scholarly journals The F-Like Protein Ac23 Enhances the Infectivity of the Budded Virus of gp64-Null Autographa californica Multinucleocapsid Nucleopolyhedrovirus Pseudotyped with Baculovirus Envelope Fusion Protein F

2008 ◽  
Vol 82 (19) ◽  
pp. 9800-9804 ◽  
Author(s):  
Manli Wang ◽  
Ying Tan ◽  
Feifei Yin ◽  
Fei Deng ◽  
Just M. Vlak ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Fusion Proteins ◽  
Spodoptera Exigua ◽  
Autographa Californica ◽  
Pseudotyped Virus ◽  
F Protein ◽  
Group I ◽  
Protein F ◽  
Budded Virus ◽  
Functional Envelope

ABSTRACT The GP64 and F proteins were previously identified as the sole functional envelope fusion proteins in Baculoviridae. F-like proteins, present only in group I nucleopolyhedroviruses (NPVs), are remnant, nonfunctional F proteins. In this report, we describe the effect of the presence or absence of the F-like protein Ac23 in a gp64-null Autographa californica multinucleocapsid NPV pseudotyped with the F protein from Spodoptera exigua multicapsid NPV (SeF). We found that the presence of Ac23 elevates the infectivity of the pseudotyped virus. This is in contrast to the results of Lung et al. (J. Virol. 76:5729-5736, 2002), who found no such effect. The possible reasons for the differing results are discussed.

scholarly journals GP64 of group I nucleopolyhedroviruses cannot readily rescue infectivity of group II f-null nucleopolyhedroviruses

2008 ◽  
Vol 89 (2) ◽  
pp. 424-431 ◽  
Author(s):  
Marcel Westenberg ◽  
Just M. Vlak
Keyword(s):  
Fusion Protein ◽  
Selective Advantage ◽  
Autographa Californica ◽  
Viral Attachment ◽  
F Protein ◽  
Group I ◽  
The Family ◽  
Protein Group ◽  
Group Ii ◽  
Budded Virus

The genus Nucleopolyhedrovirus (NPV) of the family Baculoviridae can be subdivided phylogenetically into two groups. The same division can be made on the basis of their budded virus (BV) envelope fusion protein. Group I NPVs are characterized by the presence of a GP64-like major envelope fusion protein, which is involved in viral attachment and the fusion of virus and cell membrane, and is required for budding of progeny nucleocapsids. Group II NPVs have an envelope fusion protein unrelated to GP64, named F. In contrast to GP64, F proteins are found in all baculoviruses, but they are not functional as envelope fusion proteins in group I NPVs. Autographa californica multiple NPV (AcMNPV) lacking GP64 can be pseudotyped by the F protein of Spodoptera exigua multiple NPV (SeMNPV), suggesting that F proteins are functionally analogous to GP64. GP64 homologues are thought to have been acquired by group I NPVs during evolution, thereby giving these viruses a selective advantage and obviating the need for a functional F protein. To address this supposition experimentally, attempts were made to pseudotype a group II NPV, SeMNPV, with GP64. Transfection of an f-null SeMNPV bacmid into Se301 cells did not result in the production of infectious BVs. This defect was rescued by insertion of SeMNPV f, but not by insertion of AcMNPV gp64. This suggests that the functional analogy between GP64 and F is not readily reciprocal and that F proteins from group II NPVs may provide additional functions in BV formation that are lacking in the GP64 type of fusion protein.

scholarly journals Conserved Leucines in N-Terminal Heptad Repeat HR1 of Envelope Fusion Protein F of Group II Nucleopolyhedroviruses Are Important for Correct Processing and Essential for Fusogenicity

2007 ◽  
Vol 82 (5) ◽  
pp. 2437-2447 ◽  
Author(s):  
Gang Long ◽  
Xiaoyu Pan ◽  
Just M. Vlak
Keyword(s):  
Fusion Protein ◽  
Fusion Proteins ◽  
Leucine Zipper ◽  
Fusion Peptide ◽  
Class I ◽  
Heptad Repeat ◽  
Viral Fusion ◽  
F Protein ◽  
Viral Fusion Proteins ◽  
Budded Virus

ABSTRACT The heptad repeat (HR), a conserved structural motif of class I viral fusion proteins, is responsible for the formation of a six-helix bundle structure during the envelope fusion process. The insect baculovirus F protein is a newly found budded virus envelope fusion protein which possesses common features to class I fusion proteins, such as proteolytic cleavage and the presence of an N-terminal open fusion peptide and multiple HR domains on the transmembrane subunit F1. Similar to many vertebrate viral fusion proteins, a conserved leucine zipper motif is predicted in this HR region proximal to the fusion peptide in baculovirus F proteins. To facilitate our understanding of the functional role of this leucine zipper-like HR1 domain in baculovirus F protein synthesis, processing, and viral infectivity, key leucine residues (Leu209, Leu216, and Leu223) were replaced by alanine (A) or arginine (R), respectively. By using Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) as a pseudotype expression system, we demonstrated that all mutant F proteins incorporated into budded virus, indicating that leucine substitutions did not affect intercellular trafficking of F. Furin-like protease cleavage was not affected by any of the leucine substitutions; however, the disulfide bridging and N-linked glycosylation patterns were partly altered. Single substitutions in HR1 showed that the three leucine residues were critical for F fusogenicity and the rescue of AcMNPV infectivity. Our results support the view that the leucine zipper-like HR1 domain is important to safeguard the proper folding, glycosylation, and fusogenicity of baculovirus F proteins.

scholarly journals Ac23, an Envelope Fusion Protein Homolog in the Baculovirus Autographa californica Multicapsid Nucleopolyhedrovirus, Is a Viral Pathogenicity Factor

2003 ◽  
Vol 77 (1) ◽  
pp. 328-339 ◽  
Author(s):  
Oliver Y. Lung ◽  
Marilyn Cruz-Alvarez ◽  
Gary W. Blissard
Keyword(s):  
Fusion Protein ◽  
Viral Entry ◽  
Fusion Proteins ◽  
Autographa Californica ◽  
Viral Envelope ◽  
Evolutionary Divergence ◽  
Pathogenicity Factor ◽  
Group I ◽  
Group Ii ◽  
Contrast Group

ABSTRACT Viral envelope fusion proteins are important structural proteins that mediate viral entry and may affect or determine the host range of a virus. The acquisition, exchange, and evolution of such envelope proteins may dramatically affect the success and evolutionary divergence of viruses. In the family Baculoviridae, two very different envelope fusion proteins have been identified. Budded virions of group I nucleopolyhedroviruses (NPVs) such as the Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), contain the essential GP64 envelope fusion protein. In contrast group II NPVs and granuloviruses have no gp64 gene but instead encode a different envelope protein called F. F proteins from group II NPVs can functionally substitute for GP64 in gp64null AcMNPV viruses, indicating that GP64 and these F proteins serve a similar functional role. Interestingly, AcMNPV (and other gp64-containing group I NPVs) also contain an F gene homolog (Ac23) but the AcMNPV F homolog cannot compensate for the loss of gp64. In the present study, we show that Ac23 is expressed and is found in budded virions. To examine the function of F protein homologs from the gp64-containing baculoviruses, we generated an Ac23null AcMNPV genome by homologous recombination in E. coli. We found that Ac23 was not required for viral replication or pathogenesis in cell culture or infected animals. However, Ac23 accelerated the mortality of infected insect hosts by approximately 28% or 26 h. Thus, Ac23 represents an important viral pathogenicity factor in larvae infected with AcMNPV.

scholarly journals Sequence and organization of the Spodoptera exigua multicapsid nucleopolyhedrovirus genome

1999 ◽  
Vol 80 (12) ◽  
pp. 3289-3304 ◽  
Author(s):  
Wilfred F. J. IJkel ◽  
Elisabeth A. van Strien ◽  
Jacobus G. M. Heldens ◽  
René Broer ◽  
Douwe Zuidema ◽  
...  
Keyword(s):  
Spodoptera Exigua ◽  
Autographa Californica ◽  
Recent Common Ancestor ◽  
Computer Assisted ◽  
Glycoprotein Gene ◽  
Orgyia Pseudotsugata ◽  
Group I ◽  
Group Ii ◽  
Budded Virus ◽  
Assisted Analysis

The nucleotide sequence of the DNA genome of Spodoptera exigua multicapsid nucleopolyhedrovirus (SeMNPV), a group II NPV, was determined and analysed. The genome contains 135611 bp and has a G+C content of 44 mol%. Computer-assisted analysis revealed 139 ORFs of 150 nucleotides or larger; 103 have homologues in Autographa californica MNPV (AcMNPV) and a further 16 have homologues in other baculoviruses. Twenty ORFs are unique to SeMNPV. Major differences in SeMNPV gene content and arrangement were found compared with the group I NPVs AcMNPV, Bombyx mori (Bm) NPV and Orgyia pseudotsugata (Op) MNPV and the group II NPV Lymantria dispar (Ld) MNPV. Eighty-five ORFs were conserved among all five baculoviruses and are considered as candidate core baculovirus genes. Two putative p26 and odv-e66 homologues were identified in SeMNPV, each of which appeared to have been acquired independently and not by gene duplication. The SeMNPV genome lacks homologues of the major budded virus glycoprotein gene gp64, the immediate-early transactivator ie-2 and bro (baculovirus repeat ORF) genes that are found in AcMNPV, BmNPV, OpMNPV and LdMNPV. Gene parity analysis of baculovirus genomes suggests that SeMNPV and LdMNPV have a recent common ancestor and that they are more distantly related to the group I baculoviruses AcMNPV, BmNPV and OpMNPV. The orientation of the SeMNPV genome is reversed compared with the genomes of AcMNPV, BmNPV, OpMNPV and LdMNPV. However, the gene order in the ‘central’ part of baculovirus genomes is highly conserved and appears to be a key feature in the alignment of baculovirus genomes.

scholarly journals Baculovirus envelope fusion proteins F and GP64 exploit distinct receptors to gain entry into cultured insect cells

2007 ◽  
Vol 88 (12) ◽  
pp. 3302-3306 ◽  
Author(s):  
Marcel Westenberg ◽  
Peter Uijtdewilligen ◽  
Just M. Vlak
Keyword(s):  
Fusion Proteins ◽  
Mammalian Cells ◽  
Structural Similarity ◽  
Autographa Californica ◽  
Viral Fusion ◽  
Fixed Amount ◽  
Group I ◽  
Protein Receptors ◽  
Viral Fusion Proteins ◽  
Budded Virus

Group II nucleopolyhedroviruses (NPVs), e.g. Helicoverpa armigera (Hear) NPV and Spodoptera exigua (Se) MNPV (multiple NPV), lack a GP64-like protein that is present in group I NPVs, e.g. Autographa californica (Ac)MNPV, but have an unrelated envelope fusion protein named F. Three AcMNPV viruses were constructed by introducing AcMNPV gp64, HearNPV f or SeMNPV f genes, respectively, into a gp64-negative AcMNPV bacmid. Sf21 cells were incubated with different amounts of inactivated budded virus to occupy receptors and were subsequently infected with a fixed amount of infectious virus to compete for attachment. The results suggest that GP64 and F act on their own and use different receptors, while the two different F proteins exploit the same receptor. Additionally, gp64-null AcMNPV pseudotyped with baculovirus F was, in contrast to GP64, unable to transduce mammalian cells, indicating that mammalian cells do not possess baculovirus F protein receptors despite the structural similarity of baculovirus F to vertebrate viral fusion proteins.

scholarly journals Incorporation of GP64 into Helicoverpa armigera nucleopolyhedrovirus enhances virus infectivity in vivo and in vitro

2012 ◽  
Vol 93 (12) ◽  
pp. 2705-2711 ◽  
Author(s):  
Shu Shen ◽  
Yinyin Gan ◽  
Manli Wang ◽  
Zhihong Hu ◽  
Hualin Wang ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Helicoverpa Armigera ◽  
Fusion Proteins ◽  
Virus Infectivity ◽  
F Protein ◽  
Recombinant Viruses ◽  
Group I ◽  
Helicoverpa Armígera

The envelope fusion proteins of baculoviruses, glycoprotein GP64 from group I nucleopolyhedrovirus (NPV) or the F protein from group II NPV and granulovirus, are essential for baculovirus morphogenesis and infectivity. The F protein is considered the ancestral baculovirus envelope fusion protein, while GP64 is a more recent evolutionary introduction into baculoviruses and exhibits higher fusogenic activity than the F protein. Each of the fusion proteins is required by the respective virus to spread infection within larval tissues. A recombinant Helicoverpa armigera NPV (HearNPV) expressing GP64 from Autographa californica multiple nucleopolyhedrovirus, vHaBac-gp64-egfp, was constructed, which still retained the native F protein, and its infectivity was assayed in vivo and in vitro. Analyses by one-step growth curve to determine viral titre and by quantitative PCR to determine viral DNA copy number showed that vHaBac-gp64-egfp was more infectious in vitro than the control, vHaBac-egfp. The polyhedrin gene (polh) was reintroduced into the recombinant viruses and bioassays showed that vHaBac-gp64-polh accelerated the mortality of infected larvae compared with the vHaBac-egfp-polh control, and the LC50 (median lethal concentration) of vHaBac-gp64-polh was reduced to approximately 20 % of that of vHaBac-egfp-polh. Therefore, incorporation of GP64 into HearNPV budded virions improved virus infectivity both in vivo and in vitro. The construction of this bivalent virus with a more efficient fusion protein could improve the use of baculoviruses in different areas such as gene therapy and biocontrol.

scholarly journals A Betabaculovirus-Encodedgp64Homolog Codes for a Functional Envelope Fusion Protein

2015 ◽  
Vol 90 (3) ◽  
pp. 1668-1672 ◽  
Author(s):  
Daniel M. P. Ardisson-Araújo ◽  
Fernando L. Melo ◽  
Rollie J. Clem ◽  
José L. C. Wolff ◽  
Bergmann M. Ribeiro
Keyword(s):  
Fusion Protein ◽  
Genome Sequence ◽  
Protein Activity ◽  
F Protein ◽  
Diatraea Saccharalis ◽  
Group I ◽  
Functional Envelope

The GP64 envelope fusion protein is a hallmark of group I alphabaculoviruses. However, the Diatraea saccharalis granulovirus genome sequence revealed the first betabaculovirus species harboring agp64homolog (disa118). In this work, we have shown that this homolog encodes a functional envelope fusion protein and could enable the infection and fusogenic abilities of agp64-null prototype baculovirus. Therefore, GP64 may complement or may be in the process of replacing F protein activity in this virus lineage.

scholarly journals A Functional F Analogue of Autographa californica Nucleopolyhedrovirus GP64 from the Agrotis segetum Granulovirus

2008 ◽  
Vol 82 (17) ◽  
pp. 8922-8926 ◽  
Author(s):  
Feifei Yin ◽  
Manli Wang ◽  
Ying Tan ◽  
Fei Deng ◽  
Just M. Vlak ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Membrane Fusion ◽  
Plutella Xylostella ◽  
Syncytium Formation ◽  
Low Ph ◽  
Autographa Californica ◽  
Agrotis Segetum ◽  
Induced Membrane ◽  
F Protein ◽  
Autographa Californica Nucleopolyhedrovirus

ABSTRACT The envelope fusion protein F of Plutella xylostella granulovirus is a computational analogue of the GP64 envelope fusion protein of Autographa californica nucleopolyhedrovirus (AcMNPV). Granulovirus (GV) F proteins were thought to be unable to functionally replace GP64 in the AcMNPV pseudotyping system. In the present study the F protein of Agrotis segetum GV (AgseGV) was identified experimentally as the first functional GP64 analogue from GVs. AgseF can rescue virion propagation and infectivity of gp64-null AcMNPV. The AgseF-pseudotyped AcMNPV also induced syncytium formation as a consequence of low-pH-induced membrane fusion.

scholarly journals Functional Analysis of the Putative Fusion Domain of the Baculovirus Envelope Fusion Protein F

2004 ◽  
Vol 78 (13) ◽  
pp. 6946-6954 ◽  
Author(s):  
Marcel Westenberg ◽  
Frank Veenman ◽  
Els C. Roode ◽  
Rob W. Goldbach ◽  
Just M. Vlak ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Conformational Changes ◽  
Cellular Membrane ◽  
Fusion Peptide ◽  
Single Amino Acid ◽  
Viral Infectivity ◽  
Viral Fusion ◽  
F Protein ◽  
Group I ◽  
N Terminus

ABSTRACT Group II nucleopolyhedroviruses (NPVs), e.g., Spodoptera exigua MNPV, lack a GP64-like protein that is present in group I NPVs but have an unrelated envelope fusion protein named F. In contrast to GP64, the F protein has to be activated by a posttranslational cleavage mechanism to become fusogenic. In several vertebrate viral fusion proteins, the cleavage activation generates a new N terminus which forms the so-called fusion peptide. This fusion peptide inserts in the cellular membrane, thereby facilitating apposition of the viral and cellular membrane upon sequential conformational changes of the fusion protein. A similar peptide has been identified in NPV F proteins at the N terminus of the large membrane-anchored subunit F1. The role of individual amino acids in this putative fusion peptide on viral infectivity and propagation was studied by mutagenesis. Mutant F proteins with single amino acid changes as well as an F protein with a deleted putative fusion peptide were introduced in gp64-null Autographa californica MNPV budded viruses (BVs). None of the mutations analyzed had an major effect on the processing and incorporation of F proteins in the envelope of BVs. Only two mutants, one with a substitution for a hydrophobic residue (F152R) and one with a deleted putative fusion peptide, were completely unable to rescue the gp64-null mutant. Several nonconservative substitutions for other hydrophobic residues and the conserved lysine residue had only an effect on viral infectivity. In contrast to what was expected from vertebrate virus fusion peptides, alanine substitutions for glycines did not show any effect.

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