A self-inactivating invertebrate opsin optically drives biased signaling toward G & beta;& gamma;-dependent ion channel modulation

Animal opsins, light-sensitive G protein-coupled receptors, have been used for opto-genetic tools to control G protein-dependent signaling pathways. Upon G protein activation, the G & alpha; and G & beta;& gamma; subunits drive different intracellular signaling pathways, leading to complex cellular responses. For some purposes, G & alpha;- and G & beta;& gamma;-dependent signaling needs to be separately modulated, but these responses are simultaneously evoked due to the 1:1 stoichiometry of G & alpha; and G & beta;& gamma; Nevertheless, we show tempo-ral activation of G protein using a self-inactivating invertebrate opsin, Platynereis c-opsin1, drives biased signaling for G & beta;& gamma;-dependent GIRK channel activation in a light-dependent manner by utilizing the kinetic difference between G & beta;& gamma;-dependent and G & alpha;-dependent responses. The opsin-induced transient Gi/o activation pref-erentially causes activation of the kinetically fast G & beta;& gamma;-dependent GIRK channels rather than slower Gi/o & alpha;-dependent adenylyl cyclase inhibition. Although simi-lar G & beta;& gamma;-biased signaling properties were observed in a self-inactivating vertebrate visual pigment, Platynereis c-opsin1 requires fewer retinal molecules to evoke cellular responses. Furthermore, the G & beta;& gamma;-biased signaling properties of Platynereis c-opsin1 are enhanced by genetically fusing with RGS8 protein, which accelerates G protein inactivation. The self-inactivating invertebrate opsin and its RGS8-fusion protein can function as optical control tools biased for G & beta;& gamma;-dependent ion channel modulation.