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

Nature Microbiology volume 3, pages 1090–1098 (2018)Cite this article

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Abstract

Intraerythrocytic malaria parasites reside within a parasitophorous vacuolar membrane (PVM) generated during host cell invasion1. 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 cytosol2,3. 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 EXP24. Inactivation of HSP101 and PTEX150 arrests protein export across the PVM5,6, but the contribution of EXP2 to parasite biology is not well understood7. A nutrient permeable channel in the PVM has also been characterized electrophysiologically, but its molecular identity is unknown8,9. Here, using regulated gene expression, mutagenesis and cell-attached patch-clamp measurements, we show that EXP2, the putative membrane-spanning channel of PTEX4,10,11,12,13,14, 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.

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Fig. 1: EXP2 is essential for blood stage survival and protein export.
Fig. 2: EXP2 expression differs from other PTEX components.
Fig. 3: PVM channel characteristics and correlation with EXP2 levels.
Fig. 4: Altered voltage response of the PVM channel in EXP2apt::∆234–287 parasites.

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Acknowledgements

This work was supported by NIH grants HL133453 to J.R.B. and AI47798 to D.E.G. and by the Division of Intramural Research of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health. We thank S. Glushakova for creating and applying the parasite liberation technique, for performing the IMF experiment and for many helpful conversations throughout the course of this project. We thank J. McBride, D. Cavanagh and EMRR for the EXP2 antibody, D. Taylor for HRP2 antibody, C. Braun-Breton for SBP1 antibody, W. Beatty for assistance with electron microscopy, P. Gurnev for the buffer conductivity measurement, P. S. Blank for helpful suggestions for the statistical analysis of the patch-clamp data and B. Vaupel for technical assistance.

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Authors and Affiliations

  1. Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA

    Matthias Garten & Joshua Zimmerberg

  2. Departments of Medicine and Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, USA

    Armiyaw S. Nasamu, Daniel E. Goldberg & Josh R. Beck

  3. Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA

    Jacquin C. Niles

  4. Department of Biomedical Sciences, Iowa State University, Ames, IA, USA

    Josh R. Beck

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Contributions

M.G., J.Z., D.E.G. and J.R.B. conceived and designed experiments. M.G. and J.R.B. performed the experiments. J.R.B. generated and analysed the parasite strains. M.G. performed patch-clamp analysis. A.S.N. generated the pEXP2apt plasmid. J.C.N. contributed reagents. M.G., J.Z., D.E.G. and J.R.B. analysed the data and wrote the manuscript. All authors discussed and edited the manuscript.

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Correspondence to Joshua Zimmerberg or Daniel E. Goldberg.

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Garten, M., Nasamu, A.S., Niles, J.C. et al. EXP2 is a nutrient-permeable channel in the vacuolar membrane of Plasmodium and is essential for protein export via PTEX. Nat Microbiol 3, 1090–1098 (2018). https://doi.org/10.1038/s41564-018-0222-7

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