Dataset Information

A novel thyroid hormone receptor isoform, TR?2-46, promotes SKP2 expression and retinoblastoma cell proliferation.

ABSTRACT: Retinoblastoma is a childhood retinal tumor that develops from cone photoreceptor precursors in response to inactivating RB1 mutations and loss of functional RB protein. The cone precursor's response to RB loss involves cell type-specific signaling circuitry that helps to drive tumorigenesis. One component of the cone precursor circuitry, the thyroid hormone receptor ?2 (TR?2), enables the aberrant proliferation of diverse RB-deficient cells in part by opposing the down-regulation of S-phase kinase-associated protein 2 (SKP2) by the more widely expressed and tumor-suppressive TR?1. However, it is unclear how TR?2 opposes TR?1 to enable SKP2 expression and cell proliferation. Here, we show that in human retinoblastoma cells TR?2 mRNA encodes two TR?2 protein isoforms: a predominantly cytoplasmic 54-kDa protein (TR?2-54) corresponding to the well-characterized full-length murine Tr?2 and an N-terminally truncated and exclusively cytoplasmic 46-kDa protein (TR?2-46) that starts at Met-79. Whereas TR?2 knockdown decreased SKP2 expression and impaired retinoblastoma cell cycle progression, re-expression of TR?2-46 but not TR?2-54 stabilized SKP2 and restored proliferation to an extent similar to that of ectopic SKP2 restoration. We conclude that TR?2-46 is an oncogenic thyroid hormone receptor isoform that promotes SKP2 expression and SKP2-dependent retinoblastoma cell proliferation.

SUBMITTER: Li Z

PROVIDER: S-EPMC6393598 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

A novel thyroid hormone receptor isoform, TRβ2-46, promotes SKP2 expression and retinoblastoma cell proliferation.

Li Zhengke Z Qi Dong-Lai DL Singh Hardeep P HP Zou Yue Y Shen Binghui B Cobrinik David D

The Journal of biological chemistry 20190114 8

Retinoblastoma is a childhood retinal tumor that develops from cone photoreceptor precursors in response to inactivating <i>RB1</i> mutations and loss of functional RB protein. The cone precursor's response to RB loss involves cell type-specific signaling circuitry that helps to drive tumorigenesis. One component of the cone precursor circuitry, the thyroid hormone receptor β2 (TRβ2), enables the aberrant proliferation of diverse RB-deficient cells in part by opposing the down-regulation of S-ph ...[more]

PMID: 30643022

Similar Datasets

Project description:The thyroid hormone receptor ? gene (THRA) transcript is alternatively spliced to generate either thyroid hormone receptor (TR)?1 or a non-hormone-binding variant protein, TR?2, the function of which is unknown. Here, we describe the first patients identified with a mutation in THRA that affects both TR?1 and TR?2, and compare them with patients who have resistance to thyroid hormone owing to a mutation affecting only TR?1, to delineate the relative roles of TR?1 and TR?2.We did clinical, biochemical, and genetic analyses of an index case and her two sons. We assessed physical and radiological features, thyroid function, physiological and biochemical markers of thyroid hormone action, and THRA sequence.The patients presented in childhood with growth failure, developmental delay, and constipation, which improved after treatment with thyroxine, despite normal concentrations of circulating thyroid hormones. They had similar clinical (macrocephaly, broad faces, skin tags, motor dyspraxia, slow speech), biochemical (subnormal ratio of free thyroxine:free tri-iodothyronine [T3], low concentration of total reverse T3, high concentration of creatine kinase, mild anaemia), and radiological (thickened calvarium) features to patients with TR?1-mediated resistance to thyroid hormone, although our patients had a heterozygous mis-sense mutation (Ala263Val) in both TR?1 and TR?2 proteins. The Ala263Val mutant TR?1 inhibited the transcriptional function of normal receptor in a dominant-negative fashion. By contrast, function of Ala263Val mutant TR?2 matched its normal counterpart. In vitro, high concentrations of T3 restored transcriptional activity of Ala263Val mutant TR?1, and reversed the dominant-negative inhibition of its normal counterpart. High concentrations of T3 restored expression of thyroid hormone-responsive target genes in patient-derived blood cells.TR?1 seems to be the principal functional product of the THRA gene. Thyroxine treatment alleviates hormone resistance in patients with mutations affecting this gene, possibly ameliorating the phenotype. These findings will help the diagnosis and treatment of other patients with resistance to thyroid hormone resulting from mutations in THRA.Wellcome Trust, NIHR Cambridge Biomedical Research Centre, Marie Curie Actions, Foundation for Development of Internal Medicine in Europe.

Project description:Thyroid hormones (THs) elicit significant effects on numerous physiological processes, such as growth, development, and metabolism. A lack of thyroid hormones is not compatible with normal health. Most THs effects are mediated by two different thyroid hormone receptor (TR) isoforms, namely TR? and TR?, with the TR? isoform known to be responsible for the main beneficial effects of TH on liver. In brain, despite the crucial role of TR? isoform in neuronal development, TR? has been proposed to play a role in the remyelination processes. Consequently, over the past two decades, much effort has been applied in developing thyroid hormone analogs capable of uncoupling beneficial actions on liver (triglyceride and cholesterol lowering) and central nervous system (CNS) (oligodendrocyte proliferation) from deleterious effects on the heart, muscle and bone. Sobetirome (GC-1) and subsequently Eprotirome (KB2115) were the first examples of TR? selective thyromimetics, with Sobetirome differing from the structure of thyronines because of the absence of halogens, biaryl ether oxygen, and amino-acidic side chain. Even though both thyromimetics showed encouraging actions against hypercholesterolemia, non-alcoholic steatohepatitis (NASH) and in the stimulation of hepatocytes proliferation, they were stopped after Phase 1 and Phase 2-3 clinical trials, respectively. In recent years, advances in molecular and structural biology have facilitated the design of new selective thyroid hormone mimetics that exhibit TR isoform-selective binding, and/or liver- and tissue-selective uptake, with Resmetirom (MGL-3196) and Hep-Direct prodrug VK2809 (MB07811) probably representing two of the most promising lipid lowering agents, currently under phase 2-3 clinical trials. More recently the application of a comprehensive panel of ADME-Toxicity assays enabled the selection of novel thyromimetic IS25 and its prodrug TG68, as very powerful lipid lowering agents both in vitro and in vivo. In addition to dyslipidemia and other liver pathologies, THs analogs could also be of value for the treatment of neurodegenerative diseases, such as multiple sclerosis (MS). Sob-AM2, a CNS- selective prodrug of Sobetirome has been shown to promote significant myelin repair in the brain and spinal cord of mouse demyelinating models and it is rapidly moving into clinical trials in humans. Taken together all these findings support the great potential of selective thyromimetics in targeting a large variety of human pathologies characterized by altered metabolism and/or cellular differentiation.

Dataset Information

A novel thyroid hormone receptor isoform, TR?2-46, promotes SKP2 expression and retinoblastoma cell proliferation.

Publications

A novel thyroid hormone receptor isoform, TRβ2-46, promotes SKP2 expression and retinoblastoma cell proliferation.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure