal the cause of drug resistance for cisplatin resistance in cancer treatment. Furthermore, it may serve as an effective tool to confirm the mechanism of antitumor drug resistance.

Toxoplasma gondii glutathione S-transferase 2 plays an important role in partial secretory protein transport.

Toxoplasma gondii is an apicomplexan parasite, which has three unique secretory organelles: micronemes, rhoptries, and dense granules. Almost all the secreted proteins are transported through the endoplasmic reticulum (ER) and Golgi system to function in their respective destination by accurate targeting and packaging. Glutathione S-transferase (GST) is a supergene family enzyme that has multiple functions, which include regulation of cell proliferation and death signaling pathways, and participation in transportation and metabolism in mammal cells. However, the role of GST in Toxoplasma gondii has not been explained. In this study, we identified three GST proteins in T gondii, of which GST2 acts as a membrane protein that localizes to the Golgi-endosomal system and colocalizes with proteins involved in vesicle transport as well, including synaptobrevin, putative sortilin (VPS10), Rab5 and Rab6, which function as vesicle transport factors. Moreover, the loss of TgGST2 leads to Rab5 and Rab6 distribution of discrete puncta, and incorrect localization and decreased expression of several secretory proteins, and to significantly reduced invasion capacity and virulence to mice. Consistent with its relation to vesicle transport proteins, the distribution of TgGST2 relies on post-Golgi trafficking. Overall, our findings demonstrated that TgGST2 contributes to vesicle trafficking and plays a critical role in parasite lytic cycle.

The role of GSTπ isoform in the cells signalling and anticancer therapy.

The glutathione S-transferases (GSTs) overexpression in hyperproliferating tumour cells resistant to chemotherapy was demonstrated. An increased GST-π activity weakens the efficacy of anti-cancer drugs by promoting their efflux from cells. This review summarises available information on the physiological role of GSTs, in particular the role of GST-π, in regulation of signalling pathways mechanisms and cellular homeostasis for understanding and explaining the basis for GST-π application as a target for anticancer therapy and implications for clinical practice. GST-π can weaken the effect of TNF receptor-associated factor 2 (TRAF2) on apoptosis signal-regulating kinase-1 by inactivation of MAP kinase pathways (c-Jun N-terminal, p38 kinases). GST-π is involved in the metabolism of endogenous lipids mediators, such as 15-detoxy-Δ12,14-prostaglandin J2 (15d-PGJ2). Reduced binding of 15d-PGJ2 to peroxisome proliferator-activated receptors accompanied by GST-π can result in the inhibition of apoptosis. GSTP1 RNA is able to increase the phosphorylation of signal transducer and activator of transcription 3, what results in negative regulation as regards transcriptional activity thereof and affects the growth factor signalling. However, the oxidation of GST-π results in inhibition of TRAF2-GST-π complexes formation and unblocks cell apoptosis. The inhibition of multidrug resistance related proteins 1 (MRP-1) promoter activity and impairment of MRP-1 function can also act as a potent non-competitive inhibitor of GST-π. GST-π is recognised as an important target in designing new anticancer drugs. These drugs are often substrates for GST-π or have the affinity with its structure, what results in weakening its activity and achieving therapeutic goal.

The determination of Plutella xylostella (L.) GSTs (PxGSTs) involved in the detoxification metabolism of Tolfenpyrad.

Insect glutathione S-transferases (GSTs) play a crucial role in insecticide detoxification. However, there remains a distinct lack of information regarding the role of GSTs in the detoxification of Tolfenpyrad (TFP) in insects. Real-time quantitative PCR showed significant upregulation of PxGSTs after exposure to TFP for 6 h. An in vitro inhibition assay showed that TFP could inhibit PxGSTδ, PxGSTε and PxGSTσ, and the most pronounced inhibitory effect was on PxGSTσ. Metabolism assays displayed that PxGSTσ was superior to other test PxGSTs in metabolizing TFP. The molecular docking of TFP and PxGSTσ revealed that the H-bond provided by the sidechains of Tyr107 and Tyr162 were key to the detoxification of TFP by PxGSTσ. Further tests using mutant PxGSTσ proteins at the sites of Tyr107 (PxGSTσY107A) and Tyr162 (PxGSTσY162A) corroborated that the individual replacement of Tyr107 and Tyr162 could greatly weaken the binding and metabolic abilities to TFP. Metabolic interactions between the Plutella xylostella (L.) GSTs (PxGSTs) and TFP were deciphered. This study illustrates the molecular metabolism mechanism of PxGSTσ towards TFP and provides theoretical underpinnings for the design and optimization of novel TFP-like insecticides. © 2020 Society of Chemical Industry.

Role of Glutathione S-transferase (GSTM1, GSTT1) and CYP1A1 (cytochrome p450) Gene Polymorphisms in Susceptibility to Acute Myeloid Leukemia

Background: Acute myeloid leukemia (AML) may originate from the combination of genetic susceptibility factors and environmental exposure. The aim of this study was to investigate the association of GSTM1 and GSTT1 null genotypes and CYP1A1*2A allele with susceptibility to AML in an Iranian population. Method: In this case-control study, 200 patients with AML and 200 normal individuals as controls were included. GSTM1 and GSTT1 null genotypes were amplified using multiplex PCR and CYP1A1*2A polymorphisms were genotyped by PCR-RFLP. Result: The frequency of GSTM1 null genotype was significantly higher in the control group compared to the case group. The frequency of GSST1 null genotype was significantly lower in the controls. No association was observed between the studied CYP1A1*2A variant and the risk of acute myeloid leukemia. The combination of GSTT1 null genotype and CYP1A1 *2A AA and AC alleles further increased the risk of AML. Conclusion: GSTT1 null genotype can increase the risk of AML, particularly when combined with CYP1A1*2A allele. GSTM1 null genotype can also play a protective role and reduce the risk of AML. However, further studies are required on a larger number of patients.

Detection and functional characterization of sigma class GST in Phlebotomus argentipes and its role in stress tolerance and DDT resistance

Several Glutathione S-transferases (GSTs) enzymes, in insects, have previously been implicated in resistance developed against DDT and other insecticides. The GST enzyme particularly sigma class have important physiological role in detoxification of lipid peroxidation by-products in insects. Phlebotomus argentipes has been intensely exposed to DDT over years due to Indoor Residual Spray (IRS) programme for Kala-azar elimination in Bihar, India. However, in P. argentipes, role of GSTs in DDT resistance have not been elucidated. Here, sigma class GST of P. argentipes (Parg-GSTσ) was successfully cloned, expressed and purified by affinity chromatography. The recombinant Parg-GSTσ was found to be highly active towards cumene hydroperoxide and 4-HNE having specific activity 92.47 & 203.92 µM/min/mg of protein, respectively and exhibited low activity towards universal substrate CDNB i.e., 8.75 µM/min/mg of protein. RT-PCR and immunoblot analysis showed at least 2 and 1.8 fold overexpression of Parg-GSTσ in the single exposed and non exposed DDT resistant P. argentipes as compared to susceptible, implicating Parg-GSTσ also involved in DDT resistance probably by imparting enhanced stress tolerance. The DDT, H2O2 and temperature induction assays demonstrated stress-dependent induction of Parg-GSTσ expression indicating its important role in oxidative stress redressal.