The female mosquito, Aedes aegypti, is a day-biting mosquito, taking a single or multiple blood meals, to obtain the necessary vitamins and nutrients for her egg development¹. However, upon ingesting a large blood meal, adult females face the challenge of haemolymph (blood) ion dilution, as they take on a significant water load. To cope with this, insects like A. aegypti utilize a specialized excretory system, comprised of the Malpighian ‘renal’ tubules (MTs), to counter the disturbances to their haemolymph balance, whereby diuretic hormones are released to act on the MTs to drive secretion of large amounts of urine to maintain osmotic balance².

The MTs are under rigorous control by neuroendocrine factors², and our research focuses on examining the complex cross-talk between the hormonal regulators of A. aegypti MTs. Multiple studies have examined the effects of diuretic factors on A. aegypti mosquitoes, with only limited attention on anti-diuretic factors. Our research focuses on investigating the physiological roles of an insect neuropeptide, CAPA, and its contribution to mosquito osmoregulation via its direct actions on the MTs.

Our lab team recently published a study in Scientific Reports where we established an anti-diuretic hormone system in the adult mosquito A. aegypti³. This work demonstrated the release of the CAPA hormone by the abdominal segmental neurohaemal organs to target their receptor, exclusively expressed within the principal cells of the MTs. Through RNA interference techniques, we were able to successfully knockdown the CAPA receptor, and confirm its anti-diuretic activity against a subset of diuretic hormones through in vitro bioassays.

Although CAPA peptides have been shown to demonstrate species-specific and dose-dependent effects, displaying both diuretic^4–6 and anti-diuretic activity^4,7, we have shown a novel anti-diuretic role for the CAPA peptide in the Aedes mosquito. Our research indicates that CAPA selectively inhibits (serotonin) 5HT- and (calcitonin-related diuretic hormone) DH₃₁-stimulated secretion⁸, previously published in the Journal of Experimental Biology, through the cGMP/NOS/PKG pathway³. Currently, we are in the process of investigating the precise mechanism of action on ion channels and transporters involved in the signaling pathway of CAPA, which remains unclear to date.

Investigating hormonal regulation of anti-diuresis is important in insects, since this is the standard physiological state, interrupted only briefly during post-prandial diuresis in insects engorging on plant nectar or vertebrate blood. The female Aedes aegypti mosquito is recognized as an important disease vector, responsible for transmitting various arboviruses including dengue fever, yellow fever and the Zika virus. Therefore, further understanding this complex regulation can allow for development of novel pest management strategies that can interfere with hormones regulating hydromineral balance, and thus lessen the burden of these insects.

This blog post was written by one of our winners, Farwa Sajadi, of the Graduate Student Nomination Contest 2021. She is currently pursuing her PhD at York University.

Related Research

Do you work in this field of research? If so, you may be interested in viewing our other reagents that might be related to the Aedes aegypti mosquito. Some of the reagents include:

• Anti-Zika Virus
• Photoactivatable Serotonin (BHQ-O-5HT)
• Anti-Dengue-1,2,3 Virus Non-Structural Protein 1 (NS1) [2G1] Antibody

References:

1.          Clements, A. N. The biology of mosquitoes. Volume 1. Development, nutrition and reproduction | Mosquito Taxonomic Inventory. (Chapman & Hall, 1992).

2.          Beyenbach, K. W. Transport mechanisms of diuresis in Malpighian tubules of insects. J. Exp. Biol. 206, 3845–3856 (2003).

3.          Sajadi, F. et al. CAPA neuropeptides and their receptor form an anti-diuretic hormone signaling system in the human disease vector, Aedes aegypti. Sci. Rep. 10, (2020).

4.          Ionescu, A. & Donini, A. AedesCAPA-PVK-1 displays diuretic and dose dependent antidiuretic potential in the larval mosquito Aedes aegypti (Liverpool). J. Insect Physiol. 58, 1299–1306 (2012).

5.          Terhzaz, S. et al. Mechanism and function of Drosophila capa GPCR: A desiccation stress-responsive receptor with functional homology to human neuromedinU receptor. (2012). doi:10.1371/journal.pone.0029897

6.          Pollock, V. P. et al. Conservation of capa peptide-induced nitric oxide signalling in Diptera. J. Exp. Biol. 207, 4135–4145 (2004).

7.          Paluzzi, J. P., Naikkhwah, W. & O’Donnell, M. J. Natriuresis and diuretic hormone synergism in R. prolixus upper Malpighian tubules is inhibited by the anti-diuretic hormone, RhoprCAPA-α2. J. Insect Physiol. 58, 534–542 (2012).

8.          Sajadi, F., Curcuruto, C., Al Dhaheri, A. & Paluzzi, J.-P. V. Anti-diuretic action of a

CAPA neuropeptide against a subset of diuretic hormones in the disease vector, Aedes aegypti. J. Exp. Biol (2018). doi: 10.1242/jeb.177089