Cyclophilin A enables specific HIV-1 Tat palmitoylation and accumulation in uninfected cells

Christophe Chopard,Hocine Yezid,Petra Tóth,Solène Debaisieux,Jean-Marc Strub,Jean-Michel Mesnard,Malvina Schatz,Antoine Gross,Annie Tu,Bruno Beaumelle,Clément Mettling,Martine Pugnière,Phuoc Bao Viet Tong,Nicolas Vitale

doi:10.1038/s41467-018-04674-y

Abstract

Most HIV-1 Tat is unconventionally secreted by infected cells following Tat interaction with phosphatidylinositol (4,5) bisphosphate (PI(4,5)P2) at the plasma membrane. Extracellular Tat is endocytosed by uninfected cells before escaping from endosomes to reach the cytosol and bind PI(4,5)P2. It is not clear whether and how incoming Tat concentrates in uninfected cells. Here we show that, in uninfected cells, the S-acyl transferase DHHC-20 together with the prolylisomerases cyclophilin A (CypA) and FKBP12 palmitoylate Tat on Cys31 thereby increasing Tat affinity for PI(4,5)P2. In infected cells, CypA is bound by HIV-1 Gag, resulting in its encapsidation and CypA depletion from cells. Because of the lack of this essential cofactor, Tat is not palmitoylated in infected cells but strongly secreted. Hence, Tat palmitoylation specifically takes place in uninfected cells. Moreover, palmitoylation is required for Tat to accumulate at the plasma membrane and affect PI(4,5)P2-dependent membrane traffic such as phagocytosis and neurosecretion.

Highlights

Most HIV-1 Tat is unconventionally secreted by infected cells following Tat interaction with phosphatidylinositol (4,5) bisphosphate (PI(4,5)P2) at the plasma membrane
HIV-1 infected patients suffer from defects in phagocytosis[16] and cardiac repolarization[17]. They present various neurocognitive disorders[18]. In target cells such as macrophages, neurons and myocytes, incoming Tat binds to PI(4,5)P2 and severely inhibits cell machineries that rely on protein recruitment by this phosphoinositide, i.e., phagocytosis, neurosecretion and key cardiac potassium channels[19]
We found that HIV-1 budding essentially depletes cells in cyclophilin A (CypA) and, because CypA is required for Tat palmitoylation, this process is thereby inhibited in infected cells

Summary

Introduction

Most HIV-1 Tat is unconventionally secreted by infected cells following Tat interaction with phosphatidylinositol (4,5) bisphosphate (PI(4,5)P2) at the plasma membrane. In target cells such as macrophages, neurons and myocytes, incoming Tat binds to PI(4,5)P2 and severely inhibits cell machineries that rely on protein recruitment by this phosphoinositide, i.e., phagocytosis, neurosecretion and key cardiac potassium channels[19]. To this end, Tat prevents cdc[42] recruitment at the phagocytic cup in macrophages thereby inhibiting phagocytosis[20]. How can such small doses of Tat be inhibitory while plenty of PI(4,5)P2 (~ 10 μM23) is present within cells? And how is it possible for Tat to perturb PI(4,5)P2 mediated protein recruitment while it should quickly abandon PI(4,5)P2 to cross the plasma membrane for secretion?

Methods

Results

Conclusion