Posttranscriptional regulation of sodium-iodide symporter mRNA expression in the rat thyroid gland by acute iodide administration

Abstract

Serrano-Nascimento C, Calil-Silveira J, Nunes MT. Posttranscriptional regulation of sodium-iodide symporter mRNA expression in the rat thyroid gland by acute iodide administration. Am J Physiol Cell Physiol 298: C893-C899, 2010. First published January 27, 2010 doi:10.1152/ajpcell.00224.2009Iodide is an important regulator of thyroid activity. Its excess elicits the Wolff-Chaikoff effect, characterized by an acute suppression of thyroid hormone synthesis, which has been ascribed to serum TSH reduction or TGF-␤ increase and production of iodolipids in the thyroid. These alterations take hours/days to occur, contrasting with the promptness of WolffChaikoff effect. We investigated whether acute iodide administration could trigger events that precede those changes, such as reduction of sodium-iodide symporter (NIS) mRNA abundance and adenylation, and if perchlorate treatment could counteract them. Rats subjected or not to methylmercaptoimidazole treatment (0.03%) received NaI (2,000 g/0.5 ml saline) or saline intraperitoneally and were killed 30 min up to 24 h later. Another set of animals was treated with iodide and perchlorate, in equimolar doses. NIS mRNA content was evaluated by Northern blotting and real-time PCR, and NIS mRNA poly(A) tail length by rapid amplification of cDNA ends-poly(A) test (RACE-PAT). We observed that NIS mRNA abundance and poly(A) tail length were significantly reduced in all periods of iodide treatment. Perchlorate reversed these effects, indicating that iodide was the agent that triggered the modifications observed. Since the poly(A) tail length of mRNAs is directly associated with their stability and translation efficiency, we can assume that the rapid decay of NIS mRNA abundance observed was due to a reduction of its stability, a condition in which its translation could be impaired. Our data show for the first time that iodide regulates NIS mRNA expression at posttranscriptional level, providing a new mechanism by which iodide exerts its autoregulatory effect on thyroid.NIS mRNA poly(A) tail; RACE-PAT; perchlorate THERE IS A GROWING body of evidence showing that trace elements, such as iron and selenium, modify the expression of proteins that are involved in their transport and metabolism by posttranscriptionally regulating the expression of the mRNAs that encode them. This posttranscriptional regulation mechanism rapidly changes gene expression patterns and occurs mainly at the transcript polyadenylation level, leading to alterations of the mRNA poly(A) tail length, which has been directly associated to transcript stability and translation efficiency (1-3, 34).Iodine is known to acutely regulate the expression of the sodium-iodide symporter (NIS), a specific protein present in the basement membrane of thyroid cells and that mediates iodide uptake (8). This trace element is essential for thyroid hormone synthesis, although its excess causes a blockade of the thyroid function, which is known as the Wolff-Chaikoff effect (29,49). This effect is rapid and transitory, and the mechanisms ...

Testosterone Induces Vascular Smooth Muscle Cell Migration by NADPH Oxidase and c-Src–Dependent Pathways

“…22,24 Although the Src kinase family acts as a cofactor in the activation of AR in prostatic cells, 26,36 and inhibition of c-Src results in increased dehydroepiandrosterone production by human adrenal tumor cells, there are no data indicating modulation of c-Src by testosterone in VSMCs.…”

“…The analysis of mRNA expression was made by the real-time PCR technique, which was performed as described previ- ously. 26 Briefly, total RNA extracted from VSMCs (TRIzol) were treated with RNase-free DNAse I (Invitrogen Life Technology), and 2 g of RNA were reverse transcribed in a reaction containing oligo-dT (100 g/mL), 10 mmol/L of 2=-deoxynucleoside 5=-triphosphate, 5ϫ First-Strand buffer, and 2 L of 200-U Moloney Murine Leukemia Virus (M-MLV) reverse transcriptase (Invitrogen Life Technology). For real-time PCR amplification, 2 L of each reverse transcription product was diluted in a reaction buffer containing 5 L of SYBR Green PCR master mix (Applied Biosystems) and 900 nmol/L of primers in a final volume of 10 L per sample.…”

Non-classic thyroid hormone signalling involved in hepatic lipid metabolism

“…The involvement of posttranscriptional mechanisms, regulating mRNA stability, seems to justify the rapid effect of T 3 on spot14 mRNA expression, which is not proportional to transcription rate of this gene (Narayan & Towle 1985). This thyroid hormone ability to induce mRNA stability has been described by some authors as a non-classic mechanism involved in rapid changes of mRNA expression (Serrano-Nascimento et al 2010).…”

Hypothyroidism decreases proinsulin gene expression and the attachment of its mRNA and eEF1A protein to the actin cytoskeleton of INS-1E cells

“…Proinsulin mRNA poly(A) tail length was measured by the RACE-PAT according to a standard protocol (25,26). Briefly, 200 ηg of an oligo(dT) anchor (5'-GCGAGCTCCGCGGCC GCG-T 12 ) was added to 2 µg total RNA in a sterile RNasefree microfuge tube.…”