Optogenetic manipulation of second messengers in neurons and cardiomyocytes with microbial rhodopsins and adenylyl cyclase

Even though microbial photosensitive proteins have been used for optogenetics, their use should be optimized to precisely control second messengers in vivo. We exploited GtCCR4 and KnChR, cation channelrhodopsins from algae, BeGC1, a guanylyl cyclase rhodopsin from a fungus, and photoactivated adenylyl cyclases (PACs) from cyanobacteria (OPAC) or bacteria (bPAC), to control cell functions in zebrafish. Optical activation of GtCCR4 and KnChR in the hindbrain reticulospinal V2a neurons, which are involved in locomotion, immediately induced swimming behavior, whereas activation of BeGC1 or PACs was achieved at a short latency. KnChR had the highest locomotioninducing activity of all the channelrhodopsins examined. Activation of GtCCR4 and KnChR in cardiomyocytes induced cardiac arrest, whereas activation of bPAC gradually induced bradycardia. KnChR activation led to an increase in intracellular Ca2+ in the heart, suggesting that depolarization caused cardiac arrest. These data suggest that these optogenetic tools can be used to reveal the roles of second messengers in various cell types in vertebrates. Impact statementWe identified efficient and useful microbial channelrhodopsin, guanylyl cyclase rhodopsin, and photoactivated adenylyl cyclase that regulate neural activity and cardiac function in zebrafish. Major subject areasNeuroscience, Cell biology Research organismZebrafish (Danio rerio)