Kim Junhong, Na Hyeonjin, Choi Si-Young, Oh Eun Ju, Lee Hyunsook, Ryu Sung Ho, Yunn Na-Oh, Cho Yunje
Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea.
Department of Biological Sciences, Institute of Molecular Biology and Genetics, Seoul National University, Seoul, Republic of Korea.
Exp Mol Med. 2025 Jul 2. doi: 10.1038/s12276-025-01494-1.
Insulin binding to the insulin receptor (IR) triggers signaling pathways that regulate glucose uptake and cell growth. In previous work, we identified a DNA aptamer, A62, which partially activates the IR. During engineering aptamers for improved in vivo stability, we discovered that crosslinking two A62 aptamers with linkers of varying lengths led to full phosphorylation of the IR, although activation remained selective to the AKT pathway. Here, to elucidate the mechanism behind this aptamer-induced full activation of the IR, we determined the structure of the IR in complex with a dimeric form of A62 (A62D) linked by an eight-nucleotide connector. We identified three distinct conformations of the IR: arrowhead-shaped, pseudo-arrowhead-shaped and pseudo-gamma-shaped. The pseudo-gamma-shaped conformation closely resembles the structure of a fully active IR bound by a single insulin molecule. In these configurations, only one A62 monomer (A62M) within the A62D dimer binds to the IR dimer. This binding brings the IR monomers into close proximity, promoting intermolecular trans-phosphorylation. Our findings provide valuable structural insights for the development of novel therapeutic strategies targeting the IR.
胰岛素与胰岛素受体（IR）结合会触发调节葡萄糖摄取和细胞生长的信号通路。在之前的研究中，我们鉴定出一种DNA适配体A62，它能部分激活IR。在对适配体进行工程改造以提高其体内稳定性的过程中，我们发现用不同长度的连接子将两个A62适配体交联会导致IR完全磷酸化，尽管激活仍对AKT通路具有选择性。在此，为了阐明这种适配体诱导IR完全激活背后的机制，我们确定了与通过八核苷酸连接子连接的二聚体形式的A62（A62D）形成复合物的IR的结构。我们鉴定出IR的三种不同构象：箭头形、伪箭头形和伪γ形。伪γ形构象与被单个胰岛素分子结合的完全活性IR的结构非常相似。在这些构型中，A62D二聚体内只有一个A62单体（A62M）与IR二聚体结合。这种结合使IR单体紧密靠近，促进分子间的反式磷酸化。我们的发现为开发针对IR的新型治疗策略提供了有价值的结构见解。
