Proteolysis-targeting chimeras (PROTACs) are heterobifunctional molecules containing a ligand for a protein of interest linked to an E3 ubiquitin ligase ligand that induce protein degradation through E3 recruitment to the target protein. Small changes in PROTAC linkers can have drastic consequences, including loss of degradation activity, but the structural mechanisms governing such changes are unclear. To study this phenomenon, we screened PROTACs of diverse targeting modalities and identified dTAG-13 as an activator of the xenobiotic-sensing pregnane X receptor (PXR), which promiscuously binds various ligands. Characterization of dTAG-13 analogs and precursors revealed interplay between the PXR-binding moiety, linker, and E3 ligand that altered PXR activity without inducing degradation. A crystal structure of PXR ligand binding domain bound to a precursor ligand showed ligand-induced binding pocket distortions and a linker-punctured tunnel to the protein exterior at a region incompatible with E3 complex formation, highlighting the effects of linker environment on PROTAC activity.

中文翻译：

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PROTAC 介导的核受体激活而不是降解揭示了复杂的配体-受体相互作用网络


蛋白水解靶向嵌合体 （PROTAC） 是异双功能分子，含有与 E3 泛素连接酶配体相连的目标蛋白质的配体，该配体通过 E3 募集到靶蛋白来诱导蛋白质降解。PROTAC 连接子的微小变化可能会产生严重后果，包括降解活性的丧失，但控制这些变化的结构机制尚不清楚。为了研究这种现象，我们筛选了不同靶向模式的 PROTACs，并将 dTAG-13 鉴定为外源性感应孕烷 X 受体 （PXR） 的激活剂，该受体混杂结合各种配体。dTAG-13 类似物和前体的表征揭示了 PXR 结合部分、接头和 E3 配体之间的相互作用，这些配体改变了 PXR 活性而不诱导降解。与前体配体结合的 PXR 配体结合域的晶体结构显示配体诱导的结合口袋扭曲和在与 E3 复合物形成不相容的区域通往蛋白质外部的接头穿刺隧道，突出了接头环境对 PROTAC 活性的影响。