{"gene":"IST1","run_date":"2026-06-10T01:55:23","timeline":{"discoveries":[{"year":2007,"finding":"Yeast Ist1 has a dual role in regulating Vps4: it localizes to the ESCRT machinery via Did2 where it positively recruits Vps4, and it also negatively regulates Vps4 by forming an Ist1-Vps4 heterodimer in which Vps4 cannot bind the ESCRT machinery.","method":"Genetic and biochemical analysis in S. cerevisiae, including co-immunoprecipitation and mutant analysis","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal binding assays and genetic analysis in yeast, replicated by independent lab (PMID:18032584) in the same year","pmids":["18032582"],"is_preprint":false},{"year":2007,"finding":"Yeast Ist1 forms a specific physical complex with Did2, and both Ist1-Did2 and Vta1-Vps60 compose two independent functional units that modulate late steps in MVB sorting; Ist1 endosomal recruitment depends on ESCRT-III.","method":"Synthetic genetic analysis (double mutants), co-immunoprecipitation, endosomal localization assays in S. cerevisiae","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — epistasis, physical interaction, and localization data in yeast; replicated by independent lab (PMID:18032582)","pmids":["18032584"],"is_preprint":false},{"year":2009,"finding":"Human IST1 is required for efficient cytokinetic abscission in HeLa cells; IST1 contains two distinct MIT-interacting motifs (MIM1 and MIM2) at its C-terminus that bind different grooves of the VPS4 MIT domain; IST1 and CHMP1 co-recruit VPS4 to the midbody, and depletion of either blocks VPS4 recruitment and abscission. IST1 depletion does not inhibit HIV-1 budding.","method":"RNAi knockdown with cytokinesis phenotype readout, NMR spectroscopy, mutagenesis, midbody localization by immunofluorescence, viral budding assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — NMR structure plus mutagenesis plus cellular functional assays (abscission, localization) in a single rigorous study","pmids":["19129479"],"is_preprint":false},{"year":2009,"finding":"The crystal structure of the Ist1 N-terminal domain reveals an ESCRT-III subunit-like fold, identifying Ist1 as a divergent ESCRT-III family member; Ist1NTD specifically binds the Did2 C-terminal MIM1 via a novel MIM-binding structural motif, revealing a mechanism for intermolecular ESCRT-III subunit association.","method":"X-ray crystallography of Ist1NTD alone and co-crystallized with Did2 fragment; binding assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with co-crystal of complex, providing direct structural mechanism","pmids":["19477918"],"is_preprint":false},{"year":2010,"finding":"The SPG20 protein spartin is recruited to the midbody through its MIT domain binding to IST1 (but not other CHMP proteins); Ist1 depletion significantly reduces spartin at midbodies; a structure-based mutation (F24D) in spartin MIT domain blocks spartin-IST1 interaction and prevents midbody localization, acting as dominant-negative to impair cytokinesis.","method":"Yeast two-hybrid, surface plasmon resonance, siRNA knockdown, immunofluorescence co-localization, dominant-negative rescue experiments","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — SPR binding assay, siRNA epistasis, structure-based mutagenesis with functional rescue, multiple orthogonal methods","pmids":["20719964"],"is_preprint":false},{"year":2010,"finding":"Human IST1 interacts with the tandem MIT domains of calpain 7 via both MIM1 and MIM2, and the IST1 MIM (GST-MIM fusion) enhances autolytic activity of purified calpain 7 in vitro; autolysis requires the catalytic Cys290 and is abolished by N-ethylmaleimide.","method":"GST pulldown, co-immunoprecipitation with deletion/point mutants, in vitro autolysis assay with purified proteins, catalytic-dead mutant (C290S)","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — in vitro reconstitution of calpain-7 activation by IST1, mutagenesis confirming catalytic requirement; single lab","pmids":["20849418"],"is_preprint":false},{"year":2011,"finding":"Calpain-7 binds CHMP1B at its second α-helical region (not the canonical MIM1 region), and forms a ternary complex with IST1; coexpression of CHMP1B and IST1 enhances calpain-7 autolysis in cells; ternary complex formation increases calpain-7 recruitment to membrane/organelle fractions.","method":"Co-immunoprecipitation with deletion mutants, in vitro pulldown, cell-based autolysis assay (HEK293T), subcellular fractionation","journal":"Journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with mutants plus fractionation plus functional autolysis assay; single lab","pmids":["21616915"],"is_preprint":false},{"year":2013,"finding":"Mammalian IST1 possesses a distinctive Met-Pro repeat sequence that is essential for Ca2+-dependent interaction with the EF-hand Ca2+-binding protein ALG-2; this interaction is enhanced by co-expression with CHMP1 proteins; IST1 binds ALG-2 by a different mode than other known ALG-2-interacting proteins.","method":"Far-Western blotting with biotinylated ALG-2, pulldown assays with deletion mutants of IST1 and GST-ALG-2 mutants","journal":"Bioscience, biotechnology, and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Far-Western plus pulldown with mutagenesis; single lab, two orthogonal binding methods","pmids":["23649269"],"is_preprint":false},{"year":2015,"finding":"Crystal structures of IST1 MIM complexed with MIT domains of VPS4, LIP5, and Spartin reveal two distinct binding mechanisms (MIM1 mode vs. MIM3 mode); two phenylalanine residues in IST1 MIM discriminate MIM1 vs. MIM3 binding; structural features in both MIT and MIM determine specificity.","method":"X-ray crystallography of three binary complexes, mutagenesis validating key residues","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple crystal structures with mutagenesis validation in a single comprehensive study","pmids":["25657007"],"is_preprint":false},{"year":2015,"finding":"Ist1 inhibition of Vps4 ATPase activity involves both the MIM and a conserved ELYC surface; an open conformation of the Ist1 core together with MIM interaction stimulates Vps4; binding of Did2 converts Ist1 from a Vps4 inhibitor to a stimulator, and this shift corresponds to altered ESCRT-III disassembly in vitro.","method":"ATPase activity assays, in vitro ESCRT-III disassembly assay, mutagenesis of Ist1 conformational elements","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstituted ATPase and disassembly assays with mutagenesis, multiple orthogonal methods","pmids":["26515066"],"is_preprint":false},{"year":2019,"finding":"IST1 facilitates association of CHMP2B and CHMP4B/SNF7-2 to form the ESCRT-III complex required for autophagosome-lysosome fusion; lack of IST1 impedes ESCRT-III complex formation and blocks autophagosome-lysosome fusion; MAPT/tau accumulation suppresses IST1 transcription via the ANP32A-INHAT pathway.","method":"Co-immunoprecipitation, AAV-mediated overexpression/knockdown in transgenic mice, autophagy flux assays (LC3-II, p62, autophagosome imaging)","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP for complex formation, in vivo knockdown/overexpression with defined autophagy phenotype; single lab","pmids":["31223056"],"is_preprint":false},{"year":2022,"finding":"In yeast, Ist1 is ubiquitinated, and this ubiquitination is required for proper endosomal recruitment of Ist1 and for recycling of nutrient transporters from endosomes back to the plasma membrane; the AAA-ATPase Cdc48 and its adaptor Npl4 are required for recycling, potentially through regulation of ubiquitinated Ist1.","method":"Ubiquitination assays, genetic mutant analysis, fluorescence microscopy of cargo recycling in S. cerevisiae","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis plus ubiquitination characterization plus cargo trafficking readout; single lab","pmids":["36125415"],"is_preprint":false},{"year":2023,"finding":"Human IST1, together with its binding partner CHMP1B, contributes to scission of early endosomal carriers; depleting IST1 impairs transferrin receptor delivery from early/sorting endosomes to the endocytic recycling compartment and impairs mannose-6-phosphate receptor export; IST1 interacts with the MIT domain-containing sorting nexin SNX15 on endosomes; SNX15 and CHMP1B alternately recruit IST1 to a clathrin-containing subdomain or the base of endosomal tubules.","method":"siRNA depletion, live-cell microscopy, kinetic and spatial cargo tracking, co-immunoprecipitation with SNX15","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — siRNA KD with defined cargo phenotypes and co-IP identification of SNX15 as binding partner; single lab, two orthogonal methods","pmids":["37926552"],"is_preprint":false},{"year":2023,"finding":"CAPN7 (Calpain-7) tandem MIT domains bind simultaneously to two distinct MIM motifs on IST1; structure-guided point mutations in either CAPN7 MIT domain disrupt IST1 binding in vitro and in cells; the CAPN7-IST1 interaction is required for CAPN7 recruitment to midbodies, efficient cytokinetic abscission, and NoCut checkpoint arrest; CAPN7 proteolytic activity is also required for abscission and checkpoint maintenance.","method":"X-ray crystallography of CAPN7 MIT-IST1 MIM complexes, mutagenesis, co-immunoprecipitation, siRNA depletion/rescue experiments, abscission and checkpoint assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus mutagenesis plus cellular epistasis (depletion/rescue) with multiple functional readouts in one rigorous study","pmids":["37772788"],"is_preprint":false},{"year":2024,"finding":"A pseudonatural product compound specifically disrupts the IST1-CHMP1B interaction, inhibiting IST1-CHMP1B copolymer formation required for normal-topology membrane scission; this inhibition rapidly blocks transferrin receptor recycling, causing accumulation in stalled sorting endosomes; stalled endosomes become decorated by lipidated LC3, linking noncanonical LC3 lipidation to IST1-CHMP1B complex disruption. The compound has no impact on cytokinesis, MVB sorting, or extracellular vesicle biogenesis.","method":"Chemical inhibitor treatment, transferrin recycling assay, LC3 lipidation assay, live-cell imaging, biogenesis assays for MVBs and extracellular vesicles","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — selective chemical tool with multiple functional readouts; single lab but orthogonal assays","pmids":["38635626"],"is_preprint":false},{"year":2025,"finding":"Endogenous IST1 exists in at least two distinct pools on endosomes (one transient, one relatively stable); upon growth factor stimulation, the stable pool becomes more mobile and the transient pool accumulates more rapidly; ESCRT-III dynamics are distinct from those of other ESCRT complexes, and an intrinsic amount of time is required for ESCRT-mediated ILV biogenesis.","method":"CRISPR tagging of endogenous Ist1, high-speed live-cell imaging, fluorescence microscopy","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — endogenous tagging with live imaging; single lab, single method but quantitative dynamics","pmids":["41060239"],"is_preprint":false},{"year":2025,"finding":"DeSUMOylated Spastin (Spastin-K427R) exhibits enhanced binding to IST1 compared to wild-type Spastin; co-overexpression of IST1 with Spastin enhances synaptic transmission and spine maturation; IST1 knockdown reduces GluA1 surface levels and abolishes Spastin's effects on AMPAR recycling, indicating IST1 is a key mediator of Spastin-dependent AMPAR endosomal recycling.","method":"Co-immunoprecipitation, siRNA knockdown, overexpression, immunofluorescence, electrophysiology (mEPSC recording)","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP plus siRNA rescue plus electrophysiology; single lab, multiple orthogonal methods","pmids":["41296224"],"is_preprint":false},{"year":2025,"finding":"In mammalian cytokinetic abscission, CHMP2A knockout causes minimal disruption to IST1 and CHMP2B localization at the abscission site, while CHMP4B, CHMP3, and CHMP1B show progressively severe organization defects, supporting a hierarchical ESCRT-III assembly model in which IST1 is among the least dependent on CHMP2A.","method":"CHMP2A knockout, live-cell imaging, structured illumination microscopy (SIM), correlative light-electron microscopy (CLEM)","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 2 / Weak — preprint, single lab; IST1-specific finding is a secondary observation within broader CHMP2A study","pmids":["bio_10.1101_2025.06.24.661003"],"is_preprint":true}],"current_model":"IST1 is a divergent ESCRT-III family member (ESCRT-III-like fold) that functions as a dual regulator of VPS4 ATPase activity—inhibiting VPS4 when bound alone (via its MIM and a conserved ELYC surface) but stimulating VPS4 when complexed with Did2/CHMP1—and is required at the midbody for cytokinetic abscission by recruiting VPS4, CAPN7 (whose proteolytic activity executes abscission and maintains the NoCut checkpoint), and spartin; IST1 also regulates endosomal membrane scission of recycling carriers together with CHMP1B, controls autophagosome-lysosome fusion via ESCRT-III complex assembly, and engages additional MIT-domain proteins (LIP5, SNX15, calpain-7) and the Ca2+-sensor ALG-2 through distinct MIM-binding mechanisms."},"narrative":{"mechanistic_narrative":"IST1 is a divergent ESCRT-III family member that functions as a bidirectional regulator of the VPS4 AAA-ATPase and an adaptor that recruits MIT-domain effectors to sites of ESCRT-III-mediated membrane remodeling [PMID:18032582, PMID:19477918]. Its N-terminal core adopts an ESCRT-III subunit-like fold, while its C-terminus presents two distinct MIT-interacting motifs (MIM1 and MIM2) that engage the MIT domains of partner proteins through structurally discriminable binding modes [PMID:19129479, PMID:19477918, PMID:25657007]. IST1 inhibits VPS4 ATPase activity when bound alone—through its MIM and a conserved ELYC surface—but binding of Did2/CHMP1 converts it into a VPS4 stimulator, coupling its conformational state to ESCRT-III disassembly [PMID:26515066]. At the midbody, IST1 and CHMP1 co-recruit VPS4 and are required for cytokinetic abscission, and IST1 additionally recruits the protease calpain-7 (CAPN7) and spartin to the abscission site, with CAPN7 proteolytic activity executing abscission and maintaining the NoCut checkpoint [PMID:19129479, PMID:20719964, PMID:37772788]. Beyond cytokinesis, IST1 partners with CHMP1B to drive normal-topology scission of endosomal recycling carriers, controlling transferrin and mannose-6-phosphate receptor trafficking, and is recruited to endosomal subdomains alternately by SNX15 and CHMP1B [PMID:37926552, PMID:38635626]. IST1 also promotes assembly of a CHMP2B/CHMP4B-containing ESCRT-III complex required for autophagosome-lysosome fusion [PMID:31223056], and engages the Ca2+-sensor ALG-2 via a Met-Pro repeat in a Ca2+-dependent manner [PMID:23649269].","teleology":[{"year":2007,"claim":"Established IST1 as a regulator of the VPS4 ATPase with opposing activities, answering how a single factor can both promote and restrain ESCRT machinery turnover.","evidence":"Genetic and co-immunoprecipitation analysis of Ist1 with Did2 and Vps4 in S. cerevisiae","pmids":["18032582","18032584"],"confidence":"High","gaps":["Structural basis of the dual regulation not yet defined","Mechanism distinguishing the recruitment versus inhibitory pools unclear"]},{"year":2009,"claim":"Defined IST1 as a divergent ESCRT-III subunit and demonstrated its functional role in human cytokinetic abscission, distinguishing it from ESCRT functions in viral budding.","evidence":"RNAi cytokinesis phenotyping, NMR of MIM1/MIM2-VPS4 MIT interaction, midbody immunofluorescence, and HIV-1 budding assay in HeLa cells; crystal structure of Ist1NTD with Did2","pmids":["19129479","19477918"],"confidence":"High","gaps":["How IST1-CHMP1 cooperatively recruit VPS4 mechanistically","Whether abscission requires VPS4 stimulation versus inhibition"]},{"year":2010,"claim":"Identified spartin and calpain-7 as IST1-specific MIT-domain effectors, expanding the abscission interactome and revealing IST1 can activate an associated protease.","evidence":"Yeast two-hybrid, SPR, structure-based mutagenesis with dominant-negative rescue for spartin; GST pulldown and in vitro autolysis assay with catalytic-dead mutant for calpain-7","pmids":["20719964","20849418"],"confidence":"High","gaps":["Physiological substrates of calpain-7 at the midbody not identified","Calpain-7 activation finding is single-lab in vitro"]},{"year":2013,"claim":"Showed IST1 engages the Ca2+-sensor ALG-2 through a distinctive Met-Pro repeat in a Ca2+-dependent, CHMP1-enhanced manner, linking ESCRT-III to calcium signaling.","evidence":"Far-Western blotting and pulldown with deletion mutants of IST1 and GST-ALG-2","pmids":["23649269"],"confidence":"Medium","gaps":["Cellular consequence of the IST1-ALG-2 interaction not established","Single-lab binding study without functional readout"]},{"year":2015,"claim":"Resolved the structural logic of IST1 MIM selectivity and the conformational switch governing VPS4, explaining how partner identity dictates IST1 binding mode and VPS4 outcome.","evidence":"Crystal structures of IST1 MIM with VPS4, LIP5, and Spartin MIT domains; ATPase and in vitro ESCRT-III disassembly assays with conformational mutants","pmids":["25657007","26515066"],"confidence":"High","gaps":["How the conformational switch is triggered in cells","Whether ELYC/MIM regulation operates at all IST1 sites of action"]},{"year":2019,"claim":"Extended IST1 function to autophagosome-lysosome fusion by demonstrating it nucleates a CHMP2B/CHMP4B ESCRT-III complex, with a transcriptional link to tau pathology.","evidence":"Co-IP, AAV-mediated knockdown/overexpression in transgenic mice, autophagy flux assays","pmids":["31223056"],"confidence":"Medium","gaps":["Direct membrane fusion mechanism not reconstituted","Single-lab study"]},{"year":2022,"claim":"Revealed that ubiquitination of IST1 controls its endosomal recruitment and cargo recycling, adding a post-translational layer to IST1 regulation.","evidence":"Ubiquitination assays, genetic analysis of Cdc48/Npl4, and cargo recycling microscopy in S. cerevisiae","pmids":["36125415"],"confidence":"Medium","gaps":["Ubiquitin ligase for IST1 not identified","Whether mammalian IST1 is similarly regulated unknown"]},{"year":2023,"claim":"Mapped CAPN7's tandem MIT engagement of both IST1 MIM motifs and proved this interaction plus CAPN7 catalytic activity are required for abscission and NoCut checkpoint, and defined IST1-CHMP1B in endosomal carrier scission with SNX15 as an alternate recruiter.","evidence":"Crystallography of CAPN7 MIT-IST1 MIM complexes with mutagenesis and depletion/rescue abscission/checkpoint assays; siRNA cargo tracking and SNX15 co-IP","pmids":["37772788","37926552"],"confidence":"High","gaps":["CAPN7 substrates executing abscission still unidentified","How SNX15 versus CHMP1B recruitment is switched in vivo"]},{"year":2024,"claim":"A selective chemical disruptor of the IST1-CHMP1B interface demonstrated that this copolymer is specifically required for endosomal recycling but dispensable for cytokinesis and MVB sorting, separating IST1's functional modes.","evidence":"Pseudonatural product inhibitor with transferrin recycling, LC3 lipidation, and MVB/EV biogenesis assays","pmids":["38635626"],"confidence":"Medium","gaps":["Mechanism linking stalled endosomes to noncanonical LC3 lipidation unresolved","Single-lab chemical-tool study"]},{"year":2025,"claim":"Endogenous imaging and effector studies defined distinct IST1 endosomal pools with growth-factor-responsive dynamics and established IST1 as the mediator of Spastin-dependent AMPAR recycling in neurons.","evidence":"CRISPR endogenous tagging with high-speed live imaging; co-IP, siRNA rescue, and mEPSC electrophysiology for the Spastin-IST1 axis","pmids":["41060239","41296224"],"confidence":"Medium","gaps":["Molecular determinants distinguishing the two endosomal pools unknown","Spastin-IST1 neuronal axis is single-lab"]},{"year":null,"claim":"How IST1's conformational/regulatory state, ubiquitination, and partner selection are coordinated to direct it among its distinct membrane-remodeling tasks (abscission, endosomal recycling, autophagy) in cells remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model for how IST1 is partitioned among its functional sites","Trigger of the inhibitor-to-stimulator switch in vivo unknown","Substrate repertoire of IST1-recruited CAPN7 undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,9]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[2,4,13]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[3,10]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[1,12,15]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[2,4]}],"pathway":[{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[2,13]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[12,14]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[10]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[15]}],"complexes":["ESCRT-III","IST1-CHMP1B copolymer"],"partners":["VPS4","CHMP1B","CAPN7","SPG20","ALG-2","LIP5","SNX15","SPAST"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P53990","full_name":"IST1 homolog","aliases":["Charged multivesicular body protein 8","CHMP8","Putative MAPK-activating protein PM28"],"length_aa":364,"mass_kda":39.8,"function":"ESCRT-III-like protein involved in cytokinesis, nuclear envelope reassembly and endosomal tubulation (PubMed:19129479, PubMed:26040712, PubMed:28242692). Is required for efficient abscission during cytokinesis (PubMed:19129479). Involved in recruiting VPS4A and/or VPS4B to the midbody of dividing cells (PubMed:19129479, PubMed:19129480). During late anaphase, involved in nuclear envelope reassembly and mitotic spindle disassembly together with the ESCRT-III complex: IST1 acts by mediating the recruitment of SPAST to the nuclear membrane, leading to microtubule severing (PubMed:26040712). Recruited to the reforming nuclear envelope (NE) during anaphase by LEMD2 (PubMed:28242692). Regulates early endosomal tubulation together with the ESCRT-III complex by mediating the recruitment of SPAST (PubMed:23897888)","subcellular_location":"Cytoplasmic vesicle; Cytoplasm, cytoskeleton, microtubule organizing center, centrosome; Midbody; Nucleus envelope","url":"https://www.uniprot.org/uniprotkb/P53990/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/IST1","classification":"Not Classified","n_dependent_lines":132,"n_total_lines":1208,"dependency_fraction":0.10927152317880795},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000182149","cell_line_id":"CID000781","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"vesicles","grade":3}],"interactors":[{"gene":"ARHGAP18","stoichiometry":0.2},{"gene":"CLTA","stoichiometry":0.2},{"gene":"CLTB","stoichiometry":0.2},{"gene":"HNRNPA2B1","stoichiometry":0.2},{"gene":"VPS9D1","stoichiometry":0.2},{"gene":"STAM","stoichiometry":0.2},{"gene":"HGS","stoichiometry":0.2},{"gene":"STAM2","stoichiometry":0.2},{"gene":"MVB12A","stoichiometry":0.2},{"gene":"NSDHL","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000781","total_profiled":1310},"omim":[{"mim_id":"621486","title":"MICROTUBULE-INTERACTING AND TRAFFICKING DOMAIN-CONTAINING PROTEIN 1; MITD1","url":"https://www.omim.org/entry/621486"},{"mim_id":"619273","title":"CIMDAG SYNDROME; CIMDAG","url":"https://www.omim.org/entry/619273"},{"mim_id":"616434","title":"IST1 FACTOR ASSOCIATED WITH ESCRT-III; IST1","url":"https://www.omim.org/entry/616434"},{"mim_id":"609983","title":"VACUOLAR PROTEIN SORTING 4 HOMOLOG B; VPS4B","url":"https://www.omim.org/entry/609983"},{"mim_id":"609982","title":"VACUOLAR PROTEIN SORTING 4 HOMOLOG A; VPS4A","url":"https://www.omim.org/entry/609982"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Vesicles","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/IST1"},"hgnc":{"alias_symbol":["CHMP8"],"prev_symbol":["KIAA0174"]},"alphafold":{"accession":"P53990","domains":[{"cath_id":"1.20.1260.60","chopping":"9-184","consensus_level":"high","plddt":94.5673,"start":9,"end":184}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P53990","model_url":"https://alphafold.ebi.ac.uk/files/AF-P53990-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P53990-F1-predicted_aligned_error_v6.png","plddt_mean":72.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=IST1","jax_strain_url":"https://www.jax.org/strain/search?query=IST1"},"sequence":{"accession":"P53990","fasta_url":"https://rest.uniprot.org/uniprotkb/P53990.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P53990/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P53990"}},"corpus_meta":[{"pmid":"31223056","id":"PMC_31223056","title":"MAPT/Tau accumulation represses autophagy flux by disrupting IST1-regulated ESCRT-III complex formation: a vicious cycle in Alzheimer neurodegeneration.","date":"2019","source":"Autophagy","url":"https://pubmed.ncbi.nlm.nih.gov/31223056","citation_count":163,"is_preprint":false},{"pmid":"18032582","id":"PMC_18032582","title":"Ist1 regulates Vps4 localization and assembly.","date":"2007","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/18032582","citation_count":116,"is_preprint":false},{"pmid":"19129479","id":"PMC_19129479","title":"Biochemical analyses of human IST1 and its function in cytokinesis.","date":"2009","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/19129479","citation_count":114,"is_preprint":false},{"pmid":"18032584","id":"PMC_18032584","title":"Novel Ist1-Did2 complex functions at a late step in multivesicular body sorting.","date":"2007","source":"Molecular biology of the 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physiology","url":"https://pubmed.ncbi.nlm.nih.gov/26983994","citation_count":60,"is_preprint":false},{"pmid":"9701564","id":"PMC_9701564","title":"Expression of Mel-CAM in implantation site intermediate trophoblastic cell line, IST-1, limits its migration on uterine smooth muscle cells.","date":"1998","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/9701564","citation_count":51,"is_preprint":false},{"pmid":"25657007","id":"PMC_25657007","title":"Distinct mechanisms of recognizing endosomal sorting complex required for transport III (ESCRT-III) protein IST1 by different microtubule interacting and trafficking (MIT) domains.","date":"2015","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/25657007","citation_count":34,"is_preprint":false},{"pmid":"20849418","id":"PMC_20849418","title":"Autolytic activity of human calpain 7 is enhanced by ESCRT-III-related protein IST1 through MIT-MIM interaction.","date":"2010","source":"The 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including co-immunoprecipitation and mutant analysis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal binding assays and genetic analysis in yeast, replicated by independent lab (PMID:18032584) in the same year\",\n      \"pmids\": [\"18032582\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Yeast Ist1 forms a specific physical complex with Did2, and both Ist1-Did2 and Vta1-Vps60 compose two independent functional units that modulate late steps in MVB sorting; Ist1 endosomal recruitment depends on ESCRT-III.\",\n      \"method\": \"Synthetic genetic analysis (double mutants), co-immunoprecipitation, endosomal localization assays in S. cerevisiae\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — epistasis, physical interaction, and localization data in yeast; replicated by independent lab (PMID:18032582)\",\n      \"pmids\": [\"18032584\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Human IST1 is required for efficient cytokinetic abscission in HeLa cells; IST1 contains two distinct MIT-interacting motifs (MIM1 and MIM2) at its C-terminus that bind different grooves of the VPS4 MIT domain; IST1 and CHMP1 co-recruit VPS4 to the midbody, and depletion of either blocks VPS4 recruitment and abscission. IST1 depletion does not inhibit HIV-1 budding.\",\n      \"method\": \"RNAi knockdown with cytokinesis phenotype readout, NMR spectroscopy, mutagenesis, midbody localization by immunofluorescence, viral budding assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — NMR structure plus mutagenesis plus cellular functional assays (abscission, localization) in a single rigorous study\",\n      \"pmids\": [\"19129479\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The crystal structure of the Ist1 N-terminal domain reveals an ESCRT-III subunit-like fold, identifying Ist1 as a divergent ESCRT-III family member; Ist1NTD specifically binds the Did2 C-terminal MIM1 via a novel MIM-binding structural motif, revealing a mechanism for intermolecular ESCRT-III subunit association.\",\n      \"method\": \"X-ray crystallography of Ist1NTD alone and co-crystallized with Did2 fragment; binding assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with co-crystal of complex, providing direct structural mechanism\",\n      \"pmids\": [\"19477918\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The SPG20 protein spartin is recruited to the midbody through its MIT domain binding to IST1 (but not other CHMP proteins); Ist1 depletion significantly reduces spartin at midbodies; a structure-based mutation (F24D) in spartin MIT domain blocks spartin-IST1 interaction and prevents midbody localization, acting as dominant-negative to impair cytokinesis.\",\n      \"method\": \"Yeast two-hybrid, surface plasmon resonance, siRNA knockdown, immunofluorescence co-localization, dominant-negative rescue experiments\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — SPR binding assay, siRNA epistasis, structure-based mutagenesis with functional rescue, multiple orthogonal methods\",\n      \"pmids\": [\"20719964\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Human IST1 interacts with the tandem MIT domains of calpain 7 via both MIM1 and MIM2, and the IST1 MIM (GST-MIM fusion) enhances autolytic activity of purified calpain 7 in vitro; autolysis requires the catalytic Cys290 and is abolished by N-ethylmaleimide.\",\n      \"method\": \"GST pulldown, co-immunoprecipitation with deletion/point mutants, in vitro autolysis assay with purified proteins, catalytic-dead mutant (C290S)\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — in vitro reconstitution of calpain-7 activation by IST1, mutagenesis confirming catalytic requirement; single lab\",\n      \"pmids\": [\"20849418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Calpain-7 binds CHMP1B at its second α-helical region (not the canonical MIM1 region), and forms a ternary complex with IST1; coexpression of CHMP1B and IST1 enhances calpain-7 autolysis in cells; ternary complex formation increases calpain-7 recruitment to membrane/organelle fractions.\",\n      \"method\": \"Co-immunoprecipitation with deletion mutants, in vitro pulldown, cell-based autolysis assay (HEK293T), subcellular fractionation\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with mutants plus fractionation plus functional autolysis assay; single lab\",\n      \"pmids\": [\"21616915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Mammalian IST1 possesses a distinctive Met-Pro repeat sequence that is essential for Ca2+-dependent interaction with the EF-hand Ca2+-binding protein ALG-2; this interaction is enhanced by co-expression with CHMP1 proteins; IST1 binds ALG-2 by a different mode than other known ALG-2-interacting proteins.\",\n      \"method\": \"Far-Western blotting with biotinylated ALG-2, pulldown assays with deletion mutants of IST1 and GST-ALG-2 mutants\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Far-Western plus pulldown with mutagenesis; single lab, two orthogonal binding methods\",\n      \"pmids\": [\"23649269\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Crystal structures of IST1 MIM complexed with MIT domains of VPS4, LIP5, and Spartin reveal two distinct binding mechanisms (MIM1 mode vs. MIM3 mode); two phenylalanine residues in IST1 MIM discriminate MIM1 vs. MIM3 binding; structural features in both MIT and MIM determine specificity.\",\n      \"method\": \"X-ray crystallography of three binary complexes, mutagenesis validating key residues\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple crystal structures with mutagenesis validation in a single comprehensive study\",\n      \"pmids\": [\"25657007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Ist1 inhibition of Vps4 ATPase activity involves both the MIM and a conserved ELYC surface; an open conformation of the Ist1 core together with MIM interaction stimulates Vps4; binding of Did2 converts Ist1 from a Vps4 inhibitor to a stimulator, and this shift corresponds to altered ESCRT-III disassembly in vitro.\",\n      \"method\": \"ATPase activity assays, in vitro ESCRT-III disassembly assay, mutagenesis of Ist1 conformational elements\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstituted ATPase and disassembly assays with mutagenesis, multiple orthogonal methods\",\n      \"pmids\": [\"26515066\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"IST1 facilitates association of CHMP2B and CHMP4B/SNF7-2 to form the ESCRT-III complex required for autophagosome-lysosome fusion; lack of IST1 impedes ESCRT-III complex formation and blocks autophagosome-lysosome fusion; MAPT/tau accumulation suppresses IST1 transcription via the ANP32A-INHAT pathway.\",\n      \"method\": \"Co-immunoprecipitation, AAV-mediated overexpression/knockdown in transgenic mice, autophagy flux assays (LC3-II, p62, autophagosome imaging)\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP for complex formation, in vivo knockdown/overexpression with defined autophagy phenotype; single lab\",\n      \"pmids\": [\"31223056\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In yeast, Ist1 is ubiquitinated, and this ubiquitination is required for proper endosomal recruitment of Ist1 and for recycling of nutrient transporters from endosomes back to the plasma membrane; the AAA-ATPase Cdc48 and its adaptor Npl4 are required for recycling, potentially through regulation of ubiquitinated Ist1.\",\n      \"method\": \"Ubiquitination assays, genetic mutant analysis, fluorescence microscopy of cargo recycling in S. cerevisiae\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis plus ubiquitination characterization plus cargo trafficking readout; single lab\",\n      \"pmids\": [\"36125415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Human IST1, together with its binding partner CHMP1B, contributes to scission of early endosomal carriers; depleting IST1 impairs transferrin receptor delivery from early/sorting endosomes to the endocytic recycling compartment and impairs mannose-6-phosphate receptor export; IST1 interacts with the MIT domain-containing sorting nexin SNX15 on endosomes; SNX15 and CHMP1B alternately recruit IST1 to a clathrin-containing subdomain or the base of endosomal tubules.\",\n      \"method\": \"siRNA depletion, live-cell microscopy, kinetic and spatial cargo tracking, co-immunoprecipitation with SNX15\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — siRNA KD with defined cargo phenotypes and co-IP identification of SNX15 as binding partner; single lab, two orthogonal methods\",\n      \"pmids\": [\"37926552\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CAPN7 (Calpain-7) tandem MIT domains bind simultaneously to two distinct MIM motifs on IST1; structure-guided point mutations in either CAPN7 MIT domain disrupt IST1 binding in vitro and in cells; the CAPN7-IST1 interaction is required for CAPN7 recruitment to midbodies, efficient cytokinetic abscission, and NoCut checkpoint arrest; CAPN7 proteolytic activity is also required for abscission and checkpoint maintenance.\",\n      \"method\": \"X-ray crystallography of CAPN7 MIT-IST1 MIM complexes, mutagenesis, co-immunoprecipitation, siRNA depletion/rescue experiments, abscission and checkpoint assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus mutagenesis plus cellular epistasis (depletion/rescue) with multiple functional readouts in one rigorous study\",\n      \"pmids\": [\"37772788\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"A pseudonatural product compound specifically disrupts the IST1-CHMP1B interaction, inhibiting IST1-CHMP1B copolymer formation required for normal-topology membrane scission; this inhibition rapidly blocks transferrin receptor recycling, causing accumulation in stalled sorting endosomes; stalled endosomes become decorated by lipidated LC3, linking noncanonical LC3 lipidation to IST1-CHMP1B complex disruption. The compound has no impact on cytokinesis, MVB sorting, or extracellular vesicle biogenesis.\",\n      \"method\": \"Chemical inhibitor treatment, transferrin recycling assay, LC3 lipidation assay, live-cell imaging, biogenesis assays for MVBs and extracellular vesicles\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — selective chemical tool with multiple functional readouts; single lab but orthogonal assays\",\n      \"pmids\": [\"38635626\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Endogenous IST1 exists in at least two distinct pools on endosomes (one transient, one relatively stable); upon growth factor stimulation, the stable pool becomes more mobile and the transient pool accumulates more rapidly; ESCRT-III dynamics are distinct from those of other ESCRT complexes, and an intrinsic amount of time is required for ESCRT-mediated ILV biogenesis.\",\n      \"method\": \"CRISPR tagging of endogenous Ist1, high-speed live-cell imaging, fluorescence microscopy\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — endogenous tagging with live imaging; single lab, single method but quantitative dynamics\",\n      \"pmids\": [\"41060239\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DeSUMOylated Spastin (Spastin-K427R) exhibits enhanced binding to IST1 compared to wild-type Spastin; co-overexpression of IST1 with Spastin enhances synaptic transmission and spine maturation; IST1 knockdown reduces GluA1 surface levels and abolishes Spastin's effects on AMPAR recycling, indicating IST1 is a key mediator of Spastin-dependent AMPAR endosomal recycling.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown, overexpression, immunofluorescence, electrophysiology (mEPSC recording)\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP plus siRNA rescue plus electrophysiology; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"41296224\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In mammalian cytokinetic abscission, CHMP2A knockout causes minimal disruption to IST1 and CHMP2B localization at the abscission site, while CHMP4B, CHMP3, and CHMP1B show progressively severe organization defects, supporting a hierarchical ESCRT-III assembly model in which IST1 is among the least dependent on CHMP2A.\",\n      \"method\": \"CHMP2A knockout, live-cell imaging, structured illumination microscopy (SIM), correlative light-electron microscopy (CLEM)\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 2 / Weak — preprint, single lab; IST1-specific finding is a secondary observation within broader CHMP2A study\",\n      \"pmids\": [\"bio_10.1101_2025.06.24.661003\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"IST1 is a divergent ESCRT-III family member (ESCRT-III-like fold) that functions as a dual regulator of VPS4 ATPase activity—inhibiting VPS4 when bound alone (via its MIM and a conserved ELYC surface) but stimulating VPS4 when complexed with Did2/CHMP1—and is required at the midbody for cytokinetic abscission by recruiting VPS4, CAPN7 (whose proteolytic activity executes abscission and maintains the NoCut checkpoint), and spartin; IST1 also regulates endosomal membrane scission of recycling carriers together with CHMP1B, controls autophagosome-lysosome fusion via ESCRT-III complex assembly, and engages additional MIT-domain proteins (LIP5, SNX15, calpain-7) and the Ca2+-sensor ALG-2 through distinct MIM-binding mechanisms.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"IST1 is a divergent ESCRT-III family member that functions as a bidirectional regulator of the VPS4 AAA-ATPase and an adaptor that recruits MIT-domain effectors to sites of ESCRT-III-mediated membrane remodeling [#0, #3]. Its N-terminal core adopts an ESCRT-III subunit-like fold, while its C-terminus presents two distinct MIT-interacting motifs (MIM1 and MIM2) that engage the MIT domains of partner proteins through structurally discriminable binding modes [#2, #3, #8]. IST1 inhibits VPS4 ATPase activity when bound alone—through its MIM and a conserved ELYC surface—but binding of Did2/CHMP1 converts it into a VPS4 stimulator, coupling its conformational state to ESCRT-III disassembly [#9]. At the midbody, IST1 and CHMP1 co-recruit VPS4 and are required for cytokinetic abscission, and IST1 additionally recruits the protease calpain-7 (CAPN7) and spartin to the abscission site, with CAPN7 proteolytic activity executing abscission and maintaining the NoCut checkpoint [#2, #4, #13]. Beyond cytokinesis, IST1 partners with CHMP1B to drive normal-topology scission of endosomal recycling carriers, controlling transferrin and mannose-6-phosphate receptor trafficking, and is recruited to endosomal subdomains alternately by SNX15 and CHMP1B [#12, #14]. IST1 also promotes assembly of a CHMP2B/CHMP4B-containing ESCRT-III complex required for autophagosome-lysosome fusion [#10], and engages the Ca2+-sensor ALG-2 via a Met-Pro repeat in a Ca2+-dependent manner [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established IST1 as a regulator of the VPS4 ATPase with opposing activities, answering how a single factor can both promote and restrain ESCRT machinery turnover.\",\n      \"evidence\": \"Genetic and co-immunoprecipitation analysis of Ist1 with Did2 and Vps4 in S. cerevisiae\",\n      \"pmids\": [\"18032582\", \"18032584\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the dual regulation not yet defined\", \"Mechanism distinguishing the recruitment versus inhibitory pools unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined IST1 as a divergent ESCRT-III subunit and demonstrated its functional role in human cytokinetic abscission, distinguishing it from ESCRT functions in viral budding.\",\n      \"evidence\": \"RNAi cytokinesis phenotyping, NMR of MIM1/MIM2-VPS4 MIT interaction, midbody immunofluorescence, and HIV-1 budding assay in HeLa cells; crystal structure of Ist1NTD with Did2\",\n      \"pmids\": [\"19129479\", \"19477918\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How IST1-CHMP1 cooperatively recruit VPS4 mechanistically\", \"Whether abscission requires VPS4 stimulation versus inhibition\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified spartin and calpain-7 as IST1-specific MIT-domain effectors, expanding the abscission interactome and revealing IST1 can activate an associated protease.\",\n      \"evidence\": \"Yeast two-hybrid, SPR, structure-based mutagenesis with dominant-negative rescue for spartin; GST pulldown and in vitro autolysis assay with catalytic-dead mutant for calpain-7\",\n      \"pmids\": [\"20719964\", \"20849418\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrates of calpain-7 at the midbody not identified\", \"Calpain-7 activation finding is single-lab in vitro\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed IST1 engages the Ca2+-sensor ALG-2 through a distinctive Met-Pro repeat in a Ca2+-dependent, CHMP1-enhanced manner, linking ESCRT-III to calcium signaling.\",\n      \"evidence\": \"Far-Western blotting and pulldown with deletion mutants of IST1 and GST-ALG-2\",\n      \"pmids\": [\"23649269\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cellular consequence of the IST1-ALG-2 interaction not established\", \"Single-lab binding study without functional readout\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Resolved the structural logic of IST1 MIM selectivity and the conformational switch governing VPS4, explaining how partner identity dictates IST1 binding mode and VPS4 outcome.\",\n      \"evidence\": \"Crystal structures of IST1 MIM with VPS4, LIP5, and Spartin MIT domains; ATPase and in vitro ESCRT-III disassembly assays with conformational mutants\",\n      \"pmids\": [\"25657007\", \"26515066\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the conformational switch is triggered in cells\", \"Whether ELYC/MIM regulation operates at all IST1 sites of action\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extended IST1 function to autophagosome-lysosome fusion by demonstrating it nucleates a CHMP2B/CHMP4B ESCRT-III complex, with a transcriptional link to tau pathology.\",\n      \"evidence\": \"Co-IP, AAV-mediated knockdown/overexpression in transgenic mice, autophagy flux assays\",\n      \"pmids\": [\"31223056\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct membrane fusion mechanism not reconstituted\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Revealed that ubiquitination of IST1 controls its endosomal recruitment and cargo recycling, adding a post-translational layer to IST1 regulation.\",\n      \"evidence\": \"Ubiquitination assays, genetic analysis of Cdc48/Npl4, and cargo recycling microscopy in S. cerevisiae\",\n      \"pmids\": [\"36125415\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitin ligase for IST1 not identified\", \"Whether mammalian IST1 is similarly regulated unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Mapped CAPN7's tandem MIT engagement of both IST1 MIM motifs and proved this interaction plus CAPN7 catalytic activity are required for abscission and NoCut checkpoint, and defined IST1-CHMP1B in endosomal carrier scission with SNX15 as an alternate recruiter.\",\n      \"evidence\": \"Crystallography of CAPN7 MIT-IST1 MIM complexes with mutagenesis and depletion/rescue abscission/checkpoint assays; siRNA cargo tracking and SNX15 co-IP\",\n      \"pmids\": [\"37772788\", \"37926552\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"CAPN7 substrates executing abscission still unidentified\", \"How SNX15 versus CHMP1B recruitment is switched in vivo\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"A selective chemical disruptor of the IST1-CHMP1B interface demonstrated that this copolymer is specifically required for endosomal recycling but dispensable for cytokinesis and MVB sorting, separating IST1's functional modes.\",\n      \"evidence\": \"Pseudonatural product inhibitor with transferrin recycling, LC3 lipidation, and MVB/EV biogenesis assays\",\n      \"pmids\": [\"38635626\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking stalled endosomes to noncanonical LC3 lipidation unresolved\", \"Single-lab chemical-tool study\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Endogenous imaging and effector studies defined distinct IST1 endosomal pools with growth-factor-responsive dynamics and established IST1 as the mediator of Spastin-dependent AMPAR recycling in neurons.\",\n      \"evidence\": \"CRISPR endogenous tagging with high-speed live imaging; co-IP, siRNA rescue, and mEPSC electrophysiology for the Spastin-IST1 axis\",\n      \"pmids\": [\"41060239\", \"41296224\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular determinants distinguishing the two endosomal pools unknown\", \"Spastin-IST1 neuronal axis is single-lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How IST1's conformational/regulatory state, ubiquitination, and partner selection are coordinated to direct it among its distinct membrane-remodeling tasks (abscission, endosomal recycling, autophagy) in cells remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model for how IST1 is partitioned among its functional sites\", \"Trigger of the inhibitor-to-stimulator switch in vivo unknown\", \"Substrate repertoire of IST1-recruited CAPN7 undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 9]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 4, 13]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [3, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [1, 12, 15]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [2, 13]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [12, 14]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"complexes\": [\n      \"ESCRT-III\",\n      \"IST1-CHMP1B copolymer\"\n    ],\n    \"partners\": [\n      \"VPS4\",\n      \"CHMP1B\",\n      \"CAPN7\",\n      \"SPG20\",\n      \"ALG-2\",\n      \"LIP5\",\n      \"SNX15\",\n      \"SPAST\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}