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Cilia are microtubule-based cellular projections that act as motile, sensory, and secretory organelles. These structures receive information from the environment and transmit downstream signals to the cell body. Cilia also release vesicular ectosomes that bud from the ciliary membrane and carry an array of bioactive enzymes and peptide products. Peptidergic signals represent an ancient mode of intercellular communication, and in metazoans are involved in the maintenance of cellular homeostasis and various other physiological processes and responses. Numerous peptide receptors, subtilisin-like proteases, the peptide-amidating enzyme, and bioactive amidated peptide products have been localized to these organelles. In this review, we detail how cilia serve as specialized signaling organelles and act as a platform for the regulated processing and secretion of peptidergic signals. We especially focus on the processing and trafficking pathways by which a peptide precursor from the green alga Chlamydomonas reinhardtii is converted into an amidated bioactive product—a chemotactic modulator—and released from cilia in ectosomes. Biochemical dissection of this complex ciliary secretory pathway provides a paradigm for understanding cilia-based peptidergic signaling in mammals and other eukaryotes. [ABSTRACT FROM AUTHOR]

Many anthelmintics target the neuromuscular system, in particular by interfering with signaling mediated by classical neurotransmitters. Although peptidergic signaling has been proposed as a novel target for anthelmintics, current knowledge of the neuropeptide complement of many helminth groups is still limited, especially for parasitic flatworms (cestodes, trematodes, and monogeneans). In this work, we have characterized the neuropeptide complement of the model cestode Hymenolepis microstoma. Peptidomic characterization of adults of H. microstoma validated many of the neuropeptide precursor (npp) genes previously predicted in silico, and identified novel neuropeptides that are conserved in parasitic flatworms. Most neuropeptides from parasitic flatworms lack significant similarity to those from other animals, confirming the uniqueness of their peptidergic signaling. Analysis of gene expression of ten npp genes by in situ hybridization confirmed that all of them are expressed in the nervous system and identified cryptic features, including the first evidence of dorsoventral asymmetry, as well as a new population of peripheral peptidergic cells that appears to be conserved in the trematode Schistosoma mansoni. Finally, we characterized in greater detail Attachin, an SIFamide homolog. Although its expression is largely restricted to the longitudinal nerve cords and cerebral commissure in H. microstoma, it shows widespread localization in the larval nervous system of Echinococcus multilocularis and Mesocestoides corti. Exogenous addition of a peptide corresponding to the highly conserved C‐terminus of Attachin stimulated motility and attachment of M. corti larvae. Altogether, this work provides a robust experimental foothold for the characterization of peptidergic signaling in parasitic flatworms. Cover Image for this issue: https://doi.org/10.1111/jnc.15418 [ABSTRACT FROM AUTHOR]

Extracellular vesicles (EVs) provide a mechanism for intercellular communication that transports complex signals in membrane delimited structures between cells, tissues and organisms. Cells secrete EVs of various subtypes defined by the pathway leading to release and by the pathological condition of the cell. Cilia are evolutionarily conserved organelles that can act as sensory structures surveilling the extracellular environment. Here we discuss the secretory functions of cilia and their biological implications. Studies in multiple species – from the nematode Caenorhabditis elegans and the chlorophyte alga Chlamydomonas reinhardtii to mammals – have revealed that cilia shed bioactive EVs (ciliary EVs or ectosomes) by outward budding of the ciliary membrane. The content of ciliary EVs is distinct from that of other vesicles released by cells. Peptides regulate numerous aspects of metazoan physiology and development through evolutionarily conserved mechanisms. Intriguingly, cilia-derived vesicles have recently been found to mediate peptidergic signaling. C. reinhardtii releases the peptide α-amidating enzyme (PAM), bioactive amidated products and components of the peptidergic signaling machinery in ciliary EVs in a developmentally regulated manner. Considering the origin of cilia in early eukaryotes, it is likely that release of peptidergic signals in ciliary EVs represents an alternative and ancient mode of regulated secretion that cells can utilize in the absence of dedicated secretory granules. [ABSTRACT FROM AUTHOR]

Abstract The southern rock lobster, Jasus edwardsii , is a member of the Achelata native to New Zealand and southern Australia that in addition to being the subject of an extensive wild fishery, has been proposed as a target for aquaculture. One obstacle to the farming of this species is its long maturation period, and the development of large-scale commercial aquaculture will require management strategies that reduce the duration of its time in culture. Increasing food intake can result in increased growth rates, and may be one way to reduce the time to market for farmed lobsters. In crustaceans, food intake and growth are regulated by locally released and/or circulating paracrines/hormones, the largest class being peptides. In the study presented here, the native peptides of J. edwardsii , as well as their cognate receptors, were predicted using a publicly accessible transcriptome. Two hundred and seventy distinct peptides were identified (the largest peptidome currently extant for any decapod), 122 of which possess structures that place them into generally recognized arthropod peptide families, i.e. , adipokinetic hormone-corazonin-like peptide, allatostatin A, allatostatin B, allatostatin C, bursicon, CCHamide, corazonin, crustacean cardioactive peptide, crustacean hyperglycemic hormone/molt-inhibiting hormone, diuretic hormone 31, diuretic hormone 44, eclosion hormone, elevenin, FMRFamide-like peptide, glycoprotein hormone, GSEFLamide, inotocin, insulin-like peptide, leucokinin, myosuppressin, neuroparsin, neuropeptide F, orcokinin, orcomyotropin, pigment dispersing hormone, proctolin, pyrokinin, red pigment concentrating hormone, RYamide, short neuropeptide F, SIFamide, sulfakinin, tachykinin-related peptide and trissin. Putative receptors for many of the identified peptide groups were also identified via transcriptome mining. This is the first report of a peptidome and peptide receptors for J. edwardsii , and as such, provides a powerful new resource for beginning to investigate the physiological/behavioral roles played by peptidergic signaling systems in this species, including the roles they play in controlling processes that are of importance for improving aquaculture management strategies. Highlights • Jasus edwardsii peptidergic systems were identified via in silico transcriptome mining/bioinformatics. • The structures of 270 peptides encompassing 33 different families were predicted, as were receptors for 17 peptide groups. • The peptides/receptors provide a resource for investigating the physiological roles peptidergic systems play in Jasus. • The peptides/receptors provide targets for developing new aquaculture management strategies for rock/spiny lobster species. [ABSTRACT FROM AUTHOR]

Due to its sensitivity to many environmental and anthropogenic stressors, including a wide range of chemical compounds, Hyalella azteca , a freshwater amphipod, has emerged as one of the most commonly used invertebrates for ecotoxicological assessment.Peptidergic signaling systems are key components in the control of organism-environment interactions, and there is a growing literature suggesting that they are targets of a number of aquatic toxicants.Interestingly, and despite its model species status in the field of ecotoxicology, little is known about the peptide hormones of H. azteca .Here, a transcriptome was produced for this species using the de novo assembler Trinity and mined for sequences encoding putative peptide precursors; the transcriptome was assembled from 460,291,636 raw reads and consists of 133,486 unique transcripts.Seventy-six sequences encoding peptide pre/preprohormones were identified from this transcriptome, allowing for the prediction of 202 distinct peptides, which included members of the allatostatin A, allatostatin B, allatostatin C, allatotropin, bursicon, CCHamide, corazonin, crustacean cardioactive peptide, crustacean hyperglycemic hormone/molt-inhibiting hormone, ecdysis-triggering hormone, eclosion hormone, elevenin, FMRFamide-like peptide, glycoprotein hormone, GSEFLamide, inotocin, leucokinin, myosuppressin, neuropeptide F, orcokinin, orcomyotropin, pigment dispersing hormone, proctolin, pyrokinin, red pigment concentrating hormone, RYamide, short neuropeptide F, SIFamide, sulfakinin, tachykinin-related peptide and trissin families.These peptides expand the known peptidome for H. azteca approximately nine-fold, forming a strong foundation for future studies of peptidergic control, including disruption by aquatic toxicants, in this important ecotoxicological model. [ABSTRACT FROM AUTHOR]

Peptides may act through G protein-coupled receptors to influence cardiovascular performance; thus, delineating mechanisms involved in signaling is a molecular-based strategy to influence health. Molecular switches, often represented by conserved motifs, maintain a receptor in an inactive state. However, once the switch is broken, the transmembrane regions move and activation occurs. The molecular switches of Drosophila melanogaster myosuppressin (MS) receptors were previously identified to include a unique ionic lock and novel 3-6 lock, as well as transmission and tyrosine toggle switches. In addition to MS, cardioactive ligands structurally related by a C-terminal RF-NH 2 include sulfakinin, neuropeptide F (NPF), short NPF, and FMRF-NH 2 -containing peptide subfamilies. We hypothesized receptor molecular switch motifs were conserved within a RF-NH 2 subfamily and across species. Thus, we investigated RF-NH 2 receptor (RFa-R) molecular switches in D. melanogaster , Tribolium castaneum , Anopheles gambiae , Rhodnius prolixus , and Bombyx mori . Adipokinetic hormone (AKH), which does not contain a RF-NH 2 , was also examined. The tyrosine toggle switch and ionic lock showed a higher degree of conservation within a RF-NH 2 subfamily than the transmission switch and 3-7 lock. AKH receptor motifs were not representative of a RF-NH 2 subfamily. The motifs and interactions of switches in the RFa-Rs were consistent with receptor activation and ligand-specific binding. [ABSTRACT FROM AUTHOR]

Ciliary ectosomes are vesicles that bud from the ciliary membrane. Isolation and analysis of these structures can shed light on their bioactive cargoes and identify proteins and biomolecules involved in intercellular communication and various physiological processes. Most published methods to isolate ciliary ectosomes are based on their size (100nm to 1μm) to separate cilia-derived vesicles from isolated cilia and/or intact cells. However, it is often difficult to determine the origin of extracellular vesicles and to distinguish ciliary ectosomes from ectosomes budded from the plasma membrane or from exosomes that derive from multivesicular bodies. Here, we describe procedures to isolate and purify ciliary ectosomes from the unicellular green alga, Chlamydomonas reinhardtii, through differential and iodixanol density gradient ultracentrifugation; in this organism, the ciliary membrane is the only membrane directly exposed to the environment and thus ectosomes are of known origin. Ciliary ectosomes contain enzymes and α-amidated peptide products required to mediate peptidergic-signaling cascades; one identified amidated peptide acts as a chemotactic modulator for C. reinhardtii gametes. Classical methods used to assess chemotaxis do not provide quantitative measurements of the chemotactic gradient or the real-time effects on the migration of fast moving cells. Consequently, we developed a chemotaxis assay protocol using microfluidic channel slides that provides quantitative and qualitative measurements of the chemotactic gradient and cell migration. Here, we describe how to establish a stable gradient of a bioactive substance in microfluidic channel slides and perform quantitative assays to assess chemotaxis of both individual cells and populations of C. reinhardtii., (Copyright © 2023 Elsevier Inc. All rights reserved.)

The shrimp Litopenaeus vannamei and Penaeus monodon are arguably the most important commercially farmed crustaceans. While expansion of their aquaculture has classically relied on improvements to rearing facilities, these options have largely been exhausted, and today a shift in focus is occurring, with increased investment in manipulating the shrimp themselves. Hormonal control is one strategy for increasing aquaculture output. However, to use it, one must first understand an animal’s native hormonal systems. Here, transcriptome shotgun assembly (TSA) data were used to expand the peptidomes for L. vannamei and P. monodon . Via an established bioinformatics workflow, 41 L. vannamei and 25 P. monodon pre/preprohormone-encoding transcripts were identified, allowing for the prediction of 158 and 106 distinct peptide structures for these species, respectively. The identified peptides included isoforms of allatostatin A, B and C, as well as members the bursicon, CAPA, CCHamide, crustacean cardioactive peptide, crustacean hyperglycemic hormone, diuretic hormone 31, eclosion hormone, FLRFamide, GSEFLamide, intocin, leucokinin, molt-inhibiting hormone, myosuppressin, neuroparsin, neuropeptide F, orcokinin, orcomyotropin, pigment dispersing hormone, proctolin, red pigment concentrating hormone, RYamide, SIFamide, short neuropeptide F and tachykinin-related peptide families. While some of the predicted peptides are known L. vannamei and/or P. monodon isoforms (which vet the structures of many peptides identified previously via mass spectrometry and other means), most are described here for the first time. These data more than double the extant catalogs of L. vannamei and P. monodon peptides and provide platforms from which to launch future physiological studies of peptidergic signaling in these two commercially important species. [ABSTRACT FROM AUTHOR]

Cilia are sensory and secretory organelles that both receive information from the environment and transmit signals. Cilia-derived vesicles (ectosomes), formed by outward budding of the ciliary membrane, carry enzymes and other bioactive products; this process represents an ancient mode of regulated secretion. Peptidergic intercellular communication controls a wide range of physiological and behavioral responses and occurs throughout eukaryotes. The Chlamydomonas reinhardtii genome encodes what appear to be numerous prepropeptides and enzymes homologous to those used to convert metazoan prepropeptides into bioactive peptide products. Since C. reinhardtii , a green alga, lack the dense core vesicles in which metazoan peptides are processed and stored, we explored the hypothesis that propeptide processing and secretion occur through the regulated release of ciliary ectosomes. A synthetic peptide (GATI- amide ) that could be generated from a 91-kDa peptide precursor (proGATI) serves as a chemotactic modulator, attracting minus gametes while repelling plus gametes. Here we dissect the processing pathway that leads to formation of an amidated peptidergic sexual signal specifically on the ciliary ectosomes of plus gametes. Unlike metazoan propeptides, modeling studies identified stable domains in proGATI. Mass spectrometric analysis of a potential prohormone convertase and the amidated proGATI-derived products found in cilia and mating ectosomes link endoproteolytic cleavage to ectosome entry. Extensive posttranslational modification of proGATI confers stability to its amidated product. Analysis of this pathway affords insight into the evolution of peptidergic signaling; this will facilitate studies of the secretory functions of metazoan cilia.

Summary Placozoans, together with sponges, are the only animals devoid of a nervous system and muscles, yet both respond to sensory stimulation in a coordinated manner. How behavioral control in these free-living animals is achieved in the absence of neurons and, more fundamentally, how the first neurons evolved from more primitive cells for communication during the rise of animals are not yet understood [ 1–5 ]. The placozoan Trichoplax adhaerens is a millimeter-wide, flat, free-living marine animal composed of six morphologically identified cell types distributed across a simple body plan [ 6–9 ]: a thin upper epithelium and a columnar lower epithelium interspersed with a loose layer of fiber cells in between. Its genome contains genes encoding several neuropeptide-precursor-like proteins and orthologs of proteins involved in neurosecretion in animals with a nervous system [ 10–12 ]. Here we investigate peptidergic signaling in T. adhaerens. We found specific expression of several neuropeptide-like molecules in non-overlapping cell populations distributed over the three cell layers, revealing an unsuspected cell-type diversity of T. adhaerens. Using live imaging, we discovered that treatments with 11 different peptides elicited striking and consistent effects on the animals' shape, patterns of movement, and velocity that we categorized under three main types: (1) crinkling, (2) turning, and (3) flattening and churning. Together, the data demonstrate a crucial role for peptidergic signaling in nerveless placozoans and suggest that peptidergic volume signaling may have pre-dated synaptic signaling in the evolution of nervous systems. Highlights • Trichoplax adhaerens expresses several neuropeptides in different cell populations • Treatments with 11 different neuropeptides elicit consistent effects on behavior • Different neuropeptides induced crinkling, turning, or flattening and churning • Neuron-less placozoans have complex peptidergic signaling to regulate behavior Placozoans are simple flat animals that lack a nervous system and muscles. Varoqueaux et al. find that the behavior of the placozoan Trichoplax is influenced by complex chemical signaling. Neuropeptides, secreted molecules produced by neurons in other animals, induce striking changes in the behavior of these neuron-less animals. [ABSTRACT FROM AUTHOR]