Campos Jessica L O, Doratioto Tabata R, Videira Natalia B, Ribeiro Filho Helder V, Batista Fernanda A H, Fattori Juliana, Indolfo Nathalia de C, Nakahira Marcel, Bajgelman Marcio C, Cvoro Aleksandra, Laurindo Francisco R M, Webb Paul, Figueira Ana Carolina M
Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research Energy and Materials (CNPEM), São Paulo, Brazil.
Graduation Program of Biosciences and Bioactive Products Technology, Institute of Biology, State University of Campinas (Unicamp), São Paulo, Brazil.
Front Endocrinol (Lausanne). 2019 Jan 8;9:784. doi: 10.3389/fendo.2018.00784. eCollection 2018.
Thyroid hormone receptors (TRs) are responsible for mediating thyroid hormone (T3 and T4) actions at a cellular level. They belong to the nuclear receptor (NR) superfamily and execute their main functions inside the cell nuclei as hormone-regulated transcription factors. These receptors also exhibit so-called "non-classic" actions, for which other cellular proteins, apart from coregulators inside nuclei, regulate their activity. Aiming to find alternative pathways of TR modulation, we searched for interacting proteins and found that PDIA1 interacts with TRβ in a yeast two-hybrid screening assay. The functional implications of PDIA1-TR interactions are still unclear; however, our co-immunoprecipitation (co-IP) and fluorescence assay results showed that PDI was able to bind both TR isoforms . Moreover, T3 appears to have no important role in these interactions in cellular assays, where PDIA1 was able to regulate transcription of TRα and TRβ-mediated genes in different ways depending on the promoter region and on the TR isoform involved. Although PDIA1 appears to act as a coregulator, it binds to a TR surface that does not interfere with coactivator binding. However, the TR:PDIA1 complex affinity and activation are different depending on the TR isoform. Such differences may reflect the structural organization of the PDIA1:TR complex, as shown by models depicting an interaction interface with exposed cysteines from both proteins, suggesting that PDIA1 might modulate TR by its thiol reductase/isomerase activity.
甲状腺激素受体（TRs）负责在细胞水平介导甲状腺激素（T3和T4）的作用。它们属于核受体（NR）超家族，并作为激素调节的转录因子在细胞核内执行其主要功能。这些受体还表现出所谓的“非经典”作用，除了细胞核内的共调节因子外，其他细胞蛋白也可调节其活性。为了寻找TR调节的替代途径，我们搜索了相互作用蛋白，发现在酵母双杂交筛选试验中PDIA1与TRβ相互作用。PDIA1与TR相互作用的功能意义仍不清楚；然而，我们的共免疫沉淀（co-IP）和荧光分析结果表明，PDI能够结合两种TR亚型。此外，在细胞试验中，T3在这些相互作用中似乎没有重要作用，在这些试验中，PDIA1能够根据启动子区域和所涉及的TR亚型以不同方式调节TRα和TRβ介导基因的转录。尽管PDIA1似乎作为一种共调节因子发挥作用，但它与TR的一个表面结合，该表面不干扰共激活因子的结合。然而，TR:PDIA1复合物的亲和力和激活作用因TR亚型而异。这种差异可能反映了PDIA1:TR复合物的结构组织，如模型所示，该模型描绘了一个与两种蛋白质暴露的半胱氨酸相互作用的界面，表明PDIA1可能通过其硫醇还原酶/异构酶活性调节TR。
