title: Regulation of histone H3 phosphorylation at serine 10 in PTTH-stimulated prothoracic glands of the silkworm, Bombyx mori.
abstract: A complex signaling network appears to be involved in prothoracicotropic hormone (PTTH)-stimulated ecdysteroidogenesis in insect prothoracic glands (PGs). In the present study, we investigated the localization of phosphorylated extracellular signal-regulated kinase (ERK) in PTTH-stimulated PGs in Bombyx mori. The nuclear effect of PTTH was further studied by examining phosphorylation of histone H3 at serine 10. Results showed that in PTTH-stimulated PGs, higher phosphorylated ERK was detected in nuclear fraction compared to that in cytosolic fraction. PTTH treatment in vitro appears to rapidly enhance the transcriptional activation-associated histone H3 phosphorylation at serine 10. PTTH stimulated histone H3 phosphorylation in a time-dependent manner. Injection of PTTH into day-6 last instar larvae greatly increased histone H3 phosphorylation, verifying the in vitro effect. The stimulation of histone H3 phosphorylation by PTTH appears to be developmentally regulated. PTTH-stimulated histone H3 phosphorylation was greatly reduced in Ca(2+)-free saline or by pretreatment with a potent and specific inhibitor of phospholipase C (PLC), U73122. When PGs were treated with agents that directly elevate the intracellular Ca(2+) concentration (either A23187 or thapsigargin), a greatly increase in histone H3 phosphorylation at serine 10 was observed, indicating Ca(2+)-dependency of histone H3 phosphorylation stimulated by PTTH. In addition, PTTH-stimulated histone H3 phosphorylation was partially reduced by U0126, a specific mitogen-activated protein kinase (MAPK)/ERK kinase (MEK) inhibitor, indicating the involvement of ERK. However, pretreatment with LY294002, a phosphoinositide 3-kinase (PI3K) inhibitor, did not inhibit PTTH-stimulated histone H3 phosphorylation, implying that PI3K signaling is not related to PTTH-stimulated histone H3 phosphorylation. Taken together, these results suggest that PTTH-stimulated histone H3 phosphorylation at serine 10 is mediated by Ca(2+)/ERK signaling in B. mori PGs.
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
authors.affiliation: Department of Biology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung 404, Taiwan, ROC.
authors.forename: Yun-Chin
authors.initials: YC
authors.lastname: Hsieh
mesh_terms: D000818:Animals; D012831:Bombyx / Q000201:enzymology* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D003593:Cytoplasm; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D007301:Insect Hormones / Q000378:metabolism*; D007814:Larva / Q000201:enzymology / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D015533:Transcriptional Activation
chemical_list: D006657:Histones; D007301:Insect Hormones; D012694:Serine; C009089:prothoracicotropic hormone; D019869:Phosphatidylinositol 3-Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D002118:Calcium
keywords: Bombyx mori; ERK; Ecdysone; Epigenetic regulation; Histone H3 phosphorylation at serine 10; PTTH; Prothoracic gland