Animal opsins are light-sensitive G protein coupled receptors (GPCRs). Thousands of the opsins have been identified from a wide variety of animals and they are phylogenetically divided into several groups. The members belonging to each group have unique molecular properties and the properties could potentially contribute to GPCR optogenetics, namely, optical control of GPCR functions. I discuss optogenetic potentials of animal opsins from the viewpoints of their molecular properties. Most animal opsins require an 11-cis retinal as a chromophore, but the amount of the 11-cis form in extraocular tissues is extremely limited. Therefore, the demand for the 11-cis form has been often pointed out as a disadvantage of animal opsins in optogenetic application. Bistable opsins, which exhibit an interconvertible photoreaction between two stable states, dark-inactive and light-active states, do not release chromophore retinals and therefore, they potentially overcome the disadvantage in optogenetics [1, 2]. In my presentation, I discuss optogenetic potentials about some bistable opsins such as parapinopsin, a typical bistable opsin involved in the pineal wavelength discrimination [1,3], a mutant protein of the jumping spider peropsin that binds to all-trans retinal in the dark and light-dependently stops activating G protein [4] and some opsins including jumping spider Rh1 for activating Gq-mediated signal transduction cascades.
[1] Koyanagi et al., Proc Natl. Acad. Sci. USA 119, e2204341119, 2022; [2] Hagio et al., eLife 12, e83974, 2023; [3] Wada et al., Proc Natl. Acad. Sci. USA 115, 11310-113115, 2018; [4] Nagata, et al., Sci. Rep. 8, 3535, 2018