Self assembly of HIV-1 Gag protein on lipid membranes generates PI(4,5)P2/Cholesterol nanoclusters.

Naresh Yandrapalli,Quentin Lubart,Hanumant S Tanwar,Johnson Mak,Catherine Picart,Delphine Muriaux,Cyril Favard

doi:10.1038/srep39332

Abstract

The self-assembly of HIV-1 Gag polyprotein at the inner leaflet of the cell host plasma membrane is the key orchestrator of virus assembly. The binding between Gag and the plasma membrane is mediated by specific interaction of the Gag matrix domain and the PI(4,5)P2 lipid (PIP2). It is unknown whether this interaction could lead to local reorganization of the plasma membrane lipids. In this study, using model membranes, we examined the ability of Gag to segregate specific lipids upon self-assembly. We show for the first time that Gag self-assembly is responsible for the formation of PIP2 lipid nanoclusters, enriched in cholesterol but not in sphingomyelin. We also show that Gag mainly partition into liquid-disordered domains of these lipid membranes. Our work strongly suggests that, instead of targeting pre-existing plasma membrane lipid domains, Gag is more prone to generate PIP2/Cholesterol lipid nanodomains at the inner leaflet of the plasma membrane during early events of virus assembly.

Highlights

The self-assembly of HIV-1 Gag polyprotein at the inner leaflet of the cell host plasma membrane is the key orchestrator of virus assembly
Since PIP2, Chol and SPM have been shown to be enriched in the virus envelope[7], the impact of Gag self-assembly on their lateral distribution was tested in different types of model membranes (Fig. 1A) exhibiting different lipid compositions
Given that the plasma membrane of HIV producing cells (~10 μm in diameter) has reduced level of curvature compared to these Large unilamellar vesicles (LUVs) (100 nm in diameter), we have used supported lipid bilayers (SLBs) as membrane models for analyses

Summary

Introduction

The self-assembly of HIV-1 Gag polyprotein at the inner leaflet of the cell host plasma membrane is the key orchestrator of virus assembly. Our work strongly suggests that, instead of targeting pre-existing plasma membrane lipid domains, Gag is more prone to generate PIP2/Cholesterol lipid nanodomains at the inner leaflet of the plasma membrane during early events of virus assembly. The retroviral Gag protein drives the assembly process of the Human Immunodeficiency Virus type 1(HIV-1) particles[1,2] This protein is synthesized as a polyprotein Pr55 Gag, which contains three major structural domains, namely matrix (MA), capsid (CA) and nucleocapsid (NC), as well as two spacer peptides, sp[1] and sp[2] and an unstructured C-terminus p6 peptide. In order to elucidate whether Gag would bind to pre-existing “rafts” or lipid domains in the PM or generate its own lipid domains for assembling, we first decided to monitor its binding and partitioning to single or dual-phase model membranes made with simple and complex lipid compositions (see Table 1 for detailed composition of lipid mixtures). We extended this study to more complex lipid compositions mimicking either lipid “rafts” or inner leaflet of the PM

Methods

Results

Discussion

Conclusion