Platyhelminth Mitochondrial and Cytosolic Redox Homeostasis Is Controlled by a Single Thioredoxin Glutathione Reductase and Dependent on Selenium and Glutathione

Abstract

Platyhelminth parasites are a major health problem in developing countries. In contrast to their mammalian hosts, platyhelminth thiol-disulfide redox homeostasis relies on linked thioredoxin-glutathione systems, which are fully dependent on thioredoxin-glutathione reductase (TGR), a promising drug target. TGR is a homodimeric enzyme comprising a glutaredoxin domain and thioredoxin reductase (TR) domains with a C-terminal redox center containing selenocysteine (Sec). In this study, we demonstrate the existence of functional linked thioredoxin-glutathione systems in the cytosolic and mitochondrial compartments of Echinococcus granulosus, the platyhelminth responsible for hydatid disease. The glutathione reductase (GR) activity of TGR exhibited hysteretic behavior regulated by the [GSSG]/[GSH] ratio. This behavior was associated with glutathionylation by GSSG and abolished by deglutathionylation. The Km and kcat values for mitochondrial and cytosolic thioredoxins (9.5 μm and 131 s–1, 34 μm and 197 s–1, respectively) were higher than those reported for mammalian TRs. Analysis of TGR mutants revealed that the glutaredoxin domain is required for the GR activity but did not affect the TR activity. In contrast, both GR and TR activities were dependent on the Sec-containing redox center. The activity loss caused by the Sec-to-Cys mutation could be partially compensated by a Cys-to-Sec mutation of the neighboring residue, indicating that Sec can support catalysis at this alternative position. Consistent with the essential role of TGR in redox control, 2.5 μm auranofin, a known TGR inhibitor, killed larval worms in vitro. These studies establish the selenium- and glutathione-dependent regulation of cytosolic and mitochondrial redox homeostasis through a single TGR enzyme in platyhelminths. Platyhelminth parasites are a major health problem in developing countries. In contrast to their mammalian hosts, platyhelminth thiol-disulfide redox homeostasis relies on linked thioredoxin-glutathione systems, which are fully dependent on thioredoxin-glutathione reductase (TGR), a promising drug target. TGR is a homodimeric enzyme comprising a glutaredoxin domain and thioredoxin reductase (TR) domains with a C-terminal redox center containing selenocysteine (Sec). In this study, we demonstrate the existence of functional linked thioredoxin-glutathione systems in the cytosolic and mitochondrial compartments of Echinococcus granulosus, the platyhelminth responsible for hydatid disease. The glutathione reductase (GR) activity of TGR exhibited hysteretic behavior regulated by the [GSSG]/[GSH] ratio. This behavior was associated with glutathionylation by GSSG and abolished by deglutathionylation. The Km and kcat values for mitochondrial and cytosolic thioredoxins (9.5 μm and 131 s–1, 34 μm and 197 s–1, respectively) were higher than those reported for mammalian TRs. Analysis of TGR mutants revealed that the glutaredoxin domain is required for the GR activity but did not affect the TR activity. In contrast, both GR and TR activities were dependent on the Sec-containing redox center. The activity loss caused by the Sec-to-Cys mutation could be partially compensated by a Cys-to-Sec mutation of the neighboring residue, indicating that Sec can support catalysis at this alternative position. Consistent with the essential role of TGR in redox control, 2.5 μm auranofin, a known TGR inhibitor, killed larval worms in vitro. These studies establish the selenium- and glutathione-dependent regulation of cytosolic and mitochondrial redox homeostasis through a single TGR enzyme in platyhelminths. The control of parasitic infections, which are a major cause of disability, mortality, and economic losses in many developing countries, remains as one of the most important challenges for medicine in the 21st century (1WHOPreventive Chemotherapy in Human Helminthiasis: Coordinated Use of Antihelminthic Drugs in Control Interventions: a Manual for Health Professionals and Programme Managers. WHO Press, World Health Organization, Geneva, Switzerland2006Google Scholar). In the case of the phylum platyhelminthes (flatworms), which include the causative agents of schistosomiasis (bilharzia) and hydatid disease, pharmacotherapy with praziquantel has met great success in the treatment of infection. However, drug resistance is a serious issue as it has been the case for other antiparasitic drugs (2Mansour T. Mansour T Chemotherapeutic Targets in Parasites: Contemporary Strategies. University Press, Cambridge, Cambridge2002: 58-89Google Scholar). In the case of platyhelminths, this may have severe consequences, because praziquantel is the only drug that is readily available for large scale treatment of these infections (3Doenhoff M.J. Pica-Mattoccia L. Expert Rev. Anti Infect. Ther. 2006; 4: 199-210Crossref PubMed Scopus (143) Google Scholar). Thus, the need for new drugs and/or vaccines is of great importance. In recent years, evidence has accrued that the selenocysteine (Sec) 2The abbreviations used are: Sec, selenocysteine; DMEM, Dulbecco's modified Eagle's medium; DTNB, 5,5′-dithiobis(2-dinitrobenzoic acid); DTT, dithiothreitol; EGFP, enhanced green fluorescent protein; GR, glutathione reductase; Grx, glutaredoxin; GSSG, glutathione(oxidizedform); TGR, thioredoxinglutathione reductase; TR, thioredoxin reductase; Trx, thioredoxin; SECIS, selenocysteine insertion sequence; mtTrx, mitochondrial Trx; cTrx, cytosolic Trx. -containing enzyme thioredoxin glutathione reductase (TGR) is essential for platyhelminth parasites and has emerged as a rational target for chemotherapy and/or immunotherapy (4Alger H.M. Williams D.L. Mol. Biochem. Parasitol. 2002; 121: 129-139Crossref PubMed Scopus (147) Google Scholar, 5Agorio A. Chalar C. Cardozo S. Salinas G. J. Biol. Chem. 2003; 278: 12920-12928Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar, 6Rendón J.L. del Arenal I.P. Guevara-Flores A. Uribe A. Plancarte A. Mendoza-Hernández G. Mol. Biochem. Parasitol. 2004; 133: 61-69Crossref PubMed Scopus (70) Google Scholar, 7Salinas G. Selkirk M.E. Chalar C. Maizels R.M. Fernández C. Trends Parasitol. 2004; 20: 340-346Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar, 8Kuntz A.N. Davioud-Charvet E. Sayed A.A. Califf L.L. Dessolin J. Arnér E.S. Williams D.L. PLoS Med. 2007; 4: e206Crossref PubMed Scopus (295) Google Scholar). In most organisms, including the mammalian hosts of platyhelminths, cellular redox homeostasis, antioxidant defenses, and supply of reducing equivalents to several targets and essential enzymes rely on two major pathways: the glutathione (GSH) and the thioredoxin (Trx) systems, which have overlapping and differential targets and functions (9Fernandes A.P. Holmgren A. Antioxid. Redox Signal. 2004; 6: 63-74Crossref PubMed Scopus (539) Google Scholar, 10Winyard P.G. Moody C.J. Jacob C. Trends Biochem. Sci. 2005; 30: 453-461Abstract Full Text Full Text PDF PubMed Scopus (216) Google Scholar). In contrast, platyhelminth parasites lack conventional thioredoxin reductase (TR) and glutathione reductase (GR), and hence conventional Trx and GSH systems (4Alger H.M. Williams D.L. Mol. Biochem. Parasitol. 2002; 121: 129-139Crossref PubMed Scopus (147) Google Scholar, 6Rendón J.L. del Arenal I.P. Guevara-Flores A. Uribe A. Plancarte A. Mendoza-Hernández G. Mol. Biochem. Parasitol. 2004; 133: 61-69Crossref PubMed Scopus (70) Google Scholar, 7Salinas G. Selkirk M.E. Chalar C. Maizels R.M. Fernández C. Trends Parasitol. 2004; 20: 340-346Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar). Instead, they rely exclusively on linked thioredoxin-glutathione systems, with TGR being the key enzyme that provides reducing equivalents to both pathways. Another feature of the linked systems in platyhelminths is that cytosolic and mitochondrial TGR derive from a single gene and have identical sequence, once the leader peptide of the mitochondrial variant is removed (5Agorio A. Chalar C. Cardozo S. Salinas G. J. Biol. Chem. 2003; 278: 12920-12928Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar). In the mammalian hosts, different thioredoxin reductase isozymes function in the cytosol and the mitochondria (11Turanov A.A. Su D. Gladyshev J. Biol. Chem. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar, A. G. J. Biochem. PubMed Scopus Google TGR is to L. S. Gladyshev Sci. S. A. PubMed Scopus Google and GR as a gene M.J. Biochem. PubMed Scopus Google Scholar). In the of redox as with their hosts, the lack of systems, and the that parasitic are not only to the but to the by the a to target platyhelminth studies support this of TGR by caused of the platyhelminth and auranofin, a of TGR and Sec-containing S. Williams J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google caused a in A.N. Davioud-Charvet E. Sayed A.A. Califf L.L. Dessolin J. Arnér E.S. Williams D.L. PLoS Med. 2007; 4: e206Crossref PubMed Scopus (295) Google Scholar). TGR a of conventional TR domains with a glutaredoxin domain L. S. Gladyshev Sci. S. A. PubMed Scopus Google Scholar, D.L. Gladyshev J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). TGR, GR and TR, is a with in a on the of the of for TGR that from to to the redox center to Echinococcus to the C-terminal is redox center of the and to the redox center of the domain of the The fully enzyme can Trx the C-terminal GSSG through the redox center of the domain L. S. Gladyshev Sci. S. A. PubMed Scopus Google Scholar, Su D. D.L. Gladyshev 2005; PubMed Scopus Google Scholar). a of S. TGR has been on the GR activity of the the alternative in which GSSG could be by the redox center of TR domains G. D. A. Google Scholar). In the study, we have the linked thioredoxin-glutathione of the platyhelminth E. granulosus, the causative of hydatid disease. the of functional linked systems in both cytosol and The of activities of TGR mutants revealed that the domain is required for the GR but not affect the TR in contrast, both and glutathione-dependent activities selenocysteine (Sec) that [GSSG]/[GSH] TGR activities and that is in this In we that larval worms are killed by of auranofin, a TGR inhibitor, and in of the that have been to the GR activity of the of the mitochondrial of Trx and TGR, were In the case of Trx, the was from and the including the leader was as to In the case of TGR the of mitochondrial TGR, containing the leader peptide by the domain of TGR, was as In both a was in the for of at the were in with in the of and were in to the was of Trx mitochondrial TGR used as a and of were in for The was with a containing a of the mitochondrial were for and with were by were for of TGR is Sec, and is the C-terminal and the to to to and to Sec as as a the domain of TGR In from E. was used as a for and and and were from the TGR (5Agorio A. Chalar C. Cardozo S. Salinas G. J. Biol. Chem. 2003; 278: 12920-12928Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar). In the case of the were modified and of the was to Sec, because the by Sec insertion in the Thus, for these the at the the of at a from the of for are in This with a has been used for C-terminal Sec in E. E.S. Holmgren A. A. J. Mol. Biol. PubMed Scopus Google Scholar). The were and the were to were used to E. in the case of with a that of in Sec and and E.S. Holmgren A. A. J. Mol. Biol. PubMed Scopus Google Scholar). of was the in a L. E. A. Arnér E.S. 2004; PubMed Scopus Google which has been for of of was with μm at at were in modified to a S. Biol. Med. 30: PubMed Scopus Google with and S. J. A. PubMed Scopus Google in the of and the was used only in the case of the and the of the was with μm and to a S. Biol. Med. 30: PubMed Scopus Google Scholar). that did not Sec and the was that the was not The were and the were in modified containing and and of with The were for at and were to a with and with The were to containing the were at and were at and The of was by a in Analysis University of The of the was by reducing and by on a cytosolic and mitochondrial E. were by from larval as and for cytosolic and the mitochondrial Trx were from C. C. A. Salinas G. J. Biochem. PubMed Scopus Google and from The were and were used to E. of was the for of were on in the of and of was with μm at for at The were and the were and as for TGR, that containing the were at to was at and for cytosolic and mitochondrial Trx, The of the was by reducing and by on a with E. the different were at and the was with activity of University of was to at a of of at were and by in containing were to by of a was with a for Trx of two of by Trx in the of was used as a of Trx to a A. J. Biol. Chem. Full Text PDF PubMed Google Scholar). The was by the in at to the of The DTT, μm and in with were as for TR of with was by the in at to of at E.S. L. Holmgren A. PubMed Scopus Google Scholar). The DTNB, and in for TR of TR activity of the of Trx by TR, which is by the in at in this of is used as to a of Trx E.S. L. Holmgren A. PubMed Scopus Google Scholar). The and E. cytosolic mitochondrial Trx from to μm and from to in The of TGR with cytosolic and mitochondrial Trx, were from of from GR GR activity was as of glutathione which is as the in at PubMed Scopus Google Scholar). The GSSG, in were in a at of the were TGR were with GSSG in the of at which was was not μm GSSG, respectively) in containing and through a were with and to by The was at the In of from of a single hydatid from were several with and at in with and were with and μm with the in the of μm were the and was by of the of Trx and TGR the of both cytosolic and mitochondrial of TGR and Trx, with TGR from a single and two for Trx The of in mammalian of the mitochondrial of Trx and TGR are in with indicating that the of these the to the mitochondrial of the cytosol other compartments was TGR has been to be in the mitochondrial of a larval (5Agorio A. Chalar C. Cardozo S. Salinas G. J. Biol. Chem. 2003; 278: 12920-12928Abstract Full Text Full Text PDF PubMed Scopus (61) Google the mitochondrial of Trx was to in in platyhelminths G. Selkirk M.E. Chalar C. Maizels R.M. Fernández C. Trends Parasitol. 2004; 20: 340-346Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar). TGR to and Trx to the of TGR with the of was in several the of TGR and and of cytosolic and mitochondrial Trx was by reducing and by not In the case of Sec was by of the with The are in and at the was exclusively in the indicating that were In the of was Sec was to in for for and for these that the was to TGR in a higher of Sec to have been reported this for other E.S. Holmgren A. A. J. Mol. Biol. PubMed Scopus Google Scholar). only a of the TGR Sec to of at Sec of were to their The activities of TGR and Trx were of the and enzymes activity in these not the the of TGR with cytosolic and mitochondrial Trx, were from of Km and kcat values were of the for both The of TGR was and for mitochondrial and cytosolic Trx, of TGR and Km kcat in a new Sec but the for TR the role of the domain and of Sec at the C-terminal redox center of TGR in the we a of TGR TGR the to to and to Sec and to Analysis of TR activity with the in and in revealed that and TGR have activity at enzyme not a kcat than two of than that of The with Sec and at a kcat one of higher than that of the to the of the mutants with mitochondrial Trx. The are in The of the Sec to was 2.5 of than that of the TGR, the was one of higher than the TR the domain did not affect the TR the C-terminal Sec was essential for this activity. a Sec at the of the C-terminal redox center could partially for the loss of activity to Sec to GR on the of and hysteretic behavior the existence of a catalysis of the GR activity of TGR was reported for the TGR of platyhelminth J.L. del Arenal I.P. Guevara-Flores A. Uribe A. Plancarte A. Mendoza-Hernández G. Mol. Biochem. Parasitol. 2004; 133: 61-69Crossref PubMed Scopus (70) Google Scholar). This behavior has not been reported for E. granulosus, S. mammalian TGR (5Agorio A. Chalar C. Cardozo S. Salinas G. J. Biol. Chem. 2003; 278: 12920-12928Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar, L. S. Gladyshev Sci. S. A. PubMed Scopus Google Scholar, H.M. Sayed A.A. M.J. Williams D.L. J. Parasitol. 2002; PubMed Scopus Google Scholar). that E. TGR exhibited hysteretic behavior for GR which at TGR GSSG the were to those for T. TGR, the E. TGR exhibited for J.L. del Arenal I.P. Guevara-Flores A. Uribe A. Plancarte A. Mendoza-Hernández G. Mol. Biochem. Parasitol. 2004; 133: 61-69Crossref PubMed Scopus (70) Google that of TGR with GSH the hysteretic behavior of the that was not to GR of E. TGR the with the of GSSG, and with the of the of the did not once the enzyme was fully and Trx can GR and that μm Trx, abolished the hysteretic behavior GR by J.L. del Arenal I.P. Guevara-Flores A. Uribe A. Plancarte A. Mendoza-Hernández G. Mol. Biochem. Parasitol. 2004; 133: 61-69Crossref PubMed Scopus (70) Google have that TGR two one of with for of E. TGR to a glutathione and that TGR associated with the [GSSG]/[GSH] the activity of the we that TGR may be by GSSG at and by Thus, we TGR with and GSSG for at which the enzyme is and for enzyme is the enzymes to and The that TGR is at two and with GSSG and of did not In contrast, with GSSG and TGR was to be In glutathionylation was TGR was for with μm GSSG which is with In the to the those of the redox center of TGR were as they were to be including the Sec-containing peptide could not be the that the enzyme is at GSSG and that it once the enzyme is the TR activity was in TGR at at which the GR activity was it is not to the TR activity of TGR in the of GSSG, we TGR with GSSG for which is GR and and the TGR to a to the TR activity of this TGR by both the and not hysteretic In contrast, the GR activity of the TGR was at GSSG which is the enzyme was not In we domain to this we glutathionylation and TR activity of at that the TR activity was at the the peptide containing was not in the and the Sec for GR the GR activity was by the domain and the Sec at the C-terminal redox center. and did not activity at the of the at of enzymes the of for the GR activity is dependent not only on the enzyme but on GSSG and GSH we the activity of these mutants at enzyme and different of GSSG and in the of of these enzymes exhibited activity at GSSG and of GSH did not affect the activity not these that the C-terminal and redox are essential for GR activity. and to was for the TR the exhibited GR activity the of GSH on the GR activity of the of GSSG the of GSH abolished we a of functional TR domains with functional domain GR activity. activity was at of both indicating that these two is not This the that the with to functional TR domains in and to the in these can affect the GR activity of these a TGR at glutathione and thioredoxin activities on TGR in both mitochondria and we in the of on were of μm The of was the of the drug of the μm auranofin, of were at and at 2.5 μm auranofin, were at μm auranofin, of but was the of on to μm of only at μm studies have that TGR is essential enzyme in platyhelminth parasites and target for drug and/or A.N. Davioud-Charvet E. Sayed A.A. Califf L.L. Dessolin J. Arnér E.S. Williams D.L. PLoS Med. 2007; 4: e206Crossref PubMed Scopus (295) Google Scholar). In this study, we evidence that TGR as a key platyhelminth to target. have that cytosolic and mitochondrial of TGR from E. derive from a single gene and have the sequence, once the leader peptide of the mitochondrial is by in that the mitochondrial variant of TGR and a mitochondrial Trx from E. to the mitochondrial by evidence for mitochondrial of platyhelminth TGR and Trx been that TGR provides to E. cytosolic and mitochondrial as as to GSSG, indicating the existence of functional systems in cytosol and TGR functions with both Trx with a of s–1, to the values reported for other and TRs. The Km and kcat values for are higher than those reported for mammalian μm and to s–1, respectively) S. Williams J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. D.L. M.J. Gladyshev and in Human Scopus Google Scholar, L. Holmgren A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). However, Km values of the of the to E. and S. are higher than those for mammalian TRs. The reported kcat values for these are than the reported for E. TGR, but it be that by have been in those J.L. del Arenal I.P. Guevara-Flores A. Uribe A. Plancarte A. Mendoza-Hernández G. Mol. Biochem. Parasitol. 2004; 133: 61-69Crossref PubMed Scopus (70) Google Scholar, 8Kuntz A.N. Davioud-Charvet E. Sayed A.A. Califf L.L. Dessolin J. Arnér E.S. Williams D.L. PLoS Med. 2007; 4: e206Crossref PubMed Scopus (295) Google Scholar). of the GR activity of E. TGR we that at the enzyme exhibited hysteretic we that the [GSSG]/[GSH] the activity of the the with GSSG and with GSH behavior has been associated with in and/or in to C. J. Biol. Chem. Full Text PDF PubMed Google Scholar). did not in the of TGR of the enzyme with GSSG by not that the hysteretic to the glutathionylation of TGR as in evidence that the hysteretic behavior of TGR was to glutathionylation from the once GSSG was removed a the enzyme was hysteretic at GSSG the two to be is in and in Grx, is only in E. TGR is to the of domains and is to a G. D. A. Google Scholar). have been to of target M.J. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, C. Holmgren A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, A. A. Holmgren A. J. Biol. Chem. 2003; 278: Full Text Full Text PDF PubMed Scopus Google Scholar). Thus, issue to is by of TGR by GSH in the of not This that these can but catalysis by the domain be TGR and at the activity is by the [GSSG]/[GSH] it to regulation by as as and The that is at GSSG the of this in be that parasites are to the This not only GSSG, but and glutathione and which have been as glutathione and for 2007; PubMed Scopus Google Scholar). of has been to in mammalian (9Fernandes A.P. Holmgren A. Antioxid. Redox Signal. 2004; 6: 63-74Crossref PubMed Scopus (539) Google Scholar, M.J. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, 2007; PubMed Scopus Google and to a for the of agents 2007; PubMed Scopus Google Scholar, T. J. 2007; PubMed Scopus Google Scholar). that TGR activity is for of Trx these TGR be for the GR the TR function the of TR and GR activities of TGR, we a of to the of C-terminal redox center and the Consistent with the for mammalian TGR Su D. D.L. Gladyshev 2005; PubMed Scopus Google we that the Sec of TGR is essential for both The Sec to at the has GR and TR a Sec to mutation in a loss of TR activity and loss of GR activity. These that in E. the redox homeostasis is by TGR and is dependent on was that the mutation at the C-terminal redox center partially compensated for the loss of activity caused by the single Sec to mutation This of activity was with DTNB, and redox are by the of Sec at the and a is at the of the Su D. D.L. Gladyshev 2005; PubMed Scopus Google Scholar, A.A. Gladyshev Sci. S. A. 2005; PubMed Scopus Google Scholar, A.A. Gladyshev 2006; PubMed Scopus Google Scholar, A.P. 2007; PubMed Scopus Google Scholar). The higher and of the of Sec S. L. S. Williams Arnér E.S. Sci. S. A. 2003; PubMed Scopus Google are to Sec a at the position. In recent evidence the that Sec is the of the the A.P. 2007; PubMed Scopus Google Scholar). with Sec at the has been D.L. M.J. Gladyshev and in Human and it is that Sec not a to the at this position. a mammalian TR with C-terminal in in activity to the Sec to A.P. 2007; PubMed Scopus Google Scholar). that Sec not only provides a at the but a to Sec mutation at the can activity with the The that Sec is to at the of the redox center may to other and the be to this in the of enzymes for enhanced the role of the domain in TGR the of TGR and TR revealed that the domain not affect the TR activity of the indicating that the domain the TR activity of In contrast, the TR of TGR has GR and both the and TR domains are for this activity. that GSSG both the C-terminal Sec-containing redox center and the in with the for mammalian TGR L. S. Gladyshev Sci. S. A. PubMed Scopus Google and by of the enzyme Su D. D.L. Gladyshev 2005; PubMed Scopus Google Scholar). This that can from the C-terminal redox center to Trx, to the redox center of the domain and to This that a to Trx the domain to from the C-terminal redox center. alternative for GSSG has been on the of a S. for the GR activity of the the that GSSG could be by the redox center of TR domains G. D. A. Google Scholar). The that auranofin, of Sec-containing and not only TR but GR activities of S. TGR, that the alternative is and is to be A.N. Davioud-Charvet E. Sayed A.A. Califf L.L. Dessolin J. Arnér E.S. Williams D.L. PLoS Med. 2007; 4: e206Crossref PubMed Scopus (295) Google Scholar, H.M. Sayed A.A. M.J. Williams D.L. J. Parasitol. 2002; PubMed Scopus Google Scholar). we in studies on E. larval worms to the of as as 2.5 μm of larval worms and in of larval worms The of the drug on larval worms with was of have been reported to and S. in are to higher of A.N. Davioud-Charvet E. Sayed A.A. Califf L.L. Dessolin J. Arnér E.S. Williams D.L. PLoS Med. 2007; 4: e206Crossref PubMed Scopus (295) Google Scholar). available that in platyhelminth parasites the of thiol-disulfide redox homeostasis from that of their mammalian In platyhelminths, the redox homeostasis is by TGR and is dependent on The of conventional Trx and GSH systems by linked systems TGR for Trx and glutathione-dependent a target for drug In this study, we the existence of functional linked systems in both mitochondria and the cytosol that on a single Thus, this enzyme can be to the cellular redox homeostasis in these the of from Arnér for and and Fernández for the for with with