{"gene":"FHIP1A","run_date":"2026-04-28T17:46:03","timeline":{"discoveries":[{"year":2021,"finding":"FHIP1A is a component of the FTS-Hook-FHIP (FHF) cargo adaptor complex that links cytoplasmic dynein-1 to cargo. Proteomic interactome mapping of each FHIP protein revealed that FHIP1A-containing FHF complexes have a distinct protein interactome compared to FHIP1B- and FHIP2A-containing complexes, and associate with distinct motile cargos. FHIP1A-FHF complexes move with dynein and dynactin in single-molecule in vitro reconstitution assays, establishing FHIP1A as a dynein cargo adaptor.","method":"Affinity purification mass spectrometry (interactome mapping), live-cell imaging, single-molecule in vitro reconstitution assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including proteomics, live imaging, and in vitro reconstitution in a single study","pmids":["34882091"],"is_preprint":false},{"year":2020,"finding":"The FTS-Hook-FHIP (FHF) complex interacts with the heterotetrameric adaptor protein complex AP-4, with the interaction mediated by direct binding of the AP-4 μ4 subunit to coiled-coil domains in Hook1 and Hook2 subunits. Knockdown of FHF subunits (including FHIP proteins) results in dispersal of AP-4 and its cargo ATG9A from the perinuclear region, consistent with FHF coupling organelles to the dynein-dynactin retrograde motor on microtubules.","method":"Affinity purification-mass spectrometry, biochemical binding assays (direct binding), siRNA knockdown with fluorescence microscopy readout","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal biochemical validation and functional KD phenotype, but FHIP1A not individually distinguished from other FHIP subunits in this study","pmids":["32073997"],"is_preprint":false},{"year":2017,"finding":"FHIP1A (as part of the FTS-Hook-FHIP complex) was identified in the human cytoplasmic dynein-1 interactome by BioID proximity labeling attached to dynein and dynactin subunits, placing the FHF complex in spatial proximity to the dynein/dynactin machinery in living cells.","method":"Proximity-dependent biotinylation (BioID) coupled to mass spectrometry","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 — BioID in living cells provides spatial interaction data; single lab, single method","pmids":["28718761"],"is_preprint":false}],"current_model":"FHIP1A is a subunit of the FTS-Hook-FHIP (FHF) cargo adaptor complex that links cytoplasmic dynein-1/dynactin to specific intracellular cargos; different combinatorial assemblies of FHF complexes (distinguished by which FHIP protein is present) associate with distinct motile cargos, and the FHF complex also interacts with the AP-4 coat complex to mediate perinuclear distribution of AP-4 and its autophagy cargo ATG9A via dynein-driven retrograde transport."},"narrative":{"teleology":[{"year":2017,"claim":"Establishing the physical proximity of the FHF complex to the dynein-dynactin machinery in living cells placed FHIP1A within the dynein transport system, but its precise role was undefined.","evidence":"BioID proximity labeling on dynein and dynactin subunits in human cells, followed by mass spectrometry","pmids":["28718761"],"confidence":"Medium","gaps":["Proximity labeling does not distinguish direct from indirect interactions","No functional data on the consequence of FHIP1A loss","Identity of cargos linked specifically through FHIP1A unknown"]},{"year":2020,"claim":"Demonstrating that the FHF complex directly binds the AP-4 coat and that FHF knockdown disperses AP-4 and ATG9A from the perinuclear region established a functional role for the complex in dynein-driven retrograde positioning of AP-4-coated organelles.","evidence":"AP-MS, direct biochemical binding assays between AP-4 μ4 and Hook1/Hook2, siRNA knockdown with fluorescence microscopy in human cells","pmids":["32073997"],"confidence":"Medium","gaps":["FHIP1A was not individually distinguished from other FHIP paralogs in this study","Whether FHIP1A specifically mediates the AP-4 interaction or another FHIP paralog is the relevant subunit remains unresolved","Mechanism by which FHF activates dynein motility on AP-4 vesicles not determined"]},{"year":2021,"claim":"Systematic interactome mapping of individual FHIP proteins revealed that FHIP1A-containing FHF complexes engage a cargo repertoire distinct from FHIP1B- and FHIP2A-containing complexes, and in vitro reconstitution proved FHIP1A-FHF activates processive dynein-dynactin motility, establishing FHIP1A as a bona fide dynein cargo adaptor.","evidence":"AP-MS of each FHIP protein, live-cell imaging, and single-molecule in vitro motility assays in a single integrated study","pmids":["34882091"],"confidence":"High","gaps":["Specific cargo identities uniquely requiring FHIP1A in vivo remain incompletely cataloged","Structural basis for FHIP1A incorporation into the FHF complex and cargo selectivity is unknown","In vivo loss-of-function phenotype of FHIP1A alone (not other FHF subunits) not yet characterized"]},{"year":null,"claim":"Open questions include the identity of the specific vesicular cargos that require FHIP1A (as opposed to other FHIP paralogs) for dynein-mediated transport, the structural determinants that confer cargo selectivity on FHIP1A-FHF, and the physiological consequences of FHIP1A loss in organismal models.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of the FHIP1A-FHF complex exists","No genetic or animal model phenotype reported for FHIP1A loss","Regulation of FHIP1A incorporation into FHF complexes is unexplored"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[0,2]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[0,1]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[1]}],"complexes":["FTS-Hook-FHIP (FHF) complex"],"partners":["FTS","HOOK1","HOOK2","DCTN1","DYNC1H1","AP4M1"],"other_free_text":[]},"mechanistic_narrative":"FHIP1A is a subunit of the FTS-Hook-FHIP (FHF) cargo adaptor complex that links cytoplasmic dynein-1 and dynactin to specific intracellular cargos for retrograde microtubule-based transport [PMID:34882091]. Proteomic interactome mapping demonstrates that FHIP1A-containing FHF complexes associate with a distinct set of motile cargos compared to complexes containing other FHIP paralogs, and single-molecule reconstitution confirms that FHIP1A-FHF complexes move processively with dynein-dynactin in vitro [PMID:34882091]. The FHF complex also physically interacts with the AP-4 adaptor protein coat, and knockdown of FHF subunits disperses AP-4 and its autophagy cargo ATG9A from the perinuclear region, indicating that FHF-dynein coupling maintains perinuclear organelle positioning [PMID:32073997]."},"prefetch_data":{"uniprot":{"accession":"Q05DH4","full_name":"FHF complex subunit HOOK-interacting protein 1A","aliases":["FTS- and Hook-interacting protein like","FHIP-L"],"length_aa":1040,"mass_kda":116.6,"function":"Probable component of the FTS/Hook/FHIP complex (FHF complex) (PubMed:32073997). FHF complex promotes the distribution of AP-4 complex to the perinuclear area of the cell (PubMed:32073997)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q05DH4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FHIP1A","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/FHIP1A","total_profiled":1310},"omim":[{"mim_id":"620230","title":"FHF COMPLEX SUBUNIT HOOK-INTERACTING PROTEIN 2B; FHIP2B","url":"https://www.omim.org/entry/620230"},{"mim_id":"620229","title":"FHF COMPLEX SUBUNIT HOOK-INTERACTING PROTEIN 1B; FHIP1B","url":"https://www.omim.org/entry/620229"},{"mim_id":"617312","title":"FHF COMPLEX SUBUNIT HOOK-INTERACTING PROTEIN 2A; FHIP2A","url":"https://www.omim.org/entry/617312"},{"mim_id":"607825","title":"HOOK MICROTUBULE TETHERING PROTEIN 3; HOOK3","url":"https://www.omim.org/entry/607825"},{"mim_id":"607824","title":"HOOK MICROTUBULE TETHERING PROTEIN 2; HOOK2","url":"https://www.omim.org/entry/607824"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"skeletal muscle","ntpm":32.3}],"url":"https://www.proteinatlas.org/search/FHIP1A"},"hgnc":{"alias_symbol":["FLJ43373","FHIP-L"],"prev_symbol":["FAM160A1"]},"alphafold":{"accession":"Q05DH4","domains":[{"cath_id":"-","chopping":"435-449_498-519_850-950_975-1038","consensus_level":"high","plddt":79.4362,"start":435,"end":1038}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q05DH4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q05DH4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q05DH4-F1-predicted_aligned_error_v6.png","plddt_mean":64.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FHIP1A","jax_strain_url":"https://www.jax.org/strain/search?query=FHIP1A"},"sequence":{"accession":"Q05DH4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q05DH4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q05DH4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q05DH4"}},"corpus_meta":[{"pmid":"35546142","id":"PMC_35546142","title":"Meta-analysis 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genes and pathways in familial lymphoid cancers using whole exome sequencing.","date":"2026","source":"Leukemia & lymphoma","url":"https://pubmed.ncbi.nlm.nih.gov/41652927","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"12477932","id":"PMC_12477932","title":"Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12477932","citation_count":1479,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"26186194","id":"PMC_26186194","title":"The BioPlex Network: A Systematic Exploration of the Human Interactome.","date":"2015","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/26186194","citation_count":1118,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28514442","id":"PMC_28514442","title":"Architecture of the human interactome defines protein communities and disease networks.","date":"2017","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/28514442","citation_count":1085,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"29507755","id":"PMC_29507755","title":"VIRMA mediates preferential m6A mRNA methylation in 3'UTR and near stop codon and associates with alternative polyadenylation.","date":"2018","source":"Cell discovery","url":"https://pubmed.ncbi.nlm.nih.gov/29507755","citation_count":829,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"33961781","id":"PMC_33961781","title":"Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.","date":"2021","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/33961781","citation_count":705,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"29395067","id":"PMC_29395067","title":"High-Density Proximity Mapping Reveals the Subcellular Organization of mRNA-Associated Granules and Bodies.","date":"2018","source":"Molecular 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cell.","date":"2021","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/34079125","citation_count":339,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"10737800","id":"PMC_10737800","title":"Shotgun sequencing of the human transcriptome with ORF expressed sequence tags.","date":"2000","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/10737800","citation_count":135,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28718761","id":"PMC_28718761","title":"The human cytoplasmic dynein interactome reveals novel activators of motility.","date":"2017","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/28718761","citation_count":118,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"20379614","id":"PMC_20379614","title":"Personalized smoking cessation: interactions between nicotine dose, dependence and quit-success genotype score.","date":"2010","source":"Molecular medicine (Cambridge, Mass.)","url":"https://pubmed.ncbi.nlm.nih.gov/20379614","citation_count":108,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"35044719","id":"PMC_35044719","title":"Proteome-scale mapping of binding sites in the unstructured regions of the human proteome.","date":"2022","source":"Molecular systems biology","url":"https://pubmed.ncbi.nlm.nih.gov/35044719","citation_count":61,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"29467281","id":"PMC_29467281","title":"The MYO6 interactome reveals adaptor complexes coordinating early endosome and cytoskeletal dynamics.","date":"2018","source":"EMBO reports","url":"https://pubmed.ncbi.nlm.nih.gov/29467281","citation_count":44,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"34882091","id":"PMC_34882091","title":"Cytoplasmic dynein-1 cargo diversity is mediated by the combinatorial assembly of FTS-Hook-FHIP complexes.","date":"2021","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/34882091","citation_count":37,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"31527615","id":"PMC_31527615","title":"The RNA-mediated estrogen receptor α interactome of hormone-dependent human breast cancer cell nuclei.","date":"2019","source":"Scientific data","url":"https://pubmed.ncbi.nlm.nih.gov/31527615","citation_count":32,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32073997","id":"PMC_32073997","title":"The FTS-Hook-FHIP (FHF) complex interacts with AP-4 to mediate perinuclear distribution of AP-4 and its cargo ATG9A.","date":"2020","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/32073997","citation_count":27,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"37827155","id":"PMC_37827155","title":"Antagonistic roles of canonical and Alternative-RPA in disease-associated tandem CAG repeat instability.","date":"2023","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/37827155","citation_count":23,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"37689310","id":"PMC_37689310","title":"Pulse-SILAC and Interactomics Reveal Distinct DDB1-CUL4-Associated Factors, Cellular Functions, and Protein Substrates.","date":"2023","source":"Molecular & cellular proteomics : MCP","url":"https://pubmed.ncbi.nlm.nih.gov/37689310","citation_count":8,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"30420729","id":"PMC_30420729","title":"Whole exome sequencing identifies recessive germline mutations in FAM160A1 in familial NK/T cell lymphoma.","date":"2018","source":"Blood cancer journal","url":"https://pubmed.ncbi.nlm.nih.gov/30420729","citation_count":6,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":3879,"output_tokens":34,"usd":0.006073},"stage2":{"model":"","input_tokens":0,"output_tokens":0,"usd":0.0},"total_usd":0.128085,"stage1_batch_id":"msgbatch_0118RScg3WGaGkaZRtWZbtce","stage2_batch_id":"msgbatch_01Cpfzvtbj42aqp5oYZ5Te2s","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":12367,"output_tokens":2150,"usd":0.034675},"round2_rules_fired":"R1","round2_stage2":{"model":"claude-opus-4-6","input_tokens":4380,"output_tokens":1453,"usd":0.087337}},"stage1_raw":"```json\n{\n  \"discoveries\": [],\n  \"current_model\": \"No mechanistic findings in the available literature.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper before extracting discoveries.\n\n**Classification:**\n\n**Retrieved Papers (4):**\n1. PMID:35546142 — GWAS/meta-analysis associating GATB/FHIP1A region with LDL-C. Pure association study, no mechanistic findings. EXCLUDE from discovery extraction (but confirms gene identity).\n2. PMID:29930801 — EWAS for stroke susceptibility genes. No FHIP1A mechanism. EXCLUDE.\n3. PMID:41913828 — Case study with FAM160A1 variants. FAM160A1 = FHIP1A alias. Pure genetic association/clinical. No mechanism. EXCLUDE from discoveries.\n4. PMID:41652927 — Lymphoid cancers, FAM160A1 variants. Pure genetic association. EXCLUDE from discoveries.\n\n**Gene2pubmed Papers (20):**\n1. PMID:12477932 — MGC cDNA sequencing. No mechanism. EXCLUDE.\n2. PMID:26186194 — BioPlex network, FHIP1A may appear as interactor. Proteome-scale AP-MS. KEEP if FHIP1A interactions described.\n3. PMID:28514442 — BioPlex 2.0. Same as above. KEEP.\n4. PMID:29507755 — VIRMA/m6A methylation. No FHIP1A mechanism. EXCLUDE.\n5. PMID:33961781 — BioPlex 3.0. KEEP.\n6. PMID:29395067 — BioID mRNA granules. No specific FHIP1A mechanism. EXCLUDE.\n7. PMID:16344560 — Alternative promoters. No mechanism. EXCLUDE.\n8. PMID:8889549 — EST database. EXCLUDE.\n9. PMID:34079125 — BioID human cell map. KEEP (localization data).\n10. PMID:10737800 — EST sequencing. EXCLUDE.\n11. PMID:28718761 — Dynein interactome BioID. KEEP — FHIP1A is part of FHF complex context.\n12. PMID:20379614 — Smoking cessation genetics. EXCLUDE.\n13. PMID:35044719 — SLiM-binding domains proteome. EXCLUDE (no specific FHIP1A mechanism).\n14. PMID:29467281 — MYO6 interactome. EXCLUDE (no FHIP1A specific findings).\n15. PMID:34882091 — FTS-Hook-FHIP complexes. **KEEP** — directly about FHIP proteins including FHIP1A/FHIP1B.\n16. PMID:31527615 — ERα interactome. EXCLUDE.\n17. PMID:32073997 — FHF complex with AP-4. **KEEP** — directly about FHF complex.\n18. PMID:37827155 — RPA/CAG repeats. EXCLUDE.\n19. PMID:37689310 — DDB1-CUL4 DCAFs. EXCLUDE (no FHIP1A specific findings).\n20. PMID:30420729 — FAM160A1 (=FHIP1A) germline mutations in NK/T cell lymphoma. Genetic association only. EXCLUDE from discoveries.\n\n**Key KEPT papers:** PMID:34882091, PMID:32073997, PMID:28718761, PMID:26186194, PMID:28514442, PMID:33961781, PMID:34079125.\n\nNow examining the mechanistic content:\n\n- PMID:34882091: Directly studies FHIP1A and FHIP1B. FHIP1B (not FHIP1A) interacts with Rab5. FHIP1A is characterized as part of FHF complex but with a different interactome. Need to extract what's specifically said about FHIP1A.\n- PMID:32073997: FHF complex (FTS-Hook-FHIP) interacts with AP-4 via Hook1/Hook2; knockdown of FHF subunits disperses AP-4 and ATG9A from perinuclear region. FHIP1A may be one of the FHIP proteins involved.\n- PMID:28718761: Dynein interactome; FHIP proteins identified as part of dynein machinery context.\n- BioPlex papers: FHIP1A appears as a node in interaction networks.\n\nFrom PMID:34882091, the abstract specifically discusses FHIP1A and FHIP1B as distinct proteins with different interactomes and cargo associations. FHIP1A's specific interactome is determined by proteomic approaches, and different FHF complexes associate with distinct motile cargos.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2021,\n      \"finding\": \"FHIP1A is a component of the FTS-Hook-FHIP (FHF) cargo adaptor complex that links cytoplasmic dynein-1 to cargo. Proteomic interactome mapping of each FHIP protein revealed that FHIP1A-containing FHF complexes have a distinct protein interactome compared to FHIP1B- and FHIP2A-containing complexes, and associate with distinct motile cargos. FHIP1A-FHF complexes move with dynein and dynactin in single-molecule in vitro reconstitution assays, establishing FHIP1A as a dynein cargo adaptor.\",\n      \"method\": \"Affinity purification mass spectrometry (interactome mapping), live-cell imaging, single-molecule in vitro reconstitution assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including proteomics, live imaging, and in vitro reconstitution in a single study\",\n      \"pmids\": [\"34882091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The FTS-Hook-FHIP (FHF) complex interacts with the heterotetrameric adaptor protein complex AP-4, with the interaction mediated by direct binding of the AP-4 μ4 subunit to coiled-coil domains in Hook1 and Hook2 subunits. Knockdown of FHF subunits (including FHIP proteins) results in dispersal of AP-4 and its cargo ATG9A from the perinuclear region, consistent with FHF coupling organelles to the dynein-dynactin retrograde motor on microtubules.\",\n      \"method\": \"Affinity purification-mass spectrometry, biochemical binding assays (direct binding), siRNA knockdown with fluorescence microscopy readout\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal biochemical validation and functional KD phenotype, but FHIP1A not individually distinguished from other FHIP subunits in this study\",\n      \"pmids\": [\"32073997\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FHIP1A (as part of the FTS-Hook-FHIP complex) was identified in the human cytoplasmic dynein-1 interactome by BioID proximity labeling attached to dynein and dynactin subunits, placing the FHF complex in spatial proximity to the dynein/dynactin machinery in living cells.\",\n      \"method\": \"Proximity-dependent biotinylation (BioID) coupled to mass spectrometry\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — BioID in living cells provides spatial interaction data; single lab, single method\",\n      \"pmids\": [\"28718761\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FHIP1A is a subunit of the FTS-Hook-FHIP (FHF) cargo adaptor complex that links cytoplasmic dynein-1/dynactin to specific intracellular cargos; different combinatorial assemblies of FHF complexes (distinguished by which FHIP protein is present) associate with distinct motile cargos, and the FHF complex also interacts with the AP-4 coat complex to mediate perinuclear distribution of AP-4 and its autophagy cargo ATG9A via dynein-driven retrograde transport.\"\n}\n```","stage2_raw":"\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"FHIP1A is a subunit of the FTS-Hook-FHIP (FHF) cargo adaptor complex that links cytoplasmic dynein-1 and dynactin to specific intracellular cargos for retrograde microtubule-based transport [PMID:34882091]. Proteomic interactome mapping demonstrates that FHIP1A-containing FHF complexes associate with a distinct set of motile cargos compared to complexes containing other FHIP paralogs, and single-molecule reconstitution confirms that FHIP1A-FHF complexes move processively with dynein-dynactin in vitro [PMID:34882091]. The FHF complex also physically interacts with the AP-4 adaptor protein coat, and knockdown of FHF subunits disperses AP-4 and its autophagy cargo ATG9A from the perinuclear region, indicating that FHF-dynein coupling maintains perinuclear organelle positioning [PMID:32073997].\",\n  \"teleology\": [\n    {\n      \"year\": 2017,\n      \"claim\": \"Establishing the physical proximity of the FHF complex to the dynein-dynactin machinery in living cells placed FHIP1A within the dynein transport system, but its precise role was undefined.\",\n      \"evidence\": \"BioID proximity labeling on dynein and dynactin subunits in human cells, followed by mass spectrometry\",\n      \"pmids\": [\"28718761\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Proximity labeling does not distinguish direct from indirect interactions\",\n        \"No functional data on the consequence of FHIP1A loss\",\n        \"Identity of cargos linked specifically through FHIP1A unknown\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrating that the FHF complex directly binds the AP-4 coat and that FHF knockdown disperses AP-4 and ATG9A from the perinuclear region established a functional role for the complex in dynein-driven retrograde positioning of AP-4-coated organelles.\",\n      \"evidence\": \"AP-MS, direct biochemical binding assays between AP-4 μ4 and Hook1/Hook2, siRNA knockdown with fluorescence microscopy in human cells\",\n      \"pmids\": [\"32073997\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"FHIP1A was not individually distinguished from other FHIP paralogs in this study\",\n        \"Whether FHIP1A specifically mediates the AP-4 interaction or another FHIP paralog is the relevant subunit remains unresolved\",\n        \"Mechanism by which FHF activates dynein motility on AP-4 vesicles not determined\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Systematic interactome mapping of individual FHIP proteins revealed that FHIP1A-containing FHF complexes engage a cargo repertoire distinct from FHIP1B- and FHIP2A-containing complexes, and in vitro reconstitution proved FHIP1A-FHF activates processive dynein-dynactin motility, establishing FHIP1A as a bona fide dynein cargo adaptor.\",\n      \"evidence\": \"AP-MS of each FHIP protein, live-cell imaging, and single-molecule in vitro motility assays in a single integrated study\",\n      \"pmids\": [\"34882091\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Specific cargo identities uniquely requiring FHIP1A in vivo remain incompletely cataloged\",\n        \"Structural basis for FHIP1A incorporation into the FHF complex and cargo selectivity is unknown\",\n        \"In vivo loss-of-function phenotype of FHIP1A alone (not other FHF subunits) not yet characterized\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Open questions include the identity of the specific vesicular cargos that require FHIP1A (as opposed to other FHIP paralogs) for dynein-mediated transport, the structural determinants that confer cargo selectivity on FHIP1A-FHF, and the physiological consequences of FHIP1A loss in organismal models.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No structural model of the FHIP1A-FHF complex exists\",\n        \"No genetic or animal model phenotype reported for FHIP1A loss\",\n        \"Regulation of FHIP1A incorporation into FHF complexes is unexplored\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [0, 2]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"complexes\": [\n      \"FTS-Hook-FHIP (FHF) complex\"\n    ],\n    \"partners\": [\n      \"FTS\",\n      \"HOOK1\",\n      \"HOOK2\",\n      \"DCTN1\",\n      \"DYNC1H1\",\n      \"AP4M1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}