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Evidence that Vpu modulates HIV-1 Gag-envelope interaction towards envelope incorporation and infectivity in a cell
Archana Gautam1, Jayanta Bhattacharya
1Department of Molecular Virology, National AIDS Research Institute, Bhosari, Pune, India.
Abstract:
The HIV-1 Vpu is required for efficient virus particle release from the plasma membrane and intracellular CD4 degradation in infected cells. In the present study, we found that the loss of virus infectivity as a result of envelope (Env) incorporation defect caused by a Gag matrix (MA) mutation (L30E) was significantly alleviated by introducing a start codon mutation in vpu. Inactivation of Vpu partially restored the Env incorporation defect imposed by L30E substitution in MA. This effect was found to be comparable in cell types such as 293T, HeLa, NP2 and GHOST as well as in peripheral blood mononuclear cells (PBMC) and monocyte-derived macrophages (MDM). However, in HeLa cells BST-2 knockdown was found to further alleviate the effect of Vpu inactivation on infectivity of L30E mutant. Our data demonstrated that the impaired infectivity of virus particles due to Env incorporation defect caused by MA mutation was modulated by start codon mutation in Vpu.
Insights
A mutation in the HIV-1 Vpu protein partially restored virus infectivity by correcting envelope incorporation defects caused by a Gag matrix mutation. This finding offers insights into HIV-1 replication and potential therapeutic targets.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- The Human Immunodeficiency Virus type 1 (HIV-1) Vpu protein plays a crucial role in efficient virus release and CD4 receptor downregulation.
- Defects in viral envelope (Env) incorporation can severely impair HIV-1 infectivity.
- Gag matrix (MA) mutations, such as L30E, are known to cause Env incorporation defects.
Purpose of the Study:
- To investigate the impact of Vpu modulation on HIV-1 infectivity when Env incorporation is compromised by a Gag MA mutation.
- To determine if altering Vpu function can rescue the infectivity defects caused by the MA L30E mutation.
Main Methods:
- Introduction of a start codon mutation in the vpu gene to inactivate Vpu function.
- Generation and analysis of HIV-1 variants with specific Gag MA (L30E) and Vpu mutations.
- Assessment of virus infectivity and Env incorporation in various cell lines (293T, HeLa, NP2, GHOST) and primary cells (PBMC, MDM).
- Evaluation of BST-2 (Bone Sialoprotein-2) knockdown effects in HeLa cells.
Main Results:
- A start codon mutation in vpu significantly alleviated the loss of infectivity caused by the Gag MA L30E mutation.
- Inactivation of Vpu partially restored Env incorporation defects associated with the MA L30E substitution.
- This Vpu-mediated rescue effect was observed across multiple cell types, including primary immune cells.
- BST-2 knockdown further enhanced the infectivity of the Vpu-inactivated L30E mutant in HeLa cells.
Conclusions:
- The infectivity of HIV-1 particles with Env incorporation defects, caused by Gag MA mutations, is modulated by Vpu activity.
- Modifying Vpu function, specifically through start codon mutations, can partially rescue virus infectivity despite Env incorporation defects.
- These findings highlight a complex interplay between Gag MA, Vpu, and Env incorporation in HIV-1 replication and suggest Vpu as a potential target for therapeutic intervention.
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