The autophagy protein ATG9A promotes HIV-1 infectivity

Elodie Mailler,Sang-Yoon Park,Abdul A Waheed,David C Gershlick,Eric O Freed,Juan S Bonifacino

doi:10.1186/s12977-019-0480-3

Abstract

BackgroundNef is a multifunctional accessory protein encoded by HIV-1, HIV-2 and SIV that plays critical roles in viral pathogenesis, contributing to viral replication, assembly, budding, infectivity and immune evasion, through engagement of various host cell pathways.ResultsTo gain a better understanding of the role of host proteins in the functions of Nef, we carried out tandem affinity purification-mass spectrometry analysis, and identified over 70 HIV-1 Nef-interacting proteins, including the autophagy-related 9A (ATG9A) protein. ATG9A is a transmembrane component of the machinery for autophagy, a catabolic process in which cytoplasmic components are degraded in lysosomal compartments. Pulldown experiments demonstrated that ATG9A interacts with Nef from not only HIV-1 and but also SIV (cpz, smm and mac). However, expression of HIV-1 Nef had no effect on the levels and localization of ATG9A, and on autophagy, in the host cells. To investigate a possible role for ATG9A in virus replication, we knocked out ATG9A in HeLa cervical carcinoma and Jurkat T cells, and analyzed virus release and infectivity. We observed that ATG9A knockout (KO) had no effect on the release of wild-type (WT) or Nef-defective HIV-1 in these cells. However, the infectivity of WT virus produced from ATG9A-KO HeLa and Jurkat cells was reduced by ~ fourfold and eightfold, respectively, relative to virus produced from WT cells. This reduction in infectivity was independent of the interaction of Nef with ATG9A, and was not due to reduced incorporation of the viral envelope (Env) glycoprotein into the virus. The loss of HIV-1 infectivity was rescued by pseudotyping HIV-1 virions with the vesicular stomatitis virus G glycoprotein.ConclusionsThese studies indicate that ATG9A promotes HIV-1 infectivity in an Env-dependent manner. The interaction of Nef with ATG9A, however, is not required for Nef to enhance HIV-1 infectivity. We speculate that ATG9A could promote infectivity by participating in either the removal of a factor that inhibits infectivity or the incorporation of a factor that enhances infectivity of the viral particles. These studies thus identify a novel host cell factor implicated in HIV-1 infectivity, which may be amenable to pharmacologic manipulation for treatment of HIV-1 infection.

Highlights

Nef is a multifunctional accessory protein encoded by human immunodeficiency virus (HIV)-1, HIV-2 and simian immunodeficiency viruses (SIV) that plays critical roles in viral pathogenesis, contributing to viral replication, assembly, budding, infectivity and immune evasion, through engagement of various host cell pathways
Some interactors were common to two or more Nefs. Among these were the subunits of the exocyst (i.e., EXOC1-EXOC8) (Fig. 1c and Additional file 2: Figure S1A, B), a tethering complex that was previously shown to interact with HIV-1 Nef, and to promote Nef-mediated enhancement of nanotube formation [30] and regulation of actin remodeling [34]
To investigate whether the requirement of autophagy-related 9A (ATG9A) for infectivity was dependent on Env, we examined the infectivity of HIV-1 pseudotyped with the vesicular stomatitis virus G glycoprotein (VSV-G) glycoprotein a EEEE WL PxxP

Summary

Introduction

Nef is a multifunctional accessory protein encoded by HIV-1, HIV-2 and SIV that plays critical roles in viral pathogenesis, contributing to viral replication, assembly, budding, infectivity and immune evasion, through engagement of various host cell pathways. Viruses need to circumvent the intrinsic defenses of their hosts in order to replicate and disseminate To this end, primate lentiviruses such as human immunodeficiency viruses (HIV-1, HIV-2) and simian immunodeficiency viruses (SIV) have evolved to encode several virulence factors that create favorable conditions for viral replication within their host cells. Primate lentiviruses such as human immunodeficiency viruses (HIV-1, HIV-2) and simian immunodeficiency viruses (SIV) have evolved to encode several virulence factors that create favorable conditions for viral replication within their host cells Prominent among these factors is Nef, an accessory protein encoded in all HIV1, HIV-2 and SIV genomes that is highly expressed early after infection A flexible loop connecting the folded 84–148 and 178–203 segments becomes structured when it binds to one of its targets, the clathrinassociated adaptor protein complex AP-2 [7]

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Conclusion