Novel Interactions Between Dengue Virus NS5 and Host Proteins Modulate Cellular Antiviral Responses

FEDERICO A. DE MAIO; RICARDO RAJSBAUM; MARÍA MORA GONZÁLEZ LÓPEZ LEDESMA; NESTOR GABRIEL IGLESIAS; ANDREA V. GAMARNIK; GUADALUPE SOLEDAD COSTA NAVARRO; PRIYA SAHA

Killarney

Simposio; Positive-Strand RNA Viruses; 2019

Keystone Symposia

Dengue virus (DENV) is currently one of the most important human viral pathogens transmitted by insects. DENV belongs to the Flaviviridae family, together with a large number of human pathogens that cause fever and encephalitis, such as Zika, Yellow fever, West Nile and Japanese encephalitis viruses. Flavivirus NS5 proteins play multiple functions during infection, enabling viral RNA synthesis and counteracting host antiviral responses. To investigate the interaction of NS5 with cellular components, we performed proteomic studies using NS5 tagged infectious DENV. We identified 53 host proteins that bind or form complexes with NS5 during viral infection and found that a number of these host proteins had antiviral activities. As a proof of concept, we detected STAT2, a known antiviral factor that binds to NS5 and is degraded during infection (Ashour et al. J Virol 2009). Furthermore, we showed that NS5 interaction with components of the host spliceosome machinery, in particular of the U5 snRNP particle, changes mRNA isoform abundance of known antiviral factors (De Maio et al. PLOS Pat 2016).To elucidate the mechanism of action of novel NS5 binders, we investigated the fate of host proteins that inhibit viral replication. Interestingly, the level of one of these proteins, ERC1, was significantly reduced in the course of DENV2 infection and protein degradation was found to be proteasome dependent. Expression of NS5 alone, in the absence of other viral proteins, was sufficient for ERC1 degradation. In addition, studies with the four DENV serotypes indicated that all but DENV4 NS5 efficiently degraded the host protein. Based on these findings, chimeric DENV2 NS5 proteins, containing defined residues of DENV4 NS5, unveiled amino acids involved in ERC1 interaction and degradation. These studies highlight the relevance of ERC1 as an antiviral factor and provide relevant information for dissecting its function during DENV infection.