title: The degradome and the evolution of Drosophila sex peptide as a ligand for the MIP receptor.
abstract: The male sex peptide (SP) of Drosophila melanogaster has wide ranging effects on females, including rejection of courting males, increased egg production, changes to the feeding habit, increased synthesis of antimicrobial peptides and elevated locomotor activity during day-time. The peptide activates receptors in sensory neurons of the female reproductive tract and can also traverse into the hemolymph and reach the central nervous system. The SP receptor involved in rejection and egg-laying responses has been shown to be identical to the receptor for the evolutionary conserved myoinhibitory peptides (MIPs) that function as neuropeptides in both males and females. Intriguingly, MIPs cannot substitute for SP when either expressed in the male accessory glands or injected into virgin females. MIPs are linear peptides with an amidated C-terminus which protects them from cleavage by carboxypeptidases, but leaves them exposed to potential attack from aminopeptidase and endopeptidase activities. In contrast, the SP region responsible for eliciting the post-mating response is cyclic and has several hydroxyproline residues N-terminal to the disulfide bridge which is expected to protect the biological activity of SP from peptidases of the male accessory gland and seminal fluid. We now present in vitro data showing that SP is metabolically stable, whereas MIPs are much more susceptible to degradation by peptidases of the male accessory gland and the hemolymph of virgin female D. melanogaster. SP has evolved relatively recently as a MIP receptor ligand that is particularly well adapted to surviving in the hostile degradome of the male accessory gland and seminal fluid.
authors.affiliation: School of Biology, University of Leeds, Leeds LS2 9JT, UK. Electronic address: r.e.isaac@leeds.ac.uk.
authors.forename: R Elwyn
authors.initials: RE
authors.lastname: Isaac
authors.affiliation: Department of Life Science, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea.
authors.forename: Young-Joon
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: The Food and Environmental Research Agency, Sand Hutton, York, YO41 1LZ, UK.
authors.forename: Neil
authors.initials: N
authors.lastname: Audsley
mesh_terms: D000818:Animals; D004330:Drosophila / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism; D005260:Female; D008297:Male; D010447:Peptide Hydrolases / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D012661:Semen / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D010455:Peptides; D010447:Peptide Hydrolases
keywords: Drosophila melanogaster; Male accessory glands; Myoinhibitory peptide; Peptidase; Seminal fluid; Sex peptide