SMAC Mimetics Induce Autophagy-Dependent Apoptosis of HIV-1-Infected Resting Memory CD4+ T Cells

Abstract

Long-lived resting memory CD4+ T cells (T_CM) are a major reservoir of latent HIV infection. We hypothesized that latent HIV-T_CM cells are maintained by aberrant expression of cell survival factors, including XIAP, BIRC2/cIAP1, and beclin-1. DIABLO/SMAC mimetics are therapeutic agents that compromise cell survival by hijacking host apoptotic machinery. We found that DIABLO/SMAC mimetics (birinapant, GDC-0152, and embelin) selectively kill HIV-T_CM without increasing virus production or targeting uninfected T_CM. Treatment of HIV-T_CM with DIABLO/SMAC mimetics promoted XIAP and BIRC2 degradation, which triggered autophagy and the formation of a cell death complex consisting of pro-apoptotic (FADD, RIPK1, RIPK3, and caspase 8) and autophagy (ATG5, ATG7, and SQSTM1) proteins. Genetic or pharmacological inhibition of autophagy induction, but not autophagy-mediated degradation, abrogated this interaction and subsequent cell death. Our findings identify a mechanism whereby DIABLO/SMAC mimetics exploit autophagy and apoptotic machinery to selectively induce killing of HIV-T_CM without viral reactivation while sparing uninfected cells.

Keywords: BIRC2; CD4+ T cell; Fas; HIV; RIPK1; SMAC mimetics; XIAP; apoptosis; autophagy; caspase 8.