Neuropeptide F: a novel parasitic flatworm regulatory peptide from Moniezia expansa (Cestoda: Cyclophyllidea)

Abstract

SUMMARYUsing a C-terminally directed pancreatic polypeptide (PP) antiserum and immunocytochemical methods, PP-immuno-reactivity (IR) was localized throughout the central (CNS) and peripheral nervous systems (PNS) of the cestode, Moniezia expansa. In the CNS, immunostaining was evident in the paired cerebral ganglia (primitive brain), connecting commissure, and the paired longitudinal nerve cords that are cross-linked by numerous regular transverse connectives. The PNS was seen to consist of a fine anastomosing nerve-net of immunoreactive fibres, many of which were closely associated with reproductive structures. Radioimmunoassay of this peptide IR in acid-alcohol extracts of the worm measured 192·8 ng/g of PP–IR. HPLC analyses of the M. expansa PP–IR identified a single molecular form which was purified to homogeneity. Plasma desorption mass spectrometry (PDMS) of purified parasite peptide resolved a single peptide with a molecular mass of 4599±10 Da. Automated gas-phase Edman degradation identified a 39-amino acid peptide with a C-terminal phenyl-alaninamide. Examination of its primary structure shows that it displays significant sequence homology with the vertebrate neuropeptide Y superfamily, suggesting that this platyhelminth-derived peptide is the phylogenetic precursor. Neuropeptide F (M. expansa) is the first regulatory peptide to be fully sequenced from the phylum Platyhelminthes and may represent a member of an important new class of invertebrate neuropeptide.

Structure and Bioactivity of Neuropeptide F from the Human Parasites Schistosoma mansoni and Schistosoma japonicum

“…SignalP analysis finds a signal peptide in each of the possible schistosome prepro-NPFs, with the exception of the potential 147-amino acid S. mansoni prepro-NPF. In mxNPF, the only other NPF identified thus far in a parasitic platyhelminth, the amino terminus of the 40-amino acid mature peptide is generated by cleavage at a single basic residue (11,25). Both schistosome prepro-NPFs have a single basic residue at a site that would generate a 36-amino acid mature peptide (Fig.…”

“…Fraction aliquots (10 l) were monitored by using a neuropeptide F radioimmunoassay that employed an antiserum raised against the carboxyl-terminal decapeptide (YFAIIGRPRF-NH 2 ) of Moniezia expansa NPF (11). The assay sensitivity was 17 fmol of NPF per assay tube.…”

“…Second, if the schistosome prepro-NPFs are processed like the only other known parasitic flatworm NPF, the 36-amino acid mature peptide would result. For M. expansa, because both the cDNA and mature peptide have been identified (11,25), it is known that cleavage at a single basic residue produces the amino terminus of the mature peptide. Both schistosome prepro-NPFs have a single basic residue where cleavage would produce the 36-amino acid mature peptide.…”

“…One distinct feature of platyhelminths and other early diverging phyla is a prominent peptidergic component within their nervous systems. One family of neuropeptides abundant among these early animals is the neuropeptide F (NPF) family (11)(12)(13)(14). NPFs are 36 -40-amino acid peptides featuring a carboxyl-terminal Gly-Arg-X-Arg-Phe-amide (GRXRF-NH 2 ) motif and tyrosine residues at positions 10 and 17 relative to the carboxyl terminus.…”

“…These structural similarities were the basis of the discovery of invertebrate NPFs, as they were first localized using antisera targeting the carboxyl termini of NPY family neuropeptides (11). The striking structural similarities between NPY family peptides and NPFs notwithstanding, the evolutionary relationship between these neuropeptides is not yet clear.…”