scholarly journals The Signal Peptide of the Junín Arenavirus Envelope Glycoprotein Is Myristoylated and Forms an Essential Subunit of the Mature G1-G2 Complex

2004 ◽  
Vol 78 (19) ◽  
pp. 10783-10792 ◽  
Author(s):  
Joanne York ◽  
Victor Romanowski ◽  
Min Lu ◽  
Jack H. Nunberg
Keyword(s):  
Signal Peptide ◽  
Envelope Glycoprotein ◽  
Hemorrhagic Fever ◽  
Gene Replacement ◽  
Etiologic Agent ◽  
Virus Envelope ◽  
Glycoprotein Complex ◽  
Amino Acid Signal Peptide ◽  
Dependent Cell ◽  
And Function

ABSTRACT Arenaviruses comprise a diverse family of rodent-borne viruses that are responsible for recurring and emerging outbreaks of viral hemorrhagic fevers worldwide. The Junín virus, a member of the New World arenaviruses, is endemic to the pampas grasslands of Argentina and is the etiologic agent of Argentine hemorrhagic fever. In this study, we have analyzed the assembly and function of the Junín virus envelope glycoproteins. The mature envelope glycoprotein complex is proteolytically processed from the GP-C precursor polypeptide and consists of three noncovalently associated subunits, G1, G2, and a stable 58-amino-acid signal peptide. This tripartite organization is found both on virions of the attenuated Candid 1 strain and in cells expressing the pathogenic MC2 strain GP-C gene. Replacement of the Junín virus GP-C signal peptide with that of human CD4 has little effect on glycoprotein assembly while abolishing the ability of the G1-G2 complex to mediate pH-dependent cell-cell fusion. In addition, we demonstrate that the Junín virus GP-C signal peptide subunit is myristoylated at its N-terminal glycine. Alanine substitution for the modified glycine residue in the GP-C signal peptide does not affect formation of the tripartite envelope glycoprotein complex but markedly reduces its membrane fusion activity. In contrast to the classical view that signal peptides act primarily in targeting nascent polypeptides to the endoplasmic reticulum, we suggest that the signal peptide of the arenavirus GP-C may serve additional functions in envelope glycoprotein structure and trafficking.

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

2007 ◽  
Vol 81 (24) ◽  
pp. 13385-13391 ◽  
Author(s):  
Joanne York ◽  
Jack H. Nunberg
Keyword(s):  
Membrane Fusion ◽  
Envelope Glycoprotein ◽  
Zinc Binding ◽  
Target Cells ◽  
Viral Fusion ◽  
Virus Envelope ◽  
Glycoprotein Complex ◽  
Amino Acid Signal Peptide ◽  
C Complex ◽  
Zinc Binding Domain

ABSTRACT The envelope glycoprotein of the Junín arenavirus (GP-C) mediates entry into target cells through a pH-dependent membrane fusion mechanism. Unlike other class I viral fusion proteins, the mature GP-C complex retains a cleaved, 58-amino-acid signal peptide (SSP) as an essential subunit, required both for trafficking of GP-C to the cell surface and for the activation of membrane fusion. SSP has been shown to associate noncovalently in GP-C via the cytoplasmic domain (CTD) of the transmembrane fusion subunit G2. In this report we investigate the molecular basis for this intersubunit interaction. We identify an invariant series of six cysteine and histidine residues in the CTD of G2 that is essential for incorporation of SSP in the GP-C complex. Moreover, we show that a CTD peptide fragment containing His-447, His-449, and Cys-455 specifically binds Zn2+ at subnanomolar concentrations. Together, these results suggest a zinc finger-like domain structure in the CTD of G2. We propose that the remaining residues in the series (His-459, Cys-467, and Cys-469) form an intersubunit zinc-binding center that incorporates Cys-57 of SSP. This unusual motif may act to retain SSP in the GP-C complex and position the ectodomain loop of SSP for its role in modulating membrane fusion activity. The unique tripartite organization of GP-C could provide novel molecular targets for therapeutic intervention in arenaviral disease.

scholarly journals A Specific Interaction of Small Molecule Entry Inhibitors with the Envelope Glycoprotein Complex of the Junín Hemorrhagic Fever Arenavirus

2010 ◽  
Vol 286 (8) ◽  
pp. 6192-6200 ◽  
Author(s):  
Celestine J. Thomas ◽  
Hedi E. Casquilho-Gray ◽  
Joanne York ◽  
Dianne L. DeCamp ◽  
Dongcheng Dai ◽  
...  
Keyword(s):  
Small Molecule ◽  
Envelope Glycoprotein ◽  
Specific Interaction ◽  
Hemorrhagic Fever ◽  
Entry Inhibitors ◽  
Glycoprotein Complex

scholarly journals Probing the antigenicity of hepatitis C virus envelope glycoprotein complex by high-throughput mutagenesis

2017 ◽  
Vol 13 (12) ◽  
pp. e1006735 ◽  
Author(s):  
Radhika Gopal ◽  
Kelli Jackson ◽  
Netanel Tzarum ◽  
Leopold Kong ◽  
Andrew Ettenger ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
High Throughput ◽  
Envelope Glycoprotein ◽  
Virus Envelope ◽  
Glycoprotein Complex

scholarly journals Immunogenicity and functional characterization of Leishmania-derived hepatitis C virus envelope glycoprotein complex

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Katarzyna Grzyb ◽  
Anna Czarnota ◽  
Agnieszka Brzozowska ◽  
Anna Cieślik ◽  
Łukasz Rąbalski ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Envelope Glycoprotein ◽  
Functional Characterization ◽  
Virus Envelope ◽  
Glycoprotein Complex

scholarly journals Intersubunit Interactions Modulate pH-Induced Activation of Membrane Fusion by the Junín Virus Envelope Glycoprotein GPC

2009 ◽  
Vol 83 (9) ◽  
pp. 4121-4126 ◽  
Author(s):  
Joanne York ◽  
Jack H. Nunberg
Keyword(s):  
Membrane Fusion ◽  
Envelope Glycoprotein ◽  
Specific Interaction ◽  
Hemorrhagic Fever ◽  
Virus Envelope ◽  
Alanine Scanning Mutagenesis ◽  
Ph Dependent ◽  
Membrane Spanning ◽  
Intersubunit Interactions ◽  
Stable Signal

ABSTRACT The mature arenavirus envelope glycoprotein GPC is a tripartite complex comprising a stable signal peptide (SSP) in addition to the receptor-binding (G1) and transmembrane fusion (G2) subunits. We have shown previously that SSP is a key element in GPC-mediated membrane fusion, and that GPC sensitivity to acidic pH is modulated in part through the lysine residue at position 33 in the ectodomain loop of SSP (J. York and J. H. Nunberg, J. Virol. 80:7775-7780, 2006). A glutamine substitution at this position stabilizes the native GPC complex and thereby prevents the induction of pH-dependent membrane fusion. In efforts to identify the intersubunit interactions of K33, we performed alanine-scanning mutagenesis at charged residues in the membrane-proximal ectodomain of G2 and determined the ability of these mutations to rescue the fusion deficiency in K33Q GPC. Four second-site mutations that specifically complement K33Q were identified (D400A, E410A, R414A, and K417A). Moreover, complementation was also observed at three hydrophobic positions in the membrane-spanning domain of G2 (F427, W428, and F438). Interestingly, all of the complementing mutations restored wild-type pH sensitivity to the K33Q mutant, while none themselves affected the pH of membrane fusion. Our studies demonstrate a specific interaction between SSP and G2 that is involved in priming the native GPC complex for pH-induced membrane fusion. Importantly, this pH-dependent interaction has been shown to be vulnerable to small-molecule compounds that stabilize the native complex and prevent the activation of membrane fusion. A detailed mechanistic understanding of the control of GPC-mediated membrane fusion will be important in guiding the development of effective therapeutics against arenaviral hemorrhagic fever.

scholarly journals Role of the Stable Signal Peptide and Cytoplasmic Domain of G2 in Regulating Intracellular Transport of the Junín Virus Envelope Glycoprotein Complex

2006 ◽  
Vol 80 (11) ◽  
pp. 5189-5198 ◽  
Author(s):  
Sudhakar S. Agnihothram ◽  
Joanne York ◽  
Jack H. Nunberg
Keyword(s):  
Cell Surface ◽  
Signal Peptide ◽  
Envelope Glycoprotein ◽  
Intracellular Transport ◽  
Cytoplasmic Domain ◽  
Virus Envelope ◽  
Quality Control Process ◽  
C Complex ◽  
Stable Signal

ABSTRACT Enveloped viruses utilize the membranous compartments of the host cell for the assembly and budding of new virion particles. In this report, we have investigated the biogenesis and trafficking of the envelope glycoprotein (GP-C) of the Junín arenavirus. The mature GP-C complex is unusual in that it retains a stable signal peptide (SSP) as an essential component in association with the typical receptor-binding (G1) and transmembrane fusion (G2) subunits. We demonstrate that, in the absence of SSP, the G1-G2 precursor is restricted to the endoplasmic reticulum (ER). This constraint is relieved by coexpression of SSP in trans, allowing transit of the assembled GP-C complex through the Golgi and to the cell surface, the site of arenavirus budding. Transport of a chimeric CD4 glycoprotein bearing the transmembrane and cytoplasmic domains of G2 is similarly regulated by SSP association. Truncations to the cytoplasmic domain of G2 abrogate SSP association yet now permit transport of the G1-G2 precursor to the cell surface. Thus, the cytoplasmic domain of G2 is an important determinant for both ER localization and its control through SSP binding. Alanine mutations to either of two dibasic amino acid motifs in the G2 cytoplasmic domain can also mobilize the G1-G2 precursor for transit through the Golgi. Taken together, our results suggest that SSP binding masks endogenous ER localization signals in the cytoplasmic domain of G2 to ensure that only the fully assembled, tripartite GP-C complex is transported for virion assembly. This quality control process points to an important role of SSP in the structure and function of the arenavirus envelope glycoprotein.

scholarly journals Role of the Stable Signal Peptide of Junín Arenavirus Envelope Glycoprotein in pH-Dependent Membrane Fusion

2006 ◽  
Vol 80 (15) ◽  
pp. 7775-7780 ◽  
Author(s):  
Joanne York ◽  
Jack H. Nunberg
Keyword(s):  
Amino Acid ◽  
Membrane Fusion ◽  
Signal Peptide ◽  
Envelope Glycoprotein ◽  
Amino Acid Signal Peptide ◽  
Ph Dependent ◽  
Mediate Cell ◽  
C Complex ◽  
Stable Signal

ABSTRACT The envelope glycoprotein of the arenaviruses (GP-C) is unusual in that the mature complex retains the cleaved, 58-amino-acid signal peptide. Association of this stable signal peptide (SSP) has been shown to be essential for intracellular trafficking and proteolytic maturation of the GP-C complex. We identify here a specific and previously unrecognized role of SSP in pH-dependent membrane fusion. Amino acid substitutions that alter the positive charge at lysine K33 in SSP affect the ability of GP-C to mediate cell-cell fusion and the threshold pH at which membrane fusion is triggered. Based on the presumed location of K33 at or near the luminal domain of SSP, we postulate that SSP interacts with the membrane-proximal or transmembrane regions of the G2 fusion protein. This unique organization of the GP-C complex may suggest novel strategies for intervention in arenavirus infection.

Human immunodeficiency virus envelope glycoprotein 120 alters sleep and induces cytokine mRNA expression in rats [published errata appear in Am J Physiol 1996 Aug;271(2 Pt 2):section R following table of contents and 1996 Dec;271(6 Pt 3):section R following table of contents]

1996 ◽  
Vol 270 (5) ◽  
pp. R963-R970 ◽  
Author(s):  
M. R. Opp ◽  
P. L. Rady ◽  
T. K. Hughes ◽  
P. Cadet ◽  
S. K. Tyring ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Mrna Expression ◽  
Eye Movement ◽  
Envelope Glycoprotein ◽  
Brain Temperature ◽  
Etiologic Agent ◽  
Rapid Eye Movement ◽  
Rapid Eye Movement Sleep ◽  
Virus Envelope ◽  
Immunodeficiency Virus

Sleep is altered during the course of viral infection, including that in which the human immunodeficiency virus (HIV) is the etiologic agent. Alterations in the sleep of HIV-infected individuals occur early in the course of infection, prior to the onset of AIDS. The mechanisms for such alterations in sleep are not known. The HIV envelope glycoprotein 120 (gp120) induces the synthesis and secretion of cytokines that enhance [e.g., interleukin (IL)-1 and tumor necrosis factor] and suppress (e.g., IL-10 and IL-1 receptor antagonist) sleep. We used a well-defined rat model to test the hypothesis that the HIV gp120 alters sleep. Recombinant HIV-1IIIB gp120 was injected intracerebroventricularly (20- 500 ng) into rats prior to dark onset. Sleep-wake behavior was not altered after the 20-ng dose, whereas both non-rapid eye movement sleep (NREMS) and rapid eye movement sleep (REMS) were initially enhanced and subsequently suppressed after the 100-ng dose. NREMS was enhanced for 8 h after the 500-ng dose; REMS was not affected by this dose. Brain temperature was not altered by any of the gp120 doses used in this study. In addition, mRNA expression for IL-1 beta and IL-10 was induced in the hypothalamus by gp120; this brain region is crucial for the regulation of sleep. These new data support the hypothesis that altered cytokine concentrations within the central nervous system play a pivotal role in the complex alterations in sleep observed during HIV infection.

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