VPS4

PF3D7_1457500 (VPS4) is a Mg²⁺-dependent AAA-ATPase of P. falciparum whose ATP hydrolysis activity drives multivesicular body biogenesis and is required for intraerythrocytic proliferation (PMID:15252121, PMID:41957628). The endogenous protein resides in the cytoplasm of trophozoites, and blocking ATP hydrolysis relocalizes it from the cytosol onto large vesicular structures, demonstrating that its catalytic cycle governs its normal cytosolic distribution (PMID:15252121). Expression of ATP-hydrolysis- or ATP-binding-defective VPS4 generates enlarged cholesterol-enriched multivesicular bodies, placing the enzyme at the core of parasite endosomal/MVB formation (PMID:15252121). In vitro, purified VPS4 is a bona fide AAA-ATPase (optimal at pH 7.5/37°C, Mg²⁺-dependent) whose activity depends on the canonical catalytic residues D213 and E214 and on the species-specific residues T161 and I288, and is stimulated by the cofactor PfVta1 (PMID:41957628). Conditional knockdown reduces asexual progeny by 84% and merozoite numbers, establishing essentiality for blood-stage proliferation, and additionally lowers gametocyte conversion by 46% without impairing subsequent maturation, implicating VPS4 in efficient sexual conversion (PMID:41957628). Beyond these findings, no further binding partners or downstream substrates of PF3D7_1457500 have been characterized in the available corpus.

1. 2004 Medium

   To learn whether VPS4's ATPase cycle controls its subcellular behavior, its localization was probed in normal versus catalytically dead states, establishing that ATP hydrolysis maintains its cytosolic distribution.

   Evidence Immunofluorescence of endogenous protein plus transient expression of ATPase-dead and ATP-binding-dead mutants in P. falciparum, T. gondii, and COS cells

   PMID:15252121

   Open questions at the time

   • Dominant-negative relocalization does not identify the membranes/vesicles VPS4 acts on directly
   • No in situ validation of MVB engagement in native parasite cytosol
2. 2004 Medium

   To connect VPS4 to an organellar process, dominant-negative mutants were tested for effects on membrane compartments, showing that VPS4 function is required for multivesicular body formation.

   Evidence Transient expression of dominant-negative mutants in COS cells and T. gondii with cholesterol staining and early-endosome marker co-localization

   PMID:15252121

   Open questions at the time

   • MVB phenotype demonstrated largely in heterologous systems rather than natively in P. falciparum
   • No identification of cargo sorted through these MVBs
3. 2026 Medium

   To move from dominant-negative inference to loss-of-function, conditional knockdown tested whether VPS4 is needed for parasite growth, establishing it as essential for intraerythrocytic proliferation.

   Evidence CRISPR-Cas9 conditional knockdown in synchronized 3D7/NF54 cultures with Western blot and IFA confirmation

   PMID:41957628

   Open questions at the time

   • Single lab, single study
   • Proliferation defect not resolved to a specific step in the asexual cycle beyond reduced merozoite numbers
4. 2026 Medium

   To test a role beyond asexual growth, knockdown was assessed across sexual commitment, showing VPS4 is required for efficient conversion to gametocytes but not for their later maturation.

   Evidence CRISPR-Cas9 conditional knockdown with gametocytogenesis conversion-rate assay

   PMID:41957628

   Open questions at the time

   • Mechanism linking VPS4 ATPase activity to commitment signaling is unknown
   • Single study
5. 2026 High

   To define the enzyme biochemically, purified VPS4 was subjected to kinetics and active-site mutagenesis, confirming Mg²⁺-dependent AAA-ATPase activity requiring catalytic residues D213/E214.

   Evidence In vitro purification, enzyme kinetics (Vmax 2.23 U/mg, Km 0.086 mM), and site-directed mutagenesis of D213/E214

   PMID:41957628

   Open questions at the time

   • No structural model of the ATPase or its oligomeric assembly
   • Physiological substrates/machinery acted upon not defined
6. 2026 Medium

   To probe parasite-specific features exploitable for selectivity, non-canonical residues were mutated, showing T161 and I288 are required for enzymatic activity.

   Evidence Site-directed mutagenesis with in vitro ATPase assays

   PMID:41957628

   Open questions at the time

   • Structural basis for how T161/I288 support catalysis is not established
   • Single study
7. 2026 Medium

   To identify a functional partner regulating activity, the cofactor PfVta1 was tested, establishing it as an activator of VPS4 ATPase activity.

   Evidence In vitro ATPase kinetics with and without recombinant PfVta1

   PMID:41957628

   Open questions at the time

   • Physical basis and stoichiometry of the VPS4–PfVta1 interaction not defined
   • In vivo dependence of VPS4 function on PfVta1 not tested

• It remains unknown what protein substrates VPS4 disassembles, how its ATPase cycle is structurally coupled to MVB membrane remodeling, and how these activities mechanistically drive both proliferation and sexual conversion.
• No structural model or oligomeric assembly defined
• No identified substrate complex acted upon by VPS4
• Mechanistic link between ATPase activity and the sexual-conversion phenotype unresolved