RAB7

PF3D7_0903200 (RAB7) is a Mg2+-dependent GTPase that marks a late endosomal compartment in Plasmodium falciparum and coordinates endosomal protein sorting and autophagosome maturation (PMID:24025672, PMID:24587025, PMID:32512169). RAB7 localizes to a small number of punctate endosomal structures distinct from the Golgi—resistant to brefeldin A redistribution—positioned near the Golgi, nascent rhoptries, and the digestive vacuole (PMID:24587025). At this compartment RAB7 physically interacts with the retromer subunit PfVPS26, and its GTPase activity is required for retromer complex assembly: the specific Rab7 GTPase inhibitor CID 1067700 prevents retromer assembly and inhibits parasite growth, while chemical disruption of the digestive vacuole causes retromer disassembly, linking retromer integrity to digestive vacuole function (PMID:32512169). In parallel, upon amino acid starvation RAB7-labeled vesicles increasingly colocalize with PfATG8-positive autophagosomes, and the co-labeled double-membrane structures become acidified, indicating RAB7-mediated maturation of autophagosomes and their routing through the endosomal system to the food vacuole (PMID:24025672). Beyond these roles in retromer assembly and autophagosome maturation, no further mechanistic detail for PF3D7_0903200 has been characterized in the available corpus.

1. 2013 Medium

   To determine whether RAB7 participates in autophagy, its relationship to the autophagosome marker PfATG8 was tested, establishing RAB7 as a mediator of autophagosome maturation and delivery to the food vacuole.

   Evidence Fluorescence colocalization, acidification assay, and immuno-electron microscopy under amino acid starvation in P. falciparum

   PMID:24025672

   Open questions at the time

   • Colocalization and acidification are correlative; RAB7 depletion was not used to show autophagosome maturation is RAB7-dependent
   • The molecular effectors linking RAB7 to ATG8-positive membranes are not identified
   • Whether the same RAB7 pool serves both autophagy and endosomal sorting is not resolved
2. 2014 Medium

   To define the compartment RAB7 marks, its localization was compared against retromer and Golgi markers, showing RAB7 labels a distinct endosomal compartment near the Golgi and nascent rhoptries.

   Evidence Confocal co-localization with organelle markers and brefeldin A perturbation in P. falciparum

   PMID:24587025

   Open questions at the time

   • A functional role in rhoptry biogenesis is inferred from proximity, not demonstrated
   • The identity of cargo sorted at this compartment is not established
   • Colocalization with retromer does not by itself demonstrate physical interaction
3. 2020 High

   To test whether RAB7 functionally drives retromer assembly, its interaction with PfVPS26, its GTPase activity, and the effect of inhibiting that activity were examined, establishing RAB7 GTPase activity as required for retromer complex assembly and parasite growth.

   Evidence Co-immunoprecipitation, in vitro Mg2+-dependent GTPase assay, digestive-vacuole disruption (chloroquine, compound 5f), and Rab7 inhibitor CID 1067700 with growth assay in P. falciparum

   PMID:32512169

   Open questions at the time

   • The GEF/GAP that regulate RAB7 nucleotide cycling are not identified
   • The full set of retromer and endosomal cargo dependent on RAB7 is not defined
   • How digestive vacuole integrity is mechanistically coupled to retromer assembly is not resolved

• How RAB7 nucleotide cycling is regulated, which effectors and cargo it engages, and whether its autophagy and retromer roles are mechanistically linked remain unresolved.
• No RAB7 GEF or GAP identified in the corpus
• No genetic loss-of-function (conditional knockout/knockdown) of RAB7 reported
• No structural model of RAB7 or its complex with PfVPS26