scholarly journals Analyses of Coronavirus Assembly Interactions with Interspecies Membrane and Nucleocapsid Protein Chimeras

2016 ◽  
Vol 90 (9) ◽  
pp. 4357-4368 ◽  
Author(s):  
Lili Kuo ◽  
Kelley R. Hurst-Hess ◽  
Cheri A. Koetzner ◽  
Paul S. Masters
Keyword(s):  
Nucleocapsid Protein ◽  
Hepatitis Virus ◽  
Virus Assembly ◽  
Mouse Hepatitis Virus ◽  
M Protein ◽  
Growth Defect ◽  
S Protein ◽  
N Protein ◽  
Protein Incorporation ◽  
Carboxy Terminal

ABSTRACTThe coronavirus membrane (M) protein is the central actor in virion morphogenesis. M organizes the components of the viral membrane, and interactions of M with itself and with the nucleocapsid (N) protein drive virus assembly and budding. In order to further define M-M and M-N interactions, we constructed mutants of the model coronavirus mouse hepatitis virus (MHV) in which all or part of the M protein was replaced by its phylogenetically divergent counterpart from severe acute respiratory syndrome coronavirus (SARS-CoV). We were able to obtain viable chimeras containing the entire SARS-CoV M protein as well as mutants with intramolecular substitutions that partitioned M protein at the boundaries between the ectodomain, transmembrane domains, or endodomain. Our results show that the carboxy-terminal domain of N protein, N3, is necessary and sufficient for interaction with M protein. However, despite some previous genetic and biochemical evidence that mapped interactions with N to the carboxy terminus of M, it was not possible to define a short linear region of M protein sufficient for assembly with N. Thus, interactions with N protein likely involve multiple linearly discontiguous regions of the M endodomain. The SARS-CoV M chimera exhibited a conditional growth defect that was partially suppressed by mutations in the envelope (E) protein. Moreover, virions of the M chimera were markedly deficient in spike (S) protein incorporation. These findings suggest that the interactions of M protein with both E and S protein are more complex than previously thought.IMPORTANCEThe assembly of coronavirus virions entails concerted interactions among the viral structural proteins and the RNA genome. One strategy to study this process is through construction of interspecies chimeras that preserve or disrupt particular inter- or intramolecular associations. In this work, we replaced the membrane (M) protein of the model coronavirus mouse hepatitis virus with its counterpart from a heterologous coronavirus. The results clarify our understanding of the interaction between the coronavirus M protein and the nucleocapsid protein. At the same time, they reveal unanticipated complexities in the interactions of M with the viral spike and envelope proteins.

scholarly journals Identification of In Vivo-Interacting Domains of the Murine Coronavirus Nucleocapsid Protein

2009 ◽  
Vol 83 (14) ◽  
pp. 7221-7234 ◽  
Author(s):  
Kelley R. Hurst ◽  
Cheri A. Koetzner ◽  
Paul S. Masters
Keyword(s):  
Nucleocapsid Protein ◽  
Fluorescent Protein ◽  
Hepatitis Virus ◽  
M Protein ◽  
N Protein ◽  
Terminal Domain ◽  
Domain 3 ◽  
Positive Strand Rna ◽  
Carboxy Terminal

ABSTRACT The coronavirus nucleocapsid protein (N), together with the large, positive-strand RNA viral genome, forms a helically symmetric nucleocapsid. This ribonucleoprotein structure becomes packaged into virions through association with the carboxy-terminal endodomain of the membrane protein (M), which is the principal constituent of the virion envelope. Previous work with the prototype coronavirus mouse hepatitis virus (MHV) has shown that a major determinant of the N-M interaction maps to the carboxy-terminal domain 3 of the N protein. To explore other domain interactions of the MHV N protein, we expressed a series of segments of the MHV N protein as fusions with green fluorescent protein (GFP) during the course of viral infection. We found that two of these GFP-N-domain fusion proteins were selectively packaged into virions as the result of tight binding to the N protein in the viral nucleocapsid, in a manner that did not involve association with either M protein or RNA. The nature of each type of binding was further explored through genetic analysis. Our results defined two strongly interacting regions of the N protein. One is the same domain 3 that is critical for M protein recognition during assembly. The other is domain N1b, which corresponds to the N-terminal domain that has been structurally characterized in detail for two other coronaviruses, infectious bronchitis virus and the severe acute respiratory syndrome coronavirus.

scholarly journals A Conserved Domain in the Coronavirus Membrane Protein Tail Is Important for Virus Assembly

2010 ◽  
Vol 84 (21) ◽  
pp. 11418-11428 ◽  
Author(s):  
Ariel L. Arndt ◽  
Blake J. Larson ◽  
Brenda G. Hogue
Keyword(s):  
Protein Interactions ◽  
Hepatitis Virus ◽  
Virus Assembly ◽  
Viral Envelope ◽  
Mutant Proteins ◽  
N Protein ◽  
Conserved Domain ◽  
M Proteins ◽  
A Charge ◽  
Carboxy Terminal

ABSTRACT Coronavirus membrane (M) proteins play key roles in virus assembly, through M-M, M-spike (S), and M-nucleocapsid (N) protein interactions. The M carboxy-terminal endodomain contains a conserved domain (CD) following the third transmembrane (TM) domain. The importance of the CD (SWWSFNPETNNL) in mouse hepatitis virus was investigated with a panel of mutant proteins, using genetic analysis and transient-expression assays. A charge reversal for negatively charged E121 was not tolerated. Lysine (K) and arginine (R) substitutions were replaced in recovered viruses by neutrally charged glutamine (Q) and leucine (L), respectively, after only one passage. E121Q and E121L M proteins were capable of forming virus-like particles (VLPs) when coexpressed with E, whereas E121R and E121K proteins were not. Alanine substitutions for the first four or the last four residues resulted in viruses with significantly crippled phenotypes and proteins that failed to assemble VLPs or to be rescued into the envelope. All recovered viruses with alanine substitutions in place of SWWS residues had second-site, partially compensating, changes in the first TM of M. Alanine substitution for proline had little impact on the virus. N protein coexpression with some M mutants increased VLP production. The results overall suggest that the CD is important for formation of the viral envelope by helping mediate fundamental M-M interactions and that the presence of the N protein may help stabilize M complexes during virus assembly.

scholarly journals Retargeting of Coronavirus by Substitution of the Spike Glycoprotein Ectodomain: Crossing the Host Cell Species Barrier

2000 ◽  
Vol 74 (3) ◽  
pp. 1393-1406 ◽  
Author(s):  
Lili Kuo ◽  
Gert-Jan Godeke ◽  
Martin J. B. Raamsman ◽  
Paul S. Masters ◽  
Peter J. M. Rottier
Keyword(s):  
Host Cell ◽  
Reverse Genetics ◽  
Hepatitis Virus ◽  
Rna Recombination ◽  
Spike Glycoprotein ◽  
Species Barrier ◽  
S Protein ◽  
Narrow Host Range ◽  
Protein Incorporation ◽  
Carboxy Terminal

ABSTRACT Coronaviruses generally have a narrow host range, infecting one or just a few species. Using targeted RNA recombination, we constructed a mutant of the coronavirus mouse hepatitis virus (MHV) in which the ectodomain of the spike glycoprotein (S) was replaced with the highly divergent ectodomain of the S protein of feline infectious peritonitis virus. The resulting chimeric virus, designated fMHV, acquired the ability to infect feline cells and simultaneously lost the ability to infect murine cells in tissue culture. This reciprocal switch of species specificity strongly supports the notion that coronavirus host cell range is determined primarily at the level of interactions between the S protein and the virus receptor. The isolation of fMHV allowed the localization of the region responsible for S protein incorporation into virions to the carboxy-terminal 64 of the 1,324 residues of this protein. This establishes a basis for further definition of elements involved in virion assembly. In addition, fMHV is potentially the ideal recipient virus for carrying out reverse genetics of MHV by targeted RNA recombination, since it presents the possibility of selecting recombinants, no matter how defective, that have regained the ability to replicate in murine cells.

scholarly journals Two palmitylated cysteine residues of the severe acute respiratory syndrome coronavirus spike (S) protein are critical for S incorporation into virus-like particles, but not for M–S co-localization

2012 ◽  
Vol 93 (4) ◽  
pp. 823-828 ◽  
Author(s):  
Makoto Ujike ◽  
Cheng Huang ◽  
Kazuya Shirato ◽  
Shutoku Matsuyama ◽  
Shinji Makino ◽  
...  
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Hepatitis Virus ◽  
Mouse Hepatitis Virus ◽  
Immunofluorescence Assay ◽  
M Protein ◽  
Cysteine Residues ◽  
S Protein ◽  
Virion Assembly ◽  
Virus Like Particles ◽  
S Proteins

The endodomain of several coronavirus (CoV) spike (S) proteins contains palmitylated cysteine residues and enables co-localization and interaction with the CoV membrane (M) protein. Depalmitylation of mouse hepatitis virus S proteins abolished this interaction, resulting in the failure of S incorporation into virions. In contrast, an immunofluorescence assay (IFA) showed that depalmitylated severe acute respiratory syndrome coronavirus (SCoV) S proteins still co-localized with the M protein in the budding site. Here, we determined the ability of depalmitylated SCoV S mutants to incorporate S into virus-like particles (VLPs). IFA confirmed that all SCoV S mutants co-localized with the M protein intracellularly. However, the mutants lacking two cysteine residues (C1234/1235) failed to incorporate S into VLPs. This indicated that these palmitylated cysteines are essential for S incorporation, but are not involved in S co-localization mediated by the M protein. Our findings suggest that M–S co-localization and S incorporation occur independently of one another in SCoV virion assembly.

scholarly journals Envelope glycoprotein interactions in coronavirus assembly.

1995 ◽  
Vol 131 (2) ◽  
pp. 339-349 ◽  
Author(s):  
D J Opstelten ◽  
M J Raamsman ◽  
K Wolfs ◽  
M C Horzinek ◽  
P J Rottier
Keyword(s):  
Envelope Glycoprotein ◽  
Hepatitis Virus ◽  
Virus Assembly ◽  
Higher Order ◽  
M Protein ◽  
Lag Phase ◽  
S Protein ◽  
Viral Membrane ◽  
Golgi Membranes ◽  
S Proteins

Coronaviruses are assembled by budding into smooth membranes of the intermediate ER-to-Golgi compartment. We have studied the association of the viral membrane glycoproteins M and S in the formation of the virion envelope. Using coimmunoprecipitation analysis we demonstrated that the M and S proteins of mouse hepatitis virus (MHV) interact specifically forming heteromultimeric complexes in infected cells. These could be detected only when the detergents used for their solubilization from cells or virions were carefully chosen: a combination of nonionic (NP-40) and ionic (deoxycholic acid) detergents proved to be optimal. Pulse-chase experiments revealed that newly made M and S proteins engaged in complex formation with different kinetics. Whereas the M protein appeared in complexes immediately after its synthesis, newly synthesized S protein did so only after a lag phase of > 20 min. Newly made M was incorporated into virus particles faster than S, which suggests that it associates with preexisting S molecules. Using the vaccinia virus T7-driven coexpression of M and S we also demonstrate formation of M/S complexes in the absence of other coronaviral proteins. Pulse-chase labelings and coimmunoprecipitation analyses revealed that M and S associate in pre-Golgi membranes because the unglycosylated form of M appeared in M/S complexes rapidly. Since no association of M and S was detected when protein export from the ER was blocked by brefeldin A, stable complexes most likely arise in the ER-to-Golgi intermediate compartment. Sucrose velocity gradient analysis showed the M/S complexes to be heterogeneous and of higher order, suggesting that they are maintained by homo- and heterotypic interactions. M/S complexes colocalized with alpha-mannosidase II, a resident Golgi protein. They acquired Golgi-specific oligosaccharide modifications but were not detected at the cell surface. Thus, the S protein, which on itself was transported to the plasma membrane, was retained in the Golgi complex by its association with the M protein. Because coronaviruses bud at pre-Golgi membranes, this result implies that the envelope glycoprotein complexes do not determine the site of budding. Yet, the self-association of the MHV envelope glycoproteins into higher order complexes is indicative of its role in the sorting of the viral membrane proteins and in driving the formation of the viral lipoprotein coat in virus assembly.

scholarly journals Enhanced Virulence Mediated by the Murine Coronavirus, Mouse Hepatitis Virus Strain JHM, Is Associated with a Glycine at Residue 310 of the Spike Glycoprotein

2003 ◽  
Vol 77 (19) ◽  
pp. 10260-10269 ◽  
Author(s):  
Evelena Ontiveros ◽  
Taeg S. Kim ◽  
Thomas M. Gallagher ◽  
Stanley Perlman
Keyword(s):  
Virus Strain ◽  
Hepatitis Virus ◽  
Neurological Diseases ◽  
Mouse Hepatitis Virus ◽  
Neutralizing Antibody ◽  
Lateral Spread ◽  
S Protein ◽  
Acute Encephalitis ◽  
The Central Nervous System

ABSTRACT The coronavirus, mouse hepatitis virus strain JHM, causes acute and chronic neurological diseases in rodents. Here we demonstrate that two closely related virus variants, both of which cause acute encephalitis in susceptible strains of mice, cause markedly different diseases if mice are protected with a suboptimal amount of an anti-JHM neutralizing antibody. One strain, JHM.SD, caused acute encephalitis, while infection with JHM.IA resulted in no acute disease. Using recombinant virus technology, we found that the differences between the two viruses mapped to the spike (S) glycoprotein and that the two S proteins differed at four amino acids. By engineering viruses that differed by only one amino acid, we identified a serine-to-glycine change at position 310 of the S protein (S310G) that recapitulated the more neurovirulent phenotype. The increased neurovirulence mediated by the virus encoding glycine at position S310 was not associated with a different tropism within the central nervous system (CNS) but was associated with increased lateral spread in the CNS, leading to significantly higher brain viral titers. In vitro studies revealed that S310G was associated with decreased S1-S2 stability and with enhanced ability to mediate infection of cells lacking the primary receptor for JHM (“receptor-independent spread”). These enhanced fusogenic properties of viruses encoding a glycine at position 310 of the S protein may contribute to spread within the CNS, a tissue in which expression of conventional JHM receptors is low.

scholarly journals Soluble Receptor Potentiates Receptor-Independent Infection by Murine Coronavirus

2002 ◽  
Vol 76 (3) ◽  
pp. 950-958 ◽  
Author(s):  
Fumihiro Taguchi ◽  
Shutoku Matsuyama
Keyword(s):  
Monoclonal Antibody ◽  
Hepatitis Virus ◽  
Active Form ◽  
Mouse Hepatitis Virus ◽  
Soluble Receptor ◽  
Wild Type ◽  
S Protein ◽  
Bhk Cells ◽  
Direct Binding ◽  
Mediate Cell

ABSTRACT Mouse hepatitis virus (MHV) infection spreads from MHV-infected DBT cells, which express the MHV receptor CEACAM1 (MHVR), to BHK cells, which are devoid of the receptor, by intercellular membrane fusion (MHVR-independent fusion). This mode of infection is a property of wild-type (wt) JHMV cl-2 virus but is not seen in cultures infected with the mutant virus JHMV srr7. In this study, we show that soluble MHVR (soMHVR) potentiates MHVR-independent fusion in JHMV srr7-infected cultures. Thus, in the presence of soMHVR, JHMV srr7-infected DBT cells overlaid onto BHK cells induce BHK cell syncytia and the spread of JHMV srr7 infection. This does not occur in the absence of soMHVR. soMHVR also enhanced wt virus MHVR-independent fusion. These effects were dependent on the concentration of soMHVR in the culture and were specifically blocked by the anti-MHVR monoclonal antibody CC1. Together with these observations, direct binding of soMHVR to the virus spike (S) glycoprotein as revealed by coimmunoprecipitation demonstrated that the effect is mediated by the binding of soMHVR to the S protein. Furthermore, fusion of BHK cells expressing the JHMV srr7 S protein was also induced by soMHVR. These results indicated that the binding of soMHVR to the S protein expressed on the DBT cell surface potentiates the fusion of MHV-infected DBT cells with nonpermissive BHK cells. We conclude that the binding of soMHVR to the S protein converts the S protein to a fusion-active form competent to mediate cell-cell fusion, in a fashion similar to the fusion of virus and cell membranes.

scholarly journals A Major Determinant for Membrane Protein Interaction Localizes to the Carboxy-Terminal Domain of the Mouse Coronavirus Nucleocapsid Protein

2005 ◽  
Vol 79 (21) ◽  
pp. 13285-13297 ◽  
Author(s):  
Kelley R. Hurst ◽  
Lili Kuo ◽  
Cheri A. Koetzner ◽  
Rong Ye ◽  
Bilan Hsue ◽  
...  
Keyword(s):  
Viral Envelope ◽  
M Protein ◽  
N Protein ◽  
Amino Terminal ◽  
Terminal Domain ◽  
Dominant Negative Mutation ◽  
Carboxy Terminal Domain ◽  
Domain 3 ◽  
Positive Strand Rna ◽  
Carboxy Terminal

ABSTRACT The two major constituents of coronavirus virions are the membrane (M) and nucleocapsid (N) proteins. The M protein is anchored in the viral envelope by three transmembrane segments flanked by a short amino-terminal ectodomain and a large carboxy-terminal endodomain. The M endodomain interacts with the viral nucleocapsid, which consists of the positive-strand RNA genome helically encapsidated by N protein monomers. In previous work with the coronavirus mouse hepatitis virus (MHV), a highly defective M protein mutant, MΔ2, was constructed. This mutant contained a 2-amino-acid carboxy-terminal truncation of the M protein. Analysis of second-site revertants of MΔ2 revealed mutations in the carboxy-terminal region of the N protein that compensated for the defect in the M protein. To seek further genetic evidence corroborating this interaction, we generated a comprehensive set of clustered charged-to-alanine mutants in the carboxy-terminal domain 3 of N protein. One of these mutants, CCA4, had a highly defective phenotype similar to that of MΔ2. Transfer of the CCA4 mutation into a partially diploid MHV genome showed that CCA4 was a loss-of-function mutation rather than a dominant-negative mutation. Analysis of multiple second-site revertants of CCA4 revealed mutations in both the M protein and the N protein that could compensate for the original lesion in N. These data more precisely define the region of the N protein that interacts with the M protein. Further, we found that fusion of domain 3 of the N protein to the carboxy terminus of a heterologous protein caused it to be incorporated into MHV virions.

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