{"gene":"WDR41","run_date":"2026-04-28T23:00:23","timeline":{"discoveries":[{"year":2016,"finding":"WDR41 forms a stable trimeric complex with C9ORF72 and SMCR8, and this complex acts as a GDP/GTP exchange factor (GEF) for RAB8a and RAB39b, thereby controlling autophagic flux.","method":"Co-immunoprecipitation, GEF activity assay, knockdown with autophagic flux readouts (p62/TDP-43 aggregate accumulation)","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP plus biochemical GEF assay, replicated across multiple independent labs in same year","pmids":["27103069","27193190","27617292","27494456"],"is_preprint":false},{"year":2016,"finding":"WDR41 is tightly associated with the Golgi complex and the C9orf72/SMCR8 heterodimer, and the trimeric complex associates with the FIP200/ULK1 autophagy initiation complex.","method":"Co-immunoprecipitation, subcellular fractionation/immunofluorescence localization","journal":"Acta neuropathologica communications","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP and localization from single lab, corroborated by other labs for complex membership","pmids":["27193190"],"is_preprint":false},{"year":2016,"finding":"The C9ORF72-SMCR8-WDR41 complex also contains ATG101 and displays GTPase activity; SMCR8/C9ORF72 interacts with the ULK1 complex to regulate ULK1 expression and activity, placing the complex at autophagy initiation.","method":"Co-immunoprecipitation, in vitro GTPase assay, Smcr8 knockout mouse with autophagy phenotype","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro biochemical assay plus genetic KO with defined autophagy phenotype and mechanistic follow-up","pmids":["27617292"],"is_preprint":false},{"year":2018,"finding":"WDR41 deficiency phenocopies SMCR8 loss, causing accumulation of LysoTracker-positive vesicles, delayed phagosome maturation, and excessive endosomal TLR signaling, demonstrating WDR41's role in lysosomal/phagosomal maturation.","method":"WDR41 knockout cells, LysoTracker staining, phagosome maturation assay, inflammatory cytokine measurement","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with multiple defined cellular phenotypes, single lab","pmids":["30442666"],"is_preprint":false},{"year":2018,"finding":"WDR41 is required for recruitment of the C9orf72-SMCR8 complex to lysosomes in response to amino acid starvation, and this recruitment is critical for mTORC1 signaling; constitutive lysosomal targeting of C9orf72 rescues the requirement for WDR41 in mTORC1 activation.","method":"WDR41 knockout cells, lysosome fractionation/immunofluorescence, mTORC1 activity assay, rescue with constitutive lysosomal-targeted C9orf72","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — KO with multiple orthogonal methods (fractionation, signaling assay) and epistatic rescue experiment","pmids":["29995611"],"is_preprint":false},{"year":2020,"finding":"Cryo-EM structure of the C9orf72-SMCR8-WDR41 complex reveals WDR41 is a β-propeller protein that binds the DENN domain of SMCR8; contacts between WDR41 and SMCR8-DENN drive lysosomal localization of the complex under amino acid starvation; the complex functions as a GAP for ARF family GTPases.","method":"Cryo-electron microscopy structure determination, in vitro GAP activity assay, mutagenesis of interface residues","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — high-resolution cryo-EM structure with in vitro biochemical validation and mutagenesis","pmids":["32848248"],"is_preprint":false},{"year":2020,"finding":"Cryo-EM structure at 3.2 Å shows the C9orf72-SMCR8-WDR41 complex forms a dimer of heterotrimers; WDR41 binds the DENN domain of SMCR8 via its N-terminal β-strand and C-terminal helix without direct contact to C9orf72; SMCR8 Arg147 is the catalytic arginine finger mediating GAP activity toward Rab8a and Rab11a.","method":"Cryo-EM structure determination, in vitro GAP assay, Arg147 mutagenesis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — high-resolution structure with biochemical validation and active-site mutagenesis","pmids":["32303654"],"is_preprint":false},{"year":2020,"finding":"An interaction between WDR41 and the lysosomal cationic amino acid transporter PQLC2 mediates recruitment of the C9orf72-SMCR8-WDR41 complex to lysosomes; this interaction is negatively regulated by arginine, lysine, and histidine (PQLC2 substrates).","method":"Co-immunoprecipitation, lysosome fractionation, amino acid titration experiments, WDR41/PQLC2 interaction mapping","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP with functional amino acid regulation assay and mechanistic specificity, replicated","pmids":["31851326"],"is_preprint":false},{"year":2021,"finding":"The WDR41-PQLC2 interaction is mediated by a short peptide motif in a flexible loop of WDR41 that inserts into a cavity presented by the inward-facing conformation of PQLC2; PQLC2 conformational changes related to substrate transport regulate WDR41 binding site availability (transceptor mechanism).","method":"Mutagenesis of WDR41 loop motif, co-immunoprecipitation, structure-guided interaction mapping","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 — mutagenesis of defined binding motif combined with mechanistic model validated by multiple methods","pmids":["33597295"],"is_preprint":false},{"year":2021,"finding":"Cryo-EM structure of C9orf72-SMCR8 at 3.8 Å reveals two distinct dimerization interfaces; deletion of a coiled-coil region in the uDENN domain of SMCR8 reduces interaction of the C9orf72-SMCR8 complex with FIP200 upon starvation, implicating this region as an interaction platform for autophagy initiation.","method":"Cryo-EM structure determination, deletion mutagenesis, co-immunoprecipitation with FIP200","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 1-2 — cryo-EM structure combined with mutagenesis and interaction assay","pmids":["34297726"],"is_preprint":false},{"year":2021,"finding":"Cryo-EM structure of ARF1-GDP-BeF3- bound to C9orf72:SMCR8:WDR41 shows SMCR8longin and C9orf72longin domains form the ARF1 binding pocket; SMCR8 Arg147 acts as catalytic finger; mutations in ARF1 or C9orf72 interfacial residues reduce/eliminate GAP activity; ARF1 is preferred substrate over RAB8A (~10-fold lower Km).","method":"Cryo-EM structure of substrate-bound complex, in vitro GAP assay, mutagenesis of active-site and interfacial residues","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — substrate-bound cryo-EM structure with rigorous mutagenesis and quantitative in vitro enzyme kinetics","pmids":["34145292"],"is_preprint":false},{"year":2020,"finding":"C9orf72 long isoform complexes with and stabilizes SMCR8, enabling interaction with WDR41; loss of SMCR8 (and consequently WDR41 complex function) increases lysosomal exocytosis in macrophages, as evidenced by elevated surface LAMP1 and secretion of lysosomal components.","method":"Quantitative mass spectrometry proteomics, Co-IP, Smcr8 KO mouse, surface LAMP1 flow cytometry, lysosomal secretion assay","journal":"Genes & development","confidence":"Medium","confidence_rationale":"Tier 2 — MS proteomics plus genetic KO with cellular readouts, single lab","pmids":["29950492"],"is_preprint":false},{"year":2020,"finding":"WDR41 (as part of the SMCR8-WDR41-C9ORF72 complex) is required for normal lysosomal degradation of endocytosed TLR ligands; WDR41 deficiency causes accumulation of endosomal vesicles and prolonged TLR signaling.","method":"WDR41 knockout phenotyping, LysoTracker vesicle staining, cytokine response assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotypes, but WDR41-specific mechanism not separated from complex","pmids":["30442666"],"is_preprint":false},{"year":2020,"finding":"WDR41 knockdown in triple-negative breast cancer cells activates the AKT/GSK-3β/β-catenin pathway, promoting cell proliferation and migration; WDR41 overexpression suppresses tumor growth in vivo and represses this pathway.","method":"siRNA knockdown, overexpression, AKT inhibitor rescue, in vivo xenograft","journal":"Journal of cellular and molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2-3 — loss- and gain-of-function with pathway inhibitor rescue, single lab, context may be cancer-specific","pmids":["32394588"],"is_preprint":false}],"current_model":"WDR41 is a β-propeller protein that forms a stable heterotrimeric complex with C9orf72 and SMCR8 (CSW complex); within this complex, WDR41 binds the DENN domain of SMCR8 (but not C9orf72 directly) and is essential for recruiting the complex to lysosomes by interacting—via a short flexible loop motif—with the lysosomal cationic amino acid transporter PQLC2, whose conformational state (regulated by arginine/lysine/histidine occupancy) gates this interaction; lysosomal recruitment of the complex supports mTORC1 signaling and coordinates lysosomal responses to amino acid availability, while the C9orf72-SMCR8 heterodimer within the complex provides GAP activity toward ARF GTPases (and to a lesser extent RAB8A/RAB11A) through a catalytic arginine finger (SMCR8 Arg147) positioned in the ARF active site."},"narrative":{"teleology":[{"year":2016,"claim":"Identification of WDR41 as a stable subunit of a trimeric complex with C9orf72 and SMCR8 established the CSW complex as a functional unit linked to RAB GEF activity and autophagy regulation, answering the question of whether C9orf72 acted alone or as part of a defined multiprotein assembly.","evidence":"Reciprocal co-immunoprecipitation, in vitro GEF assays for RAB8a/RAB39b, and knockdown/KO studies with autophagic flux readouts across multiple independent laboratories","pmids":["27103069","27193190","27617292","27494456"],"confidence":"High","gaps":["GEF versus GAP activity assignment was later revised; the initial GEF claim for RABs was not independently confirmed with purified components","Direct binding topology among the three subunits was unknown","Identity of the lysosomal recruitment mechanism was unresolved"]},{"year":2016,"claim":"Demonstrating that the CSW complex associates with the ULK1–FIP200 autophagy initiation complex and regulates ULK1 expression placed the complex at the earliest step of autophagosome formation, answering how it connects to the core autophagy machinery.","evidence":"Co-immunoprecipitation with ULK1/ATG101, Smcr8 knockout mouse with autophagy defects","pmids":["27617292"],"confidence":"High","gaps":["Whether WDR41 itself directly contacts ULK1/FIP200 or is required only for complex integrity was not resolved","Stoichiometry of the CSW–ULK1 supercomplex was not determined"]},{"year":2018,"claim":"Showing that WDR41 knockout phenocopies SMCR8 loss—with lysosomal vesicle accumulation, delayed phagosome maturation, and excessive TLR signaling—established that WDR41 is functionally non-redundant and essential for the complex's role in endolysosomal trafficking and innate immune regulation.","evidence":"WDR41 KO cells with LysoTracker staining, phagosome maturation kinetics, and inflammatory cytokine assays","pmids":["30442666"],"confidence":"Medium","gaps":["Whether the phenotypes reflect loss of WDR41-specific function or destabilization of the entire complex was not distinguished","Downstream GTPase targets responsible for these phenotypes were not identified"]},{"year":2018,"claim":"Demonstrating that WDR41 is required for amino-acid-starvation-induced recruitment of the CSW complex to lysosomes and for mTORC1 reactivation—rescued by constitutive lysosomal targeting of C9orf72—answered the question of WDR41's non-enzymatic role: it is the lysosomal targeting subunit.","evidence":"WDR41 KO, lysosome fractionation, mTORC1 activity assays, epistatic rescue with lysosome-targeted C9orf72","pmids":["29995611"],"confidence":"High","gaps":["The lysosomal receptor for WDR41 was unknown","Structural basis for WDR41's targeting function was unresolved"]},{"year":2020,"claim":"Identification of the lysosomal transporter PQLC2 as the WDR41 receptor, and demonstration that arginine/lysine/histidine negatively regulate this interaction, revealed the amino acid sensing logic: cationic amino acid depletion from lysosomes exposes the WDR41 binding site on PQLC2.","evidence":"Reciprocal co-immunoprecipitation, lysosome fractionation, amino acid titration of WDR41–PQLC2 binding","pmids":["31851326"],"confidence":"High","gaps":["The structural details of the WDR41–PQLC2 interface were not yet resolved","Whether PQLC2 conformational state directly controls WDR41 access was not proven"]},{"year":2020,"claim":"Cryo-EM structures of the CSW complex resolved WDR41 as a β-propeller contacting only the SMCR8 DENN domain, corrected the enzymatic assignment from GEF to GAP (toward ARF GTPases), and showed the complex forms a dimer of heterotrimers with SMCR8 Arg147 as the catalytic arginine finger.","evidence":"Cryo-EM at 3.2–3.8 Å resolution, in vitro GAP assays, interface and active-site mutagenesis","pmids":["32848248","32303654"],"confidence":"High","gaps":["Physiological ARF substrates in vivo were not validated","The biological function of complex dimerization was unclear","WDR41's contribution to catalysis beyond scaffolding was not defined"]},{"year":2021,"claim":"Fine mapping of the WDR41–PQLC2 interface showed that a short peptide motif in a flexible WDR41 loop inserts into a cavity exposed only in the inward-facing conformation of PQLC2, establishing a transceptor mechanism whereby transporter conformational cycling gates signaling complex recruitment.","evidence":"Structure-guided mutagenesis of the WDR41 loop motif, co-immunoprecipitation","pmids":["33597295"],"confidence":"High","gaps":["No high-resolution structure of the WDR41–PQLC2 interface exists","Whether other transporters can substitute for PQLC2 in other tissues is untested"]},{"year":2021,"claim":"A substrate-bound cryo-EM structure of ARF1-GDP-BeF₃⁻ with the CSW complex showed the SMCR8/C9orf72 longin domains form the ARF1 binding pocket and confirmed ARF1 as the preferred GAP substrate (~10-fold lower Km than RAB8A), resolving the long-standing question of enzymatic specificity.","evidence":"Cryo-EM of the transition-state complex, quantitative in vitro GAP kinetics, active-site and interfacial mutagenesis","pmids":["34145292"],"confidence":"High","gaps":["In vivo ARF1 regulation by the CSW complex has not been validated in cellular systems","Roles of specific ARF substrates in autophagy or lysosomal function downstream of the complex remain uncharacterized"]},{"year":null,"claim":"Key open questions include: (1) how CSW complex GAP activity toward ARF GTPases mechanistically connects to its roles in autophagy initiation, mTORC1 signaling, and lysosomal exocytosis; (2) whether WDR41 has functions independent of the CSW complex; and (3) the structural basis of the WDR41–PQLC2 interface at atomic resolution.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structure of the WDR41–PQLC2 binary complex","ARF-dependent downstream effectors mediating CSW phenotypes are unidentified","WDR41-independent functions remain unexplored"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[4,5,7,8]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,5,6,10]}],"localization":[{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[4,5,7,8]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[1]}],"pathway":[{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[0,2,9]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[4,10]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,12]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[3,11]}],"complexes":["C9orf72-SMCR8-WDR41 (CSW) complex"],"partners":["SMCR8","C9ORF72","PQLC2","FIP200","ULK1","ATG101","ARF1"],"other_free_text":[]},"mechanistic_narrative":"WDR41 is a β-propeller scaffold protein that functions as an essential subunit of the C9orf72–SMCR8–WDR41 (CSW) heterotrimeric complex, coupling lysosomal amino acid sensing to autophagy initiation, mTORC1 signaling, and GTPase regulation. WDR41 binds the DENN domain of SMCR8 via its N-terminal β-strand and C-terminal helix—without directly contacting C9orf72—and recruits the entire complex to lysosomes by engaging the cationic amino acid transporter PQLC2 through a short flexible loop motif that inserts into a cavity exposed only in the inward-facing, substrate-free conformation of PQLC2, thereby transducing lysosomal arginine/lysine/histidine availability into complex localization [PMID:32848248, PMID:31851326, PMID:33597295]. Once at the lysosome, the C9orf72–SMCR8 longin-domain heterodimer within the complex provides GAP activity preferentially toward ARF1 (and to a lesser extent RAB8A/RAB11A), with SMCR8 Arg147 serving as the catalytic arginine finger, while the complex also associates with the ULK1–FIP200 autophagy initiation machinery to regulate autophagic flux [PMID:34145292, PMID:32303654, PMID:27617292]. Loss of WDR41 phenocopies SMCR8 deficiency, causing accumulation of LysoTracker-positive vesicles, delayed phagosome maturation, excessive endosomal TLR signaling, impaired mTORC1 reactivation, and increased lysosomal exocytosis [PMID:30442666, PMID:29995611, PMID:29950492]."},"prefetch_data":{"uniprot":{"accession":"Q9HAD4","full_name":"WD repeat-containing protein 41","aliases":[],"length_aa":459,"mass_kda":51.7,"function":"Non-catalytic component of the C9orf72-SMCR8 complex, a complex that has guanine nucleotide exchange factor (GEF) activity and regulates autophagy (PubMed:27103069, PubMed:27193190, PubMed:27617292, PubMed:28195531). The C9orf72-SMCR8 complex promotes the exchange of GDP to GTP, converting inactive GDP-bound RAB8A and RAB39B into their active GTP-bound form, thereby promoting autophagosome maturation (PubMed:27103069). As part of the C9orf72-SMCR8 complex, stimulates RAB8A and RAB11A GTPase activity in vitro, however WDR42 is shown not be an essential complex component for this function (PubMed:32303654). The C9orf72-SMCR8 complex also acts as a negative regulator of autophagy initiation by interacting with the ULK1/ATG1 kinase complex and inhibiting its protein kinase activity (PubMed:27103069, PubMed:27617292)","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q9HAD4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/WDR41","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/WDR41","total_profiled":1310},"omim":[{"mim_id":"617502","title":"WD REPEAT-CONTAINING PROTEIN 41; WDR41","url":"https://www.omim.org/entry/617502"},{"mim_id":"617074","title":"SMITH-MAGENIS SYNDROME CHROMOSOME REGION, CANDIDATE GENE 8; SMCR8","url":"https://www.omim.org/entry/617074"},{"mim_id":"614760","title":"SOLUTE CARRIER FAMILY 66, MEMBER 1; SLC66A1","url":"https://www.omim.org/entry/614760"},{"mim_id":"614260","title":"CHROMOSOME 9 OPEN READING FRAME 72; C9ORF72","url":"https://www.omim.org/entry/614260"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Golgi apparatus","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/WDR41"},"hgnc":{"alias_symbol":["FLJ10904"],"prev_symbol":[]},"alphafold":{"accession":"Q9HAD4","domains":[{"cath_id":"2.130.10.10","chopping":"29-41_309-354_391-452","consensus_level":"medium","plddt":93.273,"start":29,"end":452}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HAD4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HAD4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9HAD4-F1-predicted_aligned_error_v6.png","plddt_mean":82.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=WDR41","jax_strain_url":"https://www.jax.org/strain/search?query=WDR41"},"sequence":{"accession":"Q9HAD4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9HAD4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9HAD4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9HAD4"}},"corpus_meta":[{"pmid":"27103069","id":"PMC_27103069","title":"Loss of C9ORF72 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Pathophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/38390945","citation_count":3,"is_preprint":false},{"pmid":"40808945","id":"PMC_40808945","title":"Transcriptome-wide N6-methyladenosinem modifications analysis of chicken cecum in responding to Campylobacter jejuni inoculation.","date":"2025","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/40808945","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":17194,"output_tokens":3413,"usd":0.051388},"stage2":{"model":"claude-opus-4-6","input_tokens":6832,"output_tokens":2909,"usd":0.160328},"total_usd":0.211716,"stage1_batch_id":"msgbatch_01BparvgRZ9S2LMidvaoo86K","stage2_batch_id":"msgbatch_01NkBfv9SVZWthhS7j6mU6G3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2016,\n      \"finding\": \"WDR41 forms a stable trimeric complex with C9ORF72 and SMCR8, and this complex acts as a GDP/GTP exchange factor (GEF) for RAB8a and RAB39b, thereby controlling autophagic flux.\",\n      \"method\": \"Co-immunoprecipitation, GEF activity assay, knockdown with autophagic flux readouts (p62/TDP-43 aggregate accumulation)\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP plus biochemical GEF assay, replicated across multiple independent labs in same year\",\n      \"pmids\": [\"27103069\", \"27193190\", \"27617292\", \"27494456\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"WDR41 is tightly associated with the Golgi complex and the C9orf72/SMCR8 heterodimer, and the trimeric complex associates with the FIP200/ULK1 autophagy initiation complex.\",\n      \"method\": \"Co-immunoprecipitation, subcellular fractionation/immunofluorescence localization\",\n      \"journal\": \"Acta neuropathologica communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP and localization from single lab, corroborated by other labs for complex membership\",\n      \"pmids\": [\"27193190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"The C9ORF72-SMCR8-WDR41 complex also contains ATG101 and displays GTPase activity; SMCR8/C9ORF72 interacts with the ULK1 complex to regulate ULK1 expression and activity, placing the complex at autophagy initiation.\",\n      \"method\": \"Co-immunoprecipitation, in vitro GTPase assay, Smcr8 knockout mouse with autophagy phenotype\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro biochemical assay plus genetic KO with defined autophagy phenotype and mechanistic follow-up\",\n      \"pmids\": [\"27617292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"WDR41 deficiency phenocopies SMCR8 loss, causing accumulation of LysoTracker-positive vesicles, delayed phagosome maturation, and excessive endosomal TLR signaling, demonstrating WDR41's role in lysosomal/phagosomal maturation.\",\n      \"method\": \"WDR41 knockout cells, LysoTracker staining, phagosome maturation assay, inflammatory cytokine measurement\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with multiple defined cellular phenotypes, single lab\",\n      \"pmids\": [\"30442666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"WDR41 is required for recruitment of the C9orf72-SMCR8 complex to lysosomes in response to amino acid starvation, and this recruitment is critical for mTORC1 signaling; constitutive lysosomal targeting of C9orf72 rescues the requirement for WDR41 in mTORC1 activation.\",\n      \"method\": \"WDR41 knockout cells, lysosome fractionation/immunofluorescence, mTORC1 activity assay, rescue with constitutive lysosomal-targeted C9orf72\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — KO with multiple orthogonal methods (fractionation, signaling assay) and epistatic rescue experiment\",\n      \"pmids\": [\"29995611\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Cryo-EM structure of the C9orf72-SMCR8-WDR41 complex reveals WDR41 is a β-propeller protein that binds the DENN domain of SMCR8; contacts between WDR41 and SMCR8-DENN drive lysosomal localization of the complex under amino acid starvation; the complex functions as a GAP for ARF family GTPases.\",\n      \"method\": \"Cryo-electron microscopy structure determination, in vitro GAP activity assay, mutagenesis of interface residues\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution cryo-EM structure with in vitro biochemical validation and mutagenesis\",\n      \"pmids\": [\"32848248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Cryo-EM structure at 3.2 Å shows the C9orf72-SMCR8-WDR41 complex forms a dimer of heterotrimers; WDR41 binds the DENN domain of SMCR8 via its N-terminal β-strand and C-terminal helix without direct contact to C9orf72; SMCR8 Arg147 is the catalytic arginine finger mediating GAP activity toward Rab8a and Rab11a.\",\n      \"method\": \"Cryo-EM structure determination, in vitro GAP assay, Arg147 mutagenesis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution structure with biochemical validation and active-site mutagenesis\",\n      \"pmids\": [\"32303654\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"An interaction between WDR41 and the lysosomal cationic amino acid transporter PQLC2 mediates recruitment of the C9orf72-SMCR8-WDR41 complex to lysosomes; this interaction is negatively regulated by arginine, lysine, and histidine (PQLC2 substrates).\",\n      \"method\": \"Co-immunoprecipitation, lysosome fractionation, amino acid titration experiments, WDR41/PQLC2 interaction mapping\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP with functional amino acid regulation assay and mechanistic specificity, replicated\",\n      \"pmids\": [\"31851326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The WDR41-PQLC2 interaction is mediated by a short peptide motif in a flexible loop of WDR41 that inserts into a cavity presented by the inward-facing conformation of PQLC2; PQLC2 conformational changes related to substrate transport regulate WDR41 binding site availability (transceptor mechanism).\",\n      \"method\": \"Mutagenesis of WDR41 loop motif, co-immunoprecipitation, structure-guided interaction mapping\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis of defined binding motif combined with mechanistic model validated by multiple methods\",\n      \"pmids\": [\"33597295\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cryo-EM structure of C9orf72-SMCR8 at 3.8 Å reveals two distinct dimerization interfaces; deletion of a coiled-coil region in the uDENN domain of SMCR8 reduces interaction of the C9orf72-SMCR8 complex with FIP200 upon starvation, implicating this region as an interaction platform for autophagy initiation.\",\n      \"method\": \"Cryo-EM structure determination, deletion mutagenesis, co-immunoprecipitation with FIP200\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — cryo-EM structure combined with mutagenesis and interaction assay\",\n      \"pmids\": [\"34297726\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cryo-EM structure of ARF1-GDP-BeF3- bound to C9orf72:SMCR8:WDR41 shows SMCR8longin and C9orf72longin domains form the ARF1 binding pocket; SMCR8 Arg147 acts as catalytic finger; mutations in ARF1 or C9orf72 interfacial residues reduce/eliminate GAP activity; ARF1 is preferred substrate over RAB8A (~10-fold lower Km).\",\n      \"method\": \"Cryo-EM structure of substrate-bound complex, in vitro GAP assay, mutagenesis of active-site and interfacial residues\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — substrate-bound cryo-EM structure with rigorous mutagenesis and quantitative in vitro enzyme kinetics\",\n      \"pmids\": [\"34145292\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"C9orf72 long isoform complexes with and stabilizes SMCR8, enabling interaction with WDR41; loss of SMCR8 (and consequently WDR41 complex function) increases lysosomal exocytosis in macrophages, as evidenced by elevated surface LAMP1 and secretion of lysosomal components.\",\n      \"method\": \"Quantitative mass spectrometry proteomics, Co-IP, Smcr8 KO mouse, surface LAMP1 flow cytometry, lysosomal secretion assay\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MS proteomics plus genetic KO with cellular readouts, single lab\",\n      \"pmids\": [\"29950492\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"WDR41 (as part of the SMCR8-WDR41-C9ORF72 complex) is required for normal lysosomal degradation of endocytosed TLR ligands; WDR41 deficiency causes accumulation of endosomal vesicles and prolonged TLR signaling.\",\n      \"method\": \"WDR41 knockout phenotyping, LysoTracker vesicle staining, cytokine response assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotypes, but WDR41-specific mechanism not separated from complex\",\n      \"pmids\": [\"30442666\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"WDR41 knockdown in triple-negative breast cancer cells activates the AKT/GSK-3β/β-catenin pathway, promoting cell proliferation and migration; WDR41 overexpression suppresses tumor growth in vivo and represses this pathway.\",\n      \"method\": \"siRNA knockdown, overexpression, AKT inhibitor rescue, in vivo xenograft\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — loss- and gain-of-function with pathway inhibitor rescue, single lab, context may be cancer-specific\",\n      \"pmids\": [\"32394588\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"WDR41 is a β-propeller protein that forms a stable heterotrimeric complex with C9orf72 and SMCR8 (CSW complex); within this complex, WDR41 binds the DENN domain of SMCR8 (but not C9orf72 directly) and is essential for recruiting the complex to lysosomes by interacting—via a short flexible loop motif—with the lysosomal cationic amino acid transporter PQLC2, whose conformational state (regulated by arginine/lysine/histidine occupancy) gates this interaction; lysosomal recruitment of the complex supports mTORC1 signaling and coordinates lysosomal responses to amino acid availability, while the C9orf72-SMCR8 heterodimer within the complex provides GAP activity toward ARF GTPases (and to a lesser extent RAB8A/RAB11A) through a catalytic arginine finger (SMCR8 Arg147) positioned in the ARF active site.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"WDR41 is a β-propeller scaffold protein that functions as an essential subunit of the C9orf72–SMCR8–WDR41 (CSW) heterotrimeric complex, coupling lysosomal amino acid sensing to autophagy initiation, mTORC1 signaling, and GTPase regulation. WDR41 binds the DENN domain of SMCR8 via its N-terminal β-strand and C-terminal helix—without directly contacting C9orf72—and recruits the entire complex to lysosomes by engaging the cationic amino acid transporter PQLC2 through a short flexible loop motif that inserts into a cavity exposed only in the inward-facing, substrate-free conformation of PQLC2, thereby transducing lysosomal arginine/lysine/histidine availability into complex localization [PMID:32848248, PMID:31851326, PMID:33597295]. Once at the lysosome, the C9orf72–SMCR8 longin-domain heterodimer within the complex provides GAP activity preferentially toward ARF1 (and to a lesser extent RAB8A/RAB11A), with SMCR8 Arg147 serving as the catalytic arginine finger, while the complex also associates with the ULK1–FIP200 autophagy initiation machinery to regulate autophagic flux [PMID:34145292, PMID:32303654, PMID:27617292]. Loss of WDR41 phenocopies SMCR8 deficiency, causing accumulation of LysoTracker-positive vesicles, delayed phagosome maturation, excessive endosomal TLR signaling, impaired mTORC1 reactivation, and increased lysosomal exocytosis [PMID:30442666, PMID:29995611, PMID:29950492].\",\n  \"teleology\": [\n    {\n      \"year\": 2016,\n      \"claim\": \"Identification of WDR41 as a stable subunit of a trimeric complex with C9orf72 and SMCR8 established the CSW complex as a functional unit linked to RAB GEF activity and autophagy regulation, answering the question of whether C9orf72 acted alone or as part of a defined multiprotein assembly.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, in vitro GEF assays for RAB8a/RAB39b, and knockdown/KO studies with autophagic flux readouts across multiple independent laboratories\",\n      \"pmids\": [\"27103069\", \"27193190\", \"27617292\", \"27494456\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"GEF versus GAP activity assignment was later revised; the initial GEF claim for RABs was not independently confirmed with purified components\",\n        \"Direct binding topology among the three subunits was unknown\",\n        \"Identity of the lysosomal recruitment mechanism was unresolved\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Demonstrating that the CSW complex associates with the ULK1–FIP200 autophagy initiation complex and regulates ULK1 expression placed the complex at the earliest step of autophagosome formation, answering how it connects to the core autophagy machinery.\",\n      \"evidence\": \"Co-immunoprecipitation with ULK1/ATG101, Smcr8 knockout mouse with autophagy defects\",\n      \"pmids\": [\"27617292\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether WDR41 itself directly contacts ULK1/FIP200 or is required only for complex integrity was not resolved\",\n        \"Stoichiometry of the CSW–ULK1 supercomplex was not determined\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showing that WDR41 knockout phenocopies SMCR8 loss—with lysosomal vesicle accumulation, delayed phagosome maturation, and excessive TLR signaling—established that WDR41 is functionally non-redundant and essential for the complex's role in endolysosomal trafficking and innate immune regulation.\",\n      \"evidence\": \"WDR41 KO cells with LysoTracker staining, phagosome maturation kinetics, and inflammatory cytokine assays\",\n      \"pmids\": [\"30442666\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether the phenotypes reflect loss of WDR41-specific function or destabilization of the entire complex was not distinguished\",\n        \"Downstream GTPase targets responsible for these phenotypes were not identified\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating that WDR41 is required for amino-acid-starvation-induced recruitment of the CSW complex to lysosomes and for mTORC1 reactivation—rescued by constitutive lysosomal targeting of C9orf72—answered the question of WDR41's non-enzymatic role: it is the lysosomal targeting subunit.\",\n      \"evidence\": \"WDR41 KO, lysosome fractionation, mTORC1 activity assays, epistatic rescue with lysosome-targeted C9orf72\",\n      \"pmids\": [\"29995611\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The lysosomal receptor for WDR41 was unknown\",\n        \"Structural basis for WDR41's targeting function was unresolved\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of the lysosomal transporter PQLC2 as the WDR41 receptor, and demonstration that arginine/lysine/histidine negatively regulate this interaction, revealed the amino acid sensing logic: cationic amino acid depletion from lysosomes exposes the WDR41 binding site on PQLC2.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, lysosome fractionation, amino acid titration of WDR41–PQLC2 binding\",\n      \"pmids\": [\"31851326\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The structural details of the WDR41–PQLC2 interface were not yet resolved\",\n        \"Whether PQLC2 conformational state directly controls WDR41 access was not proven\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Cryo-EM structures of the CSW complex resolved WDR41 as a β-propeller contacting only the SMCR8 DENN domain, corrected the enzymatic assignment from GEF to GAP (toward ARF GTPases), and showed the complex forms a dimer of heterotrimers with SMCR8 Arg147 as the catalytic arginine finger.\",\n      \"evidence\": \"Cryo-EM at 3.2–3.8 Å resolution, in vitro GAP assays, interface and active-site mutagenesis\",\n      \"pmids\": [\"32848248\", \"32303654\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Physiological ARF substrates in vivo were not validated\",\n        \"The biological function of complex dimerization was unclear\",\n        \"WDR41's contribution to catalysis beyond scaffolding was not defined\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Fine mapping of the WDR41–PQLC2 interface showed that a short peptide motif in a flexible WDR41 loop inserts into a cavity exposed only in the inward-facing conformation of PQLC2, establishing a transceptor mechanism whereby transporter conformational cycling gates signaling complex recruitment.\",\n      \"evidence\": \"Structure-guided mutagenesis of the WDR41 loop motif, co-immunoprecipitation\",\n      \"pmids\": [\"33597295\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No high-resolution structure of the WDR41–PQLC2 interface exists\",\n        \"Whether other transporters can substitute for PQLC2 in other tissues is untested\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"A substrate-bound cryo-EM structure of ARF1-GDP-BeF₃⁻ with the CSW complex showed the SMCR8/C9orf72 longin domains form the ARF1 binding pocket and confirmed ARF1 as the preferred GAP substrate (~10-fold lower Km than RAB8A), resolving the long-standing question of enzymatic specificity.\",\n      \"evidence\": \"Cryo-EM of the transition-state complex, quantitative in vitro GAP kinetics, active-site and interfacial mutagenesis\",\n      \"pmids\": [\"34145292\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"In vivo ARF1 regulation by the CSW complex has not been validated in cellular systems\",\n        \"Roles of specific ARF substrates in autophagy or lysosomal function downstream of the complex remain uncharacterized\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key open questions include: (1) how CSW complex GAP activity toward ARF GTPases mechanistically connects to its roles in autophagy initiation, mTORC1 signaling, and lysosomal exocytosis; (2) whether WDR41 has functions independent of the CSW complex; and (3) the structural basis of the WDR41–PQLC2 interface at atomic resolution.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No high-resolution structure of the WDR41–PQLC2 binary complex\",\n        \"ARF-dependent downstream effectors mediating CSW phenotypes are unidentified\",\n        \"WDR41-independent functions remain unexplored\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [4, 5, 7, 8]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 5, 6, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [4, 5, 7, 8]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [0, 2, 9]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [4, 10]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 12]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [3, 11]}\n    ],\n    \"complexes\": [\n      \"C9orf72-SMCR8-WDR41 (CSW) complex\"\n    ],\n    \"partners\": [\n      \"SMCR8\",\n      \"C9orf72\",\n      \"PQLC2\",\n      \"FIP200\",\n      \"ULK1\",\n      \"ATG101\",\n      \"ARF1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}