Identification of the novel bioactive peptides dRYamide-1 and dRYamide-2, ligands for a neuropeptide Y-like receptor in Drosophila.

A number of bioactive peptides are involved in regulating a wide range of animal behaviors, including food consumption. Vertebrate neuropeptide Y (NPY) is a potent stimulator of appetitive behavior. Recently, Drosophila neuropeptide F (dNPF) and short NPF (sNPF), the Drosophila homologs of the vertebrate NPY, were identified to characterize the functions of NPFs in the feeding behaviors of this insect. Dm-NPFR1 and NPFR76F are the receptors for dNPF and sNPF, respectively; both receptors are G protein-coupled receptors (GPCRs). Another GPCR (CG5811; NepYR) was indentified in Drosophila as a neuropeptide Y-like receptor. Here, we identified 2 ligands of CG5811, dRYamide-1 and dRYamide-2. Both peptides are derived from the same precursor (CG40733) and have no significant structural similarities to known bioactive peptides. The C-terminal sequence RYamide of dRYamides is identical to that of NPY family peptides; on the other hand, dNPF and sNPF have C-terminal RFamide. When administered to blowflies, dRYamide-1 suppressed feeding motivation. We propose that dRYamides are related to the NPY family in vertebrates, similar to dNPF and sNPF.

Isolation of the bioactive peptides CCHamide-1 and CCHamide-2 from Drosophila and their putative role in appetite regulation as ligands for G protein-coupled receptors.

There are many orphan G protein-coupled receptors (GPCRs) for which ligands have not yet been identified. One such GPCR is the bombesin receptor subtype 3 (BRS-3). BRS-3 plays a role in the onset of diabetes and obesity. GPCRs in invertebrates are similar to those in vertebrates. Two Drosophila GPCRs (CG30106 and CG14593) belong to the BRS-3 phylogenetic subgroup. Here, we succeeded to biochemically purify the endogenous ligands of Drosophila CG30106 and CG14593 from whole Drosophila homogenates using functional assays with the reverse pharmacological technique, and identified their primary amino acid sequences. The purified ligands had been termed CCHamide-1 and CCHamide-2, although structurally identical to the peptides recently predicted from the genomic sequence searching. In addition, our biochemical characterization demonstrated two N-terminal extended forms of CCHamide-2. When administered to blowflies, CCHamide-2 increased their feeding motivation. Our results demonstrated these peptides actually present as the major components to activate these receptors in living Drosophila. Studies on the effects of CCHamides will facilitate the search for BRS-3 ligands.

Mechanoreceptors involved in the hindwing-evoked escape behaviour in cricket, Gryllus bimaculatus.

Mechanoreceptors involved in the escape jumping evoked by hindwing stimulation have been investigated in the field cricket Gryllus bimaculatus. By partial ablation of the hindwing, we found that a mechanosensory system relevant to the escape behaviour was localized on specific veins of the hindwing tip. Scanning electron microscopy revealed three types of mechanoreceptive sensillae on the corresponding region. Based on their morphology, type I and type III sensillae were judged to be trichoid and chaetic sensillae, respectively. Type II sensillae were newly found in this study, having a twisted shaft with a socket-like structure at its base. They existed almost exclusively on the tip and middle regions of the hindwing. The conduction velocity of type II units was significantly smaller than that of type I units. One cycle of sinusoidal deflection of a single type II sensilla at frequencies in the range of 10-120 Hz caused the sensory unit to discharge a single or a few spikes that were not directly correlated with any specific direction of hair movement nor specific deflection angle. The response probability decreased with the stimulus frequency to be less than 0.1 at 0.2 Hz. The results suggest that type II sensillae would serve as contact mechanoreceptors with a low-cut filter property to obtain general information on the presence of stimuli on the hindwing tip rather than specific information on their precise positioning or movement.