EXP2 is a nutrient-permeable channel in the vacuolar membrane of Plasmodium and is essential for protein export via PTEX

Abstract

Intraerythrocytic malaria parasites reside within a parasitophorous vacuolar membrane (PVM) generated during host cell invasion. Erythrocyte remodelling and parasite metabolism require the export of effector proteins and transport of small molecules across this barrier between the parasite surface and host cell cytosol. Protein export across the PVM is accomplished by the Plasmodium translocon of exported proteins (PTEX) consisting of three core proteins, the AAA+ ATPase HSP101 and two additional proteins known as PTEX150 and EXP2. Inactivation of HSP101 and PTEX150 arrests protein export across the PVM, but the contribution of EXP2 to parasite biology is not well understood. A nutrient permeable channel in the PVM has also been characterized electrophysiologically, but its molecular identity is unknown. Here, using regulated gene expression, mutagenesis and cell-attached patch-clamp measurements, we show that EXP2, the putative membrane-spanning channel of PTEX, serves dual roles as a protein-conducting channel in the context of PTEX and as a channel able to facilitate nutrient passage across the PVM independent of HSP101. Our data suggest a dual functionality for a channel operating in its endogenous context.