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Updated: Aug 8, 2026
Assessment of Immunologically Relevant Dynamic Tertiary Structural Features of the HIV-1 V3 Loop Crown R2 Sequence by ab initio Folding
Published on: September 16, 2010
Mutational analysis of HIV-1 gp160-mediated receptor interference: intracellular complex formation
1Department of Microbiology and Immunology, Jonsson Comprehensive Cancer Center, UCLA School of Medicine 90024-1747, USA.
Insights
Intracellular interactions between CD4 and gp160, crucial for HIV receptor interference, may use different binding sites than cell surface interactions. Mutations affecting surface binding do not always prevent ER complex formation.
Area of Science:
- Virology
- Immunology
- Cell Biology
Background:
- Formation of CD4-gp160 intracellular complexes is key to receptor interference.
- Previous research showed coexpression blocks CD4-gp160 complexes in the ER, preventing cell surface CD4 transport.
Purpose of the Study:
- Investigate specific domains and residues of CD4 and gp160 involved in intracellular complex formation.
- Analyze how mutations affect intracellular binding and CD4 surface expression.
Main Methods:
- Introduced mutations in CD4 and gp160 based on known CD4-gp120 surface interaction sites.
- Utilized a T7-vaccinia virus transient expression system in HeLa cells.
- Analyzed intracellular complex formation and CD4 surface modulation.
Main Results:
- Mutations disrupting cell surface CD4-gp120 binding often prevented ER complex formation.
- However, mutations at gp160 residue W427 did not abolish intracellular CD4 binding.
- Some CD4 mutants also formed intracellular complexes with gp160, reducing surface CD4.
Conclusions:
- Intracellular gp160-CD4 interactions in the ER may differ from cell surface CD4-gp120 binding.
- The cellular environment significantly influences CD4 and HIV-1 envelope glycoprotein interactions.
Abstract:
Formation of CD4-gp160 intracellular complexes represents an important mechanism leading to the induction of receptor interference. Previous studies have demonstrated that cells coexpressing gp160 and CD4 formed complexes of CD4 and gp160 which became blocked within the endoplasmic reticulum (ER), preventing CD4 from reaching the cell surface. In this report we have investigated the domains and residues of CD4 and gp160 involved in intracellular interaction. Accordingly, we have introduced mutations in both CD4 and gp160 at sites previously shown to disrupt CD4-gp120 interactions at the cell surface. Using a T7-vaccinia virus transient expression system, we expressed these gp160 and CD4 mutants in HeLa cells and analyzed their effects on intracellular complex formation and CD4 surface modulation. We observed that a number of gp160 mutants which failed to interact with CD4 at the cell surface also failed to bind and trap CD4 within the ER as expected. However, mutations at a critical residue, W427, did not abrogate intracellular CD4 binding. These gp160 mutants continued to interact with intracellular CD4 and inhibit CD4 transport to the cell surface, although gp120 produced from these mutants did not bind CD4 at the cell surface as expected. A number CD4 mutants also continued to form intracellular complexes with gp160, resulting in the loss of CD4 surface expression. Again, these CD4 mutants did not bind to gp120 at the cell surface, consistent with earlier reports. These results demonstrate that intracellular interactions between gp160 and CD4 in the ER may utilize different contact sites compared to those used during CD4 and gp120 binding at the cell surface. The data provide further evidence that the environment in which CD4 and the HIV-1 envelope glycoprotein interact can have a significant effect on their interaction.
