背景:甲状腺易受上皮细胞异常生长的影响,常导致甲状腺功能异常。丝氨酸-苏氨酸蛋白激酶的机制靶点雷帕霉素(mTOR)调节细胞代谢,扩散,通过两种不同的蛋白质复合物生长,mTORC1和mTORC2。PI3K-Akt-mTORC1通路的过度活性与甲状腺癌的侵袭性增强密切相关,但最近的研究表明mTORC2也参与其中。
方法:为了阐明mTORC1在甲状腺细胞中的作用,我们开发了一种新的小鼠模型,通过删除结节性硬化症2(TSC2),mTORC1在甲状腺细胞中获得功能,mTORC1的细胞内抑制剂。
结果:得到的TPO-TSC2KO小鼠表现出70-80%的TSC2水平降低,导致mTORC1活性增加六倍。雄性和雌性TPO-TSC2KO小鼠的甲状腺在整个生命周期中都显示出快速的增大和持续的生长。有较大的卵泡,胶体和上皮面积增加。在TPO-TSC2KO小鼠中,我们观察到Ki67染色表明甲状腺细胞增殖升高,细胞周期蛋白D3表达升高。mTORC1激活导致参与甲状腺激素生物合成的关键基因逐渐下调,包括甲状腺球蛋白(Tg),甲状腺过氧化物酶(Tpo),和碘化钠转运体(Nis),而Tff1,Pax8和Mct8mRNA水平未受影响。在TPO-TSC2KO小鼠中NIS蛋白表达也减少。用mTORC1抑制剂雷帕霉素治疗可防止TPO-TSC2KO小鼠的甲状腺质量扩张并恢复基因表达改变。尽管T4、T3和TSH血浆水平在2月龄时正常,在6月龄和12月龄时观察到T4的轻微降低和TSH水平的升高,而TPO-TSC2KO中的T3与同窝对照小鼠相比仍然相似.
结论:我们的甲状腺细胞特异性小鼠模型显示mTORC1激活抑制TH生物合成,抑制甲状腺细胞基因表达,促进增长和扩散。
Background: The thyroid gland is susceptible to abnormal epithelial cell growth, often resulting in thyroid dysfunction. The serine-threonine protein kinase mechanistic target of rapamycin (mTOR) regulates cellular metabolism, proliferation, and growth through two different protein complexes, mTORC1 and mTORC2. The PI3K-Akt-mTORC1 pathway\'s overactivity is well associated with heightened aggressiveness in thyroid cancer, but recent studies indicate the involvement of mTORC2 as well. Methods: To elucidate mTORC1\'s role in thyrocytes, we developed a novel mouse model with mTORC1 gain of function in thyrocytes by deleting tuberous sclerosis complex 2 (TSC2), an intracellular inhibitor of mTORC1. Results: The resulting TPO-TSC2KO mice exhibited a 70-80% reduction in TSC2 levels, leading to a sixfold increase in mTORC1 activity. Thyroid glands of both male and female TPO-TSC2KO mice displayed rapid enlargement and continued growth throughout life, with larger follicles and increased colloid and epithelium areas. We observed elevated thyrocyte proliferation as indicated by Ki67 staining and elevated cyclin D3 expression in the TPO-TSC2KO mice. mTORC1 activation resulted in a progressive downregulation of key genes involved in thyroid hormone biosynthesis, including thyroglobulin (Tg), thyroid peroxidase (Tpo), and sodium-iodide symporter (Nis), while Tff1, Pax8, and Mct8 mRNA levels remained unaffected. NIS protein expression was also diminished in TPO-TSC2KO mice. Treatment with the mTORC1 inhibitor rapamycin prevented thyroid mass expansion and restored the gene expression alterations in TPO-TSC2KO mice. Although total thyroxine (T4), total triiodothyronine (T3), and TSH plasma levels were normal at 2 months of age, a slight decrease in T4 and an increase in TSH levels were observed at 6 and 12 months of age while T3 remained similar in TPO-TSC2KO compared with littermate control mice. Conclusions: Our thyrocyte-specific mouse model reveals that mTORC1 activation inhibits thyroid hormone (TH) biosynthesis, suppresses thyrocyte gene expression, and promotes growth and proliferation.