The Distribution and Physiological Effects of the Myoinhibiting Peptides in the Kissing Bug, Rhodnius Prolixus

Angela B Lange,Ian Orchard,Jozef Vanden Broeck,Hans Peter Vandersmissen,Uzma Alim,Akira Mizoguchi

doi:10.3389/fnins.2012.00098

Abstract

The myoinhibiting peptides (MIPs), also designated as allatostatin-Bs or prothoracicostatic peptides in some insects, are neuropeptides that are characterized by two tryptophan (W) residues at the C-terminal, denoted as the W(X6)Wamide motif. They are believed to be the ancestral ligands for the Drosophila sex peptide (SP) receptor. Physiological functions of MIPs include the inhibition of contraction of insect visceral muscles, in addition to allatostatic and prothoracicostatic activities. The MIP precursor in Rhodnius prolixus encodes MIPs that have an unusual W(X7)Wamide motif. In the present study, MIP-like immunoreactivity was detected within neurons in the central nervous system and within the innervation to the salivary glands, hindgut, and female and male reproductive systems of adult R. prolixus. The effects of peptides with the unusual W(X7)Wamide motif (Rhopr-MIP-4) and with the typical W(X6)Wamide motif (Rhopr-MIP-7) were tested for physiological activity on R. prolixus hindgut contractions. Both peptides reduce the frequency and amplitude of hindgut contractions in a dose-dependent manner. In addition, both peptides activate the Drosophila SP receptor. The MIP/SP receptors are therefore activated by peptides with the unusual W(X7)Wamide motif.

Highlights

Various insect neuropeptide families are myoinhibitory when tested against contractions of visceral muscle, but might have other biological functions
IMMUNOHISTOCHEMISTRY Like all antibodies used in immunohistochemistry, the MIPantibody could potentially cross-react with antigens other than the specific one it was generated against, and the term myoinhibiting peptides (MIPs)-like immunoreactivity
The number of MIP-like immunoreactive neurons was highest in the brain and mesothoracic ganglion mass (MTGM, ∼300), relative to the sub-esophageal ganglion (SOG) and prothoracic ganglion (PRO)

Summary

Introduction

Various insect neuropeptide families are myoinhibitory when tested against contractions of visceral muscle, but might have other biological functions (see Nässel and Winther, 2010). This peptide (AWQDLNAGWamide) was found to inhibit spontaneous contractions of locust hindgut and oviduct, and processes immunoreactive for Lom-MIP were subsequently found to be associated with both of these tissues (Schoofs et al, 1991, 1996) Additional members of this family with the C-terminal consensus sequence W(X6)Wamide, and some resemblance to vertebrate galanin, have since been identified in a number of insect species, including Manduca sexta, Bombyx mori, Periplaneta americana, Blattella germanica, Drosophila melanogaster, Gryllus bimaculatus, Carausius morosus, and Tribolium castaneum (Blackburn et al, 1995, 2001; Lorenz et al, 1995, 2000; Hua et al, 1999; Predel et al, 2001; Williamson et al, 2001; Baggerman et al, 2002; Aguilar et al, 2006; Li et al, 2008), as well as in crustacean and molluscan species (Moroz et al, 2006; Fu et al, 2007). MIPs appear to play a role in the abdominal circuits associated with ecdysis behavior in M. sexta and D. melanogaster (Davis et al, 2003; Kim et al, 2006a,b; Santos et al, 2007), and in Leucophaea maderae in multiple brain circuits, including the circadian system (Schulze et al, 2012)

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