Luciferin Synthesis and Pesticide Detection by Luminescence Enzymatic Cascades

D-Luciferin (D-LH₂ ), a substrate of firefly luciferase (Fluc), is important for a wide range of bioluminescence applications. This work reports a new and green method using enzymatic reactions (HELP, HadA Enzyme for Luciferin Preparation) to convert 19 phenolic derivatives to 8 D-LH₂ analogues with ≈51 % yield. The method can synthesize the novel 5'-methyl-D-LH₂ and 4',5'-dimethyl-D-LH₂ , which have never been synthesized or found in nature. 5'-Methyl-D-LH₂ emits brighter and longer wavelength light than the D-LH₂ . Using HELP, we further developed LUMOS (Luminescence Measurement of Organophosphate and Derivatives) technology for in situ detection of organophosphate pesticides (OPs) including parathion, methyl parathion, EPN, profenofos, and fenitrothion by coupling the reactions of OPs hydrolase and Fluc. The LUMOS technology can detect these OPs at parts per trillion (ppt) levels. The method can directly detect OPs in food and biological samples without requiring sample pretreatment.

A biochemiluminescent assay for rapid diagnosis of influenza

A biochemiluminescent assay of influenza diagnosis is presented. The assay diagnoses influenza based on detection of the influenza viral neuraminidase activity. An instrument designed for the assay is also reported. This assay solves the problem that current influenza virus diagnosis assays are susceptible to virus mutation. A luciferase-based complex is synthesized as biochemiluminescent substrate. The substrate is cleaved to free luciferin with presence of influenza neuraminidase in specimen. Luciferase is oxidized to oxyluciferin with luciferin as catalyzer resulting in luminescence, which is proportional to the neuraminidase activity and measured by instrument. The instrument uses a photomultiplier tube as sensor, with 24 test channels. Fine optical arrangements enable the instrument with high sensitivity and accuracy. A total of 389 clinical specimens were collected to evaluate the performance of the assay in clinical settings. This assay had a sensitivity and specificity of 95.92% (95% confidence interval 91.38-98.12%) and 97.93% (95% confidence interval 95.26-99.11%), respectively, compared to the colloidal gold assay. As a biochemiluminscence assay, this assay is advantageous in sensitivity and specificity. It does not require any washing or separation steps, which makes the instrument simple in design and easy to operate or maintenance. The assay is suitable for the rapid diagnosis of influenza virus in point-of-care settings.

Synthetic Coelenterazine Derivatives and Their Application for Bioluminescence Imaging

Bioluminescence (BL), the emission light resulting from the enzyme-catalyzed oxidative reaction, is a powerful imaging modality for monitoring biological phenomena both in vitro and in vivo. Coelenterazine (CTZ), the known widespread luciferin found in bioluminescent organisms, develops bioluminescence imaging (BLI). Here, we describe an approach to synthesize a series of novel CTZ derivatives for diversifying the toolbox of the BL substrates. Furthermore, we exemplify some of them display excellent BL signals in vitro and in vivo, and thus should be noted as one of the ideal substrates for in vivo BLI compared with a well-known conventional substrate, DeepBlueC.

Split-Luciferase Complementation for Analysis of Virus-Host Protein Interactions

Productive viral infection entails highly regulated and sequential protein-protein interactions between viral factors and between virus and host factors. Deciphering such interactions is of paramount importance for a better understanding of virus infection cycles and the development of new strategies for virus prevention and control. In this protocol, we describe a split-luciferase complementation (SLC ) assay for the detection of protein-protein interaction in Nicotiana benthamiana leaves following agroinfiltration-mediated transient protein expression. In this assay, the firefly luciferase protein is divided into two halves, each expressed as a fusion to a prey or bait protein, respectively. Interaction of the two candidate proteins brings the two otherwise nonfunctional halves into close proximity to restore the luciferase activity, which catalyzes the substrate D-luciferin to emit luminescence. The SLC assay allows for noninvasive, quantitative measurement of dynamic protein interactions in living cells within their native cellular compartments.

Quantitative Assessment of the Efficacy of Near-Infrared Photoimmunotherapy with Bioluminescence Imaging

Near-infrared photoimmunotherapy (NIR-PIT) is a cell-specific cancer therapy in which antibody-photoabsorber conjugates (APCs) are activated by NIR light to induce rapid immunogenic cell death with minimal off-target effects. In preclinical settings, bioluminescence imaging (BLI) is useful to quantitatively assess the efficacy of NIR-PIT for both in vitro and in vivo experiments, especially in the early phase of testing. Here, we describe the detailed methods of the experiments for NIR-PIT and evaluation of its efficacy using BLI.

Biosynthesis-Inspired Deracemizative Production of D-Luciferin In Vitro by Combining Luciferase and Thioesterase

Due to the strict enantioselectivity of firefly luciferase (FLuc), only D-luciferin can be used as a substrate for the bioluminescence (BL) reaction. Unfortunately, luciferin racemizes easily and accumulation of nonluminous L-luciferin has negative influences on the light-emitting reaction. By a detailed analysis of luciferin chirality, however, it becomes clarified that L-luciferin is the biosynthetic precursor of D-luciferin in fireflies and undergoes the enzymatic chiral inversion. By the chiral inversion reaction, the enantiopurity of luciferin can be maintained in the reaction mixture for applications using FLuc. Thus, chirality is crucial for the BL reaction and essential for investigating and applying the biosynthesis of D-luciferin. Here, we describe the methods for the analysis of chiral inversion reaction using high-performance liquid chromatography (HPLC) with a chiral column. We also introduce an example of an in vitro deracemizative BL reaction system using a combination of FLuc and fatty acyl-CoA thioesterase, which is inspired by the chiral inversion mechanism in the biosynthetic pathway of D-luciferin.

Bioluminescence-Optogenetics: A Practical Guide

Manipulation of neural activity in genetically predefined populations of neurons through genetic techniques is an essential tool in the field of neuroscience as well as a potential avenue in treating a vast assortment of neurological and psychiatric diseases. Here, we describe an emerging methodology of molecular neuromodulation termed bioluminescence-optogenetics (BL-OG) where BL is harnessed to activate bacterial light-driven channels and pumps expressed in neurons to control their activity. BL-OG is realized through opsin-luciferase fusion proteins called luminopsins (LMOs). In this chapter, we will provide a practical guide for applying BL-OG and LMOs in vitro using a cell line and primary cells in culture. In the following chapter, we will turn our focus towards BL-OG applications in ex vivo and in vivo rodent models of the nervous system.

In Vivo Bioluminescent Imaging of Rabies Virus Infection and Evaluation of Antiviral Drug

In vivo bioluminescence imaging (BLI) methods enable the longitudinal and semi-quantitative monitoring of viral replication dynamics in small animal models and, thus, are useful for examining viral pathogenesis and the effect of antiviral drugs. Here, we describe an in vivo BLI method to evaluate the efficacy of antiviral drugs against rabies virus (RABV) infection in mice. We exemplify mice inoculated with recombinant RABV expressing red firefly luciferase and administered orally with the antiviral drug, favipiravir. For the imaging, mice are intraperitoneally administered with D-luciferin and placed in the dark chamber of an imaging system. The BL images are captured using a highly sensitive charge-coupled device camera. Image data are processed and analyzed using image analysis software.

Applications of Bioluminescence-Optogenetics in Rodent Models

In the preceding chapter, we introduced bioluminescence-optogenetics (BL-OG) and luminopsin fusion proteins (LMOs), an emerging method of molecular neuromodulation. In addition to reviewing the fundamental principles of BL-OG, we provided a discussion of its application in vitro, including with cell lines and primary cells in culture in vitro. BL-OG is mediated by an easily diffusible molecule, luciferin, and when applied systemically in rodents, the substrate can spread throughout the body, including the brain, achieving powerful molecular neuromodulation with convenience even in awake and behaving animals. In this chapter, we provide a practical guide for BL-OG and LMO applications in rodent models of the nervous system, both ex vivo and in vivo.

The analysis of Period1 gene expression in vivo and in vitro using a micro PMT system

To detect a small amount of Period1 (Per1) expression, we developed a micro-photomultiplier tube (μPMT) system which can be used both in vivo and in vitro. Using this system, we succeeded in detecting Per1 gene expression in the skin of freely moving mice over 240 times higher compared with that of the tissue contact optical sensor (TCS) as previously reported. For in vitro studies, we succeeded in detecting elevated Per1 expression by streptozotocin (STZ) treatment in the scalp hairs at an early stage of diabetes, when glucose content in the blood was still normal. In addition, we could detect elevated Per1 expression in a single whisker hair at the time of diabetes onset. These results show that our μPMT system responds to minute changes in gene expression in freely moving mice in vivo and in mice hair follicles in vitro. Furthermore, Per1 in the hair can be used for a marker of diabetic aggravation.

Etmopterus lantern sharks use coelenterazine as the substrate for their luciferin-luciferase bioluminescence system

The lantern shark genus Etmopterus contains approximately 40 species of deep-sea bioluminescent cartilaginous fishes. They emit blue light mainly from the ventral body surface. The biological functions of this bioluminescence have been discussed based on the luminescence patterns, but the bioluminescence mechanism remains uncertain. In this study, we detected both coelenterazine and coelenterazine-dependent luciferase activity in the ventral photophore tissue of Etmopterus molleri. The results suggested that bioluminescence in lantern sharks is produced using coelenterazine as the substrate for the luciferin-luciferase reaction, as some luminous bony fishes.

Period1 gene expression in the olfactory bulb and liver of freely moving streptozotocin-treated diabetic mouse

Clock genes express circadian rhythms in most organs. These rhythms are organized throughout the whole body, regulated by the suprachiasmatic nucleus (SCN) in the brain. Disturbance of these clock gene expression rhythms is a risk factor for diseases such as obesity. In the present study, to explore the role of clock genes in developing diabetes, we examined the effect of streptozotocin (STZ)-induced high glucose on Period1 (Per1) gene expression rhythm in the liver and the olfactory bub (OB) in the brain. We found a drastic increase of Per1 expression in both tissues after STZ injection while blood glucose content was low. After a rapid expression peak, Per1 expression showed no rhythm. Associated with an increase of glucose content, behavior became arrhythmic. Finally, we succeeded in detecting an increase of Per1 expression in mice hair follicles on day 1 after STZ administration, before the onset of symptoms. These results show that elevated Per1 expression by STZ plays an important role in the aggravation of diabetes.

Emerging tools for bioluminescence imaging

Bioluminescence (BL) relies on the enzymatic reaction between luciferase, a substrate conventionally named luciferin, and various cofactors. BL imaging has become a widely used technique to interrogate gene expression and cell fate, both in small and large animal models of research. Recent developments include the generation of improved luciferase-luciferin systems for deeper and more sensitive imaging as well as new caged luciferins to report on enzymatic activity and other intracellular functions. Here, we critically evaluate the emerging tools for BL imaging aiming to provide the reader with an updated compendium of the latest developments (2018-2020) and their notable applications.

Bioluminescence-Optogenetics

In this chapter, we introduce a relatively new, emerging method for molecular neuromodulation-bioluminescence-optogenetics. Bioluminescence-optogenetics is mediated by luminopsin fusion proteins-light-sensing opsins fused to light-emitting luciferases. We describe their structures and working mechanisms and discuss their unique benefits over conventional optogenetics and chemogenetics. We also summarize applications of bioluminescence-optogenetics in various neurological disease models in rodents.

Evaluating Brightness and Spectral Properties of Click Beetle and Firefly Luciferases Using Luciferin Analogues: Identification of Preferred Pairings of Luciferase and Substrate for In Vivo Bioluminescence Imaging

Purpose

Currently, a variety of red and green beetle luciferase variants are available for bioluminescence imaging (BLI). In addition, new luciferin analogues providing longer wavelength luminescence have been developed that show promise for improved deep tissue imaging. However, a detailed assessment of these analogues (e.g., Akalumine-HCl, CycLuc1, and amino naphthyl luciferin (NH₂-NpLH2)) combined with state of the art luciferases has not been performed. The aim of this study was to evaluate for the first time the in vivo brightness and spectral characteristics of firefly (Luc2), click beetle green (CBG99), click beetle red 2 (CBR2), and Akaluc luciferases when paired with different d-luciferin (d-LH2) analogues in vivo.

Procedures

Transduced human embryonic kidney (HEK 293T) cells expressing individual luciferases were analyzed both in vitro and in mice (via subcutaneous injection). Following introduction of the luciferins to cells or animals, the resulting bioluminescence signal and photon emission spectrum were acquired using a sensitive charge-coupled device (CCD) camera equipped with a series of band pass filters and spectral unmixing software.

Results

Our in vivo analysis resulted in four primary findings: (1) the best substrate for Luc2, CBG99, and CBR2 in terms of signal strength was d-luciferin; (2) the spectra for Luc2 and CBR2 were shifted to a longer wavelength when Akalumine-HCl was the substrate; (3) CBR2 gave the brightest signal with the near-infrared substrate, NH₂-NpLH2; and (4) Akaluc was brighter when paired with either CycLuc1 or Akalumine-HCl when paired with d-LH2.

Conclusion

We believe that the experimental results described here should provide valuable guidance to end users for choosing the correct luciferin/luciferase pairs for a variety of BLI applications.

Electronic supplementary material

The online version of this article (10.1007/s11307-020-01523-7) contains supplementary material, which is available to authorized users.

Real-time tracking of stem cell viability, proliferation, and differentiation with autonomous bioluminescence imaging

BACKGROUND

Luminescent reporter proteins are vital tools for visualizing cells and cellular activity. Among the current toolbox of bioluminescent systems, only bacterial luciferase has genetically defined luciferase and luciferin synthesis pathways that are functional at the mammalian cell temperature optimum of 37 °C and have the potential for in vivo applications. However, this system is not functional in all cell types, including stem cells, where the ability to monitor continuously and in real-time cellular processes such as differentiation and proliferation would be particularly advantageous.

RESULTS

We report that artificial subdivision of the bacterial luciferin and luciferase pathway subcomponents enables continuous or inducible bioluminescence in pluripotent and mesenchymal stem cells when the luciferin pathway is overexpressed with a 20-30:1 ratio. Ratio-based expression is demonstrated to have minimal effects on phenotype or differentiation while enabling autonomous bioluminescence without requiring external excitation. We used this method to assay the proliferation, viability, and toxicology responses of iPSCs and showed that these assays are comparable in their performance to established colorimetric assays. Furthermore, we used the continuous luminescence to track stem cell progeny post-differentiation. Finally, we show that tissue-specific promoters can be used to report cell fate with this system.

CONCLUSIONS

Our findings expand the utility of bacterial luciferase and provide a new tool for stem cell research by providing a method to easily enable continuous, non-invasive bioluminescent monitoring in pluripotent cells.

Detection of Extracellular ATP in the Tumor Microenvironment, Using the pmeLUC Biosensor

ATP is one of the main components of the tumor microenvironment, where it affects cell growth, tumor progression and antitumor immune response. The development of the pmeLUC probe, a luciferase engineered to be expressed on the outer facet of the plasma membrane, allowed real-time measurement of extracellular ATP in vitro and in vivo systems, among which the tumor microenvironment. Here we describe the experimental procedures to measure extracellular ATP levels in the tumor microenvironment of three different cancer models generated by the implant of pmeLUC-expressing tumor cells into the appropriate mice strain: ACN human neuroblastoma (nude/nude mice host), WEHI-3B murine leukemia (BALB/c host), and B16F10 murine melanoma (C57Bl/6 host). The procedure to obtain stable expression of pmeLUC in different cell types and methods for the measurement of extracellular ATP with pmeLUC in vitro are also described.

ATP Measurement in Cerebrospinal Fluid Using a Microplate Reader

Imbalance in extracellular ATP levels in brain tissue has been suggested as a triggering factor for several neurological disorders. Here, we describe the most sensitive and reliable technique for monitoring the ATP levels in mice cerebrospinal samples collected by cisterna magna puncture technique and quantified using a microplate reader.

In Vivo Bioimaging for Monitoring Intratumoral Virus Activity

In vivo studies are the mainstay of translational immune-oncology and virotherapy research. In general oncology, bioluminescence imaging provides a convenient and reliable tool to visualize disseminated tumors and monitor growth kinetics or treatment effects. Unique aspects of this method in the field of oncolytic viruses are tracing the process of tumor-specific targeting, assessing potential off-target replication, and visualizing intratumoral spread. In addition, the longitudinal monitoring of virus activity kinetics over time is a very powerful feature supporting the subsequent, often elaborate, preclinical biodistribution and pharmtox program. Here we present a step-by-step standard imaging protocol used in our group for both tumor and virus monitoring, along with background information and general principles that should allow the reader to modify and adapt the protocol according to their needs.

Bioluminescence Imaging to Study Mature Biofilm Formation by Candida spp. and Antifungal Activity In Vitro and In Vivo

The widespread use of indwelling medical devices has increased the number of device-related infections in hospitalized patients. These infections are often associated with the formation of biofilms on the medical implants that are difficult to treat because of their resistance to the classical antifungal drugs. The most common fungi isolated from catheters and other medical devices are Candida species. The Candida genus contains multiple species of which C. albicans and C. glabrata are the two most common pathogenic yeasts in humans. A limited number of animal models is available for investigating host-pathogen interactions and testing novel antifungal drugs in vivo against these species. Fungal load in biofilms in these models is traditionally analyzed postmortem, requiring host sacrifice and enumeration of microorganisms from individual biofilms in order to evaluate the amount of colony forming units and the efficacy of antifungal treatment. Bioluminescence imaging (BLI) made compatible with small animal models for in vivo biofilm formation is a valuable tool to follow biofilm development and its treatment longitudinally. Due to the noninvasive nature of BLI, the imaging procedure can be repeated in the same animal, allowing for follow-up of the biofilm growth in vivo without removing the implanted device or detaching the biofilm from its substrate. Although detecting a quantifiable in vivo BLI signal from biofilms formed on the inside of implanted catheters is challenging, BLI proved to be a practical tool in the study of fungal biofilms. This method describes the use of BLI for in vitro and in vivo follow-up of device-related fungal biofilm formation in mice and rats and antifungal activity testing against both C. albicans and C. glabrata device-associated biofilms. It can further be applied for efficient in vivo screening for interesting genes of the pathogen and the host involved in biofilm formation.

Continual Conscious Bioluminescent Imaging in Freely Moving Mice

In vivo bioluminescent imaging allows the detection of reporter gene expression in rodents in real time. Here we describe a novel technology whereby we can generate somatotransgenic rodents with the use of a viral vector carrying a luciferase transgene. We are able to achieve long term luciferase expression by a single injection of lentiviral or adeno-associated virus vectors to newborn mice. Further, we describe whole body bioluminescence imaging of conscious mice in a noninvasive manner, thus enforcing the 3R's (replacement, reduction, and refinement) of biomedical animal research.

Molecular and biochemical basis for the loss of bioluminescence in the dinoflagellate Noctiluca scintillans along the west coast of the USA

The globally distributed heterotrophic dinoflagellate Noctiluca scintillans (Macartney) Kofoid & Swezy is well known for its dense blooms and prominent displays of bioluminescence. Intriguingly, along the west coast of the USA its blooms are not bioluminescent. We investigated the basis for the regional loss of bioluminescence using molecular, cellular and biochemical analyses of isolates from different geographic regions. Prominent differences of the non-bioluminescent strains were: (1) the fused luciferase and luciferin binding protein gene (lcf/lbp) was present but its transcripts were undetectable; (2) lcf/lbp contained multiple potentially deleterious mutations; (3) the substrate luciferin was absent, based on the lack of luciferin blue autofluorescence and the absence of luciferin derived metabolites; (4) although the cells possessed scintillons, the vesicles that contain the luminescent chemistry, electron microscopy revealed additional scintillon-like vesicles with an atypical internal structure; (5) cells isolated from the California coast were 43% smaller in size than bioluminescent cells from the Gulf of Mexico. Phylogenetic analyses based on the large subunit of rDNA did not show divergence of the non-bioluminescent population in relation to other bioluminescent N. scintillans from the Pacific Ocean and Arabian Sea. Our study demonstrates that gene silencing and the lack of the luciferin substrate have resulted in the loss of a significant dinoflagellate functional trait over large spatial scales in the ocean. As the bioluminescence system of dinoflagellates is well characterized, non-bioluminescent N. scintillans is an ideal model to explore the evolutionary and ecological mechanisms that lead to intraspecific functional divergence in natural dinoflagellate populations.

Comparison of inner ear drug availability of combined treatment with systemic or local drug injections alone

Combination of systemic and local drug therapy has been proved more effective and safer for idiopathic sudden sensorineural hearing loss by some clinical trials, and there are few laboratory researches on its pharmacokinetic behaviors in the inner ear. In the present study, we use a new in vivo imaging system to compare the pharmacokinetics of combined therapy (CT), with intravenous (IV) or transtympanic (TT) injection alone in both ears of transgenic GFAP-Luc mice. Biological half-life, total photon counts and the area under the curve (AUC) value significantly increased after CT. However, adding IV to TT injection cannot strengthen the peak photon of the drug in the inner ear. In addition, when D-luciferin is injected to the left ear the volume of total photon count and AUC value of CT-left ear are larger than the combined volume of TT-left ear and IV-left ear, suggesting a synergistic effect, and those of CT-right ear are almost equal to the summation of those of IV-right group and TT-right group, suggesting no amplifying effect on the risk of systemic side effect. This study showed that CT could deliver more drugs into the inner ear, and brought a longer therapeutic window, and were more effective than intravenous or transtympanic injection alone in the pharmacokinetics.

Simultaneous Fluorescent Recordings of Extracellular ATP and IntracellularCalcium in Mammalian Cells

Extracellular ATP is a potent signaling molecule that stimulates intracellular calcium responses through purinergic (P2) receptors in mammalian cells. While extracellular ATP and intracellular calcium can be measured separately, simultaneous monitoring can offer additional insights into P2 receptor physiology. This protocol takes advantage of the overlapping fluorescence spectra between the ATP-detection substrate luciferin and calcium indicator dye Fura2. Mammalian cells are loaded with Fura2-AM and live-cell recordings are acquired in the presence of a luciferin-luciferase imaging solution. This protocol allows to study stimulus-induced ATP release and directly relate changes in extracellular ATP concentration to observed calcium responses.

A brief review of bioluminescent systems (2019)

Despite being widely used in reporter technologies, bioluminescent systems are largely understudied. Of at least forty different bioluminescent systems thought to exist in nature, molecular components of only seven light-emitting reactions are known, and the full biochemical pathway leading to light emission is only understood for two of them. Here, we provide a succinct overview of currently known bioluminescent systems highlighting available tools for research and discussing future applications.

Molecular Imaging of Therapeutic Effect of Mesenchymal Stem Cell-Derived Exosomes for Hindlimb Ischemia Treatment

Critical limb ischemia is a major cause of morbidity and mortality worldwide. Recently, many studies confirmed that MSC-derived exosomes (MSC-exosomes) had potential therapeutic effect to treat hindlimb ischemia through pro-angiogenesis. The therapeutic angiogenesis is a critical measurement to judge the beneficial effect of MSC-exosomes treatment. Formerly, the therapeutic effect of MSC-exosomes was usually evaluated through clinical assessment and histopathological examination. Here, we describe a strategy to evaluate the therapeutic effect of MSC-exosomes by monitoring the therapeutic angiogenesis with bioluminescent imaging in hindlimb ischemia mice models.

Molecular Mechanisms of Bacterial Bioluminescence

Bioluminescence refers to the production of light by living organisms. Bioluminescent bacteria with a variety of bioluminescence emission characteristics have been identified in Vibrionaceae, Shewanellaceae and Enterobacteriaceae. Bioluminescent bacteria are mainly found in marine habitats and they are either free-floating, sessile or have specialized to live in symbiosis with other marine organisms. On the molecular level, bioluminescence is enabled by a cascade of chemical reactions catalyzed by enzymes encoded by the lux operon with the gene order luxCDABEG. The luxA and luxB genes encode the α- and β- subunits, respectively, of the enzyme luciferase producing the light emitting species. LuxC, luxD and luxE constitute the fatty acid reductase complex, responsible for the synthesis of the long-chain aldehyde substrate and luxG encodes a flavin reductase. In bacteria, the heterodimeric luciferase catalyzes the monooxygenation of long-chain aliphatic aldehydes to the corresponding acids utilizing reduced FMN and molecular oxygen. The energy released as a photon results from an excited state flavin-4a-hydroxide, emitting light centered around 490 nm. Advances in the mechanistic understanding of bacterial bioluminescence have been spurred by the structural characterization of protein encoded by the lux operon. However, the number of available crystal structures is limited to LuxAB (Vibrio harveyi), LuxD (Vibrio harveyi) and LuxF (Photobacterium leiognathi). Based on the crystal structure of LuxD and homology models of LuxC and LuxE, we provide a hypothetical model of the overall structure of the LuxCDE fatty acid reductase complex that is in line with biochemical observations.

Bioluminescence expression during the transition from mycelium to mushroom in three North American Armillaria and Desarmillaria species

Unlike most bioluminescent fungi, mycelia of Armillaria and Desarmillaria are constitutively bioluminescent while mature mushrooms are not. The absence of the luciferin, 3-hydroxyhispidin, and its precursor hispidin in mature mushrooms have been proposed to explain the lack of bioluminescence from Armillaria mushrooms. Using three North American species, A. gallica, A. mellea and D. tabescens (syn., Armillaria tabescens), we documented a decline in luminescence of ten fold during the transition from mycelia to, immature mushrooms (i.e., pins) for the two Armillaria species. As pins matured, luminescence declined by an additional two or three orders of magnitude. Lower initial luminescence of D. tabescens mycelia declined to negligible levels during mushroom development. Further, light production was localized in the gills and lower stipe of A. mellea mushrooms. The decline in luminescence during mushroom formation was reversed by addition of hispidin to stipe or gills which significantly enhanced luminescence by one and three orders of magnitude, respectively. We conclude that the modulation of Armillaria and Desarmillaria luminescence is achieved by luciferin availability early in mushroom development. However, since the temporal regulation of bioluminescence differs between Armillaria species and other genera, we conclude that bioluminescence in Armillaria is under unique selective pressures.

Luciferin production and luciferase transcription in the bioluminescent copepod Metridia lucens

Bioluminescent copepods are often the most abundant marine zooplankton and play critical roles in oceanic food webs. Metridia copepods exhibit particularly bright bioluminescence, and the molecular basis of their light production has just recently begun to be explored. Here we add to this body of work by transcriptomically profiling Metridia lucens, a common species found in temperate, northern, and southern latitudes. In this previously molecularly-uncharacterized species, we find the typical luciferase paralog gene set found in Metridia. More surprisingly, we recover noteworthy putative luciferase sequences that had not been described from Metridia species, indicating that bioluminescence produced by these copepods may be more complex than previously known. This includes another copepod luciferase, as well as one from a shrimp. Furthermore, feeding experiments using mass spectrometry and ¹³C labelled L-tyrosine and L-phenylalanine firmly establish that M. lucens produces its own coelenterazine luciferin rather than acquiring it through diet. This coelenterazine synthesis has only been directly confirmed in one other copepod species.

Feature-preserving noise reduction by using time-domain Gaussian-weighted multiple noise reduction filters for real-time bioluminescence measurement

This paper proposes a time-domain Gaussian-weighted noise reduction filter for bioluminescence measurement with low signal-to-noise ratio through photon counting. The filter was used for estimating the true fold-change signal from noisy gene expression data obtained through real-time dual-color luciferase assay. Furthermore, not only was the higher harmonics noise of the measurement system confirmed to reduce from the gene expression data but rapid and slow changes were also preserved in the estimated signal. In addition, the probability value of Pearson's chi-squared test was improved 257 times at most and 1.5 times on average without impairing the noise reduction ratio.

Optical Bioluminescence Protocol for Imaging Mice

The presence, growth, or decline of transfected cell populations expressing the enzyme Luciferase can be followed in live mice using bioluminescence optical imaging techniques. This protocol describes how to verify the imaging equipment, options for injecting the substrate Luciferin into mice, image acquisition considerations, and commonly used data analysis techniques.

Assessing Extracellular ATP as Danger Signal In Vivo: The pmeLuc System

Inflammation is the key pathophysiological response triggered by noxious agents in multicellular organisms. Central to inflammation is detection of exogenous or endogenous danger signals by immune cells. Extracellular ATP is a ubiquitous danger signal released during septic or sterile inflammation. The development of reliable techniques to measure extracellular ATP in vivo has become an urgent need in inflammation studies after the discovery that the most potent plasma membrane receptor responsible for NLRP3 inflammasome activation is an ATP-activated receptor, P2RX7. Here we describe an easy bioluminescence technique for the measurement of extracellular ATP in vivo.

On the use of peroxy-caged luciferin (PCL-1) probe for bioluminescent detection of inflammatory oxidants in vitro and in vivo - Identification of reaction intermediates and oxidant-specific minor products

Peroxy-caged luciferin (PCL-1) probe was first used to image hydrogen peroxide in living systems (Van de Bittner et al., 2010 [9]). Recently this probe was shown to react with peroxynitrite more potently than with hydrogen peroxide (Sieracki et al., 2013 [11]) and was suggested to be a more suitable probe for detecting peroxynitrite under in vivo conditions. In this work, we investigated in detail the products formed from the reaction between PCL-1 and hydrogen peroxide, hypochlorite, and peroxynitrite. HPLC analysis showed that hydrogen peroxide reacts slowly with PCL-1, forming luciferin as the only product. Hypochlorite reaction with PCL-1 yielded significantly less luciferin, as hypochlorite oxidized luciferin to form a chlorinated luciferin. Reaction between PCL-1 and peroxynitrite consists of a major and minor pathway. The major pathway results in luciferin and the minor pathway produces a radical-mediated nitrated luciferin. Radical intermediate was characterized by spin trapping. We conclude that monitoring of chlorinated and nitrated products in addition to bioluminescence in vivo will help identify the nature of oxidant responsible for bioluminescence derived from PCL-1.

Synthetic Bioluminescent Coelenterazine Derivatives

The development of coelenterazine (CTZ) derivatives resulting in superior optical characteristics is an efficient method to extend the range of its possible applications. Here, we describe the synthesis of three C-6 substituted CTZ derivatives retaining the recognition by Renilla luciferase (RLuc) and its derivatives. The novel derivatives are useful as bright blue-shifted CTZ derivatives, which can be used as an alternative to hitherto reported compound DeepBlueC™.

Establishment of procedures for studying mPR-interacting agents and physiological roles of mPR

More than 10years have passed since the discovery of membrane progestin receptors (mPRs). Although the identification of mPR genes in various organisms and mPR expression patterns have been described since then, the precise physiological roles of mPRs are still unclear, except their function as a receptor for maturation-inducing steroid in fish. The wide distribution of mPRs suggests variable actions for progestins through mPRs in the tissues. Information about the physiological roles of mPRs, such as roles in the progression of breast cancer and T-cell proliferation, has gradually accumulated recently. These results suggest that mPRs are possible targets for new pharmaceuticals. We established a cell line that was transformed with cDNAs for mPRα and a recombinant luciferase gene named GloSensor. The cells can be used for monitoring the effects of ligands on mPRα based on intracellular cyclic adenosine monophosphate (cAMP) levels. Studies using these cell lines indicated that the cAMP concentration is decreased by ligands for mPRα. The results provide support for previous results suggesting that mPRα is coupled to inhibitory G protein (Gi). We also established screening methods that make it possible to screen ligands for mPR. Recently, we succeeded in expressing and purifying recombinant mPR protein in the yeast Pichia pastoris. Relatively large amounts of mPR protein with hormonal binding activity can be purified by our method. The recombinant protein will be applicable to establishing a molecular probe to detect mPR-interacting agents. To obtain decisive evidence for the roles of mPRs, we are establishing strains of medaka fish that are deficient in mPRs. In medaka, four subtypes of mPR genes (α, β, γ, and α2) have been identified. By reverse genetic screening, we have selected three to four strains in which a point mutation has been induced in the coding sequence of the mPR subtypes. However, homozygous mutants of each mPR gene showed no phenotype. The results suggested that mPR genes share redundancy. We are currently producing double and triple mutants of the mPR subtypes. The physiological roles of mPRs will be demonstrated using the mutant medaka strains.

Cell-based assay of nongenomic actions of progestins revealed inhibitory G protein coupling to membrane progestin receptor α (mPRα)

Previously, we established cell lines stably producing goldfish membrane progestin receptor α (goldfish mPRα) proteins, which mediate steroidal nongenomic actions. In this study, we transfected these cell lines (MDA-MD-231) with cDNAs encoding a recombinant luciferase gene (GloSensor). These cells can be used for monitoring the effects of ligands that bind to mPR by means of luminescence, the intensity of which reflects intracellular cyclic adenosine monophosphate (cAMP) levels. Luminescence intensity of the cells increased significantly when cells were treated with forskolin, strong activator of adenylyl cyclase. Then, we established a strategy to measure changes in luminescence that correlated with the actions of the ligands. The actions of ligands were measurable by the prevention of stimulation caused by forskolin after ligand stimulation. The studies using these cell lines indicated that cAMP concentrations were decreased specifically by the mPR ligands 17α,20β-dihydroxy-4-pregnen-3-one, diethylstilbestrol and progesterone. Furthermore, pertussis toxin inhibited the decrease in cAMP levels caused by mPR ligands. These results support evidence from previous results that mPRα is coupled to an inhibitory G protein.

Luciferin and derivatives as a DYRK selective scaffold for the design of protein kinase inhibitors

D-Luciferin is widely used as a substrate in luciferase catalysed bioluminescence assays for in vitro studies. However, little is known about cross reactivity and potential interference of D-luciferin with other enzymes. We serendipitously found that firefly luciferin inhibited the CDK2/Cyclin A protein kinase. Inhibition profiling of D-luciferin over a 103-protein kinase panel showed significant inhibition of a small set of protein kinases, in particular the DYRK-family, but also other members of the CMGC-group, including ERK8 and CK2. Inhibition profiling on a 16-member focused library derived from D-luciferin confirms that D-luciferin represents a DYRK-selective chemotype of fragment-like molecular weight. Thus, observation of its inhibitory activity and the initial SAR information reported here promise to be useful for further design of protein kinase inhibitors with related scaffolds.

Synthesis and characterization of valyloxy methoxy luciferin for the detection of valacyclovirase and peptide transporter

An amino acid ester derivative of luciferin (valoluc) was synthesized to mimic the transport and activation of valacyclovir. This molecule was characterized in vitro for specificity and enzymatic constants, and then assayed in two different, physiologically-relevant conditions. It was demonstrated that valoluc activation is sensitive to the same cellular factors as valacyclovir and thus has the potential to elucidate the dynamics of amino acid ester prodrug therapies in a functional, high-throughput manner.

Evaluation of Luminescent P450 Analysis for Directed Evolution of Human CYP4A11

Cytochrome P450 4A11 (CYP4A11) is a fatty acid hydroxylase enzyme expressed in human liver. It catalyzes not only the hydroxylation of saturated and unsaturated fatty acids, but the conversion of arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE), a regulator of blood pressure. In this study, we performed a directed evolution analysis of CYP4A11 using the luminogenic assay system. A random mutant library of CYP4A11, in which mutations were made throughout the entire coding region, was screened with luciferase activity to detect the demethylation of luciferin-4A (2-[6-methoxyquinolin-2-yl]-4,5-dihydrothiazole-4-carboxylic acid) of CYP4A11 mutants in Escherichia coli. Consecutive rounds of random mutagenesis and screening yielded three improved CYP4A11 mutants, CP2600 (A24T/T263A), CP2601 (T263A), and CP2616 (A24T/T263A/V430E) with ~3-fold increase in whole cells and >10-fold increase in purified proteins on the luminescence assay. However, the steady state kinetic analysis for lauric acid hydroxylation showed the significant reductions in enzymatic activities in all three mutants. A mutant, CP2600, showed a 51% decrease in catalytic efficiency (k_cat/K_m) for lauric acid hydroxylation mainly due to an increase in K_m. CP2601 and CP2616 showed much greater reductions (>75%) in the catalytic efficiency due to both a decrease in k_cat and an increase in K_m. These decreased catalytic activities of CP2601 and CP2616 can be partially attributed to the changes in substrate affinities. These results suggest that the enzymatic activities of CYP4A11 mutants selected from directed evolution using a luminogenic P450 substrate may not demonstrate a direct correlation with the hydroxylation activities of lauric acid.

Bioluminescent detection of peroxynitrite with a boronic acid-caged luciferin

Peroxynitrite, a highly reactive biological oxidant, is formed under pathophysiologic conditions from the diffusion-limited reaction of nitric oxide and superoxide radical anion. Peroxynitrite has been implicated as the mediator of nitric oxide toxicity in many diseases and as an important signaling disrupting molecule (L. Liaudet et al., Front. Biosci.14, 4809-4814, 2009) [1]. Biosensors effective at capturing peroxynitrite in a specific and fast enough manner for detection, along with readouts compatible with in vivo studies, are lacking. Here we report that the boronic acid-based bioluminescent system PCL-1 (peroxy-caged luciferin-1), previously reported as a chemoselective sensor for hydrogen peroxide (G.C. Van de Bittner et al., Proc. Natl. Acad. Sci. USA107, 21316-21321, 2010) [2], reacts with peroxynitrite stoichiometrically with a rate constant of 9.8±0.3×10(5)M(-1)s(-1) and a bioluminescence detection limit of 16nM, compared to values of 1.2±0.3M(-1)s(-1) and 231nM for hydrogen peroxide. Further, we demonstrate bioluminescent detection of peroxynitrite in the presence of physiological competitors: carbon dioxide, glutathione, albumin, and catalase. We also demonstrate the utility of this method to assess peroxynitrite formation in mammalian cells by measuring peroxynitrite generated under normal culture conditions after stimulation of macrophages with bacterial endotoxin lipopolysaccharide. Thus, the PCL-1 method for measuring peroxynitrite generation shows superior selectivity over other oxidants under in vivo conditions.