Showing 1 - 25 of 93 results
Engineered BRET-Based Biologic Light Sources Enable Spatiotemporal Control over Diverse Optogenetic Systems.
Light-inducible optogenetic systems offer precise spatiotemporal control over a myriad of biologic processes. Unfortunately, current systems are inherently limited by their dependence on external light sources for their activation. Further, the utility of laser/LED-based illumination strategies are often constrained by the need for invasive surgical procedures to deliver such devices and local heat production, photobleaching and phototoxicity that compromises cell and tissue viability. To overcome these limitations, we developed a novel BRET-activated optogenetics (BEACON) system that employs biologic light to control optogenetic tools. BEACON is driven by self-illuminating bioluminescent-fluorescent proteins that generate "spectrally tuned" biologic light via bioluminescence resonance energy transfer (BRET). Notably, BEACON robustly activates a variety of commonly used optogenetic systems in a spatially restricted fashion, and at physiologically relevant time scales, to levels that are achieved by conventional laser/LED light sources.
A time-dependent role for the transcription factor CREB in neuronal allocation to an engram underlying a fear memory revealed using a novel in vivo optogenetic tool to modulate CREB function.
The internal representation of an experience is thought to be encoded by long-lasting physical changes to the brain ("engrams") (Josselyn et al. Nat Rev Neurosci 16:521-534, 2015; Josselyn et al. J Neurosci 37:4647-4657, 2017; Schacter. 2001; Tonegawa et al. Neuron 87:918-931, 2015). Previously, we (Han et al. Science 316:457-460, 2007) and others (Zhou et al. Nat Neurosci 12:1438-1443, 2009) showed within the lateral amygdala (LA), a region critical for auditory conditioned fear, eligible neurons compete against one other for allocation to an engram. Neurons with relatively higher function of the transcription factor CREB were more likely to be allocated to the engram. In these studies, though, CREB function was artificially increased for several days before training. Precisely when increased CREB function is important for allocation remains an unanswered question. Here, we took advantage of a novel optogenetic tool (opto-DN-CREB) (Ali et al. Chem Biol 22:1531-1539, 2015) to gain spatial and temporal control of CREB function in freely behaving mice. We found increasing CREB function in a small, random population of LA principal neurons in the minutes-hours, but not 24 h, before training was sufficient to enhance memory, likely because these neurons were preferentially allocated to the underlying engram. However, similarly increasing CREB activity in a small population of random LA neurons immediately after training disrupted subsequent memory retrieval, likely by disrupting the precise spatial and temporal patterns of offline post-training neuronal activity and/or function required for consolidation. These findings reveal the importance of the timing of CREB activity in regulating allocation and subsequent memory retrieval, and further, highlight the potential of optogenetic approaches to control protein function with temporal specificity in behaving animals.
Optogenetic control of cofilin and αTAT in living cells using Z-lock.
Here we introduce Z-lock, an optogenetic approach for reversible, light-controlled steric inhibition of protein active sites. The light oxygen voltage (LOV) domain and Zdk, a small protein that binds LOV selectively in the dark, are appended to the protein of interest where they sterically block the active site. Irradiation causes LOV to change conformation and release Zdk, exposing the active site. Computer-assisted protein design was used to optimize linkers and Zdk-LOV affinity, for both effective binding in the dark, and effective light-induced release of the intramolecular interaction. Z-lock cofilin was shown to have actin severing ability in vitro, and in living cancer cells it produced protrusions and invadopodia. An active fragment of the tubulin acetylase αTAT was similarly modified and shown to acetylate tubulin on irradiation.
Repurposing protein degradation for optogenetic modulation of protein activities.
Non-neuronal optogenetic approaches empower precise regulation of protein dynamics in live cells but often require target-specific protein engineering. To address this challenge, we developed a generalizable light-modulated protein stabilization system (GLIMPSe) to control intracellular protein level independent of its functionality. We applied GLIMPSe to control two distinct classes of proteins: mitogen-activated protein kinase phosphatase 3 (MKP3), a negative regulator of the extracellu-lar signal-regulated kinase (ERK) pathway, as well as a constitutively active form of MEK (CA MEK), a positive regulator of the same pathway. Kinetics study showed that light-induced protein stabilization could be achieved within 30 minutes of blue light stimulation. GLIMPSe enables target-independent optogenetic control of protein activities and therefore minimizes the systematic variation embedded within different photoactivatable proteins. Overall, GLIMPSe promises to achieve light-mediated post-translational stabilization of a wide array of target proteins in live cells.
An AND-Gated Drug and Photoactivatable Cre-loxP System for Spatiotemporal Control in Cell-Based Therapeutics.
While engineered chimeric antigen receptor (CAR) T cells have shown promise in detecting and eradicating cancer cells within patients, it remains difficult to identify a set of truly cancer-specific CAR-targeting cell surface antigens to prevent potentially fatal on-target off-tumor toxicity against other healthy tissues within the body. To help address this issue, we present a novel tamoxifen-gated photoactivatable split-Cre recombinase optogenetic system, called TamPA-Cre, that features high spatiotemporal control to limit CAR T cell activity to the tumor site. We created and optimized a novel genetic AND gate switch by integrating the features of tamoxifen-dependent nuclear localization and blue-light-inducible heterodimerization of Magnet protein domains (nMag, pMag) into split Cre recombinase. By fusing the cytosol-localizing mutant estrogen receptor ligand binding domain (ERT2) to the N-terminal half of split Cre(2-59aa)-nMag, the TamPA-Cre protein ERT2-CreN-nMag is physically separated from its nuclear-localized binding partner, NLS-pMag-CreC(60-343aa). Without tamoxifen to drive nuclear localization of ERT2-CreN-nMag, the typically high background of the photoactivation system was significantly suppressed. Upon blue light stimulation following tamoxifen treatment, the TamPA-Cre system exhibits sensitivity to low intensity, short durations of blue light exposure to induce robust Cre-loxP recombination efficiency. We finally demonstrate that this TamPA-Cre system can be applied to specifically control localized CAR expression and subsequently T cell activation. As such, we posit that CAR T cell activity can be confined to a solid tumor site by applying an external stimulus, with high precision of control in both space and time, such as light.
Imaging of Morphological and Biochemical Hallmarks of Apoptosis with Optimized Optogenetic Actuators.
The creation of optogenetic switches for specific activation of cell-death pathways can provide insights into apoptosis and could also form a basis for non-invasive, next-generation therapeutic strategies. Previous work has demonstrated that cryptochrome 2 (Cry2)/CIB, a blue light–activated protein–protein dimerization module from the plant Arabidopsis thaliana together with BCL2-associated X apoptosis regulator (BAX), an outer mitochondrial membrane (OMM)-targeting pro-apoptotic protein, can be used for light-mediated initiation of mitochondrial outer-membrane permeabilization (MOMP) and downstream apoptosis. In this work, we further developed the original light-activated Cry2–BAX system (henceforth referred to as OptoBAX) by improving the photophysical properties and light-independent interactions of this optogenetic switch. The resulting optogenetic constructs significantly reduced the frequency of light exposure required for the membrane permeabilization activation and also decreased dark-state cytotoxicity. We used OptoBAX in a series of experiments in Neuro-2a and HEK293T cells to measure the timing of the dramatic morphological and biochemical changes occurring in cells after light-induced MOMP. In these experiments, we used OptoBAX in tandem with fluorescent reporters for imaging key events in early apoptosis, including membrane inversion, caspase cleavage, and actin redistribution. We then used these data to construct a timeline of biochemical and morphological events in early apoptosis, demonstrating a direct link between MOMP-induced redistribution of actin and apoptosis progression. In summary, we have created a next-generation Cry2/CIB–BAX system requiring less frequent light stimulation and established a timeline of critical apoptotic events, providing detailed insights into key steps in early apoptosis.
Optogenetic control of protein binding using light-switchable nanobodies.
A growing number of optogenetic tools have been developed to control binding between two engineered protein domains. In contrast, relatively few tools confer light-switchable binding to a generic target protein of interest. Such a capability would offer substantial advantages, enabling photoswitchable binding to endogenous target proteins in vivo or light-based protein purification in vitro. Here, we report the development of opto-nanobodies (OptoNBs), a versatile class of chimeric photoswitchable proteins whose binding to proteins of interest can be enhanced or inhibited upon blue light illumination. We find that OptoNBs are suitable for a range of applications: modulating intracellular protein localization and signaling pathway activity and controlling target protein binding to surfaces and in protein separation columns. This work represents a first step towards programmable photoswitchable regulation of untagged, endogenous target proteins.
A split CRISPR-Cpf1 platform for inducible genome editing and gene activation.
The CRISPR-Cpf1 endonuclease has recently been demonstrated as a powerful tool to manipulate targeted gene sequences. Here, we performed an extensive screening of split Cpf1 fragments and identified a pair that, combined with inducible dimerization domains, enables chemical- and light-inducible genome editing in human cells. We also identified another split Cpf1 pair that is spontaneously activated. The newly generated amino and carboxyl termini of the spontaneously activated split Cpf1 can be repurposed as de novo fusion sites of artificial effector domains. Based on this finding, we generated an improved split dCpf1 activator, which has the potential to activate endogenous genes more efficiently than a previously established dCas9 activator. Finally, we showed that the split dCpf1 activator can efficiently activate target genes in mice. These results demonstrate that the present split Cpf1 provides an efficient and sophisticated genome manipulation in the fields of basic research and biotechnological applications.
Compartmentalized cAMP Generation by Engineered Photoactivated Adenylyl Cyclases.
Because small-molecule activators of adenylyl cyclases (AC) affect ACs cell-wide, it is challenging to explore the signaling consequences of AC activity emanating from specific intracellular compartments. We explored this issue using a series of engineered, optogenetic, spatially restricted, photoactivable adenylyl cyclases (PACs) positioned at the plasma membrane (PM), the outer mitochondrial membrane (OMM), and the nucleus (Nu). The biochemical consequences of brief photostimulation of PAC is primarily limited to the intracellular site occupied by the PAC. By contrast, sustained photostimulation results in distal cAMP signaling. Prolonged cAMP generation at the OMM profoundly stimulates nuclear protein kinase (PKA) activity. We have found that phosphodiesterases 3 (OMM and PM) and 4 (PM) modulate proximal (local) cAMP-triggered activity, whereas phosphodiesterase 4 regulates distal cAMP activity as well as the migration of PKA's catalytic subunit into the nucleus.
Achieving tight control of a photoactivatable Cre recombinase gene switch: new design strategies and functional characterization in mammalian cells and rodent.
A common mechanism for inducibly controlling protein function relies on reconstitution of split protein fragments using chemical or light-induced dimerization domains. A protein is split into fragments that are inactive on their own, but can be reconstituted after dimerization. As many split proteins retain affinity for their complementary half, maintaining low activity in the absence of an inducer remains a challenge. Here, we systematically explore methods to achieve tight regulation of inducible proteins that are effective despite variation in protein expression level. We characterize a previously developed split Cre recombinase (PA-Cre2.0) that is reconstituted upon light-induced CRY2-CIB1 dimerization, in cultured cells and in vivo in rodent brain. In culture, PA-Cre2.0 shows low background and high induced activity over a wide range of expression levels, while in vivo the system also shows low background and sensitive response to brief light inputs. The consistent activity stems from fragment compartmentalization that shifts localization toward the cytosol. Extending this work, we exploit nuclear compartmentalization to generate light-and-chemical regulated versions of Cre recombinase. This work demonstrates in vivo functionality of PA-Cre2.0, describes new approaches to achieve tight inducible control of Cre DNA recombinase, and provides general guidelines for further engineering and application of split protein fragments.
High-throughput multicolor optogenetics in microwell plates.
Optogenetic probes can be powerful tools for dissecting complexity in cell biology, but there is a lack of instrumentation to exploit their potential for automated, high-information-content experiments. This protocol describes the construction and use of the optoPlate-96, a platform for high-throughput three-color optogenetics experiments that allows simultaneous manipulation of common red- and blue-light-sensitive optogenetic probes. The optoPlate-96 enables illumination of individual wells in 96-well microwell plates or in groups of wells in 384-well plates. Its design ensures that there will be no cross-illumination between microwells in 96-well plates, and an active cooling system minimizes sample heating during light-intensive experiments. This protocol details the steps to assemble, test, and use the optoPlate-96. The device can be fully assembled without specialized equipment beyond a 3D printer and a laser cutter, starting from open-source design files and commercially available components. We then describe how to perform a typical optogenetics experiment using the optoPlate-96 to stimulate adherent mammalian cells. Although optoPlate-96 experiments are compatible with any plate-based readout, we describe analysis using quantitative single-cell immunofluorescence. This workflow thus allows complex optogenetics experiments (independent control of stimulation colors, intensity, dynamics, and time points) with high-dimensional outputs at single-cell resolution. Starting from 3D-printed and laser-cut components, assembly and testing of the optoPlate-96 can be accomplished in 3-4 h, at a cost of ~$600. A full optoPlate-96 experiment with immunofluorescence analysis can be performed within ~24 h, but this estimate is variable depending on the cell type and experimental parameters.
Engineering proteins for allosteric control by light or ligands.
Control of protein activity in living cells can reveal the role of spatiotemporal dynamics in signaling circuits. Protein analogs with engineered allosteric responses can be particularly effective in the interrogation of protein signaling, as they can replace endogenous proteins with minimal perturbation of native interactions. However, it has been a challenge to identify allosteric sites in target proteins where insertion of responsive domains produces an allosteric response comparable to the activity of native proteins. Here, we describe a detailed protocol to generate genetically encoded analogs of proteins that can be allosterically controlled by either rapamycin or blue light, as well as experimental procedures to produce and test these analogs in vitro and in mammalian cell lines. We describe computational methods, based on crystal structures or homology models, to identify effective sites for insertion of either an engineered rapamycin-responsive (uniRapR) domain or the light-responsive light-oxygen-voltage 2 (LOV2) domain. The inserted domains allosterically regulate the active site, responding to rapamycin with irreversible activation, or to light with reversible inactivation at higher spatial and temporal resolution. These strategies have been successfully applied to catalytic domains of protein kinases, Rho family GTPases, and guanine exchange factors (GEFs), as well as the binding domain of a GEF Vav2. Computational tasks can be completed within a few hours, followed by 1-2 weeks of experimental validation. We provide protocols for computational design, cloning, and experimental testing of the engineered proteins, using Src tyrosine kinase, GEF Vav2, and Rho GTPase Rac1 as examples.
Accurate manipulation of optogenetic proteins with wavelength tunable femtosecond laser system.
Photoactivated proteins controlled by optogenetic tools have broad application prospects in cell biology, neuroscience, and brain science. However, due to the narrow excitation wavelength width and the inflexibility of spatiotemporal operations, conventional sources such as visible light severely limit the further application of optogenetics. In this work, a femtosecond laser-operated system based on the optogenetic application was designed to address these limitations. The interaction between the photoreceptor and its partner protein can be triggered by a wavelength-tunable femtosecond laser. The results indicated that this process can be used to accurately manipulate optogenetic proteins in cells, which met spectral flexibility (700–1040 nm) and operational flexibility in time and space (a single cell to multiple cells). To demonstrate the practical applications of this process, the apoptotic signaling pathway of cancer cells was taken as an example. We believe that this wavelength-tunable femtosecond laser system will promote the development of optogenetics, making optics and even physics more powerful tools in biology.
Optical induction of autophagy via Transcription factor EB (TFEB) reduces pathological tau in neurons.
Aggregation and accumulation of microtubule associated protein tau in neurons is major neuropathological hallmark of Alzheimer’s disease (AD) and related tauopathies. Attempts have been made to promote clearance of pathological tau (p-Tau) from neurons via autophagy. Over expression of transcription factor EB (TFEB), has shown to clear pTau from neurons via autophagy. However, sustained TFEB activation and/or autophagy can create burden on cellular bioenergetics and can be deleterious. Thus, we engineered a minimally invasive optical system that could transiently alter autophagic flux. We optimized and testedan optogenetic gene expression system derived from apreviouslyengineered bacterial transcription factor, EL222. For the first time, our group utilized this system not only to spatial-temporally control nuclear TFEB expression, we also show light-induced TFEB has the capacity to reduce p-Tau burden in AD patient-derived human iPSC-neurons. Together, these results suggest that optically-regulatable gene expression of TFEB unlocks opto-therapeutics to treat AD and other dementias.
Reversible induction of mitophagy by an optogenetic bimodular system.
Autophagy-mediated degradation of mitochondria (mitophagy) is a key process in cellular quality control. Although mitophagy impairment is involved in several patho-physiological conditions, valuable methods to induce mitophagy with low toxicity in vivo are still lacking. Herein, we describe a new optogenetic tool to stimulate mitophagy, based on light-dependent recruitment of pro-autophagy protein AMBRA1 to mitochondrial surface. Upon illumination, AMBRA1-RFP-sspB is efficiently relocated from the cytosol to mitochondria, where it reversibly mediates mito-aggresome formation and reduction of mitochondrial mass. Finally, as a proof of concept of the biomedical relevance of this method, we induced mitophagy in an in vitro model of neurotoxicity, fully preventing cell death, as well as in human T lymphocytes and in zebrafish in vivo. Given the unique features of this tool, we think it may turn out to be very useful for a wide range of both therapeutic and research applications.
Luciferase-LOV BRET enables versatile and specific transcriptional readout of cellular protein-protein interactions.
Technologies that convert transient protein-protein interactions (PPIs) into stable expression of a reporter gene are useful for genetic selections, high-throughput screening, and multiplexing with omics technologies. We previously reported SPARK (Kim et al., 2017), a transcription factor that is activated by the coincidence of blue light and a PPI. Here, we report an improved, second-generation SPARK2 that incorporates a luciferase moiety to control the light-sensitive LOV domain. SPARK2 can be temporally gated by either external light or addition of a small-molecule luciferin, which causes luciferase to open LOV via proximity-dependent BRET. Furthermore, the nested 'AND' gate design of SPARK2-in which both protease recruitment to the membrane-anchored transcription factor and LOV domain opening are regulated by the PPI of interest-yields a lower-background system and improved PPI specificity. We apply SPARK2 to high-throughput screening for GPCR agonists and for the detection of trans-cellular contacts, all with versatile transcriptional readout.
Advances in optogenetic regulation of gene expression in mammalian cells using cryptochrome 2 (CRY2).
Synthetic regulation of gene expression provides a powerful approach to reprogram molecular and cellular processes and test the function of specific genes and gene products. In the last decade, optogenetic systems that allow light-dependent gene regulation have become valuable tools, providing tight spatiotemporal control of protein levels. Here we discuss and build on recent optogenetic approaches for regulating gene expression in mammalian cells using cryptochrome 2 (CRY2), a photoreceptor protein from Arabidopsis. We provide detailed protocols for using light to manipulate activity of a CRY2-based engineered photoactivatable Cre DNA recombinase, and to induce or disrupt transcription factor function. In addition, we provide instructions and software for building an inexpensive Rasberry-Pi-based programable LED device for optogenetic experiments, delivering pulsed light with customized control of illumination duration, frequency, and intensity.
Optogenetic perturbation of the biochemical pathways that control cell behavior.
Optogenetic tools provide a level of spatial and temporal resolution needed to shed new light on dynamic intercellular processes. In this chapter we outline specific protocols for applying these tools to cell motility (optogenetic cofilin), apoptosis [optogenetic Bcl-like protein 4 (Bax)], and protein kinase-mediated signaling pathways [optogenetic cAMP-dependent protein kinase (PKA)]. The activity of these optogenetic species is regulated by the light-mediated dimerization of a cryptochrome/Cib protein pair, which controls the intracellular positioning of the protein of interest. The light induced recruitment of cofilin to the cytoskeleton is utilized for directed migration studies and filopodial dynamics. Light-triggered migration of Bax to the outer mitochondrial membrane induces cellular collapse and eventual apoptosis. Finally, the light-mediated movement of PKA to specific intracellular compartments offers the means to assess the consequences of PKA activity in a site-specific fashion via phosphoproteomic analysis.
Near-infrared light remotely up-regulate autophagy with spatiotemporal precision via upconversion optogenetic nanosystem.
In vivo noninvasively manipulating biological functions by the mediation of biosafe near infrared (NIR) light is becoming increasingly popular. For these applications, upconversion rare-earth nanomaterial holds great promise as a novel photonic element, and has been widely adopted in optogenetics. In this article, an upconversion optogenetic nanosystem that was promised to achieve autophagy up-regulation with spatiotemporal precision was designed. The implantable, wireless, recyclable, less-invasive and biocompatible system worked via two separated parts: blue light-receptor optogenetics-autophagy upregulation plasmids, for protein import; upconversion rods-encapsulated flexible capsule (UCRs-capsule), for converting tissue-penetrative NIR light into local visible blue light. Results validated that this system could achieve up-regulation of autophagy in vitro (in both HeLa and 293T cell lines) and remotely penetrate tissue (∼3.5 mm) in vivo. Since autophagy serves at a central position in intracellular signalling pathways, which is correlative with diverse pathologies, we expect that this method could establish an upconversion material-based autophagy up-regulation strategy for fundamental and clinical applications.
Noninvasive optical activation of Flp recombinase for genetic manipulation in deep mouse brain regions.
Spatiotemporal control of gene expression or labeling is a valuable strategy for identifying functions of genes within complex neural circuits. Here, we develop a highly light-sensitive and efficient photoactivatable Flp recombinase (PA-Flp) that is suitable for genetic manipulation in vivo. The highly light-sensitive property of PA-Flp is ideal for activation in deep mouse brain regions by illumination with a noninvasive light-emitting diode. In addition, PA-Flp can be extended to the Cre-lox system through a viral vector as Flp-dependent Cre expression platform, thereby activating both Flp and Cre. Finally, we demonstrate that PA-Flp-dependent, Cre-mediated Cav3.1 silencing in the medial septum increases object-exploration behavior in mice. Thus, PA-Flp is a noninvasive, highly efficient, and easy-to-use optogenetic module that offers a side-effect-free and expandable genetic manipulation tool for neuroscience research.
Optogenetic control of integrin-matrix interaction.
Optogenetic approaches have gathered momentum in precisely modulating and interrogating cellular signalling and gene expression. The use of optogenetics on the outer cell surface to interrogate how cells receive stimuli from their environment, however, has so far not reached its full potential. Here we demonstrate the development of an optogenetically regulated membrane receptor-ligand pair exemplified by the optically responsive interaction of an integrin receptor with the extracellular matrix. The system is based on an integrin engineered with a phytochrome-interacting factor domain (OptoIntegrin) and a red light-switchable phytochrome B-functionalized matrix (OptoMatrix). This optogenetic receptor-ligand pair enables light-inducible and -reversible cell-matrix interaction, as well as the controlled activation of downstream mechanosensory signalling pathways. Pioneering the application of optogenetic switches in the extracellular environment of cells, this OptoMatrix–OptoIntegrin system may serve as a blueprint for rendering matrix–receptor interactions amendable to precise control with light.
Liquid Nuclear Condensates Mechanically Sense and Restructure the Genome.
Phase transitions involving biomolecular liquids are a
fundamental mechanism underlying intracellular organization.
In the cell nucleus, liquid-liquid phase
separation of intrinsically disordered proteins (IDPs)
is implicated in assembly of the nucleolus, as well
as transcriptional clusters, and other nuclear bodies.
However, it remains unclear whether and how physical
forces associated with nucleation, growth, and
wetting of liquid condensates can directly restructure
chromatin. Here, we use CasDrop, a novel
CRISPR-Cas9-based optogenetic technology, to
show that various IDPs phase separate into liquid
condensates that mechanically exclude chromatin
as they grow and preferentially form in low-density,
largely euchromatic regions. A minimal physical
model explains how this stiffness sensitivity arises
from lower mechanical energy associated with deforming
softer genomic regions. Targeted genomic
loci can nonetheless be mechanically pulled together
through surface tension-driven coalescence. Nuclear
condensates may thus function as mechanoactive
chromatin filters, physically pulling in targeted
genomic loci while pushing out non-targeted regions
of the neighboring genome.
Engineered anti-CRISPR proteins for optogenetic control of CRISPR-Cas9.
Anti-CRISPR proteins are powerful tools for CRISPR-Cas9 regulation; the ability to precisely modulate their activity could facilitate spatiotemporally confined genome perturbations and uncover fundamental aspects of CRISPR biology. We engineered optogenetic anti-CRISPR variants comprising hybrids of AcrIIA4, a potent Streptococcus pyogenes Cas9 inhibitor, and the LOV2 photosensor from Avena sativa. Coexpression of these proteins with CRISPR-Cas9 effectors enabled light-mediated genome and epigenome editing, and revealed rapid Cas9 genome targeting in human cells.
A light-gated potassium channel for sustained neuronal inhibition.
Currently available inhibitory optogenetic tools provide short and transient silencing of neurons, but they cannot provide long-lasting inhibition because of the requirement for high light intensities. Here we present an optimized blue-light-sensitive synthetic potassium channel, BLINK2, which showed good expression in neurons in three species. The channel is activated by illumination with low doses of blue light, and in our experiments it remained active over (tens of) minutes in the dark after the illumination was stopped. This activation caused long periods of inhibition of neuronal firing in ex vivo recordings of mouse neurons and impaired motor neuron response in zebrafish in vivo. As a proof-of-concept application, we demonstrated that in a freely moving rat model of neuropathic pain, the activation of a small number of BLINK2 channels caused a long-lasting (>30 min) reduction in pain sensation.
RalB directly triggers invasion downstream Ras by mobilizing the Wave complex.
The two Ral GTPases, RalA and RalB, have crucial roles downstream Ras oncoproteins in human cancers; in particular, RalB is involved in invasion and metastasis. However, therapies targeting Ral signalling are not available yet. By a novel optogenetic approach, we found that light-controlled activation of Ral at plasma-membrane promotes the recruitment of the Wave Regulatory Complex (WRC) via its effector exocyst, with consequent induction of protrusions and invasion. We show that active Ras signals to RalB via two RalGEFs (Guanine nucleotide Exchange Factors), RGL1 and RGL2, to foster invasiveness; RalB contribution appears to be more important than that of MAPK and PI3K pathways. Moreover, on the clinical side, we uncovered a potential role of RalB in human breast cancers by determining that RalB expression at protein level increases in a manner consistent with progression toward metastasis. This work highlights the Ras-RGL1/2-RalB-exocyst-WRC axis as appealing target for novel anti-cancer strategies.