A neuropsin-based optogenetic tool for precise control of G_q signaling

G_q-coupled receptors regulate numerous physiological processes by activating enzymes and inducing intracellular Ca²⁺ signals. There is a strong need for an optogenetic tool that enables powerful experimental control over G_q signaling. Here, we present chicken opsin 5 (cOpn5) as the long sought-after, single-component optogenetic tool that mediates ultra-sensitive optical control of intracellular G_q signaling with high temporal and spatial resolution. Expressing cOpn5 in HEK 293T cells and primary mouse astrocytes enables blue light-triggered, G_q-dependent Ca²⁺ release from intracellular stores and protein kinase C activation. Strong Ca²⁺ transients were evoked by brief light pulses of merely 10 ms duration and at 3 orders lower light intensity of that for common optogenetic tools. Photostimulation of cOpn5-expressing cells at the subcellular and single-cell levels generated fast intracellular Ca²⁺ transition, thus demonstrating the high spatial precision of cOpn5 optogenetics. The cOpn5-mediated optogenetics could also be applied to activate neurons and control animal behavior in a circuit-dependent manner. cOpn5 optogenetics may find broad applications in studying the mechanisms and functional relevance of G_q signaling in both non-excitable cells and excitable cells in all major organ systems.