A Toxoplasma gondii pseudokinase inhibits host IRG resistance proteins.

Martin C. Fleckenstein, Michael L. Reese, Stephanie Könen-Waisman, John C. Boothroyd, Jonathan C. Howard, Tobias Steinfeldt

Research output: Contribution to journalArticle

85 Citations (Scopus)

Abstract

The ability of mice to resist infection with the protozoan parasite, Toxoplasma gondii, depends in large part on the function of members of a complex family of atypical large GTPases, the interferon-gamma-inducible immunity-related GTPases (IRG proteins). Nevertheless, some strains of T. gondii are highly virulent for mice because, as recently shown, they secrete a polymorphic protein kinase, ROP18, from the rhoptries into the host cell cytosol at the moment of cell invasion. Depending on the allele, ROP18 can act as a virulence factor for T. gondii by phosphorylating and thereby inactivating mouse IRG proteins. In this article we show that IRG proteins interact not only with ROP18, but also strongly with the products of another polymorphic locus, ROP5, already implicated as a major virulence factor from genetic crosses, but whose function has previously been a complete mystery. ROP5 proteins are members of the same protein family as ROP18 kinases but are pseudokinases by sequence, structure, and function. We show by a combination of genetic and biochemical approaches that ROP5 proteins act as essential co-factors for ROP18 and present evidence that they work by enforcing an inactive GDP-dependent conformation on the IRG target protein. By doing so they prevent GTP-dependent activation and simultaneously expose the target threonines on the switch I loop for phosphorylation by ROP18, resulting in permanent inactivation of the protein. This represents a novel mechanism in which a pseudokinase facilitates the phosphorylation of a target by a partner kinase by preparing the substrate for phosphorylation, rather than by upregulation of the activity of the kinase itself.

Original languageEnglish (US)
JournalPLoS Biology
Volume10
Issue number7
DOIs
StatePublished - 2012

Fingerprint

Toxoplasma
Toxoplasma gondii
Phosphorylation
Proteins
proteins
phosphorylation
phosphotransferases (kinases)
Phosphotransferases
GTP Phosphohydrolases
guanosinetriphosphatase
Virulence Factors
mice
virulence
Genetic Crosses
Protozoan Infections
cell invasion
Threonine
Guanosine Triphosphate
interferon-gamma
threonine

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Neuroscience(all)

Cite this

Fleckenstein, M. C., Reese, M. L., Könen-Waisman, S., Boothroyd, J. C., Howard, J. C., & Steinfeldt, T. (2012). A Toxoplasma gondii pseudokinase inhibits host IRG resistance proteins. PLoS Biology, 10(7). https://doi.org/10.1371/journal.pbio.1001358

A Toxoplasma gondii pseudokinase inhibits host IRG resistance proteins. / Fleckenstein, Martin C.; Reese, Michael L.; Könen-Waisman, Stephanie; Boothroyd, John C.; Howard, Jonathan C.; Steinfeldt, Tobias.

In: PLoS Biology, Vol. 10, No. 7, 2012.

Research output: Contribution to journalArticle

Fleckenstein, MC, Reese, ML, Könen-Waisman, S, Boothroyd, JC, Howard, JC & Steinfeldt, T 2012, 'A Toxoplasma gondii pseudokinase inhibits host IRG resistance proteins.', PLoS Biology, vol. 10, no. 7. https://doi.org/10.1371/journal.pbio.1001358
Fleckenstein, Martin C. ; Reese, Michael L. ; Könen-Waisman, Stephanie ; Boothroyd, John C. ; Howard, Jonathan C. ; Steinfeldt, Tobias. / A Toxoplasma gondii pseudokinase inhibits host IRG resistance proteins. In: PLoS Biology. 2012 ; Vol. 10, No. 7.
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