AIP

PF3D7_1136700 (AIP) is a rhoptry-associated protein of Plasmodium falciparum that functions in red blood cell invasion (PMID:31877322). AIP localizes to the rhoptries, and its conditional mislocalization produces a defect in host cell invasion, establishing an essential role in this process (PMID:31877322). AIP is recruited to the cytosolic face of the rhoptry membrane through direct dependence on the armadillo-repeat protein ARO: structure-guided mutations in the ARO armadillo repeats mislocalize AIP, indicating that its rhoptry targeting requires the ARO interaction (PMID:31877322). This ARO–AIP relationship is conserved across apicomplexans, as P. falciparum ARO functionally complements ARO depletion in Toxoplasma gondii and engages the same partners including AIP; in T. gondii, AIP acts upstream of adenylate cyclase β rhoptry association, since AC β is lost from the rhoptries in the absence of AIP (PMID:26769898). Beyond this ARO-dependent rhoptry-targeting and invasion role, the AIP proximal interactome and its molecular activity have not been further characterized in the available corpus (PMID:31877322).

1. 2016 Medium

   Before this work it was unknown how adenylate cyclase β is anchored at the rhoptry; the study placed AIP upstream of ACβ rhoptry association and established conservation of the ARO–AIP module across apicomplexans.

   Evidence Conditional depletion of AIP in T. gondii with immunofluorescence, plus functional complementation of T. gondii ARO depletion by P. falciparum ARO

   PMID:26769898

   Open questions at the time

   • The P. falciparum AIP–ACβ relationship is inferred from cross-species complementation, not directly demonstrated in P. falciparum
   • The direct biochemical nature of the AIP–ACβ link is not resolved
   • No structural model of the AIP–ARO interface
2. 2019 Medium

   To determine AIP's role in P. falciparum, conditional mislocalization was used to show AIP resides at the rhoptries and is required for red blood cell invasion, defining its function in the parasite's own life cycle.

   Evidence DiCre-based conditional mislocalization with fluorescence microscopy and an invasion assay in P. falciparum

   PMID:31877322

   Open questions at the time

   • The molecular step of invasion that AIP contributes to is not defined
   • Whether the invasion defect is direct or secondary to loss of other rhoptry components is unresolved
3. 2019 Medium

   It was unclear what recruits AIP to the rhoptry; structure-guided ARO mutagenesis showed AIP targeting depends on direct interaction with ARO, defining the recruitment mechanism.

   Evidence Structure-guided mutagenesis of PfARO armadillo repeats with fluorescence microscopy of AIP localization in P. falciparum

   PMID:31877322

   Open questions at the time

   • The AIP residues mediating the ARO contact are not mapped
   • Direct binding was inferred from localization rather than reconstituted biochemically
4. 2019 Low

   To place AIP in its molecular neighborhood, proximity biotinylation was used to sketch the AIP proximal interactome at the rhoptry.

   Evidence Proximity-based biotinylation (BioID) in P. falciparum

   PMID:31877322

   Open questions at the time

   • Individual proximity hits were not validated by reciprocal or orthogonal interaction assays
   • Proximity labeling does not distinguish direct partners from bystanders
5. 2022 Low

   AIP was situated among the rhoptry cytosolic-surface proteome, reinforcing its localization to the cytosolic face of the rhoptry membrane.

   Evidence Cited as an established prior result during characterization of the rhoptry cytosolic surface in P. falciparum

   PMID:35140336

   Open questions at the time

   • No new primary experiment for AIP was performed in this study
   • Membrane topology and mode of membrane association of AIP are not defined

• The molecular activity of AIP itself, its validated direct binding partners beyond ARO, and the mechanistic step of invasion it enables remain unknown.
• No enzymatic or biochemical activity assigned to AIP
• Direct AIP interactome not validated beyond the ARO dependence
• Precise contribution of AIP to the invasion mechanism unresolved