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Schlumberger
Expression of the apical iodide transporter in human thyroid tissues: a comparison study with other iodide transporters.
Lacroix L, Pourcher T, Magnon C, Bellon N, Talbot M, Intaraphairot T, Caillou B, Schlumberger M, Bidart JM.
J Clin Endocrinol Metab. 2004 Mar;89(3):1423-8.
"Iodide transport by thyrocytes involves two transporters, namely the Na(+)/I (-) symporter located at the basolateral pole and possibly pendrin in the apical membranes of the cell. Recently, we identified a human gene and its protein product, designated hAIT, as a putative new transporter involved in iodide transfer across the apical membrane of thyrocytes. In the present report, we analyzed both hAIT gene and protein expressions in a large series of benign and malignant human thyroid tissues. Using immunohistochemistry, hAIT staining was detected in normal thyroid tissue in about 10% of follicles; in positive follicles, 10-40% of thyrocytes, mostly the tall cells, were stained. In thyroid tissues obtained from patients with Graves' disease and toxic adenomas, hAIT mRNA and protein levels were similar to those found in normal tissue. In hypofunctioning adenomas, hAIT mRNA levels were slightly decreased, and apical iodide transporter (AIT) immunostaining was similar to that observed in normal thyroid tissue. AIT staining was stronger in Hurthle cell adenomas and in microfollicular adenomas. In thyroid carcinomas, the mean and median hAIT mRNA levels were significantly decreased. Expression of AIT protein was undetectable in most papillary carcinomas and was weak but detectable in most follicular carcinomas; it was negative in anaplastic carcinomas."
Identification and characterization of a putative human iodide transporter located at the apical membrane of thyrocytes.
Rodriguez AM, Perron B, Lacroix L, Caillou B, Leblanc G, Schlumberger M, Bidart JM, Pourcher T.
J Clin Endocrinol Metab. 2002 Jul;87(7):3500-3.
"Iodide transport by
thyrocytes is a two step process involving transporters located either
in the basal or in the apical membranes of the cell. The sodium iodide
symporter (NIS) is localized in the basolateral membrane facing the
bloodstream and mediates iodide accumulation into thyrocytes. Pendrin
has been proposed as an apical transporter. In order to identify new
iodide transporters, we developed a PCR cloning strategy based on NIS
sequence homologies. From a human kidney cDNA library, we
characterized a gene, located on chromosome 12q23, that encodes a 610
amino acid protein sharing 46% identity (70% similarity) with the
human NIS. Functional analysis of the protein expressed in mammalian
cells indicates that it catalyzes a passive iodide transport. The
protein product was immunohistochemically localized at the apical pole
of the thyroid cells facing the colloid lumen. These results suggest
that this new identified protein mediates iodide transport from the
thyrocyte into the colloid lumen through the apical membrane. It was
designated hAIT for human Apical Iodide Transporter."