Optical control of cellular signaling pathways using animal opsins

Currently, in various biological research fields, optical control of cellular responses is widely utilized, leading to establishing a research field named "optogenetics". Successful optogenetic studies need both state-of-art optical devices illuminating target issues with a high spatiotemporal resolution and optical control tools (typically photosensitive proteins) driving cellular reactions in a light-dependent manner. Most of optogenetic analyses have used channelrhodopsins, light-sensitive ion channels, as control tools. Alternatively, animal opsins, light-sensitive G protein-coupled receptors, can be used as tools to drive a wide variety of G protein-dependent intracellular signaling pathways. Here, I characterize molecular properties of invertebrate opsins by spectroscopic and electrophysiological techniques, and introduce them as "ON-OFF" switch of GPCR signalings. Also, I discuss potentials of the animal opsins as optogenetic tools to expand the research field.