Showing 1 - 15 of 15 results
Light control of RTK activity: from technology development to translational research.
Inhibition of receptor tyrosine kinases (RTKs) by small molecule inhibitors and monoclonal antibodies is used to treat cancer. Conversely, activation of RTKs with their ligands, including growth factors and insulin, is used to treat diabetes and neurodegeneration. However, conventional therapies that rely on injection of RTK inhibitors or activators do not provide spatiotemporal control over RTK signaling, which results in diminished efficiency and side effects. Recently, a number of optogenetic and optochemical approaches have been developed that allow RTK inhibition or activation in cells and in vivo with light. Light irradiation can control RTK signaling non-invasively, in a dosed manner, with high spatio-temporal precision, and without the side effects of conventional treatments. Here we provide an update on the current state of the art of optogenetic and optochemical RTK technologies and the prospects of their use in translational studies and therapy.
Bacterial Phytochrome as a Scaffold for Engineering of Receptor Tyrosine Kinases Controlled with Near-Infrared Light.
Optically controlled receptor tyrosine kinases (opto-RTKs) allow regulation of RTK signaling using light. Until recently, the majority of opto-RTKs were activated with blue-green light. Fusing a photosensory core module of Deinococcus radiodurans bacterial phytochrome (DrBphP-PCM) to the kinase domains of neurotrophin receptors resulted in opto-RTKs controlled with light above 650 nm. To expand this engineering approach to RTKs of other families, here we combined the DrBpP-PCM with the cytoplasmic domains of EGFR and FGFR1. The resultant Dr-EGFR and Dr-FGFR1 opto-RTKs are rapidly activated with near-infrared and inactivated with far-red light. The opto-RTKs efficiently trigger ERK1/2, PI3K/Akt, and PLCγ signaling. Absence of spectral crosstalk between the opto-RTKs and green fluorescent protein-based biosensors enables simultaneous Dr-FGFR1 activation and detection of calcium transients. Action mechanism of the DrBphP-PCM-based opto-RTKs is considered using the available RTK structures. DrBphP-PCM represents a versatile scaffold for engineering of opto-RTKs that are reversibly regulated with far-red and near-infrared light.
Optogenetic regulation of endogenous proteins.
Techniques of protein regulation, such as conditional gene expression, RNA interference, knock-in and knock-out, lack sufficient spatiotemporal accuracy, while optogenetic tools suffer from non-physiological response due to overexpression artifacts. Here we present a near-infrared light-activatable optogenetic system, which combines the specificity and orthogonality of intrabodies with the spatiotemporal precision of optogenetics. We engineer optically-controlled intrabodies to regulate genomically expressed protein targets and validate the possibility to further multiplex protein regulation via dual-wavelength optogenetic control. We apply this system to regulate cytoskeletal and enzymatic functions of two non-tagged endogenous proteins, actin and RAS GTPase, involved in complex functional networks sensitive to perturbations. The optogenetically-enhanced intrabodies allow fast and reversible regulation of both proteins, as well as simultaneous monitoring of RAS signaling with visible-light biosensors, enabling all-optical approach. Growing number of intrabodies should make their incorporation into optogenetic tools the versatile technology to regulate endogenous targets.
Neurotrophin receptor tyrosine kinases regulated with near-infrared light.
Optical control over the activity of receptor tyrosine kinases (RTKs) provides an efficient way to reversibly and non-invasively map their functions. We combined catalytic domains of Trk (tropomyosin receptor kinase) family of RTKs, naturally activated by neurotrophins, with photosensory core module of DrBphP bacterial phytochrome to develop opto-kinases, termed Dr-TrkA and Dr-TrkB, reversibly switchable on and off with near-infrared and far-red light. We validated Dr-Trk ability to reversibly light-control several RTK pathways, calcium level, and demonstrated that their activation triggers canonical Trk signaling. Dr-TrkA induced apoptosis in neuroblastoma and glioblastoma, but not in other cell types. Absence of spectral crosstalk between Dr-Trks and blue-light-activatable LOV-domain-based translocation system enabled intracellular targeting of Dr-TrkA independently of its activation, additionally modulating Trk signaling. Dr-Trks have several superior characteristics that make them the opto-kinases of choice for regulation of RTK signaling: high activation range, fast and reversible photoswitching, and multiplexing with visible-light-controllable optogenetic tools.
Smallest near-infrared fluorescent protein evolved from cyanobacteriochrome as versatile tag for spectral multiplexing.
From a single domain of cyanobacteriochrome (CBCR) we developed a near-infrared (NIR) fluorescent protein (FP), termed miRFP670nano, with excitation at 645 nm and emission at 670 nm. This is the first CBCR-derived NIR FP evolved to efficiently bind endogenous biliverdin chromophore and brightly fluoresce in mammalian cells. miRFP670nano is a monomer with molecular weight of 17 kDa that is 2-fold smaller than bacterial phytochrome (BphP)-based NIR FPs and 1.6-fold smaller than GFP-like FPs. Crystal structure of the CBCR-based NIR FP with biliverdin reveals a molecular basis of its spectral and biochemical properties. Unlike BphP-derived NIR FPs, miRFP670nano is highly stable to denaturation and degradation and can be used as an internal protein tag. miRFP670nano is an effective FRET donor for red-shifted NIR FPs, enabling engineering NIR FRET biosensors spectrally compatible with GFP-like FPs and blue-green optogenetic tools. miRFP670nano unlocks a new source of diverse CBCR templates for NIR FPs.
Near-Infrared Fluorescent Proteins: Multiplexing and Optogenetics across Scales.
Since mammalian tissue is relatively transparent to near-infrared (NIR) light, NIR fluorescent proteins (FPs) engineered from bacterial phytochromes have become widely used probes for non-invasive in vivo imaging. Recently, these genetically encoded NIR probes have been substantially improved, enabling imaging experiments that were not possible previously. Here, we discuss the use of monomeric NIR FPs and NIR biosensors for multiplexed imaging with common visible GFP-based probes and blue light-activatable optogenetic tools. These NIR probes are suitable for visualization of functional activities from molecular to organismal levels. In combination with advanced imaging techniques, such as two-photon microscopy with adaptive optics, photoacoustic tomography and its recent modification reversibly switchable photoacoustic computed tomography, NIR probes allow subcellular resolution at millimeter depths.
Near-infrared light-controlled systems for gene transcription regulation, protein targeting and spectral multiplexing.
Near-infrared (NIR, 740-780 nm) optogenetic systems are well-suited to spectral multiplexing with blue-light-controlled tools. Here, we present two protocols, one for regulation of gene transcription and another for control of protein localization, that use a NIR-responsive bacterial phytochrome BphP1-QPAS1 optogenetic pair. In the first protocol, cells are transfected with the optogenetic constructs for independently controlling gene transcription by NIR (BphP1-QPAS1) and blue (LightOn) light. The NIR and blue-light-controlled gene transcription systems show minimal spectral crosstalk and induce a 35- to 40-fold increase in reporter gene expression. In the second protocol, the BphP1-QPAS1 pair is combined with a light-oxygen-voltage-sensing (LOV) domain-based construct into a single optogenetic tool, termed iRIS. This dual-light-controllable protein localization tool allows tridirectional protein translocation among the cytoplasm, nucleus and plasma membrane. Both procedures can be performed within 3-5 d. Use of NIR light-controlled optogenetic systems should advance basic and biomedical research.
Direct multiplex imaging and optogenetics of Rho GTPases enabled by near-infrared FRET.
Direct visualization and light control of several cellular processes is a challenge, owing to the spectral overlap of available genetically encoded probes. Here we report the most red-shifted monomeric near-infrared (NIR) fluorescent protein, miRFP720, and the fully NIR Förster resonance energy transfer (FRET) pair miRFP670-miRFP720, which together enabled design of biosensors compatible with CFP-YFP imaging and blue-green optogenetic tools. We developed a NIR biosensor for Rac1 GTPase and demonstrated its use in multiplexed imaging and light control of Rho GTPase signaling pathways. Specifically, we combined the Rac1 biosensor with CFP-YFP FRET biosensors for RhoA and for Rac1-GDI binding, and concurrently used the LOV-TRAP tool for upstream Rac1 activation. We directly observed and quantified antagonism between RhoA and Rac1 dependent on the RhoA-downstream effector ROCK; showed that Rac1 activity and GDI binding closely depend on the spatiotemporal coordination between these two molecules; and simultaneously observed Rac1 activity during optogenetic manipulation of Rac1.
Optogenetically controlled protein kinases for regulation of cellular signaling.
Protein kinases are involved in the regulation of many cellular processes including cell differentiation, survival, migration, axon guidance and neuronal plasticity. A growing set of optogenetic tools, termed opto-kinases, allows activation and inhibition of different protein kinases with light. The optogenetic regulation enables fast, reversible and non-invasive manipulation of protein kinase activities, complementing traditional methods, such as treatment with growth factors, protein kinase inhibitors or chemical dimerizers. In this review, we summarize the properties of the existing optogenetic tools for controlling tyrosine kinases and serine-threonine kinases. We discuss how the opto-kinases can be applied for studies of spatial and temporal aspects of protein kinase signaling in cells and organisms. We compare approaches for chemical and optogenetic regulation of protein kinase activity and present guidelines for selection of opto-kinases and equipment to control them with light. We also describe strategies to engineer novel opto-kinases on the basis of various photoreceptors.
Near-infrared light-controlled gene expression and protein targeting in neurons and non-neuronal cells.
Near-infrared (NIR) light-inducible binding of bacterial phytochrome BphP1 to its engineered partner QPAS1 is used for optical protein regulation in mammalian cells. However, there are no data on the application of the BphP1-QPAS1 pair in cells derived from various mammalian tissues. Here, we tested functionality of two BphP1-QPAS1-based optogenetic tools, such as an NIR and blue light-sensing system for control of protein localization (iRIS) and an NIR light-sensing system for transcription activation (TA), in several cell types including cortical neurons. We found that the performance of these optogenetic tools often rely on physiological properties of a specific cell type, such as nuclear transport, which may limit applicability of blue light-sensitive component of iRIS. In contrast, the NIR-light-sensing part of iRIS performed well in all tested cell types. The TA system showed the best performance in HeLa, U-2 OS and HEK-293 cells. Small size of the QPAS1 component allows designing AAV viral particles, which were applied to deliver the TA system to neurons.
Near-Infrared Fluorescent Proteins, Biosensors, and Optogenetic Tools Engineered from Phytochromes.
Phytochrome photoreceptors absorb far-red and near-infrared (NIR) light and regulate light responses in plants, fungi, and bacteria. Their multidomain structure and autocatalytic incorporation of linear tetrapyrrole chromophores make phytochromes attractive molecular templates for the development of light-sensing probes. A subclass of bacterial phytochromes (BphPs) utilizes heme-derived biliverdin tetrapyrrole, which is ubiquitous in mammalian tissues, as a chromophore. Because biliverdin possesses the largest electron-conjugated chromophore system among linear tetrapyrroles, BphPs exhibit the most NIR-shifted spectra that reside within the NIR tissue transparency window. Here we analyze phytochrome structure and photochemistry to describe the molecular mechanisms by which they function. We then present strategies to engineer BphP-based NIR fluorescent proteins and review their properties and applications in modern imaging technologies. We next summarize designs of reporters and biosensors and describe their use in the detection of protein-protein interactions, proteolytic activities, and posttranslational modifications. Finally, we provide an overview of optogenetic tools developed from phytochromes and describe their use in light-controlled cell signaling, gene expression, and protein localization. Our review provides guidelines for the selection of NIR probes and tools for noninvasive imaging, sensing, and light-manipulation applications, specifically focusing on probes developed for use in mammalian cells and in vivo.
Near-infrared optogenetic pair for protein regulation and spectral multiplexing.
Multifunctional optogenetic systems are in high demand for use in basic and biomedical research. Near-infrared-light-inducible binding of bacterial phytochrome BphP1 to its natural PpsR2 partner is beneficial for simultaneous use with blue-light-activatable tools. However, applications of the BphP1-PpsR2 pair are limited by the large size, multidomain structure and oligomeric behavior of PpsR2. Here, we engineered a single-domain BphP1 binding partner, Q-PAS1, which is three-fold smaller and lacks oligomerization. We exploited a helix-PAS fold of Q-PAS1 to develop several near-infrared-light-controllable transcription regulation systems, enabling either 40-fold activation or inhibition. The light-induced BphP1-Q-PAS1 interaction allowed modification of the chromatin epigenetic state. Multiplexing the BphP1-Q-PAS1 pair with a blue-light-activatable LOV-domain-based system demonstrated their negligible spectral crosstalk. By integrating the Q-PAS1 and LOV domains in a single optogenetic tool, we achieved tridirectional protein targeting, independently controlled by near-infrared and blue light, thus demonstrating the superiority of Q-PAS1 for spectral multiplexing and engineering of multicomponent systems.
A bacterial phytochrome-based optogenetic system controllable with near-infrared light.
Light-mediated control of protein-protein interactions to regulate cellular pathways is an important application of optogenetics. Here, we report an optogenetic system based on the reversible light-induced binding between the bacterial phytochrome BphP1 and its natural partner PpsR2 from Rhodopseudomonas palustris bacteria. We extensively characterized the BphP1-PpsR2 interaction both in vitro and in mammalian cells and then used this interaction to translocate target proteins to specific cellular compartments, such as the plasma membrane and the nucleus. We showed light-inducible control of cell morphology that resulted in a substantial increase of the cell area. We demonstrated light-dependent gene expression with 40-fold contrast in cultured cells, 32-fold in subcutaneous mouse tissue, and 5.7-fold in deep tissues in mice. Characteristics of the BphP1-PpsR2 optogenetic system include its sensitivity to 740- to 780-nm near-infrared light, its ability to utilize an endogenous biliverdin chromophore in eukaryotes (including mammals), and its spectral compatibility with blue-light-driven optogenetic systems.
Natural photoreceptors as a source of fluorescent proteins, biosensors, and optogenetic tools.
Genetically encoded optical tools have revolutionized modern biology by allowing detection and control of biological processes with exceptional spatiotemporal precision and sensitivity. Natural photoreceptors provide researchers with a vast source of molecular templates for engineering of fluorescent proteins, biosensors, and optogenetic tools. Here, we give a brief overview of natural photoreceptors and their mechanisms of action. We then discuss fluorescent proteins and biosensors developed from light-oxygen-voltage-sensing (LOV) domains and phytochromes, as well as their properties and applications. These fluorescent tools possess unique characteristics not achievable with green fluorescent protein-like probes, including near-infrared fluorescence, independence of oxygen, small size, and photosensitizer activity. We next provide an overview of available optogenetic tools of various origins, such as LOV and BLUF (blue-light-utilizing flavin adenine dinucleotide) domains, cryptochromes, and phytochromes, enabling control of versatile cellular processes. We analyze the principles of their function and practical requirements for use. We focus mainly on optical tools with demonstrated use beyond bacteria, with a specific emphasis on their applications in mammalian cells.
Engineering of bacterial phytochromes for near-infrared imaging, sensing, and light-control in mammals.
Near-infrared light is favourable for imaging in mammalian tissues due to low absorbance of hemoglobin, melanin, and water. Therefore, fluorescent proteins, biosensors and optogenetic constructs for optimal imaging, optical readout and light manipulation in mammals should have fluorescence and action spectra within the near-infrared window. Interestingly, natural Bacterial Phytochrome Photoreceptors (BphPs) utilize the low molecular weight biliverdin, found in most mammalian tissues, as a photoreactive chromophore. Due to their near-infrared absorbance BphPs are preferred templates for designing optical molecular tools for applications in mammals. Moreover, BphPs spectrally complement existing genetically-encoded probes. Several BphPs were already developed into the near-infrared fluorescent variants. Based on the analysis of the photochemistry and structure of BphPs we suggest a variety of possible BphP-based fluorescent proteins, biosensors, and optogenetic tools. Putative design strategies and experimental considerations for such probes are discussed.