Institute of Physiology, RWTH Aachen University, 52074 Aachen, Germany.
Computational Biomedicine-Institute for Advanced Simulation/Institute of Neuroscience and Medicine, Forschungszentrum Jülich, 52425 Jülich, Germany.
J Med Chem. 2021 Sep 23;64(18):13299-13311. doi: 10.1021/acs.jmedchem.1c00447. Epub 2021 Aug 30.
Prolonged acidosis, as it occurs during ischemic stroke, induces neuronal death via acid-sensing ion channel 1a (ASIC1a). Concomitantly, it desensitizes ASIC1a, highlighting the pathophysiological significance of modulators of ASIC1a acid sensitivity. One such modulator is the opioid neuropeptide big dynorphin (Big Dyn) which binds to ASIC1a and enhances its activity during prolonged acidosis. The molecular determinants and dynamics of this interaction remain unclear, however. Here, we present a molecular interaction model showing a dynorphin peptide inserting deep into the acidic pocket of ASIC1a. We confirmed experimentally that the interaction is predominantly driven by electrostatic forces, and using noncanonical amino acids as photo-cross-linkers, we identified 16 residues in ASIC1a contributing to Big Dyn binding. Covalently tethering Big Dyn to its ASIC1a binding site dramatically decreased the proton sensitivity of channel activation, suggesting that Big Dyn stabilizes a resting conformation of ASIC1a and dissociates from its binding site during channel opening.
在缺血性中风期间，长时间的酸中毒会通过酸感应离子通道 1a（ASIC1a）诱导神经元死亡。同时，它使 ASIC1a 脱敏，突出了 ASIC1a 酸敏感性调节剂的病理生理意义。其中一种调节剂是阿片肽神经肽大 dynorphin（Big Dyn），它与 ASIC1a 结合，并在长时间的酸中毒期间增强其活性。然而，这种相互作用的分子决定因素和动力学仍然不清楚。在这里，我们提出了一个分子相互作用模型，显示 dynorphin 肽插入 ASIC1a 的酸性口袋深处。我们通过实验证实，这种相互作用主要是由静电力驱动的，并且使用非典型氨基酸作为光交联剂，我们确定了 ASIC1a 中 16 个残基有助于 Big Dyn 结合。将 Big Dyn 共价连接到其 ASIC1a 结合位点上，大大降低了通道激活的质子敏感性，这表明 Big Dyn 稳定了 ASIC1a 的静息构象，并在通道打开时从其结合位点解离。
