Toxoplasma bradyzoites exhibit physiological plasticity of calcium and energy stores controlling motility and egress

  1. Yong Fu
  2. Kevin M Brown
  3. Nathaniel G Jones
  4. Silvia NJ Moreno
  5. L David Sibley  Is a corresponding author
  1. Washington University in St. Louis, United States
  2. University of Georgia, United States

Abstract

Toxoplasma gondii has evolved different developmental stages for disseminating during acute infection (i.e. tachyzoites) and for establishing chronic infection (i.e. bradyzoites). Calcium ion (Ca2+) signaling tightly regulates the lytic cycle of tachyzoites by controlling microneme secretion and motility to drive egress and cell invasion. However, the roles of Ca2+ signaling pathways in bradyzoites remain largely unexplored. Here we show that Ca2+ responses are highly restricted in bradyzoites and that they fail to egress in response to agonists. Development of dual-reporter parasites revealed dampened Ca2+ responses and minimal microneme secretion by bradyzoites induced in vitro or harvested from infected mice and tested ex vivo. Ratiometric Ca2+ imaging demonstrated lower Ca2+ basal levels, reduced magnitude, and slower Ca2+ kinetics in bradyzoites compared with tachyzoites stimulated with agonists. Diminished responses in bradyzoites were associated with down-regulation of Ca2+-ATPases involved in intracellular Ca2+ storage in the endoplasmic reticulum (ER) and acidocalcisomes. Once liberated from cysts by trypsin digestion, bradyzoites incubated in glucose plus Ca2+ rapidly restored their intracellular Ca2+ and ATP stores leading to enhanced gliding. Collectively, our findings indicate that intracellular bradyzoites exhibit dampened Ca2+ signaling and lower energy levels that restrict egress, and yet upon release they rapidly respond to changes in the environment to regain motility.

Data availability

All of the data generated and analysed are included in the manuscript and supporting files including the meta data files.

Article and author information

Author details

  1. Yong Fu

    Department of Molecular Microbiology, Washington University in St. Louis, St Louis, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Kevin M Brown

    Department of Molecular Microbiology, Washington University in St. Louis, St Louis, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Nathaniel G Jones

    Department of Molecular Microbiology, Washington University in St. Louis, St Louis, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Silvia NJ Moreno

    Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-2041-6295
  5. L David Sibley

    Department of Molecular Microbiology, Washington University in St. Louis, St Louis, United States
    For correspondence
    sibley@wustl.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-7110-0285

Funding

National Institutes of Health (AI034036)

  • L David Sibley

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Malcolm J McConville, The University of Melbourne, Australia

Publication history

  1. Preprint posted: May 17, 2021 (view preprint)
  2. Received: August 12, 2021
  3. Accepted: December 3, 2021
  4. Accepted Manuscript published: December 3, 2021 (version 1)
  5. Version of Record published: December 16, 2021 (version 2)
  6. Version of Record updated: January 27, 2022 (version 3)

Copyright

© 2021, Fu et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Yong Fu
  2. Kevin M Brown
  3. Nathaniel G Jones
  4. Silvia NJ Moreno
  5. L David Sibley
(2021)
Toxoplasma bradyzoites exhibit physiological plasticity of calcium and energy stores controlling motility and egress
eLife 10:e73011.
https://doi.org/10.7554/eLife.73011
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