The role of Ins(1,4,5)P(3) in signal transduction of the metabolic neuropeptide Mem-CC in the cetoniid beetle, Pachnoda sinuata.
We have investigated the role of inositol triphosphate, Ins(1,4,5)P(3), in the transduction of the hypertrehalosaemic and hyperprolinaemic signal of the endogenous neuropeptide Mem-CC in the cetoniid beetle Pachnoda sinuata. Flight and injection of Mem-CC into the haemocoel of the beetle induce an increase of Ins(1,4,5)P(3) levels in the fat body of the beetle. When Mem-CC is co-injected with U 73122, which is an inhibitor of phospholipase C, this effect is abolished. Mem-CC also elevates Ins(1,4,5)P(3) concentration in fat body pieces in vitro. The increase in Ins(1,4,5)P(3) levels is tissue-specific and does not occur in brain and flight muscles. Elevation of the Ins(1,4,5)P(3) levels upon injection of Mem-CC is time- and dose-dependent: the maximum response is reached after 3 min and a dose of 10 pmol is needed. Compounds that mimic the action of cAMP (cpt-cAMP, forskolin) do not influence the concentration of Ins(1,4,5)P(3), while those that stimulate G-proteins (aluminium fluoride and cholera toxin) cause an increase of Ins(1,4,5)P(3) levels. The application (in vivo and in vitro) of F-Ins(1,4,5)P(3), an Ins(1,4,5)P(3) analogue that penetrates the cell membrane, causes a mobilisation of carbohydrate reserves via the activation of glycogen phosphorylase but does not stimulate proline synthesis. In addition, U 73122 abolishes the hypertrehalosaemic but not the hyperprolinaemic effect of Mem-CC. The results suggest that the hypertrehalosaemic signal of Mem-CC is mediated via an increase of Ins(1,4,5)P(3) levels in the fat body of P. sinuata.
Auerswald
Lutz
L
Zoology Department, University of Cape Town, Rondebosch 7701, South Africa. lauerswa@botzoo.uct.ac.za
Gäde
Gerd
G
D000818:Animals; D001517:Coleoptera / Q000502:physiology*; D005426:Flight, Animal; D024981:Glycogen Phosphorylase / Q000378:metabolism; D006458:Hemolymph / Q000502:physiology; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D007301:Insect Hormones / Q000502:physiology*; D008297:Male; D009479:Neuropeptides / Q000502:physiology*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D015398:Signal Transduction / Q000502:physiology*
D007301:Insect Hormones; D009479:Neuropeptides; C069011:adipokinetic hormone, beetle; D015544:Inositol 1,4,5-Trisphosphate; D024981:Glycogen Phosphorylase; D011761:Pyrrolidonecarboxylic Acid