A Novel Zinc-Binding Domain Is Essential for Formation of the Functional Junín Virus Envelope Glycoprotein Complex

Self Cite

159

The arenavirus envelope glycoprotein (GPC) mediates viral entry through pH-induced membrane fusion in the endosome. This crucial process in the viral life cycle can be specifically inhibited in the New World arenaviruses by the small-molecule compound ST-294. Here, we show that ST-294 interferes with GPCmediated membrane fusion by targeting the interaction of the G2 fusion subunit with the stable signal peptide (SSP). We demonstrate that amino acid substitutions at lysine-33 of the Junín virus SSP confer resistance to ST-294 and engender de novo sensitivity to ST-161, a chemically distinct inhibitor of the Old World Lassa fever virus. These compounds, as well as a broadly active inhibitor, ST-193, likely share a molecular target at the SSP-G2 interface. We also show that both ST-294 and ST-193 inhibit pH-induced dissociation of the G1 receptor-binding subunit from GPC, a process concomitant with fusion activation. Interestingly, the inhibitory activity of these molecules can in some cases be overcome by further lowering the pH used for activation. Our results suggest that these small molecules act to stabilize the prefusion GPC complex against acidic pH. The pH-sensitive interaction between SSP and G2 in GPC represents a robust molecular target for the development of antiviral compounds for the treatment of arenavirus hemorrhagic fevers.

Section: Molecular and Chemical Reagents And Monoclonal Antibodies (Mmentioning

confidence: 99%

mentioning

confidence: 99%

pH-Induced Activation of Arenavirus Membrane Fusion Is Antagonized by Small-Molecule Inhibitors

York

Dai

Amberg

et al. 2008

Self Cite

159

“…Curiously, the SSP can be expressed in trans and will associate with the G1-G2 precursor to reconstitute the functional complex (21,77). The SSP associates with the cytoplasmic domain of G2, likely through an intersubunit zinc finger structure (73). Among its several roles, the SSP is required for the transit of the complex through the Golgi apparatus (2,21).…”

mentioning

confidence: 99%

Assembly of Arenavirus Envelope Glycoprotein GPC in Detergent-Soluble Membrane Microdomains

Agnihothram

Dancho²,

Grant

et al. 2009

Self Cite

The family Arenaviridae includes a number of highly pathogenic viruses that are responsible for acute hemorrhagic fevers in humans. Genetic diversity among arenavirus species in their respective rodent hosts supports the continued emergence of new pathogens. In the absence of available vaccines or therapeutic agents, the hemorrhagic fever arenaviruses remain a serious public health and biodefense concern. Arenaviruses are enveloped virions that assemble and bud from the plasma membrane. In this study, we have characterized the microdomain organization of the virus envelope glycoprotein (GPC) on the cell surface by using immunogold electron microscopy. We find that Junín virus (JUNV) GPC clusters into discrete microdomains of 120 to 160 nm in diameter and that this property of GPC is independent of its myristoylation and of coexpression with the virus matrix protein Z. In cells infected with the Candid#1 strain of JUNV, and in purified Candid#1 virions, these GPC microdomains are soluble in cold Triton X-100 detergent and are thus distinct from conventional lipid rafts, which are utilized by numerous other viruses for assembly. Virion morphogenesis ultimately requires colocalization of viral components, yet our dual-label immunogold staining studies failed to reveal a spatial association of Z with GPC microdomains. This observation may reflect either rapid Z-dependent budding of virus-like particles upon coassociation or a requirement for additional viral components in the assembly process. Together, these results provide new insight into the molecular basis for arenavirus morphogenesis.

“…The F49 residue is located within the recently identified FILL sorting signal motif that is required for glycoprotein processing and surface expression (8,24). The C57 residue of GP2, along with its H459, C467, and C469 residues, form a zinc-binding center, which provides the structural basis for association with SSP in the glycoprotein complex in order to modulate optimal membrane fusion activity (25,26).…”

Section: Discussionmentioning

confidence: 99%

“…Many of these residues have been characterized previously in the context of GPC expression and pseudotyped viruses (8,11,(22)(23)(24)(25)(26)(27)(28); however, their biological roles have not been investigated. Here, we show that multiple SSP conserved residues are essential or critical for viral infection of cell culture and/or guinea pigs by participating in the membrane fusion reaction, and that two residues, N37 and R55, are required for viral virulence by a yet-to-be-determined mechanism.…”

mentioning

confidence: 99%

Characterization of the Glycoprotein Stable Signal Peptide in Mediating Pichinde Virus Replication and Virulence

Shao

et al. 2016

Arenaviruses can cause lethal hemorrhagic fevers in humans with few preventative and therapeutic measures. The arenaviral glycoprotein stable signal peptide (SSP) is unique among signal peptides in that it is an integral component of the mature glycoprotein complex (GPC) and plays important roles not only in GPC expression and processing but also in the membrane fusion process during viral entry. Using the Pichinde virus (PICV) reverse genetics system, we analyzed the effects of alanine substitutions at many conserved residues within the SSP on viral replication in cell culture and in a guinea pig infection model. Our data showed that the K33A, F49A, and C57A mutations abolished GPC-mediated cell entry and therefore could not allow for the generation of viable recombinant viruses, demonstrating that these residues are essential for the PICV life cycle. The G2A mutation caused a marked reduction of cell entry at the membrane fusion step, and while this mutant virus was viable, it was significantly attenuated in vitro and in vivo. The N20A mutation also reduced membrane fusion activity and viral virulence in guinea pigs, but it did not significantly affect cell entry or viral growth in cell culture. Two other mutations (N37A and R55A) did not affect membrane fusion or viral growth in vitro but significantly reduced viral virulence in vivo. Taken together, our data suggest that the GPC SSP plays an essential role in mediating viral entry and also contributes to viral virulence in vivo. IMPORTANCESeveral arenaviruses, such as Lassa fever virus, can cause severe and lethal hemorrhagic fever diseases with high mortality and morbidity, and no FDA-approved vaccines or therapies are currently available. Viral entry into cells is mediated by arenavirus GPC that consists of an SSP, the receptor-binding GP1, and transmembrane GP2 protein subunits. Using a reverse genetics system of a prototypic arenavirus, Pichinde virus (PICV), we have shown for the first time in the context of virus infections of cell culture and of guinea pigs that the SSP plays an essential role in mediating the membrane fusion step as well as in other yet-to-be-determined processes during viral infection. Our study provides important insights into the biological roles of GPC SSP and implicates it as a good target for the development of antivirals against deadly human arenavirus pathogens.A renaviruses can cause neurologic or hemorrhagic fever diseases in humans, and few preventive or therapeutic measures are available (1, 2). The most significant arenavirus pathogen is Lassa fever virus (LASV), which causes infections that are endemic to many countries in West Africa, with an estimated 500,000 cases resulting in ϳ5,000 deaths annually (3). Except for Junin virus (JUNV), which has a vaccine, Candid#1, used only in Argentina, no licensed vaccine for human use is currently available for any other arenaviruses. Therapeutic options are limited and depend mainly on supportive care. Ribavirin, a nonspecific antiviral compound, has shown some efficacy ...