scholarly journals Autographa Californica Multiple Nucleopolyhedrovirus Enters Host Cells via Clathrin-Mediated Endocytosis and Direct Fusion with the Plasma Membrane

Viruses ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 632 ◽  
Author(s):  
Fujun Qin ◽  
Congrui Xu ◽  
Chengfeng Lei ◽  
Jia Hu ◽  
Xiulian Sun
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Autographa Californica ◽  
Host Cells ◽  
Quantitative Electron Microscopy ◽  
Virus Particles ◽  
Multiple Nucleopolyhedrovirus ◽  
Single Virus Tracking ◽  
Autographa Californica Multiple Nucleopolyhedrovirus ◽  
Direct Fusion

The cell entry mechanism of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is not fully understood. Previous studies showed that AcMNPV entered host cells primarily through clathrin-mediated endocytosis, and could efficiently infect cells via fusion with the plasma membrane after a low-pH trigger. However, whether AcMNPV enters cells via these two pathways simultaneously, and the exact manner in which AcMNPV particles are internalized into cells remains unclear. In this study, using single-virus tracking, we observed that AcMNPV particles were first captured by pre-existing clathrin-coated pits (CCP), and were then delivered to early endosomes. Population-based analysis of single-virus tracking and quantitative electron microscopy demonstrated that the majority of particles were captured by CCPs and internalized via invagination. In contrast, a minority of virus particles were not delivered to CCPs, and were internalized through direct fusion with the plasma membrane without invagination. Quantitative electron microscopy also showed that, while inhibition of CCP assembly significantly impaired viral internalization, inhibition of endosomal acidification blocked virus particles out of vesicles. Collectively, these findings demonstrated that approximately 90% of AcMNPV particles entered cells through clathrin-mediated endocytosis and 10% entered via direct fusion with the plasma membrane. This study will lead toward a better understanding of AcMNPV infection.

scholarly journals Ac102 Participates in Nuclear Actin Polymerization by Modulating BV/ODV-C42 Ubiquitination during Autographa californica Multiple Nucleopolyhedrovirus Infection

2018 ◽  
Vol 92 (12) ◽  
Author(s):  
Yongli Zhang ◽  
Xue Hu ◽  
Jingfang Mu ◽  
Yangyang Hu ◽  
Yuan Zhou ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
Proteasomal Degradation ◽  
Autographa Californica ◽  
Host Cells ◽  
Nuclear Accumulation ◽  
Nuclear Actin ◽  
Regulatory Cascade ◽  
Multiple Nucleopolyhedrovirus ◽  
Nucleation Promoting Factor ◽  
Autographa Californica Multiple Nucleopolyhedrovirus

ABSTRACTAs a virus-encoded actin nucleation promoting factor (NPF), P78/83 induces actin polymerization to assist in Autographa californica multiple nucleopolyhedrovirus (AcMNPV) propagation. According to our previous study, although P78/83 actively undergoes ubiquitin-independent proteasomal degradation, AcMNPV encodes budded virus/occlusion derived virus (BV/ODV)-C42 (C42), which allows P78/83 to function as a stable NPF by inhibiting its degradation during viral infection. However, whether there are other viral proteins involved in regulating P78/83-induced actin polymerization has yet to be determined. In this study, we found that Ac102, an essential viral gene product previously reported to play a key role in mediating the nuclear accumulation of actin during AcMNPV infection, is a novel regulator of P78/83-induced actin polymerization. By characterizing anac102knockout bacmid, we demonstrated that Ac102 participates in regulating nuclear actin polymerization as well as the morphogenesis and distribution of capsid structures in the nucleus. These regulatory effects are heavily dependent on an interaction between Ac102 and C42. Further investigation revealed that Ac102 binds to C42 to suppress K48-linked ubiquitination of C42, which decreases C42 proteasomal degradation and consequently allows P78/83 to function as a stable NPF to induce actin polymerization. Thus, Ac102 and C42 form a regulatory cascade to control viral NPF activity, representing a sophisticated mechanism for AcMNPV to orchestrate actin polymerization in both a ubiquitin-dependent and ubiquitin-independent manner.IMPORTANCEActin is one of the most functionally important proteins in eukaryotic cells. Morphologically, actin can be found in two forms: a monomeric form called globular actin (G-actin) and a polymeric form called filamentous actin (F-actin). G-actin can polymerize to form F-actin, and nucleation promoting factor (NPF) is the initiator of this process. Many viral pathogens harness the host actin polymerization machinery to assist in virus propagation. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) induces actin polymerization in host cells. P78/83, a viral NPF, is responsible for this process. Previously, we identified that BV/ODV-C42 (C42) binds to P78/83 and protects it from degradation. In this report, we determined that another viral protein, Ac102, is involved in modulating C42 ubiquitination and, consequently, ensures P78/83 activity as an NPF to initiate actin polymerization. This regulatory cascade represents a novel mechanism by which a virus can harness the cellular actin cytoskeleton to assist in viral propagation.

scholarly journals Autographa californica Multiple Nucleopolyhedrovirus LEF-2 Is a Capsid Protein Required for Amplification but Not Initiation of Viral DNA Replication

2010 ◽  
Vol 84 (10) ◽  
pp. 5015-5024 ◽  
Author(s):  
Carol P. Wu ◽  
Yi-Ju Huang ◽  
Jen-Yeu Wang ◽  
Yueh-Lung Wu ◽  
Huei-Ru Lo ◽  
...  
Keyword(s):  
Dna Replication ◽  
Autographa Californica ◽  
Host Cells ◽  
Growth Curve Analysis ◽  
Late Gene Expression ◽  
Viral Dna ◽  
Viral Dna Replication ◽  
Virus Particles ◽  
Multiple Nucleopolyhedrovirus ◽  
Infected Cells

ABSTRACT The late expression factor 2 gene (lef-2) of baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV) has been identified as one of the factors essential for origin-dependent DNA replication in transient expression assays and has been shown to be involved in late/very late gene expression. To study the function of lef-2 in the life cycle of AcMNPV, lef-2 knockout and repair bacmids were generated by homologous recombination in Escherichia coli. Growth curve analysis showed that lef-2 was essential for virus production. Interestingly, a DNA replication assay indicated that lef-2 is not required for the initiation of viral DNA replication and that, rather, it is required for the amplification of DNA replication. lef-2 is also required for the expression of late and very late genes, as the expression of these genes was abolished by lef-2 deletion. Temporal and spatial distributions of LEF-2 protein in infected cells were also analyzed, and the data showed that LEF-2 protein was localized to the virogenic stroma in the nuclei of the infected cells. Analysis of purified virus particles revealed that LEF-2 is a viral protein component of both budded and occlusion-derived virions, predominantly in the nucleocapsids of the virus particles. This observation suggests that LEF-2 may be required immediately after virus entry into host cells for efficient viral DNA replication.

Systematic analysis of nuclear localization of Autographa californica multiple nucleopolyhedrovirus proteins

2021 ◽  
Author(s):  
Lihong He ◽  
Wei Shao ◽  
Jiang Li ◽  
Fei Deng ◽  
Hualin Wang ◽  
...  
Keyword(s):  
Virus Infection ◽  
Transient Expression ◽  
Nuclear Localization ◽  
Protein Localization ◽  
Viral Proteins ◽  
Autographa Californica ◽  
Host Cells ◽  
Genome Replication ◽  
Multiple Nucleopolyhedrovirus ◽  
Autographa Californica Multiple Nucleopolyhedrovirus

Baculoviruses are large DNA viruses that replicate within the nucleus of infected host cells. Therefore, many viral proteins must gain access to the nucleus for efficient viral genome replication, gene transcription and virion assembly. To date, the global protein localization pattern of baculoviral proteins is unknown. In this study, we systematically analysed the nuclear localization of 154 ORFs encoded by the prototypic baculovirus, Autographa californica multiple nucleopolyhedrovirus (AcMNPV), either during transient expression or with super-infection of the virus. By transient expression of vectors containing egfp-fused ORFs, we found that in the absence of virus infection, 25 viral proteins were localized in the nucleus. Most of these, which we called ‘auto-nuclear localization’ proteins, are related to virus replication, transcription or virion structure, and 20 of them contain predicted classical nuclear localization signal. Upon virus infection, 11 proteins, which originally localized in the cytoplasm or both cytoplasm and nucleus in the transfection assays, were completely translocated into the nucleus, suggesting that their nuclear import is facilitated by other viral or host proteins. Further co-transfection experiments identified that four of the 11 proteins, including P143, P33, AC73 and AC114, were imported into the nucleus with the assistance of the auto-nuclear localization proteins LEF-3 (for P143), TLP (for P33) and VP80 (for both AC73 and AC114). This study presents the first global nuclear localization profile of AcMNPV proteins and provides useful information for further elucidation of the mechanisms of baculovirus nuclear entry and gene functions.

scholarly journals Immunofluorescence and electron microscopy of the cytoplasmic surface of the human erythrocyte membrane and its interaction with Sendai virus.

1979 ◽  
Vol 83 (2) ◽  
pp. 338-347 ◽  
Author(s):  
M Büechi ◽  
T Bächi
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Plasma Membranes ◽  
Sendai Virus ◽  
Light And Electron Microscopy ◽  
Distal Portion ◽  
Double Labeling ◽  
Virus Particles ◽  
Viral Antigens ◽  
Cytoplasmic Surface

A method was developed for directly observing the inner surfaces of plasma membranes by light and electron microscopy. Human erythrocytes were attached to cover slips (glass or mica) treated with aminopropylsilane and glutaraldehyde, and then disrupted by direct application of a jet of buffer, which removed the distal portion of the cells, thus exposing the cytoplasmic surface (PS) of the flattened membranes. Antispectrin antibodies and Sendai virus particles were employed as sensitive markers for, respectively, the PS and the external surface (ES) of the membrane; their localization by immunofluorescence or electron microscopy demonstrated that the major asymmetrical features of the plasma membrane were preserved. The fusion of Sendai virus particles with cells was investigated using double-labeling immunofluorescence techniques. Virus adsorbed to the ES of cells at 4 degrees C was not accessible to fluorescein-labeled antibodies applied from the PS side. After incubation at 37 degrees C, viral antigens could be detected at the PS. These antigens, however, remained localized and did not diffuse from the site of attachment, as is usually seen in viral antigens accessible on the ES. They may therefore represent internal viral antigens not incorporated into the plasma membrane as a result of virus-cell fusion.

The Autographa californica multiple nucleopolyhedrovirus ac110 gene encodes a new per os infectivity factor

2016 ◽  
Vol 221 ◽  
pp. 30-37 ◽  
Author(s):  
Jiantao Liu ◽  
Leyuan Zhu ◽  
Shan Zhang ◽  
Zihao Deng ◽  
Zhihong Huang ◽  
...  
Keyword(s):  
Autographa Californica ◽  
Multiple Nucleopolyhedrovirus ◽  
Autographa Californica Multiple Nucleopolyhedrovirus
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