{"gene":"MAP1A","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":1994,"finding":"MAP1A light chain 3 (LC3) is a microtubule-binding subunit of both MAP1A and MAP1B; purified recombinant LC3 associates with microtubules assembled in the presence of brain MAPs and with microtubules assembled from purified tubulin, indicating LC3 functions as a MAP1A/MAP1B subunit that can regulate their microtubule-binding activity.","method":"cDNA sequencing, in vitro microtubule co-sedimentation assay with purified recombinant LC3","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified recombinant protein and microtubule co-sedimentation, single lab but two orthogonal methods","pmids":["7908909"],"is_preprint":false},{"year":1984,"finding":"MAP1A localizes along microtubules (mitotic spindle and interphase cytoplasmic fibers) in a wide variety of mammalian cell types; co-localization with tubulin, disappearance upon colchicine/vinblastine treatment, and reorganization by taxol confirmed microtubule association. The punctate staining pattern suggests MAP1A contacts microtubules at discrete foci.","method":"Immunofluorescence microscopy with monoclonal antibody, co-localization with tubulin, drug-treatment experiments (colchicine, vinblastine, taxol), immunoblot analysis","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (immunofluorescence, drug perturbation, immunoblot) replicated across 18 cell lines","pmids":["6142895"],"is_preprint":false},{"year":1987,"finding":"MAP1A forms filamentous cross-bridges between microtubules in Purkinje cell dendrites; immunoelectron microscopy showed gold particles on filamentous materials connected to microtubules but not to neurofilaments; rotary shadowing revealed MAP1A is a long, thin, flexible filamentous molecule.","method":"Immunoelectron microscopy with monoclonal antibody and gold-labeled secondary antibody; quick-freeze deep-etch; rotary shadowing","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Moderate — ultrastructural and direct structural characterization using multiple EM techniques in one rigorous study","pmids":["3553448"],"is_preprint":false},{"year":1994,"finding":"MAP1A binds to both G-actin and F-actin, crosslinks F-actin (causing gelation and increased viscosity), and co-sediments with the gelled actin network; MAP1A and MAP2 bind to common or overlapping sites on actin.","method":"Solid-phase immunoassay, F-actin co-sedimentation, viscometry, SDS-PAGE analysis of purified native MAP1A","journal":"Cell motility and the cytoskeleton","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple in vitro biochemical assays with purified native protein demonstrating actin binding and crosslinking","pmids":["7820861"],"is_preprint":false},{"year":1994,"finding":"A novel microtubule-binding domain in MAP1A was identified that is rich in charged amino acids, is acidic (unlike all other known mammalian microtubule-binding domains which are basic), lacks sequence repeats, and is sufficient for autonomous microtubule binding. Expression of this domain stabilized microtubules against nocodazole and produced a distinct rearrangement pattern compared to MAP2 or tau.","method":"cDNA expression constructs transfected into cultured cell lines, co-localization with microtubules, nocodazole resistance assay","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based functional assays with deletion constructs and drug challenge, single lab with multiple readouts","pmids":["8006079"],"is_preprint":false},{"year":1994,"finding":"Purified native MAP1A promotes both nucleation and elongation of tubulin polymerization, binds 13–15 mol of tubulin dimers per MAP1A molecule, lowers the critical concentration for assembly, and has higher kinetic rate constants (K+1 and K-1) than MAP2.","method":"Turbidimetry-based microtubule assembly kinetics, ion-exchange purification, stoichiometry analysis with purified MAP1A","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified protein, quantitative kinetic analysis, single lab with rigorous biochemical methods","pmids":["7918469"],"is_preprint":false},{"year":2002,"finding":"MAP1A light chain 2 (LC2) binds to microtubules in vivo and in vitro, induces rapid tubulin polymerization via an N-terminal microtubule-binding domain, and also contains a C-terminal actin filament-binding domain that directly interacts with actin. LC2 differs from LC1 (MAP1B light chain) in its effects on microtubule bundling and stability in vivo, establishing LC2 as a potential linker between neuronal microtubules and microfilaments.","method":"In vitro microtubule binding assays, in vivo localization, tubulin polymerization assays, deletion mutagenesis, actin co-sedimentation","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro and in vivo assays with mutagenesis defining functional domains, single lab with multiple orthogonal methods","pmids":["11896150"],"is_preprint":false},{"year":2003,"finding":"DISC1 interacts with MAP1A via the LC2 domain of MAP1A binding to the N-terminus of DISC1, as determined by yeast two-hybrid, mammalian two-hybrid, and co-immunoprecipitation assays.","method":"Yeast two-hybrid, mammalian two-hybrid, co-immunoprecipitation, deletion mapping","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — three orthogonal interaction assays with domain mapping, single lab","pmids":["12812986"],"is_preprint":false},{"year":2004,"finding":"Caldendrin (a neuronal Ca2+-sensor protein) specifically binds to light chain 3 (LC3) of MAP1A/MAP1B at two binding sites; one site shows strict Ca2+-dependency while both require the first two EF-hands of caldendrin. Calmodulin, despite high sequence similarity to caldendrin, cannot bind LC3 at either site.","method":"Yeast two-hybrid, biochemical interaction assays, Ca2+-dependency experiments, deletion/mutagenesis analysis, computer modelling","journal":"Journal of molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple interaction assays including Ca2+-dependency analysis, single lab","pmids":["15095872"],"is_preprint":false},{"year":2004,"finding":"LC2 of MAP1A interacts with the cAMP-binding domain of EPAC1 (exchange protein directly activated by cAMP 1); deletion of the cAMP-binding domain of EPAC1 abolished LC2 interaction in two-hybrid assay; LC2 was found to interact with a GST-fusion of the cAMP-binding domain but not DEP, REM, or CAT domains; EPAC2 also co-immunoprecipitated with LC2 from rat cerebellum.","method":"Yeast two-hybrid screen, co-immunoprecipitation, GST pulldown assay, immunolocalization","journal":"The Biochemical journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal interaction assays (two-hybrid, pulldown, co-IP) with domain mapping, single lab","pmids":["15202935"],"is_preprint":false},{"year":2004,"finding":"LC2 enhances both basal and cAMP-stimulated Rap1 GTPase activation by EPAC1; LC2 elicits conformational changes in the cAMP-binding domain of EPAC1 increasing its sensitivity to cAMP activation; disruption of endogenous EPAC1/LC2 interaction abolished Rap1 activity in PC12 cells; LC2/EPAC1 co-expression enhanced cell adhesion to laminin. Part of LC2's enhancement of EPAC1 activity is through microtubule stabilization (nocodazole partially blocked the effect).","method":"Simultaneous expression system, Rap1 GTPase activation assays, cyclic AMP-agarose binding assay, antibody-mediated disruption of endogenous interaction, cell adhesion assay, nocodazole treatment","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays with gain- and loss-of-function approaches, single lab","pmids":["15591041"],"is_preprint":false},{"year":2005,"finding":"Casein kinase 1 delta (CK1δ) interacts with a 176-aa fragment of MAP1A LC2 (LC2-P16) at two interaction domains in LC2 (near aa 2629–2753 and 2712–2805), and LC2 is phosphorylated by CK1δ as a substrate, suggesting CK1δ modulates microtubule dynamics by changing the phosphorylation status of LC2.","method":"Yeast two-hybrid, co-immunoprecipitation, in vitro kinase assay, deletion mapping","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — interaction assays plus in vitro kinase assay with domain mapping, single lab","pmids":["15961172"],"is_preprint":false},{"year":2005,"finding":"Both the MAP1A heavy chain and LC2 are required for efficient microtubule co-localization; neither heavy chain nor LC2 alone produced filamentous structures along microtubules in COS7 cells, but co-expression of both enabled co-localization with microtubules; yeast two-hybrid confirmed the N-terminal heavy chain/LC2 interaction is important for microtubule binding; full MAP1A and LC2 protected microtubules against nocodazole.","method":"Transfection of tagged constructs in COS7 and Neuro2A cells, fluorescence microscopy, nocodazole resistance assay, yeast two-hybrid","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-based functional assays with domain analysis and yeast two-hybrid, single lab","pmids":["15936015"],"is_preprint":false},{"year":2007,"finding":"The guanylate kinase (GK) domain of PSD-95 directly binds a conserved motif in MAP1A; structural modeling defined a consensus GK-binding sequence in MAP1A; the GK domain uses its GMP-binding region, which has evolved conformational flexibility allowing it to bind diverse protein partners including MAP1A.","method":"Biochemical interaction assays, NMR structural analysis, deletion mutagenesis defining consensus binding sequence","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — NMR structural model with functional validation and mutagenesis, single lab with rigorous structural methods","pmids":["17220895"],"is_preprint":false},{"year":2007,"finding":"LC2 of MAP1A interacts with GTP-bound RhoB (GTP-loading and the 18-aa C-terminal hypervariable domain of RhoB are critical for binding); downregulation of MAP1A/LC2 decreased EGF receptor expression and modified EGF signaling responses, placing LC2 as critical for RhoB function in EGF-induced receptor regulation.","method":"Yeast two-hybrid screen, GST pulldown assay, co-immunoprecipitation, immunofluorescence, RNAi knockdown, EGF receptor expression analysis","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple interaction assays plus functional knockdown with defined signaling readout, single lab","pmids":["18056259"],"is_preprint":false},{"year":2008,"finding":"MAP1A LC2 mediates presynaptic surface retention of Cav2.2 calcium channels via a 23-residue binding domain in the Cav2.2 C-terminus; RNAi knockdown of LC2 reduced surface expression of endogenous Cav2.2 at presynaptic boutons, decreased Ca2+-influx into nerve terminals, and impaired activity-dependent FM4-64 uptake; an LC2 truncation lacking the actin-binding domain could not rescue Cav2.2 surface expression, indicating LC2 anchors surface Cav2.2 to the actin cytoskeleton.","method":"Co-immunoprecipitation, extracellular epitope antibody to detect surface Cav2.2, RNAi knockdown, Ca2+ imaging, FM4-64 uptake assay, Latrunculin A treatment, rescue experiments with truncation mutant","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (Co-IP, live imaging, RNAi, drug perturbation, rescue) with clear functional readouts, single lab","pmids":["18971475"],"is_preprint":false},{"year":2009,"finding":"MAP1A-associated LC3 stabilizes microtubules by decreasing microtubule dynamicity and promoting growth over shortening events (suppression of dynamics), but does not render microtubules resistant to nocodazole-induced depolymerization; in contrast, LC1 and LC2 form nocodazole-resistant bundles. All three light chains co-localize with microtubules and bind taxol-stabilized microtubules in vitro.","method":"Fluorescence microscopy, in vitro microtubule binding assay, nocodazole resistance assay, live-cell measurement of microtubule dynamics","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding plus live-cell dynamics measurements, single lab with multiple assays","pmids":["19233279"],"is_preprint":false},{"year":2005,"finding":"Soluble Abeta oligomers induce sequential proteolysis of MAP1A and MAP1B through the combined action of caspase-3 and calpain (following Ca2+ homeostasis perturbation); calpain activation alone is sufficient for MAP2 isoform proteolysis but MAP1A and MAP1B proteolysis requires both caspase-3 and calpain activation; antioxidants prevent MAP1A proteolysis, highlighting an upstream role for reactive oxygen species.","method":"Time-course degradation assays in primary neurons, caspase-3 and calpain inhibitor treatments, antioxidant rescue, immunoblotting","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological dissection with multiple inhibitors, single lab","pmids":["16234245"],"is_preprint":false},{"year":2012,"finding":"Osteopontin (OPN) associates with MAP1A and MAP1B in rat substantia nigra and striatum, confirmed by affinity pull-down, co-immunoprecipitation, and immunohistochemistry; site-directed mutagenesis of OPN (Y165A, D139E) inhibited some of these interactions.","method":"Yeast two-hybrid, affinity pull-down, co-immunoprecipitation, immunohistochemistry, site-directed mutagenesis","journal":"The European journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple interaction assays with mutagenesis confirming specificity, single lab","pmids":["22779921"],"is_preprint":false},{"year":2012,"finding":"The conserved C-terminal ~125-aa domain (located in the light chains of MAP1A, MAP1B, and MAP1S) directly interacts with α1-syntrophin through the PH2 and PDZ domains of α1-syntrophin; the MAP1A/MAP1B light chain–α1-syntrophin interaction was confirmed by yeast two-hybrid and co-immunoprecipitation from mouse brain.","method":"Yeast two-hybrid screen, co-immunoprecipitation from mouse brain, co-localization in transfected cells","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid plus co-IP from native tissue, single lab","pmids":["23152929"],"is_preprint":false},{"year":2015,"finding":"Loss of MAP1A in mice (spontaneous nm2719 mutation and targeted deletion) causes Purkinje cell degeneration with dendritic focal swellings, disruptions in axon initial segment (AIS) morphology, reduction of the microtubule network in somatodendritic and AIS compartments, aberrant redistribution of MAP1B heavy and light chains to soma/dendrites, and reduction of the MAGUK scaffold protein PSD-93 in Purkinje cells.","method":"Spontaneous mouse mutation characterization, targeted gene knockout, immunofluorescence, histology, immunoblotting","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent genetic loss-of-function models (spontaneous + targeted KO) with multiple cellular phenotype readouts","pmids":["25788676"],"is_preprint":false},{"year":2017,"finding":"Crystal structure of PSD-95 GK domain in complex with a MAP1A peptide at 2.6-Å resolution reveals the MAP1A peptide adopts a unique conformation where hydrophobic residues cluster to interact with the 'hydrophobic site' of PSD-95 GK, and a conserved aspartic acid (D2117) of MAP1A mimics phosphoserine/threonine binding to the 'phospho-site'—a phosphorylation-independent interaction distinct from canonical phosphopeptide-GK complexes.","method":"X-ray crystallography at 2.6-Å resolution, structural comparison with phosphopeptide complexes","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with atomic-level detail and structural comparison, single lab with rigorous structural method","pmids":["28701415"],"is_preprint":false},{"year":2022,"finding":"α-Synuclein preformed fibril-induced accumulation promotes nitric oxide synthesis and S-nitrosylation of MAP1A; inhibition of nitric oxide synthase (with L-NAME) blocked MAP1A S-nitrosylation and normalized NMDAR-dependent calcium transients and overall network activity, placing MAP1A S-nitrosylation downstream of α-syn aggregation-induced nitrosative stress and upstream of NMDAR dysfunction.","method":"Live-cell calcium imaging, network activity assays, nitric oxide synthase inhibitor (L-NAME) treatment, S-nitrosylation detection, primary rat cortical neurons with preformed fibrils","journal":"The Journal of neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional readouts with pharmacological intervention defining pathway position, single lab","pmids":["36414406"],"is_preprint":false},{"year":2024,"finding":"Map1a knockdown in Sertoli cells disrupts microtubule structural organization and secondarily perturbs actin, vimentin, and septin cytoskeletal organization; cadmium-induced Map1a redistribution is associated with p38-MAPK phosphorylation, and the p38-MAPK inhibitor doramapimod restored MT structural organization after cadmium injury, placing p-p38-MAPK activation in the pathway of cadmium-induced Sertoli cell injury downstream of Map1a disruption.","method":"RNAi knockdown, immunofluorescence, RNA-Seq, transcriptome profiling, biochemical cytoskeletal assays, toxicant injury model, pharmacological inhibition with doramapimod","journal":"Reproductive biology and endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi knockdown with multiple cytoskeletal readouts and pharmacological rescue, single lab","pmids":["38570783"],"is_preprint":false},{"year":1991,"finding":"Estramustine specifically binds MAP1A in Du145a cells (confirmed by [3H]estramustine drug uptake and fluorography), causing disruption of MAP1A-associated microtubule networks and inhibiting type IV collagenase secretion; pulse-labeling excluded effects on protein synthesis or turnover.","method":"Immunofluorescence, immunoprecipitation, [3H]estramustine uptake and fluorography, pulse-labeling","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — radiolabeled drug binding plus functional secretion assay with multiple controls, single lab","pmids":["1647395"],"is_preprint":false}],"current_model":"MAP1A is a large microtubule-associated protein complex consisting of a heavy chain and light chains (LC2, LC3) that promotes microtubule polymerization, stabilization, and crosslinking; its light chains bind both microtubules and actin filaments (LC2 via distinct N- and C-terminal domains), thereby physically linking the two cytoskeletal networks; the PSD-95 GK domain binds MAP1A through a phosphorylation-independent, structurally defined interaction; MAP1A LC2 also serves as a signaling scaffold interacting with EPAC1/2 (enhancing Rap1 activation), RhoB (regulating EGF receptor trafficking), Cav2.2 channels (anchoring them to the presynaptic actin cytoskeleton), DISC1, and CK1δ (which phosphorylates LC2); loss of MAP1A in neurons disrupts the dendritic and axon initial segment microtubule network and reduces PSD-93 levels, leading to Purkinje cell degeneration, while S-nitrosylation of MAP1A in the context of synucleinopathy impairs NMDAR-dependent synaptic function."},"narrative":{"mechanistic_narrative":"MAP1A is a large, filamentous neuronal microtubule-associated protein that assembles as a multi-subunit complex of a heavy chain and light chains (LC2, LC3) to nucleate, elongate, stabilize, and crosslink microtubules and to physically couple them to the actin cytoskeleton [PMID:3553448, PMID:7918469, PMID:11896150]. Purified native MAP1A drives both nucleation and elongation of tubulin polymerization, lowers the critical concentration for assembly, and binds 13–15 tubulin dimers per molecule [PMID:7918469]; it engages microtubules through an unusual acidic, repeat-free microtubule-binding domain sufficient for autonomous binding and microtubule stabilization [PMID:8006079], and efficient filamentous decoration of microtubules requires the joint action of the heavy chain and LC2 [PMID:15936015]. Beyond tubulin, MAP1A and its LC2 subunit bind and crosslink F-actin via a distinct C-terminal actin-binding domain, establishing LC2 as a linker between microtubule and microfilament networks [PMID:7820861, PMID:11896150]; the LC3 subunit independently suppresses microtubule dynamics [PMID:19233279]. The light chains also serve as protein-interaction hubs: LC2 binds the PSD-95 guanylate kinase domain through a phosphorylation-independent interaction in which a conserved MAP1A aspartate mimics a phosphoserine [PMID:17220895, PMID:28701415], and recruits signaling proteins including EPAC1/EPAC2 (potentiating cAMP-stimulated Rap1 activation) [PMID:15202935, PMID:15591041], GTP-loaded RhoB (regulating EGF receptor expression) [PMID:18056259], the presynaptic Cav2.2 calcium channel (anchoring it to the actin cytoskeleton to maintain surface expression and Ca2+ influx) [PMID:18971475], and DISC1 [PMID:12812986], while CK1δ binds and phosphorylates LC2 [PMID:15961172]. In vivo, loss of MAP1A causes Purkinje cell degeneration with dendritic swellings, disrupted axon initial segment and somatodendritic microtubule networks, and reduced PSD-93 [PMID:25788676]. In disease contexts MAP1A is a degradative and post-translational target: Aβ oligomers trigger its caspase-3/calpain-dependent proteolysis [PMID:16234245], and α-synuclein fibril–induced nitrosative stress drives MAP1A S-nitrosylation upstream of NMDAR dysfunction [PMID:36414406].","teleology":[{"year":1984,"claim":"Established that MAP1A is a bona fide microtubule-associated protein in living cells, anchoring all later mechanistic work to the cytoskeleton.","evidence":"Immunofluorescence with monoclonal antibody, tubulin co-localization, and colchicine/vinblastine/taxol perturbation across 18 mammalian cell lines","pmids":["6142895"],"confidence":"High","gaps":["Did not define the molecular binding domain","No information on subunit composition or stoichiometry"]},{"year":1987,"claim":"Resolved MAP1A's physical form, showing it is a long flexible filament that builds cross-bridges between dendritic microtubules rather than a compact globular MAP.","evidence":"Immunoelectron microscopy, quick-freeze deep-etch, and rotary shadowing in Purkinje cell dendrites","pmids":["3553448"],"confidence":"High","gaps":["Crosslinking partners beyond microtubules not defined","Molecular basis of cross-bridge formation unknown"]},{"year":1994,"claim":"Defined MAP1A's biochemical activity on tubulin and identified an atypical acidic microtubule-binding domain, explaining how MAP1A stabilizes microtubules distinctly from MAP2/tau.","evidence":"Turbidimetric assembly kinetics and stoichiometry with purified native MAP1A; cDNA expression constructs with nocodazole-resistance assays","pmids":["7918469","8006079"],"confidence":"High","gaps":["Structural basis of acidic-domain microtubule contact not determined","Regulation of binding activity in vivo unknown"]},{"year":1994,"claim":"Showed MAP1A also binds and crosslinks actin and that LC3 is a shared microtubule-binding subunit, introducing the dual-cytoskeletal-linker and modular-light-chain themes.","evidence":"F-actin co-sedimentation, viscometry, and solid-phase immunoassay with purified MAP1A; recombinant LC3 microtubule co-sedimentation","pmids":["7820861","7908909"],"confidence":"High","gaps":["Whether actin and microtubule binding are simultaneous not established","LC3 contribution within the holo-complex not quantified"]},{"year":2002,"claim":"Localized the dual-cytoskeleton linker activity to LC2, mapping separable N-terminal microtubule-binding and C-terminal actin-binding domains.","evidence":"In vitro and in vivo microtubule binding, tubulin polymerization, deletion mutagenesis, and actin co-sedimentation","pmids":["11896150"],"confidence":"High","gaps":["Whether LC2 simultaneously bridges both filament types in cells unresolved","Functional consequence of bridging for neuronal architecture not yet tested"]},{"year":2007,"claim":"Reconstituted the minimal MAP1A complex requirement, demonstrating heavy chain and LC2 must co-assemble for efficient filamentous microtubule decoration.","evidence":"Tagged-construct transfection in COS7/Neuro2A, nocodazole-resistance assays, and yeast two-hybrid (reported 2005)","pmids":["15936015"],"confidence":"Medium","gaps":["Stoichiometry of the assembled complex not defined","In vitro reconstitution of heavy chain/LC2 binding not performed"]},{"year":2008,"claim":"Established MAP1A LC2 as a scaffold beyond the cytoskeleton, defining structurally and biochemically resolved interactions with PSD-95 GK, EPAC1/2, CK1δ, RhoB, and DISC1.","evidence":"Yeast/mammalian two-hybrid, co-IP, GST pulldown, NMR, in vitro kinase, Rap1 GTPase, and EGFR signaling assays across multiple studies","pmids":["12812986","15202935","15591041","15961172","17220895","18056259"],"confidence":"Medium","gaps":["Most interactions rest on single-lab assays","How simultaneous scaffolding is coordinated on one LC2 molecule unknown"]},{"year":2008,"claim":"Demonstrated a physiological scaffolding role at synapses, showing LC2 anchors Cav2.2 channels to the actin cytoskeleton to maintain presynaptic surface expression and calcium influx.","evidence":"Co-IP, surface-epitope detection, RNAi, Ca2+ imaging, FM4-64 uptake, Latrunculin A treatment, and actin-binding-domain truncation rescue","pmids":["18971475"],"confidence":"High","gaps":["Whether the holo-MAP1A complex or free LC2 mediates anchoring unclear","Generalizability to other channels not tested"]},{"year":2009,"claim":"Differentiated the light chains functionally, showing LC3 suppresses microtubule dynamics without conferring nocodazole resistance whereas LC1/LC2 form resistant bundles.","evidence":"Live-cell microtubule dynamics measurement, in vitro binding, and nocodazole-resistance assays","pmids":["19233279"],"confidence":"Medium","gaps":["Mechanistic basis of differing light-chain effects unresolved","Behavior within the native MAP1A complex not addressed"]},{"year":2015,"claim":"Provided in vivo loss-of-function evidence that MAP1A is required for neuronal microtubule network integrity and survival, linking the protein to Purkinje cell degeneration and PSD-93 maintenance.","evidence":"Spontaneous and targeted mouse knockouts with immunofluorescence, histology, and immunoblotting","pmids":["25788676"],"confidence":"High","gaps":["Whether MAP1B redistribution drives or compensates for the phenotype unclear","Causal link between PSD-93 loss and degeneration not dissected"]},{"year":2022,"claim":"Placed MAP1A within neurodegenerative pathways as a degradative and post-translational target, with Aβ-driven proteolysis and α-synuclein–driven S-nitrosylation upstream of NMDAR dysfunction.","evidence":"Caspase-3/calpain inhibitor and antioxidant assays in primary neurons (2005); calcium imaging and NOS inhibition with α-syn preformed fibrils (2022)","pmids":["16234245","36414406"],"confidence":"Medium","gaps":["S-nitrosylation site on MAP1A not mapped","Mechanistic link from modified MAP1A to NMDAR remains correlative"]},{"year":2024,"claim":"Extended MAP1A's cytoskeletal-organizer role beyond neurons, showing it coordinates microtubule, actin, vimentin, and septin networks in Sertoli cells via a p38-MAPK pathway.","evidence":"RNAi knockdown, immunofluorescence, RNA-Seq, cadmium injury model, and doramapimod rescue","pmids":["38570783"],"confidence":"Medium","gaps":["Direct MAP1A interaction with non-tubulin cytoskeletal elements not shown","How p38-MAPK couples to MAP1A disruption unknown"]},{"year":null,"claim":"How the full MAP1A heavy chain/light chain holo-complex integrates simultaneous microtubule crosslinking, actin coupling, and multivalent signaling scaffolding into a single regulated unit remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of the assembled heavy chain/light chain complex","Phospho-regulation by CK1δ not linked to specific functional outputs in vivo","Whether scaffolding interactions occur on holo-complex or free light chains untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[3,4,5,6,16]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[9,13,14,15]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[2,5]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[1,2,3,6]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[15,20,22]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,14]}],"complexes":["MAP1A heavy chain/light chain complex"],"partners":["MAP1B","PSD-95","EPAC1","RHOB","CACNA1B","DISC1","CSNK1D","SNTA1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P78559","full_name":"Microtubule-associated protein 1A","aliases":["Proliferation-related protein p80"],"length_aa":2803,"mass_kda":305.5,"function":"Structural protein involved in the filamentous cross-bridging between microtubules and other skeletal elements","subcellular_location":"Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/P78559/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MAP1A","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"MAP1LC3B","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/MAP1A","total_profiled":1310},"omim":[{"mim_id":"611372","title":"SMALL ADP-RIBOSYLATION FACTOR GTPase-ACTIVATING PROTEIN 1; SMAP1","url":"https://www.omim.org/entry/611372"},{"mim_id":"610267","title":"METHIONINE AMINOPEPTIDASE 1D; METAP1D","url":"https://www.omim.org/entry/610267"},{"mim_id":"605708","title":"RHO GUANINE NUCLEOTIDE EXCHANGE FACTOR 11; ARHGEF11","url":"https://www.omim.org/entry/605708"},{"mim_id":"605210","title":"DISC1 SCAFFOLD PROTEIN; DISC1","url":"https://www.omim.org/entry/605210"},{"mim_id":"604360","title":"SPASTIC PARAPLEGIA 11, AUTOSOMAL RECESSIVE; SPG11","url":"https://www.omim.org/entry/604360"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Mid piece","reliability":"Additional"},{"location":"Principal piece","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":149.9}],"url":"https://www.proteinatlas.org/search/MAP1A"},"hgnc":{"alias_symbol":[],"prev_symbol":["MAP1L"]},"alphafold":{"accession":"P78559","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P78559","model_url":"","pae_url":"","plddt_mean":null},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MAP1A","jax_strain_url":"https://www.jax.org/strain/search?query=MAP1A"},"sequence":{"accession":"P78559","fasta_url":"https://rest.uniprot.org/uniprotkb/P78559.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P78559/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P78559"}},"corpus_meta":[{"pmid":"12812986","id":"PMC_12812986","title":"DISC1 (Disrupted-In-Schizophrenia 1) is a centrosome-associated protein that interacts with MAP1A, MIPT3, ATF4/5 and NUDEL: regulation and loss of interaction with mutation.","date":"2003","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/12812986","citation_count":314,"is_preprint":false},{"pmid":"7908909","id":"PMC_7908909","title":"Molecular characterization of light chain 3. A microtubule binding subunit of MAP1A and MAP1B.","date":"1994","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7908909","citation_count":239,"is_preprint":false},{"pmid":"2509111","id":"PMC_2509111","title":"Microtubule formation and neurite growth in cerebellar macroneurons which develop in vitro: evidence for the involvement of the microtubule-associated proteins, MAP-1a, HMW-MAP2 and Tau.","date":"1989","source":"Brain research. 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adult mouse cerebellum.","date":"1996","source":"The European journal of neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/8713450","citation_count":18,"is_preprint":false},{"pmid":"19233279","id":"PMC_19233279","title":"MAP1a associated light chain 3 increases microtubule stability by suppressing microtubule dynamics.","date":"2009","source":"Molecular and cellular neurosciences","url":"https://pubmed.ncbi.nlm.nih.gov/19233279","citation_count":17,"is_preprint":false},{"pmid":"15936015","id":"PMC_15936015","title":"The functional cooperation of MAP1A heavy chain and light chain 2 in the binding of microtubules.","date":"2005","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/15936015","citation_count":13,"is_preprint":false},{"pmid":"23152929","id":"PMC_23152929","title":"The light chains of microtubule-associated proteins MAP1A and MAP1B interact with α1-syntrophin in the central and peripheral nervous system.","date":"2012","source":"PloS 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The punctate staining pattern suggests MAP1A contacts microtubules at discrete foci.\",\n      \"method\": \"Immunofluorescence microscopy with monoclonal antibody, co-localization with tubulin, drug-treatment experiments (colchicine, vinblastine, taxol), immunoblot analysis\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (immunofluorescence, drug perturbation, immunoblot) replicated across 18 cell lines\",\n      \"pmids\": [\"6142895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"MAP1A forms filamentous cross-bridges between microtubules in Purkinje cell dendrites; immunoelectron microscopy showed gold particles on filamentous materials connected to microtubules but not to neurofilaments; rotary shadowing revealed MAP1A is a long, thin, flexible filamentous molecule.\",\n      \"method\": \"Immunoelectron microscopy with monoclonal antibody and gold-labeled secondary antibody; quick-freeze deep-etch; rotary shadowing\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — ultrastructural and direct structural characterization using multiple EM techniques in one rigorous study\",\n      \"pmids\": [\"3553448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"MAP1A binds to both G-actin and F-actin, crosslinks F-actin (causing gelation and increased viscosity), and co-sediments with the gelled actin network; MAP1A and MAP2 bind to common or overlapping sites on actin.\",\n      \"method\": \"Solid-phase immunoassay, F-actin co-sedimentation, viscometry, SDS-PAGE analysis of purified native MAP1A\",\n      \"journal\": \"Cell motility and the cytoskeleton\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple in vitro biochemical assays with purified native protein demonstrating actin binding and crosslinking\",\n      \"pmids\": [\"7820861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"A novel microtubule-binding domain in MAP1A was identified that is rich in charged amino acids, is acidic (unlike all other known mammalian microtubule-binding domains which are basic), lacks sequence repeats, and is sufficient for autonomous microtubule binding. Expression of this domain stabilized microtubules against nocodazole and produced a distinct rearrangement pattern compared to MAP2 or tau.\",\n      \"method\": \"cDNA expression constructs transfected into cultured cell lines, co-localization with microtubules, nocodazole resistance assay\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based functional assays with deletion constructs and drug challenge, single lab with multiple readouts\",\n      \"pmids\": [\"8006079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Purified native MAP1A promotes both nucleation and elongation of tubulin polymerization, binds 13–15 mol of tubulin dimers per MAP1A molecule, lowers the critical concentration for assembly, and has higher kinetic rate constants (K+1 and K-1) than MAP2.\",\n      \"method\": \"Turbidimetry-based microtubule assembly kinetics, ion-exchange purification, stoichiometry analysis with purified MAP1A\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified protein, quantitative kinetic analysis, single lab with rigorous biochemical methods\",\n      \"pmids\": [\"7918469\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"MAP1A light chain 2 (LC2) binds to microtubules in vivo and in vitro, induces rapid tubulin polymerization via an N-terminal microtubule-binding domain, and also contains a C-terminal actin filament-binding domain that directly interacts with actin. LC2 differs from LC1 (MAP1B light chain) in its effects on microtubule bundling and stability in vivo, establishing LC2 as a potential linker between neuronal microtubules and microfilaments.\",\n      \"method\": \"In vitro microtubule binding assays, in vivo localization, tubulin polymerization assays, deletion mutagenesis, actin co-sedimentation\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro and in vivo assays with mutagenesis defining functional domains, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"11896150\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"DISC1 interacts with MAP1A via the LC2 domain of MAP1A binding to the N-terminus of DISC1, as determined by yeast two-hybrid, mammalian two-hybrid, and co-immunoprecipitation assays.\",\n      \"method\": \"Yeast two-hybrid, mammalian two-hybrid, co-immunoprecipitation, deletion mapping\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — three orthogonal interaction assays with domain mapping, single lab\",\n      \"pmids\": [\"12812986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Caldendrin (a neuronal Ca2+-sensor protein) specifically binds to light chain 3 (LC3) of MAP1A/MAP1B at two binding sites; one site shows strict Ca2+-dependency while both require the first two EF-hands of caldendrin. Calmodulin, despite high sequence similarity to caldendrin, cannot bind LC3 at either site.\",\n      \"method\": \"Yeast two-hybrid, biochemical interaction assays, Ca2+-dependency experiments, deletion/mutagenesis analysis, computer modelling\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple interaction assays including Ca2+-dependency analysis, single lab\",\n      \"pmids\": [\"15095872\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"LC2 of MAP1A interacts with the cAMP-binding domain of EPAC1 (exchange protein directly activated by cAMP 1); deletion of the cAMP-binding domain of EPAC1 abolished LC2 interaction in two-hybrid assay; LC2 was found to interact with a GST-fusion of the cAMP-binding domain but not DEP, REM, or CAT domains; EPAC2 also co-immunoprecipitated with LC2 from rat cerebellum.\",\n      \"method\": \"Yeast two-hybrid screen, co-immunoprecipitation, GST pulldown assay, immunolocalization\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal interaction assays (two-hybrid, pulldown, co-IP) with domain mapping, single lab\",\n      \"pmids\": [\"15202935\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"LC2 enhances both basal and cAMP-stimulated Rap1 GTPase activation by EPAC1; LC2 elicits conformational changes in the cAMP-binding domain of EPAC1 increasing its sensitivity to cAMP activation; disruption of endogenous EPAC1/LC2 interaction abolished Rap1 activity in PC12 cells; LC2/EPAC1 co-expression enhanced cell adhesion to laminin. Part of LC2's enhancement of EPAC1 activity is through microtubule stabilization (nocodazole partially blocked the effect).\",\n      \"method\": \"Simultaneous expression system, Rap1 GTPase activation assays, cyclic AMP-agarose binding assay, antibody-mediated disruption of endogenous interaction, cell adhesion assay, nocodazole treatment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays with gain- and loss-of-function approaches, single lab\",\n      \"pmids\": [\"15591041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Casein kinase 1 delta (CK1δ) interacts with a 176-aa fragment of MAP1A LC2 (LC2-P16) at two interaction domains in LC2 (near aa 2629–2753 and 2712–2805), and LC2 is phosphorylated by CK1δ as a substrate, suggesting CK1δ modulates microtubule dynamics by changing the phosphorylation status of LC2.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, in vitro kinase assay, deletion mapping\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — interaction assays plus in vitro kinase assay with domain mapping, single lab\",\n      \"pmids\": [\"15961172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Both the MAP1A heavy chain and LC2 are required for efficient microtubule co-localization; neither heavy chain nor LC2 alone produced filamentous structures along microtubules in COS7 cells, but co-expression of both enabled co-localization with microtubules; yeast two-hybrid confirmed the N-terminal heavy chain/LC2 interaction is important for microtubule binding; full MAP1A and LC2 protected microtubules against nocodazole.\",\n      \"method\": \"Transfection of tagged constructs in COS7 and Neuro2A cells, fluorescence microscopy, nocodazole resistance assay, yeast two-hybrid\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-based functional assays with domain analysis and yeast two-hybrid, single lab\",\n      \"pmids\": [\"15936015\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The guanylate kinase (GK) domain of PSD-95 directly binds a conserved motif in MAP1A; structural modeling defined a consensus GK-binding sequence in MAP1A; the GK domain uses its GMP-binding region, which has evolved conformational flexibility allowing it to bind diverse protein partners including MAP1A.\",\n      \"method\": \"Biochemical interaction assays, NMR structural analysis, deletion mutagenesis defining consensus binding sequence\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — NMR structural model with functional validation and mutagenesis, single lab with rigorous structural methods\",\n      \"pmids\": [\"17220895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"LC2 of MAP1A interacts with GTP-bound RhoB (GTP-loading and the 18-aa C-terminal hypervariable domain of RhoB are critical for binding); downregulation of MAP1A/LC2 decreased EGF receptor expression and modified EGF signaling responses, placing LC2 as critical for RhoB function in EGF-induced receptor regulation.\",\n      \"method\": \"Yeast two-hybrid screen, GST pulldown assay, co-immunoprecipitation, immunofluorescence, RNAi knockdown, EGF receptor expression analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple interaction assays plus functional knockdown with defined signaling readout, single lab\",\n      \"pmids\": [\"18056259\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MAP1A LC2 mediates presynaptic surface retention of Cav2.2 calcium channels via a 23-residue binding domain in the Cav2.2 C-terminus; RNAi knockdown of LC2 reduced surface expression of endogenous Cav2.2 at presynaptic boutons, decreased Ca2+-influx into nerve terminals, and impaired activity-dependent FM4-64 uptake; an LC2 truncation lacking the actin-binding domain could not rescue Cav2.2 surface expression, indicating LC2 anchors surface Cav2.2 to the actin cytoskeleton.\",\n      \"method\": \"Co-immunoprecipitation, extracellular epitope antibody to detect surface Cav2.2, RNAi knockdown, Ca2+ imaging, FM4-64 uptake assay, Latrunculin A treatment, rescue experiments with truncation mutant\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (Co-IP, live imaging, RNAi, drug perturbation, rescue) with clear functional readouts, single lab\",\n      \"pmids\": [\"18971475\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"MAP1A-associated LC3 stabilizes microtubules by decreasing microtubule dynamicity and promoting growth over shortening events (suppression of dynamics), but does not render microtubules resistant to nocodazole-induced depolymerization; in contrast, LC1 and LC2 form nocodazole-resistant bundles. All three light chains co-localize with microtubules and bind taxol-stabilized microtubules in vitro.\",\n      \"method\": \"Fluorescence microscopy, in vitro microtubule binding assay, nocodazole resistance assay, live-cell measurement of microtubule dynamics\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding plus live-cell dynamics measurements, single lab with multiple assays\",\n      \"pmids\": [\"19233279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Soluble Abeta oligomers induce sequential proteolysis of MAP1A and MAP1B through the combined action of caspase-3 and calpain (following Ca2+ homeostasis perturbation); calpain activation alone is sufficient for MAP2 isoform proteolysis but MAP1A and MAP1B proteolysis requires both caspase-3 and calpain activation; antioxidants prevent MAP1A proteolysis, highlighting an upstream role for reactive oxygen species.\",\n      \"method\": \"Time-course degradation assays in primary neurons, caspase-3 and calpain inhibitor treatments, antioxidant rescue, immunoblotting\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological dissection with multiple inhibitors, single lab\",\n      \"pmids\": [\"16234245\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Osteopontin (OPN) associates with MAP1A and MAP1B in rat substantia nigra and striatum, confirmed by affinity pull-down, co-immunoprecipitation, and immunohistochemistry; site-directed mutagenesis of OPN (Y165A, D139E) inhibited some of these interactions.\",\n      \"method\": \"Yeast two-hybrid, affinity pull-down, co-immunoprecipitation, immunohistochemistry, site-directed mutagenesis\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple interaction assays with mutagenesis confirming specificity, single lab\",\n      \"pmids\": [\"22779921\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The conserved C-terminal ~125-aa domain (located in the light chains of MAP1A, MAP1B, and MAP1S) directly interacts with α1-syntrophin through the PH2 and PDZ domains of α1-syntrophin; the MAP1A/MAP1B light chain–α1-syntrophin interaction was confirmed by yeast two-hybrid and co-immunoprecipitation from mouse brain.\",\n      \"method\": \"Yeast two-hybrid screen, co-immunoprecipitation from mouse brain, co-localization in transfected cells\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid plus co-IP from native tissue, single lab\",\n      \"pmids\": [\"23152929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Loss of MAP1A in mice (spontaneous nm2719 mutation and targeted deletion) causes Purkinje cell degeneration with dendritic focal swellings, disruptions in axon initial segment (AIS) morphology, reduction of the microtubule network in somatodendritic and AIS compartments, aberrant redistribution of MAP1B heavy and light chains to soma/dendrites, and reduction of the MAGUK scaffold protein PSD-93 in Purkinje cells.\",\n      \"method\": \"Spontaneous mouse mutation characterization, targeted gene knockout, immunofluorescence, histology, immunoblotting\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent genetic loss-of-function models (spontaneous + targeted KO) with multiple cellular phenotype readouts\",\n      \"pmids\": [\"25788676\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Crystal structure of PSD-95 GK domain in complex with a MAP1A peptide at 2.6-Å resolution reveals the MAP1A peptide adopts a unique conformation where hydrophobic residues cluster to interact with the 'hydrophobic site' of PSD-95 GK, and a conserved aspartic acid (D2117) of MAP1A mimics phosphoserine/threonine binding to the 'phospho-site'—a phosphorylation-independent interaction distinct from canonical phosphopeptide-GK complexes.\",\n      \"method\": \"X-ray crystallography at 2.6-Å resolution, structural comparison with phosphopeptide complexes\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with atomic-level detail and structural comparison, single lab with rigorous structural method\",\n      \"pmids\": [\"28701415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"α-Synuclein preformed fibril-induced accumulation promotes nitric oxide synthesis and S-nitrosylation of MAP1A; inhibition of nitric oxide synthase (with L-NAME) blocked MAP1A S-nitrosylation and normalized NMDAR-dependent calcium transients and overall network activity, placing MAP1A S-nitrosylation downstream of α-syn aggregation-induced nitrosative stress and upstream of NMDAR dysfunction.\",\n      \"method\": \"Live-cell calcium imaging, network activity assays, nitric oxide synthase inhibitor (L-NAME) treatment, S-nitrosylation detection, primary rat cortical neurons with preformed fibrils\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional readouts with pharmacological intervention defining pathway position, single lab\",\n      \"pmids\": [\"36414406\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Map1a knockdown in Sertoli cells disrupts microtubule structural organization and secondarily perturbs actin, vimentin, and septin cytoskeletal organization; cadmium-induced Map1a redistribution is associated with p38-MAPK phosphorylation, and the p38-MAPK inhibitor doramapimod restored MT structural organization after cadmium injury, placing p-p38-MAPK activation in the pathway of cadmium-induced Sertoli cell injury downstream of Map1a disruption.\",\n      \"method\": \"RNAi knockdown, immunofluorescence, RNA-Seq, transcriptome profiling, biochemical cytoskeletal assays, toxicant injury model, pharmacological inhibition with doramapimod\",\n      \"journal\": \"Reproductive biology and endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi knockdown with multiple cytoskeletal readouts and pharmacological rescue, single lab\",\n      \"pmids\": [\"38570783\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"Estramustine specifically binds MAP1A in Du145a cells (confirmed by [3H]estramustine drug uptake and fluorography), causing disruption of MAP1A-associated microtubule networks and inhibiting type IV collagenase secretion; pulse-labeling excluded effects on protein synthesis or turnover.\",\n      \"method\": \"Immunofluorescence, immunoprecipitation, [3H]estramustine uptake and fluorography, pulse-labeling\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — radiolabeled drug binding plus functional secretion assay with multiple controls, single lab\",\n      \"pmids\": [\"1647395\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MAP1A is a large microtubule-associated protein complex consisting of a heavy chain and light chains (LC2, LC3) that promotes microtubule polymerization, stabilization, and crosslinking; its light chains bind both microtubules and actin filaments (LC2 via distinct N- and C-terminal domains), thereby physically linking the two cytoskeletal networks; the PSD-95 GK domain binds MAP1A through a phosphorylation-independent, structurally defined interaction; MAP1A LC2 also serves as a signaling scaffold interacting with EPAC1/2 (enhancing Rap1 activation), RhoB (regulating EGF receptor trafficking), Cav2.2 channels (anchoring them to the presynaptic actin cytoskeleton), DISC1, and CK1δ (which phosphorylates LC2); loss of MAP1A in neurons disrupts the dendritic and axon initial segment microtubule network and reduces PSD-93 levels, leading to Purkinje cell degeneration, while S-nitrosylation of MAP1A in the context of synucleinopathy impairs NMDAR-dependent synaptic function.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MAP1A is a large, filamentous neuronal microtubule-associated protein that assembles as a multi-subunit complex of a heavy chain and light chains (LC2, LC3) to nucleate, elongate, stabilize, and crosslink microtubules and to physically couple them to the actin cytoskeleton [#2, #5, #6]. Purified native MAP1A drives both nucleation and elongation of tubulin polymerization, lowers the critical concentration for assembly, and binds 13\\u201315 tubulin dimers per molecule [#5]; it engages microtubules through an unusual acidic, repeat-free microtubule-binding domain sufficient for autonomous binding and microtubule stabilization [#4], and efficient filamentous decoration of microtubules requires the joint action of the heavy chain and LC2 [#12]. Beyond tubulin, MAP1A and its LC2 subunit bind and crosslink F-actin via a distinct C-terminal actin-binding domain, establishing LC2 as a linker between microtubule and microfilament networks [#3, #6]; the LC3 subunit independently suppresses microtubule dynamics [#16]. The light chains also serve as protein-interaction hubs: LC2 binds the PSD-95 guanylate kinase domain through a phosphorylation-independent interaction in which a conserved MAP1A aspartate mimics a phosphoserine [#13, #21], and recruits signaling proteins including EPAC1/EPAC2 (potentiating cAMP-stimulated Rap1 activation) [#9, #10], GTP-loaded RhoB (regulating EGF receptor expression) [#14], the presynaptic Cav2.2 calcium channel (anchoring it to the actin cytoskeleton to maintain surface expression and Ca2+ influx) [#15], and DISC1 [#7], while CK1\\u03b4 binds and phosphorylates LC2 [#11]. In vivo, loss of MAP1A causes Purkinje cell degeneration with dendritic swellings, disrupted axon initial segment and somatodendritic microtubule networks, and reduced PSD-93 [#20]. In disease contexts MAP1A is a degradative and post-translational target: A\\u03b2 oligomers trigger its caspase-3/calpain-dependent proteolysis [#17], and \\u03b1-synuclein fibril\\u2013induced nitrosative stress drives MAP1A S-nitrosylation upstream of NMDAR dysfunction [#22].\",\n  \"teleology\": [\n    {\n      \"year\": 1984,\n      \"claim\": \"Established that MAP1A is a bona fide microtubule-associated protein in living cells, anchoring all later mechanistic work to the cytoskeleton.\",\n      \"evidence\": \"Immunofluorescence with monoclonal antibody, tubulin co-localization, and colchicine/vinblastine/taxol perturbation across 18 mammalian cell lines\",\n      \"pmids\": [\"6142895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular binding domain\", \"No information on subunit composition or stoichiometry\"]\n    },\n    {\n      \"year\": 1987,\n      \"claim\": \"Resolved MAP1A's physical form, showing it is a long flexible filament that builds cross-bridges between dendritic microtubules rather than a compact globular MAP.\",\n      \"evidence\": \"Immunoelectron microscopy, quick-freeze deep-etch, and rotary shadowing in Purkinje cell dendrites\",\n      \"pmids\": [\"3553448\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Crosslinking partners beyond microtubules not defined\", \"Molecular basis of cross-bridge formation unknown\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Defined MAP1A's biochemical activity on tubulin and identified an atypical acidic microtubule-binding domain, explaining how MAP1A stabilizes microtubules distinctly from MAP2/tau.\",\n      \"evidence\": \"Turbidimetric assembly kinetics and stoichiometry with purified native MAP1A; cDNA expression constructs with nocodazole-resistance assays\",\n      \"pmids\": [\"7918469\", \"8006079\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of acidic-domain microtubule contact not determined\", \"Regulation of binding activity in vivo unknown\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Showed MAP1A also binds and crosslinks actin and that LC3 is a shared microtubule-binding subunit, introducing the dual-cytoskeletal-linker and modular-light-chain themes.\",\n      \"evidence\": \"F-actin co-sedimentation, viscometry, and solid-phase immunoassay with purified MAP1A; recombinant LC3 microtubule co-sedimentation\",\n      \"pmids\": [\"7820861\", \"7908909\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether actin and microtubule binding are simultaneous not established\", \"LC3 contribution within the holo-complex not quantified\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Localized the dual-cytoskeleton linker activity to LC2, mapping separable N-terminal microtubule-binding and C-terminal actin-binding domains.\",\n      \"evidence\": \"In vitro and in vivo microtubule binding, tubulin polymerization, deletion mutagenesis, and actin co-sedimentation\",\n      \"pmids\": [\"11896150\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LC2 simultaneously bridges both filament types in cells unresolved\", \"Functional consequence of bridging for neuronal architecture not yet tested\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Reconstituted the minimal MAP1A complex requirement, demonstrating heavy chain and LC2 must co-assemble for efficient filamentous microtubule decoration.\",\n      \"evidence\": \"Tagged-construct transfection in COS7/Neuro2A, nocodazole-resistance assays, and yeast two-hybrid (reported 2005)\",\n      \"pmids\": [\"15936015\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry of the assembled complex not defined\", \"In vitro reconstitution of heavy chain/LC2 binding not performed\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Established MAP1A LC2 as a scaffold beyond the cytoskeleton, defining structurally and biochemically resolved interactions with PSD-95 GK, EPAC1/2, CK1\\u03b4, RhoB, and DISC1.\",\n      \"evidence\": \"Yeast/mammalian two-hybrid, co-IP, GST pulldown, NMR, in vitro kinase, Rap1 GTPase, and EGFR signaling assays across multiple studies\",\n      \"pmids\": [\"12812986\", \"15202935\", \"15591041\", \"15961172\", \"17220895\", \"18056259\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Most interactions rest on single-lab assays\", \"How simultaneous scaffolding is coordinated on one LC2 molecule unknown\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrated a physiological scaffolding role at synapses, showing LC2 anchors Cav2.2 channels to the actin cytoskeleton to maintain presynaptic surface expression and calcium influx.\",\n      \"evidence\": \"Co-IP, surface-epitope detection, RNAi, Ca2+ imaging, FM4-64 uptake, Latrunculin A treatment, and actin-binding-domain truncation rescue\",\n      \"pmids\": [\"18971475\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the holo-MAP1A complex or free LC2 mediates anchoring unclear\", \"Generalizability to other channels not tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Differentiated the light chains functionally, showing LC3 suppresses microtubule dynamics without conferring nocodazole resistance whereas LC1/LC2 form resistant bundles.\",\n      \"evidence\": \"Live-cell microtubule dynamics measurement, in vitro binding, and nocodazole-resistance assays\",\n      \"pmids\": [\"19233279\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic basis of differing light-chain effects unresolved\", \"Behavior within the native MAP1A complex not addressed\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Provided in vivo loss-of-function evidence that MAP1A is required for neuronal microtubule network integrity and survival, linking the protein to Purkinje cell degeneration and PSD-93 maintenance.\",\n      \"evidence\": \"Spontaneous and targeted mouse knockouts with immunofluorescence, histology, and immunoblotting\",\n      \"pmids\": [\"25788676\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether MAP1B redistribution drives or compensates for the phenotype unclear\", \"Causal link between PSD-93 loss and degeneration not dissected\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Placed MAP1A within neurodegenerative pathways as a degradative and post-translational target, with A\\u03b2-driven proteolysis and \\u03b1-synuclein\\u2013driven S-nitrosylation upstream of NMDAR dysfunction.\",\n      \"evidence\": \"Caspase-3/calpain inhibitor and antioxidant assays in primary neurons (2005); calcium imaging and NOS inhibition with \\u03b1-syn preformed fibrils (2022)\",\n      \"pmids\": [\"16234245\", \"36414406\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"S-nitrosylation site on MAP1A not mapped\", \"Mechanistic link from modified MAP1A to NMDAR remains correlative\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended MAP1A's cytoskeletal-organizer role beyond neurons, showing it coordinates microtubule, actin, vimentin, and septin networks in Sertoli cells via a p38-MAPK pathway.\",\n      \"evidence\": \"RNAi knockdown, immunofluorescence, RNA-Seq, cadmium injury model, and doramapimod rescue\",\n      \"pmids\": [\"38570783\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct MAP1A interaction with non-tubulin cytoskeletal elements not shown\", \"How p38-MAPK couples to MAP1A disruption unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the full MAP1A heavy chain/light chain holo-complex integrates simultaneous microtubule crosslinking, actin coupling, and multivalent signaling scaffolding into a single regulated unit remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of the assembled heavy chain/light chain complex\", \"Phospho-regulation by CK1\\u03b4 not linked to specific functional outputs in vivo\", \"Whether scaffolding interactions occur on holo-complex or free light chains untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [3, 4, 5, 6, 16]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [9, 13, 14, 15]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [2, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [1, 2, 3, 6]},\n      {\"term_id\": \"GO:0005874\", \"supporting_discovery_ids\": [1, 2, 4, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [15, 20, 22]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 14]}\n    ],\n    \"complexes\": [\"MAP1A heavy chain/light chain complex\"],\n    \"partners\": [\"MAP1B\", \"PSD-95\", \"EPAC1\", \"RhoB\", \"CACNA1B\", \"DISC1\", \"CSNK1D\", \"SNTA1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}