Labudda Kristin, Norahan Mohamad Javad, Hübner Lisa-Marie, Althoff Philipp, Gerwert Klaus, Lübben Mathias, Rudack Till, Kötting Carsten
Center for Protein Diagnostics (PRODI), Biospectroscopy, Ruhr University Bochum, Bochum, Germany.
Department of Biophysics, Ruhr University Bochum, Bochum, Germany.
Commun Biol. 2025 Aug 8;8(1):1183. doi: 10.1038/s42003-025-08560-4.
Optogenetics is a method to regulate cells, tissues and organisms using light. It is applied to study neurons and to develop diagnostic and therapeutic tools for neuron-related diseases. The cation-conducting channelrhodopsin ChR2 triggers photoinduced depolarization of neuronal cells but generates lower ion currents due to the syn-pathway of its branched photocycle. In contrast, the homologous anion-conducting ACR1 from Guillardia theta (GtACR1), exhibits high photocurrents. Here, we investigate the mechanistic cause for the observed high photocurrents in GtACR1 using FTIR spectroscopy. Unexpectedly, we discovered that the O intermediate of GtACR1 is photoactivable, allowing for fast and efficient channel reopening. Our vibrational spectra show a photocyclic reaction sequence after O excitation similar to the ground state photocycle but with slightly altered channel conformation and protonation states. Our results provide deeper insights into the gating mechanism of channelrhodopsins and pave the way to advance the development of optimized optogenetic tools in future.
光遗传学是一种利用光来调控细胞、组织和生物体的方法。它被应用于研究神经元，并开发用于治疗神经元相关疾病的诊断和治疗工具。阳离子传导性通道视紫红质ChR2会引发神经元细胞的光致去极化，但由于其分支光循环的同步途径，会产生较低的离子电流。相比之下，来自嗜热四膜虫的同源阴离子传导性ACR1（GtACR1）表现出高光电流。在这里，我们使用傅里叶变换红外光谱（FTIR）研究了GtACR1中观察到的高光电流的机制原因。出乎意料的是，我们发现GtACR1的O中间体是可光激活的，这使得通道能够快速有效地重新开放。我们的振动光谱显示，O激发后的光循环反应序列与基态光循环相似，但通道构象和质子化状态略有改变。我们的结果为通道视紫红质的门控机制提供了更深入的见解，并为未来推进优化光遗传学工具的开发铺平了道路。
