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APEASPFIRFamide, a novel FMRFamide-related decapeptide from Caenorhabditis elegans: structure and myoactivity
N J Marks1, A G Maule, T G Geary
1Comparative Neuroendocrinology Research Group, Queen's University of Belfast, Northern Ireland.
Abstract:
To date, 9 FMRFamide-related peptides (FaRPs) have been identified in Caenorhabditis elegans. Eight of these peptides are encoded on the flp-1 gene. However, AF2 (KHEYLRFamide) which was not co-encoded was the most abundant FaRP identified in ethanolic extracts. Further radioimmunometrical screening of acidified ethanol extracts of C. elegans has revealed the presence of other novel FaRPs, which are not encoded on the flp-1 gene. One of these peptides has been isolated by sequential rpHPLC and subjected to Edman degradation analysis and gas-phase sequencing and the unequivocal primary structure of the decapeptide Ala-Pro-Glu-Ala-Ser-Pro-Phe-Ile-Arg-Phe-NH2 was determined following a single gas-phase sequencing run. The molecular mass of the peptide was found to be 1133.7 Da, determined using a time-of-flight mass spectrometer. Synthetic replicates of this peptide were found to induce a profound relaxation of both dorsal and ventral somatic muscle-strip preparations of Ascaris suum with a threshold for activity of 10 nM. The inhibitory response was not dependent on the presence of nerve cords, indicating a post-synaptic site-of-action. The relaxation was Ca(+2)- and Cl(-)-independent but was abolished in high-K+ medium and could be distinguished from those of other inhibitory nematode FaRPs, including PF1 (SDPNFLRFamide) and PF4 (KPNFIRFamide).
Insights
Researchers identified a novel FMRFamide-related peptide (FaRP) in C. elegans not encoded by the flp-1 gene. This new peptide induces muscle relaxation in Ascaris suum, suggesting a post-synaptic inhibitory role.
Area of Science:
- * Neurobiology and peptide signaling in nematodes.
Background:
- * Nine FMRFamide-related peptides (FaRPs) are known in C. elegans, with eight encoded by the flp-1 gene.
- * AF2 (KHEYLRFamide), an unencoded FaRP, is highly abundant, prompting further investigation into other non-flp-1 encoded FaRPs.
Purpose of the Study:
- * To identify and characterize novel FMRFamide-related peptides (FaRPs) in C. elegans.
- * To determine the primary structure and biological activity of a newly identified FaRP.
Main Methods:
- * Radioimmunometrical screening of C. elegans extracts.
- * Peptide isolation using sequential reversed-phase high-performance liquid chromatography (rpHPLC).
- * Primary structure determination via Edman degradation and gas-phase sequencing.
- * Mass determination using time-of-flight mass spectrometry.
- * Pharmacological characterization using Ascaris suum muscle-strip preparations.
Main Results:
- * A novel decapeptide, Ala-Pro-Glu-Ala-Ser-Pro-Phe-Ile-Arg-Phe-NH2 (molecular mass 1133.7 Da), was identified.
- * Synthetic replicates induced profound relaxation in Ascaris suum somatic muscle strips (threshold 10 nM).
- * The relaxation was post-synaptic, Ca(+2)- and Cl(-)-independent, but abolished in high-K+ medium.
Conclusions:
- * A novel, non-flp-1 encoded FaRP with significant muscle relaxant properties was discovered in C. elegans.
- * This peptide exhibits distinct pharmacological characteristics compared to other known inhibitory nematode FaRPs.
- * The findings expand the known repertoire of nematode neuropeptides and their physiological functions.