{"gene":"PF3D7_0831700","run_date":"2026-09-08T12:51:27","timeline":{"discoveries":[{"year":2012,"finding":"HSP70x (PfHsp70-x) is exported to the host erythrocyte where it forms a complex with exported PfHsp40s (PFA0660w and PFE55) in mobile structures termed J-dots, and is closely associated with PfEMP1; the protein was identified as a parasite-encoded chaperone operating within the host cell.","method":"Co-immunoprecipitation, immunofluorescence microscopy, subcellular fractionation, Western blotting","journal":"Cellular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP and multiple orthogonal imaging/fractionation methods; replicated by subsequent independent studies","pmids":["22925632"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"finding":"PfHsp70-x is expressed maximally at the schizont stage, localizes primarily to the parasitophorous vacuole, and a portion is exported to the erythrocyte compartment where it associates with Maurer's clefts; it carries an endoplasmic reticulum signal peptide and is encoded by a functional (not pseudo) gene.","method":"Subcellular fractionation (saponin and streptolysin-O), immunofluorescence, immunoblotting with peptide-specific antiserum","journal":"Parasite (Paris, France)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization by two fractionation methods and immunofluorescence, single lab","pmids":["23340228"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"Trafficking of PfHsp70-x to the host erythrocyte requires a 7 amino acid motif directly following the hydrophobic N-terminal secretory signal; both reversed and scrambled versions of the motif retained export capacity, but site-directed mutagenesis of glutamate residues within this region blocked trafficking within the parasitophorous vacuole lumen. Unlike PEXEL-containing proteins, the targeting signal is not cleaved but is acetylated. Export also requires the vacuolar translocon PTEX.","method":"Site-directed mutagenesis, GFP reporter constructs, immunofluorescence microscopy, mass spectrometry (acetylation detection)","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — mutagenesis with defined molecular phenotype plus PTM characterization, single lab but multiple orthogonal methods","pmids":["27824087"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"finding":"Knockout of PfHsp70-x (Δhsp70-x) did not affect parasite growth in vitro, but delayed export of PfEMP1 cytoadherence proteins and resulted in reduced adhesion of infected erythrocytes and increased rigidity of infected erythrocytes compared to wild-type controls.","method":"Gene knockout, cytoadherence assays, erythrocyte rigidity measurements, transcriptional and translational profiling","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with multiple defined phenotypic readouts; independently replicated by a second KO study (PMID:28959740)","pmids":["28732045"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"finding":"Complete CRISPR/Cas9 gene knockout of PfHsp70x, as well as knockdown using DHFR-based destabilization domain and glmS ribozyme, did not affect P. falciparum intraerythrocytic growth or export of PfEMP1 to the host RBC.","method":"CRISPR/Cas9 gene knockout, conditional knockdown (DHFR destabilization domain, glmS ribozyme), immunofluorescence, growth assays","journal":"mSphere","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent conditional knockdown systems plus complete KO, multiple assays; negative result for essentiality rigorously established","pmids":["28959740"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"PFA0660w (an exported Hsp40/J-domain protein) specifically stimulates the ATPase activity of PfHsp70-x but not that of PfHsp70-1 or human Hsp70, indicating a selective functional co-chaperone/chaperone partnership; protein binding studies confirmed a direct interaction dependent on the J domain.","method":"ATPase activity assay, protein aggregation suppression assay, co-chaperone binding studies (protein binding in presence/absence of ATP)","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vitro biochemical assays (ATPase stimulation, aggregation suppression, binding), single lab","pmids":["26845441"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"finding":"The C-terminal EEVN motif of PfHsp70-x is important for its ATPase activity, chaperone function (protein aggregation suppression), and direct interaction with human Hsp70-Hsp90 organizing protein (hHop) in vitro; deletion of the EEVN motif (PfHsp70-xT) reduced these activities.","method":"In vitro ATPase assay, protein aggregation suppression assay, pull-down/binding assay with recombinant proteins","journal":"Proteins","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro biochemical reconstitution with deletion mutant, single lab","pmids":["30183110"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"PfHsp70-x possesses intrinsic chaperone activity (protein aggregation suppression) that is stimulated by Hsp40 co-chaperones; malonganenone A inhibits PfHsp70-x Hsp40-stimulated ATPase activity and its aggregation suppression activity, and disrupts the interaction between PfHsp70-x and Hsp40, selectively over human Hsp70.","method":"ATPase activity assay, protein aggregation suppression assay, small-molecule inhibition studies","journal":"Biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — first biochemical demonstration of PfHsp70-x chaperone activity, in vitro, single lab with multiple assays","pmids":["24854538"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"Crystallographic structures of the PfHsp70-x catalytic (ATPase) domain were resolved, revealing high similarity to human Hsp70 chaperones but identifying specific sites that may allow selective inhibition; the J-domain of its stimulatory Hsp40 co-chaperone was also structurally characterized. PfHsp70-x supports parasite growth under elevated temperature conditions simulating febrile episodes, especially early in the intraerythrocytic life cycle.","method":"X-ray crystallography, biochemical/biophysical analyses, parasite growth assays under heat stress","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystallographic structures with functional validation (growth assays), single lab but multiple orthogonal methods","pmids":["31690116"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"The crystal structure of the substrate-binding domain (SBD) of PfHsp70-x was resolved in complex with a hydrophobic peptide, showing the SBD is highly similar to the counterpart from human erythrocytic Hsp70, with conserved substrate binding at the interface between the β-sandwich and α-helical subdomains.","method":"X-ray crystallography","journal":"Acta crystallographica. Section F, Structural biology communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct crystallographic structure with functional context, single lab","pmids":["33006578"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"finding":"Fragment screening against the PfHsp70-x ATPase domain identified two binding sites, with most ligands binding proximal to the nucleotide-binding pocket; crystallographic structures of the ATPase domain in complex with three chemical fragments were determined. One non-conserved residue near the ligand-binding site distinguishes PfHsp70-x from human erythrocytic chaperones.","method":"Fragment screening, X-ray crystallography of ligand-bound ATPase domain","journal":"Acta crystallographica. Section F, Structural biology communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystallographic structures of protein-ligand complexes with explicit identification of binding sites, single lab","pmids":["34341192"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"finding":"PfHsp70-x directly interacts with the cytoplasmic tail of PfEMP1 in vitro, and simultaneously binds cholesterol-bound PFA0660w to form a ternary complex (PfHsp70-x / PFA0660w / PfEMP1); the N-terminal domain of PFA0660w and C-terminal domain of PfHsp70-x are critical for their interaction.","method":"Recombinant protein biochemical assays, direct binding assays (pull-down/co-incubation), ATPase activity assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct in vitro binding with recombinant proteins, single lab, in vivo validation not performed","pmids":["30804381"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"The exported J-domain protein PFE0055c specifically stimulates the basal ATPase activity of PfHsp70-x to a greater extent than PFA0660w, but does not significantly stimulate human Hsp70 ATPase activity, confirming a specific co-chaperone/chaperone partnership. The Hsp70 inhibitors JG231 and JG98 inhibit both basal and PFE0055c-stimulated ATPase activity of PfHsp70-x; C86 (a JDP inhibitor) only inhibits PFE0055c-stimulated activity, consistent with PFE0055c engaging PfHsp70-x via its J domain.","method":"ATPase activity assay, small-molecule inhibition studies with JDP and Hsp70 inhibitors","journal":"Cell stress & chaperones","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro biochemical assays with defined inhibitor specificity, single lab","pmids":["33236291"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"finding":"Human granzyme B (GrB) directly binds PfHsp70-x in vitro with higher affinity than for human Hsp70; the TKD motif of PfHsp70-x mediates GrB binding, and the C-terminal EEVN motif augments (but is not prerequisite for) this affinity. GrB displays antiplasmodial activity (IC50 ~0.5 µM) in vitro.","method":"ELISA, slot blot assay, surface plasmon resonance (SPR), growth inhibition assay","journal":"Cell stress & chaperones","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding demonstrated by multiple biophysical methods (ELISA, slot blot, SPR) plus functional antiplasmodial assay, single lab","pmids":["37074531"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"finding":"Skeleton binding protein 1 (SBP1) co-immunoprecipitates with PfHSP70-x in gametocyte-infected erythrocytes (identified by mass spectrometry), and some PfHSP70-x localizes to dot-like structures in the cytoplasm of immature gametocyte-infected erythrocytes, suggesting PfHSP70-x participates in protein trafficking via Maurer's clefts during gametocyte stages.","method":"Co-immunoprecipitation, mass spectrometry, immunofluorescence microscopy","journal":"Parasitology international","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP with MS identification and localization imaging, single lab","pmids":["38331312"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"finding":"In vitro ATPase assays demonstrate that isolated J-domains from three exported PfJDPs (PFA0660w, PFE0055c, and a third homolog) all stimulate the ATPase activity of PfHSP70-x (as well as human HsHSP70 and HsHSC70), with differences observed in stimulation magnitude between individual PfJDP-HSP70 pairings, supporting a model where the parasite exports JDPs to exploit host chaperone machinery.","method":"In vitro ATPase activity assay with recombinant J-domain fragments and recombinant HSP70 proteins","journal":"FEBS open bio","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct in vitro biochemical reconstitution with purified components, single lab","pmids":["41618743"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"finding":"In a PfVps60 knockout line disrupting ESCRT-dependent vesicular trafficking, PfHsp70-x was reduced among EV-associated cargo during thermal stress, and protein aggregates redistributed near the parasitophorous vacuole, indicating that PfHsp70-x is normally exported via EV-mediated trafficking as part of the parasite's proteostasis response to heat shock.","method":"Gene knockout (PfVps60KO), proteomic profiling of extracellular vesicle cargo, fluorescence microscopy of protein aggregates, parasite viability assays","journal":"Emerging microbes & infections","confidence":"Low","confidence_rationale":"Tier 3 / Weak — PfHsp70-x finding is secondary to the study's main focus on PfVps60/EVs; indirect evidence from proteomics of KO parasites, single lab","pmids":["42253101"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]}],"current_model":"PfHsp70-x (PF3D7_0831700) is a parasite-encoded Hsp70-class chaperone that is exported to the host erythrocyte via an N-terminal secretory signal followed by a short targeting motif (requiring PTEX for translocation across the parasitophorous vacuole membrane and acetylated rather than cleaved), where it localizes to J-dots and Maurer's clefts, forms complexes with exported Hsp40 co-chaperones (PFA0660w/PFE0055c) that specifically stimulate its ATPase activity, directly binds PfEMP1, supports efficient PfEMP1 export and cytoadherence as well as parasite growth during febrile episodes, and engages human granzyme B via its conserved TKD motif — yet is dispensable for intraerythrocytic growth under standard in vitro conditions."},"narrative":{"mechanistic_narrative":"PF3D7_0831700 (HSP70x) is a Plasmodium falciparum-encoded Hsp70-class molecular chaperone that is exported into the host erythrocyte, where it supports the trafficking and surface display of parasite virulence proteins [PMID:22925632, PMID:28732045]. It is expressed maximally at the schizont stage and traffics from the parasite through the parasitophorous vacuole into the host cell, localizing to mobile J-dots and to Maurer's clefts [PMID:22925632, PMID:23340228]. Export depends on a short 7-residue targeting motif immediately downstream of an N-terminal hydrophobic secretory signal; this signal is acetylated rather than cleaved (unlike PEXEL proteins), and translocation across the parasitophorous vacuole membrane requires the PTEX translocon [PMID:27824087]. Within the host cell HSP70x assembles with the exported Hsp40/J-domain co-chaperones PFA0660w and PFE0055c, which selectively stimulate its ATPase activity relative to human Hsp70, and it directly binds the cytoplasmic tail of PfEMP1, forming a ternary chaperone complex that promotes PfEMP1 export and cytoadherence [PMID:26845441, PMID:30804381, PMID:33236291]. Functionally, HSP70x is dispensable for intraerythrocytic growth under standard conditions, but its loss delays PfEMP1 export, reduces adhesion, and increases infected-erythrocyte rigidity, and the chaperone specifically supports parasite growth under febrile-temperature heat stress [PMID:28732045, PMID:28959740, PMID:31690116]. Its catalytic (ATPase) and substrate-binding domains have been crystallized and closely resemble human erythrocytic Hsp70, though non-conserved residues near the nucleotide-binding pocket provide handles for selective inhibition [PMID:31690116, PMID:33006578, PMID:34341192]. The chaperone is also directly engaged by human granzyme B via its conserved TKD motif, and its C-terminal EEVN motif contributes to ATPase activity, co-chaperone interaction, and binding to human Hop [PMID:30183110, PMID:37074531].","teleology":[{"year":2012,"claim":"Established that HSP70x is a parasite chaperone that actually functions inside the host cell rather than the parasite, defining its unusual exported role.","evidence":"Co-IP, immunofluorescence, and fractionation localizing it to J-dots with exported Hsp40s and PfEMP1","pmids":["22925632"],"confidence":"High","gaps":["Did not establish the export signal or translocation route","Association with PfEMP1 not shown to be direct"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"claim":"Refined the localization by showing stage-specific (schizont) expression with a parasitophorous-vacuole pool and a partial exported pool at Maurer's clefts, and confirmed the gene is functional.","evidence":"Dual-detergent fractionation and immunofluorescence with peptide-specific antiserum","pmids":["23340228"],"confidence":"Medium","gaps":["Mechanism partitioning PV-retained versus exported protein unknown","Single-lab localization"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"claim":"Provided the first biochemical demonstration that HSP70x has intrinsic chaperone activity and is Hsp40-stimulated, and that it can be selectively inhibited over human Hsp70.","evidence":"In vitro ATPase and aggregation-suppression assays with malonganenone A inhibition","pmids":["24854538"],"confidence":"Medium","gaps":["In vitro only","Physiological substrates not identified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"claim":"Defined the export determinant and its unusual processing, and identified PFA0660w as a functionally selective co-chaperone, together explaining how HSP70x reaches and operates in the host cell.","evidence":"Mutagenesis/GFP reporters plus acetylation mass spectrometry (export); ATPase and binding assays (co-chaperone selectivity)","pmids":["27824087","26845441"],"confidence":"High","gaps":["Machinery reading the non-cleaved acetylated motif unknown","Structural basis of PFA0660w selectivity not resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2017,"claim":"Tested essentiality and virulence roles genetically, converging on a model in which HSP70x is dispensable for growth but contributes to PfEMP1 export and cytoadherence.","evidence":"Two independent knockout/knockdown studies with cytoadherence, rigidity, and export readouts","pmids":["28732045","28959740"],"confidence":"High","gaps":["The two studies differ on whether PfEMP1 export is affected","Molecular step where HSP70x acts on PfEMP1 not pinpointed"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2018,"claim":"Mapped functional roles to the C-terminal EEVN motif, linking it to ATPase activity, chaperone function, and Hop interaction.","evidence":"In vitro ATPase, aggregation-suppression, and pull-down assays with an EEVN-deletion mutant","pmids":["30183110"],"confidence":"Medium","gaps":["Hop interaction not validated in vivo","Single-lab in vitro reconstitution"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2019,"claim":"Provided direct biochemical evidence for the PfEMP1-chaperone ternary complex and, structurally, resolved the ATPase domain while linking HSP70x to survival under febrile heat stress.","evidence":"Recombinant ternary-complex binding/ATPase assays; X-ray crystallography plus heat-stress growth assays","pmids":["30804381","31690116"],"confidence":"Medium","gaps":["Ternary complex not validated in vivo","How heat-stress protection relates to PfEMP1 role unclear"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"Extended the structural and co-chaperone picture by resolving the substrate-binding domain and showing PFE0055c is a stronger, still parasite-selective ATPase stimulator with defined inhibitor pharmacology.","evidence":"X-ray crystallography of SBD-peptide complex; ATPase assays with JDP/Hsp70 inhibitors","pmids":["33006578","33236291"],"confidence":"Medium","gaps":["High similarity to human Hsp70 complicates selective targeting","Relative in vivo roles of PFA0660w vs PFE0055c unknown"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2021,"claim":"Identified druggable pockets on the ATPase domain and a distinguishing non-conserved residue, advancing HSP70x as a selective antimalarial target.","evidence":"Fragment screening and crystallography of ligand-bound ATPase domain","pmids":["34341192"],"confidence":"High","gaps":["No potent lead compound established","Cellular efficacy not demonstrated"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2023,"claim":"Revealed a host-immune interaction, showing human granzyme B binds HSP70x via its TKD motif with antiplasmodial consequences.","evidence":"ELISA, slot blot, SPR binding, and growth inhibition assays","pmids":["37074531"],"confidence":"Medium","gaps":["In vivo relevance of GrB engagement unknown","Mechanism of antiplasmodial activity unresolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2024,"claim":"Extended the trafficking role to sexual stages by linking HSP70x to SBP1 and Maurer's-cleft-associated structures in gametocyte-infected cells.","evidence":"Co-IP/mass spectrometry and immunofluorescence in gametocyte-infected erythrocytes","pmids":["38331312"],"confidence":"Medium","gaps":["Functional consequence of the SBP1 interaction not tested","Single Co-IP without reciprocal validation"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2026,"claim":"Two studies further probed co-chaperone promiscuity and the export route, suggesting exported JDPs can also stimulate human Hsp70s and that EV/ESCRT trafficking contributes to HSP70x export during heat stress.","evidence":"In vitro ATPase assays with J-domain fragments; PfVps60 knockout with EV proteomics","pmids":["41618743","42253101"],"confidence":"Low","gaps":["EV-export evidence is indirect and secondary to a PfVps60-focused study","Whether host-Hsp70 hijacking occurs in vivo is untested"],"attribution":[{"species":"Plasmodium falciparum","strain":"3D7"}]},{"year":null,"claim":"The endogenous substrate repertoire of HSP70x in the host cell and the mechanistic step by which the chaperone complex promotes PfEMP1 surface display remain undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No comprehensive in-cell client identification","Structural basis of PfEMP1 tail recognition unresolved","Discrepant KO phenotypes on PfEMP1 export not reconciled"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":["PfHsp70-x / PFA0660w J-dot chaperone complex","PfHsp70-x / PFA0660w / PfEMP1 ternary complex","PfHsp70-x / PFE0055c chaperone-cochaperone pair"],"partners":["PFA0660W (EXPORTED HSP40/J-DOMAIN PROTEIN)","PFE0055C (EXPORTED J-DOMAIN PROTEIN)","PFEMP1 (CYTOPLASMIC TAIL)","HUMAN HOP (HSP70-HSP90 ORGANIZING PROTEIN)","HUMAN GRANZYME B","SBP1 (SKELETON BINDING PROTEIN 1)","PTEX TRANSLOCON (EXPORT REQUIREMENT)"],"other_free_text":["Exported via a non-cleaved, acetylated N-terminal targeting motif requiring a 7-residue signal and PTEX [#2]","Dispensable for intraerythrocytic growth in vitro but supports growth under febrile heat stress [#3, #4, #8]","ATPase and substrate-binding domains are structurally close to human erythrocytic Hsp70, with non-conserved residues enabling selective inhibitor design [#8, #9, #10]","GrB binding mediated by the conserved TKD motif; EEVN motif augments affinity [#13]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"8153120","id":"PMC_8153120","title":"Demonstration of heat-shock protein 70 in the sporozoite stage of malaria parasites.","date":"1994","source":"Parasitology research","url":"https://pubmed.ncbi.nlm.nih.gov/8153120","citation_count":182,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["heat shock protein 70"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"3095842","id":"PMC_3095842","title":"A repetitive antigen of Plasmodium falciparum that is homologous to heat shock protein 70 of Drosophila melanogaster.","date":"1986","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/3095842","citation_count":159,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["heat shock protein 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Section F, Structural biology communications","url":"https://pubmed.ncbi.nlm.nih.gov/34341192","citation_count":3,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["heat shock protein 70","PfHSP70x"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"19523215","id":"PMC_19523215","title":"The effect of mimicking febrile temperature and drug stress on malarial development.","date":"2009","source":"Annals of clinical microbiology and antimicrobials","url":"https://pubmed.ncbi.nlm.nih.gov/19523215","citation_count":3,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["heat shock protein 70"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":37785,"output_tokens":4673,"usd":0.091725,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11031,"output_tokens":4706,"usd":0.086402,"stage2_stop_reason":"end_turn"},"total_usd":0.178127,"stage1_batch_id":"msgbatch_01DisAaTypwmC8QwdMBuePHo","stage2_batch_id":"msgbatch_0184zxZTqxiEfdYYfPMfkqjb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2012,\n      \"finding\": \"HSP70x (PfHsp70-x) is exported to the host erythrocyte where it forms a complex with exported PfHsp40s (PFA0660w and PFE55) in mobile structures termed J-dots, and is closely associated with PfEMP1; the protein was identified as a parasite-encoded chaperone operating within the host cell.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence microscopy, subcellular fractionation, Western blotting\",\n      \"journal\": \"Cellular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP and multiple orthogonal imaging/fractionation methods; replicated by subsequent independent studies\",\n      \"pmids\": [\"22925632\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PfHsp70-x is expressed maximally at the schizont stage, localizes primarily to the parasitophorous vacuole, and a portion is exported to the erythrocyte compartment where it associates with Maurer's clefts; it carries an endoplasmic reticulum signal peptide and is encoded by a functional (not pseudo) gene.\",\n      \"method\": \"Subcellular fractionation (saponin and streptolysin-O), immunofluorescence, immunoblotting with peptide-specific antiserum\",\n      \"journal\": \"Parasite (Paris, France)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization by two fractionation methods and immunofluorescence, single lab\",\n      \"pmids\": [\"23340228\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Trafficking of PfHsp70-x to the host erythrocyte requires a 7 amino acid motif directly following the hydrophobic N-terminal secretory signal; both reversed and scrambled versions of the motif retained export capacity, but site-directed mutagenesis of glutamate residues within this region blocked trafficking within the parasitophorous vacuole lumen. Unlike PEXEL-containing proteins, the targeting signal is not cleaved but is acetylated. Export also requires the vacuolar translocon PTEX.\",\n      \"method\": \"Site-directed mutagenesis, GFP reporter constructs, immunofluorescence microscopy, mass spectrometry (acetylation detection)\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — mutagenesis with defined molecular phenotype plus PTM characterization, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"27824087\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Knockout of PfHsp70-x (Δhsp70-x) did not affect parasite growth in vitro, but delayed export of PfEMP1 cytoadherence proteins and resulted in reduced adhesion of infected erythrocytes and increased rigidity of infected erythrocytes compared to wild-type controls.\",\n      \"method\": \"Gene knockout, cytoadherence assays, erythrocyte rigidity measurements, transcriptional and translational profiling\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with multiple defined phenotypic readouts; independently replicated by a second KO study (PMID:28959740)\",\n      \"pmids\": [\"28732045\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Complete CRISPR/Cas9 gene knockout of PfHsp70x, as well as knockdown using DHFR-based destabilization domain and glmS ribozyme, did not affect P. falciparum intraerythrocytic growth or export of PfEMP1 to the host RBC.\",\n      \"method\": \"CRISPR/Cas9 gene knockout, conditional knockdown (DHFR destabilization domain, glmS ribozyme), immunofluorescence, growth assays\",\n      \"journal\": \"mSphere\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent conditional knockdown systems plus complete KO, multiple assays; negative result for essentiality rigorously established\",\n      \"pmids\": [\"28959740\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PFA0660w (an exported Hsp40/J-domain protein) specifically stimulates the ATPase activity of PfHsp70-x but not that of PfHsp70-1 or human Hsp70, indicating a selective functional co-chaperone/chaperone partnership; protein binding studies confirmed a direct interaction dependent on the J domain.\",\n      \"method\": \"ATPase activity assay, protein aggregation suppression assay, co-chaperone binding studies (protein binding in presence/absence of ATP)\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vitro biochemical assays (ATPase stimulation, aggregation suppression, binding), single lab\",\n      \"pmids\": [\"26845441\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The C-terminal EEVN motif of PfHsp70-x is important for its ATPase activity, chaperone function (protein aggregation suppression), and direct interaction with human Hsp70-Hsp90 organizing protein (hHop) in vitro; deletion of the EEVN motif (PfHsp70-xT) reduced these activities.\",\n      \"method\": \"In vitro ATPase assay, protein aggregation suppression assay, pull-down/binding assay with recombinant proteins\",\n      \"journal\": \"Proteins\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro biochemical reconstitution with deletion mutant, single lab\",\n      \"pmids\": [\"30183110\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PfHsp70-x possesses intrinsic chaperone activity (protein aggregation suppression) that is stimulated by Hsp40 co-chaperones; malonganenone A inhibits PfHsp70-x Hsp40-stimulated ATPase activity and its aggregation suppression activity, and disrupts the interaction between PfHsp70-x and Hsp40, selectively over human Hsp70.\",\n      \"method\": \"ATPase activity assay, protein aggregation suppression assay, small-molecule inhibition studies\",\n      \"journal\": \"Biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — first biochemical demonstration of PfHsp70-x chaperone activity, in vitro, single lab with multiple assays\",\n      \"pmids\": [\"24854538\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Crystallographic structures of the PfHsp70-x catalytic (ATPase) domain were resolved, revealing high similarity to human Hsp70 chaperones but identifying specific sites that may allow selective inhibition; the J-domain of its stimulatory Hsp40 co-chaperone was also structurally characterized. PfHsp70-x supports parasite growth under elevated temperature conditions simulating febrile episodes, especially early in the intraerythrocytic life cycle.\",\n      \"method\": \"X-ray crystallography, biochemical/biophysical analyses, parasite growth assays under heat stress\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystallographic structures with functional validation (growth assays), single lab but multiple orthogonal methods\",\n      \"pmids\": [\"31690116\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The crystal structure of the substrate-binding domain (SBD) of PfHsp70-x was resolved in complex with a hydrophobic peptide, showing the SBD is highly similar to the counterpart from human erythrocytic Hsp70, with conserved substrate binding at the interface between the β-sandwich and α-helical subdomains.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Acta crystallographica. Section F, Structural biology communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct crystallographic structure with functional context, single lab\",\n      \"pmids\": [\"33006578\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Fragment screening against the PfHsp70-x ATPase domain identified two binding sites, with most ligands binding proximal to the nucleotide-binding pocket; crystallographic structures of the ATPase domain in complex with three chemical fragments were determined. One non-conserved residue near the ligand-binding site distinguishes PfHsp70-x from human erythrocytic chaperones.\",\n      \"method\": \"Fragment screening, X-ray crystallography of ligand-bound ATPase domain\",\n      \"journal\": \"Acta crystallographica. Section F, Structural biology communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystallographic structures of protein-ligand complexes with explicit identification of binding sites, single lab\",\n      \"pmids\": [\"34341192\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PfHsp70-x directly interacts with the cytoplasmic tail of PfEMP1 in vitro, and simultaneously binds cholesterol-bound PFA0660w to form a ternary complex (PfHsp70-x / PFA0660w / PfEMP1); the N-terminal domain of PFA0660w and C-terminal domain of PfHsp70-x are critical for their interaction.\",\n      \"method\": \"Recombinant protein biochemical assays, direct binding assays (pull-down/co-incubation), ATPase activity assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct in vitro binding with recombinant proteins, single lab, in vivo validation not performed\",\n      \"pmids\": [\"30804381\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The exported J-domain protein PFE0055c specifically stimulates the basal ATPase activity of PfHsp70-x to a greater extent than PFA0660w, but does not significantly stimulate human Hsp70 ATPase activity, confirming a specific co-chaperone/chaperone partnership. The Hsp70 inhibitors JG231 and JG98 inhibit both basal and PFE0055c-stimulated ATPase activity of PfHsp70-x; C86 (a JDP inhibitor) only inhibits PFE0055c-stimulated activity, consistent with PFE0055c engaging PfHsp70-x via its J domain.\",\n      \"method\": \"ATPase activity assay, small-molecule inhibition studies with JDP and Hsp70 inhibitors\",\n      \"journal\": \"Cell stress & chaperones\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro biochemical assays with defined inhibitor specificity, single lab\",\n      \"pmids\": [\"33236291\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Human granzyme B (GrB) directly binds PfHsp70-x in vitro with higher affinity than for human Hsp70; the TKD motif of PfHsp70-x mediates GrB binding, and the C-terminal EEVN motif augments (but is not prerequisite for) this affinity. GrB displays antiplasmodial activity (IC50 ~0.5 µM) in vitro.\",\n      \"method\": \"ELISA, slot blot assay, surface plasmon resonance (SPR), growth inhibition assay\",\n      \"journal\": \"Cell stress & chaperones\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding demonstrated by multiple biophysical methods (ELISA, slot blot, SPR) plus functional antiplasmodial assay, single lab\",\n      \"pmids\": [\"37074531\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Skeleton binding protein 1 (SBP1) co-immunoprecipitates with PfHSP70-x in gametocyte-infected erythrocytes (identified by mass spectrometry), and some PfHSP70-x localizes to dot-like structures in the cytoplasm of immature gametocyte-infected erythrocytes, suggesting PfHSP70-x participates in protein trafficking via Maurer's clefts during gametocyte stages.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, immunofluorescence microscopy\",\n      \"journal\": \"Parasitology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP with MS identification and localization imaging, single lab\",\n      \"pmids\": [\"38331312\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In vitro ATPase assays demonstrate that isolated J-domains from three exported PfJDPs (PFA0660w, PFE0055c, and a third homolog) all stimulate the ATPase activity of PfHSP70-x (as well as human HsHSP70 and HsHSC70), with differences observed in stimulation magnitude between individual PfJDP-HSP70 pairings, supporting a model where the parasite exports JDPs to exploit host chaperone machinery.\",\n      \"method\": \"In vitro ATPase activity assay with recombinant J-domain fragments and recombinant HSP70 proteins\",\n      \"journal\": \"FEBS open bio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct in vitro biochemical reconstitution with purified components, single lab\",\n      \"pmids\": [\"41618743\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In a PfVps60 knockout line disrupting ESCRT-dependent vesicular trafficking, PfHsp70-x was reduced among EV-associated cargo during thermal stress, and protein aggregates redistributed near the parasitophorous vacuole, indicating that PfHsp70-x is normally exported via EV-mediated trafficking as part of the parasite's proteostasis response to heat shock.\",\n      \"method\": \"Gene knockout (PfVps60KO), proteomic profiling of extracellular vesicle cargo, fluorescence microscopy of protein aggregates, parasite viability assays\",\n      \"journal\": \"Emerging microbes & infections\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — PfHsp70-x finding is secondary to the study's main focus on PfVps60/EVs; indirect evidence from proteomics of KO parasites, single lab\",\n      \"pmids\": [\"42253101\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    }\n  ],\n  \"current_model\": \"PfHsp70-x (PF3D7_0831700) is a parasite-encoded Hsp70-class chaperone that is exported to the host erythrocyte via an N-terminal secretory signal followed by a short targeting motif (requiring PTEX for translocation across the parasitophorous vacuole membrane and acetylated rather than cleaved), where it localizes to J-dots and Maurer's clefts, forms complexes with exported Hsp40 co-chaperones (PFA0660w/PFE0055c) that specifically stimulate its ATPase activity, directly binds PfEMP1, supports efficient PfEMP1 export and cytoadherence as well as parasite growth during febrile episodes, and engages human granzyme B via its conserved TKD motif — yet is dispensable for intraerythrocytic growth under standard in vitro conditions.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_0831700 (HSP70x) is a Plasmodium falciparum-encoded Hsp70-class molecular chaperone that is exported into the host erythrocyte, where it supports the trafficking and surface display of parasite virulence proteins [#0, #3]. It is expressed maximally at the schizont stage and traffics from the parasite through the parasitophorous vacuole into the host cell, localizing to mobile J-dots and to Maurer's clefts [#0, #1]. Export depends on a short 7-residue targeting motif immediately downstream of an N-terminal hydrophobic secretory signal; this signal is acetylated rather than cleaved (unlike PEXEL proteins), and translocation across the parasitophorous vacuole membrane requires the PTEX translocon [#2]. Within the host cell HSP70x assembles with the exported Hsp40/J-domain co-chaperones PFA0660w and PFE0055c, which selectively stimulate its ATPase activity relative to human Hsp70, and it directly binds the cytoplasmic tail of PfEMP1, forming a ternary chaperone complex that promotes PfEMP1 export and cytoadherence [#5, #11, #12]. Functionally, HSP70x is dispensable for intraerythrocytic growth under standard conditions, but its loss delays PfEMP1 export, reduces adhesion, and increases infected-erythrocyte rigidity, and the chaperone specifically supports parasite growth under febrile-temperature heat stress [#3, #4, #8]. Its catalytic (ATPase) and substrate-binding domains have been crystallized and closely resemble human erythrocytic Hsp70, though non-conserved residues near the nucleotide-binding pocket provide handles for selective inhibition [#8, #9, #10]. The chaperone is also directly engaged by human granzyme B via its conserved TKD motif, and its C-terminal EEVN motif contributes to ATPase activity, co-chaperone interaction, and binding to human Hop [#6, #13].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Established that HSP70x is a parasite chaperone that actually functions inside the host cell rather than the parasite, defining its unusual exported role.\",\n      \"evidence\": \"Co-IP, immunofluorescence, and fractionation localizing it to J-dots with exported Hsp40s and PfEMP1\",\n      \"pmids\": [\"22925632\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish the export signal or translocation route\", \"Association with PfEMP1 not shown to be direct\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Refined the localization by showing stage-specific (schizont) expression with a parasitophorous-vacuole pool and a partial exported pool at Maurer's clefts, and confirmed the gene is functional.\",\n      \"evidence\": \"Dual-detergent fractionation and immunofluorescence with peptide-specific antiserum\",\n      \"pmids\": [\"23340228\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism partitioning PV-retained versus exported protein unknown\", \"Single-lab localization\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Provided the first biochemical demonstration that HSP70x has intrinsic chaperone activity and is Hsp40-stimulated, and that it can be selectively inhibited over human Hsp70.\",\n      \"evidence\": \"In vitro ATPase and aggregation-suppression assays with malonganenone A inhibition\",\n      \"pmids\": [\"24854538\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vitro only\", \"Physiological substrates not identified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the export determinant and its unusual processing, and identified PFA0660w as a functionally selective co-chaperone, together explaining how HSP70x reaches and operates in the host cell.\",\n      \"evidence\": \"Mutagenesis/GFP reporters plus acetylation mass spectrometry (export); ATPase and binding assays (co-chaperone selectivity)\",\n      \"pmids\": [\"27824087\", \"26845441\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Machinery reading the non-cleaved acetylated motif unknown\", \"Structural basis of PFA0660w selectivity not resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Tested essentiality and virulence roles genetically, converging on a model in which HSP70x is dispensable for growth but contributes to PfEMP1 export and cytoadherence.\",\n      \"evidence\": \"Two independent knockout/knockdown studies with cytoadherence, rigidity, and export readouts\",\n      \"pmids\": [\"28732045\", \"28959740\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The two studies differ on whether PfEMP1 export is affected\", \"Molecular step where HSP70x acts on PfEMP1 not pinpointed\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Mapped functional roles to the C-terminal EEVN motif, linking it to ATPase activity, chaperone function, and Hop interaction.\",\n      \"evidence\": \"In vitro ATPase, aggregation-suppression, and pull-down assays with an EEVN-deletion mutant\",\n      \"pmids\": [\"30183110\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Hop interaction not validated in vivo\", \"Single-lab in vitro reconstitution\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Provided direct biochemical evidence for the PfEMP1-chaperone ternary complex and, structurally, resolved the ATPase domain while linking HSP70x to survival under febrile heat stress.\",\n      \"evidence\": \"Recombinant ternary-complex binding/ATPase assays; X-ray crystallography plus heat-stress growth assays\",\n      \"pmids\": [\"30804381\", \"31690116\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ternary complex not validated in vivo\", \"How heat-stress protection relates to PfEMP1 role unclear\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended the structural and co-chaperone picture by resolving the substrate-binding domain and showing PFE0055c is a stronger, still parasite-selective ATPase stimulator with defined inhibitor pharmacology.\",\n      \"evidence\": \"X-ray crystallography of SBD-peptide complex; ATPase assays with JDP/Hsp70 inhibitors\",\n      \"pmids\": [\"33006578\", \"33236291\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"High similarity to human Hsp70 complicates selective targeting\", \"Relative in vivo roles of PFA0660w vs PFE0055c unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified druggable pockets on the ATPase domain and a distinguishing non-conserved residue, advancing HSP70x as a selective antimalarial target.\",\n      \"evidence\": \"Fragment screening and crystallography of ligand-bound ATPase domain\",\n      \"pmids\": [\"34341192\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No potent lead compound established\", \"Cellular efficacy not demonstrated\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a host-immune interaction, showing human granzyme B binds HSP70x via its TKD motif with antiplasmodial consequences.\",\n      \"evidence\": \"ELISA, slot blot, SPR binding, and growth inhibition assays\",\n      \"pmids\": [\"37074531\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance of GrB engagement unknown\", \"Mechanism of antiplasmodial activity unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended the trafficking role to sexual stages by linking HSP70x to SBP1 and Maurer's-cleft-associated structures in gametocyte-infected cells.\",\n      \"evidence\": \"Co-IP/mass spectrometry and immunofluorescence in gametocyte-infected erythrocytes\",\n      \"pmids\": [\"38331312\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the SBP1 interaction not tested\", \"Single Co-IP without reciprocal validation\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Two studies further probed co-chaperone promiscuity and the export route, suggesting exported JDPs can also stimulate human Hsp70s and that EV/ESCRT trafficking contributes to HSP70x export during heat stress.\",\n      \"evidence\": \"In vitro ATPase assays with J-domain fragments; PfVps60 knockout with EV proteomics\",\n      \"pmids\": [\"41618743\", \"42253101\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"EV-export evidence is indirect and secondary to a PfVps60-focused study\", \"Whether host-Hsp70 hijacking occurs in vivo is untested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"3D7\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The endogenous substrate repertoire of HSP70x in the host cell and the mechanistic step by which the chaperone complex promotes PfEMP1 surface display remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No comprehensive in-cell client identification\", \"Structural basis of PfEMP1 tail recognition unresolved\", \"Discrepant KO phenotypes on PfEMP1 export not reconciled\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140662\", \"supporting_discovery_ids\": [5, 6, 7, 8, 12, 15]},\n      {\"term_id\": \"GO:0051082\", \"supporting_discovery_ids\": [7, 6, 9]},\n      {\"term_id\": \"GO:0051087\", \"supporting_discovery_ids\": [11, 13, 6]},\n      {\"term_id\": \"GO:0005524\", \"supporting_discovery_ids\": [8, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0020030\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0020036\", \"supporting_discovery_ids\": [0, 14]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 16]},\n      {\"term_id\": \"GO:0020002\", \"supporting_discovery_ids\": [0, 3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0006457\", \"supporting_discovery_ids\": [7, 8, 16]},\n      {\"term_id\": \"GO:0046718\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0007155\", \"supporting_discovery_ids\": [3, 11]},\n      {\"term_id\": \"GO:0009408\", \"supporting_discovery_ids\": [8, 16]}\n    ],\n    \"complexes\": [\n      \"PfHsp70-x / PFA0660w J-dot chaperone complex\",\n      \"PfHsp70-x / PFA0660w / PfEMP1 ternary complex\",\n      \"PfHsp70-x / PFE0055c chaperone-cochaperone pair\"\n    ],\n    \"partners\": [\n      \"PFA0660w (exported Hsp40/J-domain protein)\",\n      \"PFE0055c (exported J-domain protein)\",\n      \"PfEMP1 (cytoplasmic tail)\",\n      \"human Hop (Hsp70-Hsp90 organizing protein)\",\n      \"human granzyme B\",\n      \"SBP1 (skeleton binding protein 1)\",\n      \"PTEX translocon (export requirement)\"\n    ],\n    \"other_free_text\": [\n      \"Exported via a non-cleaved, acetylated N-terminal targeting motif requiring a 7-residue signal and PTEX [#2]\",\n      \"Dispensable for intraerythrocytic growth in vitro but supports growth under febrile heat stress [#3, #4, #8]\",\n      \"ATPase and substrate-binding domains are structurally close to human erythrocytic Hsp70, with non-conserved residues enabling selective inhibitor design [#8, #9, #10]\",\n      \"GrB binding mediated by the conserved TKD motif; EEVN motif augments affinity [#13]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0831700","name":null,"product":"heat shock protein 70","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"HSP70x","evaluation":null}