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The ability to concentrate iodide actively is a characteristic feature of the thyroid gland and several other tissues. This function is mediated through the sodium iodide symporter (NIS), a protein that is located in the basolateral membrane of the thyrocyte. A defect in the NIS (iodide trapping defect) can result in hypothyroidism, the severity of which is variable and influenced, in part, by the...
The six patients described in this study were clinically diagnosed with congenital hypothyroidism. Based on clinical and pathophysiological parameters, the cause of the thyroid dyshormonogenesis was suspected to be a defect in the synthesis of thyroglobulin, the matrix protein for thyroid hormone synthesis in the thyroid gland. After RNA isolation from six goitrous tissues and control thyroid tissues,...
The human gene encoding the thyroid transcription factor 2 (TTF-2) was cloned and mapped to human chromosome 9q22. Three polymorphisms were identified in the gene by SSCP and direct sequencing: two consist of a third base substitution in the triplet encoding Leu129 and Ser273, and the third is an alanine stretch that varies from 12 to 17 residues. TTF-2 plays a critical role during thyroid morphogenesis...
Apart from the essential trace element iodine, which is the central constitutent of thyroid hormones, a second essential trace element, selenium, is required for appropriate thyroid hormone synthesis, activation and metabolism. The human thyroid gland has the highest selenium content per gram of tissue among all organs. Several selenocysteine-containing proteins respectively enzymes are functionally...
It has been suggested that selenium deficiency aggravates the iodine-induced thyroid inflammation and necrosis in iodine-deficient Wistar rats and possibly in man. Studies were carried out to determine whether large amounts of iodine given to iodine-deficient pregnant Sprague-Dawley rats with or without selenium deficiency would induce inflammation and necrosis in their term fetal thyroids. Iodine...
In vitro and in vivo models to study the pathogenesis of thyroid autoimmunity are reviewed. Animal models with experimentally induced or spontaneously developed autoimmune thyroid disease as well as transplantation models have been used extensively in these studies, but also the use of thyroid cell cultures from both humans and animals has contributed to the present state of knowledge. Cytokines may...
The ability of asialo-thyroglobulin to bind the thyroid RHL-1 subunit of the asialoglycoprotein receptor has been investigated. Ligand blot assays show that the recombinant carbohydrate recognition domain of the thyroid RHL-1 subunit specifically interacts with rat desialated thyroglobulin. Moreover, RT-PCR and Western blot assays show that TSH deprivation decreases RHL-1 expression in PC Cl3 thyroid...
The comparative analysis of the products of the limited proteolysis of bovine thyroglobulin with trypsin by SDS-polyacrylamide gel electrophoresis in non-reducing and reducing conditions revealed the presence of disulfide linkages between some of the fragments. In order to define the disulfide bond pattern between the proteolytic fragments of thyroglobulin, these were isolated by SDS-polyacrylamide...
Thyroid peroxidase is a member of a family of mammalian peroxidases that includes myeloperoxidase, lactoperoxidase, eosinophil peroxidase, and salivary peroxidase. Protein sequences showing a high degree of sequence similarity with mammalian peroxidases have recently been observed in several invertebrate species. A multiple sequence alignment prepared with five mammalian and six invertebrate peroxidases...
Type 2 deiodinase (D2) is a low K m iodothyronine deiodinase that metabolizes thyroxine (T 4 ) to the active metabolite T 3 . We have recently shown that the cDNA for the human D2 coding region contains two in-frame selenocysteine (TGA) codons. The 3` TGA is seven codons 5` to a universal stop codon, TAA. The human D2 enzyme, transiently expressed in HEK-293 cells, can be in...
We have measured 3,5,3`triiodothyronine (T 3 ) in 12 tissues from thyroidectomized (Tx) rats infused with increasing doses of T 3 , and related them to their corresponding plasma levels. Young adult Wistar rats were surgically Tx. After 4 weeks, the animals were infused with placebo or T 3 (0.25, 0.50, 0.75, 1.00 or 2.00<space>μg/100<space>g body weight/day). Placebo-infused...
Many aspects of thyroid nodule evaluation and management remain controversial. Widespread application of ultrasonography has resulted in frequent discovery of incidental nodules in the general population which has created a management dilemma for physicians. In this paper we have introduced a novel approach for evaluation of solid nodules, using an index derived from ultrasonographic and cytologic...
Iodine and thyroglobulin concentrations, as well as iodine, T 3 , T 4 and sialic acid contents of thyroglobulin, were measured in thyroid glands collected postmortem from 42 human premature or term newborns and infants. Three groups were considered: very preterm newborns (24-32 postmenstrual weeks, < 5 days postnatal life), preterm and term newborns (34-41 postmenstrual weeks, <...
Newly synthesized thyroglobulin transiting the secretory pathway is posttranslationally modified by addition of oligosaccharides to asparagine N-linked residues. The effect of divalent cation depletion on oligosaccharide processing of Tg was studied in FRTL-5 cells. Treatment with an ionophore, A23187, or thapsigargin, an inhibitor of the sarcoplasmic/endoplasmic reticulum ATPases delayed Tg secretion...
Since the beginning of the 1990s, our knowledge of the protein equipment of plant membranes progresses at an accelerating pace, owing to the irruption of molecular biology tools and genetics strategies in plant biology. Map-based cloning strategies and exploration of EST databases rapidly enrich the catalog of cDNA or gene sequences expected to code for membrane proteins. The accumulation of `putative'...
Protein transport along the secretory pathway is supported by a noria of vesicles that bud and fuse, load and unload their cargo from one compartment into the other. However, despite this constant flow-through of proteins and lipids the various compartments of the secretory pathway are able to maintain their own specific composition. Here, we discuss recent insights into mechanisms of protein retention...
Rhizobial lipochitooligosaccharidic Nod factors mediate the specific recognition between leguminous plants and their prokaryotic symbionts. This review summarizes recent findings on the way plants could perceive and transduce these bacterial signals. It starts by summarizing knowledge about Nod factor binding sites, before moving to the potential implications in Nod factor signal transduction of G...
After a brief review of the strategies used to date to identify systematically plasma membrane (PM) proteins, emphasis was given to the proteomic approach of PM proteins from the model plant Arabidopsis thaliana. Comparative analysis of two-dimensional gels from PM and cytosolic fractions was used to assess the cellular origin of proteins found in PM fraction. The classification obtained was confirmed...
Eukaryotic cells are characterised by the organised distribution of membrane bounded compartments in their cytoplasm. The endoplasmic reticulum (ER) and the Golgi apparatus (GA) are part of this endomembrane machinery. They are involved in protein flow, and are in charge of specific functions such as the assembly, sorting and transport of newly synthesised proteins, glycoproteins or polysaccharides...
Self-incompatibility (SI) is a widespread mechanism in angiosperms which prevents self-fertilization. This mechanism relies on cell-cell interactions between pollen and pistil. Among the different SI systems that have been reported, two have been particularly investigated: the gametophytic system of Solanaceae and the sporophytic system of Brassicaceae. In these two families, although the molecular...
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