FIRS Laboratories, RSR Ltd, Parc Ty Glas, Llanishen, Cardiff, UK.
J Mol Endocrinol. 2022 Dec 7;70(1). doi: 10.1530/JME-22-0120. Print 2023 Jan 1.
Determination of the full-length thyroid-stimulating hormone receptor (TSHR) structure by cryo-electron microscopy (cryo-EM) is described. The TSHR complexed with human monoclonal TSHR autoantibody K1-70™ (a powerful inhibitor of TSH action) was detergent solubilised, purified to homogeneity and analysed by cryo-EM. The structure (global resolution 3.3 Å) is a monomer with all three domains visible: leucine-rich domain (LRD), hinge region (HR) and transmembrane domain (TMD). The TSHR extracellular domain (ECD, composed of the LRD and HR) is positioned on top of the TMD extracellular surface. Extensive interactions between the TMD and ECD are observed in the structure, and their analysis provides an explanation of the effects of various TSHR mutations on TSHR constitutive activity and on ligand-induced activation. K1-70™ is seen to be well clear of the lipid bilayer. However, superimposition of M22™ (a human monoclonal TSHR autoantibody which is a powerful stimulator of the TSHR) on the cryo-EM structure shows that it would clash with the bilayer unless the TSHR HR rotates upwards as part of the M22™ binding process. This rotation could have an important role in TSHR stimulation by M22™ and as such provides an explanation as to why K1-70™ blocks the binding of TSH and M22™ without activating the receptor itself.
通过冷冻电镜（cryo-EM）确定全长促甲状腺激素受体（TSHR）结构。描述了与人类单克隆 TSHR 自身抗体 K1-70™（一种强大的 TSH 作用抑制剂）结合的 TSHR 复合物被去污剂溶解、纯化为均相并通过 cryo-EM 分析。该结构（全局分辨率为 3.3Å）是一个单体，所有三个结构域均可见：富含亮氨酸结构域（LRD）、铰链区（HR）和跨膜结构域（TMD）。TSHR 细胞外结构域（ECD，由 LRD 和 HR 组成）位于 TMD 细胞外表面的顶部。结构中观察到 TMD 和 ECD 之间存在广泛的相互作用，对其进行分析解释了各种 TSHR 突变对 TSHR 组成型活性和配体诱导激活的影响。K1-70™ 被认为远离脂质双层。然而，将 M22™（一种人类单克隆 TSHR 自身抗体，是 TSHR 的强大刺激剂）叠加在 cryo-EM 结构上表明，除非 TSHR HR 向上旋转作为 M22™结合过程的一部分，否则它会与双层发生冲突。这种旋转可能在 M22™刺激 TSHR 中起重要作用，因此解释了为什么 K1-70™ 阻止 TSH 和 M22™ 的结合而不激活受体本身。
