title: Sulfakinin is an important regulator of digestive processes in the migratory locust, Locusta migratoria.
abstract: Sulfakinin (SK) is a sulfated insect neuropeptide that is best known for its function as a satiety factor. It displays structural and functional similarities with the vertebrate peptides gastrin and cholecystokinin. Peptidomic studies in multiple insects, crustaceans and arachnids have revealed the widespread occurrence of SK in the arthropod phylum. Multiple studies in hemi- and holometabolous insects revealed the pleiotropic nature of this neuropeptide: in addition to its activity as a satiety factor, SK was also reported to affect muscle contraction, digestive enzyme release, odor preference, aggression and metabolism. However, the main site of action seems to be the digestive system of insects. In this study, we have investigated whether SK can intervene in the control of nutrient uptake and digestion in the migratory locust (Locusta migratoria). We provide evidence that sulfakinin reduces food uptake in this species. Furthermore, we discovered that SK has very pronounced effects on the main digestive enzyme secreting parts of the locust gut. It effectively reduced digestive enzyme secretion from both the midgut and gastric caeca. SK injection also elicited a reduction in absorbance and proteolytic activity of the gastric caeca contents. The characteristic sulfation of the tyrosine residue is crucial for the observed effects on digestive enzyme secretion. In an attempt to provide potential leads for the development of peptidomimetic compounds based on SK, we also tested two mimetic analogs of the natural peptide ligand in the digestive enzyme secretion assay. These analogs were able to mimic the effect of the natural SK, but their effects were milder. The results of this study provide new insights into the action of SK on the digestive system in (hemimetabolous) insects.
authors.affiliation: Molecular Developmental Physiology and Signal Transduction, Department of Biology, KU Leuven, Naamsestraat 59, Leuven, Vlaams-Brabant, Belgium. Electronic address: Sven.Zels@bio.kuleuven.be.
authors.forename: Sven
authors.initials: S
authors.lastname: Zels
authors.affiliation: Molecular Developmental Physiology and Signal Transduction, Department of Biology, KU Leuven, Naamsestraat 59, Leuven, Vlaams-Brabant, Belgium. Electronic address: Senne.Dillen@bio.kuleuven.be.
authors.forename: Senne
authors.initials: S
authors.lastname: Dillen
authors.affiliation: Molecular Developmental Physiology and Signal Transduction, Department of Biology, KU Leuven, Naamsestraat 59, Leuven, Vlaams-Brabant, Belgium. Electronic address: Katleen.Crabbe@bio.kuleuven.be.
authors.forename: Katleen
authors.initials: K
authors.lastname: Crabbé
authors.affiliation: Molecular Developmental Physiology and Signal Transduction, Department of Biology, KU Leuven, Naamsestraat 59, Leuven, Vlaams-Brabant, Belgium. Electronic address: Jornt.Spit@bio.kuleuven.be.
authors.forename: Jornt
authors.initials: J
authors.lastname: Spit
authors.affiliation: Areawide Pest Management Research Unit, Southern Plains Agricultural Research Center, USDA, College Station, TX, USA. Electronic address: nachman@tamu.edu.
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Nachman
authors.affiliation: Molecular Developmental Physiology and Signal Transduction, Department of Biology, KU Leuven, Naamsestraat 59, Leuven, Vlaams-Brabant, Belgium. Electronic address: Jozef.Vandenbroeck@bio.kuleuven.be.
authors.forename: Jozef
authors.initials: J
authors.lastname: Vanden Broeck
mesh_terms: D000818:Animals; D004064:Digestive System / Q000187:drug effects / Q000201:enzymology; D004435:Eating / Q000187:drug effects; D048188:Locusta migratoria / Q000187:drug effects* / Q000502:physiology; D009479:Neuropeptides / Q000378:metabolism / Q000494:pharmacology*; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology; D057786:Peptidomimetics / Q000138:chemical synthesis / Q000494:pharmacology
chemical_list: D009479:Neuropeptides; D009842:Oligopeptides; D057786:Peptidomimetics
keywords: Cholecystokinin; Digestion; Food intake; Insect gut; Peptide; Satiety