Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0272170 (SDS)
 50,377 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have earlier reported production and characterization of monoclonal antibodies (MAbs) to human thyroglobulin (h-tg). In the present study H10 I MAb was evaluated for its immunoreactivity towards different forms of tg and various human thyroid tumours. The specificity of H10 I MAb was validated by the absence of cross reaction with tri-iodothyronine (T3) Thyroxine (T4) and human gamma globulins. Sodium-dodicyl-sulphate polyacrylamide gel electrophoresed (SDS-PAGE) immunoblot of h-tg on the nitrocellulose membrane revealed multiple immunoreactive bands on reaction with polyclonal antibody (PAb) in comparison with total lack of reactivity with H10 I MAb. The absence of immunoreactivity of H10 I MAb was demonstrated with SDS treated, Dithiothreitol (DT) treated and heat denatured tg using dot immunobinding technique. However, the H10 I MAb was able to react with tg treated with unfolding agents such as urea and guanidine hydrochloride. All the treated forms of tg were equally recognized by PAb. The immunoreactivity of the oxidized/reduced tg towards H10 I MAb was markedly reduced (60.0%) as compared to that obtained with native tg. It appears that H10 I MAb is directed towards conformational epitope involving sulphydryl bonds. Immunohistochemically, a comparable immunoreactivity between PAb and MAb was observed with normal thyroid tissues, follicular thyroid tissues, Hurthle cell carcinoma tissues and poorly differentiated thyroid tumor tissues using immunoperoxidase staining. The sections from papillary carcinoma tissue (thyroid as well as metastatic lymph node) exhibited intense immunoreactivity with PAb. Thyroglobulin present on these sections was not recognized by H10 I MAb. Nonetheless, H10 I MAb was able to detect tg in follicular differentiation wherever present. The absence of immunoreactivity of H10 I MAb in papillary carcinoma strongly suggests that this neoplasm produces tg which is antigenically different from the protein present in the normal tissue. The reactivity of H10 I MAb with metastatic lymph node of an unknown primary origin suggests its usefulness in the identification of prevalent metastasis of differentiated thyroid carcinoma other than papillary type.
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PMID:Monoclonal antibodies to human thyroglobulin: evaluation of immunoreactivity. 128 24

We report the first isolation of purified coated vesicles (CVs) from thyroid gland. Bovine thyroid CVs were isolated by differential centrifugation, including a step through sucrose-D2O, using a modification of the method described by Nandi et al. (1) for bovine brain CVs. The CVs were characterized by electron microscopy, sedimentation properties, and SDS-PAGE of the protein components. Thyroglobulin (Tg) was found to be associated with the purified CVs. When the thyroid CVs were exposed to conditions known to remove the protein coat from brain CVs, such as low ionic strength at pH 8.5, most of the Tg dissociated from the vesicles along with the coat proteins. Moreover, the Tg remaining with the uncoated vesicles (UVs) was trypsin sensitive, and therefore judged to be associated with the external surface of the vesicle. Since ligand-receptor complexes are normally located within CVs and not on their outer surface, no evidence was found for Tg-receptor complexes within thyroid CVs. Thyroid slices were incubated in the presence of [35S] methionine with subsequent isolation of labeled CVs in order to study the incorporation of newly-synthesized proteins into these structures. At 0.5 and 2 hours of incubation, the 180K MW subunit of clathrin, as well as other proteins, but not Tg, had become labeled in the purified CVs. Extracellular 19S-[35S] thyroglobulin was isolated from the incubation medium, however, demonstrating release of newly-synthesized Tg (presumably into cut follicles). It is concluded that thyroid CVs do not seem to be involved in the secretion of newly-synthesized Tg from the rough endoplasmic reticulum into the follicular lumen. While a possible role of thyroid CVs in the reabsorption of small quantities Tg by micropinocytosis cannot be completely excluded, the present data do not support a primary role for thyroid CVs in either endocytosis or exocytosis of Tg.
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PMID:Coated vesicles from the thyroid gland: isolation, characterization, and a search for a possible role in thyroglobulin transport. 286 11

Thyroglobulin (Tg)-specific autoantibodies from a patient with Hashimoto's thyroiditis hydrolyzed radiolabeled Tg, shown by production of several smaller sized products on SDS electrophoresis gels. The apparent Km value for Tg was in the nanomolar range, a property typical of an Ab combining site. The Tg antibodies also hydrolyzed tripeptide-methylcoumarinamide (MCA) substrates with lower affinity, displaying a preference for Arg-MCA and Lys-MCA containing conjugates. The hydrolysis of one of these conjugates, Pro-Phe-Arg-MCA, was inhibited competitively by Tg, suggesting a catalytic site located in the Ab combining site. In control experiments, 1) the hydrolytic activities were removed by immunoadsorption with immobilized anti-human IgG; 2) IgG depleted of the Tg-specific Abs by affinity chromatography did not display Tg and Pro-Phe-Arg-MCA hydrolyzing activities; and 3) the peptide-MCA hydrolyzing activity tracked exactly with the 150-kDa IgG peak on a gel filtration column run in denaturing solvent (6 M guanidine chloride).
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PMID:Catalytic activity of anti-thyroglobulin antibodies. 789 15

Thyroglobulin (Tg) is the major secretory product of thyroid epithelial cells and is stored in the lumen of thyroid follicles at high concentrations. Thyroid hormone liberation is assumed to occur separately from this storage compartment within lysosomes. However, for the transfer of Tg to lysosomes, mechanisms to solubilize the luminal content must precede its endocytosis, because part of the luminal Tg occurs in a covalently cross-linked form. Here, by immunoprecipitation and immunoblotting we show that the majority of procathepsin B or L and a fraction of mature cathepsin B are released from porcine thyrocytes in vitro. Released cathepsins were detectable on the cell surface of the thyrocytes by immunocytochemistry and amounted to 27% of the total cathepsin B. Cytochemical studies revealed the proteolytic activity of cathepsin B at neutral pH on the cell surface of thyrocytes. Therefore, the possibility of extracellular proteolysis by cathepsins was investigated by incubating plasma membrane preparations, conditioned media, or lysosomes with Tg. The liberation of thyroid hormones was quantitated by RIA, and the degradation of Tg was determined by SDS-PAGE. Extracellular and plasma membrane-associated proteases rapidly mediated up to 54% of the total T4 liberation by limited proteolysis of Tg at neutral pH under conditions where cysteine proteases were reactivated. We propose that released and proteolytically active cysteine protease i.e. cathepsins B and L, provide thyrocytes with a pathway of limited extracellular proteolysis of Tg before endocytosis.
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PMID:Evidence for extracellularly acting cathepsins mediating thyroid hormone liberation in thyroid epithelial cells. 861 37

Thyroglobulin (TG) is the major soluble protein of the thyroid and is known to be extracellularly stored for future liberation of thyroid hormones. We have developed techniques for the isolation of an insoluble storage form of human TG present in the follicle lumen. The application of these techniques yielded insoluble and translucent colloid globules varying in size (50-500 microns) and shape and consisting primarily of densely packed TG. Intact colloid globules exhibited the imprints of the apical cell surfaces of thyrocytes that had surrounded the colloid globules in situ. Hence, in size and surface morphology, isolated colloid globules represent authentic lumenal content. Based on the total protein of single colloid globules and their volume, an average protein concentration of 590 mg/mL was calculated. The presence of protein disulfide isomerase in colloid globules and in the secretory product of cultured thyrocytes suggests its involvement in the extracellular multimerization of human TG. Native colloid globules increased their volume considerably upon reduction of disulfide bonds; they were completely dissolved by treatment with dithiothreitol and SDS. The results show that part of extracellular human TG undergoes multimerization, primarily by the formation of intermolecular disulfide bonds, thus allowing the storage of TG at excessively high, previously unknown, concentrations.
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PMID:Multimerization of thyroglobulin (TG) during extracellular storage: isolation of highly cross-linked TG from human thyroids. 862 58

Thyroglobulin (Tg), the thyroid hormone precursor, is a major protein component in the thyroid gland and may have other important functions. Here, we show that bovine Tg inhibited 125I-labeled transforming growth factor-beta1 (125I-TGF-beta1) binding to cell-surface TGF-beta receptors in mink lung epithelial cells with an IC50 of approximately 300 nM. After disuccinimidyl suberate (DSS) modification, reduction/alkylation, treatment with 8 M urea, 0. 1% SDS, or acidic pH (pH 4-5), Tg exhibited a approximately 5-10-fold increase of 125I-TGF-beta1 binding inhibitory activity with IC50 of approximately 30-60 nM. This inhibitory activity was an intrinsic property of the Tg and could not be segregated from Tg protein by 5% SDS-polyacrylamide gel electrophoresis or by immunoprecipitation using antiserum to Tg. Untreated Tg did not affect DNA synthesis but blocked the TGF-beta-induced inhibition of DNA synthesis in mink lung epithelial cells. After DSS activation, Tg possessed TGF-beta agonist activity and inhibited DNA synthesis of mink lung epithelial cells and rat thyroid cells. The activated Tg also exerted a small but significant TGF-beta agonist activity in transcriptional activation of plasminogen activator inhibitor-1. These results suggest that Tg possesses an authentic TGF-beta activity which can be induced by chemical modifications and treatments with denaturing agents and acidic pH.
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PMID:Activated thyroglobulin possesses a transforming growth factor-beta activity. 974 82

Thyroglobulin (Tg) was subjected to metal-catalyzed oxidation, and the oxidative degradation was analyzed by SDS-polyacrylamide gel electrophoresis under reducing conditions. In contrast to no effect of hydrogen peroxide (H2O2) alone on the Tg degradation, the inclusion of Cu2+ (30 microM), in combination with 2 mM H2O2, caused a remarkable degradation of Tg, time- and concentration-dependent. The action of Cu2+ was not mimicked by Fe2+, suggesting that Tg may interact selectively with Cu2+. A similar degradation of Tg was also observed with Cu2+/ascorbate system, and the concentration of Cu2+ (5-10 microM), in combination with ascorbate, required for the effective degradation was smaller than that of Cu2+ (10-30 microM) in combination with H2O2. In support of involvement of H2O2 in the Cu2+/ascorbate action, catalase expressed a complete protection. However, hydroxyl radical scavengers such as dimethylsulfoxide or mannitol failed to prevent the oxidation of Tg whereas phenolic compounds, which can interact with Cu2+, diminished the oxidative degradation, presumably consistent with the mechanism for Cu2+-catalyzed oxidation of protein. Moreover, the amount of carbonyl groups in Tg was increased as the concentration (3-100 microM) of Cu2+ was enhanced, while the formation of acid-soluble peptides was not remarkable in the presence of Cu2+ up to 200 microM. In further studies, Tg pretreated with heat or trichloroacetic acid seemed to be somewhat resistant to Cu2+-catalyzed oxidation, implying a possible involvement of protein conformation in the susceptibility to the oxidation. Based on these observations, it is proposed that Tg could be degraded non-enzymatically by Cu2+-catalyzed oxidation.
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PMID:Cu2+-catalyzed oxidative degradation of thyroglobulin. 1102 45