Department of Pharmacological Sciences, New York, NY, USA; Thyroid Research Unit, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
Thyroid Research Unit, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA; James J. Peters VA Medical Center, New York, NY, USA.
J Mol Graph Model. 2024 Jun;129:108725. doi: 10.1016/j.jmgm.2024.108725. Epub 2024 Feb 11.
The receptor for thyroid stimulating hormone (TSHR), a GPCR, is the primary antigen in autoimmune hyperthyroidism (Graves' disease) caused by stimulating TSHR antibodies. While we have previously published a full length model of the TSHR, including its leucine rich domain (LRD), linker region (LR) and transmembrane domain (TMD), to date, only a partial LRD (aa 21-261) stabilized with TSHR autoantibodies has been crystallized. Recently, however, cryo-EM structures of the full-length TSHR have been published but they include only an incomplete LR. We have now utilized the cryo-EM models, added disulfide bonds to the LR and performed longer (3000 ns) molecular dynamic (MD) simulations to update our previous model of the entire full-length TSHR, with and without the presence of TSH ligand. As in our earlier work, the new model was embedded in a lipid membrane and was solvated with water and counterions. We found that the 3000 ns Molecular Dynamic simulations showed that the structure of the LRD and TMD were remarkably constant while the LR, known more commonly as the "hinge region", again showed significant flexibility, forming several transient secondary structural elements. Analysis of the new simulations permitted a detailed examination of the effect of TSH binding on the structure of the TSHR. We found a structure-stabilizing effect of TSH, including increased stability of the LR, which was clearly demonstrated by analyzing several intrinsic receptor properties including hydrogen bonding, fluctuation of the LRD orientation, and radius of gyration. In conclusion, we were able to quantify the flexibility of the TSHR and show its increased stability after TSH binding. These data indicated the important role of ligands in directing the signaling structure of a receptor.
促甲状腺激素受体（TSHR）是一种 G 蛋白偶联受体，是由刺激 TSHR 抗体引起的自身免疫性甲状腺功能亢进（格雷夫斯病）的主要抗原。虽然我们之前已经发表了包括富含亮氨酸域（LRD）、连接区（LR）和跨膜域（TMD）在内的全长 TSHR 模型，但迄今为止，只有与 TSHR 自身抗体稳定的部分 LRD（aa21-261）被结晶。然而，最近已经发表了全长 TSHR 的冷冻电镜结构，但它们仅包含不完整的 LR。我们现在利用冷冻电镜模型，在 LR 中添加了二硫键，并进行了更长时间（3000 纳秒）的分子动力学（MD）模拟，以更新我们之前带有和不带有 TSH 配体的整个全长 TSHR 模型。与我们之前的工作一样，新模型被嵌入脂质膜中，并用水和抗衡离子进行溶剂化。我们发现，3000 纳秒的分子动力学模拟表明，LRD 和 TMD 的结构非常稳定，而 LR，通常称为“铰链区”，再次表现出显著的灵活性，形成了几个瞬态二级结构元件。对新模拟的分析允许详细检查 TSH 结合对 TSHR 结构的影响。我们发现 TSH 具有稳定结构的作用，包括 LR 的稳定性增加，这通过分析几个内在受体特性（包括氢键、LRD 取向的波动和回转半径）得到了明确的证明。总之，我们能够量化 TSHR 的灵活性，并显示出 TSH 结合后其稳定性的增加。这些数据表明配体在指导受体信号结构方面的重要作用。
