title: Target of rapamycin-dependent activation of S6 kinase is a central step in the transduction of nutritional signals during egg development in a mosquito.
abstract: Female mosquitoes are effective disease vectors, because they take blood from vertebrate hosts to obtain nutrients for egg development. Amino acid signaling via the target of rapamycin (TOR) pathway has been identified as a key requirement for the activation of egg development after a blood meal. We report the characterization of the TOR kinase and one of its major downstream targets, S6 kinase, of the yellow fever mosquito Aedes aegypti during egg development in adult females. Both TOR and S6K mRNA are expressed at high levels in the ovaries and in lower levels in fat body and other tissues. After a blood meal, the subcellular localization of TOR shifts from the cytoplasm to the plasma membrane of fat body cells. By detecting phosphothreonine 388 of mosquito S6 kinase, we show that TOR activity strongly increases in fat body and ovaries after a blood meal in vivo. Furthermore, phosphorylation of S6 kinase increases in in vitro cultured fat bodies after stimulation with amino acids. This increase is sensitive to the TOR inhibitor rapamycin in a concentration-dependent manner but not to the phosphatidylinositol 3-kinase/phosphatidylinositol 3-kinase-related kinase inhibitor LY294002, the MAPK inhibitor PD98059, or the translational inhibitor cycloheximide. RNA interference-mediated reduction of S6 kinase strongly inhibits the amino acid-induced up-regulation of the major yolk protein vitellogenin in vitro and effectively disrupts egg development after a blood meal in vivo. Our data show that TOR-dependent activation of S6 kinase is a central step in the transduction of nutritional information during egg development in mosquitoes.
authors.affiliation: Department of Entomology and Institute for Integrative Genome Biology, University of California, Riverside, California 92521, USA.
authors.forename: Immo A
authors.initials: IA
authors.lastname: Hansen
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Attardo
authors.forename: Saurabh G
authors.initials: SG
authors.lastname: Roy
authors.forename: Alexander S
authors.initials: AS
authors.lastname: Raikhel
mesh_terms: D000330:Aedes / Q000196:embryology* / Q000201:enzymology*; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000494:pharmacology; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D029721:Drosophila Proteins; D004527:Egg Proteins / Q000235:genetics; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005216:Fat Body / Q000201:enzymology; D005260:Female; D008969:Molecular Sequence Data; D010053:Ovary / Q000201:enzymology; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger / Q000032:analysis; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases; D014819:Vitellogenins / Q000235:genetics
chemical_list: D000596:Amino Acids; D029721:Drosophila Proteins; D004527:Egg Proteins; D004791:Enzyme Inhibitors; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D019893:Ribosomal Protein S6 Kinases; D029701:Saccharomyces cerevisiae Proteins; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; D014819:Vitellogenins; C416303:target of rapamycin protein, Drosophila; C500749:target of rapamycin protein, S cerevisiae