Multicolor photoreactions of the red light-activated channelrhodopsin Chrimson

• 成果类型: Article
• 署名作者: Vierock, Johannes; Kaufmann, Joel C. D.; Faiss, Lukas; Tillert, Linda; Krause, Benjamin S.; Fischer, Paul; Nguyen, Thi Bich Thao; Schmitz, Dietmar; Rost, Benjamin R.; Bartl, Franz; Hegemann, Peter
• 署名单位: Free University of Berlin; Humboldt University of Berlin; Charite Universitatsmedizin Berlin; Free University of Berlin; Humboldt University of Berlin; Humboldt University of Berlin; Humboldt University of Berlin; Helmholtz Association; German Center for Neurodegenerative Diseases (DZNE)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2513375122
• 发表日期: 2025-12-30
• 页码: e2513375122
• 关键词: channelrhodopsins; optogenetics; Chrimson; FTIR spectroscopy; retinal prosthesis; CHROMOPHORE STRUCTURE; TEMPORAL EVOLUTION; structural-changes; DARK ADAPTATION; proton-transfer; photocycle; photochemistry; variant; REACHR

摘要

Channelrhodopsins are light-gated ion channels that are used in modern neurosciences for the precise control of cellular ion fluxes by light. With a peak absorption at 585 nm, Chrimson is the most red-shifted cation-conducting ChR. It is frequently employed in multicolor experiments alongside blue light-sensitive optogenetic tools and is so far the only light-gated ion channel successfully applied in human vision restoration. However, its photoresponses to different wavelengths have not been thoroughly characterized. In this study, we identify multiple interconvertible dark states of Chrimson with distinct absorption and photokinetic properties. Combining electrophysiology and spectroscopy with optogenetic experiments in neurons, we unveil that this dark state heterogeneity is based on distinct protonation dynamics of the counterion complex and alternative retinal isomerization. In neurons, prolonged red illumination reduces Chrimson's red light sensitivity, which is reflected by a blue shift of the action spectrum. Blue light pulses reverse this shift and increase the excitability in subsequent red-light flashes. This understanding of wavelength-dependent photoreactions in Chrimson will improve the design of multicolor optogenetic experiments and inform strategies for optimizing Chrimson for therapeutic applications.