DENV-Protease Cleavage of cGAS

Abstract

Dengue virus (DENV) is a single-stranded RNA virus that is transmitted via mosquitos in tropical and subtropical regions. DENV is a significant public health threat, causing severe infections in humans. The virus causes potentially life-threatening symptoms in some people and has a particularly interesting evasion method to avoid the host’s immune system. DENV targets a particular immune pathway called the cGAS-STING pathway to prevent or suppress type I interferon production, allowing it to persist in the host for a longer period. DENV protease NS2B3 is a critical component of the virus's replication complex and plays a crucial role in the viral lifecycle. The two components of this protease are NS2B and NS3. NS2B is a non-structural protein that acts as a cofactor for the NS3 protein, which is a serine protease. The NS2B protein helps to activate the NS3 protein by binding to it and creating a catalytic site for the protease activity. Together, NS2B and NS3 play a crucial role in the cleavage of the viral polyprotein into individual proteins that are necessary for viral replication. NS3, in addition to its role as a protease, also has helicase activity which is essential for the unwinding of viral RNA during replication. The NS3 protein is also involved in the formation of the viral replication complex and is important for the evasion of the host immune response. NS2B and NS3 are attractive targets for the development of antiviral drugs because of their essential role in the replication of flaviviruses. Previous research shows that human cGAS (hcGAS) is targeted for degradation by the NS2B3 protease complex of the virus. However, it remains unclear whether NS2B3 interacts with and cleaves mouse cGAS (mcGAS). In this experiment I purified mcGAS and conducted a cleavage assay to investigate the interaction between NS2B3 and mcGAS. I hypothesized that under ideal conditions for DENV that resemble a human’s bodily temperature, NS2B3 cleaves mcGAS in similar relative locations to those in hcGAS. Our results demonstrate that mcGAS is cleaved in a similar manner to hcGAS in the presence of NS2B3, suggesting that this mechanism of immune evasion is conserved between human and mouse hosts. These findings provide insights into the interaction between DENV and the host immune system and suggest that targeting this interaction could be a potential therapeutic strategy for DENV infections. Future studies should investigate the functional consequences of mcGAS cleavage and explore the potential of targeting this interaction for the development of novel antiviral therapies.