Vogel Amber, Blakely Alan, Dao Yuankun, Lin Nai-Pin, Chou Danny, Hill Christopher P
Department of Biochemistry, Spencer Fox Eccles School of Medicine, University of Utah, Salt Lake City, UT, USA.
Division of Endocrinology and Diabetes, Department of Pediatrics, School of Medicine, Stanford University, Palo Alto, CA, USA.
bioRxiv. 2025 Aug 24:2025.08.23.671589. doi: 10.1101/2025.08.23.671589.
Congenital hyperinsulinism (HI) is a rare genetic disease characterized by overproduction of insulin. One class of potential HI treatments is insulin receptor (IR) antagonists like S961 and Ins-AC-S2, peptides composed of binding segments for each of the IR sites capable of binding insulin: site 1 and site 2. Notably, S597 - containing the same IR binding segments as S961 but in the opposite order (site 2-site 1) - is an IR agonist rather than an antagonist. Using cryo-EM, we show how both S961 and Ins-AC-S2 bind an inactive conformation of IR, thereby explaining their antagonism. Furthermore, our structures reveal how agonist vs. antagonist activity is dictated by the order of site 1- and site 2-binding modules in bivalent ligands. Additionally, we uncover subtle differences between the binding mechanisms of S961 and Ins-AC-S2 to IR, which include displacement or engagement of αCT, respectively, and a novel binding interface between the Ins-AC-S2 insulin and the receptor. These structural insights may inform development of next generation IR antagonists for treatment of HI.
先天性高胰岛素血症（HI）是一种罕见的遗传性疾病，其特征是胰岛素过度分泌。一类潜在的HI治疗方法是胰岛素受体（IR）拮抗剂，如S961和Ins-AC-S2，它们是由能够结合胰岛素的IR位点（位点1和位点2）的结合片段组成的肽。值得注意的是，S597 - 包含与S961相同的IR结合片段，但顺序相反（位点2 - 位点1） - 是一种IR激动剂而非拮抗剂。利用冷冻电镜，我们展示了S961和Ins-AC-S2如何结合IR的无活性构象，从而解释了它们的拮抗作用。此外，我们的结构揭示了激动剂与拮抗剂活性是如何由二价配体中位点1和位点2结合模块的顺序决定的。此外，我们还发现了S961和Ins-AC-S2与IR结合机制之间的细微差异，其中包括分别对αCT的置换或结合，以及Ins-AC-S2胰岛素与受体之间的新型结合界面。这些结构见解可能为开发用于治疗HI的下一代IR拮抗剂提供信息。
