PLoS ONE (Jan 2011)

Identification of Toxoplasma gondii cAMP dependent protein kinase and its role in the tachyzoite growth.

  • Hitomi Kurokawa,
  • Kentaro Kato,
  • Tatsuya Iwanaga,
  • Tatsuki Sugi,
  • Atsushi Sudo,
  • Kyousuke Kobayashi,
  • Haiyan Gong,
  • Hitoshi Takemae,
  • Frances C Recuenco,
  • Taisuke Horimoto,
  • Hiroomi Akashi

DOI
https://doi.org/10.1371/journal.pone.0022492
Journal volume & issue
Vol. 6, no. 7
p. e22492

Abstract

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cAMP-dependent protein kinase (PKA) has been implicated in the asexual stage of the Toxoplasma gondii life cycle through assaying the effect of a PKA-specific inhibitor on its growth rate. Since inhibition of the host cell PKA cannot be ruled out, a more precise evaluation of the role of PKA, as well as characterization of the kinase itself, is necessary.The inhibitory effects of two PKA inhibitors, H89, an ATP-competitive chemical inhibitor, and PKI, a substrate-competitive mammalian natural peptide inhibitor, were estimated. In the in vitro kinase assay, the inhibitory effect of PKI on a recombinant T. gondii PKA catalytic subunit (TgPKA-C) was weaker compared to that on mammalian PKA-C. In a tachyzoite growth assay, PKI had little effect on the growth of tachyzoites, whereas H89 strongly inhibited it. Moreover, T. gondii PKA regulatory subunit (TgPKA-R)-overexpressing tachyzoites showed a significant growth defect.Our data suggest that PKA plays an important role in the growth of tachyzoites, and the inhibitory effect of substrate-competitive inhibitor PKI on T. gondii PKA was low compared to that of the ATP competitive inhibitor H89.