title: Signaling of reactive oxygen species in PTTH-stimulated ecdysteroidogenesis in prothoracic glands of the silkworm, Bombyx mori.
abstract: Our previous study demonstrated that mitochondria-derived reactive oxygen species (ROS) generation is involved in prothoracicotropic hormone (PTTH)-stimulated ecdysteroidogenesis in Bombyx mori prothoracic glands (PGs). In the present study, we further investigated the mechanism of ROS production and the signaling pathway mediated by ROS. PTTH-stimulated ROS production was markedly attenuated in a Ca(2+)-free medium. The phospholipase C (PLC) inhibitor, U73122, greatly inhibited PTTH-stimulated ROS production, indicating the involvement of Ca(2+) and PLC. When the PGs were treated with agents that directly elevate the intracellular Ca(2+) concentration (either A23187, or the protein kinase C (PKC) activator, phorbol 12-myristate acetate (PMA)), a great increase in ROS production was observed. We further investigated the action mechanism of PTTH-stimulated ROS signaling. Results showed that in the presence of either an antioxidant (N-acetylcysteine, NAC), or the mitochondrial oxidative phosphorylation inhibitors (rotenone, antimycin A, the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP), and diphenyleneiodonium (DPI)), PTTH-regulated phosphorylation of ERK, 4E-BP, and AMPK was blocked. Treatment with 1mM of H2O2 alone activated the phosphorylation of ERK and 4E-BP, and inhibited AMPK phosphorylation. From these results, we conclude that PTTH-stimulated ROS signaling is Ca(2+)- and PLC-dependent and that ROS signaling appears to lie upstream of the phosphorylation of ERK, 4E-BP, and AMPK.
authors.affiliation: Department of Biology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung 404, Taiwan, ROC.
authors.forename: Yun-Chih
authors.initials: YC
authors.lastname: Hsieh
authors.affiliation: Department of Biology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung 404, Taiwan, ROC.
authors.forename: Pei-Ling
authors.initials: PL
authors.lastname: Lin
authors.affiliation: Department of Biology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung 404, Taiwan, ROC. Electronic address: gu330@mail.nmns.edu.tw.
authors.forename: Shi-Hong
authors.initials: SH
authors.lastname: Gu
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000818:Animals; D012831:Bombyx / Q000254:growth & development / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D026461:Ecdysteroids / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D007301:Insect Hormones / Q000378:metabolism*; D019476:Insect Proteins / Q000378:metabolism*; D007814:Larva / Q000502:physiology; D010084:Oxidation-Reduction; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000378:metabolism*
chemical_list: D026461:Ecdysteroids; D007301:Insect Hormones; D019476:Insect Proteins; D017382:Reactive Oxygen Species; C009089:prothoracicotropic hormone; D048049:Extracellular Signal-Regulated MAP Kinases; D055372:AMP-Activated Protein Kinases; D010738:Type C Phospholipases; D002118:Calcium
keywords: Bombyx mori; Ca(2+); Ecdysone; PTTH; Prothoracic glands; ROS signaling