ATP2

PF3D7_1219600 (ATP2) is a P-type ATPase of P. falciparum expressed during the intraerythrocytic cycle and required in the late stages of asexual development (PMID:7851389). Biochemical reconstitution of the P. chabaudi ortholog establishes ATP2 as a lipid-stimulated P4-ATPase (flippase): purified in complex with a Plasmodium Cdc50 subunit, its ATPase activity is stimulated by phosphatidylserine or phosphatidylethanolamine and further upregulated by phosphatidylinositol 4-phosphate (PMID:33372863). In P. falciparum blood stages ATP2 localizes to the parasite plasma membrane and drives ATP-dependent internalization of a phosphatidylserine analogue (NBD-PS), with overexpression increasing and knockdown reducing uptake — defining ATP2 as a major phosphatidylserine flipping mechanism at the parasite surface (PMID:41144577). ATP2 associates with the chaperone CDC50C, whose conditional disruption is essential for trophozoite maturation, and the CDC50C–ATP2 complex influences endocytosis of host hemoglobin and hemozoin formation (PMID:35862778). ATP2 expression level modulates parasite sensitivity to several antimalarial compounds, and its copy number amplification is selected under drug pressure, marking it as a candidate drug target or resistance determinant (PMID:41144577, PMID:39899599).

1. 1995 Low

   Established that ATP2 is a distinct P-type ATPase gene expressed in blood-stage parasites, providing the first sequence-level identification and a hint of a late-stage asexual requirement.

   Evidence Molecular cloning, sequencing, and phylogenetic/expression analysis in P. falciparum

   PMID:7851389

   Open questions at the time

   • No biochemical activity assay to define substrate or transport function
   • Late-stage requirement inferred from expression, not from genetic perturbation
2. 2021 High

   Resolved the biochemical identity of ATP2 as a lipid-stimulated P4-ATPase requiring a Cdc50 partner, moving it from a predicted ATPase to a functionally defined flippase.

   Evidence Recombinant expression and purification of the PcATP2/PcCdc50B complex with in vitro ATPase assays using defined lipids (P. chabaudi)

   PMID:33372863

   Open questions at the time

   • Direct demonstration of lipid translocation (as opposed to lipid-stimulated ATP hydrolysis) not shown in this system
   • Performed on the P. chabaudi ortholog, not P. falciparum ATP2
3. 2022 Medium

   Identified CDC50C as the P. falciparum ATP2 binding partner and linked the complex to trophozoite maturation and hemoglobin endocytosis, connecting flippase activity to a specific cellular process.

   Evidence Co-immunoprecipitation and DiCre conditional disruption with phenotypic analysis of hemoglobin endocytosis and hemozoin formation in P. falciparum

   PMID:35862778

   Open questions at the time

   • Essentiality shown for CDC50C disruption; direct ATP2 loss-of-function phenotype not established here
   • Mechanistic link between lipid flipping and endocytosis not resolved
4. 2022 Low

   Proposed structural determinants of ATP2 lipid recognition, including a candidate phosphatidylinositol allosteric site consistent with the PI4P stimulation seen biochemically.

   Evidence Coarse-grained molecular dynamics simulation of PcATP2 in a heterogeneous membrane (P. chabaudi ortholog)

   PMID:35877905

   Open questions at the time

   • Computational prediction with no experimental validation of the proposed binding site or residues
   • Based on the P. chabaudi ortholog
5. 2025 High

   Demonstrated in P. falciparum that ATP2 sits at the plasma membrane and functions as a major phosphatidylserine internalization mechanism, and that its expression level tunes sensitivity to specific antimalarial compounds independently of parasite pH.

   Evidence Fluorescence localization, reciprocal overexpression/knockdown, NBD-PS uptake assays, drug sensitivity and cytosolic pH measurements in P. falciparum

   PMID:41144577

   Open questions at the time

   • Whether the tested compounds directly inhibit ATP2 catalysis versus acting through an ATP2-dependent pathway is not resolved
   • Directionality and full lipid substrate range at the P. falciparum surface not exhaustively defined
6. 2025 Medium

   Genetic evidence from resistance selection implicated ATP2 as a drug target or resistance determinant, reinforcing its therapeutic relevance.

   Evidence In vitro resistance evolution with compound 22, whole-genome sequencing, copy-number analysis, and validation with pre-existing pfatp2-amplified lines in P. falciparum 3D7

   PMID:39899599

   Open questions at the time

   • Copy number amplification is indirect evidence for target engagement; direct binding/inhibition not shown
   • Whether amplification confers resistance through overexpression alone is not fully dissected

• How ATP2-mediated phosphatidylserine flipping mechanistically drives hemoglobin endocytosis and trophozoite maturation, and whether antimalarial compounds engage ATP2 directly, remain open.
• No structural model validated experimentally for P. falciparum ATP2
• Causal link between flippase activity and endocytosis unestablished
• Direct compound–ATP2 binding not demonstrated