PV1

PV1 (PF3D7_1129100) is an essential parasitophorous vacuole protein of Plasmodium falciparum that functions in the trafficking of exported virulence determinants across the parasite-host interface (PMID:28691708, PMID:21483790). Repeated failure to recover deletion mutants at an accessible locus establishes that PV1 is required for intra-erythrocytic survival (PMID:21483790). PV1 is a constituent of the parasitophorous-vacuole-localized EPIC (Exported Protein-Interacting Complex), and its inducible knockdown produces altered knob morphology, reduced cell rigidity, and decreased CD36-mediated cytoadherence, linking it functionally to host-cell remodeling (PMID:28691708). Beyond the vacuole, PV1 localizes to merozoite dense granules and partially co-localizes with the PTEX component EXP2, consistent with a role as a PTEX-associated accessory factor (PMID:29487358). Mechanistically, PV1 directly binds the exported protein PTP5 through a defined C-terminal PfPV1 High-affinity Region (PHR), and deletion of this region arrests PTP5 export, demonstrating that PV1-cargo engagement is required for substrate delivery (PMID:29487358). Recombinant PV1 assembles into tetramers and exhibits chaperone-like disaggregation activity in vitro, providing a biochemical basis for capturing PV-lumenal cargo prior to export (PMID:33207549). In P. berghei, deletion of the PV1 homologue attenuates parasite virulence in vivo, consistent with a conserved role in pathogenesis (PMID:28691708).

1. 2011 Medium

   Whether PV1 is dispensable was unknown; the inability to recover knockouts at a targetable locus established that PV1 is essential for blood-stage growth.

   Evidence Repeated gene-knockout attempts with control experiments verifying locus accessibility in P. falciparum

   PMID:21483790

   Open questions at the time

   • Negative-selection evidence only, no conditional system to define the stage or process requiring PV1
   • Single lab, single method
2. 2017 High

   The molecular context of PV1 was unresolved; defining the EPIC complex and its knockdown phenotypes established PV1 as a PV-resident factor for virulence determinant trafficking.

   Evidence Epitope-tagged co-immunoprecipitation defining the EPIC interactome plus inducible knockdown with knob morphology, cell rigidity, and CD36 binding readouts in P. falciparum

   PMID:28691708

   Open questions at the time

   • Does not identify which EPIC-associated substrates PV1 directly handles
   • Mechanism connecting EPIC to knob assembly not resolved
3. 2017 Medium

   Whether the PV1 role is conserved in vivo was untested; deletion of the P. berghei homologue attenuated virulence in a mouse model, extending the function beyond P. falciparum culture.

   Evidence Genetic deletion of the P. berghei homologue with in vivo mouse infection assay

   PMID:28691708

   Open questions at the time

   • Homologue only, molecular mechanism of attenuation not defined
   • Single study
4. 2018 Medium

   How PV1 relates to the export machinery was unclear; imaging placed PV1 in merozoite dense granules and adjacent to EXP2, positioning it as a candidate PTEX accessory molecule.

   Evidence Structured illumination microscopy with co-localization analysis in P. falciparum

   PMID:29487358

   Open questions at the time

   • Co-localization does not establish physical or functional coupling to PTEX
   • No functional validation of the accessory role
5. 2018 High

   It was unknown how PV1 engages export cargo; direct binding to PTP5 via the PHR region and export arrest upon PHR deletion established PV1 as a substrate-capturing factor required for export.

   Evidence Anti-PV1 co-immunoprecipitation, surface plasmon resonance for direct binding, and SIM of PTP5ΔPHR export arrest in P. falciparum

   PMID:29487358

   Open questions at the time

   • Only one cargo (PTP5) shown; breadth of substrate repertoire unknown
   • Structural basis of the PHR-PV1 interface not resolved
6. 2020 Medium

   The biochemical activity underlying cargo handling was undefined; recombinant PV1 forms tetramers with chaperone-like disaggregation activity, providing a mechanism for holding cargo before PTEX delivery.

   Evidence Recombinant protein purification, biophysical tetramer characterization, and in vitro chaperone/disaggregation substitution assays in P. falciparum

   PMID:33207549

   Open questions at the time

   • HSP101 interaction inferred, not directly demonstrated
   • In vitro reconstitution only; chaperone activity not validated in vivo
   • Single lab, limited replication

• How PV1 hands cargo to the PTEX translocon and whether its chaperone activity operates on the broader exportome in vivo remain unresolved.
• Direct PV1-HSP101/PTEX physical coupling not demonstrated
• Full substrate repertoire beyond PTP5 unknown
• In vivo relevance of tetramer/chaperone activity untested