Affinage · Plasmodium

PF3D7_1303800

peptidase, putative

Audit flag: identity unverified
Annotated
2026-09-08
23 papers in source corpus 8 papers cited in narrative 8 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PF3D7_1303800 (PfSPP) is a presenilin-type intramembrane aspartyl protease of P. falciparum that is required for intra-erythrocytic parasite development (PMID:22844982). It is an ER-resident enzyme, localized to the endoplasmic reticulum by immunofluorescence and immunogold electron microscopy, and it exists in both monomer and dimer forms in parasite lysate (PMID:22844982, PMID:25017910). An early report placing PfSPP at the micronemes and implicating it in erythrocyte invasion via binding to erythrocyte band 3 (PMID:18160114) was directly superseded by a rigorous multi-method study showing PfSPP remains intracellular throughout invasion, plays no role in invasion, and is instead required for intra-erythrocytic growth (PMID:22844982). Heat shock protein 101 (HSP101) has been identified as a substrate of PfSPP using an in vivo luminescence cleavage assay, and partial inhibition of the enzyme correlates with gametocyte emergence (PMID:25017910). PfSPP activity is inhibited by HIV protease inhibitors, with Atazanavir selectively inhibiting the parasite enzyme over the host enzyme (PMID:31311649). Beyond substrate identification and the ER localization/oligomeric state, the catalytic mechanism, regulation, and full substrate repertoire of PfSPP have not been characterized in the available corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 5 steps
  1. 2007 Medium

    The first attempt to assign a cellular role proposed PfSPP as a micronemal invasion ligand, framing it as a merozoite surface-associated factor engaging the erythrocyte during entry.

    Evidence Yeast two-hybrid, immunolocalization, invasion-inhibition antibody, and direct binding assay to erythrocyte band 3 5ABC domain in P. falciparum

    PMID:18160114

    Open questions at the time
    • Later directly contradicted by a more rigorous study
    • No genetic ablation to test the invasion requirement
    • Binding to band 3 not reconciled with subsequent intracellular localization
  2. 2009 Low

    Pharmacology raised the question of whether SPP is needed across life-cycle stages, indicating a role in liver-stage development independent of host Notch signaling.

    Evidence gamma-secretase/SPP inhibitor LY411,575 in hepatoma lines, mouse hepatocytes, and P. berghei in vivo, with Notch exclusion experiment

    PMID:19337374

    Open questions at the time
    • Inhibitor selectivity limited; effect not tied directly to the PfSPP protein
    • Ortholog inference rather than direct PF3D7_1303800 assay
    • No demonstration of on-target engagement in parasite
  3. 2012 High

    A rigorous re-examination resolved the localization and function controversy, establishing PfSPP as an ER-resident protease required for intra-erythrocytic growth rather than an invasion ligand.

    Evidence Immunofluorescence, subcellular fractionation, SPP-specific chemical inhibitors, and invasion assays in P. falciparum

    PMID:22844982

    Open questions at the time
    • Substrate(s) driving the growth requirement not identified in this study
    • Precise ER sub-compartment and topology not defined
    • No genetic knockout to confirm essentiality
  4. 2014 Medium

    Substrate identification and oligomeric characterization gave PfSPP a molecular activity, naming HSP101 as a cleavage substrate and linking partial inhibition to gametocyte emergence.

    Evidence Immunofluorescence, immunogold EM, Western blot for monomer/dimer, and transfection-based in vivo luminescence substrate assay in P. falciparum

    PMID:25017910

    Open questions at the time
    • HSP101 cleavage site and physiological consequence not mapped
    • Gametocytogenesis link is correlative
    • Single lab, no independent confirmation of the substrate
  5. 2019 Medium

    Direct enzymatic assays established that PfSPP activity can be selectively targeted, distinguishing parasite from host SPP inhibition.

    Evidence Transcription-based SPP activity assay with Lopinavir/Atazanavir, plus Babesia microti growth inhibition ex vivo and in vivo

    PMID:31311649

    Open questions at the time
    • Structural basis of parasite-selective inhibition not defined
    • In-parasite target validation limited to activity readout
    • Whether inhibition of growth is solely via PfSPP not proven

Open questions

Synthesis pass · forward-looking unresolved questions
  • The catalytic mechanism, complete substrate repertoire, and the mechanistic basis linking PfSPP activity to intra-erythrocytic development and gametocytogenesis remain unresolved.
  • No structural model or active-site characterization for PfSPP
  • No genetic knockout defining essentiality
  • Mechanism connecting HSP101 cleavage to the growth requirement unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
HSP101 (SUBSTRATE) [#3]

Evidence

Reading pass · 8 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 PfSPP (PF3D7_1303800) was identified as a presenilin-type intramembrane aspartyl protease localized to micronemes in merozoites (co-localized with EBA-175 in schizonts by immunofluorescence; confirmed by immunoelectron microscopy). An antibody to PfSPP blocked P. falciparum RBC invasion in vitro. Native and recombinant PfSPP bound directly to the 5ABC domain of erythrocyte band 3 protein in solution, and this binding was chymotrypsin-sensitive but trypsin- and neuraminidase-resistant. Yeast two-hybrid screening, immunofluorescence microscopy, immunoelectron microscopy, in vitro invasion inhibition assay with anti-PfSPP antibody, direct binding assay (native and recombinant protein vs. band 3 5ABC domain) Molecular and biochemical parasitology Medium 18160114
2009 The gamma-secretase/SPP inhibitor LY411,575 prevented Plasmodium liver-stage development in human hepatoma cell lines and mouse primary hepatocytes (IC50 ~80 nM) and reduced parasite liver load in vivo, without affecting hepatocyte invasion. The effect was proposed to operate via inhibition of parasite SPP (PF3D7_1303800 ortholog) and was not mediated through the host Notch signaling pathway. Pharmacological inhibition in cell culture and rodent malaria model (P. berghei), Notch pathway exclusion experiment PloS one Low 19337374
2012 PfSPP (PF3D7_1303800) is a bona fide ER-resident intramembrane aspartyl protease that remains intracellular throughout the invasion process. Using molecular, cellular, and chemical approaches, it was shown that PfSPP does NOT localize to micronemes and plays NO role in erythrocyte invasion. SPP-specific drug inhibition had no effect on invasion but had low-micromolar potency against intra-erythrocytic parasite development, establishing PfSPP as required for intra-erythrocytic growth rather than invasion. Immunofluorescence microscopy, subcellular fractionation, SPP-specific chemical inhibitors, invasion assays Traffic (Copenhagen, Denmark) High 22844982
2014 PfSPP (PF3D7_1303800) localizes to the endoplasmic reticulum (confirmed by immunofluorescence and immunogold electron microscopy) and exists in monomer and dimer forms in parasite lysate. Using a transfection-based in vivo luminescence assay, heat shock protein 101 (HSP101) was identified as a substrate of PfSPP. Partial inhibition of PfSPP correlated with gametocyte emergence, implicating PfSPP in gametocytogenesis. Immunofluorescence microscopy, immunogold electron microscopy, Western blot (dimer/monomer), transfection-based in vivo luminescence substrate assay, bioinformatics substrate screen Biochemical and biophysical research communications Medium 25017910
2014 A GFP-tagged PfSPP (PF3D7_1303800) fusion was expressed in P. falciparum (3D7 strain) by transfection. Immunofluorescence microscopy showed GFP fluorescence mainly in the cytoplasm, and Western blot confirmed expression of the PfSPP-GFP fusion protein at ~64 kDa. Transfection, immunofluorescence microscopy, Western blot Zhongguo ji sheng chong xue yu ji sheng chong bing za zhi Low 25518586
2015 Plasmodium SPP (PF3D7_1303800 ortholog) activity can be differentially inhibited by established gamma-secretase inhibitors. Using a recombinant FBA substrate cleavage assay (ELISA, Western blot, IP/MS), LY-411,575 and other GSIs showed differential inhibition of SPP family members, demonstrating the feasibility of selective SPP inhibition. Recombinant substrate cleavage assay (ELISA, Western blot, IP/MALDI-TOF MS), co-transfection expression system PloS one Low 26046535
2017 The gamma-secretase inhibitor YO-01027 (dibenzoazepine-type) inhibits SPP in vitro and in vivo through interaction with Val223 in SPP, and treatment efficiently inhibited propagation of P. falciparum, consistent with PfSPP (PF3D7_1303800) being the relevant target. In vitro SPP inhibition assay, in vivo P. falciparum growth inhibition, site-directed interaction analysis (Val223) Proceedings of the National Academy of Sciences of the United States of America Low 29187532
2019 HIV protease inhibitors Lopinavir and Atazanavir inhibit PfSPP (PF3D7_1303800) activity (measured by transcription-based assay); Lopinavir inhibited both parasite- and host-derived SPP activities while Atazanavir selectively inhibited only parasite-derived SPP activity. These inhibitors also blocked intraerythrocytic growth of Babesia microti ex vivo and in vivo. Transcription-based SPP activity assay, ex vivo Babesia microti growth inhibition, in vivo mouse model (rag1-deficient mice) Biochemical and biophysical research communications Medium 31311649

Source papers

Stage 0 corpus · 23 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1982 Peptidases from Plasmodium falciparum cultured in vitro. Molecular and biochemical parasitology 72 7048089
2005 Active-site specificity of digestive aspartic peptidases from the four species of Plasmodium that infect humans using chromogenic combinatorial peptide libraries. Biochemistry 29 15697202
2007 A Presenilin-like protease associated with Plasmodium falciparum micronemes is involved in erythrocyte invasion. Molecular and biochemical parasitology 26 18160114
2009 A small molecule inhibitor of signal peptide peptidase inhibits Plasmodium development in the liver and decreases malaria severity. PloS one 24 19337374
2012 Malaria parasite signal peptide peptidase is an ER-resident protease required for growth but not for invasion. Traffic (Copenhagen, Denmark) 23 22844982
2010 Downstream effects of haemoglobinase inhibition in Plasmodium falciparum-infected erythrocytes. Molecular and biochemical parasitology 23 20478341
2016 New directions for protease inhibitors directed drug discovery. Biopolymers 21 26584340
2010 Mitochondrial localization of the threonine peptidase PfHslV, a ClpQ ortholog in Plasmodium falciparum. International journal for parasitology 19 20561525
2007 Plasmodium falciparum signal peptidase is regulated by phosphorylation and required for intra-erythrocytic growth. Molecular and biochemical parasitology 19 18054093
2015 Differential Inhibition of Signal Peptide Peptidase Family Members by Established γ-Secretase Inhibitors. PloS one 18 26046535
2013 Ferrous iron-dependent drug delivery enables controlled and selective release of therapeutic agents in vivo. Proceedings of the National Academy of Sciences of the United States of America 15 24145449
2012 Host targeting of virulence determinants and phosphoinositides in blood stage malaria parasites. Trends in parasitology 15 23084821
2016 In silico screening of novel inhibitors of M17 Leucine Amino Peptidase (LAP) of Plasmodium vivax as therapeutic candidate. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie 13 27470355
2019 In silico study of M18 aspartyl amino peptidase (M18AAP) of Plasmodium vivax as an antimalarial drug target. Bioorganic & medicinal chemistry 11 30929948
2017 The Widespread Anti-Protozoal Action of HIV Aspartic Peptidase Inhibitors: Focus on Plasmodium spp., Leishmania spp. and Trypanosoma cruzi. Current topics in medicinal chemistry 11 27784256
2019 Metacaspase-3 of Plasmodium falciparum: An atypical trypsin-like serine protease. International journal of biological macromolecules 10 31301397
2017 Characterization of SPP inhibitors suppressing propagation of HCV and protozoa. Proceedings of the National Academy of Sciences of the United States of America 10 29187532
2014 Specific calpain activity evaluation in Plasmodium parasites. Analytical biochemistry 9 25281458
2005 Isolation and characterization of type I signal peptidase of different malaria parasites. Journal of biomedicine & biotechnology 9 16489263
2014 Plasmodium falciparum signal peptide peptidase cleaves malaria heat shock protein 101 (HSP101). Implications for gametocytogenesis. Biochemical and biophysical research communications 8 25017910
2019 HIV protease inhibitors block parasite signal peptide peptidases and prevent growth of Babesia microti parasites in erythrocytes. Biochemical and biophysical research communications 5 31311649
2022 Evolutionary Analysis of Dipeptidyl Peptidase I. International journal of molecular sciences 0 35163774
2014 [Construction of Plasmodium falciparum signal peptide peptidase-GFP mutant and its expression analysis in the malaria parasite]. Zhongguo ji sheng chong xue yu ji sheng chong bing za zhi = Chinese journal of parasitology & parasitic diseases 0 25518586