Eine neuartige Lipid (Phosphatidylthreonin-)regulierte Calciumhomöostase in Toxoplasma gondii


The major membrane glycerophospholipid classes, described thus far, include phosphatidylcholine,
phosphatidylethanolamine, phosphatidylserine (PtdSer) and phosphatidylinositol. Our recent work has
demonstrated the natural occurrence and genetic origin of an exclusive and rather abundant lipid
phosphatidylthreonine (PtdThr) in a widespread and clinically relevant eukaryotic model parasite
Toxoplasma gondii. Of note is the fact that PtdThr is a natural homolog of the otherwise-universal
PtdSer, which is long known to control Ca2+ homeostasis in mammalian cells. Our earlier work showed
that targeted genetic disruption of phosphatidylthreonine synthase (PTS) impairs the lytic cycle and
virulence of the parasite due to unforeseen attenuation of the consecutive events of motility, egress
and invasion. Using a calcium biosensor, we observed that loss of PtdThr causes a dysregulation of
cytosolic calcium that in turn translates into a defective gliding motility. In this proposal, we aim to
examine the mechanistic regulation of calcium homeostasis by PtdThr using an approach spanning
across the disciplines of biochemistry, gene engineering, cell biology and synthetic chemistry. In brief,
we will determine the levels of calcium in the cytosol and endoplasmic reticulum (i.e. site of PtdThr and
PtdSer synthesis) of the PTS-mutant by expressing a gene-encoded sensor. Assays involving genetic
or chemical modulation of calcium homeostasis, and genetic restoration of lipid perturbation in the
PtdThr-mutant will be done to establish a role of lipids in calcium regulation. In parallel, we will identify
PtdSer/PtdThr-binding proteins underlying Ca2+ regulation by click-chemistry and mass spectrometry,
followed by making of selected parasite mutants and phenotyping. Equally, subcellular distribution of
PtdThr and PtdSer will be detected using synthetic chemical probes and customized lipid biosensors
via high-resolution imaging. Not least, physiological importance of the key PtdThr species in T. gondii
will be investigated by chemical complementation of the parasite cultures. Upon completion, we shall
understand the roles of PtdThr (and PtdSer) in calcium homeostasis during asexual reproduction of T.
gondii, which can eventually be exploited to inhibit the parasite growth.

Projektleitung
Gupta, Nishith Dr. (Details) (Molekulare Parasitologie II)

Laufzeit
Projektstart: 02/2019
Projektende: 01/2022

Forschungsbereiche
Medizinische Mikrobiologie und Mykologie, Hygiene, Molekulare Infektionsbiologie

Zuletzt aktualisiert 2021-04-01 um 17:49