Characteristic analysis and therapeutic development in rdw rats with congenital hypothyroidism

甲状腺球蛋白（Tg）基因（Tg- g2320r）突变是rdw大鼠遗传性侏儒症和甲状腺功能减退的主要原因。1)胰腺蛋白质组中弹性酶和脂肪酶的减少以及甲状腺素注射或甲状腺移植恢复的蛋白质。2) Tg-G2320R突变是rdw大鼠先天性甲状腺功能减退的原因，其中缺乏继发性甲状腺肿大（甲状腺肿）意味着甲状腺细胞死亡是疾病发病机制的一部分。我们发现突变体Tg-G2320R保留在内质网内，没有检测到甲状腺素的合成，持续暴露于游离酚，并且与激活的内质网应激反应相关，但与内质网相关降解（ERAD）不完全相关。Tg-G2320R与多种内质网驻留蛋白相关，最明显的是ERp72，包括共价Tg-ERp72相互作用。在pcc13甲状腺细胞中，诱导的ERp72过表达增加了细胞维持Tg半胱氨酸处于降低状态的能力。几种ER伴侣与新合成的Tg- g2320r的非共价相互作用随着时间的推移而减弱，与突变蛋白的ERAD同步，但即使在合成后2天，一小部分抗ERAD的Tg仍与ERp72进行共价结合。这种共价蛋白聚集体可能为rdw大鼠甲状腺细胞凋亡奠定了基础，防止甲状腺、甲状腺肿的形成。3)甲状腺激素缺乏的rdw大鼠发育海马中多巴胺d2样受体功能由兴奋性转化为抑制性。4)甲状腺移植可恢复rdw雄性大鼠的不育。

A mutation in the Thyroglobulin (Tg) gene (Tg-G2320R) is the primary cause of hereditary dwarfism and hypothyroidism in the rdw rat.1) Elastase and lipase reduced in pancreatic proteome and those proteins recovered by thyroxine injection or thyroid graft. 2) The Tg-G2320R mutation is responsible for congenital hypothyroidism in rdw rats, in which a lack of secondary thyroid enlargement (goiter) implicates death of thyrocytes as part of desease pathogenesis. We found that mutant Tg-G2320R was retained within the ER with no detectable synthesis of thyroxine, had persistent exposure of free chiols, and was associated with activated ER stress response but incomplete ER associated degradation (ERAD). Tg-G2320R associated with multiple ER resident proteins, most notably ERp72, including covalent Tg-ERp72 interactions. In PC C13 thyrocytes, inducible overexpression of ERp72 increased the ability of cells to maintain Tg cysteines in a reduced state. Non covalent interactions of several ER chaperones with newly synthesized Tg-G2320R diminished over time in paralled with ERAD of the mutant protein, yet a small ERAD-resistant Tg fraction remained engaged in covalent association with ERp72 even 2 days post-synthesis. Such covalent protein aggregates may set the stage for apoptotic thyrocyte cell death, preventing thyroid, goiter formation in rdw rats. 3) Dopamine D2-like receptor function is converted from excitatory to inhibitory by thyroxine in the developmental hippocampus using rdw rats having deficient thyroid hormone. 4) The infertility of rdw male rats was recovered by thyroid graft.