CDPK7

TgCDPK7 is an essential calcium-dependent protein kinase in Toxoplasma gondii that drives intracellular replication by supporting the division cycle rather than the invasion or egress machinery (PMID:24011186). Its depletion causes pronounced defects in parasite division while leaving motility, egress, and microneme exocytosis intact, marking it as specifically required for endodyogeny (PMID:24011186). Mechanistically, TgCDPK7 maintains centrosome integrity at the initiation of endodyogeny, and its loss disrupts the polarity of daughter cell budding and the fate of kinetochore-associated proteins (PMID:24011186). TgCDPK7 phosphorylates TgRab11a, and this phosphorylation is critical for intracellular development and protein trafficking (PMID:33635921), while the kinase also regulates vesicular trafficking and phosphatidylethanolamine levels (PMID:33635921). Complete gene deletion confirms that TgCDPK7 is essential for growth in both type 1 (RH) and type 2 (ME49) backgrounds (PMID:26755159).

1. 2013 Medium

   Establishing which stage of the lytic cycle requires TgCDPK7 answered whether this kinase acts in invasion/egress or in replication, localizing its function to intracellular division.

   Evidence Conditional knock-down with phenotypic readouts for division, motility, egress, and microneme exocytosis in T. gondii

   PMID:24011186

   Open questions at the time

   • Does not identify direct substrates or molecular partners
   • Mechanism linking the kinase to the division defect unresolved
2. 2013 Medium

   Pinpointing the subcellular structures perturbed on depletion showed TgCDPK7 is required for centrosome function at the onset of endodyogeny, explaining the division defect.

   Evidence Conditional knock-down with immunofluorescence of centrosome and kinetochore markers during replication

   PMID:24011186

   Open questions at the time

   • No molecular target at the centrosome identified
   • How the kinase controls budding polarity mechanistically is unknown
3. 2016 High

   Complete gene deletion resolved whether the growth requirement was strain-restricted, confirming essentiality across type 1 and type 2 backgrounds.

   Evidence CRISPR/Cas9 knockout with in vitro growth assay in RH and ME49

   PMID:26755159

   Open questions at the time

   • Does not address the molecular basis of essentiality
   • No in vivo/virulence assessment
4. 2021 High

   Identifying a direct substrate answered how the kinase exerts its function, linking TgCDPK7 to TgRab11a phosphorylation as a driver of intracellular development and trafficking.

   Evidence Quantitative phosphoproteomics of cdpk7-null parasites with biochemical and cellular validation of TgRab11a phosphorylation

   PMID:33635921

   Open questions at the time

   • Phosphosite(s) on TgRab11a and their functional impact not fully mapped
   • Whether TgRab11a phosphorylation accounts for the centrosome defect is unresolved
5. 2021 Medium

   Coupling lipidomics to the null mutant connected the kinase to membrane biogenesis, showing TgCDPK7 regulates vesicular trafficking and phosphatidylethanolamine levels.

   Evidence Lipidomic analysis with biochemical and cellular studies in TgCDPK7-deficient parasites

   PMID:33635921

   Open questions at the time

   • Direct enzymatic link between the kinase and PE synthesis enzymes not established
   • Relationship between the trafficking defect and altered PE unresolved

• How the calcium signal is sensed and how substrate phosphorylation is coordinated across centrosome integrity, Rab11a-dependent trafficking, and lipid metabolism remains unresolved.
• No structural model of the kinase
• Upstream calcium-signaling context uncharacterized
• Full substrate repertoire beyond TgRab11a not defined