RAB11a

RAB11a (PF3D7_1320600) is a small GTPase with confirmed intrinsic GTPase activity (PMID:26773071) that governs membrane and cargo trafficking during Plasmodium cell division and morphogenesis (PMID:19165333, PMID:32463831). In P. falciparum asexual blood stages it executes the final step of cytokinesis by delivering new plasma membrane to nascent daughter parasites: functional RAB11a associates with the glideosome motor component MTIP/MLC1, and its loss produces daughter cells with an incompletely formed Inner Membrane Complex, phenocopied by a myosin A tail dominant-negative mutant (PMID:19165333). In mosquito stages, RAB11a orthologs drive morphological maturation: in P. berghei it is essential for the zygote-to-ookinete transition and for secretion and distribution of microneme cargo, without affecting fertility, meiosis, mitosis, or apical/IMC polarity establishment (PMID:32463831), and in P. yoelii ookinetes it acts as a cargo receptor for subpellicular-microtubule dynein-driven transport through a DHC3-dependent interaction, with its disruption impairing ookinete morphogenesis and apical organelle formation (PMID:39366980). Structurally, Rab11a engages PI4KIIIβ through an interface distinct from the switch regions normally used by GTPase effectors, permitting simultaneous recruitment of Rab11a and its effectors such as FIP3 on PI4P-enriched membranes (PMID:24876499).

1. 2003 Medium

   Establishing that PfRAB11A occupies a subcellular compartment distinct from other parasite Rab GTPases was the first step toward assigning it a dedicated trafficking role.

   Evidence Specific antisera and immunolocalization comparing PfRab11A versus PfRab1A in infected erythrocytes

   PMID:12657463

   Open questions at the time

   • No functional consequence of the localization was tested
   • Does not identify the trafficking pathway or cargo
2. 2009 High

   The question of what completes apicomplexan cytokinesis was answered by placing RAB11a at the final membrane-delivery step, linking vesicular trafficking to the glideosome motor machinery.

   Evidence Dominant-negative RAB11a expression, Co-IP with MTIP/MLC1, IMC imaging, and genetic epistasis with a myosin A tail mutant

   PMID:19165333

   Open questions at the time

   • Direct membrane cargo carried by RAB11a not molecularly defined
   • Nature of the RAB11a–MTIP association (direct vs. indirect) not resolved
3. 2014 High

   How Rab11a can bind an effector kinase and its downstream effectors at once was answered structurally, revealing a switch-region-independent interface with PI4KIIIβ.

   Evidence X-ray crystallography of PI4KIIIβ–Rab11a binary and PI4KIIIβ–Rab11a–FIP3 ternary complexes

   PMID:24876499

   Open questions at the time

   • In vivo relevance of this interface to parasite trafficking not demonstrated
   • Whether the PI4KIIIβ interaction operates in the same pathway as MTIP-linked cytokinesis is untested
4. 2016 Medium

   Whether PfRAB11a is a bona fide enzyme was confirmed by direct demonstration of intrinsic GTPase activity, and initial chemical-probe binders were identified.

   Evidence ESI-FTICR-MS fragment screening plus an orthogonal GTPase enzyme activity assay

   PMID:26773071

   Open questions at the time

   • Identified binders are weak with no demonstrated inhibitory or cellular effect
   • GDP/GTP cycling regulators (GEF/GAP) not identified
5. 2020 High

   The role of RAB11A in mosquito stages was defined by showing it is required specifically for zygote-to-ookinete morphogenesis and microneme cargo delivery rather than for the preceding sexual/mitotic events.

   Evidence Promoter-swap conditional downregulation of PbRAB11A with morphology, polarity-marker, microneme-secretion, and transmission readouts

   PMID:32463831

   Open questions at the time

   • Molecular identity of the delivered plasma membrane/microneme cargo not defined
   • Effector or motor partner in ookinetes not identified in this study
6. 2021 Medium

   This study concerns host hepatocyte Rab11a co-opted by the parasite, not parasite RAB11a, establishing that parasite-induced host Golgi fragmentation and liver-stage development depend on host Rab11a function.

   Evidence Dominant-negative Rab GTPase expression in host hepatocytes with live imaging of Golgi fragmentation and parasite developmental assays

   PMID:34013963

   Open questions at the time

   • Attribution is to host-cell Rab11a, not the parasite's PF3D7_1320600
   • Does not establish a role for parasite RAB11a in the liver stage
7. 2024 Medium

   How RAB11A links cargo to the cytoskeletal transport machinery in ookinetes was answered by identifying it as a DHC3-dependent cargo label for subpellicular-microtubule dynein-driven transport.

   Evidence Co-IP of RAB11A with DHC3, genetic disruption, ookinete morphogenesis/apical-organelle imaging, and mosquito infection assays with DHC3 epistasis

   PMID:39366980

   Open questions at the time

   • Directness of the RAB11A–DHC3 interaction not structurally established
   • How microtubule-based transport integrates with the MTIP/glideosome pathway seen in blood stages is unknown

• The molecular cargo carried by parasite RAB11a and the GEF/GAP and effector network that spatially controls its GTP cycling across life-cycle stages remain undefined.
• No RAB11a-specific membrane cargo molecularly identified
• No parasite GEF/GAP regulators characterized
• Reconciliation of glideosome-linked (blood stage) and dynein-linked (ookinete) roles unresolved