Conference 2021 Pre-Recorded Video
Anti-diuretic hormone, CAPA, inhibits V-type H+-ATPase in the Malpighian tubules of the yellow fever mosquito, Aedes aegypti
Authors and Affiliations
Farwa Sajadi1, Jean-Paul Paluzzi1
1. Department of Biology, York University, Toronto, Canada
Haematophagus insects, such as the female Aedes aegypti mosquito, face the challenge of excess ion and water intake after engorgement on a blood meal. To cope with this, adult female A. aegypti have a specialized excretory system that includes the Malpighian tubules (MTs), which are under rigorous control by several neuroendocrine factors to regulate transepithelial movement of ions/water. Produced in the CNS, the mosquito anti-diuretic hormone is a member of the CAPA peptide family, which share homology to the vertebrate neuromedin U peptide. CAPA peptides inhibit fluid secretion of MTs stimulated by select diuretic factors, 5HT and DH31 through the NOS/cGMP/PKG pathway. However, the anti-diuretic signalling mechanism and downstream cellular targets, such as ion channels and transporters, remain unclear.
The effect of endocrine factors and inhibitors on fluid secretion was measured using an in vitro bioassay, while ion-selective microelectrodes were used to measure pH levels. Activity assays were performed to measure VA and NKA activity in diuretic-stimulated tubules, while protein localization was conducted through immunohistochemistry.
MTs treated with bafilomycin, a proton pump inhibitor, was found to inhibit fluid secretion stimulated by 5-HT and DH31, while having no inhibitory action on CRF-stimulated MTs. Alkalization of the secreted fluid in response to CAPA, in DH31- and 5HT-stimuated MTs, suggests inhibition of the apical proton pump, which may lead to constrained entry of cations across the apical membrane of the MTs. Adult female MTs treated with DH31 resulted in an increase of both NKA and VA activity compared saline controls. As expected, MTs incubated with both DH31 and AedaeCAPA-1 had a lower NKA and VA activity resulting in activity levels comparable to saline control levels. The results thus far could suggest a novel mechanism for CAPA inhibition, blocking the VA to hinder fluid secretion.
A. aegypti mosquitoes are vectors of a variety of pathogens leading to diseases such as the Zika virus. Given the central importance of the MTs in insect biology, these insights will be useful considering the need to develop novel strategies which more efficiently reduce the burden of insect disease vectors.