Salinity Responsiveness of Aquaporins in Osmoregulatory Organs of Larval Mosquito Aedes Aegypti
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Aedes aegypti mosquitoes harbour and transmit arboviral diseases such as chikungunya, dengue, yellow fever, and Zika. The aquatic larvae typically reside in freshwater environments that impose an osmotic challenge of water accumulation in their hemolymph across larval surfaces. Natural phenomena and anthropogenic activities salinize freshwater environments which larvae are able to exploit and successfully complete development in up to 30% seawater. Understanding water regulation under various osmoregulatory challenges is crucial to understanding this disease vectors physiology. Generally, water crosses cellular membranes through transmembrane proteins named aquaporins (AQPs) and A. aegypti possess six AQP homologues (AaAQP). This is the first comprehensive study examining the expression of AQPs in A. aegypti and their response to changes in environmental salinity within the osmoregulatory organs. An entomoglyceroporin, AaAQP5, is the most abundant AaAQP expressed in the osmoregulatory organs with the most AaAQPs expression found in the Malpighian tubules and anal papillae when compared to other osmoregulatory organs assessed in this study. Changes in transcript and protein abundance were observed in AaAQP1, AaAQP3, AaAQP4, AaAQP5, and AaAQP6 suggesting that the larvae modulate AaAQP expression to regulate water balance with changes to aquatic environmental salinity. Additionally, it was revealed that AaAQPs change their localization between the cytosol and the membrane in osmoregulatory organ epithelia in response to environmental salinity as a potential means of regulating membrane permeability through AaAQP insertion into the membrane. The results provide a basis of understanding for the role of AQPs in the osmoregulatory processes of A. aegypti larvae which, through further studies may identify new targets for the development of novel mosquito control agents for larvae prior to their emergence into the disease vector adult life stage.