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Several N-Glycans on the HIV Envelope Glycoprotein gp120 Preferentially Locate Near Disulphide Bridges and Are Required for Efficient Infectivity and Virus Transmission.

Mathys L, Balzarini J - PLoS ONE (2015)

Bottom Line: Such a pronounced co-localization of disulphide bridges and N-glycans was also found for the N-glycans on glycoprotein E1 of the hepatitis C virus (HCV) but not for other heavily glycosylated proteins such as E2 from HCV and the surface GP from Ebola virus.The generated HIV-1NL4.3 mutants were subjected to an array of assays, determining the envelope glycoprotein levels in mutant viral particles, their infectivity and the capture and transmission efficiencies of mutant virus particles by DC-SIGN.In addition, introduction of new N-glycans upstream of several disulphide bridges, at locations where there was a significant absence of N-glycans in a broad variety of virus strains, was found to result in a complete loss of viral infectivity.

View Article: PubMed Central - PubMed

Affiliation: Rega Institute for Medical Research, KU Leuven, Leuven, Belgium.

ABSTRACT
The HIV envelope glycoprotein gp120 contains nine disulphide bridges and is highly glycosylated, carrying on average 24 N-linked glycans. Using a probability calculation, we here demonstrate that there is a co-localization of disulphide bridges and N-linked glycans in HIV-1 gp120, with a predominance of N-linked glycans in close proximity to disulphide bridges, at the C-terminal side of the involved cysteines. Also, N-glycans are frequently found immediately adjacent to disulphide bridges in gp120 at the N-terminal side of the involved cysteines. In contrast, N-glycans at positions close to, but not immediately neighboring disulphide bridges seem to be disfavored at the N-terminal side of the involved cysteines. Such a pronounced co-localization of disulphide bridges and N-glycans was also found for the N-glycans on glycoprotein E1 of the hepatitis C virus (HCV) but not for other heavily glycosylated proteins such as E2 from HCV and the surface GP from Ebola virus. The potential functional role of the presence of N-glycans near disulphide bridges in HIV-1 gp120 was studied using site-directed mutagenesis, either by deleting conserved N-glycans or by inserting new N-glycosylation sites near disulphide bridges. The generated HIV-1NL4.3 mutants were subjected to an array of assays, determining the envelope glycoprotein levels in mutant viral particles, their infectivity and the capture and transmission efficiencies of mutant virus particles by DC-SIGN. Three N-glycans located nearby disulphide bridges were found to be crucial for the preservation of several of these functions of gp120. In addition, introduction of new N-glycans upstream of several disulphide bridges, at locations where there was a significant absence of N-glycans in a broad variety of virus strains, was found to result in a complete loss of viral infectivity. It was shown that the N-glycan environment around well-defined disulphide bridges of gp120 is highly critical to allow efficient viral infection and transmission.

No MeSH data available.


Related in: MedlinePlus

Correlation between the infectivity and transmission efficiency of the gp120 N-glycan deleted mutant virus strains, relative to WT virus.The black dashed line represents a curve where infectivity and transmission would have been equally influenced by the mutations. White quadrant: both transmission and infectivity are decreased. Full grey quadrant: both transmission and infectivity are increased. Quadrant with horizontal striping: transmission efficiency is increased while infectivity is decreased. Quadrant with vertical striping: infectivity is increased while transmission efficiency is decreased.
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pone.0130621.g007: Correlation between the infectivity and transmission efficiency of the gp120 N-glycan deleted mutant virus strains, relative to WT virus.The black dashed line represents a curve where infectivity and transmission would have been equally influenced by the mutations. White quadrant: both transmission and infectivity are decreased. Full grey quadrant: both transmission and infectivity are increased. Quadrant with horizontal striping: transmission efficiency is increased while infectivity is decreased. Quadrant with vertical striping: infectivity is increased while transmission efficiency is decreased.

Mentions: It could be assumed that there would be a close correlation between the effect of gp120 N-glycan deletions on viral infectivity and transmission efficiency, since both processes involve the interaction between gp120 and CD4/CXCR4/CCR5, require conformational changes in gp120 upon interaction with CD4/CXCR4/CCR5 and result in membrane fusion. Whereas the majority of the N-glycan-deleted virus mutants showed a decreased infectivity and a decreased transmission efficiency (N156Q, N197Q, N332Q, N386Q), two virus mutants (N230Q and N295Q) were endowed with both an increased infectivity and transmission potential (Fig 7). Interestingly, it looks like most HIV-1 mutants (i.e. N197, N230Q, N241Q and N386) have consistently a more pronounced deleterious effect on transmission efficiency than on infection efficiency. This difference in efficiency was most pronounced for the mutant gp120 N386Q HIV-1 strain that showed an infection potential ~70% of WT virus, while its transmission potential was only 10% of WT virus (Fig 7).


Several N-Glycans on the HIV Envelope Glycoprotein gp120 Preferentially Locate Near Disulphide Bridges and Are Required for Efficient Infectivity and Virus Transmission.

Mathys L, Balzarini J - PLoS ONE (2015)

Correlation between the infectivity and transmission efficiency of the gp120 N-glycan deleted mutant virus strains, relative to WT virus.The black dashed line represents a curve where infectivity and transmission would have been equally influenced by the mutations. White quadrant: both transmission and infectivity are decreased. Full grey quadrant: both transmission and infectivity are increased. Quadrant with horizontal striping: transmission efficiency is increased while infectivity is decreased. Quadrant with vertical striping: infectivity is increased while transmission efficiency is decreased.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4488071&req=5

pone.0130621.g007: Correlation between the infectivity and transmission efficiency of the gp120 N-glycan deleted mutant virus strains, relative to WT virus.The black dashed line represents a curve where infectivity and transmission would have been equally influenced by the mutations. White quadrant: both transmission and infectivity are decreased. Full grey quadrant: both transmission and infectivity are increased. Quadrant with horizontal striping: transmission efficiency is increased while infectivity is decreased. Quadrant with vertical striping: infectivity is increased while transmission efficiency is decreased.
Mentions: It could be assumed that there would be a close correlation between the effect of gp120 N-glycan deletions on viral infectivity and transmission efficiency, since both processes involve the interaction between gp120 and CD4/CXCR4/CCR5, require conformational changes in gp120 upon interaction with CD4/CXCR4/CCR5 and result in membrane fusion. Whereas the majority of the N-glycan-deleted virus mutants showed a decreased infectivity and a decreased transmission efficiency (N156Q, N197Q, N332Q, N386Q), two virus mutants (N230Q and N295Q) were endowed with both an increased infectivity and transmission potential (Fig 7). Interestingly, it looks like most HIV-1 mutants (i.e. N197, N230Q, N241Q and N386) have consistently a more pronounced deleterious effect on transmission efficiency than on infection efficiency. This difference in efficiency was most pronounced for the mutant gp120 N386Q HIV-1 strain that showed an infection potential ~70% of WT virus, while its transmission potential was only 10% of WT virus (Fig 7).

Bottom Line: Such a pronounced co-localization of disulphide bridges and N-glycans was also found for the N-glycans on glycoprotein E1 of the hepatitis C virus (HCV) but not for other heavily glycosylated proteins such as E2 from HCV and the surface GP from Ebola virus.The generated HIV-1NL4.3 mutants were subjected to an array of assays, determining the envelope glycoprotein levels in mutant viral particles, their infectivity and the capture and transmission efficiencies of mutant virus particles by DC-SIGN.In addition, introduction of new N-glycans upstream of several disulphide bridges, at locations where there was a significant absence of N-glycans in a broad variety of virus strains, was found to result in a complete loss of viral infectivity.

View Article: PubMed Central - PubMed

Affiliation: Rega Institute for Medical Research, KU Leuven, Leuven, Belgium.

ABSTRACT
The HIV envelope glycoprotein gp120 contains nine disulphide bridges and is highly glycosylated, carrying on average 24 N-linked glycans. Using a probability calculation, we here demonstrate that there is a co-localization of disulphide bridges and N-linked glycans in HIV-1 gp120, with a predominance of N-linked glycans in close proximity to disulphide bridges, at the C-terminal side of the involved cysteines. Also, N-glycans are frequently found immediately adjacent to disulphide bridges in gp120 at the N-terminal side of the involved cysteines. In contrast, N-glycans at positions close to, but not immediately neighboring disulphide bridges seem to be disfavored at the N-terminal side of the involved cysteines. Such a pronounced co-localization of disulphide bridges and N-glycans was also found for the N-glycans on glycoprotein E1 of the hepatitis C virus (HCV) but not for other heavily glycosylated proteins such as E2 from HCV and the surface GP from Ebola virus. The potential functional role of the presence of N-glycans near disulphide bridges in HIV-1 gp120 was studied using site-directed mutagenesis, either by deleting conserved N-glycans or by inserting new N-glycosylation sites near disulphide bridges. The generated HIV-1NL4.3 mutants were subjected to an array of assays, determining the envelope glycoprotein levels in mutant viral particles, their infectivity and the capture and transmission efficiencies of mutant virus particles by DC-SIGN. Three N-glycans located nearby disulphide bridges were found to be crucial for the preservation of several of these functions of gp120. In addition, introduction of new N-glycans upstream of several disulphide bridges, at locations where there was a significant absence of N-glycans in a broad variety of virus strains, was found to result in a complete loss of viral infectivity. It was shown that the N-glycan environment around well-defined disulphide bridges of gp120 is highly critical to allow efficient viral infection and transmission.

No MeSH data available.


Related in: MedlinePlus