Stimulation of glycogenolysis by three locust adipokinetic hormones involves Gs and cAMP.
Insect adipokinetic hormones (AKHs) have been shown to mobilize fat body carbohydrate by glycogen phosphorylase activation. In this study, the signal transduction pathways of AKH-I, -II and -III from the migratory locust are further elucidated. We show that the AKHs enhance fat body cAMP levels in vitro. For all hormones, maximal levels are reached after 1 min and correspond to a 200% increase compared to resting levels. Although cAMP levels induced by massive doses of AKH-I, -II and -III are equal, AKH-III is the most potent when applied in a physiological dose. This difference in potency also applies to glycogen phosphorylase activation. Cholera toxin (CTX) likewise ennhaces cAMP levels and phosphorylase activity, however pertussis toxin (PTX) has no effect. Increases induced by CTX and AKH are not additive, suggesting that they share the same pathway. Phosphorylase activation by the AKHs is strongly attenuated by guanosine-5'-O-(2-thiodiphosphate) (GDP beta S). These results demonstrate a role for cAMP in AKH signal transduction and indicate that the AKH receptor(s) are coupled to cAMP formation and glycogen phosphorylase activation via the stimulatory guanine nucleotide-binding protein (Gs).
Vroemen
S F
SF
Department of Experimental Zoology, Utrecht University, The Netherlands.
Van Marrewijk
W J
WJ
Van der Horst
D J
DJ
D000818:Animals; D050260:Carbohydrate Metabolism; D002463:Cell Membrane Permeability; D002772:Cholera Toxin / Q000494:pharmacology; D000242:Cyclic AMP / Q000096:biosynthesis / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005216:Fat Body / Q000187:drug effects / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism*; D006110:Grasshoppers / Q000187:drug effects / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D007301:Insect Hormones / Q000008:administration & dosage / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D009842:Oligopeptides / Q000008:administration & dosage / Q000494:pharmacology*; D037342:Pertussis Toxin; D006005:Phosphorylases / Q000378:metabolism; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D015398:Signal Transduction; D013873:Thionucleotides / Q000494:pharmacology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D007301:Insect Hormones; D009842:Oligopeptides; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; C044833:adipokinetic hormone; D006153:Guanosine Diphosphate; C023427:guanosine 5'-O-(2-thiodiphosphate); D006003:Glycogen; D002772:Cholera Toxin; D000242:Cyclic AMP; D006005:Phosphorylases; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D011761:Pyrrolidonecarboxylic Acid