Endoplasmic Reticulum stress and thyroid cell death

内质网应激和甲状腺细胞死亡

• 批准号: 10595662
• 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
• 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/10595662
• 关键词: Age; Alleles; Animal Model; Animals; Attention; Breeding; 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; Inflammatory Infiltrate; Ingestion; Inherited; Intake; Iodides; Iodination reaction; Knock-in; Knock-in Mouse; Knockout Mice; Life; Link; Livestock; Malignant Neoplasms; Malignant neoplasm of thyroid; Mediating; Modeling; Mus; Mutation; Nerve Degeneration; Pathogenicity; Patients; Persons; Physiology; Population; Proliferating; 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

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 甲状腺同型甲状腺素（T4）的有效产生需要甲状腺球蛋白（TG）的碘化，这是 在内质网中合成（ER）合成，并经历折叠和运输到甲状腺叶状管腔 发生碘化的地方。内源性T4是由甲状腺细胞产生的100％，Tg中T4的形成 在进化中保守了5亿年。迄今为止，数百种不同的致病性突变 已经发现TG基因在人类中引起先天性甲状腺功能减退症。遗传性甲状腺功能减退症 纯合（或复合杂合）TG突变很少见，但是单个致病性TG的频率 人口中的等位基因非常普遍（≥1：200个个体）。迄今为止，所有TG突变体误折叠 蛋白质被困在ER中，导致ER应力。我们最近报道说，在未处理的TG纯合子中， 内源性甲状腺激素合成仍然发生了TG从ER出口的绝望失败。机制 涉及甲状腺上皮细胞死亡，将死亡的甲状腺细胞延伸到甲状腺卵泡的腔内，导致 这些细胞中这些细胞在叶片管腔中的瓦解和碘化。 TG蛋白在大量表达中 甲状腺细胞和人群中杂合TG突变的极高频率现在使我们进入 询问甲状腺上皮细胞死亡是否也可能是（迄今未跨性的）宽度特征 在简单的杂合子中，突变体TG的个体。这可以在动物模型中很容易测试。 此外，在纯合RDW/RDW（TG-G2298R）大鼠中，甲状腺细胞死亡长期以来一直被认为是一个因素 阻止甲状腺肿的增长。值得注意的是，我们现在发现，在先天甲状腺肿的鼠标（COG/COG，TG-L2263P）中， 也是广泛的甲状腺细胞死亡（尽管如此，甲状腺生长仍超过了）。在当前的提议中 1）我们已经设计了RDW/RDW敲击小鼠，并将直接比较细胞的生长和细胞死亡 在COG/COG小鼠中查看。 2）我们将在这两个模型的简单杂合子中检查甲状腺细胞死亡，这是 具有完全正常的血清T4水平，但暴露于甲状腺细胞ER应激。 3）由于杂合突变体TG错误折叠 在ER中，它至少部分通过ER相关的蛋白质降解（ERAD）来降解。我们发现 TG的缺陷导致甲状腺炎随着炎症细胞和叶片的融合而浸润。 4）挤出 进入叶片管腔的螺旋细胞可能会通过周围的 卵泡细胞作为细胞毒性的有助于机制。为了测试这一点，我们将检查一个TG-KO鼠标模型 其中TSH刺激的过度生长（而不是ER应力）将甲状腺细胞驱动到叶状体中，暴露于 敏感的基底外侧质膜到管腔的氧化 /碘化环境，可能 触发甲状腺细胞死亡。总而言之，该提案的所有目的都将重点介绍ER压力的问题 - 甲状腺细胞死亡的依赖和独立机制。