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Updated: Jun 25, 2026
Imaging of HIV-1 Envelope-induced Virological Synapse and Signaling on Synthetic Lipid Bilayers
Published on: March 8, 2012
Recruitment of HIV-1 envelope occurs subsequent to lipid mixing: a fluorescence microscopic evidence
Miao-Ping Chien1, Chi-Hui Lin, Ding-Kwo Chang
1Institute of Chemistry, Academia Sinica, Taipei, Taiwan 11529, ROC. michelle@chem.sinica.edu.tw
Insights
This study reveals that lipid mixing precedes envelope glycoprotein (Env) recruitment during HIV entry. Env recruitment is inhibited by gp41e, indicating lipid mixing occurs first.
Area of Science:
- Virology
- Cell Biology
- Biophysics
Background:
- HIV entry into target cells involves envelope glycoproteins (gp120/gp41) mediating fusion.
- Previous studies suggested Env recruitment and lipid mixing occur concurrently during HIV fusion.
Purpose of the Study:
- To resolve the temporal sequence of lipid mixing and Env recruitment during HIV-1 entry.
- To investigate the inhibitory mechanism of the gp41 ectodomain fragment (gp41e).
Main Methods:
- Utilized an inhibitory assay monitored by fluorescence microscopy.
- Employed a gp41e fragment to block Env recruitment and assessed its effect on lipid mixing.
Main Results:
- gp41e inhibited Env recruitment but not lipid mixing, indicating lipid mixing precedes Env recruitment.
- Random Env clustering occurred at ~1 minute, while Env recruitment was observed at ~13 minutes.
- A >10-fold temporal discrepancy between clustering and recruitment was identified.
Conclusions:
- Lipid mixing precedes Env recruitment during HIV-1 cell entry.
- Productive fusion requires spatio-temporal coordination and directed movement of aggregated Env trimers.
Abstract:
Entry of the human immunodeficiency virus (HIV) into the target cell is initiated by fusion with the cell membrane, mediated through the envelope glycoproteins gp120 and gp41, following engagement to CD4 and the co-receptor. Previous fusion kinetics studies on the HXB2 envelope protein (Env) revealed that Env recruitment occurred at about 13 min concurrent with the lipid mixing. To resolve the temporal sequence of lipid mixing and recruitment, we employed an inhibitory assay monitored by fluorescence microscopy using a gp41 ectodomain (gp41e) fragment, which blocked Env recruitment in stark contrast to the lack of gp41e effect on the lipid mixing. In addition, to demonstrate the mode of action for the inhibition of gp41e, our results strongly suggested that lipid mixing precedes the Env recruitment because lipid mixing can proceed with Env recruitment inhibited by exogeneous gp41e molecules. Importantly, it was found that the random clustering of Env molecules on the membrane surface occurred at approximately 1 minute whereas the Env recruitment was observed at 13 minutes after the attachment of Env-expressing cell to the target cell. This > 10-fold temporal discrepancy highlights that the productive assembly of Env molecules leading to fusion requires spatio-temporal coordination of several adjacent Env trimers aggregated via directed movement.
