title: Mechanism and function of Drosophila capa GPCR: a desiccation stress-responsive receptor with functional homology to human neuromedinU receptor.
abstract: The capa peptide receptor, capaR (CG14575), is a G-protein coupled receptor (GPCR) for the D. melanogaster capa neuropeptides, Drm-capa-1 and -2 (capa-1 and -2). To date, the capa peptide family constitutes the only known nitridergic peptides in insects, so the mechanisms and physiological function of ligand-receptor signalling of this peptide family are of interest. Capa peptide induces calcium signaling via capaR with EC₅₀ values for capa-1 = 3.06 nM and capa-2 = 4.32 nM. capaR undergoes rapid desensitization, with internalization via a b-arrestin-2 mediated mechanism but is rapidly re-sensitized in the absence of capa-1. Drosophila capa peptides have a C-terminal -FPRXamide motif and insect-PRXamide peptides are evolutionarily related to vertebrate peptide neuromedinU (NMU). Potential agonist effects of human NMU-25 and the insect -PRLamides [Drosophila pyrokinins Drm-PK-1 (capa-3), Drm-PK-2 and hugin-gamma [hugg]] against capaR were investigated. NMU-25, but not hugg nor Drm-PK-2, increases intracellular calcium ([Ca²⁺]i) levels via capaR. In vivo, NMU-25 increases [Ca²⁺]i and fluid transport by the Drosophila Malpighian (renal) tubule. Ectopic expression of human NMU receptor 2 in tubules of transgenic flies results in increased [Ca²⁺]i and fluid transport. Finally, anti-porcine NMU-8 staining of larval CNS shows that the most highly immunoreactive cells are capa-producing neurons. These structural and functional data suggest that vertebrate NMU is a putative functional homolog of Drm-capa-1 and -2. capaR is almost exclusively expressed in tubule principal cells; cell-specific targeted capaR RNAi significantly reduces capa-1 stimulated [Ca²⁺]i and fluid transport. Adult capaR RNAi transgenic flies also display resistance to desiccation. Thus, capaR acts in the key fluid-transporting tissue to regulate responses to desiccation stress in the fly.
authors.affiliation: Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom. Selim.Terhzaz@glasgow.ac.uk
authors.forename: Selim
authors.initials: S
authors.lastname: Terhzaz
authors.forename: Pablo
authors.initials: P
authors.lastname: Cabrero
authors.forename: Joris H
authors.initials: JH
authors.lastname: Robben
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Radford
authors.forename: Brian D
authors.initials: BD
authors.lastname: Hudson
authors.forename: Graeme
authors.initials: G
authors.lastname: Milligan
authors.forename: Julian A T
authors.initials: JA
authors.lastname: Dow
authors.forename: Shireen-A
authors.initials: SA
authors.lastname: Davies
mesh_terms: D000331:Aequorin / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001059:Apoproteins / Q000378:metabolism; D020013:Calcium Signaling; D003890:Desiccation; D029721:Drosophila Proteins / Q000737:chemistry / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000378:metabolism*; D004705:Endocytosis; D055785:Gene Knockdown Techniques; D006801:Humans; D007150:Immunohistochemistry; D008317:Malpighian Tubules / Q000378:metabolism; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000737:chemistry / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000737:chemistry / Q000378:metabolism*; D017981:Receptors, Neurotransmitter / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological
chemical_list: D001059:Apoproteins; C572391:CapaR protein, Drosophila; D029721:Drosophila Proteins; D009479:Neuropeptides; D043562:Receptors, G-Protein-Coupled; D017981:Receptors, Neurotransmitter; C455043:capa protein, Drosophila; C082444:neuromedin U receptor; C056900:neuromedin U; D000331:Aequorin