Thyroid hormone receptor β sumoylation is required for thyrotropin regulation and thyroid hormone production
Sujie Ke, … , Anna Milanesi, Gregory A. Brent
Sujie Ke, … , Anna Milanesi, Gregory A. Brent
Published July 8, 2021
Citation Information: JCI Insight. 2021;6(16):e149425. https://doi.org/10.1172/jci.insight.149425.
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Research Article Endocrinology

Thyroid hormone receptor β sumoylation is required for thyrotropin regulation and thyroid hormone production

Abstract

Thyroid hormone receptor β (THRB) is posttranslationally modified by small ubiquitin-like modifier (SUMO). We generated a mouse model with a mutation that disrupted sumoylation at lysine 146 (K146Q) and resulted in desumoylated THRB as the predominant form in tissues. The THRB K146Q mutant mice had normal serum thyroxine (T4), markedly elevated serum thyrotropin-stimulating hormone (TSH; 81-fold above control), and enlargement of both the pituitary and the thyroid gland. The marked elevation in TSH, despite a normal serum T4, indicated blunted feedback regulation of TSH. The THRB K146Q mutation altered the recruitment of transcription factors to the TSHβ gene promoter, compared with WT, in hyperthyroidism and hypothyroidism. Thyroid hormone content (T4, T3, and rT3) in the thyroid gland of the THRB K146Q mice was 10-fold lower (per gram tissue) than control, despite normal TSH bioactivity. The expression of thyroglobulin and dual oxidase 2 genes in the thyroid was reduced and associated with modifications of cAMP response element–binding protein DNA binding and cofactor interactions in the presence of the desumoylated THRB. Therefore, thyroid hormone production had both TSH-dependent and TSH-independent components. We conclude that THRB sumoylation at K146 was required for normal TSH feedback regulation and TH synthesis in the thyroid gland, by a TSH-independent pathway.

Authors

Sujie Ke, Yan-Yun Liu, Rajendiran Karthikraj, Kurunthachalam Kannan, Jingjing Jiang, Kiyomi Abe, Anna Milanesi, Gregory A. Brent

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Figure 6

TF binding patterns to the TSHβ gene promoter in hyperthyroid and hypothyroid WT and THRB K146Q mice.

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TF binding patterns to the TSHβ gene promoter in hyperthyroid and hypoth...
Mice (n = 15/genotype) were made hyperthyroid with T3 injection or hypothyroid with low iodine/PTU diet. The pituitaries were removed and pooled for the ChIP assay to detect TFs’ (THRB2, GATA2, FOG1, NCoR) binding to DNA regions (R1 and R2). (A) Diagram of the TSHβ gene regulatory region mediated by T3. The numerical labeling of the regulatory region corresponds to mouse thyrotropin gene (GenBank accession number AH002109.2). The segment is divided into 2 regions (R1, R2) that bind TFs, with the R1 containing the TSS and negative thyroid hormone response element (nTRE). GATA, Pit 1, and THRB binding sites, identified by sequence, are shown. (B and C) ChIP analysis of TF binding in R2 and R1 of TSHβ gene promoter in hyperthyroid WT mice. Inset shows modified y axis scale with the same data. Graphic summary of T3-induced TF DNA binding in suppression of TSHβ gene transcription. The transcription start site is shown with a green arrow and the magnitude of TF binding by the size of the TF symbol. (D and E) ChIP analysis of TF binding to the TSHβ gene promoter in the pituitary of hyperthyroid K146Q mice. (F and G) ChIP analysis of TF binding to the TSHβ gene promoter in the pituitary of hypothyroid WT mice. (H and I) ChIP analysis of TF binding to the TSHβ gene promoter in the pituitary of hypothyroid K146Q mice. The chromatin assay (PCR) data represent DNA-bound TFs, and a 10% fraction of the chromatin lysate supernatant was used as the input control and labeled as “relative enrichment.” The statistical analysis described in the text utilized paired Student’s t test. THRB, thyroid hormone receptor β; K146, lysine 146; TSH, thyrotropin-stimulating hormone; GATA2, GATA-binding protein 2; T3, triiodothyronine; TFs, transcription factors; TSS, transcription start site; NCoR, nuclear receptor corepressor 1; PTU, propylthiouracil.