Arenavirus Stable Signal Peptide Is the Keystone Subunit for Glycoprotein Complex Organization

The rodent arenavirus glycoprotein complex encodes a stable signal peptide (SSP) that is an essential structural component of mature virions. The SSP, GP1, and GP2 subunits of the trimeric glycoprotein complex noncovalently interact to stud the surface of virions and initiate arenavirus infectivity....

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Bibliographic Details
Published in:mBio Vol. 5; no. 6; p. e02063
Main Authors: Bederka, Lydia H., Bonhomme, Cyrille J., Ling, Emily L., Buchmeier, Michael J.
Format: Journal Article
Language:English
Published: United States American Society for Microbiology 31.12.2014
American Society of Microbiology
Subjects:
Amino acids
Animals
Antibodies
biosynthesis
Cell Line
Cell Membrane - chemistry
Cell Membrane - virology
Cell membranes
Confocal microscopy
Endoplasmic reticulum
Endosomes
Enzymes
fever
Flow Cytometry
Genomes
Glycoproteins
Glycoproteins - metabolism
Golgi apparatus
Hemorrhagic fever
Humans
Immunoprecipitation
Infectivity
Internalization
Lymphocytic choriomeningitis mammarenavirus
Lymphocytic choriomeningitis virus - physiology
Maturation
Membrane fusion
Membrane trafficking
Microscopy
Microscopy, Confocal
Molecular Biology
Mutation
pathogenicity
pathogens
Peptides
pH effects
plasma membrane
polypeptides
precipitin tests
Protein Multimerization
Protein Processing, Post-Translational
Protein Sorting Signals
Protein Subunits - metabolism
Protein Transport
Proteins
Proteolysis
receptors
RNA polymerase
rodents
signal peptide
Viral Structural Proteins - metabolism
virion
Virions
Viruses
ISSN:2161-2129, 2150-7511, 2150-7511
Online Access:Get full text
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Description
Summary:The rodent arenavirus glycoprotein complex encodes a stable signal peptide (SSP) that is an essential structural component of mature virions. The SSP, GP1, and GP2 subunits of the trimeric glycoprotein complex noncovalently interact to stud the surface of virions and initiate arenavirus infectivity. Nascent glycoprotein production undergoes two proteolytic cleavage events: first within the endoplasmic reticulum (ER) to cleave SSP from the remaining precursor GP1/2 (glycoprotein complex [GPC]) glycoprotein and second within the Golgi stacks by the cellular SKI-1/S1P for GP1/2 processing to yield GP1 and GP2 subunits. Cleaved SSP is not degraded but retained as an essential glycoprotein subunit. Here, we defined functions of the 58-amino-acid lymphocytic choriomeningitis virus (LCMV) SSP in regard to glycoprotein complex processing and maturation. Using molecular biology techniques, confocal microscopy, and flow cytometry, we detected SSP at the plasma membrane of transfected cells. Further, we identified a sorting signal (FLLL) near the carboxyl terminus of SSP that is required for glycoprotein maturation and trafficking. In the absence of SSP, the glycoprotein accumulated within the ER and was unable to undergo processing by SKI-1/S1P. Mutation of this highly conserved FLLL motif showed impaired glycoprotein processing and secretory pathway trafficking, as well as defective surface expression and pH-dependent membrane fusion. Immunoprecipitation of SSP confirmed an interaction between the signal peptide and the GP2 subunit; however, mutations within this FLLL motif disrupted the association of the GP1 subunit with the remaining glycoprotein complex. IMPORTANCE Several members of the Arenaviridae family are neglected human pathogens capable of causing illness ranging from a nondescript flu-like syndrome to fulminant hemorrhagic fever. Infections by arenaviruses are mediated by attachment of the virus glycoprotein to receptors on host cells and virion internalization by fusion within an acidified endosome. SSP plays a critical role in the fusion of the virus with the host cell membrane. Within infected cells, the retained glycoprotein SSP plays a neglected yet essential role in glycoprotein biosynthesis. Without this 6-kDa polypeptide, the glycoprotein precursor is retained within the endoplasmic reticulum, and trafficking to the plasma membrane where SSP, GP1, and GP2 localize for glycoprotein assembly into infectious virions is inhibited. To investigate SSP contributions to glycoprotein maturation and function, we created an SSP-tagged glycoprotein to directly detect and manipulate this subunit. This resource will aid future studies to identify host factors that mediate glycoprotein maturation. Several members of the Arenaviridae family are neglected human pathogens capable of causing illness ranging from a nondescript flu-like syndrome to fulminant hemorrhagic fever. Infections by arenaviruses are mediated by attachment of the virus glycoprotein to receptors on host cells and virion internalization by fusion within an acidified endosome. SSP plays a critical role in the fusion of the virus with the host cell membrane. Within infected cells, the retained glycoprotein SSP plays a neglected yet essential role in glycoprotein biosynthesis. Without this 6-kDa polypeptide, the glycoprotein precursor is retained within the endoplasmic reticulum, and trafficking to the plasma membrane where SSP, GP1, and GP2 localize for glycoprotein assembly into infectious virions is inhibited. To investigate SSP contributions to glycoprotein maturation and function, we created an SSP-tagged glycoprotein to directly detect and manipulate this subunit. This resource will aid future studies to identify host factors that mediate glycoprotein maturation.
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Present address: Cyrille J. Bonhomme, PPD, Vaccine Sciences Department, Richmond, Virginia, USA; Emily L. Ling, Department of Art as Applied to Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
This article is a direct contribution from a Fellow of the American Academy of Microbiology.
Editor Terence S. Dermody, Vanderbilt University School of Medicine
ISSN:2161-2129
2150-7511
2150-7511
DOI:10.1128/mBio.02063-14