Abstract

Pregnancy-associated malaria commonly involves the binding of Plasmodium falciparum-infected erythrocytes to placental chondroitin sulfate A (CSA) through the PfEMP1–VAR2CSA protein. VAR2CSA is translationally repressed by an upstream open reading frame. In this study, we report that the P. falciparum translation enhancing factor (PTEF) relieves upstream open reading frame repression and thereby facilitates VAR2CSA translation. VAR2CSA protein levels in var2csa-transcribing parasites are dependent on the expression level of PTEF, and the alleviation of upstream open reading frame repression requires the proteolytic processing of PTEF by PfCalpain. Cleavage generates a C-terminal domain that contains a sterile-alpha-motif-like domain. The C-terminal domain is permissive to cytoplasmic shuttling and interacts with ribosomes to facilitate translational derepression of the var2csa coding sequence. It also enhances translation in a heterologous translation system and thus represents the first non-canonical translation enhancing factor to be found in a protozoan. Our results implicate PTEF in regulating placental CSA binding of infected erythrocytes.

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Acknowledgements

The authors thank the Scilifelab in Stockholm for RNA-seq and mass spectrometry experiments, K.W. Deitsch for providing luciferase reporter plasmids and for guidance on our experimental design, BEI Resources and MR4 for supplying DSM1, and BILS for providing support for the transcriptomic analysis. This study was supported by the Swedish Research Council (VR/2012-2014/521-2011-3377 to M.W.), the Söderberg Foundation and Swedish Academy of Sciences (to M.W.), the Swedish Strategic Foundation (to M.W.), the EU EviMalar Network of Excellence (to M.W.), a Distinguished Professor Award from Karolinska Institutet (to M.W.) and the Swedish Research Council (VR 2013-8778, 2014-4423 and 2016-06264 to S.S.) and the Knut and Alice Wallenberg Foundation (KAW 2011.0081, RiboCORE to S.S.). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Author information

Affiliations

  1. Department of Microbiology, Tumor and Cell Biology (MTC), Karolinska Institutet, Box 280, Nobels väg 16, 171 77 Stockholm, Sweden

    • Sherwin Chan
    • , Alejandra Frasch
    • , Jun-Hong Ch'ng
    • , Maria del Pilar Quintana
    • , Nicolas Joannin
    •  & Mats Wahlgren
  2. Department of Cell and Molecular Biology, Uppsala University, Box-596, 751 24 Uppsala, Sweden

    • Chandra Sekhar Mandava
    •  & Suparna Sanyal
  3. Department of Microbiology, National University of Singapore 117545, Singapore

    • Jun-Hong Ch'ng
  4. Escuela de Medicina y Ciencias de la Salud, Facultad de Ciencias Naturales y Matemáticas, Universidad del Rosario, Calle 12C No. 6-25, Bogotá, Colombia

    • Maria del Pilar Quintana
  5. Cancer Proteomics, Department of Oncology-Pathology, Karolinska Institutet, 17176 Stockholm, Sweden

    • Mattias Vesterlund
  6. University of Montpellier, Faculty of Medicine, Laboratory of Parasitology-Mycology, Montpellier F34090, France

    • Mehdi Ghorbal
    •  & Jose-Juan Lopez-Rubio
  7. CNRS – 5290, IRD 224 – University of Montpellier (UMR ‘MiVEGEC’), Montpellier, France

    • Mehdi Ghorbal
    •  & Jose-Juan Lopez-Rubio
  8. Department of Genetics and Genomic Sciences, Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, New York 10029, USA

    • Oscar Franzén
  9. Institute for Research in Biomedicine, Università della Svizzera italiana, Bellinzona 6500, Switzerland

    • Sonia Barbieri
    •  & Antonio Lanzavecchia
  10. Institute of Microbiology, ETH Zurich, Zurich 8093, Switzerland

    • Antonio Lanzavecchia

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Contributions

S.C. and M.W. conceived the study. S.C., A.F., J.H.C. and M.P.Q. performed all experiments. C.S.M. and S.S. performed the RTTF assay. M.V. performed the MS experiment. J.J.L.R. and M.G. assisted in CRISPR design. S.B. and A.L. generated the recombinant PAM1.4. N.J. and O.F. performed computational analysis. S.C., A.F., C.S.M., S.S. and M.W. interpreted data and wrote the manuscript.

Competing interests

M.W. is a co-founder and member of the board of directors of Modus Therapeutics AB, a company developing drugs for severe malaria. All other authors declare no financial conflicts of interest.

Corresponding author

Correspondence to Mats Wahlgren.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    Supplementary Figures 1-9, Supplementary Table 5, Supplementary References.

Excel files

  1. 1.

    Supplementary Table 1

    One spreadsheet summarizing the list of genes deleted on the left arm of chromosome 2 and the right arm of chromosome 9 in 3D7S8.4.2 parasites.

  2. 2.

    Supplementary Table 2

    Eight spreadsheets providing a detailed description of all differentially expressed genes between NF54CSA and 3D7S8.4.2 at the four time points collected for the RNAseq experiment.

  3. 3.

    Supplementary Table 3

    Eight spreadsheets providing a list of all proteins detected in mass spectrometry from the blue native gel experiment related to Supplementary Fig. 5.

  4. 4.

    Supplementary Table 4

    Two spreadsheets describing the sequence similarity of all ribosomal proteins between Plasmodium falciparum and Homo sapiens.

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DOI

https://doi.org/10.1038/nmicrobiol.2017.68