Molecular mechanisms involved in the early steps of flavivirus cell entry

Abstract

Flaviviruses enter their host cells by receptor-mediated endocytosis, a well-orchestrated process of receptor recognition, penetration and uncoating. Recent findings on these early steps in the life cycle of flaviviruses are the focus of this review. Keywords FLAVIVIRUS; CELL ENTRY; RECEPTOR; ENDOCYTOSIS; ENVELOPE PROTEIN; PH ENVIRONMENT; STRUCTUREThe Flaviviridae are a family of small, enveloped RNA viruses that is comprised of three genera: Flavivirus, Hepacivirus, and Pestivirus. More than 70 viruses have been classified in the genus Flavivirus [1]. The genus includes various noteworthy mosquito-and tick-borne human pathogens, such as Yellow Fever virus (YFV), dengue virus (DENV), Tick-borne Encephalitis Virus (TBEV), and West Nile virus (WNV), that are subclassified into several antigenic complexes and phylogenetic groups [2]. Flaviviruses are typically associated with mild systemic disease, but can also cause severe symptoms such as hemorrhagic fever, encephalitis or death. Many of these viruses are resurgent, are spreading to new environments and are responsible for substantial morbidity and mortality around the globe. Flaviviruses are primarily transmitted through arthropod vectors. Humans and other mammals are not known to commonly develop infectious-level viremias and thus are probably incidental hosts with the exceptions of YFV, DENV and TBEV that are sufficiently well-adapted to a mammalian host. The flavivirus lifecycleThe basic stages of the flavivirus life cycle include attachment to the cell surface, internalization into the host cell, transfer of the viral RNA genome into the cytoplasm, translation of the viral proteins, replication of the genomic RNA, assembly and maturation of the virions, and ultimately the release of progeny viruses from the cell.Flaviviruses are lipid-enveloped viruses (Fig. 1A). After recognition and attachment to specific receptor molecules on the surface of the cell, the virus is internalized into the host * Correspondence should be addressed to M.G.R. (mr@purdue.edu, Tel. 765-494-4911, FAX 765-496-1189).Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. . The polyprotein is subsequently glycosylated by cellular glycosyltransferases and cleaved by a combination of viral and host proteases to release three structural (C, prM, and E) and seven non-structural proteins (NS1, NS2a, NS2b, NS3, NS4a, NS4b, and NS5). NS3 and NS5 are the bestcharacterized non-structural proteins that assemble with several other viral and host proteins to form the replication complex. NS3 combines helicase/NTPase, serine protease, and RNA triphosphatase...

The Membrane-Proximal “Stem” Region Increases the Stability of the Flavivirus E Protein Postfusion Trimer and Modulates Its Structure

“…These small enveloped viruses infect cells by receptor-mediated endocytosis and acidic-pH-induced membrane fusion in endosomes (2,3). The fusion reaction is mediated by the major envelope protein E, a class II fusion protein (4), which contains three domains (DI, DII, and DIII), a membrane-proximal region (the so-called "stem"), and the carboxy-terminal transmembrane anchor (Fig.…”

Productive Dengue Virus Infection of Human Endothelial Cells Is Directed by Heparan Sulfate-Containing Proteoglycan Receptors

“…The dengue virus envelope protein reportedly binds to Fc receptors, DC-SIGN, ICAM3, CD14, HSP70/90, GRP78, laminin receptor, and the mannose receptor (13,16,40,54,55,58,72). In addition, heparan sulfate proteoglycans (HSPGs) are also implicated as dengue virus attachment targets of Vero E6 and liver cell lines (15,29,36,45).…”

Dengue Envelope Domain III-Peptide Binding Analysis <i>via</i> Tryptophan Fluorescence Quenching Assay

“…In the peptide-induced fluorescence quenching experiment, black 96-well microplates were filled with a final concentration of 100 µM of EIII in 1X PBS pH 7.4 containing the peptides of a varying concentrations (2,8,20 and 40 µM); and the samples were incubated at 25°C for 1 h. The final concentration of DMSO and DMF was fixed to 1%. To diminish the effects of DMSO and DMF on the tryptophan fluorescence of EIII in the peptide-induced fluorescence experiment, a reference control was prepared where 1% of each solvent was added to EIII without the presence of peptide.…”

“…[3][4][5][6][7][8][9] For this reason, the EIII protein is believed to be a potential target for anti-dengue drugs. The EIII inhibitors may confer inhibition of the cellular entry of the DENV.…”