Department of Molecular and Cellular Biology, University of Geneva, Geneva, Switzerland.
Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland.
Nat Commun. 2024 Oct 9;15(1):8687. doi: 10.1038/s41467-024-52947-6.
The μ-opioid receptor (μOR), a prototypical G protein-coupled receptor (GPCR), is the target of opioid analgesics such as morphine and fentanyl. Due to the severe side effects of current opioid drugs, there is considerable interest in developing novel modulators of μOR function. Most GPCR ligands today are small molecules, however biologics, including antibodies and nanobodies, represent alternative therapeutics with clear advantages such as affinity and target selectivity. Here, we describe the nanobody NbE, which selectively binds to the μOR and acts as an antagonist. We functionally characterize NbE as an extracellular and genetically encoded μOR ligand and uncover the molecular basis for μOR antagonism by determining the cryo-EM structure of the NbE-μOR complex. NbE displays a unique ligand binding mode and achieves μOR selectivity by interactions with the orthosteric pocket and extracellular receptor loops. Based on a β-hairpin loop formed by NbE that deeply protrudes into the μOR, we design linear and cyclic peptide analogs that recapitulate NbE's antagonism. The work illustrates the potential of nanobodies to uniquely engage with GPCRs and describes lower molecular weight μOR ligands that can serve as a basis for therapeutic developments.
μ 阿片受体（μOR）是一种典型的 G 蛋白偶联受体（GPCR），是吗啡和芬太尼等阿片类镇痛药的作用靶点。由于目前阿片类药物存在严重的副作用，因此人们非常有兴趣开发新型μOR 功能调节剂。目前大多数 GPCR 配体都是小分子，但是生物制剂，包括抗体和纳米抗体，代表了具有明显优势的替代疗法，例如亲和力和靶标选择性。在这里，我们描述了一种选择性结合 μOR 并作为拮抗剂的纳米抗体 NbE。我们将 NbE 作为一种细胞外和遗传编码的 μOR 配体进行功能表征，并通过确定 NbE-μOR 复合物的冷冻电镜结构来揭示 μOR 拮抗作用的分子基础。NbE 显示出独特的配体结合模式，并通过与正位口袋和细胞外受体环的相互作用实现 μOR 选择性。基于 NbE 形成的β发夹环，我们设计了线性和环状肽类似物，重现了 NbE 的拮抗作用。这项工作说明了纳米抗体与 GPCR 独特结合的潜力，并描述了可以作为治疗开发基础的低分子量 μOR 配体。
