Sodium-iodide symporter and its related solute carriers in thyroid cancer

The solute carrier (SLC) family is a large group of membrane transport proteins. Their dysfunction plays an important role in the pathogenesis of thyroid cancer. The most well-known SLC is the sodium-iodide symporter (NIS), also known as sodium/iodide co-transporter or solute carrier family 5 member 5 (SLC5A5) in thyroid cancer. The dysregulation of NIS in thyroid cancer is well documented. The role of NIS in the uptake of iodide is critical in the treatment of thyroid cancer, radioactive iodide (RAI) therapy in particular. In addition to NIS, other SLC members may affect the autophagy, proliferation, and apoptosis of thyroid cancer cells, indicating that an alteration in SLC members may affect different cellular events in the evolution of thyroid cancer. The expression of the SLC members may impact the uptake of chemicals by the thyroid, suggesting that targeting SLC members may be a promising therapeutic strategy in thyroid cancer.

Transcriptome profiling reveals SLC5A5 regulates chicken ovarian follicle granulosa cell proliferation, apoptosis, and steroid hormone synthesis

The egg-laying performance of hens holds significant economic importance within the poultry industry. Broody inheritance of the parent stock of chickens can result in poor options for the improvement of egg production, and is a phenomenon influenced by multiple genetic factors. However, few studies have been conducted to delineate the molecular mechanism of ovarian regression in brooding chickens. Here, we explored the pivotal genes responsible for the regulation of ovarian follicles in laying hens, using RNA-sequencing analysis on the small ovarian follicles from broody and laying chickens. Sequencing data analysis revealed the differential expression of 200 genes, with a predominant enrichment in biological processes related to cell activation and metabolism. Among these genes, we focused on solute carrier family 5 member 5 (SLC5A5), which exhibited markedly higher RNA expression levels in follicles from laying compared with broody chickens. Subsequent cellular function studies with knockdown of SLC5A5 in chicken ovarian follicle granulosa cells (GCs) led to the down-regulation of genes associated with cell proliferation and steroid hormone synthesis, and concurrent promotion of gene expression linked to apoptosis. These findings indicated that SLC5A5 deficiency led to the inhibition of proliferation, steroid hormone synthesis and secretion, and promotion of apoptosis in chicken GCs. Our study demonstrated a pivotal role for SLC5A5 in the development and function of chicken GCs, shedding light on its potential significance in the broader context of chicken ovarian follicle development, and providing a prospective target to improve the egg-laying performance of chickens via molecular marker-assisted breeding technology.

A genetically encoded system for oxygen generation in living cells

Oxygen plays a key role in supporting life on our planet. It is particularly important in higher eukaryotes where it boosts bioenergetics as a thermodynamically favorable terminal electron acceptor and has important roles in cell signaling and development. Many human diseases stem from either insufficient or excessive oxygen. Despite its fundamental importance, we lack methods with which to manipulate the supply of oxygen with high spatiotemporal resolution in cells and in organisms. Here, we introduce a genetic system, SupplemeNtal Oxygen Released from ChLorite (SNORCL), for on-demand local generation of molecular oxygen in living cells, by harnessing prokaryotic chlorite O₂-lyase (Cld) enzymes that convert chlorite (ClO₂^-) into molecular oxygen (O₂) and chloride (Cl^-). We show that active Cld enzymes can be targeted to either the cytosol or mitochondria of human cells, and that coexpressing a chlorite transporter results in molecular oxygen production inside cells in response to externally added chlorite. This first-generation system allows fine temporal and spatial control of oxygen production, with immediate research applications. In the future, we anticipate that technologies based on SNORCL will have additional widespread applications in research, biotechnology, and medicine.

Brief Report: A Novel Sodium/Iodide Symporter Mutation, S356F, Causing Congenital Hypothyroidism

The sodium-iodide symporter (NIS, SLC5A5) is expressed at the basolateral membrane of the thyroid follicular cell, and facilitates the thyroidal iodide uptake required for thyroid hormone biosynthesis. Biallelic loss-of-function mutations in NIS are a rare cause of dyshormonogenic congenital hypothyroidism. Affected individuals typically exhibit a normally sited, often goitrous thyroid gland, with absent uptake of radioiodine in the thyroid and other NIS-expressing tissues. We report a novel homozygous NIS mutation (c.1067 C>T, p.S356F) in four siblings from a consanguineous Indian kindred, presenting with significant hypothyroidism. Functional characterization of the mutant protein demonstrated impaired plasma membrane localization and cellular iodide transport.

Regulation of solute carrier family 26 member 7 (Slc26a7) by thyroid stimulating hormone in thyrocytes

Iodine transportation is an important step in thyroid hormone biosynthesis. Uptake of iodine into the thyroid follicle is mediated mainly by the basolateral sodium-iodide symporter (NIS or solute carrier family 5 member 5: SLC5A5), and iodine efflux across the apical membrane into the follicular lumen is mediated by pendrin (SLC26A4). In addition to these transporters, SLC26A7, which has recently been identified as a causative gene for congenital hypothyroidism, was found to encode a novel apical iodine transporter in the thyroid. Although SLC5A5 and SLC26A4 have been well-characterized, little is known about SLC26A7, including its regulation by TSH, the central hormone regulator of thyroid function. Using rat thyroid FRTL-5 cells, we showed that the mRNA levels of Slc26a7 and Slc26a4, two apical iodine transporters responsible for iodine efflux, were suppressed by TSH, whereas the mRNA level of Slc5a5 was induced. Forskolin and dibutyryl cAMP (dbcAMP) had the same effect as that of TSH on the mRNA levels of these transporters. TSH, forskolin and dbcAMP also had suppressive effects on SLC26A7 promoter activity, as assessed by luciferase reporter gene assays, and protein levels, as determined by Western blot analysis. TSH, forskolin and dbcAMP also induced strong localization of Slc26a7 to the cell membrane according to immunofluorescence staining and confocal laser scanning microscopy. Together, these results suggest that TSH suppresses the expression level of Slc26a7 but induces its accumulation at the cell membrane, where it functions as an iodine transporter.

MiR-181a-5p Regulates NIS Expression in Papillary Thyroid Carcinoma

NIS is a potent iodide transporter encoded by the SLC5A5 gene. Its expression is reduced in papillary thyroid carcinoma (PTC). In this study we analyzed the impact of miR-181a-5p on NIS expression in the context of PTC. We used real-time PCR to analyze the expression of SLC5A5 and miR-181a-5p in 49 PTC/normal tissue pairs. Luciferase assays and mutagenesis were performed to confirm direct binding of miR-181a-5p to the 3′UTR of SLC5A5 and identify the binding site. The impact of modulation of miR-181a-5p using appropriate plasmids on endogenous NIS and radioactive iodine accumulation was verified. We confirmed downregulation of SLC5A5 and concomitant upregulation of miR-181a-5p in PTC. Broadly used algorithms did not predict the binding site of miR-181a-5p in 3′UTR of SLC5A5, but we identified and confirmed the binding site through mutagenesis using luciferase assays. In MCF7 and HEK293-flhNIS cell lines, transfection with mir-181a-expressing plasmid decreased endogenous SLC5A5, whereas silencing of miR-181a-5p increased it. We observed similar tendencies in protein expression and radioactive iodine accumulation. This study shows for the first time that miR-181a-5p directly regulates SLC5A5 expression in the context of PTC and may decrease efficacy of radioiodine treatment. Accordingly, miR-181a-5p may serve as an emerging target to enhance the efficacy of radioactive iodine therapy.

Novel Compound Heterozygous Pathogenic Mutations of SLC5A5 in a Chinese Patient With Congenital Hypothyroidism

BACKGROUND AND OBJECTIVES

Defects in the human sodium/iodide symporter (SLC5A5) gene have been reported to be one of the causes of congenital hypothyroidism (CH). We aimed to identify SLC5A5 mutations in Chinese patients with CH and to evaluate the function of the mutation.

METHODS

Two hundred and seventy-three patients with primary CH were screened for mutations in SLC5A5 using next-generation sequencing. We investigated the expression and cellular localization of the novel compound heterozygous mutation in SLC5A5. The functional activity of the mutants was further examined in vitro.

RESULTS

In 273 patients with CH, two previously undescribed pathogenic mutations p.Gly51AlafsTer45 (G51fs) and p.Gly421Arg (G421R) in a compound heterozygous state in SLC5A5 were identified in a pediatric patient. G51fs was located in the first intercellular loop connecting transmembrane segment I and II, whereas G421R was in the transmembrane segment (TMS) XI. G51fs and G421R resulted in a truncated NIS and reduced protein expression, respectively. In vitro experiments further showed that the normal function of iodine transport of sodium-iodide symporter (NIS) mutants was markedly impaired.

CONCLUSION

The undescribed compound heterozygous mutation of SLC5A5 was discovered in a Chinese CH patient. The mutation led to significantly reduced NIS expression and impaired iodide transport function accompanied by the impaired location of the NIS on the plasma membrane. Our study thus provides further insights into the roles of SLC5A5 in CH pathogenesis.

Improved Noninvasive In Vivo Tracking of AAV-9 Gene Therapy Using the Perchlorate-Resistant Sodium Iodide Symporter from Minke Whale

The sodium iodide symporter (NIS) is widely used as a reporter gene to noninvasively monitor the biodistribution and durability of vector-mediated gene expression via gamma scintigraphy, single-photon emission computed tomography (SPECT), and positron-emission tomography (PET). However, the approach is limited by background signal due to radiotracer uptake by endogenous NIS-expressing tissues. In this study, using the SPECT tracer pertechnetate (^99mTcO₄) and the PET tracer tetrafluoroborate (B¹⁸F₄), in combination with the NIS inhibitor perchlorate, we compared the transport properties of human NIS and minke whale (Balaenoptera acutorostrata scammoni) NIS in vitro and in vivo. Based on its relative resistance to perchlorate, the NIS protein from minke whale appeared to be the superior candidate reporter gene. SPECT and PET imaging studies in nude mice challenged with NIS-encoding adeno-associated virus (AAV)-9 vectors confirmed that minke whale NIS, in contrast to human and endogenous mouse NIS, continues to function as a reliable reporter even when background radiotracer uptake by endogenous NIS is blocked by perchlorate.

Rapid Growth and Early Metastasis of Papillary Thyroid Carcinoma in an Adolescent Girl with Graves' Disease

BACKGROUND

The risk factors for rapid growth and early metastasis of papillary thyroid carcinoma (PTC) and the role of coexisting Graves' disease in the clinical course of PTC remain uncertain in children.

CASE DESCRIPTION

We report on a Japanese girl, whose PTC rapidly grew and metastasized within 4 years. Graves' disease was diagnosed by the presence of serum TSH receptor antibodies at 8 years of age when thyroid ultrasonography detected no nodules. After 4 years of effective treatment with thiamazole, multifocal nodules - up to 47 mm in diameter - were detected on thyroid ultrasonography. Chest CT scan revealed multiple metastatic lesions in the lung. After total thyroidectomy, PTC was pathologically diagnosed. The patient underwent two courses of radioactive iodine (RAI) treatment, but the pulmonary metastatic lesions did not take up the RAI. Molecular analyses of the PTC tissue identified a TFG/NTRK1 chimeric gene and disclosed the preserved expression of TSHR and the reduced expression of SLC5A5 compared with non-tumor thyroid tissue.

CONCLUSIONS

Rapid growth and early metastasis of PTC with coexisting Graves' disease in this patient can be related to a combination of multiple factors including preserved TSHR expression, reduced SLC5A5 expression, and TFG/NTRK1 rearrangement.

Mannose glycosylation is an integral step for NIS localization and function in human breast cancer cells

Chasing an intriguing biological question on the disparity of sodium iodide symporter (NIS, officially known as SLC5A5) expression and function in the clinical scenario of breast cancer, this study addresses key molecular defects involved. NIS in cancer patients has primarily been recorded to be a cytoplasmic protein, thus limiting the scope for targeted radio-iodine therapy. We developed NIS transgene-overexpressing MCF-7 breast cancer cells, and found a few clonal derivatives that show predominant expression of NIS in the plasma membrane. The majority of clones, however, showed cytosolic NIS expression over long passages. Cells expressing membranous NIS show unperturbed dynamic trafficking of NIS through secretory pathway organelles when compared to cells expressing cytoplasmic NIS or to parental cells. Further, treatment of cells expressing membranous NIS with specific glycosylation inhibitors highlighted the importance of inherent glycosylation processing and an 84 gene signature glycosylation RT-Profiler array revealed that clones expressing NIS in their membrane cluster separately compared to the other cells. We further confirm a role of three differentially expressed genes, i.e. MAN1B1, MAN1A1 and MAN2A1, in regulating NIS localization by RNA interference. Thus, this study shows the important role of mannosidase in N-glycosylation processing in order to correctly traffic NIS to the plasma membrane in breast cancer cells.This article has an associated First Person interview with the first author of the paper.

mRNA Expression of SLC5A5 and SLC2A Family Genes in Papillary Thyroid Cancer: An Analysis of The Cancer Genome Atlas

PURPOSE

The present study investigated the dynamics and prognostic role of messenger RNA (mRNA) expression responsible for ¹⁸F-fluorodeoxyglucose (FDG) uptake in FDG positron emission tomography (PET) and radioactive iodine (¹³¹I) uptake in whole-body radioactive iodine scans (WBS) in papillary thyroid cancer (PTC) patients.

MATERIALS AND METHODS

The primary and processed data were downloaded from the Genomic Data Commons Data Portal. Expression data for sodium/iodide symporter (solute carrier family 5 member 5, SLC5A5), hexokinase (HK1-3), glucose-6-phosphate dehydrogenase (G6PD), and glucose transporter (solute carrier family 2, SLC2A1-4) mRNA were collected.

RESULTS

Expression of SLC5A5 mRNA were negatively correlated with SLC2A1 mRNA and positively correlated with SLC2A4 mRNA. In PTC with BRAF mutations, expressions of SLC2A1, SLC2A3, HK2, and HK3 mRNA were higher than those in PTC without BRAF mutations. Expression of SLC5A5, SLC2A4, HK1, and G6PD mRNA was lower in PTC without BRAF mutation. PTCs with higher expression of SLC5A5 mRNA had more favorable disease-free survival, but no association with overall survival.

CONCLUSION

Expression of SLC5A5 mRNA was negatively correlated with SLC2A1 mRNA. This finding provides a molecular basis for the management of PTC with negative WBS using ¹⁸F-FDG PET scans. In addition, higher expression of SLC5A5 mRNA was associated with less PTC recurrence, but not with deaths.

A Novel Missense Mutation in the SLC5A5 Gene in a Sudanese Family with Congenital Hypothyroidism

Thyroid hormone synthesis requires the presence of iodide. The sodium-iodide symporter (NIS) is a glycoprotein that mediates the active uptake of iodide from the blood stream into the thyroid grand. NIS defects due to SLC5A5 gene mutations are known to cause congenital hypothyroidism (CH). The proposita is a 28-year-old female whose origin is North Sudan where neonatal screening for CH is not available. She presented with severe constipation and a goiter at the age of 40 days. Laboratory testing confirmed CH, and she was started on levothyroxine. Presumably due to the delayed treatment, the patient developed mental retardation. Her younger sister presented with a goiter, tongue protrusion, and umbilical hernia, and the youngest brother was also diagnosed with CH based on a thyrotropin level >100 μIU/mL at the age of 22 days and 8 days, respectively. The two siblings were treated with levothyroxine and had normal development. Their consanguineous parents had no history of thyroid disorders. Whole-exome sequencing was performed on the proposita. This identified a novel homozygous missense mutation in the SLC5A5 gene-c.1042T>G, p.Y348D-which was subsequently confirmed by Sanger sequencing. All affected children were homozygous for the same mutation, and their unaffected mother was heterozygous. The NIS protein is composed of 13 transmembrane segments (TMS), an extracellular amino-terminus, and an intracellular carboxy-terminus. The mutation is located in the TMS IX, which has the most β-OH group-containing amino acids (serine and threonine), which is implicated in Na⁺ binding and translocation. In conclusion, a novel homozygous missense mutation in the SLC5A5 gene was identified in this Sudanese family with CH. The mutation is located in the TMS IX of the NIS protein, which is essential for NIS function. Low iodine intake in Sudan is considered to affect the severity of hypothyroidism in patients.

Sex Differences in the Production of SLC5A5, Thyroid Peroxidase, and Thyroid Hormones in Pubertal Rats Exposed to Endocrine Disruptor Dichlorodiphenyltrichloroethane (DDT) during Postnatal Ontogeny

Sex differences in the expression of iodide transporter SLC5A5 and thyroid peroxidase in thyroid follicular epithelium and thyroid serum profile were assessed in pubertal rats exposed to endocrine disruptor DDT starting from the first postnatal day. It was found that exposure to DDT reduced expression of SLC5A5 in peripheral regions of thyroid lobes in males and in central regions in females. The most pronounced sex differences were observed in thyroid peroxidase expression that remained sensitive to thyroid stimulating hormone regulation in males and lost sensitivity to pituitary stimulation in females after exposure to disruptor, which determines more pronounced hypothyroidism in females.

NIS expression in thyroid tumors, relation with prognosis clinicopathological and molecular features

Thyroid cancer therapy is based on surgery followed by radioiodine treatment. The incorporation of radioiodine by cancer cells is mediated by sodium iodide symporter (NIS) (codified by the SLC5A5 gene), that is functional only when targeted to the cell membrane. We aimed to evaluate if NIS expression in thyroid primary tumors would be helpful in predicting tumor behavior, response to therapy and prognosis. NIS expression was addressed by qPCR and immunohistochemistry. In order to validate our data, we also studied SLC5A5 expression on 378 primary papillary thyroid carcinomas from The Cancer Genome Atlas (TCGA) database. In our series, SLC5A5 expression was lower in carcinomas with vascular invasion and with extrathyroidal extension and in those harboring BRAFV600E mutation. Analysis of SLC5A5 expression from TCGA database confirmed our results. Furthermore, it showed that larger tumors, with locoregional recurrences and/or distant metastases or harboring RAS, BRAF and/or TERT promoter (TERTp) mutations presented significantly less SLC5A5 expression. Regarding immunohistochemistry, 12/211 of the cases demonstrated NIS in the membrane of tumor cells, those cases showed variable outcomes concerning therapy success, prognosis and all but one were wild type for BRAF, NRAS and TERTp mutations. SLC5A5 mRNA lower expression is associated with features of aggressiveness and with key genetic alterations involving BRAF, RAS and TERTp. Mutations in these genes seem to decrease protein expression and its targeting to the cell membrane. SLC5A5 mRNA expression is more informative than NIS immunohistochemical expression regarding tumor aggressiveness and prognostic features.

The sodium/iodide symporter: state of the art of its molecular characterization

The sodium/iodide symporter (NIS or SLC5A5) is an intrinsic membrane protein implicated in iodide uptake into thyroid follicular cells. It plays a crucial role in iodine metabolism and thyroid regulation and its function is widely exploited in the diagnosis and treatment of benign and malignant thyroid diseases. A great effort is currently being made to develop a NIS-based gene therapy also allowing the radiotreatment of nonthyroidal tumors. NIS is also expressed in other tissues, such as salivary gland, stomach and mammary gland during lactation, where its physiological role remains unclear. The molecular identity of the thyroid iodide transporter was elucidated approximately fifteen years ago. It belongs to the superfamily of sodium/solute symporters, SSS (and to the human transporter family, SLC5), and is composed of 13 transmembrane helices and 643 amino acid residues in humans. Knowledge concerning NIS structure/function relationship has been obtained by taking advantage of the high resolution structure of one member of the SSS family, the Vibrio parahaemolyticus sodium/galactose symporter (vSGLT), and from studies of gene mutations leading to congenital iodine transport defects (ITD). This review will summarize current knowledge regarding the molecular characterization of NIS.