GPR12 selections of the metabolites from an endophytic Streptomyces sp. associated with Cistanches deserticola

Exploring the chemical diversity of phytopathogenic fungi infecting edible fruits

Two fungi, Fusarium guttiforme and Colletotrichum horii, were cultured under different conditions to obtain fourteen compounds. The axenic cultures of F. guttiforme and C. horii in potato dextrose broth (PDB) medium yielded fusaric acid (1), 9,10-dehydrofusaric acid (2), and tyrosol, whereas their co-cultivation produced fusarinol (5), a fusaric acid complex with magnesium (3), 9,10-dehydrofusaric acid complex with magnesium (4), and 5-butyl-5-(hydroxymethyl) dihydrofuranone (9). Upon changing the medium from PDB to Czapek, different compounds (uracil, p-hydroxy acetophenone, and cyclo(L-Leu-L-Pro) were obtained. Fusaric acid (1) was biotransformed into fusarinol (5) by C. horii, suggesting a detoxification process, and three other compounds were obtained: 7-hydroxyfusarinol (7), 9,10-dehydrofusarinol (6), and fusarinyl acetate (8). Epigenetic modulation of suberohydroxamic acid against F. guttiforme afforded gibepyrone B (10). These compounds were subjected to a papain inhibition enzymatic assay; the highest inhibitory activity was displayed by the two magnesium complexes, at 56 and 54% inhibition, respectively.

Induction of New Aromatic Polyketides from the Marine Actinobacterium Streptomyces griseorubiginosus through an OSMAC Approach

Using the OSMAC (One Strain Many Compounds) approach, the actinobacterium Streptomyces griseorubiginosus, derived from an unidentified cnidarian collected from a reef near Pointe de Bellevue in Réunion Island (France), was subjected to cultivation under diverse conditions. This endeavour yielded the isolation of a repertoire of 23 secondary metabolites (1-23), wherein five compounds were unprecedented as natural products (19-23). Specifically, compounds 19 and 20 showcased novel anthrone backbones, while compound 23 displayed a distinctive tetralone structure. Additionally, compounds 21 and 22 presented an unusual naphtho [2,3-c]furan-4(9H)-one chromophore. Interestingly, the detection of all these novel compounds (19-23) was exclusively achieved when the bacterium was cultured in FA-1 liquid medium supplemented with the epigenetic modifier γ-butyrolactone. The elucidation of the structural features of the newfound compounds was accomplished through a combination of HRESIMS, 1D and 2D NMR spectroscopy, as well as QM-NMR (Quantum Mechanical-Nuclear Magnetic Resonance) methods and by comparison with existing literature. Moreover, the determination of the relative configuration of compound 23 was facilitated by employing the mix-J-DP4 computational approach.

Opportunities and challenges in drug discovery targeting the orphan receptor GPR12

G-protein-coupled receptor 12 (GPR12) is a brain-specific expression orphan G-protein-coupled receptor (oGPCR) that regulates various physiological processes. It is an emerging therapeutic target for central nervous system (CNS) disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), attention deficit hyperactivity disorder (ADHD), and schizophrenia, as well as other human diseases, such as cancer, obesity, and metabolic disorders. GPR12 remains a less extensively investigated oGPCR, particularly in terms of its biological functions, signaling pathways, and ligand discovery. The discovery of drug-like small-molecule modulators to probe the brain functions of GPR12 or to act as a potential drug candidates, as well as the identification of reliable biomarkers, are vital to elucidate the roles of this receptor in various human diseases and develop novel target-based therapeutics.

Production of antibacterial compounds using Bacillus spp. isolated from thermal springs in Saudi Arabia

Seventeen water samples were collected from four different thermal springs in Saudi Arabia. Microbiological assays were used to assess the antibacterial activities of bacterial colonies against antibiotic-resistant and susceptible-bacterial strains, and 16S rRNA gene sequencing was used to identify the genus and species of these antibiotic-producing bacteria. Chromatography and spectroscopy were used to separate the active compounds and help figuring out what their structures were. Four compounds were isolated using bacteria: N-acetyltryptamine (1), isovaleric acid (2), ethyl-4-ethoxybenzoate (3) and phenylacetic acid (4). Compounds 1, 2 and 4 were produced from Bacillus pumilus and 3 was from Bacillus licheniformis (AH-E1). The outcomes of the minimum inhibitory concentrations (MICs) showed that all pure compounds produced in this work had antibacterial activities against Gram-positive pathogens (between 128 mg/L and 512 mg/L compared to the control) and compound 2 had activity against E. coli.

Structural insight into the constitutive activity of human orphan receptor GPR12

G protein-coupled receptor 12 (GPR12) is an orphan G protein-coupled receptor that is highly expressed in the thalamus of the brain and plays a vital role in driving thalamocortical functions in short-term memory. GPR12 performs high constitutive activity and couples with Gs, increasing the intracellular cyclic adenosine monophosphate (cAMP) level when it is expressed. However, exploitation for drug development is limited since it is unclear how GPR12 initiates self-activation and signal transduction, and whether it can be modulated by endogenous or synthetic ligands. Here, we report the cryo-electron microscopy structure of the GPR12-Gs complex in the absence of agonists. Our structure reveals the key determinants for the intrinsically high basal activity of GPR12, including extracellular loop 2 partially occupying the orthosteric binding pocket, a tight-packed TM1 and TM7, and unique activation-related residues in TM6 and TM7. Together with mutagenesis data, this study will improve our understanding of the function and self-activation of the orphan receptor GPR12, enable the identification of endogenous ligands, and guide drug discovery efforts that target GPR12.

Truncatenolide, a Bioactive Disubstituted Nonenolide Produced by Colletotrichum truncatum, the Causal Agent of Anthracnose of Soybean in Argentina: Fungal Antagonism and SAR Studies

A bioactive disubstituted nonenolide, named truncatenolide, was produced by Colletotrichum truncatum, which was collected from infected tissues of soybean showing anthracnose symptoms in Argentina. This is a devastating disease that drastically reduces the yield of soybean production in the world. The fungus also produced a new trisubstituted oct-2-en-4-one, named truncatenone, and the well-known tyrosol and N-acetyltyramine. Truncatenolide and truncatenone were characterized by spectroscopic (essentially one-dimensional (1D) and two-dimensional (2D) ¹H and ¹³C NMR and HR ESIMS) and chemical methods as (5E,7R,10R)-7-hydroxy-10-methyl-3,4,7,8,9,10-hexahydro-2H-oxecin-2-one and (Z)-6-hydroxy-3,5-dimethyloct-2-en-4-one, respectively. The geometry of the double bond of truncatenolide was assigned by the value of olefinic proton coupling constant and that of truncatenone by the correlation observed in the corresponding NOESY spectrum. The relative configuration of each stereogenic center was assigned with the help of ¹³C chemical shift and ¹H-¹H scalar coupling DFT calculations, while the absolute configuration assignment of truncatenolide was performed by electronic circular dichroism (ECD). When tested on soybean seeds, truncatenolide showed the strongest phytotoxic activity. Tyrosol and N-acetyltyramine also showed phytotoxicity to a lesser extent, while truncatenone weakly stimulated the growth of the seed root in comparison to the control. When assayed against Macrophomina phaseolina and Cercospora nicotianae, other severe pathogens of soybean, truncatenolide showed significant activity against M. phaseolina and total inhibition of C. nicotianae. Thus, some other fungal nonenolides and their derivatives were assayed for their antifungal activity against both fungi in comparison with truncatenolide. Pinolidoxin showed to a less extent antifungal activity against both fungi, while modiolide A selectively and totally inhibited only the growth of C. nicotianae. The SAR results and the potential of truncatenolide, modiolide A, and pinolidoxin as biofungicides were also discussed.

Endocannabinoid signaling pathways: beyond CB1R and CB2R

The search for cannabinoid receptors other than CB1R and CB2R has been ongoing for over a decade. A number of orphan receptors have been proposed as potential cannabinoid receptors primarily based on phylogenic arguments and reactivity towards known endocannabinoids and phytocannabinoids. Seven putative cannabinoid receptors are described and discussed, and evidence for and against their inclusion in this category are presented.

Neuroprotective Effect of Protaetia brevitarsis seulensis' Water Extract on Trimethyltin-Induced Seizures and Hippocampal Neurodegeneration

This study aimed to investigate whether the Protaetia brevitarsis seulensis (PB)’ water extract (PBWE) ameliorates trimethyltin (TMT)-induced seizures and hippocampal neurodegeneration. To investigate the potential neuroprotective effect of the PBWE in vitro, a lactate dehydrogenase (LDH) assay was conducted in TMT-treated primary cultures of mouse hippocampal neurons. In TMT-treated adult C57BL/6 mice, behavioral and histopathological changes were evaluated by seizure scoring and Fluoro-Jade C staining, respectively. In our in vitro assay, we observed that pretreating mice hippocampal neuron cultures with the PBWE reduced TMT-induced cytotoxicity, as indicated by the decreased LDH release. Furthermore, pretreatment with the PBWE alleviated seizures and hippocampal neurodegeneration in TMT-treated mice. The antioxidant activity of the PBWE increased in a dose-dependent manner; moreover, pretreatment with the PBWE mitigated the TMT-induced Nrf2 stimulation. In addition, six major compounds, including adenine, hypoxanthine, uridine, adenosine, inosine, and benzoic acid, were isolated from the PBWE, and among them, inosine and benzoic acid have been confirmed to have an essential antioxidative activity. In conclusion, the PBWE ameliorated TMT-induced toxicity in hippocampal neurons in both in vitro and in vivo assays, through a potential antioxidative effect. Our findings suggest that the PBWE may have pharmacotherapeutic potential in neurodegenerative diseases such as seizures or epilepsy.

Diverse endophytic Streptomyces species with dynamic metabolites and their meritorious applications: a critical review

The strains of actinobacteria are unique as they lie between true fungi and bacteria and several of them were reported as endophytic actinobacteria as they were isolated from the inner regions of various plant parts and will enhance uptake of nutrients and improve defense against pathogens. Literature and scientific communications reported the relationship between the endophytes and plants, most of them concluded the association as commensalism. Remarkably, bioactive compounds from endophytic Streptomyces sp. were confirmed with various applications. A retrospective consolidation on the endophytic Streptomyces sp. and their metabolite application in day to day life is presented here. It was deduced that this group of the organism are a source for a wide range of bioactive compounds including anticancer agents, immune suppressor, plant growth promoters, anti-inflammatory agents, anti-tumor agents, enzymes and antimicrobial substances. These antimicrobial metabolites show broad-spectrum activity and are effective against bacteria and fungi. The mechanism of action of secondary metabolites from endophytes and its positive influence on the host plants are noted as involvement in deterrence, antifeedant activity, toxicity against common pests, and as enhancers for physical mechanisms such as water uptake and sunlight absorption, thus supporting the growth of host plants.

Advances in Neurobiology and Pharmacology of GPR12

GPR12 is a G protein-coupled orphan receptor genetically related to type 1 and type 2 cannabinoid receptors (CB₁ and CB₂) which are ancient proteins expressed all over the body. Both cannabinoid receptors, but especially CB₁, are involved in neurodevelopment and cognitive processes such as learning, memory, brain reward, coordination, etc. GPR12 shares with CB₁ that both are mainly expressed into the brain. Regrettably, very little is known about physiology of GPR12. Concerning its pharmacology, GPR12 seems to be endogenously activated by the lysophospholipids sphingosine-1-phosphate (S1P) and sphingosyl-phosphorylcholine (SPC). Exogenously, GPR12 is a target for the phytocannabinoid cannabidiol (CBD). Functionally, GPR12 seems to be related to neurogenesis and neural inflammation, but its relationship with cognitive functions remains to be characterized. Although GPR12 was initially suggested to be a cannabinoid receptor, it does not meet the five criteria proposed in 2010 by the International Union of Basic and Clinical Pharmacology (IUPHAR). In this review, we analyze all the direct available information in PubMed database about expression, function, and pharmacology of this receptor in central nervous system (CNS) trying to provide a broad overview of its current and prospective neurophysiology. Moreover, in this mini-review we highlight the need to produce more relevant data about the functions of GPR12 in CNS. Hence, this work should motivate further research in this field.

Novel 1,3-Benzodioxole From Marine-Derived Actinomycete in East Vietnam Sea

Analysis of an antimicrobial extract from the culture broth of the marine-derived actinomycete Streptomyces sp. G261 led to the isolation of a new 1,3-benzodioxole derivative (1), together with 10 known compounds 2-11. The actinomycete strain G261 was isolated from sediment, collected at Cu Lao Cham, Quang Nam in Vietnam. The taxonomic identification of the strain G261 was achieved by analysis of 16SrRNA gene sequences. On the basis of morphological and phylogenetic evidence, the actinomycete strain G261 was assigned to the genus Streptomyces. The structures of the isolated compounds were established by their spectral data analysis, including mass spectrometry, 1-dimensional nuclear magnetic resonance (1D-NMR), and 2D-NMR. The structure of 1 was confirmed by comparison of the calculated with experimental13C NMR data. Compound 1 exhibited antimicrobial activity against Enterococcus faecalis and Staphylococcus aureus with minimum inhibitory concentration values of 128 and 256 µg/mL, respectively. Whereas, compound 1 had a weak inhibition when tested against 4 cancer cell lines, KB, LU-1, HepG-2, and MCF-7.

GPR3, GPR6, and GPR12 as novel molecular targets: their biological functions and interaction with cannabidiol

The G protein-coupled receptors 3, 6, and 12 (GPR3, GPR6, and GPR12) comprise a family of closely related orphan receptors with no confirmed endogenous ligands. These receptors are constitutively active and capable of signaling through G protein-mediated and non-G protein-mediated mechanisms. These orphan receptors have previously been reported to play important roles in many normal physiological functions and to be involved in a variety of pathological conditions. Although they are orphans, GPR3, GPR6, and GPR12 are phylogenetically most closely related to the cannabinoid receptors. Using β-arrestin2 recruitment and cAMP accumulation assays, we recently found that the nonpsychoactive phytocannabinoid cannabidiol (CBD) is an inverse agonist for GPR3, GPR6, and GPR12. This discovery highlights these orphan receptors as potential new molecular targets for CBD, provides novel mechanisms of action, and suggests new therapeutic uses of CBD for illnesses such as Alzheimer's disease, Parkinson's disease, cancer, and infertility. Furthermore, identification of CBD as a new inverse agonist for GPR3, GPR6, and GPR12 provides the initial chemical scaffolds upon which potent and efficacious agents acting on these receptors can be developed, with the goal of developing chemical tools for studying these orphan receptors and ultimately new therapeutic agents.

Towards a better understanding of the cannabinoid-related orphan receptors GPR3, GPR6, and GPR12

GPR3, GPR6, and GPR12 are three orphan receptors that belong to the Class A family of G-protein-coupled receptors (GPCRs). These GPCRs share over 60% of sequence similarity among them. Because of their close phylogenetic relationship, GPR3, GPR6, and GPR12 share a high percentage of homology with other lipid receptors such as the lysophospholipid and the cannabinoid receptors. On the basis of sequence similarities at key structural motifs, these orphan receptors have been related to the cannabinoid family. However, further experimental data are required to confirm this association. GPR3, GPR6, and GPR12 are predominantly expressed in mammalian brain. Their high constitutive activation of adenylyl cyclase triggers increases in cAMP levels similar in amplitude to fully activated GPCRs. This feature defines their physiological role under certain pathological conditions. In this review, we aim to summarize the knowledge attained so far on the understanding of these receptors. Expression patterns, pharmacology, physiopathological relevance, and molecules targeting GPR3, GPR6, and GPR12 will be analyzed herein. Interestingly, certain cannabinoid ligands have been reported to modulate these orphan receptors. The current debate about sphingolipids as putative endogenous ligands will also be addressed. A special focus will be on their potential role in the brain, particularly under neurological conditions such as Parkinson or Alzheimer's disease. Reported physiological roles outside the central nervous system will also be covered. This critical overview may contribute to a further comprehension of the physiopathological role of these orphan GPCRs, hopefully attracting more research towards a future therapeutic exploitation of these promising targets.

Two new compounds from a marine-derived Streptomyces sp

Two new long-chain unsaturated compounds, (2E, 6E)-10-methoxy-3,7-dimethyl-10-oxodeca-2,6-dienoic acid (1) and (2E, 6E)-3,7,11-trimethyldodeca-2,6-dienedioic acid (2), together with seven known compounds were isolated from a marine-derived Streptomyces sp. Their structures were determined by spectroscopic methods, including 2D NMR techniques. Compounds 1 and 2 were investigated for their antibacterial activities.

Microindolinone A, a Novel 4,5,6,7-Tetrahydroindole, from the Deep-Sea-Derived Actinomycete Microbacterium sp. MCCC 1A11207

A novel indole, microindolinone A (1), was isolated from a deep-sea-derived actinomycete Microbacterium sp. MCCC 1A11207, together with 18 known compounds (2-19). By detailed analysis of the ¹H, ¹³C, HSQC, COSY, HMBC, high resolution electron spray ionization mass spectrum (HRESIMS), and circular dichroism (CD) data, the absolute configuration of 1 was elucidated as 5R-hydroxy-4,5,6,7-tetrahydroindole-4-one. It is noteworthy that 1 is the second example of a saturated indole isolated from nature.

Diversity and bioprospecting of actinomycete endophytes from the medicinal plants

The endophytic actinomycetes constitute one of the fascinating group of microorganisms associated with a wide range of plant species. The diversity of actinomycetes in plants and their tissue parts is a matter of debate as no consensus are derived between individual studies. Nevertheless, their diversity correlates with the occurrence in plant species harboured in unique regions of biologically diverse areas called "hot spots." Recent advances in the isolation techniques have facilitated the isolation of rare taxa from these environments. The biosynthetic ability of the endophytic actinomycetes has proven beyond doubt that these organisms have the potential to synthesize an array of compounds with novelty in structure and bioactivity and as a result are preferred in the natural product screening programs. In the years to come, the scientific world may await to discover many more novel actinomycete taxa with metabolic diversity and applications in therapeutics.

SIGNIFICANCE AND IMPACT OF THE STUDY

"Endophytes" - the microbes residing in the living tissues of plants are virtually omnipresent. Actinomycete endophytes are diverse in distribution within plant tissues, especially in the roots as they have a close association with the rhizhosphere. An introspection into diversity studies necessitates careful sampling, analysis, and isolation data from the biodiverse and nonbiodiverse regions represented by unique environments. The key to the recovery of novel species and their bioprospection lies in these regions.

Neuro-psychopharmacological perspective of Orphan receptors of Rhodopsin (class A) family of G protein-coupled receptors

BACKGROUND

In the central nervous system (CNS), G protein-coupled receptors (GPCRs) are the most fruitful targets for neuropsychopharmacological drug development. Rhodopsin (class A) is the most studied class of GPCR and includes orphan receptors for which the endogenous ligand is not known or is unclear. Characterization of orphan GPCRs has proven to be challenging, and the production pace of GPCR-based drugs has been incredibly slow.

OBJECTIVE

Determination of the functions of these receptors may provide unexpected insight into physiological and neuropathological processes. Advances in various methods and techniques to investigate orphan receptors including in situ hybridization and knockdown/knockout (KD/KO) showed extensive expression of these receptors in the mammalian brain and unmasked their physiological and neuropathological roles. Due to these rapid progress and development, orphan GPCRs are rising as a new and promising class of drug targets for neurodegenerative diseases and psychiatric disorders.

CONCLUSION

This review presents a neuropsychopharmacological perspective of 26 orphan receptors of rhodopsin (class A) family, namely GPR3, GPR6, GPR12, GPR17, GPR26, GPR35, GPR39, GPR48, GPR49, GPR50, GPR52, GPR55, GPR61, GPR62, GPR63, GPR68, GPR75, GPR78, GPR83, GPR84, GPR85, GPR88, GPR153, GPR162, GPR171, and TAAR6. We discussed the expression of these receptors in mammalian brain and their physiological roles. Furthermore, we have briefly highlighted their roles in neurodegenerative diseases and psychiatric disorders including Alzheimer's disease, Parkinson's disease, neuroinflammation, inflammatory pain, bipolar and schizophrenic disorders, epilepsy, anxiety, and depression.

Endophytic actinobacteria of medicinal plants: diversity and bioactivity

Endophytes are the microorganisms that exist inside the plant tissues without having any negative impact on the host plant. Medicinal plants constitute the huge diversity of endophytic actinobacteria of economical importance. These microbes have huge potential to synthesis of numerous novel compounds that can be exploited in pharmaceutical, agricultural and other industries. It is of prime importance to focus the present research on practical utilization of this microbial group in order to find out the solutions to the problems related to health, environment and agriculture. An extensive characterization of diverse population of endophytic actinobacteria associated with medicinal plants can provide a greater insight into the plant-endophyte interactions and evolution of mutualism. In the present review, we have discussed the diversity of endophytic actinobacteria of from medicinal plants their multiple bioactivities.

Metabolic parameters and emotionality are little affected in G-protein coupled receptor 12 (Gpr12) mutant mice

Background

G-protein coupled receptors (GPR) bear the potential to serve as yet unidentified drug targets for psychiatric and metabolic disorders. GPR12 is of major interest given its putative role in metabolic function and its unique brain distribution, which suggests a role in emotionality and affect. We tested Gpr12 deficient mice in a series of metabolic and behavioural tests and subjected them to a well-established high-fat diet feeding protocol.

Methodology/Principal Findings

Comparing the mutant mice with wild type littermates, no significant differences were seen in body weight, fatness or weight gain induced by a high-fat diet. The Gpr12 mutant mice displayed a modest but significant lowering of energy expenditure and a trend to lower food intake on a chow diet, but no other metabolic parameters, including respiratory rate, were altered. No emotionality-related behaviours (assessed by light-dark box, tail suspension, and open field tests) were affected by the Gpr12 gene mutation.

Conclusions/Significance

Studying metabolic and emotionality parameters in Gpr12 mutant mice did not reveal a major phenotypic impact of the gene mutation. Compared to previous results showing a metabolic phenotype in Gpr12 mice with a mixed 129 and C57Bl6 background, we suggest that a more pure C57Bl/6 background due to further backcrossing might have reduced the phenotypic penetrance.