Submitted to: Molecular and Cellular Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2008
Publication Date: 2/21/2009
Citation: Wang, J., Stanford, J.R., Willis, D.K., Orth, A., Goodman, W.G. 2009. Juvenile Hormone Regulates the Expression of Drosophila Epac– a Guanine Nucleotide Exchange Factor for Rap1 Small GTPase. Molecular and Cellular Endocrinology. 305(1-2):30-37. Interpretive Summary: Insect juvenile hormones play important roles in the development of animal and plant insect pests. Several commercial insecticides such as methoprene are chemically synthesized juvenile hormone derivatives that aid in the control of insect pests in both animals and plants. This work analyzes the regulation of a genetic regulatory pathway that is induced by juvenile hormone. The gene Epac is signficantly induced by juvenile hormone and related compounds, but not by related substances that do not have hormone activity. This is the first report of a juvenile hormone effect on the Epac gene. Analysis of this gene and the regulatory cascade that it controls may provide novel targets for future insecticide action of use to both plant and animal agriculture.
Technical Abstract: The juvenile hormones (JH) are a key group of insect hormones involved in regulating larval development and adult reproductive processes. Although well-studied from the physiological standpoint, the molecular actions of JH remain unclear. Using cDNA microchip array technology, we previously identified genes in Drosophila S2 cells whose expression is regulated by purified JHIII. One gene, Epac (exchange protein directly activated by cyclic AMP, a guanine nucleotide exchange factor for Rap1 small GTPase), was significantly upregulated (> 3-fold) in JHIII-treated cells as determined by real-time reverse transcription polymerase chain reaction (RT-PCR). Epac transcripts displayed a rapid and dose-dependent increase in the presence of JH homologs and agonists, but not in the presence of JH acid, a metabolite of JH degradation. The molting hormone, 20-hydroxyecdysone had no affect on the JH-driven response of Epac. Furthermore, JH has no effect on the mRNA expression level of Epac in the human cell line, HEK-293. The increase in Epac transcript accumulation is most likely due to increased transcription since primers that span an Epac intron-exon boundary detected elevated levels of un-processed mRNA in JH treated S2 cells. We examined the effect of the JH analog methoprene on the elevation of Epac mRNA in vivo using third instar Drosophila larvae. Feeding larvae this analog elevated Epac transcript a statistically significant (P = 0.05) 50%. Taken together, our data strongly implicates Epac as part of the JH regulatory cascade required for insect development.