title: Structure-activity relationship of adipokinetic hormone analogs in the striped hawk moth, Hippotion eson.
abstract: We showed previously that the sphingid moth Hippotion eson synthesizes the highest number of adipokinetic hormones (AKHs) ever recorded, viz. five, in its corpus cardiacum: two octa-, two nona- and one decapeptide. Further, the endogenous decapeptide (Manse-AKH-II) and the other four AKHs are all active in lipid mobilization, whereas a non-lepidopteran decapeptide (Lacsp-AKH, five amino acid substitutions compared with Manse-AKH-II), was inactive in H. eson. We tested the decapeptide, Lacol-AKH, from a noctuid moth for the first time in a bioassay and it shows a maximal AKH effect in H. eson. Lacol-AKH differs from Manse-AKH-II in three places and from Lacsp-AKH in four places. We, thus, used Lacol-AKH as a lead peptide on which a series of AKH analogs are based to represent: (a) single amino acid replacements (according to the substitutions in Lacsp-AKH), (b) shorter chain lengths, (c) modified termini, and (d) a replacement of Trp in position 8. These analogs, as well as a few naturally occurring AKHs from other lepidopterans were tested in in vivo adipokinetic assays to gain insight into the ligand-receptor interaction in H. eson. Our results show that the second and third amino acids are important for biological activity in the sphingid moth. Analogs with an N-[acetylated]Glu(1) (instead of a pyroGlu), or a free C-terminus, or Ala(8) were not active in the bioassays, while shortened Lacol-AKH analogs and the undecapeptide, non-amidated Vanca-AKH showed very reduced activity (below 25%). This information is important for the consideration of peptide mimetics to combat specific lepidopteran pest insects.
authors: Department of Biological Sciences, University of Cape Town, Rondebosch, South Africa. Electronic address: heather.marco@uct.ac.za.
authors: Heather G
authors: HG
authors: Marco
authors: Department of Biological Sciences, University of Cape Town, Rondebosch, South Africa.
authors: Gerd
authors: G
authors: Gäde
mesh_terms: D054392:Adipokines / Q000737:chemistry / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D005260:Female; D057927:Hydrophobic and Hydrophilic Interactions; D007301:Insect Hormones / Q000737:chemistry / Q000502:physiology*; D019476:Insect Proteins / Q000737:chemistry / Q000502:physiology*; D050356:Lipid Metabolism; D008297:Male; D009036:Moths / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D054392:Adipokines; D007301:Insect Hormones; D019476:Insect Proteins
keywords: Adipokinetic hormone; Energy mobilization; Hippotion eson; Sphingid moth; Structure–activity assays