Identification of thyroglobulin domain(s) involved in cell-surface binding and endocytosis

Siffroi-Fernandez, Sandrine; Delom, Frédéric; Nlend, MC; Lanet, Jeanne; Franc, JL; Giraud, Annie

doi:10.1677/joe.0.1700217

Cited by 5 publications

(4 citation statements)

References 33 publications

(45 reference statements)

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“…However, it was further demonstrated that this megalin-mediated process resulted in transcytosis of Tg without proteolytic cleavage [29], as observed for antigen processing in the lysosomal compartment. Moreover, a human Tg peptide which is part of the P40 was recently found to bind and enter porcine thyrocytes [30], as described in the present study for the P40 and human thyrocytes.…”

Section: Discussionsupporting

confidence: 72%

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Hydrogen peroxide-induced production of a 40 kDa immunoreactive thyroglobulin fragment in human thyroid cells: the onset of thyroid autoimmunity?

Duthoit

Estienne

Giraud

et al. 2001

Biochemical Journal

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We recently reported that, during in vitro thyroid-hormone synthesis, H2O2 stress cleaved thyroglobulin (Tg) into C-terminal peptides. These peptides were found to contain the immunodominant region of Tg recognized by Tg autoantibodies from patients with an autoimmune thyroid disease. To test the hypothesis that Tg fragmentation is an early upstream initiating event involved in Tg autoimmune response and the consequence of oxidative injuries, we studied the effect of H2O2 stress on human thyroid cells. In culture conditions allowing Tg synthesis and iodine organification by the cells, we found that bolus addition of increasing millimolar doses of H2O2 induced a dose–response appearance of floating cells in the culture medium. These cells apparently resulted from a necrotic process, and they bore iodinated Tg fragments. These fragments were found to be similar to those previously obtained in vitro from purified Tg. In both cases, Tg peptides were recognized by a well-defined monoclonal antibody directed to the immunodominant region of Tg. The smallest immunoreactive Tg peptide had a molecular mass of 40kDa and entered human thyrocytes more efficiently than the entire Tg. These data suggest that thyrocytes exposed to locally increased H2O2 doses accumulate fragmented Tg for further delivery into surrounding living thyrocytes in the course of an autoimmune response.

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Section: Discussionsupporting

confidence: 72%

“…Albeit not yet defined, it was suggested that this shorter peptide bound and internalized the thyrocytes via a Tg cell-surface component different from megalin, but which occurred widely on various cell-types [30].…”

Section: Discussionmentioning

confidence: 99%

Hydrogen peroxide-induced production of a 40 kDa immunoreactive thyroglobulin fragment in human thyroid cells: the onset of thyroid autoimmunity?

Duthoit

Estienne

Giraud

et al. 2001

Biochemical Journal

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“…Further studies are needed to investigate whether and how the difference in the sequence of human Tg and its different heparin-binding capacity affect its binding to HSPGs. Recently, SiffroiFernandez et al (30) provided evidence that the human Tg carboxyl terminal region from Ser2445 to Met2596, comprising the sequence we studied here (Arg2489-Glu2503), is involved in low affinity Tg binding to as yet unidentified molecules on thyroid cell membranes. Based on the results presented here it is worth considering the possibility that binding may be due to HSPGs.…”

Section: Figurementioning

confidence: 83%

Binding of heparin to human thyroglobulin (Tg) involves multiple binding sites including a region corresponding to a binding site of rat Tg

Lisi

Pinchera

McCluskey

et al. 2002

European Journal of Endocrinology

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Objective: Binding of thyroglobulin (Tg) to heparin allows efficient Tg interaction with its endocytic receptor, megalin. Rat Tg (rTg) binds to heparin using an exposed carboxyl terminal region (RELPSRRLKRPLPVK, Arg2489-Lys2503) rich in positively charged residues which is, however, not entirely conserved in human Tg (hTg) (Arg2489-Glu2503, REPPARALKRSLWVE). Here, we investigated whether and how this difference affects binding of heparin. Design: To compare binding of heparin to rTg and hTg. To investigate the role of the sequence 2489-2503 using a peptide-based approach. Methods: Binding of biotin-labeled heparin to rTg, hTg and to Tg peptides was measured in solid phase assays. Results: Heparin bound to rTg with moderately high affinity (K d : 34.2 nmol/l, K i : 37.6 nmol/l) and to hTg with lower affinity (K d : 118 nmol/l, K i : 480 nmol/l) and to a lower extent. Binding was dosedependent and saturable, and was reduced by several specific competitors (Tg itself, unlabeled heparin, lactoferrin). Heparin bound to synthetic peptides corresponding to the rat (rTgP) and to the human (hTgP) Tg sequence 2489 -2503. Heparin bound to rTgP to a greater extent and with greater affinity than to hTgP. An antibody against hTgP reduced binding of heparin to intact hTg by 30%, suggesting that in hTg this region is, in part, involved in heparin binding, but also that other regions account for most of the binding. Starting from the sequence of rTgP, we designed 6 synthetic 'mutant' peptides by replacing one amino acid residue of rTgP with the corresponding residue of the sequence of hTgP. Heparin bound to 5 of 6 mutant peptides to a lower extent and with lower affinity than to rTgP. Conclusions: In spite of a reduced binding ability of the sequence 2489-2503, hTg binds to heparin, in part, using alternative, as yet unidentified, binding sites. Substitution of both positive and neutral residues within the sequence 2489 -2503 reduced heparin-binding, suggesting that not only charge, but also sequence and/or conformation, may account for the heparin-binding ability of this region of Tg.

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“…A commonly used approach to assess the molecular mechanisms of proteins is to establish their functional domains [32,33]. Phylogenetic sequence analysis is a conservation-based method to identify functional domains and related proteins [34,35].…”

Section: Introductionmentioning

confidence: 99%

APRIN is a unique Pds5 paralog with features of a chromatin regulator in hormonal differentiation

Maffini

Denes

Sonnenschein

et al. 2008

The Journal of Steroid Biochemistry and Molecular Biology

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Activation of steroid receptors results in global changes of gene expression patterns. Recent studies showed that steroid receptors control only a portion of their target genes directly, by promoter binding. The majority of the changes are indirect, through chromatin rearrangements. The mediators that relay the hormonal signals to large-scale chromatin changes are, however, unknown. We report here that APRIN, a novel hormone-induced nuclear phosphoprotein has the characteristics of a chromatin regulator and may link endocrine pathways to chromatin. We showed earlier that APRIN is involved in the hormonal regulation of proliferative arrest in cancer cells. To investigate its function we cloned and characterized APRIN orthologs and performed homology and expression studies. APRIN is a paralog of the cohesin-associated Pds5 gene lineage and arose by gene-duplication in early vertebrates. The conservation and domain differences we found suggest, however, that APRIN acquired novel chromatin-related functions (e.g. the HMGlike domains in APRIN, the hallmarks of chromatin regulators, are absent in Pds5). We show that in interphase nuclei APRIN localizes in the euchromatin/heterochromatin interface and we also identified its DNA-binding and nuclear import signal domains. Our results indicate that APRIN, in addition to its Pds5 similarity, has the features and localization of a hormone-induced chromatin regulator.

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Identification of thyroglobulin domain(s) involved in cell-surface binding and endocytosis

Cited by 5 publications

References 33 publications

Hydrogen peroxide-induced production of a 40 kDa immunoreactive thyroglobulin fragment in human thyroid cells: the onset of thyroid autoimmunity?

Hydrogen peroxide-induced production of a 40 kDa immunoreactive thyroglobulin fragment in human thyroid cells: the onset of thyroid autoimmunity?

Binding of heparin to human thyroglobulin (Tg) involves multiple binding sites including a region corresponding to a binding site of rat Tg

APRIN is a unique Pds5 paralog with features of a chromatin regulator in hormonal differentiation

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