Biophysical Society Thematic Meeting | Bucharest 2026

Biophysics of Membrane Reactions in Brian

Wednesday Speaker Abstracts

CHANNELRHODOPSINS WITH DEFINED BIOPHYSICAL PROPERTIES FOR OPTOGENETIC CONTROL OF NEURONAL ACTIVITY AND VISION

RESTORATION Satoshi Tsunoda

Nagoya Institute of Technology, Life Science and Applied Chemistry, Nagoya, Japan Optogenetics has become a powerful approach for interrogating and manipulating neuronal activity with high temporal precision. However, its broader application, particularly in therapeutic contexts, requires optogenetic actuators with enhanced light sensitivity, tailored spectral properties, and well-defined ion channel characteristics. In this study, we investigated two functionally distinct cation-conducting channelrhodopsins, GtCCR4 and KnChR, combining electrophysiology, structural analysis, and neuronal applications to advance optogenetic control and vision restoration. First, we analyzed the ion channel properties of a highly light-sensitive cation channelrhodopsin, GtCCR4, using whole-cell patch-clamp electrophysiology. GtCCR4 exhibited robust photocurrents under low-intensity illumination, favorable ion selectivity, and fast channel kinetics, making it well suited for high-temporal neuronal activation under light limited conditions. Optogenetic manipulation experiments in primary cultured neurons demonstrated reliable light-evoked depolarization and action potential firing under low-intensity illumination. Importantly, adeno-associated virus–mediated expression of GtCCR4 in the retinas of a retinitis pigmentosa model mouse restored robust retinal light responses, highlighting its suitability for device-free optogenetic vision restoration under physiologically relevant light conditions. In parallel, we characterized KnChR, a blue-shifted cation channelrhodopsin from Klebsormidium nitens. Electrophysiological recordings demonstrated fast photocurrent kinetics and short-wavelength sensitivity, consistent with its cryo-EM structure, which reveals a compact retinal-binding pocket and characteristic transmembrane helix rearrangements. Functional expression in primary neurons confirmed precise optical control of neuronal activity using UV light. Together, these results illustrate how mechanistically distinct channelrhodopsins— optimized either for high light sensitivity or for short-wavelength responsiveness—can be strategically applied to neural circuit manipulation and retinal degenerative disease therapy. This work underscores the importance of integrating biophysical characterization with cellular and in vivo validation for next-generation optogenetic tools.

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