Study for the binding affinity of thyroid hormone receptors based on machine learning algorithm.

Long-term exposure of exogenous compounds to thyroid hormone receptors (TRs) may lead to thyroid dysfunction. Quantitative structure-activity relationship (QSAR) is expected to predicting the binding affinity of compounds to TR. In this work, two comprehensive and large datasets for TRα and TRß were collected and investigated. Five machine learning models were established to predict the pIC50 of compounds. Meanwhile, the reliability of the models was ensured by a variety of evaluation parameters. The results showed that the support vector regression model exhibited the best robustness and external prediction ability (r2train = 0.77, r2test = 0.78 for TRα, r2train = 0.78, r2test = 0.80 for TRß). We have proposed an appropriate mechanism for explaining the TR binding affinity of a compound. The molecular volume, mass, and aromaticity affected the activity of TRα. Molecular weight, electrical properties and molecular hydrophilicity played a significant role in the binding affinity of compounds to TRß. We also characterized the application domain of the model. Finally, the obtained models were utilized to predict the TR binding affinities of 109 compounds from the list of endocrine disruptors. Therefore, this model is expected to be an effective tool for alerting the effects of exogenous compounds on the thyroid system.

Secretory expression of thyroid hormone receptor using transgenic silkworms and its DNA binding activity.

Silkworms are economically important insects that have the ability to produce large amounts of silk. They have mass breeding methods and silk glands, which are specialized tissues that secrete silk fibroin and sericin. Thus, the production of recombinant proteins in a transgenic silkworm system is a promising approach. We developed a silkworm, Bombyx mori, as a host expression insect for recombinant proteins and successfully produced different proteins including antibodies, glycoproteins, and membrane receptors. The thyroid hormone receptor (TR) is a regulatory factor for many physiological phenomena. It is a lipophilic protein that has DNA-binding and ligand-binding domains. Based on our previous experiences, it was inferred that the recombinant TR easily formed aggregates and precipitates which is potentially due to an unstructured hinge domain. We applied the silkworm expression system to produce mice TRß1 that was fused with glutathione S-transferase. Using 160 larvae, the yield of the recombinant GST-TRß was approximately 4 mg, and the purified GST-TRß completely retained its physiological activity. Our results indicated that the recombinant TRß was secreted extracellularly using the silk fibroin signal peptide sequence. Moreover, we found that the expression system of silkworms was applicable to nuclear proteins.

The Affinity of Brominated Phenolic Compounds for Human and Zebrafish Thyroid Receptor ß: Influence of Chemical Structure.

Brominated phenolic compounds (BPCs) are found in the environment, and in human and wildlife tissues, and some are considered to have endocrine disrupting activities. The goal of this study was to determine how structural differences of 3 BPC classes impact binding affinities for the thyroid receptor beta (TRß) in humans and zebrafish. BPC classes included halogenated bisphenol A derivatives, halogenated oxidative transformation products of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), and brominated phenols. Affinities were assessed using recombinant TRß protein in competitive binding assays with 125I-triiodothyronine (125I-T3) as the radioligand. Zebrafish and human TRß displayed similar binding affinities for T3 (Ki = 0.40 and 0.49 nM) and thyroxine (T4, Ki = 6.7 and 6.8 nM). TRß affinity increased with increasing halogen mass and atomic radius for both species, with the iodinated compounds having the highest affinity within their compound classes. Increasing halogen mass and radius increases the molecular weight, volume, and hydrophobicity of a compound, which are all highly correlated with increasing affinity. TRß affinity also increased with the degree of halogenation for both species. Human TRß displayed higher binding affinities for the halogenate bisphenol A compounds, whereas zebrafish TRß displayed higher affinities for 2,4,6-trichlorophenol and 2,4,6-trifluorophenol. Observed species differences may be related to amino acid differences within the ligand binding domains. Overall, structural variations impact TRß affinities in a similar manner, supporting the use of zebrafish as a model for TRß disruption. Further studies are necessary to investigate how the identified structural modifications impact downstream receptor activities and potential in vivo effects.

Editor's Highlight: Structure-Based Investigation on the Binding and Activation of Typical Pesticides With Thyroid Receptor.

A broad range of pesticides have been reported to interfere with the normal function of the thyroid endocrine system. However, the precise mechanism(s) of action has not yet been thoroughly elucidated. In this study, 21 pesticides were assessed for their binding interactions and the potential to disrupt thyroid homeostasis. In the GH3 luciferase reporter gene assays, 5 of the pesticides tested had agonistic effects in the order of procymidone > imidacloprid > mancozeb > fluroxypyr > atrazine. 11 pesticides inhibited luciferase activity of T3 to varying degrees, demonstrating their antagonistic activity. And there are 4 pesticides showed mixed effects when treated with different concentrations. Surface plasmon resonance (SPR) biosensor technique was used to directly measure the binding interactions of these pesticides to the human thyroid hormone receptor (hTR). 13 pesticides were observed to bind directly with TR, with a KD ranging from 4.80E-08 M to 9.44E-07 M. The association and disassociation of the hTR/pesticide complex revealed 2 distinctive binding modes between the agonists and antagonists. At the same time, a different binding mode was displayed by the pesticides showed mix agonist and antagonist activity. In addition, the molecular docking simulation analyses indicated that the interaction energy calculated by CDOCKER for the agonists and antagonists correlated well with the KD values measured by the surface plasmon resonance assay. These results help to explain the differences of the TR activities of these tested pesticides.

Toxic effects of triclosan on a zebrafish (Danio rerio) liver cell line, ZFL.

Triclosan (TCS, 5-chloro-2-(2,4-dichlorophenoxy) phenol) is an antimicrobial agent widely used in personal care products. It has been detected in surface water, soil, aquatic species, and even humans. In this study, we used zebrafish (Danio rerio) as a model to test the hypothesis that TCS exhibits toxic effects by interacting with thyroid hormone receptor ß (TRß) and aryl hydrocarbon receptor (AhR) and by inducing the transcription of thyroid hormone (TH)-associated genes and affecting phase I and phase II enzymes. The median lethal concentrations (LC50) of TCS in zebrafish embryos/larvae and a zebrafish liver cell line (ZFL) were first determined. Hatched larvae were most sensitive to TCS exposure, with LC50 values ranging from 1.26 to 1.46µM for 96h after hatching exposure. The major effect of TCS was delayed hatching which occurred from 1.13µM. The constructed GFP-zfTRß fusion protein revealed the subcellular location of zfTRß as the nucleus in both T3-induced and uninduced states, adding to the difficulty of studying TCS action on thyroid hormone receptors in ZFL cells. TCS had neither agonistic nor antagonistic effects on zfTRßLBD or AhR from the reporter gene systems. Ethoxyresorufin-o-deethylase (EROD) assay suggested that TCS is a weak P4501a (Cyp1a) agonist at 5µM and that it inhibits cytochrome Cyp1a activity induced by benzo(a)pyrene (BaP). In time course-based mRNA profiling in ZFL cells, 4-h exposure to TCS caused a significant (up to 37.5-fold) inhibition of Cyp1a at 2.5µM. An overall inhibition of liver phase I and II gene transcription at 4h exposure indicates the possible quick catabolism of TCS. Our findings suggest that TCS is not a TH mimic that affects TH-related gene expression. The impairment of Cyp1a mRNA expression could be due to stimulation by other stressors such as oxidative stress, warranting further investigation into the underlying mechanism in zebrafish.

Cell-Free Protein Synthesis Approach to Biosensing hTRß-Specific Endocrine Disruptors.

Here we introduce a Rapid Adaptable Portable In vitro Detection biosensor platform (RAPID) for detecting ligands that interact with nuclear hormone receptors (NHRs). The RAPID platform can be adapted for field use, allowing rapid evaluation of endocrine disrupting chemicals (EDCs) presence or absence in environmental samples, and can also be applied for drug screening. The biosensor is based on an engineered, allosterically activated fusion protein, which contains the ligand binding domain from a target NHR (human thyroid receptor ß in this work). In vitro expression of this protein using cell-free protein synthesis (CFPS) technology in the presence of an EDC leads to activation of a reporter enzyme, reported through a straightforward colorimetric assay output. In this work, we demonstrate the potential of this biosensor platform to be used in a portable "just-add-sample" format for near real-time detection. We also demonstrate the robust nature of the cell-free protein synthesis component in the presence of a variety of environmental and human samples, including sewage, blood, and urine. The presented RAPID biosensor platform is significantly faster and less labor intensive than commonly available technologies, making it a promising tool for detecting environmental EDC contamination and screening potential NHR-targeted pharmaceuticals.

Loss of tyrosine phosphorylation at Y406 abrogates the tumor suppressor functions of the thyroid hormone receptor ß.

We have recently identified that phosphorylation at tyrosine (Y)406 is critical for the tumor suppressor functions of the thyroid hormone receptor ß1 (TRß) in a breast cancer line. However, still unclear is whether the critical tumor suppressor role of phosphorylated Y406 of TRß is limited to only breast cancer cells or could be extended to other cell types. In the present studies, we addressed this question by stably expressing TRß, a mutated TRß oncogene (PV), or a TRß mutated at Y406 (TRßY406F) in rat PCCL3 thyroid follicular cells and evaluated their tumor characteristics in athymic mice with elevated thyroid stimulating hormone. PCCL3 cells stably expressing PV (PCCL3-PV), TRßY406F (PCCL3-TRßY406F), or vector only (PCCL3-Neo) developed tumors with sizes in the rank order of TRßY406F>PV = Neo, whereas PCCL3 cells expressing TRß (PCCL3-TRß) barely developed tumors. As evidenced by markedly elevated Ki67, cyclin D1, and p-Rb protein abundance, proliferative activity was high in PV and TRßY406F tumors, but low in TRß tumors. These results indicate that TRß acted as a tumor suppressor in PCCL3 cells, whereas TRßY406F and PV had lost tumor suppressor activity. Interestingly, TRßY406F tumors had very low necrotic areas with decreased TNFα-NFκB signaling to lower apoptotic activity. In contrast, PV tumors had prominent large necrotic areas, with no apparent changes in TNFα-NFκB signaling, indicating distinct oncogenic activities of mutant PV and TRßY406F. Thus, the present studies uncovered a novel mechanism by which TRß could function as a tumor suppressor through modulation of the TNFα-NFκB signaling. © 2016 Wiley Periodicals, Inc.

Structure-based approach for the study of thyroid hormone receptor binding affinity and subtype selectivity.

Thyroid hormone (TH) possesses the ability to lower cholesterol and improve cardiac performance, which have prompted the efforts to design analogs that can utilize the cholesterol-lowering property without adversely affecting heart function. In order to gain insights into the interaction mechanism for agonists at the active site of thyroid hormone receptor ß (TRß), quantitative structure-activity relationship (QSAR) models have been developed on TRß agonists, significant statistical coefficients were obtained (CoMFA, R(2)cv, .732), (CoMSIA, R(2)cv, .853), indicating the internal consistency of the models, the obtained models were further validated using the test set, the acquired R(2)pred values .7054 and .7129 were in good agreement with the experimental results. The key amino acids affecting ligand binding were identified by molecular docking, and the detailed binding modes of the compounds with different activities were also determined. Furthermore, molecular dynamics (MD) simulations were conducted to assess the reliability of the derived models and the docking results. Moreover, TH exerts significant physiological effects through modulation of the two human thyroid hormone receptor subtypes. Because TRß and TRα locate in different target cells, selective TR ligands would target specific tissues regulated by one receptor without affecting the other. Thus, the 3D information was analyzed to reveal the most relevant structural features involved in selectivity. The findings serve as the basis for further investigation into selective TRß/TRα agonists.

In silico modelling of prostacyclin and other lipid mediators to nuclear receptors reveal novel thyroid hormone receptor antagonist properties.

Prostacyclin (PGI2) is a key mediator involved in cardiovascular homeostasis, acting predominantly on two receptor types; cell surface IP receptor and cytosolic peroxisome proliferator activated receptor (PPAR) ß/δ. Having a very short half-life, direct methods to determine its long term effects on cells is difficult, and little is known of its interactions with nuclear receptors. Here we used computational chemistry methods to investigate the potential for PGI2, beraprost (IP receptor agonist), and GW0742 (PPARß/δ agonist), to bind to nuclear receptors, confirmed with pharmacological methods. In silico screening predicted that PGI2, beraprost, and GW0742 have the potential to bind to different nuclear receptors, in particular thyroid hormone ß receptor (TRß) and thyroid hormone α receptor (TRα). Docking analysis predicts a binding profile to residues thought to have allosteric control on the TR ligand binding site. Luciferase reporter assays confirmed that beraprost and GW0742 display TRß and TRα antagonistic properties; beraprost IC50 6.3 × 10(-5)mol/L and GW0742 IC50 4.9 × 10(-6) mol/L. Changes to triiodothyronine (T3) induced vasodilation of rat mesenteric arteries measured on the wire myograph were measured in the presence of the TR antagonist MLS000389544 (10(-5) mol/L), beraprost (10(-5) mol/L) and GW0742 (10(-5) mol/L); all significantly inhibited T3 induced vasodilation compared to controls. We have shown that both beraprost and GW0742 exhibit TRß and TRα antagonist behaviour, and suggests that PGI2 has the ability to affect the long term function of cells through binding to and inactivating thyroid hormone receptors.

Automatic identification of mobile and rigid substructures in molecular dynamics simulations and fractional structural fluctuation analysis.

The analysis of structural mobility in molecular dynamics plays a key role in data interpretation, particularly in the simulation of biomolecules. The most common mobility measures computed from simulations are the Root Mean Square Deviation (RMSD) and Root Mean Square Fluctuations (RMSF) of the structures. These are computed after the alignment of atomic coordinates in each trajectory step to a reference structure. This rigid-body alignment is not robust, in the sense that if a small portion of the structure is highly mobile, the RMSD and RMSF increase for all atoms, resulting possibly in poor quantification of the structural fluctuations and, often, to overlooking important fluctuations associated to biological function. The motivation of this work is to provide a robust measure of structural mobility that is practical, and easy to interpret. We propose a Low-Order-Value-Optimization (LOVO) strategy for the robust alignment of the least mobile substructures in a simulation. These substructures are automatically identified by the method. The algorithm consists of the iterative superposition of the fraction of structure displaying the smallest displacements. Therefore, the least mobile substructures are identified, providing a clearer picture of the overall structural fluctuations. Examples are given to illustrate the interpretative advantages of this strategy. The software for performing the alignments was named MDLovoFit and it is available as free-software at: http://leandro.iqm.unicamp.br/mdlovofit.

(-) Arctigenin and (+) pinoresinol are antagonists of the human thyroid hormone receptor ß.

Lignans are important biologically active dietary polyphenolic compounds. Consumption of foods that are rich in lignans is associated with positive health effects. Using modeling tools to probe the ligand-binding pockets of molecular receptors, we found that lignans have high docking affinity for the human thyroid hormone receptor ß. Follow-up experimental results show that lignans (-) arctigenin and (+) pinoresinol are antagonists of the human thyroid hormone receptor ß. The modeled complexes show key plausible interactions between the two ligands and important amino acid residues of the receptor.

Unusual ratio between free thyroxine and free triiodothyronine in a long-lived mole-rat species with bimodal ageing.

Ansell's mole-rats (Fukomys anselli) are subterranean, long-lived rodents, which live in eusocial families, where the maximum lifespan of breeders is twice as long as that of non-breeders. Their metabolic rate is significantly lower than expected based on allometry, and their retinae show a high density of S-cone opsins. Both features may indicate naturally low thyroid hormone levels. In the present study, we sequenced several major components of the thyroid hormone pathways and analyzed free and total thyroxine and triiodothyronine in serum samples of breeding and non-breeding F. anselli to examine whether a) their thyroid hormone system shows any peculiarities on the genetic level, b) these animals have lower hormone levels compared to euthyroid rodents (rats and guinea pigs), and c) reproductive status, lifespan and free hormone levels are correlated. Genetic analyses confirmed that Ansell's mole-rats have a conserved thyroid hormone system as known from other mammalian species. Interspecific comparisons revealed that free thyroxine levels of F. anselli were about ten times lower than of guinea pigs and rats, whereas the free triiodothyronine levels, the main biologically active form, did not differ significantly amongst species. The resulting fT4:fT3 ratio is unusual for a mammal and potentially represents a case of natural hypothyroxinemia. Comparisons with total thyroxine levels suggest that mole-rats seem to possess two distinct mechanisms that work hand in hand to downregulate fT4 levels reliably. We could not find any correlation between free hormone levels and reproductive status, gender or weight. Free thyroxine may slightly increase with age, based on sub-significant evidence. Hence, thyroid hormones do not seem to explain the different ageing rates of breeders and non-breeders. Further research is required to investigate the regulatory mechanisms responsible for the unusual proportion of free thyroxine and free triiodothyronine.

Atom-based 3D-QSAR, molecular docking and molecular dynamics simulation assessment of inhibitors for thyroid hormone receptor α and ß.

The three-dimensional quantitative structure-activity relationship (3D-QSAR) for inhibitors of thyroid hormone receptors (TR) α and (TR) ß was studied. The training set of the TRα model generated a correlation coefficient (R(2)) = 0.9535, with standard deviation (SD) = 0.3016. From the test set of the TRα model, a Q(2) value for the predicted activities (= 0.4303), squared correlation (random selection R(2)-CV = 0.6929), Pearson-R (= 0.7294) and root mean square error (RMSE = 0.6342) were calculated. The P-value for TRα (= 1.411e-96) and TRß (= 2.108e-165) models indicate a high degree of self-reliance. For the TRß model, the training set yielded R(2) = 0.9424 with SD = 0.3719. From the test set of TRß, Q(2) value (= 0.5336), the squared correlation (R(2)-CV = 0.7201), the Pearson-R (= 0.7852) and RMSE for test set predictions (= 0.8630) all strengthen the good predictive competence of the QSAR model derived. Examination of internal as well as external validation supports the rationality and good predictive ability of the best model. Molecular docking explained the conformations of molecules and important amino acid residues at the docking pocket, and a molecular dynamics simulation study further uncovered the binding process and validated the rationality of docking results. The findings not only lead to a better understanding of interactions between these antagonists and thyroid hormone receptors α and ß, but also provide valuable information about the impact of structure on activity that will be very beneficial in the design of novel antagonists with preferred activity.

Nanostructured sensors containing immobilized nuclear receptors for thyroid hormone detection.

Thyroid hormone receptors (TRs) are members of the nuclear receptors (NRs) superfamily, being encoded by two genes: TRa and TRbeta. In this paper, the ligand-binding domain (LBD) of the TRbeta1 isoform was immobilized on the surface of nanostructured electrodes for TR detection. The platforms containing TRbeta1-LBD were applied to the detection of specific ligand agonists, including the natural hormones T3 (triiodothyronine) and T4 (thyroxine), and the synthetic agonists TRIAC (3,5,3'-triiodothyroacetic acid) and GC-1 [3,5-dimethyl-4-(4'-hydroxy-3'-isopropylbenzyl phenoxy) acetic acid]. Detection was performed via impedance spectroscopy. The biosensors were capable of distinguishing between the thyroid hormones T3 and T4, and/or the analogues TRIAC and GC-1 at concentrations as low as 50 nM. The detection and separation of thyroid hormones and analogue ligands by impedance techniques represents an innovative tool in the field of nanomedicine because it allows the design of inexpensive devices for the rapid and real-time detection of distinct ligand/receptor systems.

Analysis of the roles of mutations in thyroid hormone receptor-ß by a bacterial biosensor system.

Mutations in thyroid hormone receptors (TRs) often lead to metabolic and developmental disorders, but patients with these mutations are difficult to treat with existing thyromimetic drugs. In this study, we analyzed six clinically observed mutations in the ligand-binding domain of the human TRß using an engineered bacterial hormone biosensor. Six agonist compounds, including triiodothyronine (T3), thyroxine (T4), 3,5,3'-triiodothyroacetic acid (Triac), GC-1, KB-141, and CO-23, and the antagonist NH-3 were examined for their ability to bind to each of the TRß mutants. The results indicate that some mutations lead to the loss of ability to bind to native ligands, ranging from several fold to several hundred fold, while other mutations completely abolish the ability to bind to any ligand. Notably, the effect of each ligand on each TRß mutant in this bacterial system is highly dependent on both the mutation and the ligand; some ligands were bound well by a wide variety of mutants, while other ligands lost their affinity for all but the WT receptor. This study demonstrates the ability of our bacterial system to differentiate agonist compounds from antagonist compounds and shows that one of the TRß mutations leads to an unexpected increase in antagonist ability relative to other mutations. These results indicate that this bacterial sensor can be used to rapidly determine ligand-binding ability and character for clinically relevant TRß mutants.

Research resource: identification of novel coregulators specific for thyroid hormone receptor-ß2.

Thyroid hormone receptors (TRs) are expressed as a series of interrelated isoforms that perform distinct biological roles. The TRß2 isoform is found predominantly in the hypothalamus, pituitary, retina, and cochlea and displays unique transcriptional properties relative to the other TR isoforms. To more fully understand the isoform-specific biological and molecular properties of TRß2, we have identified a series of previously unrecognized proteins that selectively interact with TRß2 compared with the more widely expressed TRß1. Several of these proteins preferentially enhance the transcriptional activity of TRß2 when coexpressed in cells and are likely to represent novel, isoform-specific coactivators. Additional proteins were also identified in our screen that bind equally to TRß1 and TRß2 and may function as isoform-independent auxiliary proteins for these and/or other nuclear receptors. We propose that a combination of isoform-specific recruitment and tissue-specific expression of these newly identified coregulator candidates serves to customize TR function for different biological purposes in different cell types.

Distinct ligand-dependent and independent modes of thyroid hormone receptor (TR)/PGC-1α interaction.

Thyroid hormone receptor (TR)/peroxisome proliferator activated receptor coactivator (PGC-1α) interactions are required for T(3)-dependent transcriptional responses involved in adaptive thermogenesis and liver. Thus, it is important to define TR/PGC-1α contact modes and to understand their significance in gene expression. Previous studies have shown that TRß1 recruits PGC-1α to target promoters via contacts between the hormone-dependent TRß1 activation function 2 (AF-2) in the C-terminal ligand binding domain (LBD) and a major PGC-1α nuclear receptor (NR) interaction box (consensus LxxLL) at amino acids 142-146. While our studies verify the existence and importance of this interaction, we present evidence that TRß1 also binds PGC-1α in a second ligand and LxxLL motif independent mode and show that this interaction requires the TRß1 N-terminal domain (NTD) and the PGC-1α N-terminal activation domain (AD) at amino acids 1-130. Transfection assays suggest that optimal PGC-1α coactivation requires the TRß1 NTD and that these contacts are needed for utilization of the PGC-1α C-terminal AD, which does not bind TR and is implicated in basal transcription machinery contacts. We propose that TR AF-1/PGC-1α contacts are needed for transition between activities of PGC-1α N-and C-terminal ADs in gene expression. Our findings provide insights into possible roles for TR and NR AF-1 in gene expression.

Molecular characterization of thyroid hormone receptor beta from Schistosoma japonicum and assessment of its potential as a vaccine candidate antigen against schistosomiasis in BALB/c mice.

BACKGROUND: Thyroid hormones (TH) modulate growth, development and differentiation and metabolic processes by interacting with thyroid hormone receptors (THRs). The purpose of this study was to identify a novel thyroid hormone receptor beta encoding gene of Schistosoma japonicum (SjTHRß) and to investigate its potential as a vaccine candidate antigen against schistosomiasis in BALB/c mice. METHODS: The full-length cDNA sequence of SjTHRß, its gene organization, and its transcript levels were characterized, and the phylogenetic relationship between THR, RAR and RXR from other organisms were analysis, the ability of this protein binding to a conserved DNA core motif, and its potential as a vaccine candidate antigen against schistosomiasis in BALB/c mice were evaluated. RESULTS: The SjTHRß cDNA was cloned, verified by 5' and 3' Rapid Amplification of cDNA Ends and shown to be polyadenylated at the 3'end, suggesting the transcript is full-length. SjTHRß is homologous to THRs from other species and has a predicted conservative DNA binding domain and ligand binding domain that normally characterizes these receptors. A comparative quantitative PCR analysis showed that SjTHRß was the highest expressed in 21d worms and the lowest in 7 d and 13 d schistosomula. The cDNA corresponding to DNA binding domain (SjTHRß-DBD) and ligand binding domain (SjTHRß-LBD) were cloned and subsequently expressed in E coli. The expressed proteins were used to immunize mice and generate specific serum against recombinant SjTHRß (rSjTHRß). Western blotting revealed that anti-rSjTHRß-LBD serum recognized two protein bands in extracts from 21 d worm with molecular sizes of approximately 95 kDa and 72 kDa. Electrophoretic mobility shift assay (EMSA) analysis showed that rSjTHRß-DBD could bind to a conserved DNA core motif. Immunization of BALB/c mice with rSjTHRß-LBD could induce partial protective efficacy(27.52% worm reduction and 29.50% liver eggs reduction)against schistosome infection. Enzyme-linked immunosorbent assay showed that mice vaccinated with recombinant SjTHRß-LBD (rSjTHRß-LBD) generated increased levels of specific IgG, IgG1 and IgG2a antibody. Bio-plex analysis demonstrated that rSjTHRß-LBD induced considerably higher levels of T helper 1 cytokines (IL-2, IL-12 and TNF-α) than T helper 2 cytokines (IL-10, IL-4), suggesting that rSjTHRß-LBD vaccination could stimulate mixed Th1/Th2 types with Th1 dominant immune responses. CONCLUSIONS: Our study presented here identified SjTHRß as a new schistosome THR that might play an important role in host-parasite interaction and be a vaccine candidate for schistosomiasis.

A novel p.E311K mutation of thyroid receptor beta gene in resistance to thyroid hormone syndrome, inherited in autosomal recessive trait.

Resistance to thyroid hormone (RTH) syndrome is caused by mutations in THRB gene and is inherited mainly as an autosomal dominant trait with dominant negative effect. Most of up-to-now described RTH cases were heterozygous. We studied a 19-year-old woman presenting severe mental impairment, hyperkinetic behavior, learning disability, hearing loss, tachycardia, goiter, strabismus, nystagmus, and normal stature. The laboratory findings revealed elevated TSH, T3, and T4 serum levels. Her parents were healthy with normal serum level of TSH, fT3, and fT4. Sequence based prediction of a substitution was analyzed by SDM, PolPhen, and SNAP software whereas structural visualizations were performed in UCSF Chimera. We found a novel mutation in THRB gene in position 1216 (G to A transition, codon 311) resulting in novel Glu-311-Lys (p.E311K) substitution, homozygous in proband presenting with severe symptoms of RTH and heterozygous in both of her healthy parents, thus suggesting autosomal recessive mode of inheritance. p.E311K substitution was not found in 50 healthy, unrelated individuals. p.E311K was shown to be deleterious by SDM, PolPhen, and SNAP software. Structural visualizations of mutated protein performed by UCSF Chimera software disclosed a loss of hydrogen bonds between E311, R383, and R429 along with abnormal residue-residue contact between K311 and L377. This is a very rare case of a homozygous mutation in a patient with severe symptoms of RTH and lack of symptoms in both heterozygous parents. Although, computational analyses have provided the evidence that p.E311K substitution may affect THRB function, lack of dominant negative effect typical for THRB mutations could not be explained by structure-based modeling. Further in vitro analysis is required to assess the functional consequences of this substitution.

Ligand-dependent corepressor acts as a novel corepressor of thyroid hormone receptor and represses hepatic lipogenesis in mice.

BACKGROUND & AIMS: Transcriptional co-regulators assist nuclear receptors to control the transcription and maintain the metabolic homeostasis. Ligand-dependent corepressor (LCOR) was reported to function as a transcriptional corepressor in vitro. We found LCOR expression decreased in fatty livers of leptin-deficient (ob/ob) mice, diet-induced obese mice, as well as patients, suggesting LCOR may play a role in lipid homeostasis. We sought to investigate the physiological role of LCOR in vivo and elucidate the underlining molecular mechanisms. METHODS: The effect of LCOR on hepatic lipid accumulation and thyroid hormone receptor (TR) mediated expression of lipogenic genes was studied in vitro and in vivo. RESULTS: Ectopic expression of LCOR via intravenous infection with LCOR adenovirus decreased the hepatic triglyceride level in wild type, ob/ob, and diet-induced obese mice. Interestingly, overexpression of LCOR repressed the thyroid hormone induced expression of lipogenic genes and non-lipogenic genes, and ameliorated hepatic steatosis in obese mice, suggesting that LCOR might regulate lipogenesis as a novel TR corepressor. Furthermore, our study revealed that LCOR could interact with TRß1 in the presence of the ligand, which resulted in competitive binding and reduced recruitment of steroid receptor coactivator-1/3 (SRC-1/3) to the promoter region of TR target genes. CONCLUSIONS: Our data suggest that LCOR is likely to suppress TRß1-mediated hepatic lipogenesis by decreasing binding and recruitment of SRCs to TRß1. Our study reveals the physiological function of hepatic LCOR in lipid metabolism and the mechanism by which LCOR regulates lipogenesis. Hepatic LCOR may be a potential target for treating hepatic steatosis.