Structure‐guided insights on the role of NS1 in flavivirus infection

Abstract

We highlight the various domains of the flavivirus virulence factor NS1 and speculate on potential implications of the NS1 3D structure in understanding its role in flavivirus pathogenesis. Flavivirus non-structural protein 1 (NS1) is a virulence factor with dual functions in genome replication and immune evasion. Crystal structures of NS1, combined with reconstructions from electron microscopy (EM), provide insight into the architecture of dimeric NS1 on cell membranes and the assembly of a secreted hexameric NS1-lipid complex found in patient sera. Three structural domains of NS1 likely have distinct roles in membrane association, replication complex assembly, and immune system avoidance. A conserved hydrophobic inner face is sequestered either on the membrane or in the interior of the secreted hexamer and contains regions implicated in viral replication. The exposed variable outer face is presented to cellular and secreted components of the immune system in infected patients and contains candidate regions for immune system modulation. We anticipate that knowledge of the distinct NS1 domains and assembly will lead to advances in elucidating virus-host interactions mediated through NS1 and in dissecting the role of NS1 in viral genome replication.

Dengue Virus NS1 Protein Modulates Cellular Energy Metabolism by Increasing Glyceraldehyde-3-Phosphate Dehydrogenase Activity

“…This finding is interesting because the ␤-roll domain is responsible for the NS1 interaction with the ER membrane (21). Mutations in this region impair virus replication, either by affecting the NS1 interaction with NS4b or by preventing NS1 retention in the ER lumen (20)(21)(22). Indeed, mutation of the Asn10, Lys11, Gly161, and Val162 residues, located at the ␤-roll domain and connector subdomain, decreased the tendency for the interaction to occur without abolishing it.…”

“…Mutations at residues Asn10 and Lys11 (located at the NS1 ␤-roll domain) and in the region of Gly159-Phe-Gly-Val162 (connector subdomain) were previously found to be associated with defective flavivirus replication (20)(21)(22). To evaluate the importance of the ␤-roll domain for complex formation between NS1 and GAPDH, a three-dimensional model of dimeric NS1 containing the mutations Asn10Ala, Lys11Ala, Gly161Asp, and Val162Asp (NS1 mut ) was constructed as described above, and NS1 mut was used as the system's receptor and GAPDH (O chain) was used as the ligand.…”

“…Similarly, mutations in the NS1 sequence, specifically, in the ␤-roll domain and connector subdomain, impair plaque formation and RNA accumulation, resulting in decreased virus yield (19)(20)(21)(22). Nevertheless, complementation with exogenous NS1 allows RNA replication and virus particle production to be recovered in a truncated West Nile virus (WNV) lacking NS1 (23), indicating its importance in the replication process.…”

The C Terminus of the Core β-Ladder Domain in Japanese Encephalitis Virus Nonstructural Protein 1 Is Flexible for Accommodation of Heterologous Epitope Fusion

“…The surface exposure of flavivirus multimeric NS1 proteins released from infected cells determines its immunogenicity to the host, especially in terms of eliciting specific antibody responses (5,6). To examine whether the inserted EV71 epitope in the NS1 C terminus of recombinant JEV is correctly exposed outward, we used a homology-modeling algorithm (Accelrys Discovery Studio 3.1; Accelrys Inc.) to analyze the multimeric structures of NS1 in ribbons or surface diagrams among wild-type JEV NS1 and NS1-EV71 (29), and using recently reported crystal structures of dimeric and hexameric WNV NS1 (PDB 406C and 406D) as references (5), we observed a noticeable structure of the core ␤-ladder domain in dimers of JEV NS1 (Fig.…”

The mechanism by which P250L mutation impairs flavivirus-NS1 dimerization: an investigation based on molecular dynamics simulations

“…It is postulated that the β -roll domain would function as a "hydrophobic protrusion" to attach NS1 to lipid membranes (Akey et al 2014). As a direct consequence, this would orientate the other face (the "spaghetti loop" region) towards the extracellular space, exposing this area for immune recognition (Akey et al 2015). We suggest that the inhibition of NS1 dimerization would affect its membrane-binding capacity due to the disruption of the "hydrophobic protrusion" composed by monomer-complementary regions of the β-roll domains.…”