Affinage · Plasmodium

P52

PF3D7_0404500 · 6-cysteine protein P52

Annotated
2026-09-07
25 papers in source corpus 9 papers cited in narrative 10 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

P52 (PF3D7_0404500) is a 6-cysteine s48/45 family protein essential for the transition from hepatocyte invasion to intrahepatocytic development in Plasmodium sporozoites (PMID:16103357, PMID:18958160). In P. berghei and P. falciparum, P52-deficient sporozoites glide, traverse, and invade hepatocytes normally but arrest developmentally immediately after invasion (PMID:16103357, PMID:18958160). This arrest reflects a failure to establish a replication-permissive parasitophorous vacuole: in P. yoelii, deletion of P52 alone, of P36 alone, or of both together yields parasites that reside free in the host cytoplasm or nucleoplasm without forming a PV, placing P52 and P36 in the same essential invasion pathway (PMID:17517871, PMID:30547015). Mechanistically, P52 partially co-localizes with P36 in sporozoite micronemes and forms a heterodimeric complex with it; upon sporozoite stimulation only P36 is secreted while putatively GPI-anchored P52 is retained, supporting a model in which P52 acts as a membrane-tethered scaffold that presents secretion-competent P36 to the host cell (PMID:30547015). Structural analysis indicates a head-to-tail P36-P52 heterodimer whose membrane-distal face constitutes an antibody-accessible site that can be blocked to inhibit invasion (PMID:42418521). The host-cell effector of this pathway is the hepatocyte EphA2 receptor, whose loss phenocopies loss of P52/P36 (PMID:26612952). Beyond its role in this microneme complex and hepatocyte-invasion pathway, no additional biochemical function of P52 has been characterized in the available corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2005 High

    Established that P52 acts after sporozoite entry rather than during invasion itself, resolving whether the protein functions in cell penetration or in subsequent development.

    Evidence Targeted gene knockout in P. berghei with in vivo and in vitro liver-stage assays

    PMID:16103357

    Open questions at the time
    • Molecular reason for developmental arrest not defined
    • No partner or host receptor identified
    • Phenotype shown only in rodent parasite
  2. 2007 High

    Defined the cell-biological lesion behind the arrest by showing that P52 (with P36) is required to build the parasitophorous vacuole, so parasites without it lie free in the host cell.

    Evidence Simultaneous double-gene deletion in P. yoelii with IFA and electron microscopy of infected hepatocytes in vitro and in vivo

    PMID:17517871

    Open questions at the time
    • Did not separate P52 and P36 individual contributions
    • Molecular mechanism of PV formation unaddressed
    • No structural or interaction data
  3. 2008 High

    Extended the invasion-competent, development-defective phenotype to the human parasite, showing P52's role is conserved and relevant to human infection.

    Evidence Double-crossover gene disruption in P. falciparum with in vitro growth assay in primary human hepatocytes

    PMID:18958160

    Open questions at the time
    • Mechanism of arrest not defined in P. falciparum
    • No interaction partners tested
    • PV-formation defect not directly imaged
  4. 2008 Medium

    Placed P52 within a post-transcriptional regulatory hierarchy by showing SAP1 is required for its expression, distinguishing stage-specific from constitutive sporozoite proteins.

    Evidence SAP1 knockout with downstream expression analysis (RT-PCR) in P. yoelii

    PMID:18466298

    Open questions at the time
    • Mechanism of SAP1 control not resolved
    • Does not address P52 protein function
    • Single-lab epistasis result
  5. 2012 Medium

    Provided a structural framework for the s48/45 domain shared by P52, revealing a beta-sandwich fold related to Toxoplasma SRS antigens and ephrins.

    Evidence NMR structure of the Pf12 s48/45 domain, a representative family member, with inference to P52 by domain homology

    PMID:22493233

    Open questions at the time
    • Structure determined for Pf12, not P52 itself
    • No experimental structure of P52
    • Functional consequence of the fold for P52 not shown
  6. 2015 Medium

    Identified the host-side effector of the pathway by showing hepatocyte EphA2 loss phenocopies P52/P36 loss, linking the parasite complex to a defined receptor.

    Evidence Genetic EphA2 deletion in mice with sporozoite infection assays and phenotype comparison in P. yoelii

    PMID:26612952

    Open questions at the time
    • Direct interaction demonstrated for P36, not P52
    • Phenocopy is correlative for P52 specifically
    • Single-lab result in rodent model
  7. 2018 High

    Resolved P52's molecular role by demonstrating a micronemal P36-P52 complex in which only P36 is secreted, casting P52 as a retained scaffold, and showing P52 alone is sufficient for the PV defect.

    Evidence Co-IP, mCherry co-localization imaging, stimulation-secretion assay, and single-gene deletion in P. yoelii

    PMID:30547015

    Open questions at the time
    • GPI anchoring of P52 inferred, not directly demonstrated
    • How P52 scaffolding enables P36-host engagement not resolved at molecular level
    • Shown in rodent parasite only
  8. 2023 Low

    Suggested P52 participates in a larger invasion assembly by detecting interaction of the B9 beta-propeller with P52 in a heterologous system.

    Evidence Co-expression/pulldown in a heterologous expression system for P. falciparum proteins

    PMID:36761022

    Open questions at the time
    • Single heterologous pulldown, not validated in parasites
    • P52-specific interaction not independently confirmed
    • Functional significance of a B9-P52 complex untested
  9. 2026 High

    Defined the architecture of the P36-P52 heterodimer and mapped a functionally vulnerable, antibody-accessible surface, connecting structure to invasion-blocking activity.

    Evidence AlphaFold modeling, EM, SAXS, and epitope-tag neutralization assays in the P. berghei sporozoite-hepatocyte invasion model

    PMID:42418521

    Open questions at the time
    • Model relies partly on prediction rather than a solved crystal/cryo-EM structure
    • Host receptor contact on the P52 face not directly mapped
    • Neutralization shown via inserted epitope tags in rodent parasite

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the P52-P36 complex mechanistically drives parasitophorous vacuole biogenesis downstream of EphA2 engagement, and whether P52's putative GPI anchor and scaffolding are direct requirements for that step, remain unresolved.
  • No direct demonstration of P52-host receptor contact
  • Molecular link between P36 secretion and PV membrane formation unknown
  • GPI anchoring of P52 not experimentally confirmed

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
B9 (6-CYS PROTEIN, BETA-PROPELLER DOMAIN; HETEROLOGOUS INTERACTION ONLY)HOST HEPATOCYTE EPHA2 (PATHWAY EFFECTOR; DIRECT INTERACTION SHOWN FOR P36)P36 (6-CYS PROTEIN, HETERODIMER PARTNER)
Complex memberships
P36-P52 heterodimer (micronemal 6-cysteine complex)

Evidence

Reading pass · 10 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2005 P52 (referred to as P36p in P. berghei) is required for normal liver-stage development: p36p-deficient P. berghei sporozoites infect and traverse hepatocytes normally but abort development within the hepatocyte, indicating P52 is dispensable for hepatocyte invasion but essential for intrahepatocytic development. Targeted gene deletion (knockout) in P. berghei with in vivo and in vitro liver-stage development assays Proceedings of the National Academy of Sciences of the United States of America High 16103357
2007 Simultaneous deletion of P52 and P36 in P. yoelii results in sporozoites that fail to form a parasitophorous vacuole (PV) within hepatocytes in vitro and in vivo; parasites instead localize as free entities in the host cell cytoplasm or nucleoplasm and do not develop as liver stages, demonstrating that P52 and P36 together are essential for PV formation during hepatocyte invasion. Simultaneous double-gene deletion by single genetic manipulation; immunofluorescence analysis and electron microscopy of infected hepatocytes in vitro and in vivo Infection and immunity High 17517871
2008 Disruption of P52 in P. falciparum generates sporozoites with normal gliding motility, cell traversal, and hepatocyte invasion rates, but developmental arrest occurs very soon after invasion of primary human hepatocytes, confirming that P52 is required for intrahepatocytic development but not for invasion. Gene disruption by double-crossover recombination in P. falciparum; in vitro liver-stage growth assay with primary human hepatocytes PloS one High 18958160
2008 SAP1 deletion in P. yoelii abolishes expression of P52 (along with UIS3 and UIS4) but not constitutively expressed sporozoite proteins such as CSP and TRAP, placing SAP1 upstream of P52 in a post-transcriptional gene expression control pathway. Targeted gene deletion of SAP1 followed by RT-PCR/expression analysis of downstream genes in P. yoelii Molecular microbiology Medium 18466298
2012 The s48/45 domain of 6-cysteine proteins (the domain shared by P52 and other family members including Pf12) adopts a β-sandwich fold formed by two sheets with mixed parallel and antiparallel strands, with three disulfide bonds among six conserved cysteines; this domain is structurally related to the SAG1-related-sequence (SRS) fold of Toxoplasma surface antigens and to ephrins. NMR structure determination of the C-terminal s48/45 domain of Pf12 (a representative 6-cys domain, the structure being attributed to the shared domain class that includes P52) Proceedings of the National Academy of Sciences of the United States of America Medium 22493233
2015 Lack of host hepatocyte EphA2 receptor phenocopies lack of P52 and P36 in sporozoites (failure to form a permissive PV), suggesting that the P36-P52 pathway converges on EphA2 for establishment of the replication-permissive compartment. Genetic deletion of EphA2 in mice combined with comparison to p52/p36-deficient sporozoite phenotype; sporozoite infection assays Science (New York, N.Y.) Medium 26612952
2018 P52 partially co-localizes with P36 in sporozoite secretory microneme organelles, and P36 and P52 form a protein complex in sporozoites as determined by co-immunoprecipitation; upon sporozoite stimulation, only P36 is released as a secreted protein while P52 is not, supporting a model in which putatively GPI-anchored P52 serves as a scaffold to facilitate the interaction of secreted P36 with the host cell during sporozoite invasion of hepatocytes. Immunofluorescence co-localization with P36mCherry-tagged P. yoelii parasites; co-immunoprecipitation from sporozoite lysates; secretion assay upon sporozoite stimulation Frontiers in cellular and infection microbiology High 30547015
2018 Single deletion of P52 alone (without P36) in P. yoelii results in sporozoites that also lack a PV after hepatocyte invasion, phenocopying the dual p52/p36 deletion, demonstrating that P52 individually is equally essential for PV establishment and that both proteins act in the same pathway. Single-gene deletion of P52 in P. yoelii with IFA-based assessment of PV formation in infected hepatocytes Frontiers in cellular and infection microbiology High 30547015
2023 The beta-propeller domain of B9 (another 6-cys protein) interacts with both P36 and P52 in a heterologous expression system, suggesting P52 participates in a multi-protein invasion complex. Heterologous expression system interaction assay (co-expression/pulldown) iScience Low 36761022
2026 AlphaFold-based structural modeling combined with electron microscopy and SAXS data indicate that P36 and P52 form a heterodimer with a head-to-tail architecture; the interaction interface is largely conserved among Plasmodium species. Antibodies targeting epitope tags inserted at membrane-distal sites on P52 can block sporozoite invasion of hepatocytes in culture, while antibodies targeting membrane-proximal sites lack inhibitory activity, identifying the membrane-distal face of the P36-P52 heterodimer as an antibody-accessible vulnerable site. AlphaFold structural modeling; electron microscopy; small-angle X-ray scattering (SAXS); epitope-tag insertion at defined structural positions; neutralization assays in P. berghei sporozoite-hepatocyte invasion model PLoS pathogens High 42418521

Source papers

Stage 0 corpus · 25 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2005 Genetically attenuated, P36p-deficient malarial sporozoites induce protective immunity and apoptosis of infected liver cells. Proceedings of the National Academy of Sciences of the United States of America 227 16103357
2009 Preerythrocytic, live-attenuated Plasmodium falciparum vaccine candidates by design. Proceedings of the National Academy of Sciences of the United States of America 144 19625622
2007 Plasmodium yoelii sporozoites with simultaneous deletion of P52 and P36 are completely attenuated and confer sterile immunity against infection. Infection and immunity 129 17517871
2013 First-in-human evaluation of genetically attenuated Plasmodium falciparum sporozoites administered by bite of Anopheles mosquitoes to adult volunteers. Vaccine 103 24029408
2008 Targeted deletion of SAP1 abolishes the expression of infectivity factors necessary for successful malaria parasite liver infection. Molecular microbiology 94 18466298
2015 Malaria parasites target the hepatocyte receptor EphA2 for successful host infection. Science (New York, N.Y.) 84 26612952
2017 Complete attenuation of genetically engineered Plasmodium falciparum sporozoites in human subjects. Science translational medicine 83 28053159
2008 Gene disruption of Plasmodium falciparum p52 results in attenuation of malaria liver stage development in cultured primary human hepatocytes. PloS one 82 18958160
2014 A next-generation genetically attenuated Plasmodium falciparum parasite created by triple gene deletion. Molecular therapy : the journal of the American Society of Gene Therapy 73 24827907
2007 Genetically attenuated P36p-deficient Plasmodium berghei sporozoites confer long-lasting and partial cross-species protection. International journal for parasitology 62 17604034
2012 Structure of the Plasmodium 6-cysteine s48/45 domain. Proceedings of the National Academy of Sciences of the United States of America 61 22493233
2012 Assessing the adequacy of attenuation of genetically modified malaria parasite vaccine candidates. Vaccine 57 22342550
2016 The s48/45 six-cysteine proteins: mediators of interaction throughout the Plasmodium life cycle. International journal for parasitology 51 27899328
2011 Comparative efficacy of pre-erythrocytic whole organism vaccine strategies against the malaria parasite. Vaccine 46 21787828
2022 A genetically engineered Plasmodium falciparum parasite vaccine provides protection from controlled human malaria infection. Science translational medicine 39 36001680
2010 Removal of heterologous sequences from Plasmodium falciparum mutants using FLPe-recombinase. PloS one 33 21152048
2018 The Micronemal Plasmodium Proteins P36 and P52 Act in Concert to Establish the Replication-Permissive Compartment Within Infected Hepatocytes. Frontiers in cellular and infection microbiology 28 30547015
2012 Plasmodium berghei Δp52&p36 parasites develop independent of a parasitophorous vacuole membrane in Huh-7 liver cells. PloS one 20 23227206
2011 Immunization with genetically attenuated P52-deficient Plasmodium berghei sporozoites induces a long-lasting effector memory CD8+ T cell response in the liver. Journal of immune based therapies and vaccines 14 22004696
2022 An In Silico Analysis of Malaria Pre-Erythrocytic-Stage Antigens Interpreting Worldwide Genetic Data to Suggest Vaccine Candidate Variants and Epitopes. Microorganisms 10 35744609
2018 Identifying Potential Plasmodium vivax Sporozoite Stage Vaccine Candidates: An Analysis of Genetic Diversity and Natural Selection. Frontiers in genetics 9 29422913
2023 Plasmodium sporozoites require the protein B9 to invade hepatocytes. iScience 5 36761022
2024 Identifying Plasmodium P36 and P52 antigens for coadministration with circumsporozoite protein to enhance vaccine efficacy. NPJ vaccines 1 39643623
2026 A structure-based epitope tagging approach identifies vulnerable sites on the malarial P36-P52 protein complex for antibody-mediated neutralization of Plasmodium sporozoites. PLoS pathogens 0 42418521
2024 Identifying Plasmodium P36 and P52 antigens for co-administration with circumsporozoite protein to enhance vaccine efficacy. Research square 0 39399676