Conditional mutagenesis of a novel choline kinase demonstrates plasticity of phosphatidylcholine biogenesis and gene expression in Toxoplasma gondii

Vera Sampels, Anne Hartmann, Isabelle Dietrich, Isabelle Coppens, Lilach Sheiner, Boris Striepen, Andreas Herrmann, Richard Lucius, Nishith Gupta

Research output: Contribution to journalArticle

Abstract

The obligate intracellular and promiscuous protozoan parasite Toxoplasma gondii needs an extensive membrane biogenesis that must be satisfied irrespective of its host-cell milieu. We show that the synthesis of the major lipid in T. gondii, phosphatidylcholine (PtdCho), is initiated by a novel choline kinase (TgCK). Full-length (∼70-kDa) TgCK displayed a low affinity for choline (Km ∼0.77 mM) and harbors a unique N-terminal hydrophobic peptide that is required for the formation of enzyme oligomers in the parasite cytosol but not for activity. Conditional mutagenesis of the TgCK gene in T. gondii attenuated the protein level by ∼60%, which was abolished in the off state of the mutant (Δtgcki). Unexpectedly, the mutant was not impaired in its growth and exhibited a normal PtdCho biogenesis. The parasite compensated for the loss of full-length TgCK by two potential 53- and 44-kDa isoforms expressed through a cryptic promoter identified within exon 1. TgCK-Exon1 alone was sufficient in driving the expression of GFP in E. coli. The presence of a cryptic promoter correlated with the persistent enzyme activity, PtdCho synthesis, and susceptibility of T. gondii to a choline analog, dimethylethanolamine. Quite notably, the mutant displayed a regular growth in the off state despite a 35% decline in PtdCho content and lipid synthesis, suggesting a compositional flexibility in the membranes of the parasite. The observed plasticity of gene expression and membrane biogenesis can ensure a faithful replication and adaptation of T. gondii in disparate host or nutrient environments.

Original languageEnglish (US)
Pages (from-to)16289-16299
Number of pages11
JournalJournal of Biological Chemistry
Volume287
Issue number20
DOIs
StatePublished - May 11 2012

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Choline Kinase
Mutagenesis
Toxoplasma
Phosphatidylcholines
Gene expression
Plasticity
Gene Expression
Parasites
Choline
Membranes
Deanol
Lipids
Enzyme activity
Ports and harbors
Oligomers
Escherichia coli
Nutrients
Exons
Enzymes
Growth

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

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Conditional mutagenesis of a novel choline kinase demonstrates plasticity of phosphatidylcholine biogenesis and gene expression in Toxoplasma gondii. / Sampels, Vera; Hartmann, Anne; Dietrich, Isabelle; Coppens, Isabelle; Sheiner, Lilach; Striepen, Boris; Herrmann, Andreas; Lucius, Richard; Gupta, Nishith.

In: Journal of Biological Chemistry, Vol. 287, No. 20, 11.05.2012, p. 16289-16299.

Research output: Contribution to journalArticle

Sampels, Vera ; Hartmann, Anne ; Dietrich, Isabelle ; Coppens, Isabelle ; Sheiner, Lilach ; Striepen, Boris ; Herrmann, Andreas ; Lucius, Richard ; Gupta, Nishith. / Conditional mutagenesis of a novel choline kinase demonstrates plasticity of phosphatidylcholine biogenesis and gene expression in Toxoplasma gondii. In: Journal of Biological Chemistry. 2012 ; Vol. 287, No. 20. pp. 16289-16299.
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