Channelrhodopsin-2 (ChR2) (ChR2)

Channelrhodopsin-2 (ChR2) is a light-gated cation channel originally identified in the green alga Chlamydomonas reinhardtii, where it serves as a sensory photoreceptor mediating phototaxis [Nagel et al., 2003, Science]. Upon exposure to blue light, the protein undergoes a conformational change that opens a transmembrane pore, allowing the influx of cations such as sodium and calcium, which leads to rapid membrane depolarization [Deisseroth, 2011, Nature Methods]. In the field of optogenetics, ChR2 is utilized as a therapeutic tool by delivering its gene into specific cells, such as retinal ganglion cells or neurons, to restore light sensitivity or control circuit activity [Sahel et al., 2021, Nature Medicine]. Its primary clinical application is in vision restoration for patients with degenerative retinal diseases like retinitis pigmentosa, where it bypasses lost photoreceptors to directly stimulate the remaining visual pathway [GenSight Biologics, 2023, Corporate Website]. The protein requires all-trans-retinal as a chromophore, which is typically available endogenously in mammalian tissues [UniProt, 2024, P93517]. While highly effective in research, therapeutic use faces challenges including the need for high-intensity light and potential immune responses to the microbial protein [Nanoscope Therapeutics, 2024, Pipeline Information]. Ongoing clinical trials are evaluating various ChR2 variants and delivery methods to improve sensitivity and safety in human patients [ClinicalTrials.gov, 2024].

Other names

Light-gated ion channelChop2ChannelrhodopsinMicrobial rhodopsinChR

Light-induced isomerization of the retinal cofactor triggers a conformational change that opens the channel pore, allowing cation influx and subsequent cellular depolarization.