A reporter gene assay for high-throughput screening of G-protein-coupled receptors stably or transiently expressed in HEK293 EBNA cells grown in suspension culture

Identification of sulfakinin receptor regulating feeding behavior and hemolymph trehalose homeostasis in the silkworm, Bombyx mori

Feeding behavior, the most fundamental physiological activity, is controlled by two opposing groups of factors, orexigenic and anorexigenic factors. The sulfakinin family, an insect analogue of the mammalian satiety factor cholecystokinin (CCK), has been shown to suppress food intake in various insects. Nevertheless, the mechanisms through which sulfakinin regulates feeding behavior remain a biological question. This study aimed to elucidate the signaling pathway mediated by the anorexigenic peptide sulfakinin in Bombyx mori. We identified the Bombyx mori neuropeptide G protein-coupled receptor A9 (BNGR-A9) as the receptor for sulfakinin through functional assays. Stimulation with sulfakinin triggered a swift increase in intracellular IP3, Ca2+, and a notable enhancement of ERK1/2 phosphorylation, in a manner sensitive to a Gαq-specific inhibitor. Treatment with synthetic sulfakinin resulted in decreased food consumption and average body weight. Additionally, administering synthetic sulfakinin to silkworms significantly elevated hemolymph trehalose levels, an effect markedly reduced by pre-treatment with BNGR-A9 dsRNA. Consequently, our findings establish the sulfakinin/BNGR-A9 signaling pathway as a critical regulator of feeding behavior and hemolymph trehalose homeostasis in Bombyx mori, highlighting its roles in the negative control of food intake and the positive regulation of energy balance.

Platelet-derived growth factor (PDGF)-BB regulates the airway tone via activation of MAP2K, thromboxane, actin polymerisation and Ca2+-sensitisation

BACKGROUND

PDGFR-inhibition by the tyrosine kinase inhibitor (TKI) nintedanib attenuates the progress of idiopathic pulmonary fibrosis (IPF). However, the effects of PDGF-BB on the airway tone are almost unknown. We studied this issue and the mechanisms beyond, using isolated perfused lungs (IPL) of guinea pigs (GPs) and precision-cut lung slices (PCLS) of GPs and humans.

METHODS

IPL: PDGF-BB was perfused after or without pre-treatment with the TKI imatinib (perfused/nebulised) and its effects on the tidal volume (TV), the dynamic compliance (Cdyn) and the resistance were studied.

PCLS (GP)

The bronchoconstrictive effects of PDGF-BB and the mechanisms beyond were evaluated. PCLS (human): The bronchoconstrictive effects of PDGF-BB and the bronchorelaxant effects of imatinib were studied. All changes of the airway tone were measured by videomicroscopy and indicated as changes of the initial airway area.

RESULTS

PCLS (GP/human): PDGF-BB lead to a contraction of airways. IPL: PDGF-BB decreased TV and Cdyn, whereas the resistance did not increase significantly. In both models, inhibition of PDGFR-(β) (imatinib/SU6668) prevented the bronchoconstrictive effect of PDGF-BB. The mechanisms beyond PDGF-BB-induced bronchoconstriction include activation of MAP2K and TP-receptors, actin polymerisation and Ca²⁺-sensitisation, whereas the increase of Ca²⁺ itself and the activation of EP_1-4-receptors were not of relevance. In addition, imatinib relaxed pre-constricted human airways.

CONCLUSIONS

PDGFR regulates the airway tone. In PCLS from GPs, this regulatory mechanism depends on the β-subunit. Hence, PDGFR-inhibition may not only represent a target to improve chronic airway disease such as IPF, but may also provide acute bronchodilation in asthma. Since asthma therapy uses topical application. This is even more relevant, as nebulisation of imatinib also appears to be effective.

Engineering digitizer circuits for chemical and genetic screens in human cells

Cell-based transcriptional reporters are invaluable in high-throughput compound and CRISPR screens for identifying compounds or genes that can impact a pathway of interest. However, many transcriptional reporters have weak activities and transient responses. This can result in overlooking therapeutic targets and compounds that are difficult to detect, necessitating the resource-consuming process of running multiple screens at various timepoints. Here, we present RADAR, a digitizer circuit for amplifying reporter activity and retaining memory of pathway activation. Reporting on the AP-1 pathway, our circuit identifies compounds with known activity against PKC-related pathways and shows an enhanced dynamic range with improved sensitivity compared to a classical reporter in compound screens. In the first genome-wide pooled CRISPR screen for the AP-1 pathway, RADAR identifies canonical genes from the MAPK and PKC pathways, as well as non-canonical regulators. Thus, our scalable system highlights the benefit and versatility of using genetic circuits in large-scale cell-based screening.

Mixture interactions at mammalian olfactory receptors are dependent on the cellular environment

Functional characterization of mammalian olfactory receptors (ORs) remains a major challenge to ultimately understanding the olfactory code. Here, we compare the responses of the mouse Olfr73 ectopically expressed in olfactory sensory neurons using AAV gene delivery in vivo and expressed in vitro in cell culture. The response dynamics and concentration-dependence of agonists for the ectopically expressed Olfr73 were similar to those reported for the endogenous Olfr73, however the antagonism previously reported between its cognate agonist and several antagonists was not replicated in vivo. Expressing the OR in vitro reproduced the antagonism reported for short odor pulses, but not for prolonged odor exposure. Our findings suggest that both the cellular environment and the stimulus dynamics shape the functionality of Olfr73 and argue that characterizing ORs in 'native' conditions, rather than in vitro, provides a more relevant understanding of ligand-OR interactions.

Inhibitory signaling in mammalian olfactory transduction potentially mediated by Gαo

Olfactory GPCRs (ORs) in mammalian olfactory receptor neurons (ORNs) mediate excitation through the Gα_s family member Gα_olf. Here we tentatively associate a second G protein, Gα_o, with inhibitory signaling in mammalian olfactory transduction by first showing that odor evoked phosphoinositide 3-kinase (PI3K)-dependent inhibition of signal transduction is absent in the native ORNs of mice carrying a conditional OMP-Cre based knockout of Gα_o. We then identify an OR from native rat ORNs that are activated by octanol through cyclic nucleotide signaling and inhibited by citral in a PI3K-dependent manner. We show that the OR activates cyclic nucleotide signaling and PI3K signaling in a manner that reflects its functionality in native ORNs. Our findings lay the groundwork to explore the interesting possibility that ORs can interact with two different G proteins in a functionally identified, ligand-dependent manner to mediate opponent signaling in mature mammalian ORNs.

A Forward Chemical Genetic Screen Reveals Gut Microbiota Metabolites That Modulate Host Physiology

The intestinal microbiota produces tens of thousands of metabolites. Here, we used host sensing of small molecules by G-protein coupled receptors (GPCRs) as a lens to illuminate bioactive microbial metabolites that impact host physiology. We screened 144 human gut bacteria against the non-olfactory GPCRome and identified dozens of bacteria that activated both well-characterized and orphan GPCRs, including strains that converted dietary histidine into histamine and shaped colonic motility; a prolific producer of the essential amino acid L-Phe, which we identified as an agonist for GPR56 and GPR97; and a species that converted L-Phe into the potent psychoactive trace amine phenethylamine, which crosses the blood-brain barrier and triggers lethal phenethylamine poisoning after monoamine oxidase inhibitor administration. These studies establish an orthogonal approach for parsing the microbiota metabolome and uncover multiple biologically relevant host-microbiota metabolome interactions.

Computational modeling of the olfactory receptor Olfr73 suggests a molecular basis for low potency of olfactory receptor-activating compounds

The mammalian olfactory system uses hundreds of specialized G-protein-coupled olfactory receptors (ORs) to discriminate a nearly unlimited number of odorants. Cognate agonists of most ORs have not yet been identified and potential non-olfactory processes mediated by ORs are unknown. Here, we used molecular modeling, fingerprint interaction analysis and molecular dynamics simulations to show that the binding pocket of the prototypical olfactory receptor Olfr73 is smaller, but more flexible, than binding pockets of typical non-olfactory G-protein-coupled receptors. We extended our modeling to virtual screening of a library of 1.6 million compounds against Olfr73. Our screen predicted 25 Olfr73 agonists beyond traditional odorants, of which 17 compounds, some with therapeutic potential, were validated in cell-based assays. Our modeling suggests a molecular basis for reduced interaction contacts between an odorant and its OR and thus the typical low potency of OR-activating compounds. These results provide a proof-of-principle for identifying novel therapeutic OR agonists.

Deorphanization of Olfactory Trace Amine-Associated Receptors

Olfaction is the primary sense used by most animals to perceive the external world. The mouse olfactory system is composed of several sensory structures, the largest of which is the main olfactory epithelium (MOE). Olfactory sensory neurons (OSNs) located within the MOE detect odors and pheromones using dedicated seven-transmembrane G protein-coupled receptors (GPCRs). Two families of GPCRs are expressed in the MOE and are conserved in humans and other vertebrates: odorant receptors (ORs) and trace amine-associated receptors (TAARs). TAARs are distantly related to biogenic amine receptors, such as dopamine and serotonin receptors. Several TAARs detect volatile amines including ethological odors that evoke innate animal behavioral responses. Mouse TAAR4 recognizes the aversive predator odor 2-phenylethylamine, while mouse TAAR5 detects the attractive male mouse odor trimethylamine. In zebrafish, TAAR13c detects the foul death-associated odor cadaverine that mediates innate avoidance behavior. TAARs thus provide an excellent model subsystem to study odor valence. And identification of additional high-affinity ligands for TAARs will provide extra tools for such study. Therefore, this chapter focuses on the so-called SEAP assay that has been successfully applied for TAAR deorphanization in different species.

A novel L1CAM isoform with angiogenic activity generated by NOVA2-mediated alternative splicing

The biological players involved in angiogenesis are only partially defined. Here, we report that endothelial cells (ECs) express a novel isoform of the cell-surface adhesion molecule L1CAM, termed L1-ΔTM. The splicing factor NOVA2, which binds directly to L1CAM pre-mRNA, is necessary and sufficient for the skipping of L1CAM transmembrane domain in ECs, leading to the release of soluble L1-ΔTM. The latter exerts high angiogenic function through both autocrine and paracrine activities. Mechanistically, L1-ΔTM-induced angiogenesis requires fibroblast growth factor receptor-1 signaling, implying a crosstalk between the two molecules. NOVA2 and L1-ΔTM are overexpressed in the vasculature of ovarian cancer, where L1-ΔTM levels correlate with tumor vascularization, supporting the involvement of NOVA2-mediated L1-ΔTM production in tumor angiogenesis. Finally, high NOVA2 expression is associated with poor outcome in ovarian cancer patients. Our results point to L1-ΔTM as a novel, EC-derived angiogenic factor which may represent a target for innovative antiangiogenic therapies.

Growing tumors stimulate the formation of new blood vessels to supply the oxygen and nutrients the cancerous cells need to stay alive. Stopping tumors from forming the blood vessels could therefore help us to treat cancer. To do so, we need to understand how different proteins control when and how blood vessels develop.

Cells make proteins by first ‘transcribing’ genes to form RNA molecules. In many cases, the RNA then goes through a process called alternative splicing. Proteins known as splicing factors cut out different segments of the RNA molecule and stick together the remaining segments to form templates for protein production. This enables a single gene to produce many different variants of a protein.

Angiolini, Belloni, Giordano et al. have now studied mouse and human versions of the cells that line the blood vessels grown by tumors. This revealed that a splicing factor called NOVA2 targets a protein called L1CAM, which is normally responsible for gluing adjacent cells together. Angiolini et al. found that NOVA2 splices L1CAM into a form not seen before. Instead of remaining anchored to cell surfaces, the newly identified form of L1CAM is released into the blood circulation, where it stimulates new blood vessels to grow.

Samples taken from the blood vessels of human ovarian tumors showed high levels of both NOVA2 and the modified form of L1CAM, while blood vessels in healthy tissue contain no, or very low levels of both proteins. Therefore, if the new form of L1CAM can be detected in the blood, it could be used to help cancer diagnosis, and to indicate which patients would benefit from treatments that restrict the growth of blood vessels in tumors. Further work is now needed to explore these possibilities.

PDGF-BB regulates the pulmonary vascular tone: impact of prostaglandins, calcium, MAPK- and PI3K/AKT/mTOR signalling and actin polymerisation in pulmonary veins of guinea pigs

Background

Platelet-derived growth factor (PDGF)-BB and its receptor PDGFR are highly expressed in pulmonary hypertension (PH) and mediate proliferation. Recently, we showed that PDGF-BB contracts pulmonary veins (PVs) and that this contraction is prevented by inhibition of PDGFR-β (imatinib/SU6668). Here, we studied PDGF-BB-induced contraction and downstream-signalling in isolated perfused lungs (IPL) and precision-cut lung slices (PCLS) of guinea pigs (GPs).

Methods

In IPLs, PDGF-BB was perfused after or without pre-treatment with imatinib (perfused/nebulised), the effects on the pulmonary arterial pressure (P_PA), the left atrial pressure (P_LA) and the capillary pressure (P_cap) were studied and the precapillary (R_pre) and postcapillary resistance (R_post) were calculated. Perfusate samples were analysed (ELISA) to detect the PDGF-BB-induced release of prostaglandin metabolites (TXA₂/PGI₂). In PCLS, the contractile effect of PDGF-BB was evaluated in pulmonary arteries (PAs) and PVs. In PVs, PDGF-BB-induced contraction was studied after inhibition of PDGFR-α/β, L-Type Ca²⁺-channels, ROCK/PKC, prostaglandin receptors, MAP2K, p38-MAPK, PI3K-α/γ, AKT/PKB, actin polymerisation, adenyl cyclase and NO. Changes of the vascular tone were measured by videomicroscopy. In PVs, intracellular cAMP was measured by ELISA.

Results

In IPLs, PDGF-BB increased P_PA, P_cap and R_post. In contrast, PDGF-BB had no effect if lungs were pre-treated with imatinib (perfused/nebulised). In PCLS, PDGF-BB significantly contracted PVs/PAs which was blocked by the PDGFR-β antagonist SU6668. In PVs, inhibition of actin polymerisation and inhibition of L-Type Ca²⁺-channels reduced PDGF-BB-induced contraction, whereas inhibition of ROCK/PKC had no effect. Blocking of EP_1/3- and TP-receptors or inhibition of MAP2K-, p38-MAPK-, PI3K-α/γ- and AKT/PKB-signalling prevented PDGF-BB-induced contraction, whereas inhibition of EP₄ only slightly reduced it. Accordingly, PDGF-BB increased TXA₂ in the perfusate, whereas PGI₂ was increased in all groups after 120 min and inhibition of IP-receptors did not enhance PDGF-BB-induced contraction. Moreover, PDGF-BB increased cAMP in PVs and inhibition of adenyl cyclase enhanced PDGF-BB-induced contraction, whereas inhibition of NO-formation only slightly increased it.

Conclusions

PDGF-BB/PDGFR regulates the pulmonary vascular tone by the generation of prostaglandins, the increase of calcium, the activation of MAPK- or PI3K/AKT/mTOR signalling and actin remodelling. More insights in PDGF-BB downstream-signalling may contribute to develop new therapeutics for PH.

Endogenous Locus Reporter Assays

Reporter gene assays are widely used in high-throughput screening (HTS) to identify compounds that modulate gene expression. Traditionally a reporter gene assay is built by cloning an endogenous promoter sequence or synthetic response elements in the regulatory region of a reporter gene to monitor transcriptional activity of a specific biological process (exogenous reporter assay). In contrast, an endogenous locus reporter has a reporter gene inserted in the endogenous gene locus that allows the reporter gene to be expressed under the control of the same regulatory elements as the endogenous gene, thus more accurately reflecting the changes seen in the regulation of the actual gene. In this chapter, we introduce some of the considerations behind building a reporter gene assay for high-throughput compound screening and describe the methods we have utilized to establish 1536-well format endogenous locus reporter and exogenous reporter assays for the screening of compounds that modulate Myc pathway activity.

Live-cell Measurement of Odorant Receptor Activation Using a Real-time cAMP Assay

The enormous sizes of the mammalian odorant receptor (OR) families present difficulties to find their cognate ligands among numerous volatile chemicals. To efficiently and accurately deorphanize ORs, we combine the use of a heterologous cell line to express mammalian ORs and a genetically modified biosensor plasmid to measure cAMP production downstream of OR activation in real time. This assay can be used to screen odorants against ORs and vice versa. Positive odorant-receptor interactions from the screens can be subsequently confirmed by testing against various odor concentrations, generating concentration-response curves. Here we used this method to perform a high-throughput screening of an odorous compound against a human OR library expressed in Hana3A cells and confirmed that the positively-responding receptor is the cognate receptor for the compound of interest. We found this high-throughput detection method to be efficient and reliable in assessing OR activation and our data provide an example of its potential use in OR functional studies.

BNGR-A25L and -A27 are two functional G protein-coupled receptors for CAPA periviscerokinin neuropeptides in the silkworm Bombyx mori

CAPA peptides, such as periviscerokinin (PVK), are insect neuropeptides involved in many signaling pathways controlling, for example, metabolism, behavior, and reproduction. They are present in a large number of insects and, together with their cognate receptors, are important for research into approaches for improving insect control. However, the CAPA receptors in the silkworm (Bombyx mori) insect model are unknown. Here, we cloned cDNAs of two putative CAPA peptide receptor genes, BNGR-A27 and -A25, from the brain of B. mori larvae. We found that the predicted BNGR-A27 ORF encodes 450 amino acids and that one BNGR-A25 splice variant encodes a full-length isoform (BNGR-A25L) of 418 amino acid residues and another a short isoform (BNGR-A25S) of 341 amino acids with a truncated C-terminal tail. Functional assays indicated that both BNGR-A25L and -A27 are activated by the PVK neuropeptides Bom-CAPA-PVK-1 and -PVK-2, leading to a significant increase in cAMP-response element-controlled luciferase activity and Ca²⁺ mobilization in a G_q inhibitor-sensitive manner. In contrast, BNGR-A25S was not significantly activated in response to the PVK peptides. Moreover, Bom-CAPA-PVK-1 directly bound to BNGR-A25L and -A27, but not BNGR-A25S. Of note, CAPA-PVK-mediated ERK1/2 phosphorylation and receptor internalization confirmed that BNGR-A25L and -A27 are two canonical receptors for Bombyx CAPA-PVKs. However, BNGR-A25S alone is a nonfunctional receptor but serves as a dominant-negative protein for BNGR-A25L. These results provide evidence that BNGR-A25L and -A27 are two functional G_q-coupled receptors for Bombyx CAPA-PVKs, enabling the further elucidation of the endocrinological roles of Bom-CAPA-PVKs and their receptors in insect biology.

In Vitro and In Silico Characterization of Lemborexant (E2006), a Novel Dual Orexin Receptor Antagonist

Orexin (hypocretin) neuropeptides have, among others, been implicated in arousal/sleep control, and antagonizing the orexin signaling pathway has been previously demonstrated to promote sleep in animals and humans. This mechanism opens up a new therapeutic approach to curb excessive wakefulness in insomnia disorder rather than to promote sleep-related signaling. Here we describe the preclinical pharmacological in vitro and in silico characterization of lemborexant ((1R,2S)-2-{[(2,4-dimethylpyrimidin-5-yl)oxy]methyl}-2-(3-fluorophenyl)-N-(5-fluoropyridin-2-yl)cyclopropanecarboxamide)), a dual orexin receptor antagonist (DORA), as a novel experimental therapeutic agent for the symptomatic treatment of insomnia disorder and compare its properties to two other DORAs, almorexant and suvorexant. Lemborexant binds to both orexin receptors and functionally inhibits them in a competitive manner with low nanomolar potency, without any species difference apparent among human, rat, and mouse receptors. Binding and dissociation kinetics on both orexin receptors are rapid. Lemborexant is selective for both orexin receptors over 88 other receptors, transporters, and ion channels of important physiologic function. In silico modeling of lemborexant into the orexin receptors showed that it assumes the same type of conformation within the receptor-binding pocket as suvorexant, the π-stacked horseshoe-like conformation.

Regulation of post-Golgi LH3 trafficking is essential for collagen homeostasis

Post-translational modifications are necessary for collagen precursor molecules (procollagens) to acquire final shape and function. However, the mechanism and contribution of collagen modifications that occur outside the endoplasmic reticulum and Golgi are not understood. We discovered that VIPAR, with its partner proteins, regulate sorting of lysyl hydroxylase 3 (LH3, also known as PLOD3) into newly identified post-Golgi collagen IV carriers and that VIPAR-dependent sorting is essential for modification of lysines in multiple collagen types. Identification of structural and functional collagen abnormalities in cells and tissues from patients and murine models of the autosomal recessive multisystem disorder Arthrogryposis, Renal dysfunction and Cholestasis syndrome caused by VIPAR and VPS33B deficiencies confirmed our findings. Thus, regulation of post-Golgi LH3 trafficking is essential for collagen homeostasis and for the development and function of multiple organs and tissues.

Development of a Generic Dual-Reporter Gene Assay for Screening G-Protein-Coupled Receptors

Multiple assay formats have been developed for the pharmacological characterization of G-protein-coupled receptors (GPCRs) and for screening orphan receptors. However, the increased pace of target identification and the rapid expansion of compound libraries present the need to develop novel assay formats capable of screeningmultipleGPCRs simultaneously. To address this need, the authors have developed a generic dual-reporter gene assay that can detect ligand activity at 2 GPCRs within the same assay. Two stableHEK293 cell lineswere generated expressing either a firefly ( Photinus) luciferase gene under the control ofmultiple cAMP-response elements (CREs) or a Renillaluciferase gene under the control ofmultiple 12-Otetradecanoylphorbol-13-acetate (TPA)-responsive elements (TREs). Coseeded reporter cells were used to assess ligandbinding activity at bothGβ s-and Gβ q-coupled receptors. By selectively coexpressing receptors with a chimeric G-protein, agonist activitywas assessed atGβ i/o-coupled receptors in combinationwith eitherGβ s-or Gβ q-coupled receptors. The dual-reporter gene assaywas shown to be capable of simultaneously performing duplexed screens for a variety of agonist and/or antagonist combinations. The data generated from the duplexed reporter assays were pharmacologically relevant, and Zβ factor analysis indicated the suitability of both agonist and antagonist screens for use in high-throughput screening.

A novel 3D high-content assay identifies compounds that prevent fibroblast invasion into tissue surrogates

Invasion processes underlie or accompany several pathological processes but only a limited number of high-throughput capable phenotypic models exist to test anti-invasive compounds in vitro. We here evaluated 3D co-cultures as a high-content phenotypic screening system for fibrotic invasive processes. 3D multicellular spheroids were used as living tissue surrogates in co-culture with fluorescently labeled lung fibroblasts to monitor invasion processes by automated microscopy. This setup was used to screen a compound library containing 480 known bioactive substances. Identified hits prevented fibroblast invasion and could be subdivided into two hit classes. First, Prostaglandins were shown to prevent fibroblast invasion, most likely mediated by the prostaglandin EP2 receptor and generation of cAMP. Additionally, Rho-associated protein kinase (ROCK) inhibitors prevented fibroblast invasion, possibly by inactivation of myosin II. Importantly, both Prostaglandins and ROCK inhibitors are potential treatment options shown to be effective in in vitro and in vivo models of fibrotic diseases. This validates the presented novel phenotypic screening approach for the evaluation of potential inhibitors and the identification of novel compounds with activity in diseases that are associated with fibroblast invasion.

Identification of agonists for a group of human odorant receptors

Olfaction plays a critical role in several aspects of the human life. Odorants are detected by hundreds of odorant receptors (ORs) which belong to the superfamily of G protein-coupled receptors. These receptors are expressed in the olfactory sensory neurons of the nose. The information provided by the activation of different combinations of ORs in the nose is transmitted to the brain, leading to odorant perception and emotional and behavioral responses. There are ~400 intact human ORs, and to date only a small percentage of these receptors (~10%) have known agonists. The determination of the specificity of the human ORs will contribute to a better understanding of how odorants are discriminated by the olfactory system. In this work, we aimed to identify human specific ORs, that is, ORs that are present in humans but absent from other species, and their corresponding agonists. To do this, we first selected 22 OR gene sequences from the human genome with no counterparts in the mouse, rat or dog genomes. Then we used a heterologous expression system to screen a subset of these human ORs against a panel of odorants of biological relevance, including foodborne aroma volatiles. We found that different types of odorants are able to activate some of these previously uncharacterized human ORs.

Dynamics and evolution of β-catenin-dependent Wnt signaling revealed through massively parallel clonogenic screening

Wnt/β-catenin signaling is of significant interest due to the roles it plays in regulating development, tissue regeneration and disease. Transcriptional reporters have been widely employed to study Wnt/β-catenin signal transduction in live cells and whole organisms and have been applied to understanding embryonic development, exploring oncogenesis and developing therapeutics. Polyclonal heterogeneity in reporter cell lines has historically been seen as a challenge to be overcome in the development of novel cell lines and reporter-based assays, and monoclonal reporter cell lines are commonly employed to reduce this variability. A375 cell lines infected with a reporter for Wnt/β-catenin signaling were screened over short (<6) and long (>25) generational timescales. To characterize phenotypic divergence over these time-scales, a microfabricated cell array-based screen was developed enabling characterization of 1119 clonal colonies in parallel. This screen revealed phenotypic divergence after <6 generations at a similar scale to that observed in monoclonal cell lines cultured for >25 generations. Not only were reporter dynamics observed to diverge widely, but monoclonal cell lines were observed with seemingly opposite signaling phenotypes. Additionally, these observations revealed a generational-dependent trend in Wnt signaling in A375 cells that provides insight into the pathway's mechanisms of positive feedback and self-inhibition.

A versatile system for USER cloning-based assembly of expression vectors for mammalian cell engineering

A new versatile mammalian vector system for protein production, cell biology analyses, and cell factory engineering was developed. The vector system applies the ligation-free uracil-excision based technique – USER cloning – to rapidly construct mammalian expression vectors of multiple DNA fragments and with maximum flexibility, both for choice of vector backbone and cargo. The vector system includes a set of basic vectors and a toolbox containing a multitude of DNA building blocks including promoters, terminators, selectable marker- and reporter genes, and sequences encoding an internal ribosome entry site, cellular localization signals and epitope- and purification tags. Building blocks in the toolbox can be easily combined as they contain defined and tested Flexible Assembly Sequence Tags, FASTs. USER cloning with FASTs allows rapid swaps of gene, promoter or selection marker in existing plasmids and simple construction of vectors encoding proteins, which are fused to fluorescence-, purification-, localization-, or epitope tags. The mammalian expression vector assembly platform currently allows for the assembly of up to seven fragments in a single cloning step with correct directionality and with a cloning efficiency above 90%. The functionality of basic vectors for FAST assembly was tested and validated by transient expression of fluorescent model proteins in CHO, U-2-OS and HEK293 cell lines. In this test, we included many of the most common vector elements for heterologous gene expression in mammalian cells, in addition the system is fully extendable by other users. The vector system is designed to facilitate high-throughput genome-scale studies of mammalian cells, such as the newly sequenced CHO cell lines, through the ability to rapidly generate high-fidelity assembly of customizable gene expression vectors.

Structure of stem cell growth factor R-spondin 1 in complex with the ectodomain of its receptor LGR5

Leucine-rich repeat-containing G protein-coupled receptors 4-6 (LGR4-LGR6) are receptors for R-spondins, potent Wnt agonists that exert profound trophic effects on Wnt-driven stem cells compartments. We present crystal structures of a signaling-competent fragment of R-spondin 1 (Rspo1) at a resolution of 2.0 Å and its complex with the LGR5 ectodomain at a resolution of 3.2 Å. Ecto-LGR5 binds Rspo1 at its concave leucine-rich-repeat (LRR) surface, forming a dimeric 2:2 complex. Fully conserved residues on LGR4-LGR6 explain promiscuous binding of R-spondins. A phenylalanine clamp formed by Rspo1 Phe106 and Phe110 pinches Ala190 of LGR5 and is critical for binding. Mutations related to congenital anonychia reduce signaling, but not binding of Rspo1 to LGR5. Furthermore, antibody binding to the extended loop of the C-terminal LRR cap of LGR5 activates signaling in a ligand-independent manner. Thus, our data reveal binding of R-spondins to conserved sites on LGR4-LGR6 and, in analogy to FSHR and related receptors, suggest a direct signaling role for LGR4-LGR6 in addition to its formation of Wnt receptor and coreceptor complexes.

A novel truncated glucagon-like peptide 2 (GLP-2) as a tool for analyzing GLP-2 receptor agonists

Glucagon-like peptide 2 (GLP-2) is an intestinotropic peptide that binds to GLP-2 receptor (GLP-2R), a class-B G protein-coupled receptor. The GLP-2R antagonist GLP-2(3-33) has relatively high partial agonistic activity, and there are as yet no ideal known potent GLP-2R antagonists. We therefore prepared several truncated forms of human GLP-2 and characterized them by binding and reporter assays to find antagonists more potent than GLP-2(3-33). We found that GLP-2(11-33) was the most potent orthosteric GLP-2R antagonist, with binding activity almost equal to those of GLP-2 and GLP-2(3-33) and weaker intrinsic agonistic activity than GLP-2(3-33). GLP-2(11-33) retained weak agonistic activity toward human, cynomolgus monkey, dog, and Syrian hamster GLP-2Rs. However, it had no agonistic activity toward rat GLP-2R. GLP-2(11-33) potentiated the agonistic activity of an ago-allosteric modulator of GLP-2R, compound 1 (N-[1-(2,5-dichlorothiophen-3-yl)-2-(phenylsulfanyl)ethylidene]hydroxylamine), synergistically toward human GLP-2R. In the case of rat GLP-2R, GLP-2(11-33) decreased the agonistic activity of compound 1, although GLP-2 and GLP-2(3-33) increased this activity additively. These findings suggest that the binding sites of the ago-allosteric modulator and GLP-2 overlap, at least in rat GLP-2R. GLP-2(11-33) is a novel, useful tool for analyzing the mode of action of agonists and ago-allosteric modulators of GLP-2R.

Structures of Wnt-antagonist ZNRF3 and its complex with R-spondin 1 and implications for signaling

Zinc RING finger 3 (ZNRF3) and its homolog RING finger 43 (RNF43) antagonize Wnt signaling in adult stem cells by ubiquitinating Frizzled receptors (FZD), which leads to endocytosis of the Wnt receptor. Conversely, binding of ZNRF3/RNF43 to LGR4-6 – R-spondin blocks Frizzled ubiquitination and enhances Wnt signaling. Here, we present crystal structures of the ZNRF3 ectodomain and its complex with R-spondin 1 (RSPO1). ZNRF3 binds RSPO1 and LGR5-RSPO1 with micromolar affinity via RSPO1 furin-like 1 (Fu1) domain. Anonychia-related mutations in RSPO4 support the importance of the observed interface. The ZNRF3-RSPO1 structure resembles that of LGR5-RSPO1-RNF43, though Fu2 of RSPO1 is variably oriented. The ZNRF3-binding site overlaps with trans-interactions observed in 2:2 LGR5-RSPO1 complexes, thus binding of ZNRF3/RNF43 would disrupt such an arrangement. Sequence conservation suggests a single ligand-binding site on ZNRF3, consistent with the proposed competing binding role of ZNRF3/RNF43 in Wnt signaling.

Nicotinic acid and DP1 blockade: studies in mouse models of atherosclerosis

The use of nicotinic acid to treat dyslipidemia is limited by induction of a "flushing" response, mediated in part by the interaction of prostaglandin D(2) (PGD(2)) with its G-protein coupled receptor, DP1 (Ptgdr). The impact of DP1 blockade (genetic or pharmacologic) was assessed in experimental murine models of atherosclerosis. In Ptgdr(-/-)ApoE(-/-) mice versus ApoE(-/-) mice, both fed a high-fat diet, aortic cholesterol content was modestly higher (1.3- to 1.5-fold, P < 0.05) in Ptgdr(-/-)ApoE(-/-) mice at 16 and 24 weeks of age, but not at 32 weeks. In multiple ApoE(-/-) mouse studies, a DP1-specific antagonist, L-655, generally had a neutral to beneficial effect on aortic lipids in the presence or absence of nicotinic acid treatment. In a separate study, a modest increase in some atherosclerotic measures was observed with L-655 treatment in Ldlr(-/-) mice fed a high-fat diet for 8 weeks; however, this effect was not sustained for 16 or 24 weeks. In the same study, treatment with nicotinic acid alone generally decreased plasma and/or aortic lipids, and addition of L-655 did not negate those beneficial effects. These studies demonstrate that inhibition of DP1, with or without nicotinic acid treatment, does not lead to consistent or sustained effects on plaque burden in mouse atherosclerotic models.

Reprogrammed cell delivery for personalized medicine

In most approaches, personalized medicine requires time- and cost-intensive characterization of an individual's genetic background in order to achieve the best-adapted therapy. For this purpose, cell-based drug delivery offers a promising alternative. In particular, synthetic biology has introduced the vision of cells being programmable therapeutic production facilities that can be introduced into patients. This review highlights the progress made in synthetic biology-based cell engineering toward advanced drug delivery entities. Starting from basic one-input responsive transcriptional or post-transcriptional gene control systems, the field has reached a level on which cells can be engineered to detect cancer cells, to obtain control over T-cell proliferation, and to restore blood glucose homeostasis upon blue light illumination. Furthermore, a cellular implant was developed that detects blood urate level disorders and acts accordingly to restore homeostasis while another cellular implant was engineered as an artificial insemination device that releases bull sperm into bovine ovarian only during ovulation time by recording endogenous luteinizing hormone levels. Soon, the field will reach a stage at which cells can be reprogrammed to detect multiple metabolic parameters and self-sufficiently treat any disorder connected to them.

Biogenic amines and the control of neuromuscular signaling in schistosomes

Biogenic amines are small cationic monoamines that function broadly as neurotransmitters and/or neuromodulators in every animal phylum. They include such ubiquitous substances as serotonin, dopamine and invertebrate-specific phenolamines (tyramine, octopamine), among others. Biogenic amines are important neuroactive agents in all the flatworms, including blood flukes of the genus Schistosoma, the etiological agents of human schistosomiasis. A large body of evidence spanning nearly five decades identifies biogenic amines as major modulators of neuromuscular function in schistosomes, controlling movement, attachment to the host and other fundamental behaviors. Recent advances in schistosome genomics have made it possible to dissect the molecular mechanisms responsible for these effects and to identify the proteins involved. These efforts have already provided important new information about the mode of action of amine transmitters in the parasite. Moreover, these advances are continuing, as the field moves into a post-genomics era, and new molecular tools for gene and protein analysis are becoming available. Here, we review the current status of this research and discuss future prospects. In particular, we focus our attention on the receptors that mediate biogenic amine activity, their structural characteristics, functional properties and "druggability" potential. One of the themes that will emerge from this discussion is that schistosomes have a rich diversity of aminergic receptors, many of which share little sequence homology with those of the human host, making them ideally suited for selective drug targeting. Strategies for the characterization of these important parasite proteins will be discussed.

cAMP and IP3 signaling pathways in HEK293 cells transfected with canine olfactory receptor genes

Olfactory receptors (ORs) expressed at the cell surface of olfactory sensory neurons lining the olfactory epithelium are the first actors of events leading to odor perception and recognition. As for other mammalian ORs, few dog OR have been deorphanized, mainly because of the absence of good methodology and the difficulties encountered to express ORs at the cell surface. Within this work, our aim was 1) to deorphanize a large subset of dog OR and 2) to compare the implication of the 2 main pathways, namely the cAMP and inositol 1,4,5-triphosphate (IP3) pathways, in the transduction of the olfactory message. For this, we used 2 independent tests to assess the importance of each of these 2 pathways and analyzed the responses of 47 canine family 6 ORs to a number of aliphatic compounds. We found these ORs globally capable of inducing intracellular calcium elevation through the IP3 pathway as confirmed by the use of specific inhibitors and/or a cAMP increase in response to aldehyde exposure. We showed that the implication of the cAMP or/and IP3 pathway was dependent upon the ligand-receptor combination rather than on one or the other partner. Finally, by exposing OR-expressing cells to the 21 possible pairs of C6-C12 aliphatic aldehydes, we confirmed that some odorant pairs may have an inhibitory or additive effect. Altogether, these results reinforce the notion that odorant receptor subfamilies may constitute functional units and call for a more systematic use of 2 complementary tests interrogating the cAMP and IP3 pathways when deorphanizing ORs.

SEAP expression in transiently transfected mammalian cells grown in serum-free suspension culture

A transient transfection process was established using a novel 'in-house' developed transfection reagent, Ro-1539. It allows rapid production of large quantities of various recombinant proteins. Here we describe the transient expression of the secreted human placental alkaline phosphatase (SEAP) by HEK293EBNA and CHO cells in serum-free suspension culture. Unexpectedly, high expression levels of SEAP (150 mug/ml) were found 3-4 days post-transfection when placental alkaline phosphatase (AP) was used as the reference enzyme. To confirm these data, an SDS-PAGE analysis was performed and the visible SEAP protein band (MW of 65 kDa) was compared with co-migrated purified placental AP protein as reference. The scanning analysis of the gel showed that SEAP, a truncated form of AP, has a higher specific activity than the purified placental AP. A correction factor was introduced permitting a direct comparison of placental AP activity with the expression levels of SEAP. Scale-up of the transfection system from spinner flask to bioreactor was simple and straightforward, resulting in similar yields of SEAP. Finally, the effectiveness of Ro-1539 was compared to that of other transfection reagents.

International Union of Basic and Clinical Pharmacology. LXXXIII: classification of prostanoid receptors, updating 15 years of progress

It is now more than 15 years since the molecular structures of the major prostanoid receptors were elucidated. Since then, substantial progress has been achieved with respect to distribution and function, signal transduction mechanisms, and the design of agonists and antagonists (http://www.iuphar-db.org/DATABASE/FamilyIntroductionForward?familyId=58). This review systematically details these advances. More recent developments in prostanoid receptor research are included. The DP(2) receptor, also termed CRTH2, has little structural resemblance to DP(1) and other receptors described in the original prostanoid receptor classification. DP(2) receptors are more closely related to chemoattractant receptors. Prostanoid receptors have also been found to heterodimerize with other prostanoid receptor subtypes and nonprostanoids. This may extend signal transduction pathways and create new ligand recognition sites: prostacyclin/thromboxane A(2) heterodimeric receptors for 8-epi-prostaglandin E(2), wild-type/alternative (alt4) heterodimers for the prostaglandin FP receptor for bimatoprost and the prostamides. It is anticipated that the 15 years of research progress described herein will lead to novel therapeutic entities.

Isolation and identification of cucurbitane-type triterpenoids with partial agonist/antagonist potential for estrogen receptors from Momordica charantia

This study aims at investigating the estrogenic activity and active cucurbitane-type triterpenoid compounds of bitter gourd (Momordica charantia, MC) using a transactivation assay for estrogen receptors (ER) α and β. The lyophilized fruits of MC were exhaustively extracted with ethyl acetate (EA) and 95% ethanol (EtOH), sequentially. The nonsaponifiable fraction (NS) of the EA extract as well as the acid hydrolyzed EtOH extract (AH) was fractionated and isolated by repeated column chromatography and further purified by preparative HPLC or RP-HPLC. One known compound, 5β,19-epoxycucurbita-6,24-diene-3β,23ξ-diol (6), was isolated from the NS, and five new compounds (1-5) were isolated from AH and identified as cucurbita-6,22(E),24-trien-3β-ol-19,5β-olide (1), 5β,19-epoxycucurbita-6,22(E),24-triene-3β,19-diol (2), 3β-hydroxycucurbita-5(10),6,22(E),24-tetraen-19-al (3), 19-dimethoxycucurbita-5(10),6,22(E),24-tetraen-3β-ol (4), and 19-nor-cucurbita-5(10),6,8,22(E),24-pentaen-3β-ol (5). In the noncytotoxic concentration range, compounds 1, 2, 5 and 6 showed weak agonistic activity via ER α and β. Compounds 1, 2, 3 and 6 significantly antagonized the transactvation of 17β-estradiol (E(2)) via both ER α and β. In conclusion, this study demonstrates, for the first time as far as we know, the partial agonist/antagonist activity via ER of four new and one known cucurbitane-type triterpenoids from MC. Further studies are worthy to explore the selective estrogen receptor modulator (SERM) activity of MC.

Recent developments of biological reporter technology for detecting gene expression

Reporter gene assay is an invaluable tool for both biomedical and pharmaceutical researches to monitor cellular events associated with gene expression, regulation and signal transduction. On the basis of the alternations in reporter gene activities mediated by attaching response elements to these reporter genes, one sensitive, reliable and convenient assay can be provided to efficiently report the activation of particular messenger cascades and their effects on gene expression and regulations inside cells or living subjects. In this review, we introduce the current status of several commonly used reporter genes such as chloramphenicol acetyltransferase (CAT), alkaline phosphatase (AP), β-galactosidase (β-gal), luciferases, green fluorescent protein (GFP), and β-lactamase. Their applications in monitoring gene expression and regulations in vitro and in vivo will be summarized. With the development of advanced technology in gene expression and optical imaging modalities, reporter genes will become increasingly important in real-time detection of the gene expression at the single-cell level. This synergy will make it possible to understand the molecular basis of diseases, track the effectiveness of pharmaceuticals, monitor the response to therapies and evaluate the development process of new drugs.

Tissue distribution and elimination of estrogenic and anti-inflammatory catechol metabolites from sesaminol triglucoside in rats

Sesaminol triglucoside (STG) is the main sesame (Sesamum indicum L.) lignan. Like many other plant lignans, STG can be converted to the mammalian lignans by intestinal microbiota. The objectives of the present study were to investigate the distribution of STG metabolite in rats, and the effects of STG and its metabolite on in vitro inflammation and estrogenic activities. STG was metabolized via intestinal microflora to a biologically active catechol moiety which would then be absorbed into the body in rats. After oral administration of STG to Sprague-Dawley rats, the concentrations of major STG metabolites in rectum, cecum, colon, and small intestines are higher than those in liver, lung, kidney, and heart. Its concentration in brain is low but detectable. The present study demonstrates that STG may be metabolized to form the catechol metabolites first by intestinal microflora and then incorporated via intestine absorption into the cardiovascular system and transported to other tissues. Results showed that the catechol metabolites were found to be able to penetrate the tail end of intestines (large intestine) and go through urinary excretion. STG metabolites significantly reduced the production of IL-6 and TNF-alpha in RAW264.7 murine macrophages stimulated with lipopolysaccharide. The estrogenic activities of STG metabolites were also established by ligand-dependent transcriptional activation through estrogen receptors. This study clearly shows that STG has anti-inflammatory and estrogenic activities via metabolism of intestinal microflora.

Neuronal signaling in schistosomes: current status and prospects for postgenomicsThe present review is one of a series of occasional review articles that have been invited by the Editors and will feature the broad range of disciplines and expertise represented in our Editorial Advisory Board

Parasitic platyhelminths of the genus Schistosoma Weinland, 1858 (Trematoda, Digenea) are the etiological agents of human schistosomiasis, one of the most prevalent and debilitating parasitic diseases worldwide. Praziquantel is the only drug treatment available in most parts of the world and the effectiveness of the drug is threatened by the prospect of drug resistance. There is a pressing need to learn more about the basic biology of this organism and to identify molecular targets for new therapeutic drugs. The nervous system of schistosomes coordinates many activities that are essential for parasite survival, and as such is an attractive target for chemotherapeutic intervention. Until recently, very little was known about the molecular mechanisms of neuronal signaling in these organisms, but this is rapidly changing following the completion of the genome sequence and several recent developments in schistosome transgenesis and gene silencing. Here we review the current status of schistosome neurobiology and discuss prospects for future research as the field moves into a postgenomics era. One of the themes that will emerge from this discussion is that schistosomes have a rich diversity of neurotransmitters and receptors, indicating a more sophisticated system of neuronal communication than might be expected of a parasitic flatworm. Moreover, many of these transmitter receptors share little sequence homology with those of the human host, making them ideally suited for selective drug targeting. Strategies for characterization of these important parasite proteins will be discussed.

Ric-8A, a Galpha protein guanine nucleotide exchange factor potentiates taste receptor signaling

Taste receptors for sweet, bitter and umami tastants are G-protein-coupled receptors (GPCRs). While much effort has been devoted to understanding G-protein-receptor interactions and identifying the components of the signalling cascade downstream of these receptors, at the level of the G-protein the modulation of receptor signal transduction remains relatively unexplored. In this regard a taste-specific regulator of G-protein signaling (RGS), RGS21, has recently been identified. To study whether guanine nucleotide exchange factors (GEFs) are involved in the transduction of the signal downstream of the taste GPCRs we investigated the expression of Ric-8A and Ric-8B in mouse taste cells and their interaction with G-protein subunits found in taste buds. Mammalian Ric-8 proteins were initially identified as potent GEFs for a range of Gα subunits and Ric-8B has recently been shown to amplify olfactory signal transduction. We find that both Ric-8A and Ric-8B are expressed in a large portion of taste bud cells and that most of these cells contain IP3R-3 a marker for sweet, umami and bitter taste receptor cells. Ric-8A interacts with Gα-gustducin and Gαi2 through which it amplifies the signal transduction of hTas2R16, a receptor for bitter compounds. Overall, these findings are consistent with a role for Ric-8 in mammalian taste signal transduction.

Functional expression of chemoreceptors with the help of a Guanine nucleotide exchange factor

Odorant receptors and other chemoreceptors are usually poorly expressed in the plasma membrane of heterologous cells. A key point of regulation in G protein-mediated signaling is the interconversion between the active GTP-bound and inactive GDP-bound states of the Galpha subunit, which regulatory proteins, such as guanine nucleotide exchange factors (GEFs), can control. GEFs stimulate formation of the GTP-bound state of Galpha and therefore are considered to work as positive regulators of G protein-coupled receptor signaling. Ric-8B, a GEF that is specifically expressed in olfactory sensory neurons, promotes functional expression of odorant receptors in HEK293T cells because it amplifies the initially low receptor signaling through Galphaolf. This same strategy could be used to functionally express other types of chemoreceptors.

Prostanoid receptor antagonists: development strategies and therapeutic applications

Identification of the primary products of cyclo-oxygenase (COX)/prostaglandin synthase(s), which occurred between 1958 and 1976, was followed by a classification system for prostanoid receptors (DP, EP(1), EP(2) ...) based mainly on the pharmacological actions of natural and synthetic agonists and a few antagonists. The design of potent selective antagonists was rapid for certain prostanoid receptors (EP(1), TP), slow for others (FP, IP) and has yet to be achieved in certain cases (EP(2)). While some antagonists are structurally related to the natural agonist, most recent compounds are 'non-prostanoid' (often acyl-sulphonamides) and have emerged from high-throughput screening of compound libraries, made possible by the development of (functional) assays involving single recombinant prostanoid receptors. Selective antagonists have been crucial to defining the roles of PGD(2) (acting on DP(1) and DP(2) receptors) and PGE(2) (on EP(1) and EP(4) receptors) in various inflammatory conditions; there are clear opportunities for therapeutic intervention. The vast endeavour on TP (thromboxane) antagonists is considered in relation to their limited pharmaceutical success in the cardiovascular area. Correspondingly, the clinical utility of IP (prostacyclin) antagonists is assessed in relation to the cloud hanging over the long-term safety of selective COX-2 inhibitors. Aspirin apart, COX inhibitors broadly suppress all prostanoid pathways, while high selectivity has been a major goal in receptor antagonist development; more targeted therapy may require an intermediate position with defined antagonist selectivity profiles. This review is intended to provide overviews of each antagonist class (including prostamide antagonists), covering major development strategies and current and potential clinical usage.

Structural evidence for a sequential release mechanism for activation of heterotrimeric G proteins

Heptahelical G-protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptors couple to heterotrimeric G proteins to relay extracellular signals to intracellular signaling networks, but the molecular mechanism underlying guanosine 5'-diphosphate (GDP) release by the G protein alpha-subunit is not well understood. Amino acid substitutions in the conserved alpha5 helix of G(i), which extends from the C-terminal region to the nucleotide-binding pocket, cause dramatic increases in basal (receptor-independent) GDP release rates. For example, mutant Galpha(i1)-T329A shows an 18-fold increase in basal GDP release rate and, when expressed in culture, it causes a significant decrease in forskolin-stimulated cAMP accumulation. The crystal structure of Galpha(i1)-T329A.GDP shows substantial conformational rearrangement of the switch I region and additional striking alterations of side chains lining the catalytic pocket that disrupt the Mg(+2) coordination sphere and dislodge bound Mg(+2). We propose a "sequential release" mechanism whereby a transient conformational change in the alpha5 helix alters switch I to induce GDP release. Interestingly, this mechanistic model for heterotrimeric G protein activation is similar to that suggested for the activation of the plant small G protein Rop4 by RopGEF8.

Identification of anti-asthmatic compounds in Pericarpium citri reticulatae and evaluation of their synergistic effects

AIM

To investigate the anti-asthmatic mechanisms of the traditional Chinese medicine Pericarpium citri reticulatae (PCR).

METHODS

The alkaloid section (AS) of PCR was extracted using an ion exchange resin, separated, and purified into different fractions by semi-preparative HPLC. These fractions were screened for beta2-adrenergic receptor (beta(2)AR) agonistic activity using rat beta(2)AR-transfected CHO-CRE-EGFP cells. AS and its isolated components were characterized by ultra-performance liquid chromatography/quadrupole time-of-flight MS (UPLC/Q-Tof MS) and were evaluated for their spasmolytic and antitussive activities both in vitro and in vivo in a guinea pig model.

RESULTS

We demonstrated that the AS component responsible for activating beta(2)AR signaling was synephrine. Both AS and synephrine showed significant spasmolytic effects on acetylcholine chloride (ACh)-induced contractions in isolated guinea pig trachea, and they protected against histamine-induced experimental asthma by prolonging the latent period. We further identified stachydrine as the antitussive component that could significantly reduce citric acid-induced coughing. The combination of these two bioactive compounds had a more potent spasmolytic activity in comparison with the single use of synephrine or stachydrine.

CONCLUSION

We conclude that synephrine and stachydrine are the key components of AS that mediate asthma relief due to their synergism when used in combination.

Bioactivity-based screening of antibiotics and hormones

Bioactivity-based screening methods are relatively cheap, quick and easy to use tools. Especially with respect to antimicrobial residues and compounds with hormonal activity, they form a very cost-effective alternative to physical chemical methods in large-scale surveillance and monitoring programs, where their main purpose is to identify samples that require additional chemical confirmation. A major advantage is their intrinsic capability to detect unknown compounds and new hazards. This review shows an overview of the available methods and their potential and limitations for regulatory control.

High-throughput screening for analysis of in vitro toxicity

The influence of combinatorial chemistry and high-throughput screening (HTS) technologies in the pharmaceutical industry during the last 10 years has been enormous. However, the attrition rate of drugs in the clinic due to toxicity during this period still remained 40-50%. The need for reduced toxicity failure led to the development of early toxicity screening assays. This chapter describes the state of the art for assays in the area of genotoxicity, cytotoxicity, carcinogenicity, induction of specific enzymes from phase I and II metabolism, competition assays for enzymes of phase I and II metabolism, embryotoxicity as well as endocrine disruption and reprotoxicity. With respect to genotoxicity, the full Ames, Ames II, Vitotox, GreenScreen GC, RadarScreen, and non-genotoxic carcinogenicity assays are discussed. For cytotoxicity, cellular proliferation, calcein uptake, oxygen consumption, mitochondrial activity, radical formation, glutathione depletion as well as apoptosis are described. For high-content screening (HCS), the possibilities for analysis of cytotoxicity, micronuclei, centrosome formation and phospholipidosis are examined. For embryotoxicity, endocrine disruption and reprotoxicity alternative assays are reviewed for fast track analysis by means of nuclear receptors and membrane receptors. Moreover, solutions for analyzing enzyme induction by activation of nuclear receptors, like AhR, CAR, PXR, PPAR, FXR, LXR, TR and RAR are given.

Identification of higenamine in Radix Aconiti Lateralis Preparata as a beta2-adrenergic receptor agonist1

AIM

To screen beta2-adrenergic receptor (beta2-AR) agonists from Radix Aconiti Lateralis Preparata (RALP) as potential drug leads for asthma using a sensitive cell-based agonist assay.

METHODS

The beta2-AR gene was stably expressed by Chinese hamster ovary (CHO) cells also stably expressing a cyclic adenosine monophosphate (AMP) response element-linked enhanced green fluorescent protein reporter gene. The cells were used to screen agonists from high-performance liquid chromatographic fractions of an extract of RALP. The fraction with the highest activity was selected for further compound isolation and the study of the structure-activity relationship. Its active compound was further identified by chromatography and mass spectrometry.

RESULTS

Bioactivity-directed fractionation of the crude extract of RALP led to the isolation and characterization of the effective compound, namely hignamine. It could dose-dependently relax the isolated guinea pig trachea strip precontraction with acetylcholine with EC(50) value of (2.60+/-0.36)x10(-5) mol/L. Further in vivo studies also displayed that hignamine could protect experimental asthma model induced by histamine in guinea pigs to prolong the latent periods of asthma.

CONCLUSION

Hignamine, as a beta2-AR agonist existing in the extract of RALP, is the key compound contributing to the successful relief of the bronchoconstriction.

Attenuating pregnane X receptor (PXR) activation: A molecular modelling approach

Recent studies have demonstrated that the pregnane X receptor (PXR) is a key regulator of cytochromes P450 3A (e.g. CYP3A4 in human) gene expression. As a result, activation of PXR may lead to CYP3A4 protein over-expression. Because induction of CYP3A4 could result in clinically important drug drug interactions, there has been a great interest in reducing the possibility of PXR activation by drug candidates in drug-discovery programmes. In order to provide structural insight for attenuating drug candidate-mediated PXR activation, we used a docking approach to study the structure activity relationship for PXR activators. Based on our docking models, it is proposed that introducing polar groups to the end of an activator should reduce its human PXR (hPXR) activity via destabilizing interactions in the hydrophobic areas of the PXR ligand-binding pocket. A number of analogues that incorporate these structural features then were designed and synthesized, and they exhibited significantly lower hPXR activation in a transactivation assay and decreased CYP3A4 induction in a human hepatocytes-based assay. In addition, an example in which attenuating hPXR activation was achieved by sterically destabilizing the helices 11 and 12 of the receptor is presented.

Stable high volumetric production of glycosylated human recombinant IFNalpha2b in HEK293 cells

Background

Mammalian cells are becoming the prevailing expression system for the production of recombinant proteins because of their capacity for proper protein folding, assembly, and post-translational modifications. These systems currently allow high volumetric production of monoclonal recombinant antibodies in the range of grams per litre. However their use for large-scale expression of cytokines typically results in much lower volumetric productivity.

Results

We have engineered a HEK293 cell clone for high level production of human recombinant glycosylated IFNα2b and developed a rapid and efficient method for its purification. This clone steadily produces more than 200 mg (up to 333 mg) of human recombinant IFNα2b per liter of serum-free culture, which can be purified by a single-step cation-exchange chromatography following media acidification and clarification. This rapid procedure yields 98% pure IFNα2b with a recovery greater than 70%. Purified IFNα2b migrates on SDS-PAGE as two species, a major 21 kDa band and a minor 19 kDa band. N-terminal sequences of both forms are identical and correspond to the expected mature protein. Purified IFNα2b elutes at neutral pH as a single peak with an apparent molecular weight of 44,000 Da as determined by size-exclusion chromatography. The presence of intramolecular and absence of intermolecular disulfide bridges is evidenced by the fact that non-reduced IFNα2b has a greater electrophoretic mobility than the reduced form. Treatment of purified IFNα2b with neuraminidase followed by O-glycosidase both increases electrophoretic mobility, indicating the presence of sialylated O-linked glycan. A detailed analysis of glycosylation by mass spectroscopy identifies disialylated and monosialylated forms as the major constituents of purified IFNα2b. Electron transfer dissociation (ETD) shows that the glycans are linked to the expected threonine at position 106. Other minor glycosylated forms and non-sialylated species are also detected, similar to IFNα2b produced naturally by lymphocytes. Further, the HEK293-produced IFNα2b is biologically active as shown with reporter gene and antiviral assays.

Conclusion

These results show that the HEK293 cell line is an efficient and valuable host for the production of biologically active and glycosylated human IFNα2b.

Identification of LDL-receptor transcription stimulating peptides from soybean hydrolysate in human hepatocytes

Soybean protein and its hydrolysate have been reported to have cholesterol-lowering property, but the responsible components are still largely unknown. In previous study, we found that soybean protein hydrolysate (SPH) prepared with the protease from Bacillus amyloliquefaciens FSE-68, strongly stimulates transcription of low density lipoprotein receptor (LDL-R). To identify LDL-R transcription stimulating peptides in human hepatocytes, the SPH was fractionated with gel permeation chromatograpy and the active fraction was further separated by using reverse-phase chromatography. Several peptides in the most active fraction were identified by LC/MS and MS/MS analysis. LDL-R transcription stimulating peptides were synthesized on the basis of identified sequences, and their effect on LDL-R transcription was tested in vitro. Among the synthesized peptides, Phe-Val-Val-Asn-Ala-Thr-Ser-Asn (FVVNATSN) showed the strongest activity, and LDL-R transcription of hepatic cells was increased to 248.8% (compared to 100% of untreated control) by FVVNATSN at a concentration of 100 microM. This study provides direct evidence that peptides derived from soybean protein can influence LDL-R transcription in hepatocytes.