A functional nuclear localization sequence in the C. elegans TRPV channel OCR-2

Anandamide Modulates Thermal Avoidance in Caenorhabditis elegans Through Vanilloid and Cannabinoid Receptor Interplay

Understanding the endocannabinoid system in C. elegans may offer insights into basic biological processes and potential therapeutic targets for managing pain and inflammation in human. It is well established that anandamide modulates pain perception by binding to cannabinoid and vanilloid receptors, regulating neurotransmitter release and neuronal activity. One objective of this study was to demonstrate the suitability of C. elegans as a model organism for assessing the antinociceptive properties of bioactive compounds and learning about the role of endocannabinoid system in C. elegans. The evaluation of the compound anandamide (AEA) revealed antinociceptive activity by impeding C. elegans nocifensive response to noxious heat. Proteomic and bioinformatic investigations uncovered several pathways activated by AEA. Enrichment analysis unveiled significant involvement of ion homeostasis pathways, which are crucial for maintaining neuronal function and synaptic transmission, suggesting AEA's impact on neurotransmitter release and synaptic plasticity. Additionally, pathways related to translation, protein synthesis, and mTORC1 signaling were enriched, highlighting potential mechanisms underlying AEA's antinociceptive effects. Thermal proteome profiling identified NPR-32 and NPR-19 as primary targets of AEA, along with OCR-2, Cathepsin B, Progranulin, Transthyretin, and ribosomal proteins. These findings suggest a complex interplay between AEA and various cellular processes implicated in nociceptive pathways and inflammation modulation. Further investigation into these interactions could provide valuable insights into the therapeutic potential of AEA and its targets for the management of pain-related conditions.

Cannabidiol and Tetrahydrocannabinol Antinociceptive Activity is Mediated by Distinct Receptors in Caenorhabditis elegans

Cannabis has gained popularity in recent years as a substitute treatment for pain following the risks of typical treatments uncovered by the opioid crisis. The active ingredients frequently associated with pain-relieving effects are the phytocannabinoids Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), but their effectiveness and mechanisms of action are still under research. In this study, we used Caenorhabditis elegans, an ideal model organism for the study of nociception that expresses mammal ortholog cannabinoid (NPR-19 and NPR-32) and vanilloid (OSM-9 and OCR-2) receptors. Here, we evaluated the antinociceptive activity of THC and CBD, identifying receptor targets and several metabolic pathways activated following exposure to these molecules. The thermal avoidance index was used to phenotype each tested C. elegans experimental group. The data revealed for the first time that THC and CBD decreases the nocifensive response of C. elegans to noxious heat (32-35 °C). The effect was reversed 6 h post- CBD exposure but not for THC. Further investigations using specific mutants revealed CBD and THC are targeting different systems, namely the vanilloid and cannabinoid systems, respectively. Proteomic analysis revealed differences following Reactome pathways and gene ontology biological process database enrichment analyses between CBD or THC-treated nematodes and provided insights into potential targets for future drug development.

Cannflavins isolated from Cannabis sativa impede Caenorhabditis elegans response to noxious heat

Cannflavins, flavonoids abundantly present in Cannabis sativa, possess a distinct chemical structure comprising a vanillyl group. Notably, the capsaicin structure also contains a vanillyl group, which is considered essential for interacting with the vanilloid receptor. The vanilloid receptor plays a crucial role in the perception of pain, heat, and inflammation and mediates the analgesic effects of capsaicin. Therefore, we postulated that prolonged exposure to cannflavin A (Can A) and cannflavin B (Can B) would provoke vanilloid receptor desensitization and hinder nocifensive responses to noxious thermal stimuli. C. elegans wild-type (N2) and mutants were exposed to Can A and Can B solutions for 60 min and then aliquoted on Petri dishes divided into quadrants for thermal stimulation. We then determined the thermal avoidance index for each C. elegans experimental group. Proteomics was performed to identify proteins and pathways associated with Can A or B treatment. Prolonged exposure to Can A and Can B hindered heat avoidance (32-35 °C) in C. elegans. No antinociceptive effect was observed 6 h post Can A or B exposure. Proteomics and Reactome pathway enrichment analyses identified hierarchical differences between Can A- and B-treated nematodes. However, both treatments were related to eukaryotic translation initiation (R-CEL-72613) and metabolic processes strongly associated with pain development. Our study aids in characterizing the pharmacological activity of cannflavins isolated from Cannabis sativa and outlines a possible application as pain therapy.

Chemosensory signal transduction in Caenorhabditis elegans

Chemosensory neurons translate perception of external chemical cues, including odorants, tastants, and pheromones, into information that drives attraction or avoidance motor programs. In the laboratory, robust behavioral assays, coupled with powerful genetic, molecular and optical tools, have made Caenorhabditis elegans an ideal experimental system in which to dissect the contributions of individual genes and neurons to ethologically relevant chemosensory behaviors. Here, we review current knowledge of the neurons, signal transduction molecules and regulatory mechanisms that underlie the response of C. elegans to chemicals, including pheromones. The majority of identified molecules and pathways share remarkable homology with sensory mechanisms in other organisms. With the development of new tools and technologies, we anticipate that continued study of chemosensory signal transduction and processing in C. elegans will yield additional new insights into the mechanisms by which this animal is able to detect and discriminate among thousands of chemical cues with a limited sensory neuron repertoire.

Multiple olfactory pathways contribute to the lure process of Caenorhabditis elegans by pathogenic bacteria

Chemosensation is indispensable for the survival of Caenorhabditis elegans to discriminate food and pathogenic bacteria in their living environment. Food-like odors emitted by the pathogen Bacillus nematocida B16 for trapping its hosts and an olfactory signaling pathway responsible to sense the attractant 2-heptanone were identified in our previous study. Here, we further explore how the worms recognize the attractive molecules indole and 2-ethyl hexanol, which have different chemical properties and modest nematode-luring ability. We show that the chemotaxis toward indole and 2-ethyl hexanol requires the G protein-coupled receptors encoded by str-193 on AWC and str-7 on AWA. In a further genetic screen for downstream effectors in olfactory signaling cascades, the Gα subunit GSA-1, guanylyl cyclase ODR-1 and DAF-11 and the cGMP-gated channel TAX-2/TAX-4 were found to be necessary for indole sensation, whereas the TRPV channels OSM-9/OCR-2 and the PLC pathway activated by GPA-6 are responsible for the detection of 2-ethyl hexanol. Altogether, our current work further clarifies the distinct olfactory signaling pathways through which C. elegans senses different chemicals and is lured by B. nematocida B16, improving our comprehensive understanding of the mechanisms by which bacterial pathogens effectively infect their hosts.

Transient Receptor Potential Mucolipin-1 Channels in Glioblastoma: Role in Patient's Survival

A link between mucolipin channels and tumors has been recently suggested. Herein, we aim to investigate the transient receptor potential mucolipin (TRPML)-1 relevance in glioblastoma. The expression of this channel was evaluated via qRT-PCR and immunohistochemistry in biopsies from 66 glioblastoma patients and two human glioblastoma cell lines and compared to normal human brain, astrocytes, and epileptic tissues. The subcellular distribution of TRPML-1 was examined via confocal microscopy in the glioma cell lines. Then, to assess the role of TRPML-1, cell viability assays have been conducted in T98 and U251 cell lines treated with the specific TRPML-1 agonist, MK6-83. We found that MK6-83 reduced cell viability and induced caspase-3-dependent apoptosis. Indeed, the TRPML-1 silencing or the blockage of TRPML-1 dependent [Ca²⁺]_i release abrogated these effects. In addition, exposure of glioma cells to the reactive oxygen species (ROS) inducer, carbonyl cyanide m-chlorophenylhydrazone (CCCP), stimulated a TRPML-1-dependent autophagic cell death, as demonstrated by the ability of the autophagic inhibitor bafilomycin A, the TRPML-1 inhibitor sphingomyelin, and the TRPML-1 silencing to completely inhibit the CCCP-mediated effects. To test a possible correlation with patient’s survival, Kaplan–Meier, univariate, and multivariate analysis have been performed. Data showed that the loss/reduction of TRPML-1 mRNA expression strongly correlates with short survival in glioblastoma (GBM) patients, suggesting that the reduction of TRPML-1 expression represents a negative prognostic factor in GBM patients.

A Real-Time Biosensor for ERK Activity Reveals Signaling Dynamics during C. elegans Cell Fate Specification

Kinase translocation reporters (KTRs) are genetically encoded fluorescent activity sensors that convert kinase activity into a nucleocytoplasmic shuttling equilibrium for visualizing single-cell signaling dynamics. Here, we adapt the first-generation KTR for extracellular signal-regulated kinase (ERK) to allow easy implementation in vivo. This sensor, "ERK-nKTR," allows quantitative and qualitative assessment of ERK activity by analysis of individual nuclei and faithfully reports ERK activity during development and neural function in diverse cell contexts in Caenorhabditis elegans. Analysis of ERK activity over time in the vulval precursor cells, a well-characterized paradigm of epidermal growth factor receptor (EGFR)-Ras-ERK signaling, has identified dynamic features not evident from analysis of developmental endpoints alone, including pulsatile frequency-modulated signaling associated with proximity to the EGF source. The toolkit described here will facilitate studies of ERK signaling in other C. elegans contexts, and the design features will enable implementation of this technology in other multicellular organisms.

Eag1 K+ Channel: Endogenous Regulation and Functions in Nervous System

Ether-à-go-go1 (Eag1, Kv10.1, KCNH1) K⁺ channel is a member of the voltage-gated K⁺ channel family mainly distributed in the central nervous system and cancer cells. Like other types of voltage-gated K⁺ channels, the EAG1 channels are regulated by a variety of endogenous signals including reactive oxygen species, rendering the EAG1 to be in the redox-regulated ion channel family. The role of EAG1 channels in tumor development and its therapeutic significance have been well established. Meanwhile, the importance of hEAG1 channels in the nervous system is now increasingly appreciated. The present review will focus on the recent progress on the channel regulation by endogenous signals and the potential functions of EAG1 channels in normal neuronal signaling as well as neurological diseases.

Cell Biology of the Caenorhabditis elegans Nucleus

Studies on the Caenorhabditis elegans nucleus have provided fascinating insight to the organization and activities of eukaryotic cells. Being the organelle that holds the genetic blueprint of the cell, the nucleus is critical for basically every aspect of cell biology. The stereotypical development of C. elegans from a one cell-stage embryo to a fertile hermaphrodite with 959 somatic nuclei has allowed the identification of mutants with specific alterations in gene expression programs, nuclear morphology, or nuclear positioning. Moreover, the early C. elegans embryo is an excellent model to dissect the mitotic processes of nuclear disassembly and reformation with high spatiotemporal resolution. We review here several features of the C. elegans nucleus, including its composition, structure, and dynamics. We also discuss the spatial organization of chromatin and regulation of gene expression and how this depends on tight control of nucleocytoplasmic transport. Finally, the extensive connections of the nucleus with the cytoskeleton and their implications during development are described. Most processes of the C. elegans nucleus are evolutionarily conserved, highlighting the relevance of this powerful and versatile model organism to human biology.

Differential Effects of TRPA and TRPV Channels on Behaviors of Caenorhabditis elegans

TRPA and TRPV ion channels are members of the transient receptor potential (TRP) cation channel superfamily, which mediates various sensory transductions. In Caenorhabditis elegans, the TRPV channels are known to affect chemosensation, while the TRPA-1 channel is associated with thermosensation and mechanosensation. We examined thermosensation, chemosensation, and osmosensation in strains lacking TRPA-1 or TRPV channels. We found that TRPV channel knockout worms exhibited similar behavioral deficits associated with thermotaxis as the TRPA-1 channel knockout, suggesting a dual role for TRPV channels. In contrast, chemosensation responses, assessed by both avoidance reversal behavior and NaCl osmosensation, were dependent on TRPV channels but seemed independent of TRPA-1 channel. Our findings suggest that, in addition to TRPA-1 channel, TRPV channels are necessary for thermotaxis and may activate, or modulate, the function of TRPA-1 channels. In contrast, TRPA-1 channels do not have a dual responsibility, as they have no functional role in odorant avoidance or osmosensation.

Plasticity of chemoreceptor gene expression: Sensory and circuit inputs modulate state-dependent chemoreceptors

Animals dramatically modify their chemosensory behaviors when starved, which could allow them to alter and optimize their food-search strategies. Dynamic changes in the gene expression of chemoreceptors may be a general mechanism underlying food and state-dependent changes in chemosensory behaviors. In our recent study,(1) we identified chemoreceptors in the ADL sensory neuron type of C. elegans that are modulated by feeding state and food availability. Here, we highllight our recent findings by which sensory inputs into ADL, neuronal outputs from ADL, and circuit inputs from the RMG interneuron, which is electrically connected to ADL, are required to regulate an ADL-expressed chemoreceptor. This sensory and circuit-mediated regulation of chemoreceptor gene expression is dependent on cell-autonomous pathways acting in ADL, e.g. KIN-29, DAF-2, OCR-2 and calcium signaling, and circuit inputs from RMG mediated by NPR-1. Based on these findings, we propose an intriguing but speculative feedback modulatory circuit mechanism by which sensory perception of food and internal state signals may be coupled to regulate ADL-expressed chemoreceptors, which may allow animals to precisely regulate and fine-tune their chemosensory neuron responses as a function of feeding state.

The long N-terminus of the C. elegans DNA repair enzyme APN-1 targets the protein to the nucleus of a heterologous system

We previously isolated from a Caenorhabditis elegans cDNA library, designed for two-hybrid screening, a gene encoding the DNA repair enzyme APN-1 using cross-specie complementation analysis of the Saccharomyces cerevisiae apn1∆ apn2∆ tpp1∆ triple mutant deficient in the ability to repair several types of DNA lesions including apurinic/apyrimidinic (AP) sites. We subsequently purified the APN-1 from this yeast mutant and demonstrated that it possesses four distinct DNA repair activities. However, following the re-annotation of the C. elegans genome we discovered that the functionally active APN-1 encoded by the cDNA from the library might lack 108 amino acid residues from the N-terminus. We therefore synthesized the entire C. elegans apn-1 gene encoding the putative full-length APN-1 and created several N-terminal deletion mutants lacking either 63, 83 or 118 amino acid residues. The full-length APN-1, APN-1 (1-63Δ) and APN-1 (1-83Δ), but not APN-1 (1-118Δ) were stably expressed in the yeast triple mutant and cleaved the AP site substrate. However, only the full-length APN-1 rescued the yeast mutant from the genotoxicity caused by methyl methane sulfonate, a DNA damaging agent that creates AP sites in the genome. The full-length APN-1 was localized to the yeast nucleus, while APN-1 (1-63Δ) and APN-1 (1-83Δ) retained a cytoplasmic distribution. Our data suggest that the N-terminal region has no direct role in the DNA repair functions of APN-1 other than to target the protein to the nucleus and possibly to maintain its stability. Thus, the truncated APN-1, previously isolated from the two-hybrid library, ability to complement the yeast triple mutant depends on the engineered SV40 nuclear localization signal.