Haemolymph levels of Schistocerca gregaria ion transport peptide and ion transport‐like peptide

Abstract

Titres of ion transport peptide (ITP) and ion transport-like peptide (ITP-L) in the haemolymph of the desert locust Schistocerca gregaria Forska˚l are investigated using a combination of enzyme-linked immunosorbent assay and reversed-phase high-performance liquid chromatography (HPLC). The estimated circulating levels of these two peptides are used to investigate their putative physiological roles. Haemolymph levels of ITP-L are significantly higher in fed and exercise-stressed locusts than in starved insects, suggesting a role for ITP-L in postfeeding osmoregulation and metabolism associated with stress. The higher titres of ITP-L in the final nymphal stadium could be related to increased levels of ecdysteroids over this same period. In addition detection of ITP-L in the brain and corpus cardiacum of the locust demonstrates for the first time that the ITP-L is expressed in these tissues. Immunoreactivity to antibodies raised against ITP is significantly higher in fed locusts compared with starved insects. However, >95% of this immunoreactivity elutes later than synthetic ITP when separated by HPLC. The results suggest that this more hydrophobic immunoreactivity is neither native ITP nor a metabolic breakdown product of ITP. Haemolymph levels of immunoreactivity to ITP during the last nymphal stadium are similar to ITP-L but, unlike ITP-L, there is no measured increase in immunoreactivity to ITP due to exercise stress.

Neuropeptide signaling sequences identified by pyrosequencing of the American dog tick synganglion transcriptome during blood feeding and reproduction

“…ITP in Schistocerca gregaria has been shown to control ion and fluid transport across the ileum in vitro (Audsley et al, 1992). Audsley et al (2006) found that ITP-like peptide in S. gregaria was upregulated during feeding. Meredith et al (1996) had previously shown the presence of an active ITP in S. gregaria (Q26491) as well as a closely related protein (Q26492) named ITP long form (ITP-L), also referred to as ion-transport peptide-like, which was not active and contained an extended carboxy terminus.…”

Insect ion transport peptides are derived from alternatively spliced genes and differentially expressed in the central and peripheral nervous system

“…After Dircksen et al, with permission (Dircksen et al, 2008). compared with the already mentioned feeding-related changes in ITP and ITPL titres were only observed about 5 to 7 days after ecdysis from the fourth to the fifth larval stages of S. gregaria (Audsley et al, 2006). Drexler and colleageus (Drexler et al, 2007) set out to measure CHH immunoreactivity and presumed ManseITP-like material (1) densitometrically in immunostained preparations of TN-PVOs and (2) in haemolymph by a noncompetitive ELISA (0.25-8 nmol l -1 range) before, during and after larval ecdysis from L4 to L5 stages of M. sexta.…”

“…Can the derived concepts be confirmed by in vivo studies, and are these the only physiological actions of both peptides? As a first step towards answering these questions, Audsley and colleagues (Audsley et al, 2006) undertook an important study to measure and identify the proposed circulating peptides SchgrITP and SchgrITPL in the CC and the haemolymph of fed (0.5-8 min and directly bled thereafter) and starved S. gregaria. The authors used enzyme-linked immunosorbant assays (ELISAs) with hapten antisera specifically discriminating SchgrITP (with the above-mentioned C1-antiserum) and SchgrITPL [with antisera raised against the SchgrITPL65-79 fragment; both antisera produced by Ring and colleagues (Ring et al, 1998)].…”

“…The latter example shows how important it is to perform 'postgenomic verification' of mRNAs (especially of their 5Ј-and 3Ј-ends) by cDNA cloning and of the deduced peptides by biochemical analysis. In fact, the definite occurrence and biochemical identity of ITP and ITPL peptides has thus far only been proven in the cases of the desert locust and the fruit fly ITPs (Audsley et al, 1992;Audsley et al, 2006;Dircksen et al, 2008 …”

Functions of ion transport peptide and ion transport peptide-like in the red flour beetle Tribolium castaneum

“…Ion transport peptide (ITP) in locusts (Schistocerca gregaria and Locusta migratoria) was identified based on its antidiuretic activity in the ileum (Audsley et al, 1992(Audsley et al, , 2006. ITP, released from the endocrine organs known as the corpora cardiaca (CC), stimulates the ileum to transport Cl À ion from lumen to hemolymph, thus forming an electrochemical gradient driving water resorption.…”