Optogenetic monitoring identifies phosphatidylthreonine-regulated calcium homeostasis in Toxoplasma gondii

Authors:

Arunakar Kuchipudi1, Ruben D. Arroyo-Olarte1, Friederike Hoffmann1, Volker Brinkmann2, Nishith Gupta1, 2

doi: 10.15698/mic2016.05.500
Volume 3, pp. 215 to 223, published 02/05/2016.

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Affiliations:

1 Humboldt University, Berlin, Germany.

2 Max-Planck Institute for Infection Biology, Berlin, Germany.

Keywords: 

Toxoplasma gondii, phosphatidylthreonine, optogenetics, gene-encoded calcium indicator, lytic cycle, intracellular parasite, calcium homeostasis.

Corresponding Author(s):

Nishith Gupta, PhD, Department of Molecular Parasitology, Humboldt University, Philippstrasse 13, House 14, Berlin, Germany; Telephone: +49-30-20936404; Fax: +49-30-20936051 Gupta.Nishith@staff.hu-berlin.de

Conflict of interest statement:

The authors declare that there are no conflicts of interest pertaining to this work.

Please cite this article as:

Arunakar Kuchipudi, Ruben Dario Arroyo-Olarte, Friederike Hoffmann, Volker Brinkmann, Nishith Gupta (2016). Optogenetic monitoring identifies phosphatidylthreonine-regulated calcium homeostasis in Toxoplasma gondii. Microbial Cell 3(5): 215-223. doi: 10.15698/mic2016.05.500

© 2016 Kuchipudi et al. This is an open-access article released under the terms of the Creative Commons Attribution (CC BY) license, which allows the unrestricted use, distribution, and reproduction in any medium, provided the original author and source are acknowledged.

Abstract:

Toxoplasma gondii is an obligate intracellular parasite, which inflicts acute as well as chronic infections in a wide range of warm-blooded vertebrates. Our recent work has demonstrated the natural occurrence and autonomous synthesis of an exclusive lipid phosphatidylthreonine in T. gondii. Targeted gene disruption of phosphatidylthreonine synthase impairs the parasite virulence due to unforeseen attenuation of the consecutive events of motility, egress and invasion. However, the underlying basis of such an intriguing phenotype in the parasite mutant remains unknown. Using an optogenetic sensor (gene-encoded calcium indicator, GCaMP6s), we show that loss of phosphatidylthreonine depletes calcium stores in intracellular tachyzoites, which leads to dysregulation of calcium release into the cytosol during the egress phase of the mutant. Consistently, the parasite motility and egress phenotypes in the mutant can be entirely restored by ionophore-induced mobilization of calcium. Collectively, our results suggest a novel regulatory function of phosphatidylthreonine in calcium signaling of a prevalent parasitic protist. Moreover, our application of an optogenetic sensor to monitor subcellular calcium in a model intracellular pathogen exemplifies its wider utility to other entwined systems.