Single molecule fate of HIV-1 envelope reveals late-stage viral lattice incorporation

Carmen A Buttler,Schuyler B Van Engelenburg,Jesse Aaron,Sofya Norman,Nairi Pezeshkian,Melissa V Fernandez,Eric O Freed

doi:10.1038/s41467-018-04220-w

Abstract

Human immunodeficiency virus type 1 (HIV-1) assembly occurs on the inner leaflet of the host cell plasma membrane, incorporating the essential viral envelope glycoprotein (Env) within a budding lattice of HIV-1 Gag structural proteins. The mechanism by which Env incorporates into viral particles remains poorly understood. To determine the mechanism of recruitment of Env to assembly sites, we interrogate the subviral angular distribution of Env on cell-associated virus using multicolor, three-dimensional (3D) superresolution microscopy. We demonstrate that, in a manner dependent on cell type and on the long cytoplasmic tail of Env, the distribution of Env is biased toward the necks of cell-associated particles. We postulate that this neck-biased distribution is regulated by vesicular retention and steric complementarity of Env during independent Gag lattice formation.

Highlights

Human immunodeficiency virus type 1 (HIV-1) assembly occurs on the inner leaflet of the host cell plasma membrane, incorporating the essential viral envelope glycoprotein (Env) within a budding lattice of HIV-1 Gag structural proteins
Our single-molecule approach, imaging the subviral angular distribution of native levels of Env on the surface of nascent budding HIV-1 particles, enabled accurate quantification of a neck-biased phenotype present on particles produced in the T-cell line CEMA, but not on those produced in the fibroblast-like line COS7
We chose to use a late-domain mutant Gag to trap and preserve the angular orientation of Env during virus budding, as particle release would result in scrambling of the angular distribution of Env

Summary

Introduction

Human immunodeficiency virus type 1 (HIV-1) assembly occurs on the inner leaflet of the host cell plasma membrane, incorporating the essential viral envelope glycoprotein (Env) within a budding lattice of HIV-1 Gag structural proteins. In a manner dependent on cell type and on the long cytoplasmic tail of Env, the distribution of Env is biased toward the necks of cell-associated particles We postulate that this neck-biased distribution is regulated by vesicular retention and steric complementarity of Env during independent Gag lattice formation. Further compounding the complexity of HIV-1 assembly is the relative sparsity of Env on individual released particles (7–14 trimers)[9] This suggests that Env incorporation into nascent Gag lattices is tightly regulated, but the mechanisms of regulation are poorly understood. We show that Env encounters the Gag lattice late in lattice assembly and that this is cell-type-dependent as well as dependent on the Env-CT

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Results

Conclusion