Peptide products of the afp‐6 gene of the nematode Ascaris suum have different biological actions

Abstract

Matrix-assisted laser desorption/ionization time-of-flight and tandem time-of-flight (MALDI-TOF and MALDI-TOF/TOF) mass spectrometry were used to sequence and localize three novel, related neuropeptides in the nervous system of the nematode Ascaris suum, AMRNALVRFamide (AF21), NGAPQPFVRFamide (AF22), and SGMRNALVRFamide (AF23). The amino acid sequences were used to clone a novel neuropeptide gene (afp-6) that encodes a precursor bearing a single copy of each of the peptides. In situ hybridization and immunocytochemistry revealed that both the transcript and the peptides are expressed in a single cell in the ventral ganglion. Pharmacological studies of intact nematodes injected with these peptides, as well as physiological studies of responses to them in muscle tissue, motor neurons, and the pharynx, reveal that these peptides have potent bioactivity in the locomotory and feeding systems. Further exploration of their effects may contribute to our understanding of neuropeptide modulation of behavior and also to the development of compounds with anthelmintic relevance.

The FMRFamide-Like Peptide Family in Nematodes

“…These results are consistent with the fact that the majority of excitatory and inhibitory peptides were encoded on genes shown to be expressed in the C. elegans pharyngeal nervous system (23). It therefore appears that multiple FLPs are involved in feeding behavior by modulating pharyngeal activity, as supported by findings in A. suum (54, 130–132). Using a modified pressure transducer, Brownlee and colleagues measured changes in intrapharyngeal pressure to monitor the contraction of the Ascaris radial pharynx muscle.…”

“…In situ hybridization (ISH), which uses nucleotide probes complementary to specific gene transcripts, offers an attractive alternative to delineate flp gene expression in other nematodes that are less amenable to transgenesis than C. elegans (38, 42, 54, 75). Furthermore, as immunochemistry allows the determination of neurite morphology facilitating neuronal identification, several antibodies highly specific to certain A. suum FLPs were recently generated (42, 76).…”

“…Diverse inhibitory and excitatory activities have been reported in A. suum on body wall muscles upon the application of FLPs (54, 91, 133–136). Data obtained from this type of studies do, however, not always facilitate a better understanding of in vivo physiological functions.…”

A review of FMRFamide- and RFamide-like peptides in metazoa

“…In addition, Yew et al have identified a gene, which they termed afp-5 in A. suum, which encodes AF-17, which does not appear to have an equivalent in C. elegans. Recently, the gene that encodes AF-21, AF-22 and AF-23 has been cloned from A. suum and termed afp-6 (Yew et al 2007). This gene is equivalent to flp-11 of C. elegans and following on from McVeigh's nomenclature should be termed As-flp-11.…”

Different Neuropeptides Are Expressed in Different Functional Subsets of Cholinergic Excitatory Motorneurons in the Nematode Ascaris suum

“…14, 18, 19 More recently, we have used mass spectrometry (MS) to detect and then to sequence neuropeptides. 12, 13, 17, 20–22 We have now extended this technique to the single cell level; mass spectrometric methods are sensitive enough both to detect and to sequence peptides from single dissected neurons. 17, 20 This approach is limited only by how successfully we can dissect single neurons.…”