VAPA mediates lipid exchange between Leishmania amazonensis and host macrophages
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Leishmania is a vacuolar pathogen that replicates within parasitophorous vacuoles inside host phagocytes. To promote its replication, Leishmania relies on a panoply of strategies to acquire macromolecules such as lipids from host macrophages. In this study, we have evaluated the role of VAPA, an endoplasmic reticulum-resident membrane protein involved in inter-organellar lipid transport, in macrophages infected with L. amazonensis . Following infection of bone marrow-derived macrophages with metacyclic L. amazonensis promastigotes, we observed that VAPA gradually associates with communal parasitophorous vacuoles. Knockdown of VAPA prevented the replication of L. amazonensis , which was accompanied by an impaired parasitophorous vacuole expansion. Using fluorescent ceramide, we established that VAPA is required for the transport of sphingolipids to the parasitophorous vacuoles and for its acquisition by L. amazonensis amastigotes. Proximity-ligation and immunoprecipitation assays revealed that L. amazonensis hijacks VAPA by disrupting its interactions with the lipid transfer proteins CERT and ORP1L. Finally, we found that VAPA is essential for the transfer of the Leishmania virulence glycolipid lipophosphoglycan from the parasitophorous vacuoles to the host cell endoplasmic reticulum. We propose that VAPA contributes to the ability of L. amazonensis to colonize macrophages by mediating bi-directional transfer of lipids essential for parasite replication and virulence between the parasitophorous vacuoles and the host cell endoplasmic reticulum.
AUTHOR SUMMARY
The protozoan parasite Leishmania amazonensis replicates in macrophages, within communal parasitophorous vacuoles. To satisfy its various auxotrophies, this parasite must obtain macronutrients and metabolites from its host cell, including lipids. To salvage host sphingolipids, we obtained evidence that L. amazonensis exploits a macrophage nonvesicular lipid transport mechanism that requires the endoplasmic reticulum membrane protein VAPA. Moreover, we found that VAPA is also required for the transfer of the Leishmania virulence glycolipid lipophosphoglycan from the parasitophorous vacuole to the macrophage endoplasmic reticulum. The fact that VAPA is essential for L. amazonensis to colonize macrophages is consistent with the central role that VAPA plays in mediating bi-directional transfer of lipids and illustrates the importance of the host cell endoplasmic reticulum in this host-parasite interaction.
