IMC1e

IMC1e (PF3D7_0304100) is an alveolin-family, intermediate filament-like structural protein of the Plasmodium inner membrane complex (IMC) that is assembled into the subpellicular network (SPN) concurrent with pellicle development across the zoite stages of the parasite (PMID:25185663). In P. berghei, GFP-tagged PbIMC1e localizes to the SPN in merozoites, ookinetes, and sporozoites, is expressed exclusively from the maternal allele in sexual stages, and repeated failure to disrupt the gene by double-crossover recombination indicates it is essential for asexual blood-stage development (PMID:25185663). In P. falciparum, PfIMC1e is recruited to the basal complex in a sequential, PfIMC1f-dependent manner; its alveolin domain alone is insufficient for this recruitment, and a region outside the alveolin domain is critical, while alveolin domains mediate compartment-specific alveolin-alveolin interactions but are not interchangeable between family members (PMID:41019501). Beyond its structural role in the SPN and basal complex, no catalytic activity or additional mechanistic detail for IMC1e has been characterized in the available corpus.

1. 2014 Medium

   Establishing when and where IMC1e acts required localizing the protein and testing its necessity; GFP tagging placed it in the subpellicular network at the time of pellicle formation across zoite stages and identified it as essential for asexual growth.

   Evidence GFP tagging with live imaging and attempted double-crossover gene disruption in P. berghei

   PMID:25185663

   Open questions at the time

   • Essentiality is inferred from repeated failed disruption rather than a conditional knockdown/knockout phenotype
   • The molecular consequence of IMC1e loss on SPN integrity was not measured
   • Maternal-allele-only expression in sexual stages was described but its functional significance was not tested
2. 2014 Low

   Classifying IMC1e as a genuine SPN structural component required identifying its defining sequence architecture; repeat analysis found the tandem 12-amino-acid alveolin repeats characteristic of intermediate filament-like family members.

   Evidence Computational structural-repeat prediction (HHrepID) benchmarked against known alveolins, P. berghei

   PMID:25475193

   Open questions at the time

   • Purely computational — no experimental validation that the predicted repeats form filaments or mediate assembly
   • Does not link the repeat to any specific interaction or localization determinant
3. 2022 Low

   Confirming IMC1e as part of the IMC proteome in an independent species and stage placed it within the broader IMC compartment beyond single-lab imaging.

   Evidence TurboID proximity-labeling proteomics of the schizont-stage IMC in P. yoelii

   PMID:35775739

   Open questions at the time

   • Proteome-level identification only — no IMC1e-specific functional or interaction data
   • Proximity labeling does not distinguish direct partners from compartment neighbors
4. 2025 Medium

   How IMC1e is targeted to a specific IMC sub-compartment was unresolved; domain-swap and truncation dissection showed its recruitment to the basal complex is sequential and depends on IMC1f, with a determinant lying outside the alveolin domain.

   Evidence Fluorescence microscopy of domain-swap and truncation mutants plus alveolin-alveolin interaction assays in P. falciparum

   PMID:41019501

   Open questions at the time

   • The specific non-alveolin region and its binding partner at the basal complex are not defined
   • The functional consequence of mislocalizing IMC1e was not assessed
   • Whether IMC1e-IMC1f interaction is direct is not established

• The catalytic or structural mechanism by which IMC1e contributes to SPN and basal complex architecture, and the identity of the non-alveolin recruitment determinant and its direct partners, remain open.
• No direct binding partner of IMC1e has been biochemically defined
• No structural model of IMC1e filament assembly
• No conditional loss-of-function phenotype quantifying its contribution to pellicle integrity