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Hyperprolinaemia caused by novel members of the adipokinetic hormone/red pigment-concentrating hormone family of peptides isolated from corpora cardiaca of onitine beetles.

ABSTRACT: Two novel members of the adipokinetic hormone/red pigment-concentrating hormone family of peptides were identified in dung beetles of the genus Onitis using heterologous (measuring lipid and carbohydrate mobilization in locusts and cockroaches) and a homologous (measuring proline increase in the haemolymph) bioassay(s). Isolation of the peptides was achieved by single-step reverse-phase HPLC of corpora cardiaca extracts. The primary structure was elucidated by automated Edman degradation and by electrospray MS. Both peptides are blocked octapeptides containing three aromatic amino acids. Peptide 1, designated Ona-CC-I, is pGlu-Tyr-Asn-Phe-Ser-Thr-Gly-Trp-NH2, and peptide 2, designated Ona-CC-II, is pGlu-Phe-Asn-Tyr-Ser-Pro-Asp-Trp-NH2. The synthetic peptides were chromatographically indistinguishable from the natural compounds. They both had a hyperprolinaemic effect in the dung beetle. Moreover, flight experiments established that proline is an important fuel to power flight metabolism in Onitis species. Therefore, it is concluded that these novel and unique peptides are involved in regulating proline-based flight metabolism.

SUBMITTER: Gade G

PROVIDER: S-EPMC1218054 | biostudies-other | 1997 Jan

REPOSITORIES: biostudies-other

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Project description:Neuropeptides play a central role as neurotransmitters, neuromodulators and hormones in orchestrating arthropod physiology. The post-genomic surge in identified neuropeptides and their putative receptors has not been matched by functional characterization of ligand-receptor pairs. Indeed, until very recently no G protein-coupled receptors (GPCRs) had been functionally defined in any crustacean. Here we explore the structurally-related, functionally-diverse gonadotropin-releasing hormone paralogs, corazonin (CRZ) and red-pigment concentrating hormone (RPCH) and their G-protein coupled receptors (GPCRs) in the crab, Carcinus maenas. Using aequorin luminescence to measure in vitro Ca2+ mobilization we demonstrated receptor-ligand pairings of CRZ and RPCH. CRZR-activated cell signaling in a dose-dependent manner (EC50 0.75 nM) and comparative studies with insect CRZ peptides suggest that the C-terminus of this peptide is important in receptor-ligand interaction. RPCH interacted with RPCHR with extremely high sensitivity (EC50 20 pM). Neither receptor bound GnRH, nor the AKH/CRZ-related peptide. Transcript distributions of both receptors indicate that CRZR expression was, unexpectedly, restricted to the Y-organs (YO). Application of CRZ peptide to YO had no effect on ecdysteroid biosynthesis, excepting a modest stimulation in early post-molt. CRZ had no effect on heart activity, blood glucose levels, lipid mobilization or pigment distribution in chromatophores, a scenario that reflected the distribution of its mRNA. Apart from the well-known activity of RPCH as a chromatophorotropin, it also indirectly elicited hyperglycemia (which was eyestalk-dependent). RPCHR mRNA was also expressed in the ovary, indicating possible roles in reproduction. The anatomy of CRZ and RPCH neurons in the nervous system is described in detail by immunohistochemistry and in situ hybridization. Each peptide has extensive but non-overlapping distribution in the CNS, and neuroanatomy suggests that both are possibly released from the post-commissural organs. This study is one of the first to deorphanize a GPCR in a crustacean and to provide evidence for hitherto unknown and diverse functions of these evolutionarily-related neuropeptides.

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Hyperprolinaemia caused by novel members of the adipokinetic hormone/red pigment-concentrating hormone family of peptides isolated from corpora cardiaca of onitine beetles.

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