Spatiotemporal control of cell signalling using a light-switchable protein interaction

Abstract

Green fluorescent protein and other genetically encodable optical reporters have revolutionized the study of cell function. Now Levskaya et al. describe a technology that adds a new dimension to cell biology by incorporating light-activated proteins from plants into mammalian cell signalling systems, leading to cells whose morphology and behaviour can be controlled by light. The system uses a reversible protein–protein interaction module from the Arabidopsis phytochrome-signalling network to reversibly translocate activators of the Rho-family GTPases to the plasma membrane. In principle, this advance makes it possible to design a variety of light-programmable reagents for a new generation of perturbative cell biology experiments. The use of light to precisely control cellular behaviour is a challenge that has only recently begun to be addressed. Here, a genetically encoded light-control system is demonstrated in mammalian cells. Based on a reversible protein–protein interaction from the phytochrome signalling network of Arabidopsis thaliana, the system is used to reversibly translocate activators of the Rho-family GTPases to the plasma membrane with high temporal and spatial resolution. Genetically encodable optical reporters, such as green fluorescent protein, have revolutionized the observation and measurement of cellular states. However, the inverse challenge of using light to control precisely cellular behaviour has only recently begun to be addressed; semi-synthetic chromophore-tethered receptors1 and naturally occurring channel rhodopsins have been used to perturb directly neuronal networks2,3. The difficulty of engineering light-sensitive proteins remains a significant impediment to the optical control of most cell-biological processes. Here we demonstrate the use of a new genetically encoded light-control system based on an optimized, reversible protein–protein interaction from the phytochrome signalling network of Arabidopsis thaliana. Because protein–protein interactions are one of the most general currencies of cellular information, this system can, in principle, be generically used to control diverse functions. Here we show that this system can be used to translocate target proteins precisely and reversibly to the membrane with micrometre spatial resolution and at the second timescale. We show that light-gated translocation of the upstream activators of Rho-family GTPases, which control the actin cytoskeleton, can be used to precisely reshape and direct the cell morphology of mammalian cells. The light-gated protein–protein interaction that has been optimized here should be useful for the design of diverse light-programmable reagents, potentially enabling a new generation of perturbative, quantitative experiments in cell biology.