Dengue Virus

DENV is a member of the Flaviviridae family and is grouped within the flavivirus genus together with other pathogenic viruses including West Nile virus (WNV), Japanese encephalitis virus (JEV), tick-borne encephalitis virus (TBEV) and yellow fever virus (YFV) [3]. The viral genome consists of a positive-sense RNA of ~11kb. This RNA encodes 3 structural proteins (C, prM and E) that form the components of the virion, and 7 non-structural proteins (NS1, NS2A/B, NS3, NS4A/B, NS5) involved in viral RNA replication. 

Genome polyprotein (P17763 )

Capsid protein C:

Plays a role in virus budding by binding to the cell membrane and gathering the viral RNA into a nucleocapsid that forms the core of a mature virus particle (PubMed:11893341).

During virus entry, may induce genome penetration into the host cytoplasm after hemifusion induced by the surface proteins. Can migrate to the cell nucleus where it modulates host functions (PubMed:18420804, PubMed:21909430).

Overcomes the anti-viral effects of host EXOC1 by sequestering and degrading the latter through the proteasome degradation pathway (PubMed:23522008).

Capsid protein C:

Inhibits RNA silencing by interfering with host Dicer.

Peptide pr:

Prevents premature fusion activity of envelope proteins in trans-Golgi by binding to envelope protein E at pH6.0. After virion release in extracellular space, gets dissociated from E dimers.

Protein prM:

Acts as a chaperone for envelope protein E during intracellular virion assembly by masking and inactivating envelope protein E fusion peptide. prM is the only viral peptide matured by host furin in the trans-Golgi network probably to avoid catastrophic activation of the viral fusion activity in acidic Golgi compartment prior to virion release (PubMed:9971841).

prM-E cleavage is inefficient, and many virions are only partially matured. These uncleaved prM would play a role in immune evasion (PubMed:21388812).

Small envelope protein M:

May play a role in virus budding (PubMed:25326389).

Exerts cytotoxic effects by activating a mitochondrial apoptotic pathway through M extodomain (PubMed:13679613).

May display a viroporin activity (PubMed:16007501).

Envelope protein E:

Binds to host cell surface receptor and mediates fusion between viral and cellular membranes. Envelope protein is synthesized in the endoplasmic reticulum in the form of heterodimer with protein prM. They play a role in virion budding in the ER, and the newly formed immature particle is covered with 60 spikes composed of heterodimer between precursor prM and envelope protein E. The virion is transported to the Golgi apparatus where the low pH causes dissociation of PrM-E heterodimers and formation of E homodimers (PubMed:18369148).

prM-E cleavage is ineficient, and many virions are only partially matured. These uncleaved prM would play a role in immune evasion (PubMed:11893341).

Non-structural protein 1:

Involved in immune evasion, pathogenesis and viral replication. Once cleaved off the polyprotein, is targeted to three destinations: the viral replication cycle, the plasma membrane and the extracellular compartment. Essential for viral replication. Required for formation of the replication complex and recruitment of other non-structural proteins to the ER-derived membrane structures. Excreted as a hexameric lipoparticle that plays a role against host immune response. Antagonizing the complement function. Binds to the host macrophages and dendritic cells. Inhibits signal transduction originating from Toll-like receptor 3 (TLR3).

Disrupts the host endothelial glycocalyx layer of host pulmonary microvascular endothelial cells, inducing degradation of sialic acid and shedding of heparan sulfate proteoglycans. NS1 induces expression of sialidases, heparanase, and activates cathepsin L, which activates heparanase via enzymatic cleavage. These effects are probably linked to the endothelial hyperpermeability observed in severe dengue disease.

Non-structural protein 2A:

Component of the viral RNA replication complex that functions in virion assembly and antagonizes the host immune response.

Serine protease subunit NS2B:

Required cofactor for the serine protease function of NS3. May have membrane-destabilizing activity and form viroporins (PubMed:26728778).

Serine protease NS3:

Displays three enzymatic activities: serine protease, NTPase and RNA helicase. NS3 serine protease, in association with NS2B, performs its autocleavage and cleaves the polyprotein at dibasic sites in the cytoplasm: C-prM, NS2A-NS2B, NS2B-NS3, NS3-NS4A, NS4A-2K and NS4B-NS5. NS3 RNA helicase binds RNA and unwinds dsRNA in the 3' to 5' direction.

Non-structural protein 4A:

Regulates the ATPase activity of the NS3 helicase activity. NS4A allows NS3 helicase to conserve energy during unwinding. Plays a role in the inhibition of the host innate immune response. Interacts with host MAVS and thereby prevents the interaction between DDX58 and MAVS. In turn, IFN-beta production is impaired. Interacts with host AUP1 which mediates induction of lipophagy in host cells and facilitates production of virus progeny particles (By similarity).

Peptide 2k:

Functions as a signal peptide for NS4B and is required for the interferon antagonism activity of the latter.

Non-structural protein 4B:

Induces the formation of ER-derived membrane vesicles where the viral replication takes place (By similarity).

Inhibits interferon (IFN)-induced host STAT1 phosphorylation and nuclear translocation, thereby preventing the establishment of a cellular antiviral state by blocking the IFN-alpha/beta pathway (PubMed:15956546).

RNA-directed RNA polymerase NS5:

Replicates the viral (+) and (-) RNA genome, and performs the capping of genomes in the cytoplasm. NS5 methylates viral RNA cap at guanine N-7 and ribose 2'-O positions. Besides its role in RNA genome replication, also prevents the establishment of cellular antiviral state by blocking the interferon-alpha/beta (IFN-alpha/beta) signaling pathway. Inhibits host TYK2 and STAT2 phosphorylation, thereby preventing activation of JAK-STAT signaling pathway.

Reference:

1. Morens DM, Fauci AS. Dengue and hemorrhagic fever: a potential threat to public health in the United States. Jama. 2008;299:214–216.

2. Gould EA, Solomon T. Pathogenic flaviviruses. Lancet. 2008;371:500–509.

3. Kuhn RJ. The Flaviviruses. In: Acheson NH, editor. Fundamentals of Molecular Virology. 2004. in press. 

4. Ma L, Jones CT, Groesch TD, Kuhn RJ, Post CB. Solution structure of dengue virus capsid protein reveals another fold. Proc Natl Acad Sci U S A. 2004;101:3414–3419.

5. Modis Y, Ogata S, Clements D, Harrison SC. A ligand-binding pocket in the dengue virus envelope glycoprotein. Proc Natl Acad Sci USA. 2003;100:6986–6991.