Affinage · Plasmodium

PF3D7_0708500

heat shock protein 86 family protein

Audit flag: identity unverified
Annotated
2026-09-08
52 papers in source corpus 17 papers cited in narrative 17 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PF3D7_0708500 encodes PfHsp90, the major cytosolic Hsp90 chaperone of Plasmodium falciparum and a hub of intraerythrocytic proteostasis (PMID:12584193, PMID:15339915). It assembles into ~300 kDa (~11S) hetero-oligomeric complexes containing PfHsp70, and geldanamycin disruption of these complexes arrests the parasite at the ring-to-trophozoite transition and blocks heat-shock-driven developmental progression, establishing PfHsp90 as essential for temperature-dependent development (PMID:12584193, PMID:15339915). The chaperone possesses ATP-binding and exceptionally high ATPase activity — the highest among characterized Hsp90s and roughly six-fold above human Hsp90 — that is potently inhibited by geldanamycin, and it displays nucleotide-dependent holdase activity that suppresses substrate aggregation (PMID:14514358, PMID:20837488, PMID:40907219). Its unusually long charged linker is itself a functional determinant of ATPase rate, co-chaperone interaction, and conformation (PMID:22315411), and an acetylation site overlapping the Aha1/p23 co-chaperone binding region modulates complex assembly (PMID:20837488). PfHsp90 nucleates a co-chaperone network, associating with the phosphatase PfPP5, calcineurin, PfFKBP35 via its TPR domain, and PfHop through a direct, nucleotide-independent contact between the PfHop TPR2A subdomain and the PfHsp90 C-terminus (PMID:15339915, PMID:11737864, PMID:15850699, PMID:15811524, PMID:26267894). Functionally, PfHsp90 chaperones PfSir2A to preserve its histone deacetylase activity and thereby maintain var gene and ribosomal silencing (PMID:36121150), and it directly promotes assembly and hydrolytic activity of the 26S proteasome (PMID:38492573). Structural features including Arg98 in the ATP-binding pocket confer selectivity for parasite-directed inhibitors, making PfHsp90 an antimalarial drug target (PMID:22615284, PMID:26711771).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 1994 Medium

    Establishing the gene structure and expression behavior of pfhsp86 addressed whether the parasite's cytosolic Hsp90 is a stress-inducible single-copy chaperone.

    Evidence cDNA/gene sequencing, Northern blot heat-shock induction, and chromosomal mapping in P. falciparum

    PMID:7828879

    Open questions at the time
    • Did not test chaperone or enzymatic function
    • Functional significance of the calreticulin-homologous charged region unaddressed
  2. 2003 High

    Identifying that PfHsp90 forms large PfHsp70-containing complexes whose geldanamycin inhibition arrests growth at the ring-to-trophozoite transition connected the chaperone to a specific, druggable developmental checkpoint.

    Evidence Sedimentation, SEC, co-IP, phosphorylation labeling, and parasite growth inhibition; plus recombinant ATP-binding assay in strains 3D7 and W2

    PMID:12584193 PMID:14514358

    Open questions at the time
    • Kinase responsible for GA-sensitive phosphorylation not identified
    • Direct substrates of the chaperone complex not defined
  3. 2004 High

    Showing that GA-mediated disruption of the PfHsp90/PfHsp70/PfPP5/tubulin complex attenuates heat-driven ring-to-trophozoite progression established the chaperone as required for temperature-dependent development.

    Evidence Co-IP of complex components with flow-cytometric stage quantification across temperatures

    PMID:15339915

    Open questions at the time
    • Individual contribution of each complex partner not dissected
    • Mechanism linking chaperone to the thermal checkpoint unresolved
  4. 2005 Medium

    Mapping physical partners (PfPP5, PfFKBP35 via its TPR domain, calcineurin) defined PfHsp90 as the organizing center of a phosphatase/immunophilin co-chaperone network and revealed drug synergy.

    Evidence Co-IP from parasite lysate, GA-disruption, phosphatase assays, and geldanamycin/ascomycin synergy in culture

    PMID:11737864 PMID:15811524 PMID:15850699

    Open questions at the time
    • Single co-IP experiments without reciprocal validation for most partners
    • Functional consequence of each association for client processing not established
  5. 2010 High

    Quantifying PfHsp90's exceptionally high ATPase activity and identifying an acetylation site overlapping the Aha1/p23 domain linked its enzymatic power and a PTM to complex assembly and drug sensitivity.

    Evidence Full-length recombinant ATPase assays, mass spectrometry PTM mapping, and HDAC-inhibitor-induced complex dissociation

    PMID:20837488

    Open questions at the time
    • Enzyme responsible for the acetylation not identified
    • Structural basis for the higher-than-human ATPase rate not resolved
  6. 2012 High

    Demonstrating that the parasite charged linker is a functional determinant and that Arg98 governs inhibitor selectivity provided structural rationale for parasite-selective Hsp90 targeting.

    Evidence Chimeric yeast Hsp90 linker swaps with ATPase/biophysical/complementation assays, and site-directed mutagenesis with SPR

    PMID:22315411 PMID:22615284

    Open questions at the time
    • Linker mechanism tested in yeast context rather than native parasite
    • Selectivity residue validated for a single compound (harmine)
  7. 2015 High

    Resolving the direct, subdomain-specific PfHop TPR2A–PfHsp90 C-terminal interaction and identifying PfHsp90 as the class 2 imidazopyridazine target refined both the co-chaperone architecture and druggability.

    Evidence Far-Western, SPR, co-IP, split-GFP for the Hop interaction; compound pulldown and PKG gatekeeper-mutant controls for target ID

    PMID:26267894 PMID:26711771

    Open questions at the time
    • Functional consequence of Hop-mediated bridging for specific clients not shown
    • Whether class 2 binding phenocopies ATPase inhibition not fully established
  8. 2022 High

    Establishing that PfHsp90 chaperones PfSir2A to sustain its deacetylase activity connected the chaperone to epigenetic var gene and ribosomal silencing.

    Evidence Reciprocal co-IP, chemical inhibition (17-AAG, Radicicol), protein-stability Westerns, HDAC activity assays, and var gene expression analysis

    PMID:36121150

    Open questions at the time
    • Direct chaperone-client folding mechanism for PfSir2A not reconstituted
    • Breadth of PfHsp90-dependent epigenetic clients unknown
  9. 2024 High

    Showing that PfHsp90 directly promotes 26S proteasome assembly and activity, alongside confirmation of nucleotide-dependent holdase activity, placed the chaperone at the center of parasite proteostasis and degradation.

    Evidence Thermal proteome profiling with a selective inhibitor, co-fractionation and proteasome activity assays, plus in vitro ATPase/aggregation-suppression and C-terminal nucleotide-binding mutagenesis

    PMID:38492573 PMID:40907219

    Open questions at the time
    • Mechanism of proteasome subunit chaperoning not structurally defined
    • C-terminal nucleotide-binding determinants not yet validated in parasites

Open questions

Synthesis pass · forward-looking unresolved questions
  • How PfHsp90's co-chaperone network, PTMs, and client repertoire are integrated to control the developmental thermal checkpoint and epigenetic/proteostatic outputs remains unresolved.
  • No comprehensive parasite client interactome defined
  • Regulatory logic coupling ATPase cycle to specific client fates unknown
  • In vivo role of the charged linker in native parasites untested

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
CALCINEURIN (PP2B)PFFKBP35PFHOP (TPR2A SUBDOMAIN)PFHSP70PFPP5PFSIR2ATUBULIN
Complex memberships
26S proteasome (assembly chaperone)PfHsp90-PfHop-PfHsp70 complexPfHsp90-PfHsp70-PfPP5-tubulin complexPfHsp90-calcineurin (PP2B) complex~300 kDa PfHsp90-PfHsp70 multi-chaperone complex

Evidence

Reading pass · 17 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2003 PfHsp90 forms ~300 kDa complexes (sedimentation coefficient ~11S) that contain PfHsp70; geldanamycin (GA) inhibits these complexes and arrests parasite growth at the ring-to-trophozoite transition, and GA selectively inhibits PfHsp90 phosphorylation in treated cultures. Sedimentation analysis, size exclusion chromatography, co-immunoprecipitation, homology modeling, parasite culture inhibition assay, metabolic labeling The Journal of biological chemistry High 12584193
1994 The PfHsp90 (pfhsp86) gene is encoded by two exons separated by an 0.8-kb intron; it is expressed constitutively in both trophozoite and gametocyte stages, is a single-copy gene, and its transcript is upregulated 2–4-fold at elevated temperatures (39–41°C). The encoded protein contains an unusually large charged region with homology to the calreticulin calcium-binding domain. cDNA/gene sequencing, Northern blot (heat-shock transcription induction), chromosomal mapping, sequence analysis Gene Medium 7828879
2003 Recombinant PfHsp90 exhibits ATP-binding activity that is specifically inhibited by geldanamycin in vitro; the protein is expressed at all erythrocytic stages, with relatively lower amounts in schizonts. Recombinant protein expression, ATP-binding assay, immunoblot of stage-specific lysates Malaria journal Medium 14514358
2004 The PfHsp90 multi-chaperone complex (containing PfHsp70, PfPP5, and tubulin) is disrupted by geldanamycin, and this disruption attenuates heat shock-mediated promotion of parasite ring-to-trophozoite progression, establishing PfHsp90 as essential for temperature-dependent parasite development. Co-immunoprecipitation, flow cytometry (parasite stage quantification), geldanamycin inhibition assay The Journal of biological chemistry High 15339915
2005 PfHsp90 physically associates with PfPP5 (a serine/threonine phosphatase) in vivo, as demonstrated by co-immunoprecipitation. Co-immunoprecipitation from parasite lysate BMC microbiology Medium 11737864
2005 PfHsp90 associates with PfFKBP35 via the TPR domain of FKBP35; geldanamycin (Hsp90 inhibitor) and ascomycin (FKBP35 inhibitor) inhibit P. falciparum growth synergistically. Co-immunoprecipitation, synergy inhibition assay in parasite culture Molecular and biochemical parasitology Medium 15850699
2005 Parasitic calcineurin (PP2B) associates with PfHsp90 in vivo; geldanamycin disrupts this association without affecting cyclosporin A sensitivity, establishing PfHsp90 as a component of the calcineurin complex. Co-immunoprecipitation, GA treatment disruption assay, in vitro phosphatase activity assay Molecular and biochemical parasitology Medium 15811524
2010 Full-length recombinant PfHsp90 has the highest ATPase activity of all known Hsp90s (6-fold higher than human Hsp90), and GA inhibits PfHsp90 ATPase more robustly than human Hsp90. Mass spectrometry identified an acetylation site overlapping the Aha1/p23 binding domain; histone deacetylase inhibitor treatment caused partial dissociation of the PfHsp90 complex. In vitro ATPase assay (recombinant full-length protein), mass spectrometry (acetylation site), histone deacetylase inhibitor treatment + co-immunoprecipitation The Journal of biological chemistry High 20837488
2011 PfHop (Hsp70-Hsp90 organising protein) co-localises with PfHsp90 and PfHsp70 in the trophozoite-stage cytosol, and is present in a complex with both chaperones as shown by gel filtration and co-immunoprecipitation. Immunofluorescence co-localisation, gel filtration chromatography, co-immunoprecipitation Cell stress & chaperones Medium 22005844
2012 When the plasmodium native charged linker of PfHsp90 was introduced into yeast Hsp90 in place of the yeast linker, it affected ATPase activity, cochaperone interaction, and conformation in vitro and chaperone function in vivo, demonstrating that the linker sequence (not just length) is a functional determinant of Hsp90 activity. Chimeric yeast Hsp90 constructs with plasmodium linkers, in vitro ATPase assay, biophysical characterisation, in vivo yeast complementation assay Proceedings of the National Academy of Sciences of the United States of America High 22315411
2012 Site-directed mutagenesis of Arg98 in the PfHsp90 ATP-binding domain abolishes selective binding of harmine to PfHsp90 over human Hsp90, identifying Arg98 as a key residue for inhibitor selectivity. Site-directed mutagenesis, surface plasmon resonance (binding affinity measurement) Antimicrobial agents and chemotherapy Medium 22615284
2015 Class 2 imidazopyridazine compounds bind to the ATP-binding site of the N-terminal domain of PfHsp90, and PfHsp90 was identified as a binding partner of these class 2 compounds responsible for trophozoite-stage growth inhibition. Target identification (binding partner pulldown/MS), gatekeeper-mutant PKG parasite lines to rule out PKG as class 2 target, compound-Hsp90 binding characterisation Antimicrobial agents and chemotherapy Medium 26711771
2015 PfHop TPR2A subdomain preferentially interacts with the C-terminus of PfHsp90 (over PfHsp70-1), while TPR1 and TPR2B bind preferentially to PfHsp70-1; the PfHop–PfHsp90 interaction is direct and nucleotide-independent, as shown by far-Western, SPR, and split-GFP approaches. Far-Western blot, surface plasmon resonance, co-immunoprecipitation, split-GFP subdomain interaction assay PloS one High 26267894
2022 PfHsp90 physically interacts with PfSir2A (a histone deacetylase), and inhibition of PfHsp90 with 17-AAG or Radicicol leads to depletion of PfSir2A protein and loss of its histone deacetylase activity, resulting in derepression of var genes and loss of ribosomal silencing. Co-immunoprecipitation, chemical inhibition (17-AAG, Radicicol), Western blot (protein stability), HDAC activity assay, gene expression analysis (var gene derepression) mSphere High 36121150
2024 PfHsp90 directly promotes assembly and hydrolytic activity of the 26S proteasome; thermal proteome profiling upon PfHsp90 inhibition enriched proteasome subunits among destabilised proteins, and biochemical/cellular studies confirmed PfHsp90 chaperoning of the active 26S complex. Thermal proteome profiling, biochemical co-fractionation, cellular proteasome activity assays, selective PfHsp90 inhibitor (Tropane 1) Cell chemical biology High 38492573
2024 PfHsp90 exhibits in vitro ATPase activity and suppresses heat-induced aggregation of model substrates in a nucleotide-dependent manner (holdase chaperone activity); both activities are inhibited by NECA. Additionally, a C-terminal truncation of PfHsp90 specifically interacts with ATP (but not AMP or GTP) via an interaction requiring structural determinants identified by mutagenesis. ATPase assay, chaperone aggregation-suppression assay, affinity binding with lysine-reactive nucleotide analog and ATP resin, limited proteolysis, mutagenesis, molecular docking Bioorganic & medicinal chemistry Medium 40907219
2024 PfGrp94 (the ER-localised Hsp90 paralogue) is a distinct isoform from the cytosolic PfHsp90; it is localized in the endoplasmic reticulum. Plasmodium falciparum encodes four Hsp90 isoforms (cytosol, ER, mitochondria, apicoplast). Recombinant protein characterisation, ATPase assay, chaperone suppression assay, antiplasmodial assay Proteins Low 39670568

Source papers

Stage 0 corpus · 52 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2003 Heat shock protein 90 function is essential for Plasmodium falciparum growth in human erythrocytes. The Journal of biological chemistry 190 12584193
2010 Heat shock protein 90 as a drug target against protozoan infections: biochemical characterization of HSP90 from Plasmodium falciparum and Trypanosoma evansi and evaluation of its inhibitor as a candidate drug. The Journal of biological chemistry 139 20837488
2012 Charged linker sequence modulates eukaryotic heat shock protein 90 (Hsp90) chaperone activity. Proceedings of the National Academy of Sciences of the United States of America 107 22315411
2011 Intracellular protozoan parasites of humans: the role of molecular chaperones in development and pathogenesis. Protein and peptide letters 90 20955165
2009 Plasmodial heat shock proteins: targets for chemotherapy. FEMS immunology and medical microbiology 88 20041948
2003 The heat shock protein 90 of Plasmodium falciparum and antimalarial activity of its inhibitor, geldanamycin. Malaria journal 82 14514358
2004 Recurrent fever promotes Plasmodium falciparum development in human erythrocytes. The Journal of biological chemistry 71 15339915
2010 A repurposing strategy identifies novel synergistic inhibitors of Plasmodium falciparum heat shock protein 90. Journal of medicinal chemistry 64 20349996
2011 Characterisation of the Plasmodium falciparum Hsp70-Hsp90 organising protein (PfHop). Cell stress & chaperones 59 22005844
2005 The FK506-binding protein of the malaria parasite, Plasmodium falciparum, is a FK506-sensitive chaperone with FK506-independent calcineurin-inhibitory activity. Molecular and biochemical parasitology 56 15850699
1994 Molecular characterization of the heat shock protein 90 gene of the human malaria parasite Plasmodium falciparum. Molecular and biochemical parasitology 56 7838176
2012 Harmine is a potent antimalarial targeting Hsp90 and synergizes with chloroquine and artemisinin. Antimicrobial agents and chemotherapy 52 22615284
2005 Plasmodium falciparum calcineurin and its association with heat shock protein 90: mechanisms for the antimalarial activity of cyclosporin A and synergism with geldanamycin. Molecular and biochemical parasitology 52 15811524
2015 Imidazopyridazine Inhibitors of Plasmodium falciparum Calcium-Dependent Protein Kinase 1 Also Target Cyclic GMP-Dependent Protein Kinase and Heat Shock Protein 90 To Kill the Parasite at Different Stages of Intracellular Development. Antimicrobial agents and chemotherapy 47 26711771
2015 Plasmodium falciparum Hop (PfHop) Interacts with the Hsp70 Chaperone in a Nucleotide-Dependent Fashion and Exhibits Ligand Selectivity. PloS one 40 26267894
1994 Sequence, transcript characterization and polymorphisms of a Plasmodium falciparum gene belonging to the heat-shock protein (HSP) 90 family. Gene 38 7828879
2001 A novel tetratricopeptide repeat (TPR) containing PP5 serine/threonine protein phosphatase in the malaria parasite, Plasmodium falciparum. BMC microbiology 35 11737864
2018 Identification of Hsp90 Inhibitors with Anti-Plasmodium Activity. Antimicrobial agents and chemotherapy 34 29339390
2016 In vitro and in vivo anti-malarial activity of novel harmine-analog heat shock protein 90 inhibitors: a possible partner for artemisinin. Malaria journal 34 27903279
2007 Three-dimensional structure of heat shock protein 90 from Plasmodium falciparum: molecular modelling approach to rational drug design against malaria. Journal of biosciences 32 17536172
2013 Targeting Plasmodium falciparum Hsp90: Towards Reversing Antimalarial Resistance. Pathogens (Basel, Switzerland) 30 25436880
2022 Design and synthesis of harmiquins, harmine and chloroquine hybrids as potent antiplasmodial agents. European journal of medicinal chemistry 28 35551033
1988 Identification of a heat shock-like antigen in P. falciparum, related to the heat shock protein 90 family. Nucleic acids research 27 3060854
1994 Immunogenicity and antigenicity of a Plasmodium falciparum protein fraction (90-110 kDa) able to protect squirrel monkeys against asexual blood stages. Vaccine 26 8303938
2013 Heat shock protein 90 inhibitors as broad spectrum anti-infectives. Current pharmaceutical design 23 22920905
2021 Inhibitors of the Plasmodium falciparum Hsp90 towards Selective Antimalarial Drug Design: The Past, Present and Future. Cells 20 34831072
2022 Hsp90 and Associated Co-Chaperones of the Malaria Parasite. Biomolecules 18 35892329
2021 Further investigation of harmicines as novel antiplasmodial agents: Synthesis, structure-activity relationship and insight into the mechanism of action. European journal of medicinal chemistry 17 34274829
2014 Co-chaperones of Hsp90 in Plasmodium falciparum and their concerted roles in cellular regulation. Parasitology 17 24560171
2011 Target highlights in CASP9: Experimental target structures for the critical assessment of techniques for protein structure prediction. Proteins 17 22020785
2019 Plasmodium falciparum R2TP complex: driver of parasite Hsp90 function. Biophysical reviews 16 31734827
2024 Selective targeting of Plasmodium falciparum Hsp90 disrupts the 26S proteasome. Cell chemical biology 15 38492573
2023 Pharmacophore Model-Based Virtual Screening Workflow for Discovery of Inhibitors Targeting Hsp90. ACS omega 15 37867657
2021 Plasmodium berghei Hsp90 contains a natural immunogenic I-Ab-restricted antigen common to rodent and human Plasmodium species. Current research in immunology 15 35492393
2018 Novobiocin-ferrocene conjugates possessing anticancer and antiplasmodial activity independent of HSP90 inhibition. Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry 15 30542925
2018 In silico identification and evaluation of potential interaction of Azadirachta indica phytochemicals with Plasmodium falciparum heat shock protein 90. Journal of molecular graphics & modelling 15 30544005
2023 The Plasmodium falciparum exported J domain proteins fine-tune human and malarial Hsp70s: pathological exploitation of proteostasis machinery. Frontiers in molecular biosciences 11 37457831
2013 Targeting heat shock protein 90 for malaria. Mini reviews in medicinal chemistry 11 24070209
2021 Molecular docking and molecular dynamics simulation identify a novel Radicicol derivative that predicts exclusive binding to Plasmodium falciparum Topoisomerase VIB. Journal of biomolecular structure & dynamics 10 33650468
2024 Characterization and Inhibition of the Chaperone Function of Plasmodium falciparum Glucose-Regulated Protein 94 kDa (Pf Grp94). Proteins 8 39670568
1999 Stage-specific expression of heat shock protein 90 in murine malaria parasite Plasmodium yoelii. Experimental parasitology 7 10502467
2022 Heat Shock Protein 90 Regulates the Activity of Histone Deacetylase Sir2 in Plasmodium falciparum. mSphere 6 36121150
2021 Role of Hsp90 in Plasmodium falciparum Malaria. Advances in experimental medicine and biology 6 34569023
2024 Ursolic acid acetate and iso-mukaadial acetate bind to Plasmodium falciparum Hsp90, abrogating its chaperone function in vitro. Naunyn-Schmiedeberg's archives of pharmacology 5 38252299
2024 Auto QSAR-based active learning docking for hit identification of potential inhibitors of Plasmodium falciparum Hsp90 as antimalarial agents. PloS one 4 39585817
2023 In silico prediction and in vitro assessment of novel heterocyclics with antimalarial activity. Parasitology research 4 38155300
2018 Structure-activity relationship of new antimalarial 1-aryl-3-susbtituted propanol derivatives: Synthesis, preliminary toxicity profiling, parasite life cycle stage studies, target exploration, and targeted delivery. European journal of medicinal chemistry 4 29754074
2025 The possibilities and challenges associated with selective targeting Plasmodium falciparum Hsp90 for Malaria. Transactions of the Royal Society of South Africa. Royal Society of South Africa 1 41836916
2026 Synthetic quinolone-tethered aminoguanidine derivatives exhibit potent anti-plasmodial activity. International journal of antimicrobial agents 0 41921671
2026 Data sets on the interaction of FKBP35 from Plasmodium knowlesi and Hsp90 C-terminal pentapeptide. Data in brief 0 42376286
2026 In Silico Exploration of Antimalarial Potential of Ethanolic Leaf Extract of Heliotropium indicum. Nigerian journal of physiological sciences : official publication of the Physiological Society of Nigeria 0 42537022
2025 Investigation of a cryptic ligand binding site on Plasmodium falciparum Hsp90. Bioorganic & medicinal chemistry 0 40907219