HIV-1 viral infectivity factor interacts with microtubule-associated protein light chain 3 and inhibits autophagy

Autophagy, an important antiviral process triggered during HIV-1 entry by gp41-dependent membrane fusion, is repressed in infected CD4+ T cells by an unknown mechanism. The aim of this study was to identify the role of viral infectivity factor (Vif) in the autophagy blockade.

To determine the role of Vif in autophagy inhibition, we used cell lines that express CD4 and CXCR4 and primary CD4+ T cells. Pull-down experiments, immunoprecipitation assays and computational analyses were performed to analyze the interaction between Vif and microtubule-associated protein light chain 3B (LC3B), a major autophagy component, in presence or absence of the antiviral host factor apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3G (APOBEC3G), after HIV-1 infection or ectopic expression of Vif. Autophagy was analyzed after infection by viruses expressing Vif (NL4.3) or not (NL4.3[DELTA]Vif), or after exogenous Vif expression.

We demonstrate that the C-terminal part of Vif interacts directly with LC3B, independently of the presence of APOBEC3G.Vif binds to pro-LC3 and autophagy-related protein 4-cleaved LC3 forms, and glycine 120, the amino acid conjugated to phosphatidylethanolamine on autophagosomes, is required. Importantly, we evidence that Vif inhibits autophagy during HIV-1 infection. Indeed, autophagy is detected in target cells infected by NL4.3[DELTA]Vif, but prevented in cells infected by NL4.3. Furthermore, autophagy triggered in NL4.3[DELTA]Vif-infected cells is inhibited when Vif is expressed in trans but is still active when target cells express a mutant of Vif that binds weakly to LC3B.

Our study unveils that Vif inhibits autophagy independently of its action on APOBEC3G and, therefore, suggest a new function of this viral protein in restricting innate antiviral mechanisms.