{"gene":"KLC1","run_date":"2026-04-28T18:30:27","timeline":{"discoveries":[{"year":2000,"finding":"APP (amyloid precursor protein) is transported axonally by directly binding to the TPR domain of the KLC1 subunit of kinesin-I, with an estimated apparent Kd of 15-20 nM and stoichiometry of two APP per KLC. Axonal transport of APP is greatly decreased in KLC1 gene-targeted mouse mutants, establishing KLC1 as essential for anterograde axonal transport of APP.","method":"Co-immunoprecipitation, sucrose gradient sedimentation, direct in vitro binding assays, KLC1 knockout mouse","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal biochemical methods plus genetic KO validation in vivo","pmids":["11144355"],"is_preprint":false},{"year":2000,"finding":"Sunday driver (SYD/JIP1) directly binds kinesin-I via the tetratricopeptide repeat (TPR) domain of KLC with Kd ~200 nM, mediating kinesin-dependent axonal transport of at least one class of vesicles.","method":"Yeast two-hybrid, in vitro interaction studies, co-immunoprecipitation, GFP localization","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro binding with Kd measurement, co-IP, and functional genetic evidence from Drosophila SYD mutants","pmids":["11106729"],"is_preprint":false},{"year":1993,"finding":"The human KLC1 gene encodes a 569-amino acid polypeptide (64,789 Da) with an N-terminal heptad-repeat rod domain and a central/C-terminal domain of 21-mer (tetratricopeptide) repeats; KLC1 mRNA is expressed in most tissues, and the gene was provisionally assigned to human chromosome 14q.","method":"cDNA cloning, sequencing, bacterial and CHO cell expression, chromosomal assignment","journal":"DNA and cell biology","confidence":"Medium","confidence_rationale":"Tier 2 — original cloning with expression in heterologous systems; structural inference from sequence","pmids":["8274221"],"is_preprint":false},{"year":2012,"finding":"KLC1-ALK is a novel oncogenic fusion kinase identified in lung cancer. The KLC1-ALK fusion cDNA confers transforming potential to mouse 3T3 cells, demonstrating that KLC1 coiled-coil sequences can serve as a dimerization module that constitutively activates the ALK kinase domain.","method":"5'-RACE on FFPE tissue, RT-PCR, FISH confirmation, 3T3 transformation assay","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — functional transformation assay validates oncogenic activity of the fusion","pmids":["22347464"],"is_preprint":false},{"year":2012,"finding":"A 10-amino-acid WD motif in the C-terminal cytoplasmic region of Alcadein-α (Alcα) is necessary and sufficient to interact with part of the KLC1 TPR domain, activating kinesin-1 from its autoinhibited state and driving anterograde vesicular transport. Only a subset of the TPR structure is required for this activation in vivo.","method":"In vivo transport assays with artificial transmembrane proteins carrying WD motifs, excess KLC1 competition, fluorescence correlation spectroscopy (FCS) for protein interaction","journal":"Traffic","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal approaches including domain mutagenesis and rescue experiments in vivo","pmids":["22404616"],"is_preprint":false},{"year":2009,"finding":"AMPK phosphorylates recombinant GST-KLC1 at Ser520 in vitro, but overexpression of phosphomimetic (S517/520D) or non-phosphorylatable (S517/520A) KLC1 mutants does not alter glucose-stimulated insulin granule movement, indicating that AMPK-dependent phosphorylation of KLC1 at these sites does not regulate kinesin-1-mediated granule transport in β-cells.","method":"In vitro AMPK kinase assay with purified proteins, 3D live-cell spinning disc confocal imaging, phospho-specific antibody, KLC1 mutant overexpression in MIN6 cells","journal":"Islets","confidence":"Medium","confidence_rationale":"Tier 1-2 — in vitro phosphorylation confirmed, functional consequence rigorously excluded by multiple mutant approaches","pmids":["21099273"],"is_preprint":false},{"year":2015,"finding":"KLC1 associates with phagosomes carrying photoreceptor outer segment (POS) disk membranes in retinal pigment epithelium (RPE) cells and remains associated during bidirectional movement and pauses. KLC1 knockout decreases phagosome run length and impairs phagosome localization and degradation. In aged KLC1 knockout mice, RPE pathogenesis resembling age-related macular degeneration develops, including sub-RPE deposits, oxidative stress, and inflammatory responses.","method":"Live-cell imaging, KLC1 knockout mouse model, fluorescence microscopy, histopathology","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with defined cellular and organismal phenotypes, replicated with live imaging","pmids":["26261180"],"is_preprint":false},{"year":2016,"finding":"Deletion of KLC1 in mice impairs anterograde Mn2+ transport from the hippocampal CA3 region to the medial septal nuclei as measured by manganese-enhanced MRI, establishing KLC1 as a contributor to kinesin-1-mediated cargo transport in central nervous system circuits, though the effect is moderate.","method":"MEMRI (manganese-enhanced MRI) in KLC1 knockout vs. wild-type mice, histology, statistical parametric mapping","journal":"NeuroImage","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo genetic KO with direct imaging readout, but effect size modest and not fully statistically significant at the main endpoint","pmids":["27751944"],"is_preprint":false},{"year":2017,"finding":"Phosphorylation of KLC1 at Thr466 abolishes the conventional interaction between the KLC1 TPR domain and the C-terminal region of JIP1b, eliminating the enhanced fast velocity (EFV) of APP anterograde transport without impairing the novel JIP1b central-region/KLC1 coiled-coil interaction that drives enhanced high frequency (EHF). Phosphorylation of KLC1 Thr466 increases in aged mouse brains, correlating with decreased JIP1 binding to kinesin-1.","method":"Phosphomimetic/non-phosphorylatable mutagenesis (T466E/T466A), co-immunoprecipitation, live-cell transport velocity analysis, phospho-specific antibody, aged brain analysis","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 — site-specific mutagenesis with functional transport readout and biochemical validation; corroborated in aged brain samples","pmids":["29093025"],"is_preprint":false},{"year":2018,"finding":"Isothermal titration calorimetry identified seven KLC1 TPR residues critical for JIP1 binding and footprinted the JIP1-binding site on KLC1-TPR. The autoinhibitory LFP-acidic motif of KLC1 marginally inhibits JIP1 binding at this same site, and JIP1 and the W-acidic motif of Alcadein-α compete for the same region of KLC1-TPR.","method":"Isothermal titration calorimetry (ITC), truncation and mutagenesis of KLC1 TPR fragments, competition binding experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — quantitative biophysical binding assay with systematic mutagenesis identifying key interacting residues","pmids":["30026235"],"is_preprint":false},{"year":2019,"finding":"DOC2B is phosphorylated on insulin stimulation (at Y301), which enhances its interaction with KLC1 in skeletal muscle. This DOC2B-KLC1 interaction is required for insulin-stimulated GLUT4 translocation to the plasma membrane; Y301 mutation blocks both phosphorylation and KLC1 binding and impairs GLUT4 accumulation, defining a novel KLC1-dependent mechanism for insulin sensitivity.","method":"Co-immunoprecipitation, mass spectrometry, site-directed mutagenesis (Y301), GLUT4-myc surface accumulation assay in L6 myoblasts, transgenic mouse glucose/insulin tolerance tests","journal":"Diabetologia","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP validated by MS, mutagenesis of specific phosphosite, functional readout in vitro and in vivo","pmids":["30707251"],"is_preprint":false},{"year":2019,"finding":"KLC1 suppresses epithelial-mesenchymal transition (EMT), invasion, metastasis, and stem cell marker expression in breast cancer, promoting an epithelial/luminal phenotype. Prolactin enhances KLC1 expression and KIF5B-KLC1 interaction, while TGF-β-mediated pro-invasive activity depends on KIF5B but not KLC1. In triple-negative cells, KIF5B accumulates in the nucleus independently of KLC1 to interact with Snail1.","method":"siRNA knockdown, overexpression, invasion and migration assays, tumor formation assays in multiple breast cancer cell lines, co-immunoprecipitation","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 3 — KD/OE with phenotypic readouts and Co-IP, but pathway placement partially based on expression correlations","pmids":["31204277"],"is_preprint":false},{"year":2021,"finding":"SFPQ-RNA granules interact selectively with a tetrameric kinesin complex containing KLC1 and KIF5A for long-distance axonal transport. The SFPQ-KIF5A/KLC1 interaction is required for axon survival; KIF5A mutations causing Charcot-Marie-Tooth disease impair this binding. Replacing axonally translated SFPQ-bound proteins prevents axon degeneration in CMT models.","method":"Co-immunoprecipitation, selective binding assays, axon survival assays in CMT model neurons, rescue experiments with exogenous proteins","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — selective biochemical interaction established, functional genetic requirement for axon survival demonstrated, disease-relevant mutations tested","pmids":["33284322"],"is_preprint":false},{"year":2014,"finding":"Mitochondrial fission protein Dnm1L (dynamin-1-like protein) interacts with KLC1 via the KLC1 TPR domains, but not with KIF5, as determined by yeast two-hybrid screening; Dnm1L and KLC1 co-localize in cultured cells, suggesting KLC1 may mediate post-fission mitochondrial transport.","method":"Yeast two-hybrid screening, co-localization in cultured cells","journal":"Bioscience, biotechnology, and biochemistry","confidence":"Low","confidence_rationale":"Tier 3 — single yeast two-hybrid plus co-localization; no functional transport assay performed","pmids":["25082190"],"is_preprint":false},{"year":2024,"finding":"CRMP2 directly binds KLC1, and the CRMP2 R565C mutation (corresponding to zebrafish R566C) abolishes this interaction. Knockdown of klc1a in zebrafish causes defective anterior commissure and postoptic commissure formation, genetically interacting with crmp2 knockdown. These findings establish the CRMP2-KLC1 interaction as necessary for axonal elongation and forebrain commissure formation.","method":"Transfected cell co-immunoprecipitation with CRMP2 wild-type vs. R566C mutant, klc1a morpholino knockdown in zebrafish, commissure formation imaging","journal":"Developmental neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP with mutagenesis plus in vivo genetic knockdown with defined developmental phenotype","pmids":["38830696"],"is_preprint":false},{"year":2024,"finding":"CELF1, an RNA-binding protein whose expression is reduced in Alzheimer's disease brains, directly binds KLC1 RNA and suppresses the production of KLC1 splice variant E (KLC1_vE). Reduced CELF1 leads to increased KLC1_vE, which promotes AD pathogenesis, identifying a splicing regulatory axis linking CELF1 to KLC1 alternative splicing.","method":"CLIP-seq database analysis, CELF1 depletion and overexpression in cultured cells, transcriptomic correlation in human AD brain samples","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2-3 — CLIP-seq evidence for direct RNA binding, functional depletion/OE experiments, but mechanistic link to AD phenotype indirect","pmids":["38768546"],"is_preprint":false},{"year":2025,"finding":"KLC1 interacts with dengue virus NS1 protein in mosquito cells (confirmed by proximity ligation assay and co-immunoprecipitation). Silencing KLC1 reduces viral genome synthesis, NS1 secretion, and virus progeny by ~1 log. KLC1 or its function is also required for lipid droplet homeostasis; disruption causes lipid droplets to decrease in number and increase in area, suggesting KLC1-mediated lipid droplet transport is required for dengue virus replication.","method":"Proximity ligation assay, co-immunoprecipitation, transmission immunoelectron microscopy, siRNA silencing, competing peptide interference, lipid droplet imaging","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — multiple orthogonal methods; interaction and functional requirement established, but mechanistic detail of NS1-KLC1 transport role not fully resolved","pmids":["40166163"],"is_preprint":true},{"year":2025,"finding":"Cryo-EM and biophysical analysis of the intact kinesin-1 heterotetramer reveal that in the autoinhibited state, KLC TPR domains are occluded by docking of kinesin heavy chain (KHC) coiled coil 1 (CC1) onto the KLC TPR domain, forming the 'shoulder' observed by EM. Binding of an activating cargo SLiM (short linear peptide motif) to the KLC TPR domain dislocates this shoulder, freeing motor domains and enabling transition from closed/inactive to open/active states and facilitating MAP7 binding. This identifies cargo-mediated TPR shoulder dislocation as the key initial step in kinesin-1 activation.","method":"Cryo-EM of full heterotetrameric kinesin-1, protein design, computational modelling, biophysical binding analysis, negative-stain EM","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structure of holoenzyme combined with biophysical and computational validation of the activation mechanism","pmids":[],"is_preprint":true},{"year":2025,"finding":"An 8.0-Å cryo-EM structure of the autoinhibited kinesin-1 heterotetramer shows that two KLC subunits are asymmetrically arranged and their TPR cargo-binding domains are occluded, providing structural basis for simultaneous inhibition of motor activity and cargo binding. MAP7D3 binding to KHC coiled coils likely competes with intramolecular coiled-coil interactions to unfurl the autoinhibited structure.","method":"Cryo-EM (8.0 Å), structural modeling, functional motor activity assays","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 method but preprint at moderate resolution; functional studies are modeled/inferred rather than directly demonstrated for the KLC activation step","pmids":[],"is_preprint":true},{"year":2025,"finding":"KLC-bound kinesin-1 (KinΔC) on liposomes exhibits partial autoinhibition that reduces microtubule engagement (3-fold lower landing rates vs. constitutively active K543), shortens run lengths, and reduces detachment forces. At 3D microtubule intersections, KinΔC-liposomes preferentially terminate (48%) rather than turn (9%), contrasting with constitutively active motors. The small molecule kinesore, which overcomes KLC-mediated autoinhibition, restores microtubule engagement, confirming that KLC-dependent autoinhibition fine-tunes cargo transport.","method":"Single-molecule TIRF microscopy, in vitro liposome transport assay with 3D microtubule intersections, optical trapping for detachment forces, kinesore pharmacological rescue","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro system with multiple biophysical readouts and pharmacological rescue","pmids":[],"is_preprint":true}],"current_model":"KLC1, the neuronal kinesin light chain subunit of kinesin-1, functions primarily through its tetratricopeptide repeat (TPR) domain, which directly binds short linear peptide motifs (e.g., WD motifs of Alcadein-α, the C-terminal region of JIP1b, APP) on cargo or adaptor proteins, releasing kinesin-1 from its autoinhibited state (in which KHC CC1 occludes the TPR) to drive anterograde microtubule-based transport of vesicles, RNA granules (SFPQ-RNA), and phagosomes; phosphorylation of KLC1 Thr466 modulates JIP1b binding and APP transport velocity, DOC2B phosphorylation at Y301 enables a KLC1-dependent mechanism for GLUT4 translocation to the plasma membrane, CRMP2 binds KLC1 for axonal elongation and forebrain commissure formation, and lack of KLC1 leads to impaired phagosome transport in the RPE causing AMD-like pathology in aged mice."},"narrative":{"teleology":[{"year":1993,"claim":"Establishing the primary structure of human KLC1 revealed its domain architecture—an N-terminal heptad-repeat coiled-coil and a central/C-terminal tetratricopeptide repeat (TPR) region—providing the first framework for understanding how a kinesin light chain might interface with both heavy chains and cargoes.","evidence":"cDNA cloning, sequencing, and heterologous expression in bacteria and CHO cells","pmids":["8274221"],"confidence":"Medium","gaps":["No cargo or heavy-chain binding activity was demonstrated at this stage","Chromosomal assignment was provisional"]},{"year":2000,"claim":"Identification of APP and JIP1/Sunday driver as direct, high-affinity TPR-domain ligands of KLC1 established that the light chain functions as a cargo-recognition subunit required for anterograde axonal transport, resolving how kinesin-1 selects specific vesicle populations.","evidence":"In vitro binding with measured Kd values (~15–20 nM for APP, ~200 nM for JIP1), co-immunoprecipitation, and genetic KO or mutant validation in mouse and Drosophila","pmids":["11144355","11106729"],"confidence":"High","gaps":["The structural basis for how TPR accommodates different cargo motifs was unknown","Mechanism by which cargo binding relieves motor autoinhibition was not addressed"]},{"year":2012,"claim":"Discovery that a 10-residue W-acidic (WD) motif in Alcadein-α binds a subset of the KLC1 TPR domain and is sufficient to activate kinesin-1 from its autoinhibited state demonstrated that short linear motifs are the general currency for KLC1-mediated cargo engagement and motor activation.","evidence":"In vivo transport assays with synthetic transmembrane cargo constructs, competitive KLC1 excess, and fluorescence correlation spectroscopy","pmids":["22404616"],"confidence":"High","gaps":["Structural visualization of the autoinhibited-to-active transition was lacking","Whether all cargo adaptors share the same TPR sub-site was unresolved"]},{"year":2015,"claim":"Demonstrating that KLC1 remains on bidirectionally moving phagosomes and that its knockout impairs phagosome run length, degradation, and RPE homeostasis linked KLC1 function to a non-neuronal cargo (outer-segment phagosomes) and to age-related macular degeneration-like pathology.","evidence":"Live-cell imaging and histopathology in aged KLC1 knockout mice","pmids":["26261180"],"confidence":"High","gaps":["The cargo adaptor bridging phagosomes to KLC1 TPR was not identified","Whether the AMD-like phenotype involves KLC1-independent kinesin functions was not resolved"]},{"year":2017,"claim":"Identification of Thr466 phosphorylation as a switch that specifically abolishes TPR–JIP1 interaction and reduces APP fast transport velocity revealed a post-translational mechanism for tuning kinesin-1 cargo selectivity, with relevance to brain aging.","evidence":"Phosphomimetic/non-phosphorylatable mutagenesis, co-immunoprecipitation, live-cell velocity analysis, and phospho-specific antibody in aged mouse brains","pmids":["29093025"],"confidence":"High","gaps":["The kinase responsible for Thr466 phosphorylation in vivo was not identified","Causal link between age-dependent phosphorylation and neurodegeneration was correlative"]},{"year":2018,"claim":"Isothermal titration calorimetry mapping of the JIP1-binding footprint on the KLC1 TPR domain and demonstration that JIP1 and Alcadein-α W-acidic peptides compete for the same site established a shared, mutually exclusive cargo-binding pocket modulated by an autoinhibitory LFP-acidic motif.","evidence":"ITC with systematic KLC1 TPR truncations and point mutations, competition binding experiments","pmids":["30026235"],"confidence":"High","gaps":["High-resolution co-crystal or cryo-EM structure of the TPR–cargo peptide complex was still unavailable","How the LFP-acidic autoinhibitory segment is regulated in cells was unexplored"]},{"year":2019,"claim":"Two studies expanded KLC1's functional repertoire beyond neuronal transport: DOC2B phosphorylation at Y301 recruits KLC1 to drive insulin-stimulated GLUT4 translocation in skeletal muscle, and KLC1 suppresses epithelial-mesenchymal transition in breast cancer cells, linking kinesin-1 cargo transport to metabolic and oncogenic signaling.","evidence":"Reciprocal co-IP validated by mass spectrometry, Y301 mutagenesis, GLUT4 surface accumulation assay, and transgenic mouse glucose tolerance (DOC2B); siRNA/overexpression with invasion assays (breast cancer)","pmids":["30707251","31204277"],"confidence":"High","gaps":["Whether DOC2B binds the KLC1 TPR domain or a distinct region was not mapped","Molecular mechanism linking KLC1 to epithelial gene expression programs is unclear"]},{"year":2021,"claim":"Selective association of SFPQ-RNA granules with a KIF5A/KLC1 tetrameric complex for long-distance axonal transport, and the impairment of this interaction by CMT-causing KIF5A mutations, established KLC1 as a specificity determinant for RNA granule transport essential for axon survival.","evidence":"Co-immunoprecipitation, selective binding assays, axon survival assays in CMT model neurons with rescue","pmids":["33284322"],"confidence":"High","gaps":["Whether KLC1 directly contacts SFPQ or acts via an intermediate adaptor was not resolved","Structural basis for KIF5A versus KIF5B selectivity in this complex was not determined"]},{"year":2024,"claim":"CRMP2 was identified as a direct KLC1-binding partner whose disease-associated R565C mutation abolishes this interaction, and genetic interaction between klc1a and crmp2 in zebrafish established KLC1-dependent axonal elongation as essential for forebrain commissure formation.","evidence":"Co-immunoprecipitation with WT vs. R566C CRMP2, morpholino knockdown in zebrafish with commissure imaging","pmids":["38830696"],"confidence":"Medium","gaps":["The KLC1 domain mediating CRMP2 binding was not mapped","Whether the commissure defect reflects transport of a specific cargo downstream of CRMP2 is unknown"]},{"year":2025,"claim":"Cryo-EM structures of intact autoinhibited kinesin-1 heterotetramers revealed that KHC coiled-coil 1 (CC1) docks onto the KLC TPR domains to occlude cargo-binding sites, and that cargo SLiM binding to TPR dislocates this 'shoulder' to release motor autoinhibition—providing the first structural mechanism for cargo-coupled kinesin-1 activation.","evidence":"Cryo-EM of holoenzyme (preprint), biophysical binding analysis, single-molecule TIRF reconstitution with kinesore pharmacological rescue (preprint)","pmids":[],"confidence":"High","gaps":["Structures are from preprints and await peer review","Atomic-resolution details of the TPR–CC1 interface and cargo-bound active state are incomplete","How asymmetric KLC arrangement influences cargo stoichiometry in vivo is unknown"]},{"year":null,"claim":"Outstanding questions include the identity of the kinase(s) phosphorylating KLC1 Thr466 in vivo, the structural basis for selective recognition of different cargo SLiMs by the same TPR pocket, and whether KLC1 splice variants (e.g., KLC1_vE implicated in Alzheimer's disease) confer distinct cargo specificities.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution co-structure of KLC1 TPR with any cargo peptide in peer-reviewed literature","Functional distinction among KLC1 splice variants is uncharacterized","In vivo kinase for Thr466 remains unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1,4,9,10,12]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[17,18,19]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[17,18,19]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[0,1,4,6]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[0,1,4,6,12]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[0,1,8,12]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[14]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[10]}],"complexes":["Kinesin-1 heterotetramer (KIF5/KLC)"],"partners":["APP","JIP1","KIF5A","KIF5B","CRMP2","DOC2B","SFPQ","DNM1L"],"other_free_text":[]},"mechanistic_narrative":"KLC1 is the light chain subunit of the kinesin-1 motor complex that couples cargo recognition to motor activation, serving as the principal adaptor for anterograde microtubule-based transport of diverse cargoes including APP-containing vesicles, JIP1-linked vesicles, SFPQ-RNA granules, and phagosomes. Its central tetratricopeptide repeat (TPR) domain directly binds short linear peptide motifs (W-acidic/WD motifs) on cargo adaptors such as Alcadein-α, JIP1, APP, and CRMP2, and this binding displaces the autoinhibitory interaction between the kinesin heavy chain coiled-coil and the KLC TPR domain, thereby activating the motor for processive transport [PMID:11144355, PMID:22404616, PMID:30026235]. Phosphorylation of KLC1 Thr466 selectively disrupts the TPR–JIP1 interaction to reduce APP transport velocity, and phosphorylated DOC2B (Y301) recruits KLC1 to facilitate insulin-stimulated GLUT4 translocation, demonstrating that post-translational modifications tune cargo selectivity and transport dynamics [PMID:29093025, PMID:30707251]. Loss of KLC1 in mice impairs phagosome transport in retinal pigment epithelium, producing age-dependent sub-RPE deposits and pathology resembling age-related macular degeneration, and compromises CRMP2-dependent axonal elongation required for forebrain commissure formation [PMID:26261180, PMID:38830696]."},"prefetch_data":{"uniprot":{"accession":"Q07866","full_name":"Kinesin light chain 1","aliases":[],"length_aa":573,"mass_kda":65.3,"function":"Kinesin is a microtubule-associated force-producing protein that may play a role in organelle transport (PubMed:21385839). The light chain may function in coupling of cargo to the heavy chain or in the modulation of its ATPase activity (By similarity)","subcellular_location":"Cell projection, growth cone; Cytoplasmic vesicle; Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/Q07866/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KLC1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000126214","cell_line_id":"CID001431","localizations":[{"compartment":"centrosome","grade":3},{"compartment":"cytoplasmic","grade":3}],"interactors":[{"gene":"KIF5B","stoichiometry":10.0},{"gene":"KLC4","stoichiometry":10.0},{"gene":"KLC2","stoichiometry":10.0},{"gene":"KIF5A","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001431","total_profiled":1310},"omim":[{"mim_id":"618277","title":"NHL REPEAT-CONTAINING PROTEIN 2; NHLRC2","url":"https://www.omim.org/entry/618277"},{"mim_id":"615759","title":"KINASE D-INTERACTING SUBSTRATE, 220-KD; KIDINS220","url":"https://www.omim.org/entry/615759"},{"mim_id":"615535","title":"SPECTRIN REPEAT-CONTAINING NUCLEAR ENVELOPE PROTEIN 4; SYNE4","url":"https://www.omim.org/entry/615535"},{"mim_id":"611729","title":"KINESIN LIGHT CHAIN 2; KLC2","url":"https://www.omim.org/entry/611729"},{"mim_id":"611321","title":"CALSYNTENIN 1; CLSTN1","url":"https://www.omim.org/entry/611321"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Acrosome","reliability":"Approved"},{"location":"Equatorial segment","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":513.1}],"url":"https://www.proteinatlas.org/search/KLC1"},"hgnc":{"alias_symbol":["KNS2A","KLC","hKLC1S","hKLC1N","hKLC1P","hKLC1G","hKLC1R","hKLC1J","hKLC1B"],"prev_symbol":["KNS2"]},"alphafold":{"accession":"Q07866","domains":[{"cath_id":"-","chopping":"21-151","consensus_level":"high","plddt":92.9097,"start":21,"end":151},{"cath_id":"1.25.40.10","chopping":"396-434_459-513","consensus_level":"medium","plddt":78.0189,"start":396,"end":513}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q07866","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q07866-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q07866-F1-predicted_aligned_error_v6.png","plddt_mean":75.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KLC1","jax_strain_url":"https://www.jax.org/strain/search?query=KLC1"},"sequence":{"accession":"Q07866","fasta_url":"https://rest.uniprot.org/uniprotkb/Q07866.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q07866/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q07866"}},"corpus_meta":[{"pmid":"22347464","id":"PMC_22347464","title":"KLC1-ALK: 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bacteria and CHO cells and provisionally mapped to human chromosome 14.\",\n      \"method\": \"cDNA cloning, sequence analysis, bacterial/CHO expression, chromosomal mapping\",\n      \"journal\": \"DNA and cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct molecular characterization of the protein structure and gene, single lab\",\n      \"pmids\": [\"8274221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The KLC1 TPR region mediates kinesin-1 cargo binding and activation: a 10-amino-acid WD motif in the cargo protein Alcadein-α (or an 11-amino-acid C-terminal region of JIP1) is sufficient to interact with part of the KLC1 TPR domain and initiate kinesin-1 vesicular association and anterograde transport in vivo.\",\n      \"method\": \"In vivo transport assays with artificial transmembrane constructs, excess KLC1 competition, truncation and mutagenesis of TPR domain\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal in vivo assays with mutagenesis and domain dissection, replicated with two distinct cargo peptides\",\n      \"pmids\": [\"22404616\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"AMPK phosphorylates KLC1 at Ser520 in vitro, but phosphomimetic (S517/520D) and non-phosphorylatable (S517/520A) KLC1 mutants showed no difference from wild-type in glucose-stimulated insulin granule movement in MIN6 beta-cells, indicating that AMPK-dependent phosphorylation of KLC1 at these sites does not regulate kinesin-1-mediated granule transport.\",\n      \"method\": \"In vitro AMPK kinase assay with recombinant GST-KLC1, site-directed mutagenesis, live-cell 3D spinning disc confocal microscopy of insulin granule dynamics\",\n      \"journal\": \"Islets\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro kinase assay plus functional mutagenesis with live imaging, confirmed in follow-up paper (PMID:20074060)\",\n      \"pmids\": [\"21099273\", \"20074060\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"KLC1 associates with photoreceptor outer segment (POS) phagosomes in RPE cells and remains associated during bidirectional microtubule-based movement and pauses; loss of KLC1 decreases phagosome run length and impairs phagosome localization and degradation, leading to AMD-like RPE pathogenesis in aged mice.\",\n      \"method\": \"Live-cell imaging of KLC1-labeled phagosomes, KLC1 knockout mouse model, fractionation/localization, quantification of run length and speed\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct live imaging plus KO mouse with defined cellular and organismal phenotypes, multiple readouts\",\n      \"pmids\": [\"26261180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"KLC1 deletion impairs anterograde Mn2+ transport along the hippocampal-forebrain circuit in vivo, as measured by manganese-enhanced MRI, indicating that kinesin-1/KLC1 contributes to central nervous system axonal transport.\",\n      \"method\": \"KLC1 knockout mice, manganese-enhanced MRI (MEMRI) in vivo, statistical parametric mapping, histological tract tracing\",\n      \"journal\": \"NeuroImage\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO with defined in vivo transport readout, single lab\",\n      \"pmids\": [\"27751944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Phosphorylation of KLC1 at Thr466 abolishes interaction with the C-terminal region of JIP1b and eliminates the enhanced fast velocity (EFV) of APP anterograde transport, without affecting the JIP1b central region–KLC1 coiled-coil interaction responsible for enhanced high frequency transport; KLC1 Thr466 phosphorylation increases in aged brains.\",\n      \"method\": \"Site-directed mutagenesis (T466E phosphomimetic), co-immunoprecipitation, live-cell transport imaging, phosphorylation analysis in aged mouse brain\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — mutagenesis with functional transport assay plus co-IP, multiple mechanistic readouts in single study\",\n      \"pmids\": [\"29093025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The KLC1 TPR domain directly binds JIP1 via a defined footprint of seven critical KLC1 residues; the autoinhibitory LFP-acidic motif of KLC1 marginally inhibits JIP1 binding, and JIP1 and the W-acidic motif of alcadein-α compete for overlapping sites on KLC1-TPR.\",\n      \"method\": \"Isothermal titration calorimetry (ITC) with truncated KLC1-TPR fragments and mutagenesis, structural footprinting validated against existing crystal structure\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — quantitative biophysical binding assay with systematic mutagenesis and structural validation\",\n      \"pmids\": [\"30026235\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"DOC2B is phosphorylated at Y301 upon insulin stimulation, enhancing its interaction with KLC1; mutation of Y301 blocks this phosphorylation and the DOC2B–KLC1 interaction, and blunts insulin-stimulated GLUT4 accumulation at the plasma membrane in skeletal muscle cells.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, site-directed mutagenesis (Y301), GLUT4-myc accumulation assay, transgenic mouse glucose/insulin tolerance tests\",\n      \"journal\": \"Diabetologia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP and MS with mutagenesis, validated in vivo and in vitro with multiple functional readouts\",\n      \"pmids\": [\"30707251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"KLC1 (but not KIF5B) suppresses epithelial-mesenchymal transition, invasion, and stem cell marker expression in breast cancer cells, and KIF5B–KLC1 interaction (promoted by prolactin) supports the epithelial/luminal phenotype, while nuclear KIF5B–Snail1 interaction (independent of KLC1) drives EMT.\",\n      \"method\": \"KD/OE in multiple breast cancer cell lines, EMT marker analysis, invasion assays, co-immunoprecipitation of KIF5B–KLC1 and KIF5B–Snail1\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — co-IP plus functional KD/OE with phenotypic readouts, single lab\",\n      \"pmids\": [\"31204277\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SFPQ-RNA granules selectively interact with a tetrameric kinesin complex containing KLC1 and KIF5A; this KLC1–KIF5A-mediated transport of SFPQ granules is required for axon survival, and KIF5A CMT-disease mutations impair binding to the KLC1/KIF5A complex.\",\n      \"method\": \"Co-immunoprecipitation of SFPQ with KLC1/KIF5A, dominant-negative disruption, axon degeneration assays, CMT mutant analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP, loss-of-function with defined neuronal survival phenotype, disease-relevant mutagenesis\",\n      \"pmids\": [\"33284322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Dynamin-1-like protein (Dnm1L/DRP1) interacts with KLC1 through the KLC1 TPR domains (not with KIF5 heavy chain), and the two proteins co-localize in cultured cells, suggesting a role for KLC1 in post-fission mitochondrial transport.\",\n      \"method\": \"Yeast two-hybrid screening, co-localization in cultured cells\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — yeast two-hybrid plus co-localization only, single lab, no functional validation\",\n      \"pmids\": [\"25082190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CELF1 directly binds KLC1 mRNA and down-regulates the KLC1 splice variant E (KLC1_vE); reduced CELF1 expression in AD brains is associated with increased KLC1_vE, placing CELF1 upstream of KLC1 alternative splicing in AD pathogenesis.\",\n      \"method\": \"CLIP-seq, siRNA depletion and overexpression in cultured cells, transcriptomic correlation in human brain samples\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — CLIP-seq plus depletion/OE experiments with splicing readout, single lab\",\n      \"pmids\": [\"38768546\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"KLC1 binding to CRMP2 is required for axon elongation and forebrain commissure formation: the CRMP2 R565C mutation abolishes binding to KLC1, and klc1a knockdown in zebrafish phenocopies crmp2 knockdown with defective anterior and postoptic commissure formation.\",\n      \"method\": \"Co-immunoprecipitation in transfected cells, morpholino knockdown of klc1a in zebrafish, genetic interaction (double knockdown epistasis), rescue experiments with wild-type and mutant crmp2 mRNA\",\n      \"journal\": \"Developmental neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP plus in vivo genetic epistasis with zebrafish KD and mRNA rescue, single lab\",\n      \"pmids\": [\"38830696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Binding of activating short linear peptide motifs (SLiMs) to the KLC1 TPR domain dislocates the TPR 'shoulder' from the kinesin heavy chain coiled-coil 1 (CC1), freeing motor domains and promoting transition from closed autoinhibited to open active conformation; MAP7 binding is facilitated only after this TPR shoulder dislocation.\",\n      \"method\": \"Protein design, computational modelling, biophysical analysis (SEC, AUC), negative-stain electron microscopy of full heterotetrameric holoenzyme\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 — structural EM plus biophysical assays and mutagenesis, preprint not yet peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structure of the kinesin-1 heterotetramer at 8.0 Å reveals that the KLC TPR cargo-binding domains are occluded in the autoinhibited conformation through asymmetric KLC positioning stabilized by intramolecular and intermolecular KHC–KLC interactions, providing a structural basis for simultaneous inhibition of motor activity and cargo binding.\",\n      \"method\": \"Cryo-electron microscopy (8.0 Å), structural modelling, functional motility assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure with functional validation, preprint not yet peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"KLC-bound kinesin-1 (KinΔC) on liposomes exhibits partial autoinhibition that reduces microtubule engagement, run lengths, and detachment forces compared with constitutively active kinesin, and the small molecule kinesore (which overcomes autoinhibition) restores microtubule engagement; this autoinhibition tunes directional outcomes at 3D microtubule intersections.\",\n      \"method\": \"In vitro liposome transport assays, single-molecule imaging, optical trap force measurements, kinesore pharmacological rescue\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro system with multiple quantitative assays and pharmacological validation, preprint\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"KLC1 is the cargo-adaptor subunit of kinesin-1 whose tetratricopeptide repeat (TPR) domain directly binds short linear peptide motifs on diverse cargo proteins (including JIP1, alcadein-α, SFPQ, CRMP2, DOC2B) to recruit and activate the kinesin-1 heterotetramer from its autoinhibited, closed conformation—in which the KLC TPR domains are occluded by the heavy-chain coiled-coil—thereby licensing anterograde microtubule-based transport of vesicles, RNA granules, and organelles in neurons, RPE cells, and other cell types; phosphorylation of KLC1 (e.g., at Thr466) modulates specific cargo interactions and transport velocity, and KLC1 loss impairs phagosome degradation, axon survival, and GLUT4-mediated insulin signaling.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"APP (amyloid precursor protein) is transported axonally by directly binding to the TPR domain of the KLC1 subunit of kinesin-I, with an estimated apparent Kd of 15-20 nM and stoichiometry of two APP per KLC. Axonal transport of APP is greatly decreased in KLC1 gene-targeted mouse mutants, establishing KLC1 as essential for anterograde axonal transport of APP.\",\n      \"method\": \"Co-immunoprecipitation, sucrose gradient sedimentation, direct in vitro binding assays, KLC1 knockout mouse\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal biochemical methods plus genetic KO validation in vivo\",\n      \"pmids\": [\"11144355\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Sunday driver (SYD/JIP1) directly binds kinesin-I via the tetratricopeptide repeat (TPR) domain of KLC with Kd ~200 nM, mediating kinesin-dependent axonal transport of at least one class of vesicles.\",\n      \"method\": \"Yeast two-hybrid, in vitro interaction studies, co-immunoprecipitation, GFP localization\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro binding with Kd measurement, co-IP, and functional genetic evidence from Drosophila SYD mutants\",\n      \"pmids\": [\"11106729\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"The human KLC1 gene encodes a 569-amino acid polypeptide (64,789 Da) with an N-terminal heptad-repeat rod domain and a central/C-terminal domain of 21-mer (tetratricopeptide) repeats; KLC1 mRNA is expressed in most tissues, and the gene was provisionally assigned to human chromosome 14q.\",\n      \"method\": \"cDNA cloning, sequencing, bacterial and CHO cell expression, chromosomal assignment\",\n      \"journal\": \"DNA and cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — original cloning with expression in heterologous systems; structural inference from sequence\",\n      \"pmids\": [\"8274221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"KLC1-ALK is a novel oncogenic fusion kinase identified in lung cancer. The KLC1-ALK fusion cDNA confers transforming potential to mouse 3T3 cells, demonstrating that KLC1 coiled-coil sequences can serve as a dimerization module that constitutively activates the ALK kinase domain.\",\n      \"method\": \"5'-RACE on FFPE tissue, RT-PCR, FISH confirmation, 3T3 transformation assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional transformation assay validates oncogenic activity of the fusion\",\n      \"pmids\": [\"22347464\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A 10-amino-acid WD motif in the C-terminal cytoplasmic region of Alcadein-α (Alcα) is necessary and sufficient to interact with part of the KLC1 TPR domain, activating kinesin-1 from its autoinhibited state and driving anterograde vesicular transport. Only a subset of the TPR structure is required for this activation in vivo.\",\n      \"method\": \"In vivo transport assays with artificial transmembrane proteins carrying WD motifs, excess KLC1 competition, fluorescence correlation spectroscopy (FCS) for protein interaction\",\n      \"journal\": \"Traffic\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal approaches including domain mutagenesis and rescue experiments in vivo\",\n      \"pmids\": [\"22404616\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"AMPK phosphorylates recombinant GST-KLC1 at Ser520 in vitro, but overexpression of phosphomimetic (S517/520D) or non-phosphorylatable (S517/520A) KLC1 mutants does not alter glucose-stimulated insulin granule movement, indicating that AMPK-dependent phosphorylation of KLC1 at these sites does not regulate kinesin-1-mediated granule transport in β-cells.\",\n      \"method\": \"In vitro AMPK kinase assay with purified proteins, 3D live-cell spinning disc confocal imaging, phospho-specific antibody, KLC1 mutant overexpression in MIN6 cells\",\n      \"journal\": \"Islets\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro phosphorylation confirmed, functional consequence rigorously excluded by multiple mutant approaches\",\n      \"pmids\": [\"21099273\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"KLC1 associates with phagosomes carrying photoreceptor outer segment (POS) disk membranes in retinal pigment epithelium (RPE) cells and remains associated during bidirectional movement and pauses. KLC1 knockout decreases phagosome run length and impairs phagosome localization and degradation. In aged KLC1 knockout mice, RPE pathogenesis resembling age-related macular degeneration develops, including sub-RPE deposits, oxidative stress, and inflammatory responses.\",\n      \"method\": \"Live-cell imaging, KLC1 knockout mouse model, fluorescence microscopy, histopathology\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined cellular and organismal phenotypes, replicated with live imaging\",\n      \"pmids\": [\"26261180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Deletion of KLC1 in mice impairs anterograde Mn2+ transport from the hippocampal CA3 region to the medial septal nuclei as measured by manganese-enhanced MRI, establishing KLC1 as a contributor to kinesin-1-mediated cargo transport in central nervous system circuits, though the effect is moderate.\",\n      \"method\": \"MEMRI (manganese-enhanced MRI) in KLC1 knockout vs. wild-type mice, histology, statistical parametric mapping\",\n      \"journal\": \"NeuroImage\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo genetic KO with direct imaging readout, but effect size modest and not fully statistically significant at the main endpoint\",\n      \"pmids\": [\"27751944\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Phosphorylation of KLC1 at Thr466 abolishes the conventional interaction between the KLC1 TPR domain and the C-terminal region of JIP1b, eliminating the enhanced fast velocity (EFV) of APP anterograde transport without impairing the novel JIP1b central-region/KLC1 coiled-coil interaction that drives enhanced high frequency (EHF). Phosphorylation of KLC1 Thr466 increases in aged mouse brains, correlating with decreased JIP1 binding to kinesin-1.\",\n      \"method\": \"Phosphomimetic/non-phosphorylatable mutagenesis (T466E/T466A), co-immunoprecipitation, live-cell transport velocity analysis, phospho-specific antibody, aged brain analysis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — site-specific mutagenesis with functional transport readout and biochemical validation; corroborated in aged brain samples\",\n      \"pmids\": [\"29093025\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Isothermal titration calorimetry identified seven KLC1 TPR residues critical for JIP1 binding and footprinted the JIP1-binding site on KLC1-TPR. The autoinhibitory LFP-acidic motif of KLC1 marginally inhibits JIP1 binding at this same site, and JIP1 and the W-acidic motif of Alcadein-α compete for the same region of KLC1-TPR.\",\n      \"method\": \"Isothermal titration calorimetry (ITC), truncation and mutagenesis of KLC1 TPR fragments, competition binding experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — quantitative biophysical binding assay with systematic mutagenesis identifying key interacting residues\",\n      \"pmids\": [\"30026235\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"DOC2B is phosphorylated on insulin stimulation (at Y301), which enhances its interaction with KLC1 in skeletal muscle. This DOC2B-KLC1 interaction is required for insulin-stimulated GLUT4 translocation to the plasma membrane; Y301 mutation blocks both phosphorylation and KLC1 binding and impairs GLUT4 accumulation, defining a novel KLC1-dependent mechanism for insulin sensitivity.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, site-directed mutagenesis (Y301), GLUT4-myc surface accumulation assay in L6 myoblasts, transgenic mouse glucose/insulin tolerance tests\",\n      \"journal\": \"Diabetologia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP validated by MS, mutagenesis of specific phosphosite, functional readout in vitro and in vivo\",\n      \"pmids\": [\"30707251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"KLC1 suppresses epithelial-mesenchymal transition (EMT), invasion, metastasis, and stem cell marker expression in breast cancer, promoting an epithelial/luminal phenotype. Prolactin enhances KLC1 expression and KIF5B-KLC1 interaction, while TGF-β-mediated pro-invasive activity depends on KIF5B but not KLC1. In triple-negative cells, KIF5B accumulates in the nucleus independently of KLC1 to interact with Snail1.\",\n      \"method\": \"siRNA knockdown, overexpression, invasion and migration assays, tumor formation assays in multiple breast cancer cell lines, co-immunoprecipitation\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — KD/OE with phenotypic readouts and Co-IP, but pathway placement partially based on expression correlations\",\n      \"pmids\": [\"31204277\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SFPQ-RNA granules interact selectively with a tetrameric kinesin complex containing KLC1 and KIF5A for long-distance axonal transport. The SFPQ-KIF5A/KLC1 interaction is required for axon survival; KIF5A mutations causing Charcot-Marie-Tooth disease impair this binding. Replacing axonally translated SFPQ-bound proteins prevents axon degeneration in CMT models.\",\n      \"method\": \"Co-immunoprecipitation, selective binding assays, axon survival assays in CMT model neurons, rescue experiments with exogenous proteins\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — selective biochemical interaction established, functional genetic requirement for axon survival demonstrated, disease-relevant mutations tested\",\n      \"pmids\": [\"33284322\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Mitochondrial fission protein Dnm1L (dynamin-1-like protein) interacts with KLC1 via the KLC1 TPR domains, but not with KIF5, as determined by yeast two-hybrid screening; Dnm1L and KLC1 co-localize in cultured cells, suggesting KLC1 may mediate post-fission mitochondrial transport.\",\n      \"method\": \"Yeast two-hybrid screening, co-localization in cultured cells\",\n      \"journal\": \"Bioscience, biotechnology, and biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single yeast two-hybrid plus co-localization; no functional transport assay performed\",\n      \"pmids\": [\"25082190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CRMP2 directly binds KLC1, and the CRMP2 R565C mutation (corresponding to zebrafish R566C) abolishes this interaction. Knockdown of klc1a in zebrafish causes defective anterior commissure and postoptic commissure formation, genetically interacting with crmp2 knockdown. These findings establish the CRMP2-KLC1 interaction as necessary for axonal elongation and forebrain commissure formation.\",\n      \"method\": \"Transfected cell co-immunoprecipitation with CRMP2 wild-type vs. R566C mutant, klc1a morpholino knockdown in zebrafish, commissure formation imaging\",\n      \"journal\": \"Developmental neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP with mutagenesis plus in vivo genetic knockdown with defined developmental phenotype\",\n      \"pmids\": [\"38830696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CELF1, an RNA-binding protein whose expression is reduced in Alzheimer's disease brains, directly binds KLC1 RNA and suppresses the production of KLC1 splice variant E (KLC1_vE). Reduced CELF1 leads to increased KLC1_vE, which promotes AD pathogenesis, identifying a splicing regulatory axis linking CELF1 to KLC1 alternative splicing.\",\n      \"method\": \"CLIP-seq database analysis, CELF1 depletion and overexpression in cultured cells, transcriptomic correlation in human AD brain samples\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — CLIP-seq evidence for direct RNA binding, functional depletion/OE experiments, but mechanistic link to AD phenotype indirect\",\n      \"pmids\": [\"38768546\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"KLC1 interacts with dengue virus NS1 protein in mosquito cells (confirmed by proximity ligation assay and co-immunoprecipitation). Silencing KLC1 reduces viral genome synthesis, NS1 secretion, and virus progeny by ~1 log. KLC1 or its function is also required for lipid droplet homeostasis; disruption causes lipid droplets to decrease in number and increase in area, suggesting KLC1-mediated lipid droplet transport is required for dengue virus replication.\",\n      \"method\": \"Proximity ligation assay, co-immunoprecipitation, transmission immunoelectron microscopy, siRNA silencing, competing peptide interference, lipid droplet imaging\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods; interaction and functional requirement established, but mechanistic detail of NS1-KLC1 transport role not fully resolved\",\n      \"pmids\": [\"40166163\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM and biophysical analysis of the intact kinesin-1 heterotetramer reveal that in the autoinhibited state, KLC TPR domains are occluded by docking of kinesin heavy chain (KHC) coiled coil 1 (CC1) onto the KLC TPR domain, forming the 'shoulder' observed by EM. Binding of an activating cargo SLiM (short linear peptide motif) to the KLC TPR domain dislocates this shoulder, freeing motor domains and enabling transition from closed/inactive to open/active states and facilitating MAP7 binding. This identifies cargo-mediated TPR shoulder dislocation as the key initial step in kinesin-1 activation.\",\n      \"method\": \"Cryo-EM of full heterotetrameric kinesin-1, protein design, computational modelling, biophysical binding analysis, negative-stain EM\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structure of holoenzyme combined with biophysical and computational validation of the activation mechanism\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"An 8.0-Å cryo-EM structure of the autoinhibited kinesin-1 heterotetramer shows that two KLC subunits are asymmetrically arranged and their TPR cargo-binding domains are occluded, providing structural basis for simultaneous inhibition of motor activity and cargo binding. MAP7D3 binding to KHC coiled coils likely competes with intramolecular coiled-coil interactions to unfurl the autoinhibited structure.\",\n      \"method\": \"Cryo-EM (8.0 Å), structural modeling, functional motor activity assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 method but preprint at moderate resolution; functional studies are modeled/inferred rather than directly demonstrated for the KLC activation step\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"KLC-bound kinesin-1 (KinΔC) on liposomes exhibits partial autoinhibition that reduces microtubule engagement (3-fold lower landing rates vs. constitutively active K543), shortens run lengths, and reduces detachment forces. At 3D microtubule intersections, KinΔC-liposomes preferentially terminate (48%) rather than turn (9%), contrasting with constitutively active motors. The small molecule kinesore, which overcomes KLC-mediated autoinhibition, restores microtubule engagement, confirming that KLC-dependent autoinhibition fine-tunes cargo transport.\",\n      \"method\": \"Single-molecule TIRF microscopy, in vitro liposome transport assay with 3D microtubule intersections, optical trapping for detachment forces, kinesore pharmacological rescue\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro system with multiple biophysical readouts and pharmacological rescue\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"KLC1, the neuronal kinesin light chain subunit of kinesin-1, functions primarily through its tetratricopeptide repeat (TPR) domain, which directly binds short linear peptide motifs (e.g., WD motifs of Alcadein-α, the C-terminal region of JIP1b, APP) on cargo or adaptor proteins, releasing kinesin-1 from its autoinhibited state (in which KHC CC1 occludes the TPR) to drive anterograde microtubule-based transport of vesicles, RNA granules (SFPQ-RNA), and phagosomes; phosphorylation of KLC1 Thr466 modulates JIP1b binding and APP transport velocity, DOC2B phosphorylation at Y301 enables a KLC1-dependent mechanism for GLUT4 translocation to the plasma membrane, CRMP2 binds KLC1 for axonal elongation and forebrain commissure formation, and lack of KLC1 leads to impaired phagosome transport in the RPE causing AMD-like pathology in aged mice.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KLC1 is the cargo-adaptor light chain subunit of the kinesin-1 heterotetramer that couples diverse cargo recognition to motor activation for anterograde microtubule-based transport. Its tetratricopeptide repeat (TPR) domain directly binds short linear peptide motifs on cargo proteins—including JIP1, alcadein-α, SFPQ, CRMP2, and DOC2B—with JIP1 and alcadein-α competing for overlapping TPR binding sites, and cargo engagement displaces the TPR domain from the heavy-chain coiled-coil to relieve autoinhibition and license processive motility [PMID:22404616, PMID:30026235]. Phosphorylation of KLC1 at Thr466 selectively abolishes the JIP1 C-terminal interaction required for enhanced fast velocity of APP transport and increases with brain aging, while insulin-stimulated phosphorylation of the cargo DOC2B at Y301 promotes DOC2B–KLC1 binding and GLUT4 plasma membrane accumulation [PMID:29093025, PMID:30707251]. KLC1 loss impairs phagosome transport and degradation in RPE cells causing age-related pathology, disrupts axonal transport in hippocampal circuits, and—through its selective partnership with KIF5A—is required for SFPQ-RNA granule transport essential for axon survival [PMID:26261180, PMID:27751944, PMID:33284322]. KLC1 binding to CRMP2 is required for axon elongation and forebrain commissure formation, and KIF5A mutations linked to Charcot-Marie-Tooth disease impair assembly of the KLC1/KIF5A transport complex [PMID:38830696, PMID:33284322].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Establishing the primary structure of KLC1 revealed the heptad-repeat and tandem 21-mer repeat architecture that would later be recognized as coiled-coil and TPR domains, respectively, providing the molecular framework for understanding cargo binding and heavy-chain association.\",\n      \"evidence\": \"cDNA cloning, sequence analysis, heterologous expression in bacteria and CHO cells, chromosomal mapping to human chromosome 14\",\n      \"pmids\": [\"8274221\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional assays for transport or cargo binding were performed\", \"Domain boundaries of the TPR region not yet defined\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrating that short peptide motifs (W-acidic in alcadein-α, C-terminal JIP1 region) are sufficient to bind the KLC1 TPR domain and initiate kinesin-1 vesicular association answered how cargo recognition by KLC1 activates the motor for anterograde transport in vivo.\",\n      \"evidence\": \"In vivo transport assays with artificial transmembrane constructs, excess KLC1 competition, TPR truncation and mutagenesis with two distinct cargo peptides\",\n      \"pmids\": [\"22404616\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for cargo-induced activation not yet resolved\", \"Selectivity determinants among different cargo motifs unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of Dnm1L/DRP1 as a KLC1-TPR interactor raised the possibility that KLC1 participates in post-fission mitochondrial transport, but this interaction lacked functional validation.\",\n      \"evidence\": \"Yeast two-hybrid screen followed by co-localization in cultured cells\",\n      \"pmids\": [\"25082190\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No functional transport or mitochondrial phenotype demonstrated\", \"Interaction not confirmed by reciprocal co-IP or in vitro binding\", \"Single lab, single method\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Showing that KLC1 associates with phagosomes and that KLC1 knockout impairs phagosome run length, localization, and degradation in RPE cells established KLC1 as essential for non-neuronal organelle transport with direct disease relevance to age-related macular degeneration-like pathology.\",\n      \"evidence\": \"Live-cell imaging of KLC1-labeled phagosomes, KLC1 knockout mouse with quantified phagosome dynamics and RPE pathology in aged animals\",\n      \"pmids\": [\"26261180\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the phagosome-localized cargo adaptor linking KLC1 to the phagosome membrane unknown\", \"Whether KLC1 role is direct or via an intermediate adaptor not resolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"In vivo manganese-enhanced MRI in KLC1 knockout mice demonstrated impaired anterograde axonal transport in hippocampal-forebrain circuits, extending KLC1 function from cultured cells to intact CNS circuits.\",\n      \"evidence\": \"KLC1 knockout mice with manganese-enhanced MRI and statistical parametric mapping\",\n      \"pmids\": [\"27751944\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specific cargoes affected in vivo not identified\", \"Compensatory roles of KLC2 not assessed\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Phosphorylation of KLC1 at Thr466 was shown to selectively disrupt the JIP1b C-terminal interaction and abolish enhanced fast velocity of APP transport without affecting other JIP1b–KLC1 contacts, revealing a phospho-switch that tunes cargo-specific transport parameters and increases with brain aging.\",\n      \"evidence\": \"T466E phosphomimetic mutagenesis, co-immunoprecipitation, live-cell APP transport imaging, phosphorylation quantification in aged mouse brain\",\n      \"pmids\": [\"29093025\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Kinase responsible for Thr466 phosphorylation in vivo not identified\", \"Causal relationship between age-dependent phosphorylation and neurodegeneration not established\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Quantitative biophysical mapping of the KLC1-TPR footprint for JIP1 binding defined seven critical residues and showed that the autoinhibitory LFP-acidic motif marginally inhibits JIP1 binding, while JIP1 and alcadein-α W-acidic motifs compete for overlapping TPR sites, establishing the molecular logic of cargo selectivity and autoinhibition relief.\",\n      \"evidence\": \"Isothermal titration calorimetry with systematically truncated and mutated KLC1-TPR fragments, validated against crystal structure data\",\n      \"pmids\": [\"30026235\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full atomic structure of KLC1-TPR bound to JIP1 not determined\", \"How multiple cargoes are prioritized in a physiological context unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Two parallel advances extended KLC1's functional repertoire: DOC2B phosphorylation at Y301 upon insulin stimulation was shown to promote DOC2B–KLC1 interaction required for GLUT4 plasma membrane accumulation, and KLC1 was found to suppress epithelial-mesenchymal transition in breast cancer cells through its interaction with KIF5B.\",\n      \"evidence\": \"Reciprocal co-IP and mass spectrometry with Y301 mutagenesis plus GLUT4-myc assay and in vivo glucose tolerance tests (DOC2B); KD/OE with EMT marker analysis and invasion assays (breast cancer)\",\n      \"pmids\": [\"30707251\", \"31204277\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The cargo transported by KLC1-kinesin-1 that maintains epithelial phenotype is unidentified\", \"Whether DOC2B–KLC1 interaction is direct or via an adaptor not resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Selective assembly of SFPQ-RNA granules with a KLC1/KIF5A-containing kinesin-1 complex, and the requirement of this transport for axon survival, established cargo-specific light chain–heavy chain pairing as a mechanism for neuronal transport specificity; KIF5A CMT-disease mutations impaired this complex.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation of SFPQ with KLC1/KIF5A, dominant-negative disruption, axon degeneration assays, CMT mutant analysis\",\n      \"pmids\": [\"33284322\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether KLC1 directly contacts SFPQ or acts through an adaptor unknown\", \"Structural basis for KIF5A selectivity over KIF5B/C in this complex not determined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Two studies expanded KLC1's developmental and disease roles: CRMP2 binding to KLC1 was shown to be required for axon elongation and forebrain commissure formation, and CELF1 was identified as a regulator of KLC1 alternative splicing with relevance to Alzheimer's disease.\",\n      \"evidence\": \"Co-IP and zebrafish morpholino knockdown with genetic epistasis and mRNA rescue (CRMP2); CLIP-seq and siRNA experiments with transcriptomic correlation in human AD brain (CELF1)\",\n      \"pmids\": [\"38830696\", \"38768546\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequences of individual KLC1 splice variants on transport specificity not defined\", \"Whether CRMP2–KLC1 interaction is direct or bridged in vivo not fully established\", \"Causal role of KLC1 splicing changes in AD pathogenesis not demonstrated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Structural and biophysical studies revealed the autoinhibited conformation of the kinesin-1 heterotetramer: cryo-EM showed that KLC TPR domains are asymmetrically occluded by heavy-chain interactions, and cargo SLiM binding dislocates the TPR 'shoulder' from the coiled-coil to relieve autoinhibition, with partial autoinhibition on liposomes tuning transport parameters at microtubule intersections.\",\n      \"evidence\": \"Cryo-EM at 8.0 Å, negative-stain EM, SEC/AUC biophysics, protein design and computational modeling, reconstituted liposome transport with single-molecule imaging and optical trapping (all preprints)\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"All three studies are preprints awaiting peer review\", \"High-resolution structure of cargo-bound activated state not yet available\", \"In vivo validation of the TPR-shoulder dislocation mechanism not performed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: the identity of the kinase(s) phosphorylating KLC1 Thr466 in aging brain, the structural basis for how individual cargo SLiMs differentially activate the holoenzyme, whether KLC1 and KLC2 have non-redundant cargo specificity in vivo, and the functional significance of individual KLC1 splice variants in neuronal versus non-neuronal contexts.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No high-resolution co-crystal structure of KLC1-TPR with any full-length cargo\", \"KLC1 vs KLC2 cargo partitioning not systematically addressed\", \"Contribution of individual splice variants to specific transport pathways undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [1, 6, 10, 12]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 7, 9, 12]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 14]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1, 3, 15]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 6]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [1, 3, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [1, 3, 9]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [4, 5, 9]}\n    ],\n    \"complexes\": [\n      \"Kinesin-1 heterotetramer (KIF5/KLC)\"\n    ],\n    \"partners\": [\n      \"KIF5A\",\n      \"KIF5B\",\n      \"JIP1\",\n      \"ALCAM\",\n      \"SFPQ\",\n      \"CRMP2\",\n      \"DOC2B\",\n      \"DNM1L\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"KLC1 is the light chain subunit of the kinesin-1 motor complex that couples cargo recognition to motor activation, serving as the principal adaptor for anterograde microtubule-based transport of diverse cargoes including APP-containing vesicles, JIP1-linked vesicles, SFPQ-RNA granules, and phagosomes. Its central tetratricopeptide repeat (TPR) domain directly binds short linear peptide motifs (W-acidic/WD motifs) on cargo adaptors such as Alcadein-α, JIP1, APP, and CRMP2, and this binding displaces the autoinhibitory interaction between the kinesin heavy chain coiled-coil and the KLC TPR domain, thereby activating the motor for processive transport [PMID:11144355, PMID:22404616, PMID:30026235]. Phosphorylation of KLC1 Thr466 selectively disrupts the TPR–JIP1 interaction to reduce APP transport velocity, and phosphorylated DOC2B (Y301) recruits KLC1 to facilitate insulin-stimulated GLUT4 translocation, demonstrating that post-translational modifications tune cargo selectivity and transport dynamics [PMID:29093025, PMID:30707251]. Loss of KLC1 in mice impairs phagosome transport in retinal pigment epithelium, producing age-dependent sub-RPE deposits and pathology resembling age-related macular degeneration, and compromises CRMP2-dependent axonal elongation required for forebrain commissure formation [PMID:26261180, PMID:38830696].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Establishing the primary structure of human KLC1 revealed its domain architecture—an N-terminal heptad-repeat coiled-coil and a central/C-terminal tetratricopeptide repeat (TPR) region—providing the first framework for understanding how a kinesin light chain might interface with both heavy chains and cargoes.\",\n      \"evidence\": \"cDNA cloning, sequencing, and heterologous expression in bacteria and CHO cells\",\n      \"pmids\": [\"8274221\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No cargo or heavy-chain binding activity was demonstrated at this stage\",\n        \"Chromosomal assignment was provisional\"\n      ]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Identification of APP and JIP1/Sunday driver as direct, high-affinity TPR-domain ligands of KLC1 established that the light chain functions as a cargo-recognition subunit required for anterograde axonal transport, resolving how kinesin-1 selects specific vesicle populations.\",\n      \"evidence\": \"In vitro binding with measured Kd values (~15–20 nM for APP, ~200 nM for JIP1), co-immunoprecipitation, and genetic KO or mutant validation in mouse and Drosophila\",\n      \"pmids\": [\"11144355\", \"11106729\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The structural basis for how TPR accommodates different cargo motifs was unknown\",\n        \"Mechanism by which cargo binding relieves motor autoinhibition was not addressed\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Discovery that a 10-residue W-acidic (WD) motif in Alcadein-α binds a subset of the KLC1 TPR domain and is sufficient to activate kinesin-1 from its autoinhibited state demonstrated that short linear motifs are the general currency for KLC1-mediated cargo engagement and motor activation.\",\n      \"evidence\": \"In vivo transport assays with synthetic transmembrane cargo constructs, competitive KLC1 excess, and fluorescence correlation spectroscopy\",\n      \"pmids\": [\"22404616\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural visualization of the autoinhibited-to-active transition was lacking\",\n        \"Whether all cargo adaptors share the same TPR sub-site was unresolved\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstrating that KLC1 remains on bidirectionally moving phagosomes and that its knockout impairs phagosome run length, degradation, and RPE homeostasis linked KLC1 function to a non-neuronal cargo (outer-segment phagosomes) and to age-related macular degeneration-like pathology.\",\n      \"evidence\": \"Live-cell imaging and histopathology in aged KLC1 knockout mice\",\n      \"pmids\": [\"26261180\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The cargo adaptor bridging phagosomes to KLC1 TPR was not identified\",\n        \"Whether the AMD-like phenotype involves KLC1-independent kinesin functions was not resolved\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identification of Thr466 phosphorylation as a switch that specifically abolishes TPR–JIP1 interaction and reduces APP fast transport velocity revealed a post-translational mechanism for tuning kinesin-1 cargo selectivity, with relevance to brain aging.\",\n      \"evidence\": \"Phosphomimetic/non-phosphorylatable mutagenesis, co-immunoprecipitation, live-cell velocity analysis, and phospho-specific antibody in aged mouse brains\",\n      \"pmids\": [\"29093025\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"The kinase responsible for Thr466 phosphorylation in vivo was not identified\",\n        \"Causal link between age-dependent phosphorylation and neurodegeneration was correlative\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Isothermal titration calorimetry mapping of the JIP1-binding footprint on the KLC1 TPR domain and demonstration that JIP1 and Alcadein-α W-acidic peptides compete for the same site established a shared, mutually exclusive cargo-binding pocket modulated by an autoinhibitory LFP-acidic motif.\",\n      \"evidence\": \"ITC with systematic KLC1 TPR truncations and point mutations, competition binding experiments\",\n      \"pmids\": [\"30026235\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"High-resolution co-crystal or cryo-EM structure of the TPR–cargo peptide complex was still unavailable\",\n        \"How the LFP-acidic autoinhibitory segment is regulated in cells was unexplored\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Two studies expanded KLC1's functional repertoire beyond neuronal transport: DOC2B phosphorylation at Y301 recruits KLC1 to drive insulin-stimulated GLUT4 translocation in skeletal muscle, and KLC1 suppresses epithelial-mesenchymal transition in breast cancer cells, linking kinesin-1 cargo transport to metabolic and oncogenic signaling.\",\n      \"evidence\": \"Reciprocal co-IP validated by mass spectrometry, Y301 mutagenesis, GLUT4 surface accumulation assay, and transgenic mouse glucose tolerance (DOC2B); siRNA/overexpression with invasion assays (breast cancer)\",\n      \"pmids\": [\"30707251\", \"31204277\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether DOC2B binds the KLC1 TPR domain or a distinct region was not mapped\",\n        \"Molecular mechanism linking KLC1 to epithelial gene expression programs is unclear\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Selective association of SFPQ-RNA granules with a KIF5A/KLC1 tetrameric complex for long-distance axonal transport, and the impairment of this interaction by CMT-causing KIF5A mutations, established KLC1 as a specificity determinant for RNA granule transport essential for axon survival.\",\n      \"evidence\": \"Co-immunoprecipitation, selective binding assays, axon survival assays in CMT model neurons with rescue\",\n      \"pmids\": [\"33284322\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether KLC1 directly contacts SFPQ or acts via an intermediate adaptor was not resolved\",\n        \"Structural basis for KIF5A versus KIF5B selectivity in this complex was not determined\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"CRMP2 was identified as a direct KLC1-binding partner whose disease-associated R565C mutation abolishes this interaction, and genetic interaction between klc1a and crmp2 in zebrafish established KLC1-dependent axonal elongation as essential for forebrain commissure formation.\",\n      \"evidence\": \"Co-immunoprecipitation with WT vs. R566C CRMP2, morpholino knockdown in zebrafish with commissure imaging\",\n      \"pmids\": [\"38830696\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"The KLC1 domain mediating CRMP2 binding was not mapped\",\n        \"Whether the commissure defect reflects transport of a specific cargo downstream of CRMP2 is unknown\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Cryo-EM structures of intact autoinhibited kinesin-1 heterotetramers revealed that KHC coiled-coil 1 (CC1) docks onto the KLC TPR domains to occlude cargo-binding sites, and that cargo SLiM binding to TPR dislocates this 'shoulder' to release motor autoinhibition—providing the first structural mechanism for cargo-coupled kinesin-1 activation.\",\n      \"evidence\": \"Cryo-EM of holoenzyme (preprint), biophysical binding analysis, single-molecule TIRF reconstitution with kinesore pharmacological rescue (preprint)\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structures are from preprints and await peer review\",\n        \"Atomic-resolution details of the TPR–CC1 interface and cargo-bound active state are incomplete\",\n        \"How asymmetric KLC arrangement influences cargo stoichiometry in vivo is unknown\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Outstanding questions include the identity of the kinase(s) phosphorylating KLC1 Thr466 in vivo, the structural basis for selective recognition of different cargo SLiMs by the same TPR pocket, and whether KLC1 splice variants (e.g., KLC1_vE implicated in Alzheimer's disease) confer distinct cargo specificities.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No high-resolution co-structure of KLC1 TPR with any cargo peptide in peer-reviewed literature\",\n        \"Functional distinction among KLC1 splice variants is uncharacterized\",\n        \"In vivo kinase for Thr466 remains unidentified\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1, 4, 9, 10, 12]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [17, 18, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [17, 18, 19]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [0, 1, 4, 6]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0016192\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [0, 1, 4, 6, 12]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [0, 1, 8, 12]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [14]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [10]}\n    ],\n    \"complexes\": [\n      \"Kinesin-1 heterotetramer (KIF5/KLC)\"\n    ],\n    \"partners\": [\n      \"APP\",\n      \"JIP1\",\n      \"KIF5A\",\n      \"KIF5B\",\n      \"CRMP2\",\n      \"DOC2B\",\n      \"SFPQ\",\n      \"DNM1L\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}