Expression and functional characterization of aquaporins in yellow fever mosquito, Aedes aegypti

Female mosquitoes require the uptake of blood for egg production and as a result, they transmit disease pathogens to humans. It is essential for mosquitoes to possess an efficient excretion system to shed excess water and sodium ions and retain nutrients from the blood. After a blood meal, females excrete large amounts of urine through their excretory organs, the Malpighian tubules (MT). Aquaporins (AQPs) are a family of membrane transporters that regulate the flow of water, glycerol and other small molecules across cellular membranes in both prokaryotic and eukaryotic cells. Previously, we surveyed genome databases and identified six putative AQPs in the genome of Ae. aegypti. In this study, we have confirmed that the AQPs expressed in the MTs function as water channels and mediate transcellular water transport in adult female Ae. aegypti. We have expressed Ae. aegypti AQPs in Xenopus laevis oocytes which has resulted in significant increase in water permeability of their cell membranes and subsequent swelling demonstrating that these proteins are indeed water channels. Non-radio labeled solute uptake assays revealed that AQP 4 is a multifunctional aquaglyceroporin and has significant transport capabilities for a wide variety of solutes including glycerol, urea and trehalose. These studies provide a better understanding into the role of AQPs during water homeostasis and humidity adaptation in Ae. aegypti.