Mao D et al. (2017) Proc Natl Acad Sci U S A "Discovery of scmR as a global regulator of secondary metabolism and virulence in Burkholderia thailandensis E264."

Mao D, Moon K, Bushin LB, Seyedsayamdost MR, Wu Y

[Proc Natl Acad Sci U S A, 2017]

Bacteria produce a diverse array of secondary metabolites that have been invaluable in the clinic and in research. These metabolites are synthesized by dedicated biosynthetic gene clusters (BGCs), which assemble architecturally complex molecules from simple building blocks. The majority of BGCs in a given bacterium are not expressed under normal laboratory growth conditions, and our understanding of how they are silenced is in its infancy. Here, we have addressed this question in the Gram-negative model bacterium Burkholderia thailandensis E264 using genetic, transcriptomic, metabolomic, and chemical approaches. We report that a previously unknown, quorum-sensing-controlled LysR-type transcriptional regulator, which we name ScmR (for secondary metabolite regulator), serves as a global gatekeeper of secondary metabolism and a repressor of numerous BGCs. Transcriptionally, we find that 13 of the 20 BGCs in B. thailandensis are significantly (threefold or more) up- or down-regulated in a scmR deletion mutant (scmR) Metabolically, the scmR strain displays a hyperactive phenotype relative to wild type and overproduces a number of compound families by 18- to 210-fold, including the silent virulence factor malleilactone. Accordingly, the scmR mutant is hypervirulent both in vitro and in a Caenorhabditis elegans model in vivo. Aside from secondary metabolism, ScmR also represses biofilm formation and transcriptionally activates ATP synthesis and stress response. Collectively, our data suggest that ScmR is a pleiotropic regulator of secondary metabolism, virulence, biofilm formation, and other stationary phase processes. A model for how the interplay of ScmR with pathway-specific transcriptional regulators coordinately silences virulence factor production is proposed.

Weyler W (1992) Worm Breeder's Gazette "Evidence for Monoamine Oxidase in Caenorhabditis elegans"

Weyler W

[Worm Breeder's Gazette, 1992]

Monoamine oxidase A and B are mitochondrial outer membrane flavoproteins best characterized in higher vertebrates, and their association with the nervous system has led to the belief that their most important function is a role in neurotransmitter amine metabolism. In spite of extensive efforts to understand the role of these enzymes in the nervous system, little progress has been made. This is in part due to the inherent complexity of the systems studied. Because the nervous system of Caenorhabditis elegans is relatively simple and well defined, I decided to investigate if MAO is present in C elegans. The biogenic amines octopamine, serotonin, and dopamine, presumptive neurotransmitters in the worm, are all substrates of MAO. It is therefore reasonable to believe that MAO is present in C. elegans. Although first experiments to spectrophotometrically detect MAO activity failed, immunological studies of whole worm extracts indicated its presence. Homogenates were examined by SDS-PAGE and Western blot analysis with sheep anti-human MAO A, rabbit anti-human MAO A and sheep anti-bovine MAO B antibodies. A strong and specific alkaline phosphatase reaction was obtained with both anti-human MAO A antibodies. No trace of a signal was detected with anti-bovine MAO B antibody or preimmune sera. The positive band migrated more slowly than the human control suggesting that the putative nematode MAO is about 5 to 7kDa larger than the human enzyme. Evidence for the presence of MAO in whole animals was found by culturing the nematode on agar plates seeded with E. coli OP50 and containing the specific MAO A suicide inhibitor clorgyline or the structurally similar specific MAO B inhibitor deprenyl. For assays, starved Bristol N2 hermaphrodites from a plate were transferred to give 5 to 6 individuals per test plate. Plates were sealed with paraffin film and incubated at 20 C and monitored for two weeks with a microscope at 100 and 200x power. Clorgyline inhibited growth of the worm at 2.5x10 -5Mwhile deprenyl showed inhibition at >1x10 but <1x10 -3M.The effect with clorgyline expressed at 25 M is a concentration 2000 times lower than was required to observe behavioral effects in similar incubation studies with exogenously added neurotransmitters (Horvitz et al., '82, Science 216,1014). The high concentration of amines required in these experiments was attributed to impermeability of the worm's cuticle. This suggests that inhibition of growth results from an even lower concentration of clorgyline entering the animal. In vitro, MAO A is rapidly inhibited by 1x10 -7Mclorgyline or 1x10 -5Mdeprenyl. In addition to the observation that worms stopped growing in the presence of clorgyline and bacteria, cessation of pharyngeal pumping was evident. It is possible that inactivation of MAO increases the concentration of octopamine in a neuron that controls inhibition of pharyngeal pumping (Horvitz et al., '82, ibid.). Growth may have ceased due to starvation. Treatment of octopamine-defective and other mutants with clorgyline and other drugs should shed light on this proposal. These preliminary experiments strongly suggest the C. elegans contains MAO, possibly of the A type, and that the enzyme plays an essential role in either the development or the normal functioning of this simple organism. We now plan to firmly establish the presence of MAO and its type and determine the mechanism of growth arrest as this most likely underlies the role of MAO and its mode of action in C. elegans.

Boos J et al. (2021) Med Chem Res "Dual monoamine oxidase B and acetylcholine esterase inhibitors for treating movement and cognition deficits in a C. elegans model of Parkinson's disease."

Geldenhuys WJ, Shubbar A, Boos J

[Med Chem Res, 2021]

Parkinson's disease (PD) is an age-associated neurodegenerative movement disorder that leads to loss of dopaminergic neurons and motor deficits. Approaches to neuroprotection and symptom management in PD include use of monoamine oxidase B (MAO-B) inhibitors. Many patients with PD also exhibit memory loss in the later stages of disease progression, which is treated with acetylcholine esterase (AChE) inhibitors. We sought to identify a dual-mechanism compound that would inhibit both MAO-B and AChE enzymes. Our screen identified a promising compound (7) with balanced MAO-B (IC₅₀ of 16.83 M) and AChE inhibition activity (AChE IC₅₀ of 22.04 M). Application of this compound 7 increased short-term associative memory and significantly prevented 6-hydroxy-dopamine toxicity in dopaminergic neurons in the <i>Caenorhabditis elegans</i> nematode. These findings present a platform for future development of dual-mechanism drugs to treat neurodegenerative diseases such as PD.

Sakoguchi H et al. (2016) Biosci Biotechnol Biochem "Screening of biologically active monosaccharides: growth inhibitory effects of d-allose, d-talose, and l-idose against the nematode Caenorhabditis elegans."

Izumori K, Yoshihara A, Sakoguchi H, Sato M

[Biosci Biotechnol Biochem, 2016]

We compared the growth inhibitory effects of all aldohexose stereoisomers against the model animal Caenorhabditis elegans. Among the tested compounds, the rare sugars d-allose (d-All), d-talose (d-Tal), and l-idose (l-Ido) showed considerable growth inhibition under both monoxenic and axenic culture conditions. 6-Deoxy-d-All had no effect on growth, which suggests that C6-phosphorylation by hexokinase is essential for inhibition by d-All.

Sakoguchi H et al. (2016) Bioorg Med Chem Lett "Growth inhibitory effect of d-arabinose against the nematode Caenorhabditis elegans: Discovery of a novel bioactive monosaccharide."

Shintani T, Izumori K, Sato M, Sakoguchi H, Okuma K, Yoshihara A

[Bioorg Med Chem Lett, 2016]

Biological activities of unusual monosaccharides (rare sugars) have largely remained unstudied until recently. We compared the growth inhibitory effects of aldohexose stereoisomers against the animal model Caenorhabditis elegans cultured in monoxenic conditions with Escherichia coli as food. Among these stereoisomers, the rare sugar d-arabinose (d-Ara) showed particularly strong growth inhibition. The IC50 value for d-Ara was estimated to be 7.5mM, which surpassed that of the potent glycolytic inhibitor 2-deoxy-d-glucose (19.5mM) used as a positive control. The inhibitory effect of d-Ara was also observed in animals cultured in axenic conditions using a chemically defined medium; this excluded the possible influence of E. coli. To our knowledge, this is the first report of biological activity of d-Ara. The d-Ara-induced inhibition was recovered by adding either d-ribose or d-fructose, but not d-glucose. These findings suggest that the inhibition could be induced by multiple mechanisms, for example, disturbance of d-ribose and d-fructose metabolism.

Yoshihara A et al. (2019) Bioorg Med Chem Lett "Growth inhibition by 1-deoxy-d-allulose, a novel bioactive deoxy sugar, screened using Caenorhabditis elegans assay."

Sakoguchi H, Fleet GWJ, Izumori K, Shintani T, Sato M, Yoshihara A

[Bioorg Med Chem Lett, 2019]

The biological activities of deoxy sugars (deoxy monosaccharides) have remained largely unstudied until recently. We compared the growth inhibition by all 1-deoxyketohexoses using the animal model Caenorhabditis elegans. Among the eight stereoisomers, 1-deoxy-d-allulose (1d-d-Alu) showed particularly strong growth inhibition. The 50% inhibition of growth (GI₅₀) concentration by 1d-d-Alu was estimated to be 5.4mM, which is approximately 10 times lower than that of d-allulose (52.7mM), and even lower than that of the potent glycolytic inhibitor, 2-deoxy-d-glucose (19.5mM), implying that 1d-d-Alu has a strong growth inhibition. In contrast, 5-deoxy- and 6-deoxy-d-allulose showed no growth inhibition of C. elegans. The inhibition by 1d-d-Alu was alleviated by the addition of d-ribose or d-fructose. Our findings suggest that 1d-d-Alu-mediated growth inhibition could be induced by the imbalance in d-ribose metabolism. To our knowledge, this is the first report of biological activity of 1d-d-Alu which may be considered as an antimetabolite drug candidate.

Liew KF et al. (2018) Biomed Pharmacother "Multi-targeting aurones with monoamine oxidase and amyloid-beta inhibitory activities: Structure-activity relationship and translating multi-potency to neuroprotection."

Lee CY, Chan KL, Liew KF, Lee EH

[Biomed Pharmacother, 2018]

Previously, a series of aurones bearing amine and carbamate functionalities was synthesized and evaluated for their cholinesterase inhibitory activity and drug-like attributes. In the present study, these aurones were evaluated for their multi-targeting properties in two Alzheimer's disease (AD)-related activities namely, monoamine oxidase (MAO) and amyloid-beta (A) inhibition. Evaluation of the aurones for MAO inhibitory activity disclosed several potent selective inhibitors of MAO-B, particularly those with 6-methoxyl group attached at ring A. Of the different amine moieties attached as side chains, pyrrolidine-bearing aurones were prominent as represented by 2-2, the most potent inhibitor. Evaluation on the A aggregation inhibition identified 4-3 as the best inhibitor with a percentage inhibition comparable to that of a known A inhibitor curcumin. Examination on the neuroprotective ability of the more drug-like aurone 4-3 in two Caenorhabditis elegans neurodegeneration models showed 4-3 to protect the nematodes against both A- and 6-hydroxydopamine-induced toxicities. These new activities further support 4-3 as a promising lead to develop the aurones as potential multipotent agents for neurodegenerative diseases.

Katane M et al. (2020) Biochim Biophys Acta Proteins Proteom "Biochemical characterization of d-aspartate oxidase from Caenorhabditis elegans: Its potential use in the determination of free D-glutamate in biological samples."

Katane M, Sekine M, Nakayama K, Homma H, Kuwabara H, Saitoh Y, Miyamoto T

[Biochim Biophys Acta Proteins Proteom, 2020]

d-Aspartate oxidase (DDO) is a flavin adenine dinucleotide (FAD)-containing flavoprotein that stereospecifically acts on acidic D-amino acids (i.e., free d-aspartate and D-glutamate). Mammalian DDO, which exhibits higher activity toward d-aspartate than D-glutamate, is presumed to regulate levels of d-aspartate in the body and is not thought to degrade D-glutamate in vivo. By contrast, three DDO isoforms are present in the nematode Caenorhabditis elegans, DDO-1, DDO-2, and DDO-3, all of which exhibit substantial activity toward D-glutamate as well as d-aspartate. In this study, we optimized the Escherichia coli culture conditions for production of recombinant C. elegans DDO-1, purified the protein, and showed that it is a flavoprotein with a noncovalently but tightly attached FAD. Furthermore, C. elegans DDO-1, but not mammalian (rat) DDO, efficiently and selectively degraded D-glutamate in addition to d-aspartate, even in the presence of various other amino acids. Thus, C. elegans DDO-1 might be a useful tool for determining these acidic D-amino acids in biological samples.

Shintani T et al. (2019) J Appl Glycosci (1999) "D-Allose, a Stereoisomer of D-Glucose, Extends the Lifespan of Caenorhabditis elegans via Sirtuin and Insulin Signaling."

Izumori K, Sakoguchi H, Yoshihara A, Shintani T, Sato M

[J Appl Glycosci (1999), 2019]

D-Allose (D-All), C-3 epimer of D-glucose, is a rare sugar known to suppress reactive oxygen species generation and prevent hypertension. We previously reported that D-allulose, a structural isomer of D-All, prolongs the lifespan of the nematode Caenorhabditis elegans. Thus, D-All was predicted to affect longevity. In this study, we provide the first empirical evidence that D-All extends the lifespan of C. elegans. Lifespan assays revealed that a lifespan extension was induced by 28 mM D-All. In particular, a lifespan extension of 23.8 % was achieved (p< 0.0001). We further revealed that the effects of D-All on lifespan were dependent on the insulin gene daf-16 and the longevity gene sir-2.1, indicating a distinct mechanism from those of other hexoses, such as D-allulose, with previously reported antiaging effects.

Sato M et al. (2008) J Nat Med "Potential anthelmintic: D-psicose inhibits motility, growth and reproductive maturity of L1 larvae of Caenorhabditis elegans."

Izumori K, Yamasaki T, Kurose H, Sato M

[J Nat Med, 2008]

No anthelmintic sugars have yet been identified. Eight ketohexose stereoisomers (D- and L-forms of psicose, fructose, tagatose and sorbose), along with D-galactose and D-glucose, were examined for potency against L1 stage Caenorhabditis elegans fed Escherichia coli. Of the sugars, D-psicose specifically inhibited the motility, growth and reproductive maturity of the L1 stage. D-Psicose probably interferes with the nematode nutrition. The present results suggest that D-psicose, one of the rare sugars, is a potential anthelmintic.