{"gene":"ARL6","run_date":"2026-06-09T22:02:44","timeline":{"discoveries":[{"year":2004,"finding":"ARL6 (BBS3) was identified as the gene mutated in Bardet-Biedl syndrome type 3; a homozygous stop mutation in ARL6 segregates with disease in the original BBS3 Bedouin kindred, establishing ARL6 as an ADP-ribosylation factor-like GTPase causally linked to BBS.","method":"Comparative genomic analysis combined with mutation screening and segregation analysis","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — mutation co-segregation in a defined pedigree, replicated by subsequent independent studies identifying additional mutations","pmids":["15258860"],"is_preprint":false},{"year":2010,"finding":"Crystal structure of GTP-bound ARL6/BBS3 was determined, revealing ring-like localization at the distal end of basal bodies near the ciliary gate. GTP- or GDP-locked variants of ARL6 influence primary cilium length and abundance. BBS-associated point mutations alter nucleotide binding, providing a structural/mechanistic explanation for pathogenesis. ARL6 also modulates Wnt signaling, and this function is abolished by BBS-associated mutations.","method":"X-ray crystallography, overexpression of GTP/GDP-locked variants in vivo (cilium length/abundance assays), functional Wnt signaling assays with BBS point mutants","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure combined with multiple functional assays (ciliary morphology, Wnt signaling) and mutagenesis in a single study","pmids":["20207729"],"is_preprint":false},{"year":2011,"finding":"In Bbs3 knockout mice, endogenous BBS3 and the BBSome physically interact and depend on each other for their ciliary localization. Loss of Bbs3 does not affect BBSome complex formation but disrupts ciliary localization of melanin concentrating hormone receptor 1 and affects retrograde transport of Smoothened inside cilia. BBS3 and the BBSome associate with membranes independently of each other.","method":"Bbs3 knockout mouse model, co-immunoprecipitation, ciliary localization assays, receptor trafficking assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo knockout with multiple orthogonal readouts (co-IP, localization, receptor trafficking) in a defined genetic model","pmids":["22139371"],"is_preprint":false},{"year":2010,"finding":"A vision-specific long isoform of BBS3 (BBS3L) was identified. Zebrafish knockdown of bbs3L impairs visual function and mislocalizes green cone opsin, but does not affect Kupffer's vesicle or melanosome transport (phenotypes caused by bbs3 knockdown). BBS3L RNA, but not BBS3 RNA, rescues vision defects and green opsin localization in zebrafish. A Bbs3L-null mouse presents with disrupted photoreceptor architecture without obesity.","method":"Antisense oligonucleotide knockdown in zebrafish, rescue experiments with isoform-specific RNA, Bbs3L-null mouse generation, visual function assays, opsin localization","journal":"PLoS genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (zebrafish KD, rescue, mouse KO) across two model systems establishing isoform-specific function","pmids":["20333246"],"is_preprint":false},{"year":2014,"finding":"Crystal structures of ARL6-GDP, ARL6-GTP, and the ARL6-GTP–BBS1 complex from Chlamydomonas reinhardtii were determined. ARL6-GTP binds the BBS1 β-propeller at blades 1 and 7; GDP-bound ARL6 cannot recruit the BBSome to membranes. Single point mutations at the ARL6-GTP–BBS1 interface abolish BBSome interaction and prevent BBSome import into cilia. The BBS1 M390R mutation (responsible for ~30% of BBS cases) fails to interact with ARL6-GTP.","method":"X-ray crystallography (ARL6-GDP, ARL6-GTP, ARL6-GTP–BBS1 complex structures), site-directed mutagenesis, ciliary import assays","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic resolution structures of multiple nucleotide states and protein complex, combined with mutagenesis and functional ciliary import assays","pmids":["25402481"],"is_preprint":false},{"year":2014,"finding":"The Rab-like GTPase IFT27/RABL4 (a component of IFT-B) directly interacts with nucleotide-free ARL6 upon disengagement from the rest of IFT-B. IFT27 prevents aggregation of nucleotide-free ARL6 in solution and promotes ARL6 activation (GTP loading), BBSome coat assembly, and exit of BBSome and associated cargoes from cilia.","method":"Unbiased proteomics, biochemical reconstitution assays, co-immunoprecipitation, in vitro aggregation assays","journal":"Developmental cell","confidence":"High","confidence_rationale":"Tier 1 / Moderate — biochemical reconstitution plus proteomics plus functional ciliary exit assays in a single study","pmids":["25443296"],"is_preprint":false},{"year":2020,"finding":"The Rab-like 5 GTPase IFT22/RABL5 binds and stabilizes ARL6 independently of its IFT-B1 association. When both IFT22 and BBS3/ARL6 are in their GTP-bound states, they recruit the BBSome to the basal body for coupling with IFT-B1 subcomplex and subsequent ciliary entry. BBS3/ARL6 interaction with the BBSome is mediated through direct BBS3–BBSome binding. IFT22 is not required for BBSome transport inside cilia, indicating BBSome is transferred from IFT22 to IFT trains at the ciliary base.","method":"Functional assays in Chlamydomonas reinhardtii, biochemical co-immunoprecipitation, single particle in vivo imaging, GTPase activity assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods including in vivo imaging, biochemistry, and GTPase assays in a defined genetic system","pmids":["31953262"],"is_preprint":false},{"year":2009,"finding":"BBS-causing mutations in ARL6 alter guanine nucleotide-binding properties; specifically, T31R selectively abrogates GTP-binding without affecting GDP binding. All BBS mutations tested result in low protein expression that can be restored by proteasome inhibition, indicating mutant ARL6 proteins are destabilized and degraded by the proteasome.","method":"In vitro guanine nucleotide-binding assays, site-directed mutagenesis, proteasome inhibitor treatment, protein expression analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro biochemical assays with mutagenesis in a single lab study without independent replication","pmids":["19236846"],"is_preprint":false},{"year":1999,"finding":"ARL6 protein is predominantly cytosolic but increases membrane association upon GTP-γS exposure. Using yeast two-hybrid screening, ARL6 was found to interact with SEC61β (a subunit of the SEC61 protein-conducting channel); this interaction was confirmed by co-immunoprecipitation in COS cells.","method":"Yeast two-hybrid screen, co-immunoprecipitation in COS cells, GTP-γS membrane association assay","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-IP confirmation of yeast two-hybrid hit, single lab, two methods but no functional consequence established","pmids":["10508919"],"is_preprint":false},{"year":2011,"finding":"A missense mutation BBS3 A89V rescues transport delays in zebrafish bbs3 morphants (syndromic function intact) but BBS3L A89V fails to rescue vision impairment, demonstrating that A89 is specifically required for the vision/retinal function of the long BBS3L isoform but is dispensable for general ciliary transport function.","method":"Zebrafish morpholino knockdown with isoform-specific RNA rescue, visual function assays, melanosome transport assays","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — rescue assays in zebrafish with two isoforms and a defined point mutation, single lab","pmids":["21282186"],"is_preprint":false},{"year":2012,"finding":"In Trypanosoma brucei, TbARL6 localizes to electron-dense vesicles (not cilia) via N-myristoylation. RNAi knockdown of TbARL6 reduces flagellum length. Tubulin was identified as an ARL6 interacting partner (pulldown), suggesting ARL6 anchors vesicles to cytoplasmic microtubules. Overexpression of BBS1 causes translocation of endogenous ARL6 to the flagellar pocket, and BBS1 overexpression combined with ARL6 RNAi has synergistic inhibitory effect on cell growth, indicating conservation of ARL6–BBSome interaction.","method":"RNA interference, co-localization, protein pulldown (tubulin interaction), BBS1 overexpression epistasis assay, cell growth assays in T. brucei","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi with defined flagellum length phenotype, pulldown, and genetic epistasis in a model organism; ortholog context limits direct mammalian inference","pmids":["22609302"],"is_preprint":false},{"year":2013,"finding":"Crystal structure of T. brucei ARL6 (TbArl6) with bound non-hydrolysable GTP analog (GppNp) at 2.0 Å resolution was determined. The structure reveals TbARL6 lacks the key catalytic glutamine for GTP hydrolysis (unlike most small GTPases), has a shorter N-terminus suggesting a different membrane insertion mechanism, and contains two conserved surface patches predicted to mediate protein–protein interactions.","method":"X-ray crystallography at 2.0 Å resolution, structural comparison with human ARL6","journal":"Protein science","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — high-quality structural data but from a trypanosome ortholog; functional validation limited to structural inference","pmids":["23184293"],"is_preprint":false},{"year":2016,"finding":"ARL6 localizes at the base of the primary cilium in RH30 rhabdomyosarcoma cells. Knockdown of ARL6 inhibits ciliogenesis and reduces Hedgehog signaling activity, leading to inhibited proliferation and promoted apoptosis of RH30 cells.","method":"Immunofluorescence localization, siRNA knockdown, ciliogenesis assay, Hedgehog signaling reporter assay, proliferation and apoptosis assays","journal":"Cell & bioscience","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single knockdown study with cellular phenotype but limited mechanistic detail on pathway placement","pmids":["27999656"],"is_preprint":false},{"year":2020,"finding":"miR-143-3p directly targets the 3'-UTR of ARL6 mRNA (confirmed by luciferase reporter assay). Elevated miR-143-3p reduces ARL6 levels and suppresses Wnt/β-catenin signaling (Wnt3a, β-catenin, LEF1, TCF1), inhibiting osteogenic differentiation of hBMSCs. Overexpression of ARL6 blocks cadmium-induced suppression of the Wnt/β-catenin pathway and rescues osteogenesis.","method":"Luciferase reporter assay (miR-143-3p binding to ARL6 3'-UTR), miRNA inhibition, lentiviral ARL6 overexpression, Wnt pathway component expression analysis, osteogenesis assay","journal":"Toxicology letters","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab study; luciferase assay confirms miRNA targeting but functional pathway link relies on overexpression/knockdown without direct mechanistic dissection of ARL6's role in Wnt signaling","pmids":["32522577"],"is_preprint":false}],"current_model":"ARL6 (BBS3) is an Arf-like small GTPase that cycles between GDP- and GTP-bound states; GTP-bound ARL6 directly binds the BBS1 subunit (blades 1 and 7 of its β-propeller) to recruit the BBSome coat complex to membranes, enabling ciliary import of the BBSome. At the basal body, IFT22/RABL5 stabilizes ARL6 and, when both are GTP-loaded, delivers the BBSome to IFT-B1 for ciliary entry; once inside cilia, IFT27/RABL4 acts as a guanine nucleotide exchange factor for ARL6 to drive BBSome coat assembly and cargo exit from cilia. Loss of ARL6 disrupts ciliary localization of the BBSome and specific signaling receptors (e.g., MCHR1, Smoothened), impairs retrograde ciliary transport, causes retinal degeneration (with the long eye-specific isoform BBS3L specifically required for cone opsin localization), and also modulates Wnt signaling through a GTP-dependent mechanism; BBS-causing mutations either impair GTP binding, disrupt the ARL6–BBS1 interface, or destabilize the protein leading to proteasomal degradation."},"narrative":{"mechanistic_narrative":"ARL6 (BBS3) is an ADP-ribosylation factor-like small GTPase that governs membrane recruitment and ciliary trafficking of the BBSome coat complex, and its loss-of-function causes Bardet-Biedl syndrome [PMID:15258860, PMID:22139371]. ARL6 cycles between GDP- and GTP-bound states; only GTP-bound ARL6 binds the BBS1 β-propeller (at blades 1 and 7) to recruit the BBSome to membranes, whereas GDP-bound ARL6 cannot, and single point mutations at the ARL6-GTP–BBS1 interface abolish the interaction and block BBSome import into cilia [PMID:25402481]. In knockout mice, ARL6 and the BBSome are mutually dependent for ciliary localization, and ARL6 loss disrupts ciliary localization of melanin-concentrating hormone receptor 1 and impairs retrograde transport of Smoothened, without preventing BBSome assembly [PMID:22139371]. The nucleotide cycle is controlled by two Rab-like GTPases: at the basal body IFT22/RABL5 binds and stabilizes ARL6 and, when both are GTP-loaded, recruits the BBSome for coupling to IFT-B1 and ciliary entry [PMID:31953262]; inside cilia IFT27/RABL4 binds nucleotide-free ARL6, prevents its aggregation, and promotes its GTP loading to drive BBSome coat assembly and cargo exit [PMID:25443296]. A vision-specific long isoform, BBS3L, is selectively required for cone opsin localization and photoreceptor function, distinct from the general ciliary transport role of the canonical isoform [PMID:20333246]. ARL6 additionally modulates Wnt signaling in a GTP-dependent manner abolished by BBS mutations [PMID:20207729]. BBS-causing mutations act through three mechanisms: impaired GTP binding (e.g., T31R), disruption of the ARL6–BBS1 interface, or protein destabilization and proteasomal degradation [PMID:25402481, PMID:19236846].","teleology":[{"year":2004,"claim":"Established that ARL6 is a disease gene, linking an Arf-like GTPase to ciliopathy for the first time and motivating mechanistic study of its trafficking role.","evidence":"Comparative genomics and segregation analysis of a homozygous stop mutation in the BBS3 Bedouin kindred","pmids":["15258860"],"confidence":"High","gaps":["Did not define the molecular function of ARL6","No mechanism connecting GTPase activity to cilia"]},{"year":2010,"claim":"Defined the structural basis of ARL6 nucleotide states and basal body localization, and showed nucleotide-locked variants alter cilium morphology and Wnt signaling, anchoring pathogenesis to nucleotide binding.","evidence":"X-ray crystallography of GTP-bound ARL6 with GTP/GDP-locked variant overexpression and Wnt reporter assays","pmids":["20207729"],"confidence":"High","gaps":["Did not identify the direct effector that ARL6-GTP recruits","Wnt mechanism downstream of ARL6 undefined"]},{"year":2010,"claim":"Distinguished isoform-specific functions, revealing a vision-dedicated long isoform (BBS3L) required for cone opsin localization separable from general ciliary transport.","evidence":"Isoform-specific zebrafish knockdown/RNA rescue and a Bbs3L-null mouse with photoreceptor defects","pmids":["20333246"],"confidence":"High","gaps":["Molecular basis of isoform-specific opsin trafficking unresolved","How BBS3L differs biochemically from BBS3 not established"]},{"year":2011,"claim":"Showed ARL6 and the BBSome are mutually dependent for ciliary localization and that ARL6 loss selectively mislocalizes signaling receptors, placing ARL6 as a BBSome trafficking partner rather than an assembly factor.","evidence":"Bbs3 knockout mouse with co-IP, ciliary localization, and receptor trafficking readouts (MCHR1, Smoothened)","pmids":["22139371"],"confidence":"High","gaps":["Did not resolve the direct ARL6–BBSome contact interface","Mechanism of retrograde Smoothened transport defect unclear"]},{"year":2011,"claim":"Pinpointed a residue (A89) required specifically for BBS3L vision function but dispensable for syndromic ciliary transport, refining isoform-specific structure-function.","evidence":"Zebrafish morpholino knockdown with isoform-specific A89V RNA rescue across visual and transport assays","pmids":["21282186"],"confidence":"Medium","gaps":["Single lab","Biochemical consequence of A89V not characterized"]},{"year":2014,"claim":"Resolved the atomic mechanism of BBSome recruitment, showing GTP-bound ARL6 binds the BBS1 β-propeller at blades 1 and 7 and that interface mutations (including BBS1 M390R) block ciliary import.","evidence":"Crystal structures of ARL6-GDP, ARL6-GTP, and ARL6-GTP–BBS1 complex from Chlamydomonas with mutagenesis and ciliary import assays","pmids":["25402481"],"confidence":"High","gaps":["Did not define how ARL6 is loaded with GTP at membranes","Mammalian validation of the interface relied on ortholog structure"]},{"year":2014,"claim":"Identified IFT27/RABL4 as a regulator of ARL6, preventing its aggregation and promoting GTP loading to drive BBSome coat assembly and ciliary exit, defining the intraciliary activation step.","evidence":"Proteomics, biochemical reconstitution, co-IP, and aggregation assays","pmids":["25443296"],"confidence":"High","gaps":["Whether IFT27 acts as a bona fide GEF not biochemically demonstrated here","GTP hydrolysis step / GAP unidentified"]},{"year":2020,"claim":"Established IFT22/RABL5 as a basal-body stabilizer that, when GTP-loaded together with ARL6, recruits the BBSome for IFT-B1 coupling and ciliary entry, completing the entry-versus-exit regulatory logic.","evidence":"Chlamydomonas functional assays, co-IP, single-particle in vivo imaging, and GTPase activity assays","pmids":["31953262"],"confidence":"High","gaps":["GEF/GAP that toggles ARL6 nucleotide state at the basal body unidentified","How BBSome is handed off from IFT22 to IFT trains not structurally resolved"]},{"year":2009,"claim":"Provided a biochemical classification of BBS mutations, distinguishing selective GTP-binding loss (T31R) from a shared proteasomal destabilization mechanism.","evidence":"In vitro nucleotide-binding assays, mutagenesis, and proteasome inhibitor rescue of mutant expression","pmids":["19236846"],"confidence":"Medium","gaps":["Single lab without independent replication","Degradation pathway components not identified"]},{"year":2012,"claim":"Demonstrated evolutionary conservation of the ARL6–BBS1 interaction and a microtubule-anchoring vesicular role in trypanosomes, broadening the functional context.","evidence":"RNAi, co-localization, tubulin pulldown, and BBS1 overexpression epistasis in T. brucei","pmids":["22609302"],"confidence":"Medium","gaps":["Ortholog context limits direct mammalian inference","Tubulin interaction not validated in mammalian cells"]},{"year":1999,"claim":"First showed GTP-dependent membrane association of ARL6 and a candidate SEC61β interaction, an early clue to nucleotide-regulated membrane behavior predating the ciliary model.","evidence":"Yeast two-hybrid screen, co-IP in COS cells, and GTP-γS membrane association assay","pmids":["10508919"],"confidence":"Medium","gaps":["Functional consequence of SEC61β interaction never established","Not integrated into the later ciliary trafficking model"]},{"year":2016,"claim":"Linked ARL6 to ciliogenesis-dependent Hedgehog signaling and tumor cell survival in a cancer context.","evidence":"Immunofluorescence, siRNA knockdown, ciliogenesis, Hedgehog reporter, and proliferation/apoptosis assays in RH30 cells","pmids":["27999656"],"confidence":"Low","gaps":["Single-lab knockdown with limited mechanistic dissection","Pathway placement of ARL6 in Hedgehog signaling unresolved"]},{"year":2020,"claim":"Connected ARL6 to miR-143-3p regulation and Wnt/β-catenin-dependent osteogenesis, extending its signaling role beyond cilia.","evidence":"Luciferase reporter, miRNA inhibition, ARL6 overexpression, and osteogenesis assays in hBMSCs","pmids":["32522577"],"confidence":"Low","gaps":["Mechanistic link of ARL6 to Wnt relies on overexpression/knockdown without direct dissection","Independent confirmation lacking"]},{"year":null,"claim":"The enzyme(s) that toggle ARL6 between GDP and GTP states at the basal body, and a definitive GAP, remain unidentified, leaving the in vivo nucleotide cycle incompletely closed.","evidence":"","pmids":[],"confidence":"High","gaps":["No GAP for ARL6 identified","GEF activity of IFT27 not biochemically proven","How signaling roles (Wnt, Hedgehog) mechanistically depend on ARL6 nucleotide cycling unresolved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0003924","term_label":"GTPase activity","supporting_discovery_ids":[1,6,7]}],"localization":[{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[2,12]},{"term_id":"GO:0005815","term_label":"microtubule organizing center","supporting_discovery_ids":[1,12]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[8]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[8,4]}],"pathway":[{"term_id":"R-HSA-9609507","term_label":"Protein localization","supporting_discovery_ids":[2,4,5,6]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,2]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[1,12]}],"complexes":["BBSome"],"partners":["BBS1","IFT27","IFT22","SEC61B"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9H0F7","full_name":"ADP-ribosylation factor-like protein 6","aliases":["Bardet-Biedl syndrome 3 protein"],"length_aa":186,"mass_kda":21.1,"function":"Involved in membrane protein trafficking at the base of the ciliary organelle. Mediates recruitment onto plasma membrane of the BBSome complex which would constitute a coat complex required for sorting of specific membrane proteins to the primary cilia (PubMed:20603001). Together with BBS1, is necessary for correct trafficking of PKD1 to primary cilia (By similarity). Together with the BBSome complex and LTZL1, controls SMO ciliary trafficking and contributes to the sonic hedgehog (SHH) pathway regulation (PubMed:22072986). May regulate cilia assembly and disassembly and subsequent ciliary signaling events such as the Wnt signaling cascade (PubMed:20207729). Isoform 2 may be required for proper retinal function and organization (By similarity)","subcellular_location":"Cell projection, cilium membrane; Cytoplasm, cytoskeleton, cilium axoneme; Cytoplasm, cytoskeleton, cilium basal body","url":"https://www.uniprot.org/uniprotkb/Q9H0F7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ARL6","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000113966","cell_line_id":"CID000498","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleoplasm","grade":3},{"compartment":"vesicles","grade":2}],"interactors":[{"gene":"YWHAZ","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000498","total_profiled":1310},"omim":[{"mim_id":"620505","title":"INTRAFLAGELLAR TRANSPORT 22; IFT22","url":"https://www.omim.org/entry/620505"},{"mim_id":"619270","title":"INTRAFLAGELLAR TRANSPORT-ASSOCIATED PROTEIN; IFTAP","url":"https://www.omim.org/entry/619270"},{"mim_id":"616495","title":"ADP-RIBOSYLATION FACTOR-LIKE GTPase 6-INTERACTING PROTEIN 6; ARL6IP6","url":"https://www.omim.org/entry/616495"},{"mim_id":"613575","title":"RETINITIS PIGMENTOSA 55; RP55","url":"https://www.omim.org/entry/613575"},{"mim_id":"609368","title":"ATLASTIN GTPase 2; ATL2","url":"https://www.omim.org/entry/609368"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Microtubules","reliability":"Approved"},{"location":"Primary cilium","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Primary cilium tip","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"retina","ntpm":35.2}],"url":"https://www.proteinatlas.org/search/ARL6"},"hgnc":{"alias_symbol":["RP55"],"prev_symbol":["BBS3"]},"alphafold":{"accession":"Q9H0F7","domains":[{"cath_id":"3.40.50.300","chopping":"15-182","consensus_level":"high","plddt":97.1705,"start":15,"end":182}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H0F7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H0F7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9H0F7-F1-predicted_aligned_error_v6.png","plddt_mean":94.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ARL6","jax_strain_url":"https://www.jax.org/strain/search?query=ARL6"},"sequence":{"accession":"Q9H0F7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9H0F7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9H0F7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9H0F7"}},"corpus_meta":[{"pmid":"15258860","id":"PMC_15258860","title":"Comparative genomic analysis identifies an ADP-ribosylation factor-like gene as the cause of Bardet-Biedl syndrome (BBS3).","date":"2004","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/15258860","citation_count":180,"is_preprint":false},{"pmid":"25443296","id":"PMC_25443296","title":"The intraflagellar transport protein IFT27 promotes BBSome exit from cilia through the GTPase ARL6/BBS3.","date":"2014","source":"Developmental cell","url":"https://pubmed.ncbi.nlm.nih.gov/25443296","citation_count":167,"is_preprint":false},{"pmid":"22139371","id":"PMC_22139371","title":"Bardet-Biedl syndrome 3 (Bbs3) knockout mouse model reveals common BBS-associated phenotypes and Bbs3 unique phenotypes.","date":"2011","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/22139371","citation_count":115,"is_preprint":false},{"pmid":"20207729","id":"PMC_20207729","title":"Bardet-Biedl syndrome-associated small GTPase ARL6 (BBS3) functions at or near the ciliary gate and modulates Wnt signaling.","date":"2010","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20207729","citation_count":87,"is_preprint":false},{"pmid":"10508919","id":"PMC_10508919","title":"A novel ADP-ribosylation like factor (ARL-6), interacts with the protein-conducting channel SEC61beta subunit.","date":"1999","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/10508919","citation_count":69,"is_preprint":false},{"pmid":"20333246","id":"PMC_20333246","title":"Identification and functional analysis of the vision-specific BBS3 (ARL6) long isoform.","date":"2010","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/20333246","citation_count":68,"is_preprint":false},{"pmid":"25402481","id":"PMC_25402481","title":"Structural basis for membrane targeting of the BBSome by ARL6.","date":"2014","source":"Nature structural & molecular 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GTP- or GDP-locked variants of ARL6 influence primary cilium length and abundance. BBS-associated point mutations alter nucleotide binding, providing a structural/mechanistic explanation for pathogenesis. ARL6 also modulates Wnt signaling, and this function is abolished by BBS-associated mutations.\",\n      \"method\": \"X-ray crystallography, overexpression of GTP/GDP-locked variants in vivo (cilium length/abundance assays), functional Wnt signaling assays with BBS point mutants\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure combined with multiple functional assays (ciliary morphology, Wnt signaling) and mutagenesis in a single study\",\n      \"pmids\": [\"20207729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In Bbs3 knockout mice, endogenous BBS3 and the BBSome physically interact and depend on each other for their ciliary localization. Loss of Bbs3 does not affect BBSome complex formation but disrupts ciliary localization of melanin concentrating hormone receptor 1 and affects retrograde transport of Smoothened inside cilia. BBS3 and the BBSome associate with membranes independently of each other.\",\n      \"method\": \"Bbs3 knockout mouse model, co-immunoprecipitation, ciliary localization assays, receptor trafficking assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo knockout with multiple orthogonal readouts (co-IP, localization, receptor trafficking) in a defined genetic model\",\n      \"pmids\": [\"22139371\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"A vision-specific long isoform of BBS3 (BBS3L) was identified. Zebrafish knockdown of bbs3L impairs visual function and mislocalizes green cone opsin, but does not affect Kupffer's vesicle or melanosome transport (phenotypes caused by bbs3 knockdown). BBS3L RNA, but not BBS3 RNA, rescues vision defects and green opsin localization in zebrafish. A Bbs3L-null mouse presents with disrupted photoreceptor architecture without obesity.\",\n      \"method\": \"Antisense oligonucleotide knockdown in zebrafish, rescue experiments with isoform-specific RNA, Bbs3L-null mouse generation, visual function assays, opsin localization\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (zebrafish KD, rescue, mouse KO) across two model systems establishing isoform-specific function\",\n      \"pmids\": [\"20333246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Crystal structures of ARL6-GDP, ARL6-GTP, and the ARL6-GTP–BBS1 complex from Chlamydomonas reinhardtii were determined. ARL6-GTP binds the BBS1 β-propeller at blades 1 and 7; GDP-bound ARL6 cannot recruit the BBSome to membranes. Single point mutations at the ARL6-GTP–BBS1 interface abolish BBSome interaction and prevent BBSome import into cilia. The BBS1 M390R mutation (responsible for ~30% of BBS cases) fails to interact with ARL6-GTP.\",\n      \"method\": \"X-ray crystallography (ARL6-GDP, ARL6-GTP, ARL6-GTP–BBS1 complex structures), site-directed mutagenesis, ciliary import assays\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic resolution structures of multiple nucleotide states and protein complex, combined with mutagenesis and functional ciliary import assays\",\n      \"pmids\": [\"25402481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The Rab-like GTPase IFT27/RABL4 (a component of IFT-B) directly interacts with nucleotide-free ARL6 upon disengagement from the rest of IFT-B. IFT27 prevents aggregation of nucleotide-free ARL6 in solution and promotes ARL6 activation (GTP loading), BBSome coat assembly, and exit of BBSome and associated cargoes from cilia.\",\n      \"method\": \"Unbiased proteomics, biochemical reconstitution assays, co-immunoprecipitation, in vitro aggregation assays\",\n      \"journal\": \"Developmental cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biochemical reconstitution plus proteomics plus functional ciliary exit assays in a single study\",\n      \"pmids\": [\"25443296\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The Rab-like 5 GTPase IFT22/RABL5 binds and stabilizes ARL6 independently of its IFT-B1 association. When both IFT22 and BBS3/ARL6 are in their GTP-bound states, they recruit the BBSome to the basal body for coupling with IFT-B1 subcomplex and subsequent ciliary entry. BBS3/ARL6 interaction with the BBSome is mediated through direct BBS3–BBSome binding. IFT22 is not required for BBSome transport inside cilia, indicating BBSome is transferred from IFT22 to IFT trains at the ciliary base.\",\n      \"method\": \"Functional assays in Chlamydomonas reinhardtii, biochemical co-immunoprecipitation, single particle in vivo imaging, GTPase activity assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods including in vivo imaging, biochemistry, and GTPase assays in a defined genetic system\",\n      \"pmids\": [\"31953262\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"BBS-causing mutations in ARL6 alter guanine nucleotide-binding properties; specifically, T31R selectively abrogates GTP-binding without affecting GDP binding. All BBS mutations tested result in low protein expression that can be restored by proteasome inhibition, indicating mutant ARL6 proteins are destabilized and degraded by the proteasome.\",\n      \"method\": \"In vitro guanine nucleotide-binding assays, site-directed mutagenesis, proteasome inhibitor treatment, protein expression analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro biochemical assays with mutagenesis in a single lab study without independent replication\",\n      \"pmids\": [\"19236846\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"ARL6 protein is predominantly cytosolic but increases membrane association upon GTP-γS exposure. Using yeast two-hybrid screening, ARL6 was found to interact with SEC61β (a subunit of the SEC61 protein-conducting channel); this interaction was confirmed by co-immunoprecipitation in COS cells.\",\n      \"method\": \"Yeast two-hybrid screen, co-immunoprecipitation in COS cells, GTP-γS membrane association assay\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-IP confirmation of yeast two-hybrid hit, single lab, two methods but no functional consequence established\",\n      \"pmids\": [\"10508919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"A missense mutation BBS3 A89V rescues transport delays in zebrafish bbs3 morphants (syndromic function intact) but BBS3L A89V fails to rescue vision impairment, demonstrating that A89 is specifically required for the vision/retinal function of the long BBS3L isoform but is dispensable for general ciliary transport function.\",\n      \"method\": \"Zebrafish morpholino knockdown with isoform-specific RNA rescue, visual function assays, melanosome transport assays\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — rescue assays in zebrafish with two isoforms and a defined point mutation, single lab\",\n      \"pmids\": [\"21282186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In Trypanosoma brucei, TbARL6 localizes to electron-dense vesicles (not cilia) via N-myristoylation. RNAi knockdown of TbARL6 reduces flagellum length. Tubulin was identified as an ARL6 interacting partner (pulldown), suggesting ARL6 anchors vesicles to cytoplasmic microtubules. Overexpression of BBS1 causes translocation of endogenous ARL6 to the flagellar pocket, and BBS1 overexpression combined with ARL6 RNAi has synergistic inhibitory effect on cell growth, indicating conservation of ARL6–BBSome interaction.\",\n      \"method\": \"RNA interference, co-localization, protein pulldown (tubulin interaction), BBS1 overexpression epistasis assay, cell growth assays in T. brucei\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi with defined flagellum length phenotype, pulldown, and genetic epistasis in a model organism; ortholog context limits direct mammalian inference\",\n      \"pmids\": [\"22609302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structure of T. brucei ARL6 (TbArl6) with bound non-hydrolysable GTP analog (GppNp) at 2.0 Å resolution was determined. The structure reveals TbARL6 lacks the key catalytic glutamine for GTP hydrolysis (unlike most small GTPases), has a shorter N-terminus suggesting a different membrane insertion mechanism, and contains two conserved surface patches predicted to mediate protein–protein interactions.\",\n      \"method\": \"X-ray crystallography at 2.0 Å resolution, structural comparison with human ARL6\",\n      \"journal\": \"Protein science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — high-quality structural data but from a trypanosome ortholog; functional validation limited to structural inference\",\n      \"pmids\": [\"23184293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ARL6 localizes at the base of the primary cilium in RH30 rhabdomyosarcoma cells. Knockdown of ARL6 inhibits ciliogenesis and reduces Hedgehog signaling activity, leading to inhibited proliferation and promoted apoptosis of RH30 cells.\",\n      \"method\": \"Immunofluorescence localization, siRNA knockdown, ciliogenesis assay, Hedgehog signaling reporter assay, proliferation and apoptosis assays\",\n      \"journal\": \"Cell & bioscience\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single knockdown study with cellular phenotype but limited mechanistic detail on pathway placement\",\n      \"pmids\": [\"27999656\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"miR-143-3p directly targets the 3'-UTR of ARL6 mRNA (confirmed by luciferase reporter assay). Elevated miR-143-3p reduces ARL6 levels and suppresses Wnt/β-catenin signaling (Wnt3a, β-catenin, LEF1, TCF1), inhibiting osteogenic differentiation of hBMSCs. Overexpression of ARL6 blocks cadmium-induced suppression of the Wnt/β-catenin pathway and rescues osteogenesis.\",\n      \"method\": \"Luciferase reporter assay (miR-143-3p binding to ARL6 3'-UTR), miRNA inhibition, lentiviral ARL6 overexpression, Wnt pathway component expression analysis, osteogenesis assay\",\n      \"journal\": \"Toxicology letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab study; luciferase assay confirms miRNA targeting but functional pathway link relies on overexpression/knockdown without direct mechanistic dissection of ARL6's role in Wnt signaling\",\n      \"pmids\": [\"32522577\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ARL6 (BBS3) is an Arf-like small GTPase that cycles between GDP- and GTP-bound states; GTP-bound ARL6 directly binds the BBS1 subunit (blades 1 and 7 of its β-propeller) to recruit the BBSome coat complex to membranes, enabling ciliary import of the BBSome. At the basal body, IFT22/RABL5 stabilizes ARL6 and, when both are GTP-loaded, delivers the BBSome to IFT-B1 for ciliary entry; once inside cilia, IFT27/RABL4 acts as a guanine nucleotide exchange factor for ARL6 to drive BBSome coat assembly and cargo exit from cilia. Loss of ARL6 disrupts ciliary localization of the BBSome and specific signaling receptors (e.g., MCHR1, Smoothened), impairs retrograde ciliary transport, causes retinal degeneration (with the long eye-specific isoform BBS3L specifically required for cone opsin localization), and also modulates Wnt signaling through a GTP-dependent mechanism; BBS-causing mutations either impair GTP binding, disrupt the ARL6–BBS1 interface, or destabilize the protein leading to proteasomal degradation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ARL6 (BBS3) is an ADP-ribosylation factor-like small GTPase that governs membrane recruitment and ciliary trafficking of the BBSome coat complex, and its loss-of-function causes Bardet-Biedl syndrome [#0, #2]. ARL6 cycles between GDP- and GTP-bound states; only GTP-bound ARL6 binds the BBS1 \\u03b2-propeller (at blades 1 and 7) to recruit the BBSome to membranes, whereas GDP-bound ARL6 cannot, and single point mutations at the ARL6-GTP\\u2013BBS1 interface abolish the interaction and block BBSome import into cilia [#4]. In knockout mice, ARL6 and the BBSome are mutually dependent for ciliary localization, and ARL6 loss disrupts ciliary localization of melanin-concentrating hormone receptor 1 and impairs retrograde transport of Smoothened, without preventing BBSome assembly [#2]. The nucleotide cycle is controlled by two Rab-like GTPases: at the basal body IFT22/RABL5 binds and stabilizes ARL6 and, when both are GTP-loaded, recruits the BBSome for coupling to IFT-B1 and ciliary entry [#6]; inside cilia IFT27/RABL4 binds nucleotide-free ARL6, prevents its aggregation, and promotes its GTP loading to drive BBSome coat assembly and cargo exit [#5]. A vision-specific long isoform, BBS3L, is selectively required for cone opsin localization and photoreceptor function, distinct from the general ciliary transport role of the canonical isoform [#3]. ARL6 additionally modulates Wnt signaling in a GTP-dependent manner abolished by BBS mutations [#1]. BBS-causing mutations act through three mechanisms: impaired GTP binding (e.g., T31R), disruption of the ARL6\\u2013BBS1 interface, or protein destabilization and proteasomal degradation [#4, #7].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established that ARL6 is a disease gene, linking an Arf-like GTPase to ciliopathy for the first time and motivating mechanistic study of its trafficking role.\",\n      \"evidence\": \"Comparative genomics and segregation analysis of a homozygous stop mutation in the BBS3 Bedouin kindred\",\n      \"pmids\": [\"15258860\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular function of ARL6\", \"No mechanism connecting GTPase activity to cilia\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Defined the structural basis of ARL6 nucleotide states and basal body localization, and showed nucleotide-locked variants alter cilium morphology and Wnt signaling, anchoring pathogenesis to nucleotide binding.\",\n      \"evidence\": \"X-ray crystallography of GTP-bound ARL6 with GTP/GDP-locked variant overexpression and Wnt reporter assays\",\n      \"pmids\": [\"20207729\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the direct effector that ARL6-GTP recruits\", \"Wnt mechanism downstream of ARL6 undefined\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Distinguished isoform-specific functions, revealing a vision-dedicated long isoform (BBS3L) required for cone opsin localization separable from general ciliary transport.\",\n      \"evidence\": \"Isoform-specific zebrafish knockdown/RNA rescue and a Bbs3L-null mouse with photoreceptor defects\",\n      \"pmids\": [\"20333246\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of isoform-specific opsin trafficking unresolved\", \"How BBS3L differs biochemically from BBS3 not established\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed ARL6 and the BBSome are mutually dependent for ciliary localization and that ARL6 loss selectively mislocalizes signaling receptors, placing ARL6 as a BBSome trafficking partner rather than an assembly factor.\",\n      \"evidence\": \"Bbs3 knockout mouse with co-IP, ciliary localization, and receptor trafficking readouts (MCHR1, Smoothened)\",\n      \"pmids\": [\"22139371\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve the direct ARL6\\u2013BBSome contact interface\", \"Mechanism of retrograde Smoothened transport defect unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Pinpointed a residue (A89) required specifically for BBS3L vision function but dispensable for syndromic ciliary transport, refining isoform-specific structure-function.\",\n      \"evidence\": \"Zebrafish morpholino knockdown with isoform-specific A89V RNA rescue across visual and transport assays\",\n      \"pmids\": [\"21282186\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab\", \"Biochemical consequence of A89V not characterized\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Resolved the atomic mechanism of BBSome recruitment, showing GTP-bound ARL6 binds the BBS1 \\u03b2-propeller at blades 1 and 7 and that interface mutations (including BBS1 M390R) block ciliary import.\",\n      \"evidence\": \"Crystal structures of ARL6-GDP, ARL6-GTP, and ARL6-GTP\\u2013BBS1 complex from Chlamydomonas with mutagenesis and ciliary import assays\",\n      \"pmids\": [\"25402481\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define how ARL6 is loaded with GTP at membranes\", \"Mammalian validation of the interface relied on ortholog structure\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identified IFT27/RABL4 as a regulator of ARL6, preventing its aggregation and promoting GTP loading to drive BBSome coat assembly and ciliary exit, defining the intraciliary activation step.\",\n      \"evidence\": \"Proteomics, biochemical reconstitution, co-IP, and aggregation assays\",\n      \"pmids\": [\"25443296\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether IFT27 acts as a bona fide GEF not biochemically demonstrated here\", \"GTP hydrolysis step / GAP unidentified\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Established IFT22/RABL5 as a basal-body stabilizer that, when GTP-loaded together with ARL6, recruits the BBSome for IFT-B1 coupling and ciliary entry, completing the entry-versus-exit regulatory logic.\",\n      \"evidence\": \"Chlamydomonas functional assays, co-IP, single-particle in vivo imaging, and GTPase activity assays\",\n      \"pmids\": [\"31953262\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"GEF/GAP that toggles ARL6 nucleotide state at the basal body unidentified\", \"How BBSome is handed off from IFT22 to IFT trains not structurally resolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Provided a biochemical classification of BBS mutations, distinguishing selective GTP-binding loss (T31R) from a shared proteasomal destabilization mechanism.\",\n      \"evidence\": \"In vitro nucleotide-binding assays, mutagenesis, and proteasome inhibitor rescue of mutant expression\",\n      \"pmids\": [\"19236846\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab without independent replication\", \"Degradation pathway components not identified\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrated evolutionary conservation of the ARL6\\u2013BBS1 interaction and a microtubule-anchoring vesicular role in trypanosomes, broadening the functional context.\",\n      \"evidence\": \"RNAi, co-localization, tubulin pulldown, and BBS1 overexpression epistasis in T. brucei\",\n      \"pmids\": [\"22609302\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ortholog context limits direct mammalian inference\", \"Tubulin interaction not validated in mammalian cells\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"First showed GTP-dependent membrane association of ARL6 and a candidate SEC61\\u03b2 interaction, an early clue to nucleotide-regulated membrane behavior predating the ciliary model.\",\n      \"evidence\": \"Yeast two-hybrid screen, co-IP in COS cells, and GTP-\\u03b3S membrane association assay\",\n      \"pmids\": [\"10508919\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of SEC61\\u03b2 interaction never established\", \"Not integrated into the later ciliary trafficking model\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Linked ARL6 to ciliogenesis-dependent Hedgehog signaling and tumor cell survival in a cancer context.\",\n      \"evidence\": \"Immunofluorescence, siRNA knockdown, ciliogenesis, Hedgehog reporter, and proliferation/apoptosis assays in RH30 cells\",\n      \"pmids\": [\"27999656\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single-lab knockdown with limited mechanistic dissection\", \"Pathway placement of ARL6 in Hedgehog signaling unresolved\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Connected ARL6 to miR-143-3p regulation and Wnt/\\u03b2-catenin-dependent osteogenesis, extending its signaling role beyond cilia.\",\n      \"evidence\": \"Luciferase reporter, miRNA inhibition, ARL6 overexpression, and osteogenesis assays in hBMSCs\",\n      \"pmids\": [\"32522577\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Mechanistic link of ARL6 to Wnt relies on overexpression/knockdown without direct dissection\", \"Independent confirmation lacking\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The enzyme(s) that toggle ARL6 between GDP and GTP states at the basal body, and a definitive GAP, remain unidentified, leaving the in vivo nucleotide cycle incompletely closed.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No GAP for ARL6 identified\", \"GEF activity of IFT27 not biochemically proven\", \"How signaling roles (Wnt, Hedgehog) mechanistically depend on ARL6 nucleotide cycling unresolved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0003924\", \"supporting_discovery_ids\": [1, 6, 7]},\n      {\"term_id\": \"GO:0005525\", \"supporting_discovery_ids\": [4, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [2, 12]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [1, 12]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [8]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [8, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [2, 4, 5, 6]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [1, 12]}\n    ],\n    \"complexes\": [\"BBSome\"],\n    \"partners\": [\"BBS1\", \"IFT27\", \"IFT22\", \"SEC61B\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}