Structure dynamics of HIV-1 Env trimers on native virions engaged with living T cells

Irene Carlon-Andres,Tomas Malinauskas,Sergi Padilla-Parra

doi:10.1038/s42003-021-02658-1

Irene Carlon-Andres, Tomas Malinauskas + Show 1 more

Open Access

https://doi.org/10.1038/s42003-021-02658-1

Copy DOI

Abstract

The HIV-1 envelope glycoprotein (Env) mediates viral entry into the host cell. Although the highly dynamic nature of Env intramolecular conformations has been shown with single molecule spectroscopy in vitro, the bona fide Env intra- and intermolecular mechanics when engaged with live T cells remains unknown. We used two photon fast fluorescence lifetime imaging detection of single-molecule Förster Resonance Energy Transfer occurring between fluorescent labels on HIV-1 Env on native virions. Our observations reveal Env dynamics at two levels: transitions between different intramolecular conformations and intermolecular interactions between Env within the viral membrane. Furthermore, we show that three broad neutralizing anti-Env antibodies directed to different epitopes restrict Env intramolecular dynamics and interactions between adjacent Env molecules when engaged with living T cells. Importantly, our results show that Env-Env interactions depend on efficient virus maturation, and that is disrupted upon binding of Env to CD4 or by neutralizing antibodies. Thus, this study illuminates how different intramolecular conformations and distribution of Env molecules mediate HIV-1 Env–T cell interactions in real time and therefore might control immune evasion.

Highlights

The HIV-1 envelope glycoprotein (Env) mediates viral entry into the host cell
Characterization of HIV-1 Env structural dynamics by two photon Förster Resonance Energy Transfer (FRET)-FLIM. Aiming to ascertain both intramolecular and intermolecular Env dynamics with a multiparameter FRET and fluorescence lifetime microscopy (FLIM) approach, we produced HIV-1 virions labelled with super folder GFP (GFPOPT) in the V4 loop of gp[120] HXB2 Env glycoprotein (Fig. 1a–c)[27]
This particular labelling strategy allows FRET to occur between donor and acceptor dipoles located in a single Env molecule and between adjacent Env molecules, when fluorophores are in close enough proximity and in a proper orientation (Fig. 2a)

Summary

Introduction

The HIV-1 envelope glycoprotein (Env) mediates viral entry into the host cell. the highly dynamic nature of Env intramolecular conformations has been shown with single molecule spectroscopy in vitro, the bona fide Env intra- and intermolecular mechanics when engaged with live T cells remains unknown. Munro et al.,[20] pioneered in the study of in vitro intramolecular structural dynamics of fluorescently labelled HIV Env trimers in native virions utilizing single-molecule Förster Resonance Energy Transfer (FRET) This technique revealed the dynamic fluctuations of the distance between fluorescently labelled residues within the Env trimer in a millisecond-second timescale. These studies performed in the native, virion-associated Env of different HIV-1 strains helped to describe three different intramolecular conformational states of Env: first, Env adopts a closed conformation (named State 1) right before CD4 asymmetric interaction; second, after CD4 engagement, Env adopts an intermediate state (State 2) followed by a last open conformation for the coreceptor engagement (State 3) that exposes otherwise hidden epitopes, increasing susceptibility for antibody recognition[18,19,20]

Methods

Results

Conclusion