Luedtke S et al. (2010) Invert Neurosci "The regulation of feeding and metabolism in response to food deprivation in Caenorhabditis elegans."

Luedtke S, O'Connor V, Holden-Dye L, Walker RJ

[Invert Neurosci, 2010]

This review considers the factors involved in the regulation of feeding and metabolism in response to food deprivation using Caenorhabditis elegans as a model organism. Some of the sensory neurons and interneurons involved in food intake are described, together with an overview of pharyngeal pumping. A number of chemical transmitters control feeding in C. elegans including 5-hydroxytryptamine (5-HT, serotonin), acetylcholine, glutamate, dopamine, octopamine, and tyramine. The roles of these transmitters are modified by neuropeptides, including FMRFamide-like peptides (FLPs), neuropeptide-like protein (NLPs), and insulin-like peptides. The precise effects of many of these neuropeptides have yet to be elucidated but increasingly they are being shown to play a role in feeding and metabolism in C. elegans. The regulation of fat stores is complex and appears to involve the expression of a large number of genes, many with mammalian homologues, suggesting that fat regulatory signalling is conserved across phyla. Finally, a brief comparison is made between C. elegans and mammals where for both, despite their evolutionary distance, classical transmitters and neuropeptides have anorectic or orexigenic properties. Thus, there is a rationale to support the argument that an understanding of the molecular and genetic basis of feeding and fat regulation in C. elegans may contribute to efforts aimed at the identification of targets for the treatment of conditions associated with abnormal metabolism and obesity.

Luedtke S et al. (2009) European Worm Neurobiology Meeting "Pumping off Food (PoffF): A neuromodulatable adaptive response to chronic food withdrawal."

Holden-Dye L, Walker R, Luedtke S, Murray C, Hopper N, OConnor V, Franks C, Dillon J, Mould R

[European Worm Neurobiology Meeting, 2009]

Presentation or withdrawal of food provides a powerful environmental cue that modulates many aspects of C.elegan.s behaviour. Food removal is known to have progressive effect on the locomotory behaviour depending on the time the organism is in the absence of food. Such adaptive behaviours are suggestive of a complex integrative response driven from external and potential internal cues. We have defined an adaptive response in pharyngeal pumping (feeding behviour) in response to chronic food withdrawl. Well fed worms (L4+1 day) placed on a no food arena for 5 hours show a complex change in their pattern of pharyngeal pumping. This is defined by three phases encompassing a i) progressive increase in pumping reaching ii) steady state prior to iii) an erratic phase in which the pharynx fluctuates between very high pump rate or no pumping. Overall, the pumping during PoffF rises to about 30 % of the rate seen in animals placed on food. This appears driven by distinct pathways to those that increase pharyngeal pumping on food. PoffF is not affected by the tph-1 mutants which otherwise show a severe inhibition in the increased pumping seen in worms on food. In a similar way many transmitters that are embedded in the pharyngeal microcircuit do not have a marked effect on this behaviour. In contrast cutting the cuticle to isolate the pharynx from the overriding extra-pharyngeal nervous system sees a loss in the PoffF behaviour. This suggests that the primary drive for PoffF derives from the extrapharyngeal circuit. Surprisingly, the PoffF is markedly different in mutants lacking glutamate (eat-4) and these animals show an instant elevation in pumping that is sustained at a higher level than in the wild-type animals off food. As the extrapharyngeal glutamate pathways is important in mediating responses to the withdrawal of chemosensory cues it suggests a model by which activation of such pathways inhibits pharyngeal pumping during food withdrawal. Interestingly, unc-31 which is thought to play a pivotal role in peptidergic signalling exhibits a PoffF that phenocopies the eat-4 mutants which might suggest an important interaction between glutamate and peptidergic signalling. Surprisingly, PoffF is completely absent in egl-3 mutants that are deficient in neuropeptides. However, the observed converse relationship between glutamate (eat-4) and egl-3 dependent neuropeptide signalling, with respect to PoffF, suggests an integrative interaction between fast and neuromodulatory transmitters. Overall these data reinforce how the pharyngeal circuit can be used to reveal important principles of neuroadaptive responses that follow changes in the environment.

S. Luedtke et al. (2006) European Worm Meeting "The Physiological Role of Peptidergic Transmission in the Pharyngeal Nervous System"

V. O'Connor, N.A. Hopper, R.J. Walker, S. Luedtke, L. Holden-Dye

[European Worm Meeting, 2006]

S. Luedtke, R.J. Walker, N.A. Hopper, V. O''Connor and L. Holden-Dye. We are interested in the peptidergic regulation of neuronal function. As the pharyngeal muscle potently responds to a number of flp neuropeptides, we are determining whether peptidergic signalling is involved in the physiological regulation of pumping activity. In a first approach we wish to identify genes that are involved in pharyngeal pumping activity and peptidergic signalling. To achieve this we have described the pumping activity on and off food in wild-type and mutant animals. Here we show data for several different mutants with a dysfunctional feeding phenotype and how this might help in understanding the interactions in the neuronal circuit underlying pharyngeal pumping.. In another approach, we are developing an optical assay for peptidergic signalling. The neuropeptide we are focusing on initially is FLP-13, as this is expressed in pharyngeal neurones and has been shown to have a potent inhibitory effect on pharyngeal pumping. We have generated a flp-13::dsRed2 fusion construct in which the optical marker is inserted within the coding sequence of one of the FLP-13 peptides. This construct has been injected into animals using the pha-1 protocol as a selection for transgenic animals. Stable lines that were rescued for pha-1 were recovered, PCR confirmed they had the flp-13::dsRed transgene and RT-PCR confirmed that this construct was expressed. However, none of the animals exhibited fluorescence. Currently we are experimenting with other fluorophores that may be more suitable for use with the dense core secretory pathway. Funded by the Gerald Kerkut Charitable Trust. We are grateful to the C. elegans Genetics Center for the provision of strains.

Vinci CR et al. (2007) J Biol Chem "Recognition of age-damaged (R,S)-adenosyl-L-methionine by two methyltransferases in the yeast Saccharomyces cerevisiae."

Vinci CR, Clarke SG

[J Biol Chem, 2007]

The biological methyl donor, S adenosylmethionine (AdoMet), can exist in two diastereoisomeric states with respect to its sulfonium ion. The "S" configuration, (S,S)AdoMet, is the only form that is produced enzymatically as well as the only form used in almost all biological methylation reactions. Under physiological conditions, however, the sulfonium ion can spontaneously racemize to the "R" form, producing (R,S)AdoMet. As of yet, (R,S)AdoMet has no known physiological function and may inhibit cellular reactions. In this study, two enzymes have been found in Saccharomyces cerevisiae that are capable of recognizing (R,S)AdoMet and using it to methylate homocysteine to form methionine. These enzymes are the products of the SAM4 and MHT1 genes, previously identified as homocysteine methyltransferases dependent upon AdoMet and S-methylmethionine respectively. We find here that Sam4 recognizes both (S,S) and (R,S)AdoMet, but its activity is much higher with the R,S form. Mht1 reacts with only the R,S form of AdoMet while no activity is seen with the S,S form. R,S-specific homocysteine methyltransferase activity is also shown here to occur in extracts of Arabidopsis thaliana, Drosophila melanogaster, and Caenorhabditis elegans, but has not been detected in several tissue extracts of Mus musculus. Such activity may function to prevent the accumulation of (R,S)AdoMet in these organisms.

Fanning S et al. (2018) Mol Cell "Lipidomic Analysis of -Synuclein Neurotoxicity Identifies Stearoyl CoA Desaturase as a Target for Parkinson Treatment."

Lou Y, Haque A, Freyzon Y, Farese RV, Terry-Kantor E, Hofbauer HF, Termine D, Welte MA, Barrasa MI, Imberdis T, Noble T, Lindquist S, Clish CB, Jaenisch R, Pincus D, Nuber S, Sandoe J, Kohlwein SD, Kim TE, Ho GPH, Ramalingam N, Walther TC, Baru V, Selkoe D, Srinivasan S, Landgraf D, Soldner F, Dettmer U, Fanning S, Becuwe M, Newby G

[Mol Cell, 2018]

In Parkinson's disease (PD), -synuclein (S) pathologically impacts the brain, a highly lipid-rich organ. We investigated how alterations in S or lipid/fattyacid homeostasis affect each other. Lipidomic profiling of human S-expressing yeast revealed increases in oleic acid (OA, 18:1), diglycerides, and triglycerides. These findings were recapitulated in rodent and human neuronal models of S dyshomeostasis (overexpression; patient-derived triplication or E46K mutation; E46K mice). Preventing lipid droplet formation or augmenting OA increased S yeast toxicity; suppressing the OA-generating enzyme stearoyl-CoA-desaturase (SCD) was protective. Genetic or pharmacological SCD inhibition ameliorated toxicity in S-overexpressing rat neurons. In a C.elegans model, SCD knockout prevented S-induced dopaminergic degeneration. Conversely, we observed detrimental effects of OA on S homeostasis: in human neural cells, excess OA caused S inclusion formation, which was reversed by SCD inhibition. Thus, monounsaturated fatty acid metabolism is pivotal for S-induced neurotoxicity, and inhibiting SCD represents a novel PD therapeutic approach.

Vandecandelaere I et al. (2017) PLoS One "Metabolic activity, urease production, antibiotic resistance and virulence in dual species biofilms of Staphylococcus epidermidis and Staphylococcus aureus."

Deforce D, Coenye T, Van Nieuwerburgh F, Vandecandelaere I

[PLoS One, 2017]

In this paper, the metabolic activity in single and dual species biofilms of Staphylococcus epidermidis and Staphylococcus aureus isolates was investigated. Our results demonstrated that there was less metabolic activity in dual species biofilms compared to S. aureus biofilms. However, this was not observed if S. aureus and S. epidermidis were obtained from the same sample. The largest effect on metabolic activity was observed in biofilms of S. aureus Mu50 and S. epidermidis ET-024. A transcriptomic analysis of these dual species biofilms showed that urease genes and genes encoding proteins involved in metabolism were downregulated in comparison to monospecies biofilms. These results were subsequently confirmed by phenotypic assays. As metabolic activity is related to acid production, the pH in dual species biofilms was slightly higher compared to S. aureus Mu50 biofilms. Our results showed that S. epidermidis ET-024 in dual species biofilms inhibits metabolic activity of S. aureus Mu50, leading to less acid production. As a consequence, less urease activity is required to compensate for low pH. Importantly, this effect was biofilm-specific. Also S. aureus Mu50 genes encoding virulence-associated proteins (Spa, SplF and Dps) were upregulated in dual species biofilms compared to monospecies biofilms and using Caenorhabditis elegans infection assays, we demonstrated that more nematodes survived when co-infected with S. epidermidis ET-024 and S. aureus mutants lacking functional spa, splF or dps genes, compared to nematodes infected with S. epidermidis ET-024 and wild- type S. aureus. Finally, S. epidermidis ET-024 genes encoding resistance to oxacillin, erythromycin and tobramycin were upregulated in dual species biofilms and increased resistance was subsequently confirmed. Our data indicate that both species in dual species biofilms of S. epidermidis and S. aureus influence each other's behavior, but additional studies are required necessary to elucidate the exact mechanism(s) involved.

Franks CJ et al. (2006) Invert Neurosci "Anatomy, physiology and pharmacology of Caenorhabditis elegans pharynx: a model to define gene function in a simple neural system."

Franks CJ, Luedtke S, Holden-Dye L, Bull K, Walker RJ

[Invert Neurosci, 2006]

Invertebrate neuroscience has provided a number of very informative model systems that have been extensively utilized in order to define the neurobiological bases of animal behaviours (Sattelle and Buckingham in Invert Neurosci 6:1-3, 2006). Most eminent among these are a number of molluscs, including Aplysia californica, Lymnaea stagnalis and Helix aspersa, crustacean systems such as the crab stomatogastric ganglion and a wide-range of other arthropods. All of these have been elegantly exploited to shed light on the very important phenomenon of the molecular and cellular basis for synaptic regulation that underpins behavioural plasticity. Key to the successful use of these systems has been the ability to study well-defined, relatively simple neuronal circuits that direct and regulate a quantifiable animal behaviour. Here we describe the pharyngeal system of the nematode C. elegans and its utility as a model for defining the genetic basis of behaviour. The circuitry of the nervous system in this animal is uniquely well-defined. Furthermore, the feeding behaviour of the worm is controlled by the activity of the pharynx and this in turn is regulated in a context-dependent manner by a simple nervous system that integrates external signals, e.g. presence or absence of food, and internal signals, e.g. the nutritional status of the animal to direct an appropriate response. The genetics of C. elegans is being effectively exploited to provide novel insight into genes that function to regulate the neuronal network that controls the pharynx. Here we summarise the progress to date and highlight topics for future research. Two main themes emerge. First, although the anatomy of the pharyngeal system is very well-defined, there is a much poorer understanding of its neurochemistry. Second, it is evident that the neurochemistry is remarkably complex for such a simple circuit/behaviour. This suggests that the pharyngeal activity may be subject to exquisitely precise regulation depending on the animal''s environment and status. This therefore provides a very tractable genetic model to investigate neural mechanisms for signal integration and synaptic plasticity in a well-defined neuronal network that directs a quantifiable behaviour, feeding.

Vandecandelaere I et al. (2014) Pathog Dis "Protease production by Staphylococcus epidermidis and its effect on Staphylococcus aureus biofilms."

Coenye T, Vandecandelaere I, Depuydt P, Nelis HJ

[Pathog Dis, 2014]

Due to the resistance of Staphylococcus aureus to several antibiotics, treatment of S. aureus infections is often difficult. As an alternative to conventional antibiotics, the field of bacterial interference is investigated. Staphylococcus epidermidis produces a serine protease (Esp) which inhibits S. aureus biofilm formation and which degrades S. aureus biofilms. In this study, we investigated the protease production of 114 S. epidermidis isolates, obtained from biofilms on endotracheal tubes (ET). Most of the S. epidermidis isolates secreted a mixture of serine, cysteine and metalloproteases. We found a link between high protease production by S. epidermidis and the absence of S. aureus in ET biofilms obtained from the same patient. Treating S. aureus biofilms with the supernatant (SN) of the most active protease producing S. epidermidis isolates resulted in a significant biomass decrease compared to untreated controls, while the number of metabolically active cells was not affected. The effect on the biofilm biomass was mainly due to serine proteases. Staphylococcus aureus biofilms treated with the SN of protease producing S. epidermidis were thinner with almost no extracellular matrix. An increased survival of Caenorhabditis elegans, infected with S. aureus Mu50, was observed when the SN of protease positive S. epidermidis was added.

Kamp F et al. (2010) EMBO J "Inhibition of mitochondrial fusion by -synuclein is rescued by PINK1, Parkin and DJ-1."

Haass C, Hegermann J, Giese A, Eimer S, Kamp F, Lutz AK, Nuscher B, Wender N, Brunner B, Winklhofer KF, Exner N, Beyer K, Bartels T

[EMBO J, 2010]

Aggregation of -synuclein (S) is involved in the pathogenesis of Parkinson's disease (PD) and a variety of related neurodegenerative disorders. The physiological function of S is largely unknown. We demonstrate with in vitro vesicle fusion experiments that S has an inhibitory function on membrane fusion. Upon increased expression in cultured cells and in Caenorhabditis elegans, S binds to mitochondria and leads to mitochondrial fragmentation. In C. elegans age-dependent fragmentation of mitochondria is enhanced and shifted to an earlier time point upon expression of exogenous S. In contrast, siRNA-mediated downregulation of S results in elongated mitochondria in cell culture. S can act independently of mitochondrial fusion and fission proteins in shifting the dynamic morphologic equilibrium of mitochondria towards reduced fusion. Upon cellular fusion, S prevents fusion of differently labelled mitochondrial populations. Thus, S inhibits fusion due to its unique membrane interaction. Finally, mitochondrial fragmentation induced by expression of S is rescued by coexpression of PINK1, parkin or DJ-1 but not the PD-associated mutations PINK1 G309D and parkin 1-79 or by DJ-1 C106A.

El Mouridi, Sonia et al. (2021) MicroPubl Biol

AlHarbi, Sarah, El Mouridi, Sonia, Frkjr-Jensen, Christian

[MicroPubl Biol, 2021]

For El Mouridi, S; AlHarbi, S; Frkjr-Jensen, C (2021). A histamine-gated channel is an efficient negative selection marker for C. elegans transgenesis. microPublication Biology. 10.17912/micropub.biology.000349.