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THE PROPROTEIN CONVERTASES OF Aedes aegypti: IMPLICATIONS DURING FLAVIVIRUS AND ALPHAVIRUS INFECTION
In 1741, a British fleet of around 124 ships attacked Cartagena. The purpose of the siege was to gain control of the Spanish port and eventually use it to invade inner colonial lands. The siege involved invasion by sea and land and was at first successful. There was one remaining obstacle to win the victory, the San Felipe de Barajas Castle. This attack resulted more difficult as it involved mobilization of British troops into the jungle, where soldiers were exposed to mosquitoes. As the battle progressed, the British army was forced to retreat as they had lost thousands of men, the majority from yellow fever virus, leading to a Spanish victory. This is just an example of how mosquitoes can influence the outcome of history. Even in our days, we see how the mosquitoes can affect the way we live and the tremor they can cause with outbreaks like Zika, yellow fever, chikungunya, or dengue viruses. As such, it is important to be prepared and develop strategies that would harm the tight mosquito-virus relationships. For that reason, understanding the life cycle of these viruses in the mosquito would provide targets for disease control. One of the major steps in the life cycle of the virus is the maturation process, which heavily relies on the host proteases. The objective of this dissertation was to identify the mosquito proteases that are necessary for the maturation of flaviviruses and alphaviruses. Given that multiple viral families utilize these proteases, disrupting their function would prove harmful for different viruses at once. In the mosquito, Aedes aegypti, there are three proprotein convertases, named furin1, furin2 and NC2. These proteases retain high similarity with the human and drosophila homologs and were initially hypothesized to be involved in the viral maturation process. Recombinant expression and enzymatic activity assays of these proteins showed that furin1 exhibited activity comparable to human furin but significantly higher than furin2, whereas NC2 was not active under the experimental conditions. Further, CRISPr knockouts in mosquito Aag2 cells revealed that furin1 but not furin2 is required for efficient maturation flaviviruses and alphaviruses, as reduced proteolytic cleavage is also reflected in reduced viral titer. Combined, these experiments suggest that furin1 has a role in the proteolytic cleavage of different families of arboviruses in mosquitoes and is associated with their maturation and infectivity. Attacking the maturation process of these viruses during the infection of the mosquito will change the history of vector-borne diseases control.