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Cai L, Dang M, Yang Y, Mei R, Li F, Tao X, Palukaitis P, Beckett R, Miller WA, Gray SM, Xu Y. Naturally occurring substitution of an amino acid in a plant virus gene-silencing suppressor enhances viral adaptation to increasing thermal stress. PLoS Pathog 2023; 19:e1011301. [PMID: 37011127 PMCID: PMC10101640 DOI: 10.1371/journal.ppat.1011301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 04/13/2023] [Accepted: 03/16/2023] [Indexed: 04/05/2023] Open
Abstract
Cereal yellow dwarf virus (CYDV-RPV) encodes a P0 protein that functions as a viral suppressor of RNA silencing (VSR). The strength of silencing suppression is highly variable among CYDV-RPV isolates. In this study, comparison of the P0 sequences of CYDV-RPV isolates and mutational analysis identified a single C-terminal amino acid that influenced P0 RNA-silencing suppressor activity. A serine at position 247 was associated with strong suppressor activity, whereas a proline at position 247 was associated with weak suppressor activity. Amino acid changes at position 247 did not affect the interaction of P0 with SKP1 proteins from Hordeum vulgare (barley) or Nicotiana benthamiana. Subsequent studies found P0 proteins containing a P247 residue were less stable than the P0 proteins containing an S247 residue. Higher temperatures contributed to the lower stability and in planta and the P247 P0 proteins were subject to degradation via the autophagy-mediated pathway. A P247S amino acid residue substitution in P0 increased CYDV-RPV replication after expression in agroinfiltrated plant leaves and increased viral pathogenicity of P0 generated from the heterologous Potato virus X expression vector system. Moreover, an S247 CYDV-RPV could outcompete the P247 CYDV-RPV in a mixed infection in natural host at higher temperature. These traits contributed to increased transmission by aphid vectors and could play a significant role in virus competition in warming climates. Our findings underscore the capacity of a plant RNA virus to adapt to climate warming through minor genetic changes in gene-silencing suppressor, resulting in the potential for disease persistence and prevalence.
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Affiliation(s)
- Lina Cai
- Department of Plant Pathology, Nanjing Agricultural University, Jiangsu Province, China
| | - Mingqing Dang
- Department of Plant Pathology, Nanjing Agricultural University, Jiangsu Province, China
| | - Yawen Yang
- Department of Plant Pathology, Nanjing Agricultural University, Jiangsu Province, China
| | - Ruoxin Mei
- Department of Plant Pathology, Nanjing Agricultural University, Jiangsu Province, China
| | - Fan Li
- State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming, China
| | - Xiaorong Tao
- Department of Plant Pathology, Nanjing Agricultural University, Jiangsu Province, China
| | - Peter Palukaitis
- Department of Horticultural Sciences, Seoul Women's University, Nowon-gu, Seoul, Republic of Korea
| | - Randy Beckett
- Department of Plant Pathology, Entomology and Microbiology, Iowa State University, Ames, Iowa, United States of America
| | - W Allen Miller
- Department of Plant Pathology, Entomology and Microbiology, Iowa State University, Ames, Iowa, United States of America
| | - Stewart M Gray
- Plant Pathology and Plant-Microbe Biology Section, School of Integrated Plant Science, Cornell University, Ithaca, New York, United States of America
- Emerging Pests and Pathogens Research Unit, USDA, ARS, Ithaca, New York, United States of America
| | - Yi Xu
- Department of Plant Pathology, Nanjing Agricultural University, Jiangsu Province, China
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Köhrle J, Frädrich C. Deiodinases control local cellular and systemic thyroid hormone availability. Free Radic Biol Med 2022; 193:59-79. [PMID: 36206932 DOI: 10.1016/j.freeradbiomed.2022.09.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 09/21/2022] [Accepted: 09/21/2022] [Indexed: 11/17/2022]
Abstract
Iodothyronine deiodinases (DIO) are a family of selenoproteins controlling systemic and local availability of the major thyroid hormone l-thyroxine (T4), a prohormone secreted by the thyroid gland. T4 is activated to the active 3,3'-5-triiodothyronine (T3) by two 5'-deiodinases, DIO1 and DIO2. DIO3, a 5-deiodinase selenoenzyme inactivates both the prohormone T4 and its active form T3. DIOs show species-specific different patterns of temporo-spatial expression, regulation and function and exhibit different mechanisms of reaction and inhibitor sensitivities. The main regulators of DIO expression and function are the thyroid hormone status, several growth factors, cytokines and altered pathophysiological conditions. Selenium (Se) status has a modest impact on DIO expression and translation. DIOs rank high in the priority of selenium supply to various selenoproteins; thus, their function is impaired only during severe selenium deficiency. DIO variants, polymorphisms, SNPs and rare mutations have been identified. Development of DIO isozyme selective drugs is ongoing. A first X-ray structure has been reported for DIO3. This review focusses on the biochemical characteristics and reaction mechanisms, the relationships between DIO selenoproteins and their importance for local and systemic provision of the active hormone T3. Nutritional, pharmacological, and environmental factors and inhibitors, such as endocrine disruptors, impact DIO functions.
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Affiliation(s)
- Josef Köhrle
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt- Universität zu Berlin, Max Rubner Center (MRC) für Kardiovaskuläre-metabolische-renale Forschung in Berlin, Institut für Experimentelle Endokrinologie, 10115, Berlin, Germany.
| | - Caroline Frädrich
- Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt- Universität zu Berlin, Max Rubner Center (MRC) für Kardiovaskuläre-metabolische-renale Forschung in Berlin, Institut für Experimentelle Endokrinologie, 10115, Berlin, Germany
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3
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Schweizer U, Steegborn C. New insights into the structure and mechanism of iodothyronine deiodinases. J Mol Endocrinol 2015; 55:R37-52. [PMID: 26390881 DOI: 10.1530/jme-15-0156] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/16/2015] [Indexed: 12/30/2022]
Abstract
Iodothyronine deiodinases are a family of enzymes that remove specific iodine atoms from one of the two aromatic rings in thyroid hormones (THs). They thereby fine-tune local TH concentrations and cellular TH signaling. Deiodinases catalyze a remarkable biochemical reaction, i.e., the reductive elimination of a halogenide from an aromatic ring. In metazoans, deiodinases depend on the rare amino acid selenocysteine. The recent solution of the first experimental structure of a deiodinase catalytic domain allowed for a reappraisal of the many mechanistic and mutagenesis data that had been accumulated over more than 30 years. Hence, the structure generates new impetus for research directed at understanding catalytic mechanism, substrate specificity, and regulation of deiodinases. This review will focus on structural and mechanistic aspects of iodothyronine deiodinases and briefly compare these enzymes with dehalogenases, which catalyze related reactions. A general mechanism for the selenium-dependent deiodinase reaction will be described, which integrates the mouse deiodinase 3 crystal structure and biochemical studies. We will summarize further, sometimes isoform-specific molecular features of deiodinase catalysis and regulation, and we will then discuss available compounds for modulating deiodinase activity for therapeutic purposes.
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Affiliation(s)
| | - Clemens Steegborn
- Institut für Biochemie und MolekularbiologieRheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 11, 53115 Bonn, GermanyLehrstuhl BiochemieUniversität Bayreuth, Universitätsstrasse 30, 95445 Bayreuth, Germany
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4
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Guo C, Chen X, Song H, Maynard MA, Zhou Y, Lobanov AV, Gladyshev VN, Ganis JJ, Wiley D, Jugo RH, Lee NY, Castroneves LA, Zon LI, Scanlan TS, Feldman HA, Huang SA. Intrinsic expression of a multiexon type 3 deiodinase gene controls zebrafish embryo size. Endocrinology 2014; 155:4069-80. [PMID: 25004091 PMCID: PMC4164935 DOI: 10.1210/en.2013-2029] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thyroid hormone is a master regulator of differentiation and growth, and its action is terminated by the enzymatic removal of an inner-ring iodine catalyzed by the selenoenzyme type 3 deiodinase (dio3). Our studies of the zebrafish reveal that the dio3 gene is duplicated in this species and that embryonic deiodination is an important determinant of embryo size. Although both dio3 paralogs encode enzymatically active proteins with high affinity for thyroid hormones, their anatomic patterns of expression are markedly divergent and only embryos with knockdown of dio3b, a biallelically expressed selenoenzyme expressed in the developing central nervous system, manifest severe thyroid hormone-dependent growth restriction at 72 hours post fertilization. This indicates that the embryonic deficiency of dio3, once considered only a placental enzyme, causes microsomia independently of placental physiology and raises the intriguing possibility that fetal abnormalities in human deiodination may present as intrauterine growth retardation. By mapping the gene structures and enzymatic properties of all four zebrafish deiodinases, we also identify dio3b as the first multiexon dio3 gene, containing a large intron separating its open reading frame from its selenocysteine insertion sequence (SECIS) element.
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Affiliation(s)
- Cuicui Guo
- State Key Laboratory of Medical Genomics (C.G., X.C., H.S.), Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 200025 China; Thyroid Program of the Division of Endocrinology (C.G., X.C., H.S., M.A.M., R.H.J., N.Y.L., L.A.C., S.A.H.) and Clinical Research Center (H.A.F.), Boston Children's Hospital; Stem Cell Program and Division of Hematology/Oncology (Y.Z., J.J.G., D.W., L.I.Z.), Boston Children's Hospital, Harvard Stem Cell Institute, Harvard Medical School, and Howard Hughes Medical Institute; Department of Medicine (A.V.L., V.N.G., S.A.H.), Brigham and Women's Hospital; Dana Farber Cancer Institute (V.N.G., L.I.Z., S.A.H.), Boston, Massachusetts 02115; and Departments of Physiology and Pharmacology (T.S.S.), Oregon Health and Science University, Portland, Oregon 97239
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Dora JM, Wajner SM, Costa JD, Pinto Ribeiro RV, Leiria LB, Lopes MG, Vitali da Silva A, Crispim D, Maia AL. Type 2 deiodinase Thr92Ala polymorphism is associated with disrupted placental activity but not with dysglycemia or adverse gestational outcomes: a genetic association study. Fertil Steril 2014; 101:833-9. [PMID: 24355051 DOI: 10.1016/j.fertnstert.2013.11.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 11/14/2013] [Accepted: 11/14/2013] [Indexed: 01/10/2023]
Abstract
OBJECTIVE To study whether the D2 Thr92Ala polymorphism-a genetic marker that is associated with reduced thyroid type 2 deiodinase (D2) activity, increased insulin resistance, and risk for type 2 diabetes-is associated with disrupted placental D2 activity and with glycemic control and gestational outcomes. DESIGN Cross-sectional study. SETTING Tertiary hospital in Brazil. PATIENT(S) Consecutive singleton-pregnancy patients, 18-45 years old. INTERVENTION(S) Clinical examination and genotyping of the D2 Thr92Ala polymorphism, with placental samples collected and assayed for D2 mRNA and activity. MAIN OUTCOME MEASURE(S) Glucose homeostasis and gestational outcomes. RESULT(S) A total of 294 patients were included in the study. The clinical and laboratory characteristics were similar among the D2 genotypes. No differences were observed in D2 placental mRNA levels, but D2 activity was decreased in patients with the Ala92Ala genotype (0.35 ± 0.15 vs. 1.96 ± 1.02 fmol/mg/min.). Newborn serum thyroid-stimulating hormone levels (TSHneo) did not differ according to maternal D2 Thr92Ala genotype. Also, maternal glucose control, insulin resistance evaluated by the homeostasis model assessment (HOMA-IR), and gestational outcomes did not differ across D2 genotypes. CONCLUSION(S) The D2 Ala92Ala genotype is associated with reduced placental D2 activity but is not associated with dysglycemia, increased insulin resistance, or worse gestational outcomes.
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Affiliation(s)
- José Miguel Dora
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
| | - Simone M Wajner
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Juliano Dalla Costa
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Rafaela Vanin Pinto Ribeiro
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Leonardo Barbosa Leiria
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Mariah G Lopes
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Aline Vitali da Silva
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Daisy Crispim
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Ana Luiza Maia
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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A new ABC half-transporter in Leishmania major is involved in resistance to antimony. Antimicrob Agents Chemother 2013; 57:3719-30. [PMID: 23716044 DOI: 10.1128/aac.00211-13] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The characterization of ABCI4, a new intracellular ATP-binding cassette (ABC) half-transporter in Leishmania major, is described. We show that ABCI4 is involved in heavy metal export, thereby conferring resistance to Pentostam, to Sb(III), and to As(III) and Cd(II). Parasites overexpressing ABCI4 showed a lower mitochondrial toxic effect of antimony by decreasing reactive oxygen species production and maintained higher values of both the mitochondrial electrochemical potential and total ATP levels with respect to controls. The ABCI4 half-transporter forms homodimers as determined by a coimmunoprecipitation assay. A combination of subcellular localization studies under a confocal microscope and a surface biotinylation assay using parasites expressing green fluorescent protein- and FLAG-tagged ABCI4 suggests that the transporter presents a dual localization in both mitochondria and the plasma membrane. Parasites overexpressing ABCI4 present an increased replication in mouse peritoneal macrophages. We have determined that porphyrins are substrates for ABCI4. Consequently, the overexpression of ABCI4 confers resistance to some toxic porphyrins, such as zinc-protoporphyrin, due to the lower accumulation resulting from a significant efflux, as determined using the fluorescent zinc-mesoporphyrin, a validated heme analog. In addition, ABCI4 has a significant ability to efflux thiol after Sb(III) incubation, thus meaning that ABCI4 could be considered to be a potential thiol-X-pump that is able to recognize metal-conjugated thiols. In summary, we have shown that this new ABC transporter is involved in drug sensitivity to antimony and other compounds by efflux as conjugated thiol complexes.
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Zhu B, Shrivastava A, Luongo C, Chen T, Harney JW, Marsili A, Tran TV, Bhadouria A, Mopala R, Steen AI, Larsen PR, Zavacki AM. Catalysis leads to posttranslational inactivation of the type 1 deiodinase and alters its conformation. J Endocrinol 2012; 214:87-94. [PMID: 22544951 PMCID: PMC3612969 DOI: 10.1530/joe-11-0459] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Previously, it was shown that the type 1 deiodinase (D1) is subject to substrate-dependent inactivation that is blocked by pretreatment with the inhibitor of D1 catalysis, propylthiouracil (PTU). Using HepG2 cells with endogenous D1 activity, we found that while considerable D1-mediated catalysis of reverse tri-iodothyronine (rT(3)) is observed in intact cells, there was a significant loss of D1 activity in sonicates assayed from the same cells in parallel. This rT(3)-mediated loss of D1 activity occurs despite no change in D1 mRNA levels and is blocked by PTU treatment, suggesting a requirement for catalysis. Endogenous D1 activity in sonicates was inactivated in a dose-dependent manner in HepG2 cells, with a ∼50% decrease after 10 nM rT(3) treatment. Inactivation of D1 was rapid, occurring after only half an hour of rT(3) treatment. D1 expressed in HEK293 cells was inactivated by rT(3) in a similar manner. (75)Se labeling of the D1 selenoprotein indicated that after 4 h rT(3)-mediated inactivation of D1 occurs without a corresponding decrease in D1 protein levels, though rT(3) treatment causes a loss of D1 protein after 8-24 h. Bioluminescence resonance energy transfer studies indicate that rT(3) exposure increases energy transfer between the D1 homodimer subunits, and this was lost when the active site of D1 was mutated to alanine, suggesting that a post-catalytic structural change in the D1 homodimer could cause enzyme inactivation. Thus, both D1 and type 2 deiodinase are subject to catalysis-induced loss of activity although their inactivation occurs via very different mechanisms.
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Affiliation(s)
- Bo Zhu
- Division of Endocrinology, Diabetes and Hypertension, Thyroid Section, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA
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8
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Wajner SM, Maia AL. New Insights toward the Acute Non-Thyroidal Illness Syndrome. Front Endocrinol (Lausanne) 2012; 3:8. [PMID: 22654851 PMCID: PMC3356062 DOI: 10.3389/fendo.2012.00008] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Accepted: 01/10/2012] [Indexed: 11/13/2022] Open
Abstract
The non-thyroidal illness syndrome (NTIS) refers to changes in serum thyroid hormone levels observed in critically ill patients in the absence of hypothalamic-pituitary-thyroid primary dysfunction. Affected individuals have low T3, elevated rT3, and inappropriately normal TSH levels. The pathophysiological mechanisms are poorly understood but the acute and chronic changes in pituitary-thyroid function are probably the consequence of the action of multiple factors. The early phase seems to reflect changes occurring primarily in the peripheral thyroid hormone metabolism, best seen in humans since 80-90% of the circulating T3 are derived from the pro-hormone T4. The conversion of T4 to T3 is catalyzed by type 1 (D1) and type 2 (D2) deiodinases via outer-ring deiodination. In contrast, type 3 deiodinase (D3) catalyzes the inactivation of both T4 and T3. Over the last decades, several studies have attempted to elucidate the mechanisms underlying the changes on circulating thyroid hormones in NTIS. Increased inflammatory cytokines, which occurs in response to virtually any illness, has long been speculated to play a role in derangements of deiodinase expression. On the other hand, oxidative stress due to augmented reactive oxygen species (ROS) generation is characteristic of many diseases that are associated with NTIS. Changes in the intracellular redox state may disrupt deiodinase function by independent mechanisms, which might include depletion of the as yet unidentified endogenous thiol cofactor. Here we aim to present an updated picture of the advances in understanding the mechanisms that result in the fall of thyroid hormone levels in the acute phase of NTIS.
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Affiliation(s)
- Simone Magagnin Wajner
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do SulPorto Alegre, Brasil
| | - Ana Luiza Maia
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do SulPorto Alegre, Brasil
- *Correspondence: Ana Luiza Maia, Serviço de Endocrinologia, Hospital de Clínicas de Porto Alegre, Rua Ramiro Barcelos, 2350, CEP 90035-003 Porto Alegre, Brasil. e-mail:
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Maternal Thimerosal Exposure Results in Aberrant Cerebellar Oxidative Stress, Thyroid Hormone Metabolism, and Motor Behavior in Rat Pups; Sex- and Strain-Dependent Effects. THE CEREBELLUM 2011; 11:575-86. [DOI: 10.1007/s12311-011-0319-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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10
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Klootwijk W, Friesema ECH, Visser TJ. A nonselenoprotein from amphioxus deiodinates triac but not T3: is triac the primordial bioactive thyroid hormone? Endocrinology 2011; 152:3259-67. [PMID: 21652724 DOI: 10.1210/en.2010-1408] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Thyroid hormone (TH) is important for metamorphosis in many species, including the cephalochordate Branchiostoma floridae, a marine invertebrate (amphioxus) living in warmer coastal areas. Branchiostoma expresses a TH receptor, which is activated by 3,3',5-triiodothyroacetic acid (TA(3)) but not by T(3). The Branchiostoma genome also contains multiple genes coding for proteins homologous to iodothyronine deiodinases in vertebrates, selenoproteins catalyzing the activation or inactivation of TH. Three Branchiostoma deiodinases have been cloned: two have a catalytic Sec, and one, bfDy, has a Cys residue. We have studied the catalytic properties of bfDy in transfected COS1 cells by HPLC analysis of reactions with (125)I-labeled substrates and dithiothreitol as cofactor. We could not detect deiodination of T(4), T(3), or rT(3) by bfDy but observed rapid and selective inner ring deiodination (inactivation) of TA(3) and 3,3',5,5'-tetraiodothyroacetic acid (TA(4)). Deiodination of TA(3) by bfDy was optimal at 25 C and 10 mm dithiothreitol. bfDy was extremely labile at 37 C, showing a half-life of less than 2 min, in contrast with a half-life of more than 60 min at 25 C. Deiodination of labeled TA(3) was inhibited dose dependently by unlabeled TA(3)≈TA(4)>T(4)≈T(3). Michaelis-Menten analysis yielded Michaelis-Menten constant values of 6.8 and 68 nm and maximum velocity values of 1.4 and 5.4 pmol/min·mg protein for TA(3) and TA(4), respectively. bfDy was not inhibited by propylthiouracil and iodoacetate and only weakly by goldthioglucose and iopanoic acid. In conclusion, we demonstrate rapid inactivation of TA(3) and TA(4) but not of T(3) and T(4) by the first reported natural nonselenodeiodinase. Our findings support the hypothesis that TA(3) is a primordial bioactive TH.
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Affiliation(s)
- Wim Klootwijk
- Department of Internal Medicine, Erasmus University Medical Center, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
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Wajner SM, Goemann IM, Bueno AL, Larsen PR, Maia AL. IL-6 promotes nonthyroidal illness syndrome by blocking thyroxine activation while promoting thyroid hormone inactivation in human cells. J Clin Invest 2011; 121:1834-45. [PMID: 21540553 DOI: 10.1172/jci44678] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Accepted: 02/16/2011] [Indexed: 12/19/2022] Open
Abstract
Nonthyroidal illness syndrome (NTIS) is a state of low serum 3,5,3' triiodothyronine (T₃) that occurs in chronically ill patients; the degree of reduction in T₃ is associated with overall prognosis and survival. Iodthyronine deiodinases are enzymes that catalyze iodine removal from thyroid hormones; type I and II deiodinase (D1 and D2, respectively) convert the prohormone thyroxine T₄ to active T₃, whereas the type III enzyme (D3) inactivates T₄ and T₃. Increased production of cytokines, including IL-6, is a hallmark of the acute phase of NTIS, but the role of cytokines in altered thyroid hormone metabolism is poorly understood. Here, we measured the effect of IL-6 on both endogenous cofactor-mediated and dithiothreitol-stimulated (DTT-stimulated) cell sonicate deiodinase activities in human cell lines. Active T₃ generation by D1 and D2 in intact cells was suppressed by IL-6, despite an increase in sonicate deiodinases (and mRNAs). N-acetyl-cysteine (NAC), an antioxidant that restores intracellular glutathione (GSH) concentrations, prevented the IL-6-induced inhibitory effect on D1- and D2-mediated T₃ production, which suggests that IL-6 might function by depleting an intracellular thiol cofactor, perhaps GSH. In contrast, IL-6 stimulated endogenous D3-mediated inactivation of T₃. Taken together, these results identify a single pathway by which IL-6-induced oxidative stress can reduce D1- and D2-mediated T₄-to-T₃ conversion as well as increasing D3-mediated T₃ (and T₄) inactivation, thus mimicking events during illness.
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Affiliation(s)
- Simone Magagnin Wajner
- Thyroid Section, Endocrine Division, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
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