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Acta Crystallographica. Section D,... Nov 2021Thyroglobulin is a homodimeric glycoprotein that is essential for the generation of thyroid hormones in vertebrates. Upon secretion into the lumen of follicles in the...
Thyroglobulin is a homodimeric glycoprotein that is essential for the generation of thyroid hormones in vertebrates. Upon secretion into the lumen of follicles in the thyroid gland, tyrosine residues within the protein become iodinated to produce monoiodotyrosine (MIT) and diiodotyrosine (DIT). A subset of evolutionarily conserved pairs of DIT (and MIT) residues can then engage in oxidative coupling reactions that yield either thyroxine (T; produced from coupling of a DIT `acceptor' with a DIT `donor') or triiodothyronine (T; produced from coupling of a DIT acceptor with an MIT donor). Although multiple iodotyrosine residues have been identified as potential donors and acceptors, the specificity and structural context of the pairings (i.e. which donor is paired with which acceptor) have remained unclear. Here, single-particle cryogenic electron microscopy (cryoEM) was used to generate a high-resolution reconstruction of bovine thyroglobulin (2.3 Å resolution in the core region and 2.6 Å overall), allowing the structural characterization of two post-reaction acceptor-donor pairs as well as tyrosine residues modified as MIT and DIT. A substantial spatial separation between donor Tyr149 and acceptor Tyr24 was observed, suggesting that for thyroxine synthesis significant peptide motion is required for coupling at the evolutionarily conserved thyroglobulin amino-terminus.
Topics: Animals; Cattle; Cryoelectron Microscopy; Halogenation; Protein Conformation; Protein Domains; Protein Multimerization; Thyroglobulin
PubMed: 34726172
DOI: 10.1107/S2059798321010056 -
Thyroid : Official Journal of the... Jun 2023Iodine is required for the synthesis of thyroid hormone (TH), but its natural availability is limited. Dehalogenase1 (Dehal1) recycles iodine from mono- and...
Iodine is required for the synthesis of thyroid hormone (TH), but its natural availability is limited. Dehalogenase1 (Dehal1) recycles iodine from mono- and diiodotyrosines (MIT, DIT) to sustain TH synthesis when iodine supplies are scarce, but its role in the dynamics of storage and conservation of iodine is unknown. -knockout (KO) mice were generated by gene trapping. The timing of expression and distribution was investigated by X-Gal staining and immunofluorescence using recombinant Dehal1-beta-galactosidase protein produced in fetuses and adult mice. Adult KO and wild-type () animals were fed normal and iodine-deficient diets for 1 month, and plasma, urine, and tissues were isolated for analyses. TH status was monitored, including thyroxine, triiodothyronine, MIT, DIT, and urinary iodine concentration (UIC) using a novel liquid chromatography with tandem mass spectrometry method and the Sandell-Kolthoff (S-K) technique throughout the experimental period. Dehal1 is highly expressed in the thyroid and is also present in the kidneys, liver, and, unexpectedly, the choroid plexus. transcription of was induced by iodine deficiency only in the thyroid tissue. Under normal iodine intake, KO mice were euthyroid, but they showed negative iodine balance due to a continuous loss of iodotyrosines in the urine. Counterintuitively, the UIC of KO mice is twofold higher than that of mice, indicating that S-K measures both inorganic and organic iodine. Under iodine restriction, KO mice rapidly develop profound hypothyroidism, while mice remain euthyroid, suggesting reduced retention of iodine in the thyroids of KO mice. Urinary and plasma iodotyrosines were continually elevated throughout the life cycles of KO mice, including the neonatal period, when pups were still euthyroid. Plasma and urine iodotyrosine elevation occurs in Dehal1-deficient mice throughout life. Therefore, measurement of iodotyrosines predicts an eventual iodine shortage and development of hypothyroidism in the preclinical phase. The prompt establishment of hypothyroidism upon the start of iodine restriction suggests that KO mice have low iodine reserves in their thyroid glands, pointing to defective capacity for iodine storage.
Topics: Mice; Animals; Monoiodotyrosine; Mice, Knockout; Iodide Peroxidase; Hypothyroidism; Biomarkers; Thyroxine; Iodine
PubMed: 36879468
DOI: 10.1089/thy.2022.0537 -
Acta Naturae 2021Early (preclinical) diagnosis of Parkinson's disease (PD) is a major challenge in modern neuroscience. The objective of this study was to experimentally evaluate a...
Early (preclinical) diagnosis of Parkinson's disease (PD) is a major challenge in modern neuroscience. The objective of this study was to experimentally evaluate a diagnostic challenge test with monoiodotyrosine (MIT), an endogenous inhibitor of tyrosine hydroxylase. Striatal dopamine was shown to decrease by 34% 2 h after subcutaneous injection of 100 mg/kg MIT to intact mice, with the effect not being amplified by a further increase in the MIT dose. The selected MIT dose caused motor impairment in a neurotoxic mouse model of preclinical PD, but not in the controls. This was because MIT reduced striatal dopamine to the threshold of motor symptoms manifestation only in PD mice. Therefore, using the experimental mouse model of preclinical PD, we have shown that a MIT challenge test may be used to detect latent nigrostriatal dysfunction.
PubMed: 34707902
DOI: 10.32607/actanaturae.11399 -
Hematology, Transfusion and Cell Therapy 2021Although the efficacy of hydroxyurea (HU) in inhibiting erythrocyte sickling has been well demonstrated, the action of this drug on human neutrophils and the mechanism...
INTRODUCTION
Although the efficacy of hydroxyurea (HU) in inhibiting erythrocyte sickling has been well demonstrated, the action of this drug on human neutrophils and the mechanism by which it improves the manifestations of the disease have not been studied thoroughly. We aimed to investigate the cell viability, along with inflammatory and oxidative markers in the neutrophils of sickle cell anemia (SCA) patients and the effects of HU therapy on these cells, by evaluating the dose-responsiveness.
METHODS
In the present study, 101 patients (45 men and 56 women, aged 18-69 years) with SCA were divided into groups according to the use or not of HU: the SS group (without HU treatment, n = 47) and the SSHU group (under HU treatment, n = 54). The SSHU group was further stratified into subgroups according to the daily dose of the drug that patients already used: SSHU - 0.5 g (n = 19); SSHU - 1 g (n = 26) and SSHU - 1.5-2 g (n = 9). A control group (AA) comprised 50 healthy individuals. Neutrophils isolated from whole blood were analyzed using Trypan Blue, monoiodotyrosine (MTT) and lactate dehydrogenase (LDH) toxicity assays. Myeloperoxidase (MPO), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities and concentrations of interleukin 10 (IL-10), tumor necrosis factor alpha (TNF-α) and malonaldehyde (MDA) were also measured.
RESULTS
Neutrophils from SCA patients showed membrane fragility and a significant decrease in cell viability when analyzed by Trypan Blue (p < 0.05), MTT (p < 0.001) and LDH (p = 0.011), compared to the AA group. Levels of inflammatory (MPO, TNF-α, and IL-10) and oxidative markers (SOD, GSH-Px, and MDA) were also altered (p < 0.05) in these cells, showing a significant difference in the SSHU-1g and SSHU - 1.5-2 g groups, compared to the SS group. Treatment with HU reverted the levels of all markers to concentrations similar to those in healthy individuals in a positive dose-effect relationship.
CONCLUSION
The HU did not generate a cytotoxic effect on neutrophils in SCA patients, but it modulated their oxidative and inflammatory mechanisms, promoting cytoprotection with a positive dose-effect.
PubMed: 33051133
DOI: 10.1016/j.htct.2020.07.011 -
Genes & Development Jan 2020In animals, the brain regulates feeding behavior in response to local energy demands of peripheral tissues, which secrete orexigenic and anorexigenic hormones. Although...
In animals, the brain regulates feeding behavior in response to local energy demands of peripheral tissues, which secrete orexigenic and anorexigenic hormones. Although skeletal muscle is a key peripheral tissue, it remains unknown whether muscle-secreted hormones regulate feeding. In , we found that (), the homolog of human bone morphogenetic proteins BMP2 and BMP4, is a muscle-secreted factor (a myokine) that is induced by nutrient sensing and that circulates and signals to the brain. Muscle-restricted dpp RNAi promotes foraging and feeding initiation, whereas overexpression reduces it. This regulation of feeding by muscle-derived Dpp stems from modulation of brain () expression and dopamine biosynthesis. Consistently, Dpp receptor signaling in dopaminergic neurons regulates expression and feeding initiation via the downstream transcriptional repressor Schnurri. Moreover, pharmacologic modulation of TH activity rescues the changes in feeding initiation due to modulation of expression in muscle. These findings indicate that muscle-to-brain endocrine signaling mediated by the myokine Dpp regulates feeding behavior.
Topics: Animals; Brain; DNA-Binding Proteins; Dopamine Agents; Dopaminergic Neurons; Drosophila; Drosophila Proteins; Enzyme Activation; Enzyme Inhibitors; Feeding Behavior; Levodopa; Monoiodotyrosine; Signal Transduction; Transcription Factors; Tyrosine 3-Monooxygenase; Up-Regulation
PubMed: 31831628
DOI: 10.1101/gad.329110.119 -
Frontiers in Bioscience (Landmark... Jan 2019A phylogenetically conserved 5-residue thyroid hormone (TH)- binding motif was originally found in a few TH plasma carriers and, more recently, in all known plasma and...
A phylogenetically conserved 5-residue thyroid hormone (TH)- binding motif was originally found in a few TH plasma carriers and, more recently, in all known plasma and cell-associated proteins interacting with TH as well as in proteins involved in iodide uptake. Minor variations of the motif were found, depending on the particular class of those proteins. Since thyroglobulin (Tg) is the protein matrix for TH synthesis starting from iodination of a selected number of tyrosines (to form first monoiodotyrosine (MIT) and diiodotyrosine (DIT) and then T3 and T4), we hypothesized that by searching the presence of perfect or imperfect versions of that motif in two Tg species (human and murine) in which the iodinated tyrosines and pattern of iodotyrosine/iodothyronine formation are known, we could have found relevant explanations. Explanations, which are not furnished by the simple possession of tyrosine-iodination motifs and sequence of the iodination motif, concern why only some (but not other) tyrosine residues in one species are iodinated and why they have a particular iodination pattern. In this bioinformatics study, we provide such explanations.
Topics: Amino Acid Motifs; Amino Acid Sequence; Animals; Binding Sites; Computational Biology; Diiodotyrosine; Humans; Iodine; Mice; Monoiodotyrosine; Protein Binding; Thyroglobulin; Thyroid Hormones; Thyronines
PubMed: 30468652
DOI: 10.2741/4714 -
Thyroid : Official Journal of the... Feb 2023Congenital hypothyroidism due to defects in iodotyrosine deiodinase has variable phenotypes and can present as hypothyroid or with normal thyroid testing. Whole exome...
Congenital hypothyroidism due to defects in iodotyrosine deiodinase has variable phenotypes and can present as hypothyroid or with normal thyroid testing. Whole exome sequencing was performed in individuals from two families originating from different regions of Sudan. Mass spectrometry of urine and serum iodotyrosines was performed on subjects from both families. A novel iodotyrosine deiodinase (IYD) mutation (c.835C>T; R279C) was identified in individuals from two Sudanese families inherited as autosomal recessive. The mutation was identified by multiple in silica analyses to likely be detrimental. Serum and urine monoiodotyrosine (MIT) and diiodotyrosine (DIT) were markedly elevated in the homozygous subjects. Measurement of serum and urine DIT and MIT was more sensitive than that of urine iodine or serum thyroid function tests to determine the effect of the IYD mutation.
Topics: Humans; Congenital Hypothyroidism; Diiodotyrosine; Iodide Peroxidase; Monoiodotyrosine; Mutation
PubMed: 36633921
DOI: 10.1089/thy.2022.0492 -
Biology Open Jun 2021Across the animal kingdom, dopamine plays a crucial role in conferring reinforcement signals that teach animals about the causal structure of the world. In the fruit fly...
Across the animal kingdom, dopamine plays a crucial role in conferring reinforcement signals that teach animals about the causal structure of the world. In the fruit fly Drosophila melanogaster, dopaminergic reinforcement has largely been studied using genetics, whereas pharmacological approaches have received less attention. Here, we apply the dopamine-synthesis inhibitor 3-Iodo-L-tyrosine (3IY), which causes acute systemic inhibition of dopamine signaling, and investigate its effects on Pavlovian conditioning. We find that 3IY feeding impairs sugar-reward learning in larvae while leaving task-relevant behavioral faculties intact, and that additional feeding of a precursor of dopamine (L-3,4-dihydroxyphenylalanine, L-DOPA), rescues this impairment. Concerning a different developmental stage and for the aversive valence domain. Moreover, we demonstrate that punishment learning by activating the dopaminergic neuron PPL1-γ1pedc in adult flies is also impaired by 3IY feeding, and can likewise be rescued by L-DOPA. Our findings exemplify the advantages of using a pharmacological approach in combination with the genetic techniques available in D. melanogaster to manipulate neuronal and behavioral function.
Topics: Animals; Behavior, Animal; Biosynthetic Pathways; Dopamine; Dopaminergic Neurons; Drosophila melanogaster; Larva; Learning; Monoiodotyrosine
PubMed: 34106227
DOI: 10.1242/bio.058198 -
Topics in Companion Animal Medicine Jun 2021Dietary exogenous thyrotoxicosis is infrequently observed in pet food. A retrospective evaluation of pet food investigations (PFI) was conducted for 17 dogs, including...
Dietary exogenous thyrotoxicosis is infrequently observed in pet food. A retrospective evaluation of pet food investigations (PFI) was conducted for 17 dogs, including review of medical records, dietary and environmental exposure interviews, food testing, and regulatory action. Five PFIs occurring between 2016 and 2018 involved 7 food products including 2 food types, jerky treats or canned food, made from beef or bison. The dogs' serum thyroid hormone concentrations were evaluated before and after diet change. The foods were tested for active thyroid hormones and hormone precursors using high performance liquid chromatography with inductively coupled plasma mass spectrometry detection. The foods were also examined microscopically. Serum thyroid hormone concentrations of thyroxine (T4) varied depending on the food type consumed. Dogs that consumed dried jerky containing greater T4 concentrations often had increased serum T4 concentrations, whereas dogs that consumed canned products containing greater and 3,4,5- and 3,5,3'-triiodothyronine (T3) concentrations often had decreased serum T4 concentrations. After the diets were changed, serum T4 and T3 concentrations normalized at 1 month. Seven foods containing beef or bison had iodine concentrations greater than 11 mg/kg, and iodine speciation identified variable concentrations of iodide, T4, T3, monoiodotyrosine (MIT), and di-iodotyrosine (DIT). Thyroid gland was found in microscopic sections from one finished food and one ingredient, gullet. FDA performed Health Hazard Evaluations to categorize the exposure risk, and 5 foods were recalled for which the product packaging had not been discarded. Dietary exogenous thyrotoxicosis should be considered in dogs exhibiting clinical signs compatible with hyperthyroidism, especially if consuming beef-based food. A thyroid panel that includes serum iodine, coupled with a thorough feeding history can aid in diagnosis. Thyrotoxicosis is typically reversible after removing the contaminated food from the diet.
Topics: Animal Feed; Animals; Diet; Dog Diseases; Dogs; Retrospective Studies; Thyrotoxicosis; Thyroxine; Triiodothyronine
PubMed: 33556641
DOI: 10.1016/j.tcam.2021.100521