Allatostatin II

C-type allatostatins (AST-Cs) are pleiotropic neuropeptides that are broadly conserved within arthropods; the presence of three AST-C isoforms, encoded by paralog genes, is common. However, these peptides are hypothesized to act through a single receptor, thereby exerting similar bioactivities within each species. We investigated this hypothesis in the American lobster, Homarus americanus, mapping the distributions of AST-C isoforms within relevant regions of the nervous system and digestive tract, and comparing their modulatory influences on the cardiac neuromuscular system. Immunohistochemistry showed that in the pericardial organ, a neuroendocrine release site, AST-C I and/or III and AST-C II are contained within distinct populations of release terminals. Moreover, AST-C I/III-like immunoreactivity was seen in midgut epithelial endocrine cells and the cardiac ganglion (CG), whereas AST-C II-like immunoreactivity was not seen in these tissues. These data suggest that AST-C I and/or III can modulate the CG both locally and hormonally; AST-C II likely acts on the CG solely as a hormonal modulator. Physiological studies demonstrated that all three AST-C isoforms can exert differential effects, including both increases and decreases, on contraction amplitude and frequency when perfused through the heart. However, in contrast to many state-dependent modulatory changes, the changes in contraction amplitude and frequency elicited by the AST-Cs were not functions of the baseline parameters. The responses to AST-C I and III, neither of which is COOH-terminally amidated, are more similar to one another than they are to the responses elicited by AST-C II, which is COOH-terminally amidated. These results suggest that the three AST-C isoforms are differentially distributed in the lobster nervous system/midgut and can elicit distinct behaviors from the cardiac neuromuscular system, with particular structural features, e.g., COOH-terminal amidation, likely important in determining the effects of the peptides. NEW & NOTEWORTHY Multiple isoforms of many peptides exert similar effects on neural circuits. In this study we show that each of the three isoforms of C-type allatostatin (AST-C) can exert differential effects, including both increases and decreases in contraction amplitude and frequency, on the lobster cardiac neuromuscular system. The distribution of effects elicited by the nonamidated isoforms AST-C I and III are more similar to one another than to the effects of the amidated AST-C II.

Neuropeptides and peptide hormones are essential signaling molecules that regulate nearly all physiological processes. The recent release of the tsetse fly genome allowed the construction of a detailed in silico neuropeptide database (International Glossina Genome Consortium, Science 344, 380-386 (2014)), as well as an in-depth mass spectrometric analysis of the most important neuropeptidergic tissues of this medically and economically important insect species. Mass spectrometric confirmation of predicted peptides is a vital step in the functional characterization of neuropeptides, as in vivo peptides can be modified, cleaved, or even mispredicted. Using a nanoscale reversed phase liquid chromatography coupled to a Q Exactive Orbitrap mass spectrometer, we detected 51 putative bioactive neuropeptides encoded by 19 precursors: adipokinetic hormone (AKH) I and II, allatostatin A and B, capability/pyrokinin (capa/PK), corazonin, calcitonin-like diuretic hormone (CT/DH), FMRFamide, hugin, leucokinin, myosuppressin, natalisin, neuropeptide-like precursor (NPLP) 1, orcokinin, pigment dispersing factor (PDF), RYamide, SIFamide, short neuropeptide F (sNPF) and tachykinin. In addition, propeptides, truncated and spacer peptides derived from seven additional precursors were found, and include the precursors of allatostatin C, crustacean cardioactive peptide, corticotropin releasing factor-like diuretic hormone (CRF/DH), ecdysis triggering hormone (ETH), ion transport peptide (ITP), neuropeptide F, and proctolin, respectively. The majority of the identified neuropeptides are present in the central nervous system, with only a limited number of peptides in the corpora cardiaca-corpora allata and midgut. Owing to the large number of identified peptides, this study can be used as a reference for comparative studies in other insects. Graphical Abstract ᅟ.

Here we describe the neuronal organization of the arcuate body in the brain of the wandering spider Cupiennius salei. The internal anatomy of this major brain center is analyzed in detail based on allatostatin-, proctolin-, and crustacean cardioactive peptide (CCAP)-immunohistochemistry. Prominent neuronal features are demonstrated in graphic reconstructions. The stainings revealed that the neuroarchitecture of the arcuate body is characterized by several distinct layers some of which comprise nerve terminals that are organized in columnar, palisade-like arrays. The anatomy of the spider's arcuate body exhibits similarities as well as differences when compared to the central complex in the protocerebrum of the Tetraconata. Arguments for and against a possible homology of the arcuate body of the Chelicerata and the central complex of the Tetraconata and their consequences for the understanding of arthropod brain evolution are discussed.

The role of the YXFGLa family of allatostatin (AST) peptides in dipterans is not well-established. The recent completion of sequencing of genomes for multiple Drosophila species provides an opportunity to study the evolutionary variation of the allatostatins and to examine regulatory elements that control gene expression. We performed comparative analyses of Ast genes from seven Drosophila species (Drosophila melanogaster, Drosophila simulans, Drosophila ananassae, Drosophila yakuba, Drosophila pseudoobscura, Drosophila mojavensis, and Drosophila grimshawi) and used phylogenetic footprinting methods to identify conserved noncoding motifs, which are candidates for regulatory regions. The peptides encoded by the Ast precursor are nearly identical across species with the exception of AST-1, in which the leading residue may be either methionine or valine. Phylogenetic footprinting predicts as few as 3, to as many as 17 potential regulatory sites depending on the parameters used during analysis. These include a Hunchback motif approximately 1.2 kb upstream of the open reading frame (ORF), overlapping motifs for two Broad-complex isoforms in the first intron, and a CF2-II motif located in the 3'-UTR. Understanding the regulatory elements involved in Ast expression may provide insight into the function of this neuropeptide family.