Affinage · Plasmodium

Showing PF3D7_1116800 — HSP101 is a alias.

HSP101

PF3D7_1116800 · heat shock protein 101

Annotated
2026-09-08
30 papers in source corpus 20 papers cited in narrative 19 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

HSP101 (PF3D7_1116800) is a ClpA/B-like AAA+ ATPase that serves as the essential motor subunit of the Plasmodium translocon of exported proteins (PTEX), the machine that drives export of parasite effector proteins across the parasitophorous vacuole membrane (PVM) into the host erythrocyte (PMID:19536257, PMID:25043010). Together with PTEX150 and the membrane channel EXP2 it forms a stable, high-molecular-weight complex assembled at the PVM after invasion, having been delivered from merozoite dense granules during schizogony (PMID:19536257, PMID:22253438). Cryo-EM of the endogenous complex shows HSP101 as a spiral AAA+ hexamer poised above the EXP2–PTEX150 funnel, whose tyrosine-bearing pore loops grip cargo and, through a compaction/'resetting' conformational cycle, thread substrate through the channel (PMID:30150771). Conditional inactivation of HSP101 blocks export of all classes of exported cargo — PEXEL proteins, PEXEL-negative exported proteins, and the virulence factor PfEMP1 — causing substrate accumulation in the vacuole and severe growth impairment, and it is required for the protein-conducting but not the nutrient-channel activity of EXP2 (PMID:25043010, PMID:25043043, PMID:30150733). Uncoupling mutants establish that HSP101 provides the unfoldase activity specifically needed to translocate tightly folded soluble cargo, whereas transmembrane-domain cargo accesses an alternative unfolding route (PMID:31164473). Beyond the vacuole, HSP101 also localizes to the parasite ER, where it recognizes and escorts PEXEL proteins toward the PVM for docking onto the EXP2–PTEX150 subcomplex (PMID:35192672), and is maintained in the vacuole in functional excess relative to the minimum required to sustain export (PMID:37552754). Attempted deletion in P. berghei failed, indicating HSP101 is essential for blood-stage development (PMID:23869529, PMID:24076174).

Mechanistic history

Synthesis pass · year-by-year structured walk · 16 steps
  1. 2009 High

    Establishing that a dedicated machine exports parasite proteins into the host cell required identifying its components; HSP101 was defined as the AAA+ ATPase of the PVM-resident PTEX complex.

    Evidence Co-IP, mass spectrometry, immuno-EM localizing HSP101 with PTEX150 and EXP2 in P. falciparum

    PMID:19536257

    Open questions at the time
    • Did not demonstrate ATP-driven translocation directly
    • Stoichiometry and architecture of the complex unresolved
  2. 2012 High

    How and when the translocon reaches the PVM was unknown; HSP101 was shown to be pre-packaged in merozoite dense granules and discharged into the nascent PVM to assemble a stable >1230 kDa complex.

    Evidence Immunofluorescence, subcellular fractionation, blue native PAGE, immuno-EM in P. falciparum

    PMID:22253438

    Open questions at the time
    • Trigger and mechanism of dense-granule discharge not defined
    • Assembly order at the PVM inferred, not directly observed
  3. 2013 Medium

    Whether HSP101 is dispensable was tested genetically; failure to delete it in P. berghei established essentiality for blood-stage development.

    Evidence Attempted reverse-genetic gene deletion in P. berghei

    PMID:23869529 PMID:24076174

    Open questions at the time
    • Negative deletion result does not identify the essential function
    • No conditional confirmation in this species
  4. 2014 High

    Whether HSP101 is functionally required for export, not merely present, was resolved by conditional inactivation, which blocked export of all cargo classes and showed complex integrity is needed.

    Evidence Chaperone auto-inhibition/dominant-negative and inducible knockdown with export assays, IF, Co-IP, and growth assays in P. falciparum

    PMID:25043010 PMID:25043043

    Open questions at the time
    • Did not separate ATPase/unfoldase from complex-scaffolding roles
    • Mechanism of cargo recognition not addressed
  5. 2014 Low

    A candidate ER-based processing step for HSP101 was proposed by identifying it as a substrate of P. falciparum signal peptide peptidase.

    Evidence Transfection-based in vivo luminescence assay and bioinformatic substrate screen in P. falciparum

    PMID:25017910

    Open questions at the time
    • Single lab, single method with no mechanistic follow-up
    • Physiological consequence of cleavage for PTEX function not shown
  6. 2015 Medium

    Life-cycle localization of HSP101 was examined, revealing PV tubular extensions in blood stages and stage-specific expression, while its absence in early liver stages was linked to the lack of PEXEL translocation there.

    Evidence Endogenous fluorescent tagging, live imaging, CLEM, IF and reporter export assays in P. berghei

    PMID:26219962 PMID:26347246

    Open questions at the time
    • Function of PV tubular extensions unresolved
    • Causality between HSP101 absence and liver-stage export block not proven
  7. 2018 High

    The molecular mechanism of translocation was resolved by cryo-EM, showing HSP101 as a spiral hexamer whose tyrosine pore loops thread cargo through the EXP2–PTEX150 channel via an engaged/resetting cycle.

    Evidence Near-atomic cryo-EM of endogenous complex captured in engaged and resetting states, with CRISPR-Cas9 epitope tagging, in P. falciparum

    PMID:30150771

    Open questions at the time
    • ATP hydrolysis coupling to the conformational cycle inferred from static states
    • Cargo entry/recognition at the hexamer not resolved
  8. 2018 High

    Whether HSP101 governs EXP2's transport versus channel functions was separated; HSP101 is required for the protein-conducting activity but not the independent nutrient channel of EXP2.

    Evidence Regulated expression, export assays, and cell-attached patch-clamp in P. falciparum

    PMID:30150733

    Open questions at the time
    • How EXP2 switches between roles not defined
  9. 2018 Medium

    Spatial organization of the translocon under stalled export was probed, showing HSP101/PTEX150 remain in export zones while trapped cargo and EXP2 can be segregated, and that PTEX88 associates most closely with HSP101.

    Evidence Inducible folding reporters and IF (Traffic); IP and quantitative MS interactome (FEBS J) in P. falciparum

    PMID:29637707 PMID:29696751

    Open questions at the time
    • Functional role of PTEX88–HSP101 interaction unclear
    • Meaning of EXP2/cargo segregation for normal export uncertain
  10. 2019 High

    Whether HSP101's unfoldase activity is universally required was resolved by uncoupling mutants, showing it is essential for tightly folded soluble cargo but that transmembrane cargo uses an alternative unfolding pathway.

    Evidence Transgenic parasites with uncoupled unfoldase/threading functions and reporter export assays in P. falciparum

    PMID:31164473

    Open questions at the time
    • Nature of the alternative unfolding pathway for TM cargo unidentified
    • Single lab
  11. 2020 Medium

    The dependency of HSP101 organization on other PVM proteins was tested; EXP1 organizes EXP2 but not HSP101, indicating separable determinants of translocon architecture.

    Evidence Conditional knockdown (TetR-DOZI), IF, EM, and BioID in P. falciparum

    PMID:31990132

    Open questions at the time
    • Determinants that position HSP101 in the PVM remain unknown
  12. 2021 Medium

    Whether restoring HSP101 alone could enable liver-stage export was tested; reconstituted HSP101 was insufficient, implicating additional missing components or an alternative export complex in liver stages.

    Evidence Promoter-swap/extra-copy transgenic P. berghei with PEXEL reporter export assays

    PMID:34956312

    Open questions at the time
    • Identity of missing liver-stage factors unknown
    • Whether an alternative complex exists not established
  13. 2022 Medium

    An upstream chaperone role was defined: HSP101 also resides in the ER and binds PEXEL proteins irrespective of processing, escorting them to the PVM where an EXP2–PTEX150 subcomplex facilitates HSP101 docking.

    Evidence IF localization, Co-IP with model PEXEL proteins, transgenic lines in P. falciparum

    PMID:35192672

    Open questions at the time
    • Structural basis of ER PEXEL recognition unknown
    • How ER and vacuolar HSP101 pools relate not resolved
  14. 2022 Low

    A possible additional PTEX function in nutrient acquisition was explored; transient HSP101 knockdown reduced hemoglobin uptake.

    Evidence Conditional knockdown (DDDHA) and hemoglobin uptake assays in P. falciparum

    PMID:36238365

    Open questions at the time
    • Single knockdown with indirect readout and no mechanistic follow-up
    • Direct role of HSP101 versus secondary effects not distinguished
  15. 2023 Medium

    Vacuolar HSP101 abundance relative to demand was quantified; HSP101 is present in the vacuole in functional excess over the minimum required for export.

    Evidence DiCre-mediated ER sequestration (knockER) with comparison to translational knockdown and export assays in P. falciparum

    PMID:37552754

    Open questions at the time
    • Biological purpose of the functional excess unclear
    • Single lab, novel tool
  16. 2023 Medium

    Cargo features required to engage HSP101 were mapped; the spacer between the PEXEL motif and the folded domain must be adequate in length/composition, and the P2' PEXEL residue has a dual role in plasmepsin V cleavage and HSP101-dependent export.

    Evidence Transgenic reporter export assays with PEXEL mutants and conditional knockdown in P. falciparum

    PMID:37926971

    Open questions at the time
    • Direct binding of the spacer to HSP101 pore loops not shown
    • Generalizability across native cargo untested

Open questions

Synthesis pass · forward-looking unresolved questions
  • How ATP hydrolysis is kinetically coupled to the threading cycle, how HSP101 selects and hands off cargo from ER to PVM, and the identity of the alternative unfolding route for transmembrane cargo remain unresolved.
  • No time-resolved biochemical measurement of ATP-coupled translocation
  • Unidentified TM-cargo unfolding pathway
  • Mechanistic basis of vacuolar functional excess unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
EXP2PEXEL-MOTIF EXPORTED PROTEINS (CARGO, RECOGNIZED IN THE ER)PTEX150PTEX88 (CLOSEST INTERACTION PARTNER WITHIN PTEX)
Complex memberships
>1230 kDa macromolecular PTEX assembly at the PVMHSP101 spiral AAA+ hexamer tethered above the EXP2-PTEX150 funnelPTEX (Plasmodium translocon of exported proteins) core complex: HSP101 + PTEX150 + EXP2

Evidence

Reading pass · 19 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 HSP101 (PF3D7_1116800) was identified as a component of the Plasmodium translocon of exported proteins (PTEX) located in the parasitophorous vacuole membrane of P. falciparum. HSP101 is a ClpA/B-like AAA+ ATPase that forms part of an ATP-powered complex together with PTEX150 and EXP2, implicated in protein export across the vacuolar membrane. Co-immunoprecipitation, mass spectrometry, immunofluorescence, immunoelectron microscopy Nature High 19536257
2012 HSP101 is synthesized during the schizont stage and, prior to invasion, resides within the dense granules of invasive merozoites. After invasion, HSP101 is released into the parasitophorous vacuole membrane where it assembles as part of a stable macromolecular complex of >1230 kDa, with little turnover for most of the erythrocytic cycle. Biochemical fractionation supports an EXP2–PTEX150–HSP101 arrangement within the complex. Immunofluorescence, subcellular fractionation, blue native PAGE, immunoelectron microscopy The Journal of biological chemistry High 22253438
2013 Repeated attempts to delete HSP101 in P. berghei failed, indicating that HSP101 is essential for blood-stage parasite development. This genetic essentiality is consistent with an obligatory role in protein export. Reverse genetics (attempted gene deletion in P. berghei) Molecular microbiology Medium 23869529 24076174
2014 Conditional knockdown of HSP101 in P. falciparum caused a nearly complete block in export of all classes of exported proteins (PEXEL and PEXEL-negative), with substrates accumulating in the vacuole in both asexual and sexual parasites. Under export-blocked conditions, association between HSP101 and other PTEX components was lost, indicating complex integrity is required for efficient export. Chaperone auto-inhibition (dominant-negative strategy), immunofluorescence, protein export assays, co-immunoprecipitation Nature High 25043010
2014 Conditional knockdown of HSP101 (or PTEX150) greatly reduced trafficking of all classes of exported proteins across the double-membrane barrier in P. falciparum, including PEXEL proteins, PNEPs, and the virulence factor PfEMP1. Even modest knockdown strongly impaired blood-stage growth in vitro and in vivo. Inducible knockdown (conditional mutagenesis), flow cytometry, immunofluorescence, in vitro and in vivo growth assays Nature High 25043043
2014 HSP101 (PF3D7_1116800) was identified as a substrate of P. falciparum signal peptide peptidase (PfSPP) using a transfection-based in vivo luminescence assay, establishing intramembrane proteolytic cleavage of HSP101 by PfSPP at the endoplasmic reticulum. Transfection-based in vivo luminescence assay, bioinformatics substrate screen Biochemical and biophysical research communications Low 25017910
2015 Live cell imaging of endogenously fluorescence-tagged HSP101 in P. berghei revealed that HSP101 localizes to motile tubular extensions of the parasitophorous vacuole that protrude from the parasite into the red blood cell, most prominently during trophozoite growth. Distinct spatiotemporal expression during sporogony and liver-stage development indicates additional functions across the life cycle. Live cell fluorescence microscopy, correlative light and electron microscopy (CLEM), endogenous fluorescent tagging Scientific reports Medium 26219962
2015 HSP101 could not be detected during early liver stages of P. berghei infection, suggesting that the absence of HSP101 (the putative molecular motor of PTEX) may explain the lack of direct protein translocation of PEXEL-bearing reporters into the hepatocyte cytosol during liver-stage infection. Immunofluorescence, transgenic reporter export assays in liver stage Cellular microbiology Medium 26347246
2018 Cryo-electron microscopy of the endogenous PTEX core complex from P. falciparum at near-atomic resolution revealed that HSP101 forms a spiral-shaped AAA+ hexamer tethered above the EXP2-PTEX150 funnel-shaped channel. In the 'resetting' state, HSP101 undergoes pronounced compaction allowing three of six tyrosine-bearing pore loops lining the HSP101 channel to dissociate from cargo, resetting the translocon for the next threading cycle. Structures were captured in 'engaged' and 'resetting' states of cargo translocation using CRISPR-Cas9-inserted epitope tags. Cryo-electron microscopy (near-atomic resolution), CRISPR-Cas9 epitope tagging, endogenous complex isolation Nature High 30150771
2018 Inactivation of HSP101 (the AAA+ ATPase component of PTEX) arrests protein export across the parasitophorous vacuolar membrane, establishing HSP101 as required for the protein-conducting function of EXP2 but not for EXP2's independent nutrient channel activity. Regulated gene expression, functional protein export assays, cell-attached patch-clamp Nature microbiology High 30150733
2018 When export cargo is blocked from unfolding, loop-like extensions appear at the parasitophorous vacuole membrane containing trapped cargo and EXP2 but not HSP101 or PTEX150, indicating that HSP101 and PTEX150 remain in the main PTEX-containing export zones while EXP2 can be spatially segregated with stalled cargo. Fluorescence microscopy with inducible folding reporters (mouse DHFR domains), immunofluorescence Traffic (Copenhagen, Denmark) Medium 29696751
2018 Proteomic analysis showed that PTEX88 interacts most closely with HSP101 within the PTEX complex, with weaker affinity for other core PTEX constituents (EXP2, PTEX150), establishing HSP101 as the primary interaction partner of PTEX88 within the translocon. Immunoprecipitation, quantitative mass spectrometry (interactome/proteomics) The FEBS journal Medium 29637707
2019 Transgenic P. falciparum parasites were generated in which the unfoldase and threading/translocation functions of HSP101 were uncoupled. These parasites could export native proteins but were unable to translocate tightly folded soluble PEXEL-bearing reporter proteins across the PVM. In contrast, an identical reporter with a transmembrane domain could be exported, demonstrating that (1) HSP101 serves as the unfoldase for soluble cargo requiring translocation, and (2) proteins with transmembrane domains use an alternative unfolding pathway prior to PTEX. Transgenic parasite generation (uncoupled unfoldase mutants), reporter export assays, immunofluorescence mBio High 31164473
2020 Although EXP1 knockdown caused profound vacuole ultrastructure defects and altered EXP2 distribution in the PVM, the distribution of the HSP101 unfoldase was not substantially altered, indicating that EXP1 is specifically required for organizing EXP2 but not HSP101 within the vacuole membrane. Conditional knockdown (TetR-DOZI-aptamers), immunofluorescence, electron microscopy, BioID proximity labeling Cellular microbiology Medium 31990132
2021 Transgenic P. berghei parasites restored with liver-stage HSP101 expression (via ptex150 or ef1α promoter) completed the life cycle but failed to export PEXEL-proteins in early liver stages, demonstrating that HSP101 alone is insufficient to reconstitute PTEX-dependent export in early liver stages, implicating additional missing PTEX components or alternative liver-stage export complexes. Transgenic parasite generation (promoter swap, additional gene copy), PEXEL reporter export assays in liver stage Frontiers in genetics Medium 34956312
2022 HSP101 localizes both within the parasitophorous vacuole and within the parasite's ER throughout ring and trophozoite stages. HSP101 forms specific interactions with model PEXEL proteins in the ER irrespective of their PEXEL processing status, suggesting that HSP101 functions as a chaperone that recognizes and escorts PEXEL proteins from the ER to the parasitophorous vacuole. Additionally, EXP2 and PTEX150 form a stable subcomplex that facilitates HSP101 docking at the PVM. Immunofluorescence (localization), co-immunoprecipitation (protein interactions), transgenic parasite lines PLoS pathogens Medium 35192672
2022 Transient knockdown of HSP101 (in HSP101-DDDHA parasites) decreased hemoglobin uptake inside P. falciparum parasites, suggesting a role for the HSP101-containing PTEX complex at the parasitophorous vacuole membrane in hemoglobin uptake. Conditional knockdown (DDDHA destabilization domain), hemoglobin uptake assays FASEB bioAdvances Low 36238365
2023 Using the knockER system (DiCre-mediated ER sequestration via inducible KDEL fusion), vacuolar levels of HSP101 were shown to be maintained in excess of what is required to sustain effector protein export into the erythrocyte. Vacuole depletion of HSP101 hypersensitized parasites to a destabilization tag that inhibits HSP101-PTEX complex formation, but not to translational knockdown of the entire HSP101 pool, demonstrating compartment-specific functional excess of HSP101. DiCre-mediated knock-sideways (knockER), conditional ER retrieval, protein export assays Proceedings of the National Academy of Sciences of the United States of America Medium 37552754
2023 The downstream 'spacer' region separating the PEXEL motif from the folded functional domain of an exported protein must be of sufficient length and permissive amino acid composition to engage the HSP101 unfoldase component of PTEX for efficient translocation into the red blood cell. The conserved P2' E/Q/D residue of the PEXEL motif also has a dual role: first for plasmepsin V cleavage in the ER, and second for efficient PTEX-mediated (HSP101-dependent) export across the PVM. Transgenic reporter export assays, PEXEL mutant analysis, conditional knockdown Traffic (Copenhagen, Denmark) Medium 37926971

Source papers

Stage 0 corpus · 30 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2009 A newly discovered protein export machine in malaria parasites. Nature 381 19536257
2014 PTEX is an essential nexus for protein export in malaria parasites. Nature 207 25043043
2014 PTEX component HSP101 mediates export of diverse malaria effectors into host erythrocytes. Nature 205 25043010
2018 Malaria parasite translocon structure and mechanism of effector export. Nature 159 30150771
2016 Plasmodium species: master renovators of their host cells. Nature reviews. Microbiology 137 27374802
2012 Biosynthesis, localization, and macromolecular arrangement of the Plasmodium falciparum translocon of exported proteins (PTEX). The Journal of biological chemistry 120 22253438
2018 EXP2 is a nutrient-permeable channel in the vacuolar membrane of Plasmodium and is essential for protein export via PTEX. Nature microbiology 92 30150733
2013 The Plasmodium translocon of exported proteins (PTEX) component thioredoxin-2 is important for maintaining normal blood-stage growth. Molecular microbiology 72 23869529
2010 The Clp chaperones and proteases of the human malaria parasite Plasmodium falciparum. Journal of molecular biology 71 20887733
2013 Two putative protein export regulators promote Plasmodium blood stage development in vivo. Molecular and biochemical parasitology 66 24076174
2020 EXP1 is required for organisation of EXP2 in the intraerythrocytic malaria parasite vacuole. Cellular microbiology 47 31990132
2015 The Plasmodium berghei translocon of exported proteins reveals spatiotemporal dynamics of tubular extensions. Scientific reports 39 26219962
2012 An exported heat shock protein 40 associates with pathogenesis-related knobs in Plasmodium falciparum infected erythrocytes. PloS one 38 22970262
2015 The Plasmodium translocon of exported proteins component EXP2 is critical for establishing a patent malaria infection in mice. Cellular microbiology 36 26347246
2019 Uncoupling the Threading and Unfoldase Actions of Plasmodium HSP101 Reveals Differences in Export between Soluble and Insoluble Proteins. mBio 29 31164473
2018 Spatial organization of protein export in malaria parasite blood stages. Traffic (Copenhagen, Denmark) 29 29696751
2019 Deletion of Plasmodium falciparum Protein RON3 Affects the Functional Translocation of Exported Proteins and Glucose Uptake. mBio 25 31289187
2016 Expression and characterization of the Plasmodium translocon of the exported proteins component EXP2. Biochemical and biophysical research communications 23 27865834
2022 A revised mechanism for how Plasmodium falciparum recruits and exports proteins into its erythrocytic host cell. PLoS pathogens 19 35192672
2014 Crystal structure and solution characterization of the thioredoxin-2 from Plasmodium falciparum, a constituent of an essential parasitic protein export complex. Biochemical and biophysical research communications 15 25475729
2019 The N-terminus of EXP2 forms the membrane-associated pore of the protein exporting translocon PTEX in Plasmodium falciparum. Journal of biochemistry 14 30476118
2018 The malaria PTEX component PTEX88 interacts most closely with HSP101 at the host-parasite interface. The FEBS journal 13 29637707
2022 Heme Detoxification Protein (PfHDP) is essential for the hemoglobin uptake and metabolism in Plasmodium falciparum. FASEB bioAdvances 10 36238365
2022 The PTEX Pore Component EXP2 Is Important for Intrahepatic Development during the Plasmodium Liver Stage. mBio 10 36445080
2020 PV1 Protein from Plasmodium falciparum Exhibits Chaperone-Like Functions and Cooperates with Hsp100s. International journal of molecular sciences 10 33207549
2023 Knock-sideways by inducible ER retrieval enables a unique approach for studying Plasmodium-secreted proteins. Proceedings of the National Academy of Sciences of the United States of America 9 37552754
2021 Plasmodium falciparum SURFIN4.1 forms an intermediate complex with PTEX components and Pf113 during export to the red blood cell. Parasitology international 9 33901679
2014 Plasmodium falciparum signal peptide peptidase cleaves malaria heat shock protein 101 (HSP101). Implications for gametocytogenesis. Biochemical and biophysical research communications 8 25017910
2023 Sequence elements within the PEXEL motif and its downstream region modulate PTEX-dependent protein export in Plasmodium falciparum. Traffic (Copenhagen, Denmark) 6 37926971
2021 Absence of PEXEL-Dependent Protein Export in Plasmodium Liver Stages Cannot Be Restored by Gain of the HSP101 Protein Translocon ATPase. Frontiers in genetics 6 34956312