Functional organization of the HIV lipid envelope.

Nerea Huarte,Maier Lorizate,Pablo Carravilla,Jon A Nieto-Garai,Antonio Cruz,Hans-Georg Kräusslich,José L Nieva,Jesús Pérez-Gil,Jose Requejo-Isidro

doi:10.1038/srep34190

Abstract

The chemical composition of the human immunodeficiency virus type 1 (HIV-1) membrane is critical for fusion and entry into target cells, suggesting that preservation of a functional lipid bilayer organization may be required for efficient infection. HIV-1 acquires its envelope from the host cell plasma membrane at sites enriched in raft-type lipids. Furthermore, infectious particles display aminophospholipids on their surface, indicative of dissipation of the inter-leaflet lipid asymmetry metabolically generated at cellular membranes. By combining two-photon excited Laurdan fluorescence imaging and atomic force microscopy, we have obtained unprecedented insights into the phase state of membranes reconstituted from viral lipids (i.e., extracted from infectious HIV-1 particles), established the role played by the different specimens in the mixtures, and characterized the effects of membrane-active virucidal agents on membrane organization. In determining the molecular basis underlying lipid packing and lateral heterogeneity of the HIV-1 membrane, our results may help develop compounds with antiviral activity acting by perturbing the functional organization of the lipid envelope.

Highlights

The human immunodeficiency virus type 1 (HIV-1) is an enveloped virus that follows a membrane fusion strategy to access and activate the replication cycle within the cytoplasm of host cells, typically CD4+ T cells and cells of the monocyte/macrophage lineage[1]
To gain insight into the molecular basis governing packing order and lateral heterogeneity in the complex HIV membrane, we have studied Giant Unilamellar Vesicles (GUVs) and monolayers made of lipids extracted from infectious HIV-112
Our results indicate that the complex HIV membrane is highly packed, but less ordered than the rigid domains segregated in DOPC:SM:Chol-based models, and may display de-mixed nanoscopic lipid assemblies modulated by the lipid composition

Summary

Introduction

The human immunodeficiency virus type 1 (HIV-1) is an enveloped virus that follows a membrane fusion strategy to access and activate the replication cycle within the cytoplasm of host cells, typically CD4+ T cells and cells of the monocyte/macrophage lineage[1]. Host cell recognition and fusion with its plasma membrane is mediated by the viral envelope glycoprotein (Env)[2]. HIV-1 acquires its lipid envelope and Env proteins by assembly and budding at the plasma membrane of the infected cell[7,8]. Advanced mass spectrometry combined with protocols optimized for the isolation of viral lipids enabled the determination of the HIV-1 membrane composition[9,10,11]. These studies showed that cholesterol (Chol) and sphingomyelin (SM) are enriched in the virus at concentrations similar to those in detergent-resistant membranes[9]. To assess the functional relevance of lipid order and miscibility, we have characterized the perturbing effects exerted by membrane-active agents on membranes made from virus-derived lipids, correlating with their virucidal activity

Methods

Results

Conclusion