title: A biogenic amine and a neuropeptide act identically: tyramine signals through calcium in Drosophila tubule stellate cells.
abstract: Insect osmoregulation is subject to highly sophisticated endocrine control. In Drosophila, both Drosophila kinin and tyramine act on the Malpighian (renal) tubule stellate cell to activate chloride shunt conductance, and so increase the fluid production rate. Drosophila kinin is known to act through intracellular calcium, but the mode of action of tyramine is not known. Here, we used a transgenically encoded GFP::apoaequorin translational fusion, targeted to either principal or stellate cells under GAL4/UAS control, to demonstrate that tyramine indeed acts to raise calcium in stellate, but not principal cells. Furthermore, the EC(50) tyramine concentration for half-maximal activation of the intracellular calcium signal is the same as that calculated from previously published data on tyramine-induced increase in chloride flux. In addition, tyramine signalling to calcium is markedly reduced in mutants of NorpA (a phospholipase C) and itpr, the inositol trisphosphate receptor gene, which we have previously shown to be necessary for Drosophila kinin signalling. Therefore, tyramine and Drosophila kinin signals converge on phospholipase C, and thence on intracellular calcium; and both act to increase chloride shunt conductance by signalling through itpr. To test this model, we co-applied tyramine and Drosophila kinin, and showed that the calcium signals were neither additive nor synergistic. The two signalling pathways thus represent parallel, independent mechanisms for distinct tissues (nervous and epithelial) to control the same aspect of renal function.
authors: Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
authors: Pablo
authors: P
authors: Cabrero
authors: Laura
authors: L
authors: Richmond
authors: Michael
authors: M
authors: Nitabach
authors: Shireen A
authors: SA
authors: Davies
authors: Julian A T
authors: JA
authors: Dow
mesh_terms: D000331:Aequorin / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001059:Apoproteins / Q000235:genetics / Q000378:metabolism; D020013:Calcium Signaling; D002712:Chlorides / Q000378:metabolism; D029721:Drosophila Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D004331:Drosophila melanogaster / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000032:analysis; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics; D008317:Malpighian Tubules / Q000166:cytology / Q000378:metabolism; D008954:Models, Biological; D009479:Neuropeptides / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D054799:Phospholipase C beta / Q000235:genetics; D015202:Protein Engineering; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014439:Tyramine / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D014882:Water-Electrolyte Balance / Q000502:physiology
chemical_list: D001059:Apoproteins; D002712:Chlorides; D029721:Drosophila Proteins; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009479:Neuropeptides; D011994:Recombinant Proteins; C060014:apoaequorin; D049452:Green Fluorescent Proteins; D000331:Aequorin; C468371:NorpA protein, Drosophila; D054799:Phospholipase C beta; D014439:Tyramine