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Ovary ecdysteroidogenic hormone functions independently of the insulin receptor in the yellow fever mosquito,Aedes aegypti
Authors:Animesh Dhara  Jai-Hoon Eum  Anne Robertson  Monika Gulia-Nuss  Kevin J Vogel  Kevin D Clark  Rolf Graf  Mark R Brown  Michael R Strand
Institution:1. Department of Entomology, University of Georgia, Athens, GA 30602, USA;2. Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY 40536, USA;3. Department of Entomology, Purdue University, West Lafayette, IN 47907, USA;4. Pancreatitis Research Laboratory DL 34, Rämistrasse 100, Universitätsspital Zürich, 8091 Zürich, Switzerland;1. UMR 1272, UPMC-INRA, Physiologie de l’Insecte: Signalisation et Communication, Université Paris VI, Bâtiment A, 7 quai Saint Bernard, 75005 Paris, France;2. Université Paris-Sud, Service d’Enseignement de Biologie Animale, Bâtiment 332, 91405 Orsay, France;3. UMR 1272, UPMC-INRA, Physiologie de l’Insecte: Signalisation et Communication, INRA, Route de Saint-Cyr, 78026 Versailles, France;1. Department of Cell and Systems Biology, University of Toronto, Toronto, Canada;2. Department of Biology, Zoological Institute, KU Leuven, B-3000 Leuven, Belgium
Abstract:Most mosquito species must feed on the blood of a vertebrate host to produce eggs. In the yellow fever mosquito, Aedes aegypti, blood feeding triggers medial neurosecretory cells in the brain to release insulin-like peptides (ILPs) and ovary ecdysteroidogenic hormone (OEH). Theses hormones thereafter directly induce the ovaries to produce ecdysteroid hormone (ECD), which activates the synthesis of yolk proteins in the fat body for uptake by oocytes. ILP3 stimulates ECD production by binding to the mosquito insulin receptor (MIR). In contrast, little is known about the mode of action of OEH, which is a member of a neuropeptide family called neuroparsin. Here we report that OEH is the only neuroparsin family member present in the Ae. aegypti genome and that other mosquitoes also encode only one neuroparsin gene. Immunoblotting experiments suggested that the full-length form of the peptide, which we call long OEH (lOEH), is processed into short OEH (sOEH). The importance of processing, however, remained unclear because a recombinant form of lOEH (rlOEH) and synthetic sOEH exhibited very similar biological activity. A series of experiments indicated that neither rlOEH nor sOEH bound to ILP3 or the MIR. Signaling studies further showed that ILP3 activated the MIR but rlOEH did not, yet both neuropeptides activated Akt, which is a marker for insulin pathway signaling. Our results also indicated that activation of TOR signaling in the ovaries required co-stimulation by amino acids and either ILP3 or rlOEH. Overall, we conclude that OEH activates the insulin signaling pathway independently of the MIR, and that insulin and TOR signaling in the ovaries is coupled.
Keywords:Mosquito  Endocrine  Reproduction  Oogenesis
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