Duan, X., Zhang, C., Ott, S., Zhang, Z., Ruse, C., Dannhäuser, S., Jacobi, R., Ehmann, N., Sachidanandan, D., Nagel, G., Heckmann, M., Kittel, R.J., Gottschalk, A., Claridge-Chang, A., Gao, S. (2026). Stabilized Ion Selectivity Corrects Activation Drift in Kalium Channelrhodopsins.  Adv Sci (Weinh) 13(6): e09180.

FBrf0264505

Research paper

Effective optogenetic inhibition of neuronal activity requires tools that reliably silence neurons across cell types and conditions. K[+]-selective channelrhodopsins (KCRs) have emerged as attractive alternatives to chloride-conducting channels for optogenetic inhibition of cellular excitability, but many KCR variants exhibit an ion selectivity shift toward Na[+] under prolonged illumination. Through behavioral and electrophysiological analyses in Drosophila, and Caenorhabditis elegans, it is found that both the absolute K[+] to Na[+] permeability ratio and its stability over time determine the inhibition to activation transition, which limits their utility for silencing neural circuits. Among tested variants, the KCR1-C29D mutant shows a relatively high and the most stable K[+] to Na[+] permeability ratio during illumination. While other KCR variants often evoke excitatory responses, KCR1-C29D consistently provides robust in vivo inhibition across cell types, illumination conditions, and species. This work addresses a key limitation of KCR optogenetics and establishes KCR1-C29D as a superior and reliable inhibitory tool. These findings highlight the stability of ion selectivity as a design criterion and provide guidance for the design of next generation optogenetic tools.

PMC12866730 (PMC) (EuropePMC)