Endoplasmic Reticulum stress and thyroid cell death

内质网应激和甲状腺细胞死亡

基本信息

批准号：
10414536
负责人：
PETER ARVAN
金额：
$ 39万
依托单位：
UNIVERSITY OF MICHIGAN AT ANN ARBOR
依托单位国家：
美国
项目类别：
财政年份：
2022
资助国家：
美国
起止时间：
2022-04-01 至 2027-03-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10414536
关键词：
Alleles Animal Model Animals Attention Cell Death Cell membrane Cells Cessation of life Clinical Cretinism Curiosities Development Diabetes Mellitus Disease Dwarfism Endoplasmic Reticulum Engineering Environment Epithelial Cells Evolution Exhibits Failure Frequencies Gene Mutation Generations Genetic Glycoproteins Goiter Grant Growth Growth Disorders Heterozygote Homozygote Human Human Inbreeding Hyperplasia Hypothyroidism Inbreeding Individual Infiltration Inflammatory Ingestion Inherited Intake Iodides Iodination reaction Knock-in Knock-in Mouse Knockout Mice Life Link Livestock Malignant Neoplasms Malignant neoplasm of thyroid Mediating Mind Modeling Mus Mutation Nerve Degeneration Pathogenicity Patients Persons Physiology Population Proteins Rattus Reporting Role Serum Severities Sheep System TG gene Testing Thyroglobulin Thyroid Adenoma Thyroid Diseases Thyroid Gland Thyroid Hormones Thyroiditis Thyroxine Tissues Travel Triiodothyronine apical membrane autosomal recessive trait blocking factor cell growth cytotoxicity endoplasmic reticulum stress human disease in vivo misfolded protein mouse model mutant oxidation protein degradation proteotoxicity trafficking

项目摘要

ABSTRACT Efficient generation of the thyroid hormone thyroxine (T4) requires the iodination of thyroglobulin (Tg), which is synthesized in the endoplasmic reticulum (ER) and undergoes folding and trafficking to the thyroid follicle lumen wherein iodination takes place. Endogenous T4 is 100% produced by thyrocytes, and the formation of T4 in Tg has been conserved in evolution for ≥ 500 million years. To date, hundreds of different pathogenic mutations of the TG gene have been found to cause congenital hypothyroidism in humans. Genetic hypothyroidism from homozygous (or compound heterozygous) TG mutation is rare, but the frequency of a single pathogenic TG allele in the human population is very common (≥ 1:200 individuals). All Tg mutants studied to date are misfolded proteins trapped in the ER, causing ER stress. We recently reported that in untreated TG homozygotes, endogenous thyroid hormone synthesis still occurs despite failure of Tg export from the ER. The mechanism involves thyroid epithelial cell death, with extrusion of dead thyrocytes into the lumen of thyroid follicles, leading to the disintegration and iodination of those cells in the follicle lumen. Massive expression of Tg protein in thyrocytes, and the extremely high frequency of heterozygous TG mutations in the population, now leads us to ask whether thyroid epithelial cell death may also be a (heretofore unsuspected) widespread feature across individuals who are simple heterozygotes for mutant TG. This can be easily tested in animal models. Additionally, in homozygous rdw/rdw (Tg-G2298R) rats, thyroid cell death has long been recognized as a factor blocking goiter growth. Remarkably, we now find that in the congenital goiter mouse (cog/cog, Tg-L2263P), there is also widespread thyroid cell death (that is nevertheless outpaced by thyroid growth). In the current proposal, 1) we have engineered a rdw/rdw knockin mouse and will directly compare cell growth and cell death to that seen in cog/cog mice. 2) We will examine thyroid cell death in simple heterozygotes of these two models, which have perfectly normal serum T4 levels but exhibit thyrocyte ER stress. 3) As heterozygous mutant Tg is misfolded in the ER, it may be degraded at least in part by ER-associated protein degradation (ERAD). We find that defective ERAD of Tg leads to a thyroiditis with infiltration of inflammatory cells and follicle involuion. 4) Extrusion of thyrocytes into the follicle lumen may expose non-apical portions of the cell to iodination by surrounding follicular cells as a contributing mechanism of cytotoxicity. To test this, we will examine a TG-KO mouse model in which TSH-stimulated overgrowth (and not ER stress) drives thyrocytes into the follicle lumen, exposing the sensitive basolateral plasma membrane to the oxidative / iodination environment of the lumen, where it may trigger thyroid cell death. In summary, all of the Aims of this proposal will highlight questions of ER stress- dependent and independent mechanisms of thyrocyte death.

抽象的甲状腺激素甲状腺素（T4）的有效产生需要甲状腺球蛋白（Tg）的碘化，这是在内质网 (ER) 中合成，并折叠并运输至甲状腺滤泡腔因此，内源性 T4 100% 由甲状腺细胞产生，并在 Tg 中形成 T4。迄今为止，在进化中已保守了 5 亿年以上，有数百种不同的致病突变。 TG 基因已被发现会导致人类先天性甲状腺功能减退症。纯合（或复合杂合）TG突变很少见，但单一致病TG的频率等位基因在人群中非常常见（≥ 1:200 个体）。迄今为止研究的所有 Tg 突变体都是错误折叠的。蛋白质被困在 ER 中，导致 ER 应激。我们最近报道，在未经处理的 TG 纯合子中，尽管内质网 Tg 输出失败，但内源性甲状腺激素合成仍然发生。涉及甲状腺上皮细胞死亡，死亡的甲状腺细胞被挤出到甲状腺滤泡腔中，导致导致卵泡腔内这些细胞的崩解和碘化 Tg 蛋白的大量表达。甲状腺细胞，以及人群中杂合 TG 突变的极高频率，现在使我们询问甲状腺上皮细胞死亡是否也可能是一个（迄今为止未被怀疑的）普遍特征这可以很容易地在动物模型中进行测试。此外，在纯合 rdw/rdw (Tg-G2298R) 大鼠中，甲状腺细胞死亡长期以来被认为是一个因素值得注意的是，我们现在发现在先天性甲状腺肿小鼠（cog/cog，Tg-L2263P）中存在这种现象。也是广泛的甲状腺细胞死亡（但在目前的提议中，其速度超过了甲状腺生长）。 1) 我们设计了一只 rdw/rdw 敲入小鼠，并将直接比较细胞生长和细胞死亡 2) 我们将检查这两种模型的简单杂合子中的甲状腺细胞死亡。血清 T4 水平完全正常，但表现出甲状腺细胞 ER 应激 3) 由于杂合突变 Tg 错误折叠。在 ER 中，它可能至少部分被 ER 相关蛋白降解 (ERAD) 降解。 Tg 的 ERAD 缺陷会导致甲状腺炎，伴有炎症细胞浸润和卵泡退化 4) 挤压。甲状腺细胞进入滤泡腔可能会使细胞的非顶端部分暴露于周围环境的碘化作用下。为了测试这一点，我们将检查 TG-KO 小鼠模型。其中 TSH 刺激的过度生长（而非 ER 应激）驱使甲状腺细胞进入卵泡腔，从而暴露基底外侧质膜对管腔的氧化/碘化环境敏感，它可能总之，该提案的所有目标都将突出 ER 应激问题。甲状腺细胞死亡的依赖性和独立机制。