scholarly journals Transport via Macropinocytic Vesicles Is Crucial for Productive Infection with Bombyx Mori Nucleopolyhedrovirus

Viruses ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 668 ◽  
Author(s):  
Jinshan Huang ◽  
Chenya Li ◽  
Xudong Tang ◽  
Lin Liu ◽  
Wenbin Nan ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Bombyx Mori ◽  
Low Ph ◽  
Host Cells ◽  
Productive Infection ◽  
Bombyx Mori Nucleopolyhedrovirus ◽  
Viral Pathogen ◽  
Essential Condition ◽  
Fluid Uptake ◽  
Entry Mechanism

Bombyx mori nucleopolyhedrovirus (BmNPV) is a serious viral pathogen in the sericulture industry and enters host cells via macropinocytic endocytosis; however, the current understanding of the BmNPV entry mechanism remains limited. To confirm whether direct membrane fusion (DMF) results in productive BmNPV infection, DMF infectivity induced by low pH during BmNPV infection was investigated, and the infectious viral particle was traced using an eGFP-labeled virion. We found that BmNPV infection efficiently induced fluid uptake, which allowed BmNPV to bypass the cell membrane barrier via macropinocytosis. However, DMF induced by a low pH abolished the infection. While low pH is an essential condition for membrane fusion triggering, it is not sufficient for productive BmNPV infection, and DMF results in failure to transport the nucleocapsid into the nucleus. These results indicate that transport via macropinocytic vesicles facilitates BmNPV entry into the nucleus and contribute to our understanding of the BmNPV entry mechanism.

scholarly journals Methyl-Beta-Cyclodextrin-Induced Macropinocytosis Results in Increased Infection of Sf21 Cells by Bombyx Mori Nucleopolyhedrovirus

Viruses ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 937 ◽  
Author(s):  
Huang ◽  
Li ◽  
Fan ◽  
liu ◽  
Boadi ◽  
...  
Keyword(s):  
Bombyx Mori ◽  
Amino Acid Sequence Identity ◽  
Autographa Californica ◽  
Host Cells ◽  
Abortive Infection ◽  
Bombyx Mori Nucleopolyhedrovirus ◽  
Membrane Ruffling ◽  
Beta Cyclodextrin ◽  
Autographa Californica Multiple Nucleopolyhedrovirus ◽  
Entry Mechanism

Bombyx mori nucleopolyhedrovirus (BmNPV) is closely related to Autographa californica multiple nucleopolyhedrovirus (AcMNPV) with over ~93% amino acid sequence identity. However, their host ranges are essentially nonoverlapping. The mechanism of BmNPV entry into host cells is completely different from that of AcMNPV, and whether the entry mechanism difference relates to the host range remains unclear. BmNPV produces an abortive infection in nonhost cells due to virion nuclear transportation failure. Here, we performed a detailed study by increasing BmNPV infection in Sf21 cells with the aid of methyl-beta-cyclodextrin (MβCD). We found that low-concentration MβCD incubation efficiently activates membrane ruffling in Sf21 cells, which mediates the increase in BmNPV infection. Interestingly, MβCD incubation after virion internalization also increases the infection, which suggests that macropinocytosis is involved in BmNPV infection in Sf21 cells after virion internalization. Further study revealed that clathrin-mediated endocytosis (CME) is employed by BmNPV to facilitate entry into Sf21 cells, and chlorpromazine application abolishes BmNPV infection in cells incubated both with and without MβCD. Based on these studies, we show that BmNPV enters Sf21 cells via CME and that parallel induction of macropinocytosis facilitates BmNPV infection in Sf21 cells. This study reveals the mechanism of BmNPV entry into Sf21 cells and provides clues for improving BmNPV infections in nonpermissive cells.

scholarly journals Dynamic Interactions between Bombyx mori Nucleopolyhedrovirus and Its Host Cells Revealed by Transcriptome Analysis

2012 ◽  
Vol 86 (13) ◽  
pp. 7345-7359 ◽  
Author(s):  
J. Xue ◽  
N. Qiao ◽  
W. Zhang ◽  
R.-L. Cheng ◽  
X.-Q. Zhang ◽  
...  
Keyword(s):  
Bombyx Mori ◽  
Transcriptome Analysis ◽  
Host Cells ◽  
Bombyx Mori Nucleopolyhedrovirus ◽  
Dynamic Interactions

scholarly journals Membrane fusion process of Semliki Forest virus. I: Low pH-induced rearrangement in spike protein quaternary structure precedes virus penetration into cells.

1992 ◽  
Vol 116 (2) ◽  
pp. 339-348 ◽  
Author(s):  
J M Wahlberg ◽  
H Garoff
Keyword(s):  
Membrane Protein ◽  
Membrane Fusion ◽  
Semliki Forest Virus ◽  
Quaternary Structure ◽  
Low Ph ◽  
Host Cells ◽  
Protein Oligomerization ◽  
Protein Subunit ◽  
New Host ◽  
E1 Protein

The Semliki Forest virus (SFV) directs the synthesis of a heterodimeric membrane protein complex which is used for virus membrane assembly during budding at the surface of the infected cell, as well as for low pH-induced membrane fusion in the endosomes when particles enter new host cells. Existing evidence suggests that the E1 protein subunit carries the fusion potential of the heterodimer, whereas the E2 subunit, or its intracellular precursor p62, is required for binding to the nucleocapsid. We show here that during virus uptake into acidic endosomes the original E2E1 heterodimer is destabilized and the E1 proteins form new oligomers, presumably homooligomers, with altered E1 structure. This altered structure of E1 is specifically recognized by a monoclonal antibody which can also inhibit penetration of SFV into host cells as well as SFV-mediated cell-cell fusion, thus suggesting that the altered E1 structure is important for the membrane fusion. These results give further support for a membrane protein oligomerization-mediated control mechanism for the membrane fusion potential in alphaviruses.

scholarly journals Endocytosis and a Low-pH Step Are Required for Productive Entry of Equine Infectious Anemia Virus

2005 ◽  
Vol 79 (23) ◽  
pp. 14482-14488 ◽  
Author(s):  
Melinda A. Brindley ◽  
Wendy Maury
Keyword(s):  
Ammonium Chloride ◽  
Equine Infectious Anemia Virus ◽  
Cell Types ◽  
Low Ph ◽  
Host Cells ◽  
Productive Infection ◽  
Tissue Culture Cell ◽  
Lysosomotropic Agents ◽  
Equine Infectious Anemia ◽  
Anemia Virus

ABSTRACT Recently, it has become evident that entry of some retroviruses into host cells is dependent upon a vesicle-localized, low-pH step. The entry mechanism of equine infectious anemia virus (EIAV) has yet to be examined. Here, we demonstrate that wild-type strains of EIAV require a low-pH step for productive entry. Lysosomotropic agents that inhibit the acidification of internal vesicles inhibited productive entry of EIAV. The presence of ammonium chloride (30 mM), monensin (30 μM), or bafilomycin A (50 nM) in the medium dramatically decreased the number of EIAV antigen-positive cells. We found that a low-pH step was required for EIAV infection of tissue culture cell lines as well as primary cells, such as endothelial cells and monocyte-derived macrophages. The ammonium chloride treatment did not reduce virion stability, nor did the treatment prevent virion binding to cells. Consistent with a requirement for a low-pH step, virion infectivity was enhanced more than threefold by brief low-pH treatment following binding of viral particles to permissive cells. A superinfecting variant strain of EIAV, vMA-1c, did not require a low-pH step for productive infection of fibroblasts. However, lysosomotropic agents were inhibitory to vMA-1c infection in the other cell types that vMA-1c infected but did not superinfect, indicating that the entry pathway used by vMA-1c for superinfection abrogates the need for the low-pH step.

scholarly journals Two Cholesterol Recognition Amino Acid Consensus Motifs of GP64 with Uncleaved Signal Peptide Are Required for Bombyx mori Nucleopolyhedrovirus Infection

2021 ◽  
Vol 9 (3) ◽  
Author(s):  
Bifang Hao ◽  
Wenbin Nan ◽  
Ying Xu ◽  
Lin Liu ◽  
Na Liu ◽  
...  
Keyword(s):  
Amino Acid ◽  
Fusion Protein ◽  
Membrane Fusion ◽  
Bombyx Mori ◽  
Signal Peptide ◽  
Bombyx Mori Nucleopolyhedrovirus ◽  
Membrane Fusion Protein ◽  
Consensus Motifs

BmNPV is a severe pathogen that mainly infects silkworms. GP64 is the key membrane fusion protein that mediates BmNPV infection, and some studies have indicated that cholesterol and lipids are involved in BmNPV infection.

scholarly journals E1 Mutants Identify a Critical Region in the Trimer Interface of the Semliki Forest Virus Fusion Protein

2009 ◽  
Vol 83 (21) ◽  
pp. 11298-11306 ◽  
Author(s):  
Catherine Y. Liu ◽  
Margaret Kielian
Keyword(s):  
Membrane Fusion ◽  
Protein Interactions ◽  
Semliki Forest Virus ◽  
Hot Spot ◽  
Fusion Reaction ◽  
Ph Dependence ◽  
Infectious Clone ◽  
Low Ph ◽  
Host Cells ◽  
Target Membrane

ABSTRACT The alphavirus Semliki Forest virus (SFV) uses a membrane fusion reaction to infect host cells. Fusion of the virus and cell membranes is triggered by low pH in the endosome and is mediated by the viral membrane protein E1. During fusion, E1 inserts into the target membrane, trimerizes, and refolds into a hairpin conformation. Formation of the E1 homotrimer is critical to membrane fusion, but the mechanism of trimerization is not understood. The crystal structure of the postfusion E1 trimer shows that an aspartate residue, D188, is positioned in the central core trimer interface. D188 is conserved in all reported alphavirus E1 sequences. We tested the contribution of this amino acid to trimerization and fusion by replacing D188 with alanine (D188A) or lysine (D188K) in an SFV infectious clone. These mutations were predicted to disrupt specific interactions at this position and/or change their pH dependence. Our results indicated that the D188K mutation blocked SFV fusion and infection. At low pH, D188K E1 inserted into target membranes but was trapped as a target membrane-inserted monomer that did not efficiently form the stable core trimer. In contrast, the D188A mutant was infectious, although trimerization and fusion required a lower pH. While there are extensive contacts between E1 subunits in the homotrimer, the D188K mutant identifies an important “hot spot” for protein-protein interactions within the core trimer.

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