Curated Optogenetic Publication Database

Abstract: Optogenetic approaches facilitate the study of signaling and metabolic pathways in animal cell systems. In the past 10 years, a plethora of light-regulated switches for the targeted control over the induction of gene expression, subcellular localization of proteins, membrane receptor activity, and other cellular processes have been developed and successfully implemented. However, only a few tools have been engineered toward the quantitative and spatiotemporally resolved downregulation of proteins. Here we present a protocol for reversible and rapid blue light-induced reduction of protein levels in mammalian cells. By implementing a dual-regulated optogenetic switch (Blue-OFF), both repression of gene expression and degradation of the target protein are triggered simultaneously. We apply this system for the blue light-mediated control of programmed cell death. HEK293T cells are transfected with the proapoptotic proteins PUMA and BID integrated into the Blue-OFF system. Overexpression of these proteins leads to programmed cell death, which can be prevented by irradiation with blue light. This experimental approach is very straightforward, requires just simple hardware, and therefore can be easily implemented in state-of-the-art equipped mammalian cell culture labs. The system can be used for targeted cell signaling studies and biotechnological applications.

Abstract: Optogenetic switches are emerging molecular tools for studying cellular processes as they offer higher spatiotemporal and quantitative precision than classical, chemical-based switches. Light-controllable gene expression systems designed to upregulate protein expression levels meanwhile show performances superior to their chemical-based counterparts. However, systems to reduce protein levels with similar efficiency are lagging behind. Here, we present a novel two-component, blue light-responsive optogenetic OFF switch (‘Blue-OFF’), which enables a rapid and quantitative down-regulation of a protein upon illumination. Blue-OFF combines the first light responsive repressor KRAB-EL222 with the protein degradation module B-LID (blue light-inducible degradation domain) to simultaneously control gene expression and protein stability with a single wavelength. Blue-OFF thus outperforms current optogenetic systems for controlling protein levels. The system is described by a mathematical model which aids in the choice of experimental conditions such as light intensity and illumination regime to obtain the desired outcome. This approach represents an advancement of dual-controlled optogenetic systems in which multiple photosensory modules operate synergistically. As exemplified here for the control of apoptosis in mammalian cell culture, the approach opens up novel perspectives in fundamental research and applications such as tissue engineering.