AbstractThe FK506‐binding protein 51 (FKBP51) is a promising target in a variety of disorders including depression, chronic pain, and obesity. Previous FKBP51‐targeting strategies were restricted to occupation of the FK506‐binding site, which does not affect core functions of FKBP51. Here, we report the discovery of the first FKBP51 proteolysis targeting chimera (PROTAC) that enables degradation of FKBP51 abolishing its scaffolding function. Initial synthesis of 220 FKBP‐focused PROTACs yielded a plethora of active PROTACs for FKBP12, six for FKBP51, and none for FKBP52. Structural analysis of a binary FKBP12:PROTAC complex revealed the molecular basis for negative cooperativity. Linker‐based optimization of first generation FKBP51 PROTACs led to the PROTAC SelDeg51 with improved cellular activity, selectivity, and high cooperativity. The structure of the ternary FKBP51:SelDeg51:VCB complex revealed how SelDeg51 establishes cooperativity by dimerizing FKBP51 and the von Hippel‐Lindau protein (VHL) in a glue‐like fashion. SelDeg51 efficiently depletes FKBP51 and reactivates glucocorticoid receptor (GR)‐signalling, highlighting the enhanced efficacy of full protein degradation compared to classical FKBP51 binding.
摘要 FK506结合蛋白51(FKBP51)是治疗包括抑郁症、慢性疼痛和肥胖症在内的多种疾病的有望靶点。以往的 FKBP51 靶向策略仅限于占据 FK506 结合位点,这不会影响 FKBP51 的核心功能。在这里,我们报告了发现的首个 FKBP51 蛋白解质靶向嵌合体 (PROTAC),它能使 FKBP51 降解,取消其支架功能。初步合成了 220 个以 FKBP 为靶点的 PROTAC,发现了大量针对 FKBP12 的活性 PROTAC,6 个针对 FKBP51,而没有针对 FKBP52 的活性 PROTAC。对二元 FKBP12:PROTAC 复合物的结构分析揭示了负合作性的分子基础。对第一代 FKBP51 PROTAC 进行了基于连接子的优化,从而产生了具有更好的细胞活性、选择性和高合作性的 PROTAC SelDeg51。FKBP51:SelDeg51:VCB三元复合物的结构揭示了SelDeg51如何以胶水状的方式二聚FKBP51和von Hippel-Lindau蛋白(VHL),从而建立合作性。SelDeg51能有效地耗尽FKBP51并重新激活糖皮质激素受体(GR)信号,与传统的FKBP51结合相比,突出了完全降解蛋白质的功效。