Curated Optogenetic Publication Database

Abstract: Necroptosis is programmed cell death that involves active cytokine production and membrane ruptures. Whereas intracellular necroptosis has been extensively studied, intercellular propagation of necroptosis is much less understood. Pharmacological induction of necroptosis cannot delineate whether a necroptotic cell can propagate the death signal to its neighbor because of the confounding effect from the exogenously administrated death-inducers. To address this challenge, we develop an optogenetic system to enable ligand-free, optical induction of necroptosis at the single-cell level. This system, termed Light-activatable Receptor-Interacting Protein Kinase 3 or La-RIPK3, utilizes CRY2olig, a variant of the photoactivatable protein cryptochrome, to induce oligomerization of RIPK3 under blue light stimulation. Kinetic analysis La-RIPK3-activated cells shows that cytokine production and membrane rupture follows distinct kinetics. Moreover, membrane rupture requires a higher threshold of RIPK3 kinase activity than cytokine production. Intriguingly, intercellular propagation of necroptosis requires at least two proximal necroptotic cells, and a single necroptotic cell rarely induces such propagation. These results imply that RIPK3 acts as a gatekeeper to define the threshold of distinct functional outcomes of intracellular and intercellular necroptosis. Such a thresholding mechanism could allow cells to make informed decisions by evaluating the severity of environmental stress when walking a tightrope between committing an immunogenic suicidal fate and maintaining membrane integrity. This study highlights the role of RIPK3-containing necrosomes in regulating intracellular and intercellular necroptosis and offers an optimized optogenetic tool for investigating RIPK3-dependent necroptotic pathways.

Abstract: Optogenetics tools for precise temporal and spatial control of protein abundance are valuable in studying diverse complex biological processes. In the present study, we engineer a monomeric tag of stabilization upon light induction (SULI) for yeast and zebrafish based on a single light-oxygen-voltage domain from Neurospora crassa. Proteins of interest fused with SULI are stable upon light illumination but are readily degraded after transfer to dark conditions. SULI shows a high dynamic range and a high tolerance to fusion at different positions of the target protein. Further studies reveal that SULI-mediated degradation occurs through a lysine ubiquitination-independent proteasome pathway. We demonstrate the usefulness of SULI in controlling the cell cycle in yeast and regulating protein stability in zebrafish, respectively. Overall, our data indicate that SULI is a simple and robust tool to quantitatively and spatiotemporally modulate protein levels for biotechnological or biomedical applications.

Abstract: Sensory photoreceptors enable organisms to adjust their physiology, behavior, and development in response to light, generally with spatiotemporal acuity and reversibility. These traits underlie the use of photoreceptors as genetically encoded actuators to alter by light the state and properties of heterologous organisms. Subsumed as optogenetics, pertinent approaches enable regulating diverse cellular processes, not least gene expression. Here, we controlled the widely used Tet repressor by coupling to light-oxygen-voltage (LOV) modules that either homodimerize or dissociate under blue light. Repression could thus be elevated or relieved, and consequently protein expression was modulated by light. Strikingly, the homodimeric RsLOV module from Rhodobacter sphaeroides not only dissociated under light but intrinsically reacted to temperature. The limited light responses of wild-type RsLOV at 37 °C were enhanced in two variants that exhibited closely similar photochemistry and structure. One variant improved the weak homodimerization affinity of 40 µM by two-fold and thus also bestowed light sensitivity on a receptor tyrosine kinase. Certain photoreceptors, exemplified by RsLOV, can evidently moonlight as temperature sensors which immediately bears on their application in optogenetics and biotechnology. Properly accounted for, the temperature sensitivity can be leveraged for the construction of signal-responsive cellular circuits.

Abstract: In nature, photoreceptor proteins undergo molecular responses to light, that exhibit supreme fidelity in time and space and generally occur under mild reaction conditions. To unlock these traits for material science, the light‐induced homodimerization of light‐oxygen‐voltage (LOV) photoreceptors is leveraged to control the assembly of gold nanoparticles. Conjugated to genetically encodable LOV proteins, the nanoparticles are monodispersed in darkness but rapidly assemble into large aggregates upon blue‐light exposure. The work establishes a new modality for reaction control in macromolecular chemistry and thus augurs enhanced precision in space and time in diverse applications of gold nanoparticles.

Abstract: Control of cellular events by optogenetic tools is a powerful approach to manipulate cellular functions in a minimally invasive manner. A common problem posed by the application of optogenetic tools is to tune the activity range to be physiologically relevant. Here, we characterized a photoreceptor of the light-oxygen-voltage domain family of Phaeodactylum tricornutum aureochrome 1a (AuLOV) as a tool for increasing protein stability under blue light conditions in budding yeast. Structural studies of AuLOVwt, the variants AuLOVM254 and AuLOVW349 revealed alternative dimer association modes for the dark state, which differ from previously reported AuLOV dark state structures. Rational design of AuLOV-dimer interface mutations resulted in an optimized optogenetic tool that we fused to the photoactivatable adenylyl cyclase from Beggiatoa sp.. This synergistic light-regulation approach using two photoreceptors resulted in an optimized, photoactivatable adenylyl cyclase with a cyclic AMP production activity that matches the physiological range of Saccharomyces cerevisiae. Overall, we enlarged the optogenetic toolbox for yeast and demonstrated the importance of fine-tuning the optogenetic tool activity for successful application in cells.