BLEB

BLEB (PF3D7_0704300) is a transmembrane basal complex protein of Plasmodium falciparum that localizes as a ring structure to the basal complex during asexual schizogony and functions specifically in the transition to transmission stages (PMID:35972967, PMID:37400439). BLEB is dispensable for asexual replication, as its loss does not impair schizogony, but it is essential for gametocytogenesis: parasites lacking BLEB fail to expand the inner membrane complex (IMC) and cannot form mature gametocytes (PMID:35972967). Its localization as a basal complex ring makes BLEB a marker of basal complex structural integrity, and this ring becomes disorganized and fragmented in PfPPP8-deficient parasites, placing BLEB downstream of PfPPP8-dependent basal complex assembly (PMID:37400439). Super-resolution imaging further associates BLEB with a distinct plasma membrane region that is excluded from daughter cells and linked to the basal complex during asexual division (PMID:41706859). Proximity-biotinylation using BLEB as bait shows that during gametocyte formation it associates with a set of proteins distinct from the canonical asexual basal complex interactome, marking a novel subcellular compartment (PMID:35972967). Beyond these localization, interactome, and loss-of-function observations, the biochemical activity of BLEB itself has not been characterized in the available corpus.

1. 2022 High

   Established that a basal complex protein can have a role beyond asexual division by showing BLEB is required for sexual-stage development while being dispensable for asexual replication.

   Evidence Inducible knockout with phenotypic analysis of IMC expansion, gametocyte maturation, and asexual growth in P. falciparum

   PMID:35972967

   Open questions at the time

   • Molecular mechanism by which BLEB drives IMC expansion is unresolved
   • Whether the IMC defect is a direct or downstream consequence of BLEB loss is unknown
2. 2022 Medium

   Addressed which molecular neighborhood BLEB occupies during gametocytogenesis, revealing it engages a distinct interactome rather than the canonical asexual basal complex proteins, implicating a novel compartment.

   Evidence Proximity-dependent biotinylation (BioID) proteomics using BLEB as bait in stage II–III gametocytes

   PMID:35972967

   Open questions at the time

   • Partner identities and the proposed novel compartment are not independently validated
   • No reciprocal Co-IP confirming specific interactions
   • Functional relevance of identified partners to BLEB activity untested
3. 2023 Medium

   Placed BLEB within the basal complex assembly hierarchy by using it as a structural readout, showing its ring organization depends on PfPPP8.

   Evidence HaloTag-tagged BLEB in a PfPPP8-knockdown background analyzed by IFA and U-ExM in P. falciparum

   PMID:37400439

   Open questions at the time

   • Whether PfPPP8 acts directly on BLEB or on upstream scaffold components is unknown
   • The molecular determinants recruiting BLEB to the basal complex ring are undefined
4. 2023 Low

   Extended the BLEB-proximal proteome to include a novel subpellicular microtubule-associated protein, spatially connecting the basal complex region to the microtubule cytoskeleton in early gametocytes.

   Evidence Proximity-dependent biotinylation using BLEB as bait, identifying SPM3, in stage II–III gametocytes

   PMID:36625655

   Open questions at the time

   • Single proximity-biotinylation experiment with no reciprocal validation of the BLEB–SPM3 association
   • Whether BLEB and SPM3 are in a functional complex is untested
5. 2026 Medium

   Refined the subcellular assignment of BLEB, associating it with a plasma membrane region excluded from daughter cells during asexual division, implicating a role in daughter cell formation.

   Evidence Expansion microscopy and DNA-PAINT super-resolution imaging in P. falciparum

   PMID:41706859

   Open questions at the time

   • Functional consequence of the BLEB-associated membrane for daughter cell formation not tested by perturbation
   • How this membrane region relates to the gametocyte-essential role is unresolved

• The intrinsic molecular activity of BLEB and the mechanism linking its basal complex/membrane localization to IMC expansion during gametocytogenesis remain unknown.
• No biochemical or enzymatic activity defined for BLEB
• No structural model or membrane-topology determination
• Direct effectors mediating IMC expansion not identified