Na+ coordination at the Na2 site of the Na+/I− symporter

The sodium/iodide symporter (NIS) mediates active I− transport in the thyroid—the first step in thyroid hormone biosynthesis—with a 2 Na+: 1 I− stoichiometry. The two Na+ binding sites (Na1 and Na2) and the I− binding site interact allosterically: when Na+ binds to a Na+ site, the affinity of NIS for the other Na+ and for I− increases significantly. In all Na+-dependent transporters with the same fold as NIS, the side chains of two residues, S353 and T354 (NIS numbering), were identified as the Na+ ligands at Na2. To understand the cooperativity between the substrates, we investigated the coordination at the Na2 site. We determined that four other residues—S66, D191, Q194, and Q263—are also involved in Na+ coordination at this site. Experiments in whole cells demonstrated that these four residues participate in transport by NIS: mutations at these positions result in proteins that, although expressed at the plasma membrane, transport little or no I−. These residues are conserved throughout the entire SLC5 family, to which NIS belongs, suggesting that they serve a similar function in the other transporters. Our findings also suggest that the increase in affinity that each site displays when an ion binds to another site may result from changes in the dynamics of the transporter. These mechanistic insights deepen our understanding not only of NIS but also of other transporters, including many that, like NIS, are of great medical relevance.

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The importance of sodium/iodide symporter (NIS) for thyroid cancer management

Arquivos Brasileiros de Endocrinologia & Metabologia ◽

10.1590/s0004-27302007000500004 ◽

2007 ◽

Vol 51 (5) ◽

pp. 672-682 ◽

Cited By ~ 36

Author(s):

Denise P. Carvalho ◽

Andrea C.F. Ferreira

Keyword(s):

Sodium Iodide ◽

Sodium Iodide Symporter ◽

Therapeutic Tool ◽

Iodide Transport ◽

Cancer Management ◽

Thyroid Hormone Biosynthesis ◽

Nis Gene ◽

Hormone Biosynthesis ◽

Tumoral Cells

The thyroid gland has the ability to uptake and concentrate iodide, which is a fundamental step in thyroid hormone biosynthesis. Radioiodine has been used as a diagnostic and therapeutic tool for several years. However, the studies related to the mechanisms of iodide transport were only possible after the cloning of the gene that encodes the sodium/iodide symporter (NIS). The studies about the regulation of NIS expression and the possibility of gene therapy with the aim of transferring NIS gene to cells that normally do not express the symporter have also become possible. In the majority of hypofunctioning thyroid nodules, both benign and malignant, NIS gene expression is maintained, but NIS protein is retained in the intracellular compartment. The expression of NIS in non-thyroid tumoral cells in vivo has been possible through the transfer of NIS gene under the control of tissue-specific promoters. Apart from its therapeutic use, NIS has also been used for the localization of metastases by scintigraphy or PET-scan with 124I. In conclusion, NIS gene cloning led to an important development in the field of thyroid pathophysiology, and has also been fundamental to extend the use of radioiodine for the management of non-thyroid tumors.

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Rapid regulation of thyroid sodium–iodide symporter activity by thyrotrophin and iodine

Journal of Endocrinology ◽

10.1677/joe.1.05643 ◽

2005 ◽

Vol 184 (1) ◽

pp. 69-76 ◽

Cited By ~ 50

Author(s):

Andrea C F Ferreira ◽

Lívia P Lima ◽

Renata L Araújo ◽

Glaucia Müller ◽

Renata P Rocha ◽

...

Keyword(s):

Sodium Iodide ◽

Iodine Content ◽

Concomitant Administration ◽

High Serum ◽

Sodium Iodide Symporter ◽

Physiological Control ◽

Iodide Uptake ◽

Thyroid Hormone Biosynthesis ◽

Serum Tsh

Transport of iodide into thyrocytes, a fundamental step in thyroid hormone biosynthesis, depends on the presence of the sodium–iodide symporter (NIS). The importance of the NIS for diagnosis and treatment of diseases has raised several questions about its physiological control. The goal of this study was to evaluate the influence of thyroid iodine content on NIS regulation by thyrotrophin (TSH) in vivo. We showed that 15-min thyroid radioiodine uptake can be a reliable measurement of NIS activity in vivo. The effect of TSH on the NIS was evaluated in rats treated with 1-methyl-2-mercaptoimidazole (MMI; hypothyroid with high serum TSH concentrations) for 21 days, and after 1 (R1d), 2 (R2d), or 5 (R5d) days of withdrawal of MMI. NIS activity was significantly greater in both MMI and R1d rats. In R2d and R5d groups, thyroid iodide uptake returned to normal values, despite continuing high serum TSH, possibly as a result of the re-establishment of iodine organification after withdrawal of MMI. Excess iodine (0.05% NaI for 6 days) promoted a significant reduction in thyroid radioiodide uptake, an effect that was blocked by concomitant administration of MMI, confirming previous findings that iodine organification is essential for the iodide transport blockade seen during iodine overload. Therefore, our data show that modulation of the thyroid NIS by TSH depends primarily on thyroid iodine content and, further, that the regulation of NIS activity is rapid.

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The Sodium-Iodide Symporter NIS and Pendrin in Iodide Homeostasis of the Thyroid

Endocrinology ◽

10.1210/en.2008-1437 ◽

2009 ◽

Vol 150 (3) ◽

pp. 1084-1090 ◽

Cited By ~ 112

Author(s):

Aigerim Bizhanova ◽

Peter Kopp

Keyword(s):

Autosomal Recessive ◽

Sodium Iodide ◽

Basolateral Membrane ◽

Sensorineural Deafness ◽

Sodium Iodide Symporter ◽

Pendred Syndrome ◽

Iodide Uptake ◽

Anion Transporter ◽

Thyroid Hormone Biosynthesis ◽

Biallelic Mutations

Thyroid hormones are essential for normal development and metabolism. Thyroid hormone biosynthesis requires iodide uptake into the thyrocytes and efflux into the follicular lumen, where it is organified on selected tyrosyls of thyroglobulin. Uptake of iodide into the thyrocytes is mediated by an intrinsic membrane glycoprotein, the sodium-iodide symporter (NIS), which actively cotransports two sodium cations per each iodide anion. NIS-mediated transport of iodide is driven by the electrochemical sodium gradient generated by the Na+/K+-ATPase. NIS is expressed in the thyroid, the salivary glands, gastric mucosa, and the lactating mammary gland. TSH and iodide regulate iodide accumulation by modulating NIS activity via transcriptional and posttranscriptional mechanisms. Biallelic mutations in the NIS gene lead to a congenital iodide transport defect, an autosomal recessive condition characterized by hypothyroidism, goiter, low thyroid iodide uptake, and a low saliva/plasma iodide ratio. Pendrin is an anion transporter that is predominantly expressed in the inner ear, the thyroid, and the kidney. Biallelic mutations in the SLC26A4 gene lead to Pendred syndrome, an autosomal recessive disorder characterized by sensorineural deafness, goiter, and impaired iodide organification. In thyroid follicular cells, pendrin is expressed at the apical membrane. Functional in vitro data and the impaired iodide organification observed in patients with Pendred syndrome support a role of pendrin as an apical iodide transporter. This review shows how the sodium-iodide symporter mediates the active transport of iodide at the basolateral membrane of thyrocytes and discusses biallelic mutations in NIS and the effects of pendrin.

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Compartmentalization of intracellular membrane glycocomponents is revealed by fracture-label.

The Journal of Cell Biology ◽

10.1083/jcb.98.1.29 ◽

1984 ◽

Vol 98 (1) ◽

pp. 29-34 ◽

Cited By ~ 17

Author(s):

M R Torrisi ◽

P Pinto da Silva

Keyword(s):

Endoplasmic Reticulum ◽

Plasma Membrane ◽

Binding Sites ◽

Wheat Germ Agglutinin ◽

Wheat Germ ◽

Secretory Granules ◽

The Other ◽

Rat Tissues ◽

Intracellular Membrane ◽

Definition Of

We used thin-section fracture-label to determine the distribution of wheat-germ agglutinin binding sites in intracellular membranes of secretory and nonsecretory rat tissues as well as in human leukocytes. In all cases, analysis of the distribution of wheat germ agglutinin led to the definition of two endomembrane compartments: one, characterized by absence of the label, includes the membranes of mitochondria and peroxisomes as well as those of the endoplasmic reticulum and nuclear envelope; the other, strongly labeled, comprises the membrane of lysosomes, phagocytic vacuoles, and secretory granules, as well as the plasma membrane. The Golgi apparatus was weakly labeled in all studied tissues.

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Crystal structure of a human plasma membrane phospholipid flippase

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.014144 ◽

2020 ◽

Vol 295 (30) ◽

pp. 10180-10194 ◽

Cited By ~ 8

Author(s):

Hanayo Nakanishi ◽

Katsumasa Irie ◽

Katsumori Segawa ◽

Kazuya Hasegawa ◽

Yoshinori Fujiyoshi ◽

...

Keyword(s):

Plasma Membrane ◽

Human Plasma ◽

Binding Sites ◽

The Other ◽

Asymmetric Distribution ◽

Transmembrane Helices ◽

Outer Leaflet ◽

Extracellular Side ◽

Phospholipid Flippase ◽

Plasma Membrane Phospholipid

ATP11C, a member of the P4-ATPase flippase, translocates phosphatidylserine from the outer to the inner plasma membrane leaflet, and maintains the asymmetric distribution of phosphatidylserine in the living cell. We present the crystal structures of a human plasma membrane flippase, ATP11C–CDC50A complex, in a stabilized E2P conformation. The structure revealed a deep longitudinal crevice along transmembrane helices continuing from the cell surface to the phospholipid occlusion site in the middle of the membrane. We observed that the extension of the crevice on the exoplasmic side is open, and the complex is therefore in an outward-open E2P state, similar to a recently reported cryo-EM structure of yeast flippase Drs2p–Cdc50p complex. We noted extra densities, most likely bound phosphatidylserines, in the crevice and in its extension to the extracellular side. One was close to the phosphatidylserine occlusion site as previously reported for the human ATP8A1–CDC50A complex, and the other in a cavity at the surface of the exoplasmic leaflet of the bilayer. Substitutions in either of the binding sites or along the path between them impaired specific ATPase and transport activities. These results provide evidence that the observed crevice is the conduit along that phosphatidylserine traverses from the outer leaflet to its occlusion site in the membrane and suggest that the exoplasmic cavity is important for phospholipid recognition. They also yield insights into how phosphatidylserine is incorporated from the outer leaflet of the plasma membrane into the transmembrane.

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ESR study of copper(II) retention by entire cell, cells walls, and protoplasts of Saccharomyces cerevisiae

Canadian Journal of Microbiology ◽

10.1139/m87-133 ◽

1987 ◽

Vol 33 (9) ◽

pp. 777-782 ◽

Cited By ~ 4

Author(s):

Jean Claude Kihn ◽

Michèle M. Mestdagh ◽

Paul G. Rouxhet

Keyword(s):

Saccharomyces Cerevisiae ◽

Energy Source ◽

Plasma Membrane ◽

Binding Sites ◽

Cell Walls ◽

Outer Face ◽

Whole Cells ◽

Entire Cell ◽

Acidic Conditions ◽

Isolated Cell

Copper retention by whole cells, protoplasts, and isolated cell walls of Saccharomyces cerevisiae was investigated in the absence of any energy source in the medium. The cell walls accounted only for a small fraction of the cation retention by whole cells. ESR results showed that copper was not bound only at the outer face of the plasma membrane, but it was also distributed in the plasma membrane and (or) in the cytoplasm. ESR studies also showed that, in all three systems, copper was chelated by peptides or proteins. The binding sites were formed by an amide and a strongly complexing ligand such as an amine. Their configuration depended upon pH: in slightly acidic conditions, copper was bound by the oxygen of the amide; at basic pH, NHCO became deprotonated and the negatively charged nitrogen bound to the metal.

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An intramolecular ionic interaction linking defective sodium/iodide symporter transport to the plasma membrane and dyshormonogenic congenital hypothyroidism

Thyroid ◽

10.1089/thy.2021.0344 ◽

2021 ◽

Author(s):

Carlos Eduardo Bernal Barquero ◽

Mariano Martín ◽

Romina Celeste Geysels ◽

Victoria Peyret ◽

Patricia Papendieck ◽

...

Keyword(s):

Plasma Membrane ◽

Congenital Hypothyroidism ◽

Sodium Iodide ◽

Sodium Iodide Symporter ◽

Ionic Interaction

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Iodide excess regulates its own efflux: a possible involvement of pendrin

AJP Cell Physiology ◽

10.1152/ajpcell.00210.2015 ◽

2016 ◽

Vol 310 (7) ◽

pp. C576-C582 ◽

Cited By ~ 12

Author(s):

Jamile Calil-Silveira ◽

Caroline Serrano-Nascimento ◽

Peter Andreas Kopp ◽

Maria Tereza Nunes

Keyword(s):

Plasma Membrane ◽

Thyroid Hormone ◽

Thyroid Hormones ◽

Sodium Iodide ◽

Inhibitory Effect ◽

Membrane Insertion ◽

Sodium Iodide Symporter ◽

Iodide Uptake ◽

Hormone Synthesis ◽

Rat Thyroid

Adequate iodide supply and metabolism are essential for thyroid hormones synthesis. In thyrocytes, iodide uptake is mediated by the sodium-iodide symporter, but several proteins appear to be involved in iodide efflux. Previous studies demonstrated that pendrin is able to mediate apical efflux of iodide in thyrocytes. Acute iodide excess transiently impairs thyroid hormone synthesis, a phenomenon known as the Wolff-Chaikoff effect. Although the escape from this inhibitory effect is not completely understood, it has been related to the inhibition of sodium-iodide symporter-mediated iodide uptake. However, the effects of iodide excess on iodide efflux have not been characterized. Herein, we investigated the consequences of iodide excess on pendrin abundance, subcellular localization, and iodide efflux in rat thyroid PCCl3 cells. Our results indicate that iodide excess increases pendrin abundance and plasma membrane insertion after 24 h of treatment. Moreover, iodide excess increases pendrin half-life. Finally, iodide exposure also increases iodide efflux from PCCl3 cells. In conclusion, these data suggest that pendrin may have an important role in mediating iodide efflux in thyrocytes, especially under conditions of iodide excess.

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Two novel missense mutations in the thyroid peroxidase gene, R665W and G771R, result in a localization defect and cause congenital hypothyroidism

Acta Endocrinologica ◽

10.1530/eje.0.1460491 ◽

2002 ◽

pp. 491-498 ◽

Cited By ~ 31

Author(s):

K Umeki ◽

T Kotani ◽

J Kawano ◽

T Suganuma ◽

I Yamamoto ◽

...

Keyword(s):

Plasma Membrane ◽

Congenital Hypothyroidism ◽

Cellular Localization ◽

Thyroid Peroxidase ◽

Missense Mutations ◽

Thyroid Hormone Biosynthesis ◽

Thyroid Dyshormonogenesis ◽

Hormone Biosynthesis ◽

Iodide Organification Defect ◽

Organification Defect

OBJECTIVE: Thyroid peroxidase (TPO) deficiency is one of the causes of thyroid dyshormonogenesis, because TPO plays a key role in thyroid hormone biosynthesis. To determine the frequency and pattern of TPO abnormalities, we have been screening TPO genes of patients with congenital goitrous hypothyroidism. SUBJECTS AND METHODS: TPO genes of a patient with congenital goitrous hypothyroidism and her parents were directly sequenced, and two novel missense mutations (R665W and G771R) were found. The former was derived from her father and the latter from her mother. R665 and G771 were well conserved in the peroxidase superfamily. When mRNAs containing each of the mutations were transfected into CHO-K1 cells, each cell showed faint TPO enzyme activity. However, immunofluorescence and immunoelectron microscopic analyses revealed that neither of the mutated TPOs reached the plasma membrane. CONCLUSIONS: Two novel missense mutations in the TPO gene were found. TPO proteins encoded by these mutated alleles showed abnormal cellular localization; namely, localization on the plasma membrane was disturbed. The loss of plasma membrane localization in mutated TPOs brought about the iodide organification defect, which was diagnosed as congenital hypothyroidism.

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