VPS35

PF3D7_1110500 (VPS35) is a core subunit of the retromer complex in Plasmodium falciparum, functioning in endosome-to-Golgi retrograde membrane trafficking during asexual blood-stage growth (PMID:24587025, PMID:29654975). It localizes to a small number of punctate Rab7-positive endosomal structures situated close to, but distinct from, the Golgi apparatus, and these retromer-marked endosomes develop adjacent to nascent rhoptries, implicating VPS35-containing retromer in retrograde transport of PfSortilin and in rhoptry biogenesis (PMID:24587025). VPS35 physically assembles into a native retromer complex with the other retromer subunits, as detected by immunosensing surface plasmon resonance on parasite lysate (PMID:29654975). In Plasmodium berghei, the VPS35 ortholog undergoes PKG-dependent regulated phosphorylation in gliding ookinetes, linking it to cGMP/PKG-controlled trafficking during parasite motility (PMID:24594931). Beyond retromer membership, endosomal localization, and this ortholog phosphorylation, no further mechanistic detail on VPS35 has been characterized in the available corpus.

1. 2014 Medium

   Establishing where retromer acts in the parasite: the question of whether Plasmodium possesses a retromer-marked endosomal compartment was answered by placing VPS35-containing retromer at Rab7 puncta adjacent to the Golgi, defining a retrograde trafficking route toward rhoptry biogenesis.

   Evidence Fluorescence co-localization of retromer components with Rab7, brefeldin A treatment, and PfSortilin immunofluorescence in P. falciparum blood stages

   PMID:24587025

   Open questions at the time

   • Rhoptry biogenesis role inferred from adjacency, not from direct functional perturbation of VPS35
   • PfSortilin retrograde transport is proposed, not demonstrated by VPS35 depletion
   • No genetic knockout or conditional knockdown of VPS35 itself
2. 2014 Low

   Connecting VPS35 to a signaling pathway: the question of whether retromer trafficking is regulated during motility was partially addressed by showing the P. berghei ortholog is phosphorylated in a PKG-dependent manner in gliding ookinetes.

   Evidence Quantitative phosphoproteomics of P. berghei ookinetes with PKG inhibition, identifying phosphosite T690

   PMID:24594931

   Open questions at the time

   • Authors note regulated phosphosites are probably not direct PKG substrates; no direct kinase-substrate demonstration
   • No functional follow-up on the consequence of VPS35 phosphorylation
   • Finding is in P. berghei ookinetes, not the P. falciparum blood stage where localization was defined
3. 2018 Medium

   Confirming physical complex assembly: the question of whether VPS35 is genuinely incorporated into an assembled native retromer, rather than merely co-localizing, was addressed by capturing the intact complex from parasite lysate and detecting VPS35 within it.

   Evidence Immunosensing surface plasmon resonance using antibodies against retromer subunits including VPS35, on native P. falciparum lysate

   PMID:29654975

   Open questions at the time

   • Single method, single lab; no reciprocal pulldown or orthogonal validation specifically for VPS35
   • Does not define VPS35 stoichiometry, interaction interfaces, or subunit contacts
   • No structural model of the assembled complex

• Whether VPS35 is functionally required for PfSortilin retrograde transport, rhoptry biogenesis, or blood-stage viability remains unresolved, as no direct loss-of-function perturbation of VPS35 has been reported in the corpus.
• No conditional knockdown or knockout of VPS35 to test cargo transport or rhoptry phenotypes
• Functional consequence of PKG-dependent phosphorylation unknown
• No mapping of VPS35 cargo-recognition or membrane-recruitment mechanism in Plasmodium