scholarly journals Sequences in the Cytoplasmic Tail of the Gibbon Ape Leukemia Virus Envelope Protein That Prevent Its Incorporation into Lentivirus Vectors

2001 ◽  
Vol 75 (9) ◽  
pp. 4129-4138 ◽  
Author(s):  
Ilias Christodoulopoulos ◽  
Paula M. Cannon
Keyword(s):  
Leukemia Virus ◽  
Cytoplasmic Tail ◽  
Viral Fusion ◽  
Virus Envelope ◽  
Peptide Cleavage ◽  
Long Range Interactions ◽  
Virus Envelope Protein ◽  
Lentivirus Vectors ◽  
Membrane Spanning ◽  
Gibbon Ape Leukemia Virus

ABSTRACT Pseudotyping retrovirus and lentivirus vectors with different viral fusion proteins is a useful strategy to alter the host range of the vectors. Although lentivirus vectors are efficiently pseudotyped by Env proteins from several different subtypes of murine leukemia virus (MuLV), the related protein from gibbon ape leukemia virus (GaLV) does not form functional pseudotypes. We have determined that this arises because of an inability of GaLV Env to be incorporated into lentivirus vector particles. By exploiting the homology between the GaLV and MuLV Env proteins, we have mapped the determinants of incompatibility in the GaLV Env. Three modifications that allowed GaLV Env to pseudotype human immunodeficiency virus type 1 particles were identified: removal of the R peptide (C-terminal half of the cytoplasmic domain), replacement of the whole cytoplasmic tail with the corresponding MuLV region, and mutation of two residues upstream of the R peptide cleavage site. In addition, we have previously proposed that removal of the R peptide from MuLV Env proteins enhances their fusogenicity by transmitting a conformational change to the ectodomain of the protein (Y. Zhao et al., J. Virol. 72:5392–5398, 1998). Our analysis of chimeric MuLV/GaLV Env proteins provides further evidence in support of this model and suggests that proper Env function involves both interactions within the cytoplasmic tail and more long-range interactions between the cytoplasmic tail, the membrane-spanning region, and the ectodomain of the protein.

scholarly journals Cytoplasmic Tail of Moloney Murine Leukemia Virus Envelope Protein Influences the Conformation of the Extracellular Domain: Implications for Mechanism of Action of the R Peptide

2003 ◽  
Vol 77 (2) ◽  
pp. 1281-1291 ◽  
Author(s):  
Hector C. Aguilar ◽  
W. French Anderson ◽  
Paula M. Cannon
Keyword(s):  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Cytoplasmic Tail ◽  
Moloney Murine Leukemia Virus ◽  
Virus Envelope ◽  
Peptide Cleavage ◽  
Virus Envelope Protein ◽  
Env Protein ◽  
Membrane Spanning ◽  
Murine Leukemia

ABSTRACT The envelope (Env) protein of Moloney murine leukemia virus (MoMuLV) is a homotrimeric complex whose monomers consist of linked surface (SU) and transmembrane (TM) proteins cleaved from a precursor protein by a cellular protease. In addition, a significant fraction of virion-associated TM is further processed by the viral protease to remove the C-terminal 16 amino acids of the cytoplasmic domain, the R peptide. This cleavage greatly enhances the fusogenicity of the protein and is necessary for the formation of a fully functional Env protein complex. We have previously proposed that R peptide cleavage enhances fusogenicity by altering the conformation of the ectodomain of the protein (Y. Zhao et al., J. Virol. 72:5392-5398, 1998). Using a series of truncation and point mutants of MoMuLV Env, we now provide direct biochemical and immunological evidence that the cytoplasmic tail and the membrane-spanning region of Env can influence the overall structure of the ectodomain of the protein and alter the strength of the SU-TM interaction. The R-peptide-truncated form of the protein, in particular, exhibits a markedly different conformation than the full-length protein.

scholarly journals Vpu Downmodulates Two Distinct Targets, Tetherin and Gibbon Ape Leukemia Virus Envelope, through Shared Features in the Vpu Cytoplasmic Tail

PLoS ONE ◽  
2012 ◽  
Vol 7 (12) ◽  
pp. e51741 ◽  
Author(s):  
Tiffany M. Lucas ◽  
Sanath K. Janaka ◽  
Edward B. Stephens ◽  
Marc C. Johnson
Keyword(s):  
Leukemia Virus ◽  
Cytoplasmic Tail ◽  
Virus Envelope ◽  
Gibbon Ape Leukemia Virus

scholarly journals Pseudotyping Incompatibility between HIV-1 and Gibbon Ape Leukemia Virus Env Is Modulated by Vpu

2009 ◽  
Vol 84 (6) ◽  
pp. 2666-2674 ◽  
Author(s):  
Tiffany M. Lucas ◽  
Terri D. Lyddon ◽  
Paula M. Cannon ◽  
Marc C. Johnson
Keyword(s):  
Leukemia Virus ◽  
Cytoplasmic Tail ◽  
Viral Particles ◽  
Immunodeficiency Virus ◽  
Env Protein ◽  
Membrane Spanning ◽  
Gibbon Ape Leukemia Virus ◽  
Hiv 1 ◽  
Murine Leukemia

ABSTRACT The Env protein from gibbon ape leukemia virus (GaLV) has been shown to be incompatible with human immunodeficiency virus type 1 (HIV-1) in the production of infectious pseudotyped particles. This incompatibility has been mapped to the C-terminal cytoplasmic tail of GaLV Env. Surprisingly, we found that the HIV-1 accessory protein Vpu modulates this incompatibility. The infectivity of HIV-1 pseudotyped with murine leukemia virus (MLV) Env was not affected by Vpu. However, the infectivity of HIV-1 pseudotyped with an MLV Env with the cytoplasmic tail from GaLV Env (MLV/GaLV Env) was restricted 50- to 100-fold by Vpu. A Vpu mutant containing a scrambled membrane-spanning domain, VpuRD, was still able to restrict MLV/GaLV Env, but mutation of the serine residues at positions 52 and 56 completely alleviated the restriction. Loss of infectivity appeared to be caused by reduced MLV/GaLV Env incorporation into viral particles. The mechanism of this downmodulation appears to be distinct from Vpu-mediated CD4 downmodulation because Vpu-expressing cells that failed to produce infectious HIV-1 particles nonetheless continued to display robust surface MLV/GaLV Env expression. In addition, if MLV and HIV-1 were simultaneously introduced into the same cells, only the HIV-1 particle infectivity was restricted by Vpu. Collectively, these data suggest that Vpu modulates the cellular distribution of MLV/GaLV Env, preventing its recruitment to HIV-1 budding sites.

scholarly journals Retrovirus Glycoprotein Functionality Requires Proper Alignment of the Ectodomain and the Membrane-Proximal Cytoplasmic Tail

2013 ◽  
Vol 87 (23) ◽  
pp. 12805-12813 ◽  
Author(s):  
Sanath Kumar Janaka ◽  
Devon A. Gregory ◽  
Marc C. Johnson
Keyword(s):  
Leukemia Virus ◽  
Coiled Coil ◽  
Cytoplasmic Tail ◽  
Wild Type ◽  
Virus Envelope ◽  
Viral Glycoproteins ◽  
Similar Phenotype ◽  
Membrane Spanning ◽  
Hiv 1 ◽  
Murine Leukemia

Nonnative viral glycoproteins, including Friend murine leukemia virus envelope (F-MLV Env) are actively recruited to HIV-1 assembly sites by an unknown mechanism. Because interactions with the lipid microenvironment at budding sites could contribute to recruitment, we examined the contribution of the hydrophobicity of the F-MLV Env membrane-spanning domain (MSD) to its incorporation into HIV-1 particles. A series of F-MLV Env mutants that added or deleted one, two, or three leucines in the MSD were constructed. All six mutants retained the ability to be incorporated into HIV-1 particles, but the −1L, −2L, −3L, +1L, and +2L mutants were not capable of producing infectious particles. Surprisingly, the +3L Env glycoprotein was able to produce infectious particles and was constitutively fusogenic. However, when the cytoplasmic tail domains (CTDs) in the Env constructs were deleted, all six of the MSD mutants were able to produce infectious particles. Further mutational analyses revealed that the first 10 amino acids of the CTD is a critical regulator of infectivity. A similar phenotype was observed in HIV-1 Env upon addition of leucines in the MSD, with +1 and +2 leucine mutations greatly reducing Env activity, but +3 leucine mutations behaving similar to the wild type. Unlike F-MLV Env (+1L and +2L), HIV-1 Env (+1L and +2L) infectivity was not restored by deletion of the CTD. We hypothesize that the CTD forms a coiled-coil that disrupts the protein's functionality if it is not in phase with the trimer interface of the ectodomain.

scholarly journals The Role of the Membrane-spanning Domain Sequence in Glycoprotein-mediated Membrane Fusion

1999 ◽  
Vol 10 (9) ◽  
pp. 2803-2815 ◽  
Author(s):  
Gwen M. Taylor ◽  
David Avram Sanders
Keyword(s):  
Membrane Fusion ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Envelope Proteins ◽  
Viral Fusion ◽  
Virus Envelope ◽  
Membrane Spanning ◽  
Membrane Spanning Domains ◽  
Murine Leukemia

The role of glycoprotein membrane-spanning domains in the process of membrane fusion is poorly understood. It has been demonstrated that replacing all or part of the membrane-spanning domain of a viral fusion protein with sequences that encode signals for glycosylphosphatidylinositol linkage attachment abrogates membrane fusion activity. It has been suggested, however, that the actual amino acid sequence of the membrane-spanning domain is not critical for the activity of viral fusion proteins. We have examined the function of Moloney murine leukemia virus envelope proteins with substitutions in the membrane-spanning domain. Envelope proteins bearing substitutions for proline 617 are processed and incorporated into virus particles normally and bind to the viral receptor. However, they possess greatly reduced or undetectable capacities for the promotion of membrane fusion and infectious virus particle formation. Our results imply a direct role for the residues in the membrane-spanning domain of the murine leukemia virus envelope protein in membrane fusion and its regulation. They also support the thesis that membrane-spanning domains possess a sequence-dependent function in other protein-mediated membrane fusion events.

scholarly journals Sequential activation of the three protomers in the Moloney murine leukemia virus Env

2017 ◽  
Vol 114 (10) ◽  
pp. 2723-2728 ◽  
Author(s):  
Mathilda Sjöberg ◽  
Robin Löving ◽  
Birgitta Lindqvist ◽  
Henrik Garoff
Keyword(s):  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Moloney Murine Leukemia Virus ◽  
Virus Envelope ◽  
Sequential Activation ◽  
Virus Envelope Protein ◽  
Membrane Fusion Proteins ◽  
Viral Membrane Fusion ◽  
Murine Leukemia

Viral membrane fusion proteins of class I are trimers in which the protomeric unit is a complex of a surface subunit (SU) and a fusion active transmembrane subunit (TM). Here we have studied how the protomeric units of Moloney murine leukemia virus envelope protein (Env) are activated in relation to each other, sequentially or simultaneously. We followed the isomerization of the SU-TM disulfide and subsequent SU release from Env with biochemical methods and found that this early activation step occurred sequentially in the three protomers, generating two asymmetric oligomer intermediates according to the scheme (SU-TM)3→ (SU-TM)2TM → (SU-TM)TM2→ TM3. This was the case both when activation was triggered in vitro by depleting stabilizing Ca2+from solubilized Env and when viral Env was receptor triggered on rat XC cells. In the latter case, the activation reaction was too fast for direct observation of the intermediates, but they could be caught by alkylation of the isomerization active thiol.

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