{"gene":"MAP3K1","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":1994,"finding":"MEKK1 (MAP3K1) activates the JNK pathway downstream of Ras but does not activate ERK unless overexpressed, demonstrating two distinct Ras-dependent MAPK cascades: Raf-1→ERK and MEKK→JNK.","method":"Dominant negative and overexpression constructs in mammalian cells, kinase assays","journal":"Science","confidence":"High","confidence_rationale":"Tier 2 / Strong — replicated across multiple labs, multiple orthogonal methods (overexpression, dominant-negative, kinase assays), foundational finding confirmed in subsequent work","pmids":["7992057"],"is_preprint":false},{"year":1994,"finding":"MEKK1 activates the stress-activated protein kinase (SAPK/JNK) pathway by phosphorylating its activator SEK1, which in turn phosphorylates and activates SAPK.","method":"Inducible MEKK1 expression in NIH3T3 cells, in vitro kinase assay with SEK1 as substrate","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro kinase assay demonstrating direct phosphorylation of SEK1 by MEKK1, replicated across multiple subsequent studies","pmids":["7997270"],"is_preprint":false},{"year":1995,"finding":"A constitutively active catalytic domain fragment of MEKK1 (MEKK-C) directly phosphorylates MEK1 at S218 and S222 in vitro; MEKK1 also interacts with MEK1 in the yeast two-hybrid system and activates MEK1/2 in mammalian cells, but does not efficiently activate ERK2 compared to EGF stimulation.","method":"In vitro kinase assay with bacterially expressed MEKK-C, yeast two-hybrid, transfection in mammalian cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with phosphosite identification, two-hybrid interaction, and cell-based assay in one study","pmids":["7624324"],"is_preprint":false},{"year":1997,"finding":"MEKK1 induces site-specific phosphorylation of IκBα in vivo and directly activates the IκBα kinase complex in vitro, placing MEKK1 as a critical component of both the c-Jun and NF-κB stress response pathways.","method":"In vitro IκBα kinase activation assay, in vivo phosphorylation assay","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro activation of IκBα kinase complex demonstrated, replicated and extended in subsequent studies","pmids":["9008162"],"is_preprint":false},{"year":1997,"finding":"Caspase cleavage of MEKK1 at a DEVD motif is required for its kinase activation during anoikis; the cleavage product stimulates apoptosis, and a cleavage-resistant MEKK1 mutant partially protects cells from anoikis, establishing a positive feedback loop between caspases and MEKK1.","method":"Cleavage-resistant and kinase-inactive MEKK1 mutants, caspase inhibitors, cell death assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple mutants (cleavage-resistant, kinase-inactive), caspase inhibitor controls, functional apoptosis readouts; replicated in subsequent caspase-3 cleavage studies","pmids":["9244305"],"is_preprint":false},{"year":1998,"finding":"MEKK1 activates both IKK-α and IKK-β in vivo; IKK-α is present in the MEKK1-inducible high molecular weight IκBα kinase complex and MEKK1 treatment induces phosphorylation of IKK-α in vitro.","method":"In vitro phosphorylation assays, co-immunoprecipitation, transfection in mammalian cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — in vitro kinase assays combined with co-IP and transfection; confirms and extends earlier IκBα kinase findings","pmids":["9689078"],"is_preprint":false},{"year":1998,"finding":"HTLV-I Tax protein binds to the amino terminus of MEKK1, stimulates MEKK1 kinase activity, and increases IKKβ-mediated phosphorylation of IκBα, leading to NF-κB activation.","method":"Co-immunoprecipitation, in vitro kinase assay, dominant-negative mutant studies, transfection","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, in vitro kinase assay with recombinant proteins, dominant-negative validation; single lab but multiple orthogonal methods","pmids":["9630230"],"is_preprint":false},{"year":1998,"finding":"Caspase-3 (CPP32) cleaves MEKK1 after residue D68 both in vivo and in vitro during Fas-induced apoptosis; this cleavage redistributes MEKK1 from a Triton-insoluble (particulate) compartment to a Triton-soluble (cytoplasmic) compartment and is required for MEKK1 and SAPK activation during apoptosis but not during rapid stress responses.","method":"Sequencing of cleavage products, immunofluorescence, subcellular fractionation, viral and chemical caspase inhibitors","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — cleavage site identified by sequencing, subcellular redistribution shown by immunofluorescence and fractionation, caspase inhibitor controls; consistent with parallel finding in PMID 9244305","pmids":["9576928"],"is_preprint":false},{"year":1999,"finding":"MEKK1 interacts directly with α-actinin via residues 221–559 of its N-terminal regulatory domain, and both endogenous and overexpressed MEKK1 co-localize with α-actinin along actin stress fibers and at focal adhesions; kinase activity is not required for this localization.","method":"Yeast two-hybrid screen, co-immunoprecipitation, in vitro binding with purified α-actinin, immunofluorescence colocalization","journal":"Cell motility and the cytoskeleton","confidence":"High","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid identification, confirmed by reciprocal Co-IP and direct in vitro binding with purified protein, colocalization by immunofluorescence","pmids":["10401575"],"is_preprint":false},{"year":1999,"finding":"MEKK1 is required for JNK activation in response to microtubule disruption (taxol) but not actin fiber disruption; targeted disruption of MEKK1 in ES cells abolishes JNK activation and increases apoptosis after taxol treatment; MEKK1 expression is elevated 3-fold in mitosis.","method":"Targeted gene disruption in embryonic stem cells, JNK kinase assays, cell cycle analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with specific phenotypic readout (JNK activation loss), parallel MEKK2 knockout as specificity control, replicated in subsequent MEKK1-/- studies","pmids":["10212239"],"is_preprint":false},{"year":1999,"finding":"MEKK-1 activates Smad2-mediated transcription in endothelial cells independently of the C-terminal SSXS motif of Smad2 (the TGF-β receptor phosphorylation site), increases Smad2 phosphorylation state, enhances Smad2-Smad4 interactions, induces nuclear localization of Smad2/Smad4, and stimulates Smad-coactivator interactions.","method":"Constitutively active MEKK-1 transfection, Gal4-Smad2 reporter assay, co-immunoprecipitation, nuclear fractionation, shear stress experiment","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single lab, multiple reporter and co-IP methods but no direct in vitro phosphorylation of Smad2 by MEKK1 demonstrated","pmids":["10085121"],"is_preprint":false},{"year":1999,"finding":"MEKK1-deficient ES cell-derived cardiac myocytes fail to activate JNK in response to oxidative stress, leading to enhanced TNF-α production and increased apoptosis; the MEKK1-JNK pathway negatively regulates TNF-α production to protect cardiac myocytes.","method":"Targeted gene disruption (MEKK1-/- ES cells), JNK and p38 kinase assays, TNF-α ELISA, apoptosis assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with mechanistic pathway dissection (JNK vs p38, TNF-α measurement), multiple orthogonal readouts","pmids":["10611349"],"is_preprint":false},{"year":2000,"finding":"Endogenous MEKK1 physically binds to endogenous ERK2, MEK1, and Raf-1, indicating MEKK1 can scaffold all three kinases of the ERK MAP kinase module.","method":"Co-immunoprecipitation of endogenous proteins","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — endogenous co-IP in a single lab; mechanistically informative but single method","pmids":["10969079"],"is_preprint":false},{"year":2000,"finding":"Raf-mediated NF-κB activation is blocked by a dominant-negative form of MEKK1, indicating Raf induces NF-κB via MEKK1 as a membrane shuttle kinase, but not through the classical MEK-ERK cascade.","method":"Dominant-negative MEKK1, pharmacological pathway inhibitors, NF-κB reporter assays, transformation assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — dominant-negative approach with pathway inhibitor controls; functional epistasis established but no direct biochemical interaction shown","pmids":["10758165"],"is_preprint":false},{"year":2001,"finding":"Protein kinase G (PKG) directly phosphorylates the N-terminal domain of MEKK1 in vitro, and constitutively active PKG activates JNK1 via a PKG→MEKK1→SEK1→JNK1 pathway; dominant-negative MEKK1 blocks PKG-induced JNK1 activation.","method":"In vitro kinase assay with purified PKG and MEKK1, dominant-negative MEKK1, JNK1 activation assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vitro phosphorylation demonstrated plus dominant-negative epistasis; single lab","pmids":["11278263"],"is_preprint":false},{"year":2001,"finding":"RIP (receptor-interacting protein) physically associates with MEKK1 in vitro and in vivo, phosphorylates MEKK1 at Ser-957 and Ser-994, and is required for TNF-α-induced MEKK1 activation; a non-phosphorylatable S957A/S994A MEKK1 mutant fails to be activated by RIP and blocks RIP-induced IKKβ and NF-κB activation.","method":"Co-immunoprecipitation, in vitro kinase assay, site-directed mutagenesis, RIP-deficient Jurkat cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct phosphorylation site identification by mutagenesis, co-IP in vitro and in vivo, genetic (RIP-deficient) cell confirmation","pmids":["11369754"],"is_preprint":false},{"year":2002,"finding":"Purified active GCK (germinal center kinase, a Ste20 homologue) and TRAF2 activate recombinant MEKK1 in vitro; autophosphorylation within the MEKK1 kinase domain activation loop is required for activation; GCK promotes MEKK1 oligomerization in vivo, suggesting activation via induced oligomerization and autophosphorylation.","method":"In vitro activation assay with purified proteins, forced oligomerization assay, kinase domain mutagenesis, co-immunoprecipitation","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — first in vitro reconstitution of MEKK1 activation using purified proteins; autophosphorylation mechanism supported by mutagenesis","pmids":["11784851"],"is_preprint":false},{"year":2002,"finding":"MEKK1 is required for inducible urokinase-type plasminogen activator (uPA) expression in response to PMA or FGF-2; MEKK1-deficient fibroblasts show greatly reduced uPA expression and activity, which is restored by MEKK1 transfection; this requires MEKK1-dependent MKK1 and JNK activity.","method":"MEKK1-/- fibroblasts, re-expression rescue, uPA activity assay, dominant-negative MKK constructs","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with rescue by re-expression, specific pathway dissection with MKK1 and JNK dominant-negatives; MEKK2 knockout as specificity control","pmids":["12493778"],"is_preprint":false},{"year":2002,"finding":"MEKK1 is essential for Gαq-induced cardiac hypertrophy in vivo; MEKK1 knockout abolishes JNK activation, cardiac mass increase, myocyte enlargement, ANF induction, and ventricular dysfunction caused by Gαq overexpression, while other terminal MAPKs are unaffected.","method":"MEKK1 gene knockout in mice, ES cell-derived cardiomyocytes, JNK/ERK/p38 kinase assays, echocardiography, histology","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic knockout with selective JNK phenotype (other MAPKs unaffected as controls), multiple physiological readouts","pmids":["11891332"],"is_preprint":false},{"year":2003,"finding":"RhoA, but not Rac or Cdc42, binds to the N-terminal regulatory domain (including the PHD domain) of MEKK1; Rho-GTP stimulates MEKK1 kinase activity up to 10-fold toward MEK4 but does not result in RhoA ubiquitination by MEKK1.","method":"GST pulldown, in vitro kinase assay, PHD domain cysteine mutagenesis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct binding and kinase activation demonstrated in vitro with purified proteins, mutagenesis of PHD domain; single lab","pmids":["14581471"],"is_preprint":false},{"year":2003,"finding":"Glycogen synthase kinase 3β (GSK3β) physically associates with endogenous MEKK1 and activates MEKK1 kinase activity; GSK3β-mediated MEKK1 activation is inhibited by insulin via PI3K; MEKK1 activity is reduced in GSK3β-/- fibroblasts and restored by ectopic GSK3β expression.","method":"Co-immunoprecipitation of endogenous proteins, in vitro kinase assay, GSK3β knockout fibroblasts, pharmacological inhibition (wortmannin)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — endogenous co-IP, genetic knockout cells with rescue, in vitro kinase assays, pharmacological validation; multiple orthogonal methods","pmids":["12584189"],"is_preprint":false},{"year":2004,"finding":"GST Mu 1-1 (GST M1-1) directly binds MEKK1 and inhibits its kinase activity in vitro; GST M1-1 co-immunoprecipitates with endogenous MEKK1 in L929 cells, interferes with MEKK1-SEK1 binding, and suppresses MEKK1-mediated apoptosis.","method":"In vitro binding and kinase assays, endogenous co-immunoprecipitation, co-immunoprecipitation competition assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in vitro binding and inhibition of kinase activity, endogenous Co-IP; single lab","pmids":["15299005"],"is_preprint":false},{"year":2004,"finding":"Ceramide directly binds to MEKK1 in glomerular endothelial cells as shown by radioiodinated photoaffinity labeling and ceramide-coupled Sepharose affinity chromatography; this binding activates the SAPK/JNK cascade, which mediates ceramide-induced apoptosis.","method":"Photoaffinity labeling with [125I]TID-ceramide, affinity chromatography with ceramide-Sepharose, JNK inhibitor functional assay","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding demonstrated by two independent biochemical methods (photoaffinity and affinity chromatography); single lab","pmids":["15164763"],"is_preprint":false},{"year":2006,"finding":"MEKK1 PHD/RING finger domain exhibits E3 ubiquitin ligase activity toward c-Jun in vitro and in vivo; MEKK1 mediates ubiquitination-dependent degradation of c-Jun in response to osmotic stress, and MEKK1-/- cells show higher c-Jun protein levels; c-Jun downregulation by MEKK1 promotes apoptosis.","method":"In vitro ubiquitination assay, MEKK1-/- cell lines, osmotic stress treatment, rescue by c-Jun overexpression","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro E3 ligase reconstitution, genetic knockout confirmation, functional apoptosis rescue; multiple orthogonal methods","pmids":["17101801"],"is_preprint":false},{"year":2006,"finding":"MEKK1 is required for CD40-mediated activation of JNK, p38, and c-Jun in B cells; MEKK1 is recruited to CD40 and TRAF2 after CD40 ligation; Map3k1(deltaKD) mice have defective germinal center formation and reduced thymus-dependent antibody production.","method":"Map3k1 kinase domain knockin mice, kinase assays, co-immunoprecipitation (CD40-TRAF2-MEKK1), B cell proliferation assays, in vivo immunization","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockin mouse model, co-IP of endogenous proteins, multiple kinase and functional readouts in vivo","pmids":["17143273"],"is_preprint":false},{"year":2006,"finding":"MEKK1 controls mammary tumor cell dissemination and lung metastasis by regulating urokinase-type plasminogen activator (uPA) expression, gelatinase activity, and cell migration/invasion; MEKK1-/- mice with PyMT mammary tumors show delayed tumor cell dissemination associated with reduced uPA and gelatinase activity and prolonged basement membrane integrity.","method":"MEKK1-/- mouse model with PyMT transgene, siRNA knockdown in MDA-MB-231 cells, gelatin zymography, invasion assay, lung metastasis counts","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic knockout and siRNA knockdown with mechanistic pathway readouts (uPA, gelatinase); replicated in human cancer cell line","pmids":["16568086"],"is_preprint":false},{"year":2008,"finding":"MEKK1 is an essential component of antiviral signaling downstream of IPS-1 in the RIG-I-like helicase pathway; forced expression of MEKK1 with IRF3 induces IFN-β, whereas MEKK1 siRNA knockdown inhibits IFN-β induction by poly(I:C); MEKK1 mediates NF-κB and MAPK activation but not IRF3 activation in this pathway.","method":"siRNA knockdown, forced expression, IFN-β promoter reporter assay, TRAF6-/- and TAK1-/- MEF comparison","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — siRNA and overexpression with reporter assays; genetic comparison to other pathway components; single lab","pmids":["18984593"],"is_preprint":false},{"year":2010,"finding":"MEKK-1 mediates IL-1β-induced increase in intestinal epithelial tight junction permeability through activation of the canonical NF-κB pathway and MLCK gene activation; MEKK-1 knockdown inhibits these effects, while NIK (non-canonical pathway) knockdown does not affect TJ permeability.","method":"siRNA knockdown in Caco-2 monolayers, transepithelial resistance measurement, NF-κB pathway inhibitors","journal":"The American journal of pathology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — siRNA with functional barrier readout; pathway specificity shown by NIK vs MEKK-1 comparison; single lab","pmids":["21048223"],"is_preprint":false},{"year":2010,"finding":"MAP3K1 interacts with Axin1; the Axin1-MAP3K1 interaction is induced and modulated by Wnt stimulation; MAP3K1 E3 ubiquitin ligase activity (not kinase activity) is required for Wnt/β-catenin-TCF/LEF transcriptional activity; MAP3K1 siRNA abolishes TCF/LEF-driven transcription and Wnt3A-driven endogenous gene expression.","method":"Immunoprecipitation-coupled proteomics (Axin1 IP-MS), co-IP in HEK293T cells, siRNA knockdown, ubiquitin ligase-dead and kinase-dead mutant transfection, TCF reporter assay","journal":"Biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics identification confirmed by co-IP, functional mutant analysis with two independent mutations; single lab","pmids":["20128690"],"is_preprint":false},{"year":2010,"finding":"The WD40-repeat scaffold protein Han11 directly binds MEKK1 in vitro and regulates the threshold and amplitude of MEKK1-triggered stress signaling; Han11 couples MEKK1 to DYRK1 and HIPK2 in a signaling complex; knockdown of Han11 alters the kinetics and amplitude of MEKK1-triggered gene expression.","method":"In vitro binding assays, knockdown experiments, reporter assays for MEKK1-triggered gene expression","journal":"The EMBO journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding confirmed in vitro, functional consequences of knockdown shown; single lab","pmids":["20940704"],"is_preprint":false},{"year":2011,"finding":"MAP3K1 integrates TGF-α/EGFR-RhoA signals and JNK-c-Jun signals during eyelid closure; c-Jun (induced by EGFR-RhoA) binds the Map3k1 promoter in a phosphorylation-independent manner to drive MAP3K1 expression; MAP3K1 then phosphorylates JNK-c-Jun to activate AP-1 and downstream targets (PAI-1), forming an intracrine regulatory loop.","method":"ChIP (c-Jun binding to Map3k1 promoter), RhoA knockout mice, Map3k1 hemizygote mice, JNK-c-Jun phosphorylation assays, PAI-1 expression","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP for direct promoter binding, genetic mouse models (RhoA knockout, Map3k1 hemizygote), multiple pathway readouts","pmids":["21969564"],"is_preprint":false},{"year":2013,"finding":"MAP3K1 missense mutations causing 46,XY disorder of sex development increase binding of RHOA, MAP3K4, and FRAT1 while reducing SOX9/FGF9/SRY expression and increasing WNT/β-catenin/FOXL2 activity; these effects are partially rescued by co-transfection with wild-type MAP3K4.","method":"Cell transfection with wild-type or mutant MAP3K1 in B-lymphoblastoid and NT2/D1 cells, Western blot for phosphorylation of downstream targets, siRNA phenocopying","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-factor binding and downstream phosphorylation shown in cell lines, rescue experiment; gain-of-function nature established but mechanistic detail limited","pmids":["24135036"],"is_preprint":false},{"year":2013,"finding":"MAP3K1 encodes both a kinase domain and a PHD/RING finger E3 ubiquitin ligase domain; full-length MAP3K1 regulates cell migration and pro-survival signaling, while its caspase-3 cleavage product promotes apoptosis; the E3 ligase domain ubiquitylates c-Jun and ERK1/2.","method":"Review synthesizing genetic knockouts, biochemical assays, and ubiquitination assays from multiple studies (not a primary experimental paper, but summarizes established experimental findings)","journal":"Genes & cancer","confidence":"Medium","confidence_rationale":"Tier 3 / Strong — review citing multiple independent experimental demonstrations; included because it summarizes validated mechanisms about ERK1/2 ubiquitination (not fully covered elsewhere in corpus)","pmids":["24386504"],"is_preprint":false},{"year":2014,"finding":"The MEKK1 PHD motif functions as an E3 ubiquitin ligase that mediates Lys63-linked poly-ubiquitination of TAB1, using the conjugating enzyme UBE2N; this ubiquitination of TAB1 regulates TAK1 and MAPK (p38 and JNK) activation by TGF-β and EGF; PHD-inactive knockin (Map3k1(mPHD)) cells show defective MAPK responses to TGF-β, EGF, and microtubule disruption but not to hyperosmotic stress.","method":"Map3k1(mPHD) knockin ES cells and mice, protein microarray substrate profiling, ubiquitination assays (Lys63 linkage), in vitro E3 ligase reconstitution","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of E3 ligase activity, substrate identification by microarray, linkage specificity (K63), knockin mouse genetics with multiple pathway readouts","pmids":["25260751"],"is_preprint":false},{"year":2014,"finding":"MarvelD3, a tight junction transmembrane component, recruits MEKK1 to junctions; MarvelD3 expression inversely correlates with JNK activity; loss of MarvelD3 increases MEKK1-JNK signaling, cell migration, and proliferation, while re-expression in metastatic cells inhibits these processes.","method":"MarvelD3 depletion and re-expression, JNK phosphorylation assays, cell migration and proliferation assays, in vivo tumor formation, MEKK1 co-immunoprecipitation","journal":"The Journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional link between MarvelD3-MEKK1 junction recruitment and JNK activation established; Co-IP and multiple cell-based readouts; single lab","pmids":["24567356"],"is_preprint":false},{"year":2018,"finding":"Loss-of-function mutations in MAP3K1 disable the JNK-JUN-mediated feedback loop activated by MEK inhibition (via DUSP4 suppression and HER RTK activation), causing sensitivity to MEK inhibitors; this was confirmed in PDX tumor models.","method":"Genetic analysis with MEK inhibitor treatment in cancer cell lines and 168 PDX tumors, JNK-JUN pathway readouts, DUSP4 siRNA epistasis","journal":"Cell research","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic dissection of JNK-JUN feedback loop, validated in vivo in large PDX cohort, epistasis via DUSP4 siRNA","pmids":["29795445"],"is_preprint":false},{"year":2018,"finding":"MAP3K1 disruption enhances AKT phosphorylation and IRS-1 stability, promotes IRS-1 binding to p85 and PI3Kα activity; this results from deficient MAP3K1-JNK signaling increasing IRS-1 stability, thereby conferring resistance to AKT inhibitors.","method":"CRISPR knockout of MAP3K1 in PIK3CA-mutant cell lines, Western blot for p-AKT/IRS-1, co-immunoprecipitation (IRS-1/p85), 3D MCF10A models, in vivo xenograft","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR knockout with mechanistic pathway readouts (IRS-1/p85 co-IP, p-AKT), confirmed in vivo; single lab","pmids":["29765551"],"is_preprint":false},{"year":2019,"finding":"MAP3K1 mutations causing 46,XY gonadal dysgenesis cluster in three semi-contiguous domains: an N-terminal Guanine Exchange Factor-homology domain (residues 164–231), a PHD domain (residues 442–495), and an ARMadillo repeat domain (residues 566–862); these mutations increase binding of RHOA, MAP3K4, and FRAT1 and decrease binding of RAC1, with differential effects depending on domain location.","method":"Structural modeling, transfection of mutant MAP3K1 constructs, co-immunoprecipitation for co-factor binding, downstream phosphorylation assays","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — domain mapping via structural modeling and co-IP binding assays; consistent with prior functional data but primarily structural/binding characterization in a single study","pmids":["30608580"],"is_preprint":false}],"current_model":"MAP3K1 (MEKK1) is a dual-function serine/threonine kinase and PHD/RING-finger E3 ubiquitin ligase that serves as a central signaling hub: its kinase domain phosphorylates SEK1/MKK4/MKK7 to activate the JNK pathway and can also activate MEK1/2-ERK and IKK-NF-κB cascades in response to diverse stimuli including cytokines, growth factors, microtubule disruption, osmotic stress, and apoptotic signals; caspase-3 cleaves MEKK1 at D68 (or a DEVD motif), releasing and activating a C-terminal kinase fragment that amplifies apoptosis via a positive feedback loop; its PHD motif catalyzes K63-linked ubiquitination of substrates including c-Jun, ERK1/2, and TAB1 (using UBE2N) to regulate their stability and TAK1/MAPK activation; the long N-terminal regulatory domain scaffolds interacting proteins including α-actinin, RhoA, GCK/TRAF2, GSK3β, RIP, and Axin1, localizing MEKK1 to stress fibers and focal adhesions and enabling context-dependent pathway selectivity; full-length MAP3K1 supports cell survival, migration, and uPA-dependent invasion, while the caspase-generated fragment promotes apoptosis."},"narrative":{"mechanistic_narrative":"MAP3K1 (MEKK1) is a central stress- and survival-signaling hub that couples diverse extracellular and intracellular cues to the JNK, ERK, and NF-κB cascades through dual kinase and E3 ubiquitin ligase activities [PMID:7992057, PMID:24386504]. Its kinase domain directly phosphorylates and activates the JNK activator SEK1/MKK4 [PMID:7997270], can phosphorylate MEK1 at S218/S222 [PMID:7624324], and directly activates the IκBα/IKK complex to drive NF-κB [PMID:9008162, PMID:9689078], establishing parallel control of the c-Jun/JNK and NF-κB stress pathways. Activation requires autophosphorylation in the kinase activation loop and is triggered by oligomerization (GCK/TRAF2), upstream phosphorylation (RIP at S957/S994, PKG, GSK3β), and small-GTPase binding (Rho-GTP), with a long N-terminal regulatory domain serving as a scaffold that integrates these inputs [PMID:11784851, PMID:11369754, PMID:12584189, PMID:14581471]. A distinct PHD/RING domain confers E3 ligase activity that mediates K63-linked ubiquitination of TAB1 via UBE2N to control TAK1/MAPK activation, and ubiquitin-dependent degradation of c-Jun, functions genetically separable from its kinase activity [PMID:25260751, PMID:17101801]. The N-terminal domain anchors MEKK1 to α-actinin along stress fibers and focal adhesions and to tight junctions, linking it to cytoskeletal context and cell migration [PMID:10401575, PMID:24567356]. Functionally, full-length MAP3K1 supports cell survival, migration, and uPA-dependent invasion and metastasis [PMID:12493778, PMID:16568086], whereas caspase-3 cleavage at D68/a DEVD motif liberates a C-terminal fragment that amplifies apoptosis through a caspase–MEKK1 feedback loop [PMID:9244305, PMID:9576928]. Genetically, MAP3K1 missense mutations cause 46,XY disorder of sex development by altering cofactor binding (RHOA, MAP3K4, FRAT1) and shifting the SOX9-versus-WNT/β-catenin balance in the gonad [PMID:24135036, PMID:30608580].","teleology":[{"year":1994,"claim":"Established MEKK1 as a JNK-pathway-selective MAP3K acting downstream of Ras and biochemically distinct from the Raf→ERK route, defining two parallel Ras-dependent MAPK cascades.","evidence":"Dominant-negative and overexpression constructs plus in vitro kinase assays showing direct phosphorylation of SEK1, in mammalian cells","pmids":["7992057","7997270"],"confidence":"High","gaps":["Endogenous physiological stimuli not yet defined","ERK activation only under overexpression, leaving native ERK role ambiguous"]},{"year":1995,"claim":"Showed MEKK1 can directly phosphorylate MEK1 at its activating sites, raising the question of pathway selectivity between JNK and ERK modules.","evidence":"In vitro kinase assay with bacterial MEKK-C, yeast two-hybrid, and transfection","pmids":["7624324"],"confidence":"High","gaps":["Inefficient ERK2 activation vs EGF leaves physiological relevance of MEK1 phosphorylation unclear"]},{"year":1997,"claim":"Extended MEKK1 beyond JNK to the NF-κB axis by demonstrating direct activation of the IκBα kinase complex, positioning it at the junction of two stress pathways.","evidence":"In vitro IKK activation assay and in vivo IκBα phosphorylation","pmids":["9008162"],"confidence":"High","gaps":["How a single kinase selects JNK vs NF-κB output not resolved"]},{"year":1997,"claim":"Revealed a caspase–MEKK1 positive feedback loop in which caspase cleavage activates MEKK1 to amplify apoptosis, distinguishing pro-apoptotic from survival functions.","evidence":"Cleavage-resistant and kinase-inactive mutants with caspase inhibitors and anoikis assays","pmids":["9244305"],"confidence":"High","gaps":["Precise cleavage site refined later","Balance between survival and apoptotic outputs context-dependent and not quantified"]},{"year":1998,"claim":"Mapped the apoptotic cleavage to caspase-3 at D68 and linked it to subcellular redistribution, clarifying how cleavage repartitions MEKK1 activity.","evidence":"Cleavage-product sequencing, immunofluorescence, and subcellular fractionation with caspase inhibitors during Fas-induced apoptosis","pmids":["9576928"],"confidence":"High","gaps":["Functional consequence of particulate-to-soluble redistribution not mechanistically dissected"]},{"year":1998,"claim":"Defined IKK-α and IKK-β as MEKK1 targets and identified viral Tax as an N-terminus-binding activator, showing the regulatory domain controls NF-κB output.","evidence":"In vitro phosphorylation, co-IP of the IKK complex, and Tax dominant-negative studies","pmids":["9689078","9630230"],"confidence":"High","gaps":["Stoichiometry and assembly of the high-MW IKK complex incompletely defined"]},{"year":1999,"claim":"Identified the N-terminal domain as a cytoskeletal scaffold by mapping direct α-actinin binding and localization to stress fibers/focal adhesions independent of kinase activity.","evidence":"Yeast two-hybrid, reciprocal co-IP, in vitro binding with purified α-actinin, and immunofluorescence colocalization","pmids":["10401575"],"confidence":"High","gaps":["Signaling consequence of cytoskeletal anchoring not yet linked to pathway output"]},{"year":1999,"claim":"Genetic knockouts established a non-redundant requirement for MEKK1 in JNK activation by specific stresses (microtubule disruption, oxidative stress) and in cytoprotection.","evidence":"Targeted disruption in ES cells and cardiac myocytes with JNK/p38 kinase assays, TNF-α measurement, and apoptosis readouts","pmids":["10212239","10611349"],"confidence":"High","gaps":["Stimulus-selectivity mechanism (why some stresses require MEKK1 and others do not) unexplained"]},{"year":2000,"claim":"Suggested MEKK1 can scaffold the entire ERK module and relay Raf-induced NF-κB, expanding its role from kinase to multi-pathway organizer.","evidence":"Endogenous co-IP of ERK2/MEK1/Raf-1 and dominant-negative epistasis in NF-κB reporter assays","pmids":["10969079","10758165"],"confidence":"Medium","gaps":["Co-IP and epistasis only; no direct biochemical demonstration of scaffolding stoichiometry"]},{"year":2002,"claim":"Provided the first in vitro reconstitution of MEKK1 activation, defining oligomerization-induced activation-loop autophosphorylation by GCK/TRAF2 as the core activation mechanism.","evidence":"In vitro activation with purified GCK and TRAF2, forced-oligomerization assay, and kinase-domain mutagenesis","pmids":["11784851"],"confidence":"High","gaps":["Endogenous triggers of oligomerization in specific pathways not enumerated"]},{"year":2002,"claim":"Connected MEKK1 to physiology and disease by showing it is essential for Gαq-induced cardiac hypertrophy and for inducible uPA expression driving invasion.","evidence":"MEKK1 knockout mice/ES-derived cardiomyocytes and MEKK1-/- fibroblasts with rescue, plus uPA activity assays and MKK/JNK dominant-negatives","pmids":["11891332","12493778"],"confidence":"High","gaps":["Direct substrates linking JNK to uPA transcription not identified"]},{"year":2003,"claim":"Mapped multiple direct upstream activators (RIP phosphorylation, RhoA-GTP binding, GSK3β) onto the regulatory domain, explaining context-dependent activation.","evidence":"Co-IP, in vitro kinase assays with purified proteins, site-directed mutagenesis, GST pulldown, and knockout-cell rescue","pmids":["11369754","14581471","12584189"],"confidence":"High","gaps":["How competing activator inputs are integrated into distinct outputs unresolved"]},{"year":2006,"claim":"Defined the PHD/RING domain as a functional E3 ligase, with c-Jun ubiquitination/degradation as a kinase-independent output controlling apoptosis.","evidence":"In vitro ubiquitination reconstitution, MEKK1-/- cells, and rescue under osmotic stress","pmids":["17101801"],"confidence":"High","gaps":["Full substrate repertoire of the E3 activity not yet defined at this stage"]},{"year":2006,"claim":"Demonstrated an in vivo immune role via CD40/TRAF2 recruitment driving JNK/p38/c-Jun and germinal center formation.","evidence":"Map3k1 kinase-domain knockin mice, co-IP of CD40-TRAF2-MEKK1, and in vivo immunization","pmids":["17143273"],"confidence":"High","gaps":["Whether kinase or E3 activity dominates in B-cell signaling not separated"]},{"year":2010,"claim":"Identified the E3 ligase activity as required for Wnt/β-catenin transcription via Axin1, broadening the ubiquitin-dependent functions of MEKK1.","evidence":"Axin1 IP-MS, co-IP, ligase-dead/kinase-dead mutants, and TCF/LEF reporter assays","pmids":["20128690"],"confidence":"Medium","gaps":["Single lab; relevant ubiquitination substrate in the Wnt pathway not identified"]},{"year":2011,"claim":"Established a developmental intracrine feedback loop in eyelid closure where c-Jun drives Map3k1 transcription and MAP3K1 reactivates JNK-c-Jun/AP-1.","evidence":"ChIP of c-Jun on the Map3k1 promoter, RhoA knockout and Map3k1 hemizygote mice, and pathway phosphorylation readouts","pmids":["21969564"],"confidence":"High","gaps":["Generality of the autoregulatory loop beyond eyelid morphogenesis untested"]},{"year":2014,"claim":"Resolved the E3 mechanism: the PHD motif uses UBE2N to build K63-linked chains on TAB1, controlling TAK1/MAPK responses to specific stimuli.","evidence":"Map3k1(mPHD) knockin ES cells/mice, protein-microarray substrate profiling, K63-linkage ubiquitination assays, and in vitro reconstitution","pmids":["25260751"],"confidence":"High","gaps":["Why hyperosmotic-stress MAPK responses are PHD-independent not explained"]},{"year":2013,"claim":"Linked MAP3K1 mutations to 46,XY disorder of sex development through altered cofactor binding that tips the gonadal SOX9-versus-WNT balance.","evidence":"Transfection of mutant MAP3K1 with cofactor co-IP, downstream phosphorylation, structural domain mapping, and MAP3K4 rescue","pmids":["24135036","30608580"],"confidence":"Medium","gaps":["Mechanistic basis of gain-of-function binding changes only partially defined","In vivo gonadal validation lacking"]},{"year":2018,"claim":"Showed MAP3K1 loss-of-function rewires drug sensitivity by disabling JNK-JUN feedback (sensitizing to MEK inhibitors) and stabilizing IRS-1 (conferring AKT-inhibitor resistance).","evidence":"CRISPR/genetic knockout in cancer cell lines and 168 PDX tumors, DUSP4 siRNA epistasis, and IRS-1/p85 co-IP","pmids":["29795445","29765551"],"confidence":"High","gaps":["Predictive value across tumor types not generalized","Relative contribution of kinase vs E3 loss to these phenotypes not dissected"]},{"year":null,"claim":"How MEKK1 integrates competing upstream activators and partitions output between its kinase and E3 ligase activities to select among JNK, ERK, NF-κB, and ubiquitination programs remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the full-length kinase/E3 protein","Quantitative rules for kinase-vs-ligase output selection unknown","Complete in vivo substrate map of the E3 activity incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,2,3,5]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[1,2,16]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[23,33,28]},{"term_id":"GO:0140097","term_label":"catalytic activity, acting on DNA","supporting_discovery_ids":[23,33]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,16,19]}],"localization":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[8]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[7]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[34]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,3,16]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[4,7,23]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[24,26,11]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[30,31]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[31,35,25]}],"complexes":["IκBα/IKK kinase complex","Han11-DYRK1-HIPK2 complex"],"partners":["MAP2K4","MAP2K1","RIPK1","TRAF2","RHOA","GSK3B","ACTN1","AXIN1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q13233","full_name":"Mitogen-activated protein kinase kinase kinase 1","aliases":["MAPK/ERK kinase kinase 1","MEK kinase 1","MEKK 1"],"length_aa":1512,"mass_kda":164.5,"function":"Component of a protein kinase signal transduction cascade (PubMed:9808624). Activates the ERK and JNK kinase pathways by phosphorylation of MAP2K1 and MAP2K4 (PubMed:9808624). May phosphorylate the MAPK8/JNK1 kinase (PubMed:17761173). Activates CHUK and IKBKB, the central protein kinases of the NF-kappa-B pathway (PubMed:9808624)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q13233/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MAP3K1","classification":"Not Classified","n_dependent_lines":16,"n_total_lines":1208,"dependency_fraction":0.013245033112582781},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MAP3K1","total_profiled":1310},"omim":[{"mim_id":"618068","title":"SPERMATOGENIC LEUCINE ZIPPER PROTEIN 1; SPZ1","url":"https://www.omim.org/entry/618068"},{"mim_id":"616786","title":"MITOGEN-ACTIVATED PROTEIN KINASE-BINDING PROTEIN 1; MAPKBP1","url":"https://www.omim.org/entry/616786"},{"mim_id":"616711","title":"TAO KINASE 3; TAOK3","url":"https://www.omim.org/entry/616711"},{"mim_id":"615814","title":"SERINE/THREONINE/TYROSINE-INTERACTING PROTEIN; STYX","url":"https://www.omim.org/entry/615814"},{"mim_id":"614899","title":"DEAFNESS, AUTOSOMAL RECESSIVE 93; DFNB93","url":"https://www.omim.org/entry/614899"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MAP3K1"},"hgnc":{"alias_symbol":["MEKK","MAPKKK1"],"prev_symbol":["MEKK1"]},"alphafold":{"accession":"Q13233","domains":[{"cath_id":"-","chopping":"303-399_439-483","consensus_level":"medium","plddt":80.1885,"start":303,"end":483},{"cath_id":"1.25.10","chopping":"543-599_628-744","consensus_level":"medium","plddt":88.3175,"start":543,"end":744},{"cath_id":"-","chopping":"746-872","consensus_level":"medium","plddt":85.3879,"start":746,"end":872},{"cath_id":"3.30.200.20","chopping":"1212-1326","consensus_level":"medium","plddt":78.3103,"start":1212,"end":1326},{"cath_id":"1.10.510.10","chopping":"1330-1512","consensus_level":"medium","plddt":88.6962,"start":1330,"end":1512}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13233","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q13233-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q13233-F1-predicted_aligned_error_v6.png","plddt_mean":58.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MAP3K1","jax_strain_url":"https://www.jax.org/strain/search?query=MAP3K1"},"sequence":{"accession":"Q13233","fasta_url":"https://rest.uniprot.org/uniprotkb/Q13233.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q13233/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q13233"}},"corpus_meta":[{"pmid":"7992057","id":"PMC_7992057","title":"Differential activation of ERK and JNK mitogen-activated protein kinases by Raf-1 and MEKK.","date":"1994","source":"Science (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/7992057","citation_count":1056,"is_preprint":false},{"pmid":"7997270","id":"PMC_7997270","title":"Activation of stress-activated protein kinase by MEKK1 phosphorylation of its activator SEK1.","date":"1994","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/7997270","citation_count":719,"is_preprint":false},{"pmid":"9008162","id":"PMC_9008162","title":"Activation of the IkappaB alpha kinase complex by MEKK1, a kinase of the JNK pathway.","date":"1997","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/9008162","citation_count":652,"is_preprint":false},{"pmid":"9244305","id":"PMC_9244305","title":"The regulation of anoikis: MEKK-1 activation requires cleavage by caspases.","date":"1997","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/9244305","citation_count":467,"is_preprint":false},{"pmid":"9689078","id":"PMC_9689078","title":"MEKK1 activates both IkappaB kinase alpha and IkappaB kinase beta.","date":"1998","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/9689078","citation_count":341,"is_preprint":false},{"pmid":"18982020","id":"PMC_18982020","title":"MEKK1, MKK1/MKK2 and MPK4 function together in a mitogen-activated protein kinase cascade to regulate innate immunity in plants.","date":"2008","source":"Cell research","url":"https://pubmed.ncbi.nlm.nih.gov/18982020","citation_count":314,"is_preprint":false},{"pmid":"9630230","id":"PMC_9630230","title":"HTLV-I Tax protein binds to MEKK1 to stimulate IkappaB kinase activity and NF-kappaB activation.","date":"1998","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/9630230","citation_count":225,"is_preprint":false},{"pmid":"8621389","id":"PMC_8621389","title":"Molecular cloning of mitogen-activated protein/ERK kinase kinases (MEKK) 2 and 3. 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\"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — replicated across multiple labs, multiple orthogonal methods (overexpression, dominant-negative, kinase assays), foundational finding confirmed in subsequent work\",\n      \"pmids\": [\"7992057\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"MEKK1 activates the stress-activated protein kinase (SAPK/JNK) pathway by phosphorylating its activator SEK1, which in turn phosphorylates and activates SAPK.\",\n      \"method\": \"Inducible MEKK1 expression in NIH3T3 cells, in vitro kinase assay with SEK1 as substrate\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro kinase assay demonstrating direct phosphorylation of SEK1 by MEKK1, replicated across multiple subsequent studies\",\n      \"pmids\": [\"7997270\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"A constitutively active catalytic domain fragment of MEKK1 (MEKK-C) directly phosphorylates MEK1 at S218 and S222 in vitro; MEKK1 also interacts with MEK1 in the yeast two-hybrid system and activates MEK1/2 in mammalian cells, but does not efficiently activate ERK2 compared to EGF stimulation.\",\n      \"method\": \"In vitro kinase assay with bacterially expressed MEKK-C, yeast two-hybrid, transfection in mammalian cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with phosphosite identification, two-hybrid interaction, and cell-based assay in one study\",\n      \"pmids\": [\"7624324\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"MEKK1 induces site-specific phosphorylation of IκBα in vivo and directly activates the IκBα kinase complex in vitro, placing MEKK1 as a critical component of both the c-Jun and NF-κB stress response pathways.\",\n      \"method\": \"In vitro IκBα kinase activation assay, in vivo phosphorylation assay\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro activation of IκBα kinase complex demonstrated, replicated and extended in subsequent studies\",\n      \"pmids\": [\"9008162\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Caspase cleavage of MEKK1 at a DEVD motif is required for its kinase activation during anoikis; the cleavage product stimulates apoptosis, and a cleavage-resistant MEKK1 mutant partially protects cells from anoikis, establishing a positive feedback loop between caspases and MEKK1.\",\n      \"method\": \"Cleavage-resistant and kinase-inactive MEKK1 mutants, caspase inhibitors, cell death assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple mutants (cleavage-resistant, kinase-inactive), caspase inhibitor controls, functional apoptosis readouts; replicated in subsequent caspase-3 cleavage studies\",\n      \"pmids\": [\"9244305\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"MEKK1 activates both IKK-α and IKK-β in vivo; IKK-α is present in the MEKK1-inducible high molecular weight IκBα kinase complex and MEKK1 treatment induces phosphorylation of IKK-α in vitro.\",\n      \"method\": \"In vitro phosphorylation assays, co-immunoprecipitation, transfection in mammalian cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — in vitro kinase assays combined with co-IP and transfection; confirms and extends earlier IκBα kinase findings\",\n      \"pmids\": [\"9689078\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"HTLV-I Tax protein binds to the amino terminus of MEKK1, stimulates MEKK1 kinase activity, and increases IKKβ-mediated phosphorylation of IκBα, leading to NF-κB activation.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, dominant-negative mutant studies, transfection\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, in vitro kinase assay with recombinant proteins, dominant-negative validation; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"9630230\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Caspase-3 (CPP32) cleaves MEKK1 after residue D68 both in vivo and in vitro during Fas-induced apoptosis; this cleavage redistributes MEKK1 from a Triton-insoluble (particulate) compartment to a Triton-soluble (cytoplasmic) compartment and is required for MEKK1 and SAPK activation during apoptosis but not during rapid stress responses.\",\n      \"method\": \"Sequencing of cleavage products, immunofluorescence, subcellular fractionation, viral and chemical caspase inhibitors\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cleavage site identified by sequencing, subcellular redistribution shown by immunofluorescence and fractionation, caspase inhibitor controls; consistent with parallel finding in PMID 9244305\",\n      \"pmids\": [\"9576928\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"MEKK1 interacts directly with α-actinin via residues 221–559 of its N-terminal regulatory domain, and both endogenous and overexpressed MEKK1 co-localize with α-actinin along actin stress fibers and at focal adhesions; kinase activity is not required for this localization.\",\n      \"method\": \"Yeast two-hybrid screen, co-immunoprecipitation, in vitro binding with purified α-actinin, immunofluorescence colocalization\",\n      \"journal\": \"Cell motility and the cytoskeleton\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid identification, confirmed by reciprocal Co-IP and direct in vitro binding with purified protein, colocalization by immunofluorescence\",\n      \"pmids\": [\"10401575\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"MEKK1 is required for JNK activation in response to microtubule disruption (taxol) but not actin fiber disruption; targeted disruption of MEKK1 in ES cells abolishes JNK activation and increases apoptosis after taxol treatment; MEKK1 expression is elevated 3-fold in mitosis.\",\n      \"method\": \"Targeted gene disruption in embryonic stem cells, JNK kinase assays, cell cycle analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with specific phenotypic readout (JNK activation loss), parallel MEKK2 knockout as specificity control, replicated in subsequent MEKK1-/- studies\",\n      \"pmids\": [\"10212239\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"MEKK-1 activates Smad2-mediated transcription in endothelial cells independently of the C-terminal SSXS motif of Smad2 (the TGF-β receptor phosphorylation site), increases Smad2 phosphorylation state, enhances Smad2-Smad4 interactions, induces nuclear localization of Smad2/Smad4, and stimulates Smad-coactivator interactions.\",\n      \"method\": \"Constitutively active MEKK-1 transfection, Gal4-Smad2 reporter assay, co-immunoprecipitation, nuclear fractionation, shear stress experiment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single lab, multiple reporter and co-IP methods but no direct in vitro phosphorylation of Smad2 by MEKK1 demonstrated\",\n      \"pmids\": [\"10085121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"MEKK1-deficient ES cell-derived cardiac myocytes fail to activate JNK in response to oxidative stress, leading to enhanced TNF-α production and increased apoptosis; the MEKK1-JNK pathway negatively regulates TNF-α production to protect cardiac myocytes.\",\n      \"method\": \"Targeted gene disruption (MEKK1-/- ES cells), JNK and p38 kinase assays, TNF-α ELISA, apoptosis assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with mechanistic pathway dissection (JNK vs p38, TNF-α measurement), multiple orthogonal readouts\",\n      \"pmids\": [\"10611349\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Endogenous MEKK1 physically binds to endogenous ERK2, MEK1, and Raf-1, indicating MEKK1 can scaffold all three kinases of the ERK MAP kinase module.\",\n      \"method\": \"Co-immunoprecipitation of endogenous proteins\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — endogenous co-IP in a single lab; mechanistically informative but single method\",\n      \"pmids\": [\"10969079\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Raf-mediated NF-κB activation is blocked by a dominant-negative form of MEKK1, indicating Raf induces NF-κB via MEKK1 as a membrane shuttle kinase, but not through the classical MEK-ERK cascade.\",\n      \"method\": \"Dominant-negative MEKK1, pharmacological pathway inhibitors, NF-κB reporter assays, transformation assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — dominant-negative approach with pathway inhibitor controls; functional epistasis established but no direct biochemical interaction shown\",\n      \"pmids\": [\"10758165\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Protein kinase G (PKG) directly phosphorylates the N-terminal domain of MEKK1 in vitro, and constitutively active PKG activates JNK1 via a PKG→MEKK1→SEK1→JNK1 pathway; dominant-negative MEKK1 blocks PKG-induced JNK1 activation.\",\n      \"method\": \"In vitro kinase assay with purified PKG and MEKK1, dominant-negative MEKK1, JNK1 activation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vitro phosphorylation demonstrated plus dominant-negative epistasis; single lab\",\n      \"pmids\": [\"11278263\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"RIP (receptor-interacting protein) physically associates with MEKK1 in vitro and in vivo, phosphorylates MEKK1 at Ser-957 and Ser-994, and is required for TNF-α-induced MEKK1 activation; a non-phosphorylatable S957A/S994A MEKK1 mutant fails to be activated by RIP and blocks RIP-induced IKKβ and NF-κB activation.\",\n      \"method\": \"Co-immunoprecipitation, in vitro kinase assay, site-directed mutagenesis, RIP-deficient Jurkat cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct phosphorylation site identification by mutagenesis, co-IP in vitro and in vivo, genetic (RIP-deficient) cell confirmation\",\n      \"pmids\": [\"11369754\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Purified active GCK (germinal center kinase, a Ste20 homologue) and TRAF2 activate recombinant MEKK1 in vitro; autophosphorylation within the MEKK1 kinase domain activation loop is required for activation; GCK promotes MEKK1 oligomerization in vivo, suggesting activation via induced oligomerization and autophosphorylation.\",\n      \"method\": \"In vitro activation assay with purified proteins, forced oligomerization assay, kinase domain mutagenesis, co-immunoprecipitation\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — first in vitro reconstitution of MEKK1 activation using purified proteins; autophosphorylation mechanism supported by mutagenesis\",\n      \"pmids\": [\"11784851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"MEKK1 is required for inducible urokinase-type plasminogen activator (uPA) expression in response to PMA or FGF-2; MEKK1-deficient fibroblasts show greatly reduced uPA expression and activity, which is restored by MEKK1 transfection; this requires MEKK1-dependent MKK1 and JNK activity.\",\n      \"method\": \"MEKK1-/- fibroblasts, re-expression rescue, uPA activity assay, dominant-negative MKK constructs\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with rescue by re-expression, specific pathway dissection with MKK1 and JNK dominant-negatives; MEKK2 knockout as specificity control\",\n      \"pmids\": [\"12493778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"MEKK1 is essential for Gαq-induced cardiac hypertrophy in vivo; MEKK1 knockout abolishes JNK activation, cardiac mass increase, myocyte enlargement, ANF induction, and ventricular dysfunction caused by Gαq overexpression, while other terminal MAPKs are unaffected.\",\n      \"method\": \"MEKK1 gene knockout in mice, ES cell-derived cardiomyocytes, JNK/ERK/p38 kinase assays, echocardiography, histology\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic knockout with selective JNK phenotype (other MAPKs unaffected as controls), multiple physiological readouts\",\n      \"pmids\": [\"11891332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"RhoA, but not Rac or Cdc42, binds to the N-terminal regulatory domain (including the PHD domain) of MEKK1; Rho-GTP stimulates MEKK1 kinase activity up to 10-fold toward MEK4 but does not result in RhoA ubiquitination by MEKK1.\",\n      \"method\": \"GST pulldown, in vitro kinase assay, PHD domain cysteine mutagenesis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct binding and kinase activation demonstrated in vitro with purified proteins, mutagenesis of PHD domain; single lab\",\n      \"pmids\": [\"14581471\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Glycogen synthase kinase 3β (GSK3β) physically associates with endogenous MEKK1 and activates MEKK1 kinase activity; GSK3β-mediated MEKK1 activation is inhibited by insulin via PI3K; MEKK1 activity is reduced in GSK3β-/- fibroblasts and restored by ectopic GSK3β expression.\",\n      \"method\": \"Co-immunoprecipitation of endogenous proteins, in vitro kinase assay, GSK3β knockout fibroblasts, pharmacological inhibition (wortmannin)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — endogenous co-IP, genetic knockout cells with rescue, in vitro kinase assays, pharmacological validation; multiple orthogonal methods\",\n      \"pmids\": [\"12584189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"GST Mu 1-1 (GST M1-1) directly binds MEKK1 and inhibits its kinase activity in vitro; GST M1-1 co-immunoprecipitates with endogenous MEKK1 in L929 cells, interferes with MEKK1-SEK1 binding, and suppresses MEKK1-mediated apoptosis.\",\n      \"method\": \"In vitro binding and kinase assays, endogenous co-immunoprecipitation, co-immunoprecipitation competition assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in vitro binding and inhibition of kinase activity, endogenous Co-IP; single lab\",\n      \"pmids\": [\"15299005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Ceramide directly binds to MEKK1 in glomerular endothelial cells as shown by radioiodinated photoaffinity labeling and ceramide-coupled Sepharose affinity chromatography; this binding activates the SAPK/JNK cascade, which mediates ceramide-induced apoptosis.\",\n      \"method\": \"Photoaffinity labeling with [125I]TID-ceramide, affinity chromatography with ceramide-Sepharose, JNK inhibitor functional assay\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding demonstrated by two independent biochemical methods (photoaffinity and affinity chromatography); single lab\",\n      \"pmids\": [\"15164763\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MEKK1 PHD/RING finger domain exhibits E3 ubiquitin ligase activity toward c-Jun in vitro and in vivo; MEKK1 mediates ubiquitination-dependent degradation of c-Jun in response to osmotic stress, and MEKK1-/- cells show higher c-Jun protein levels; c-Jun downregulation by MEKK1 promotes apoptosis.\",\n      \"method\": \"In vitro ubiquitination assay, MEKK1-/- cell lines, osmotic stress treatment, rescue by c-Jun overexpression\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro E3 ligase reconstitution, genetic knockout confirmation, functional apoptosis rescue; multiple orthogonal methods\",\n      \"pmids\": [\"17101801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MEKK1 is required for CD40-mediated activation of JNK, p38, and c-Jun in B cells; MEKK1 is recruited to CD40 and TRAF2 after CD40 ligation; Map3k1(deltaKD) mice have defective germinal center formation and reduced thymus-dependent antibody production.\",\n      \"method\": \"Map3k1 kinase domain knockin mice, kinase assays, co-immunoprecipitation (CD40-TRAF2-MEKK1), B cell proliferation assays, in vivo immunization\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockin mouse model, co-IP of endogenous proteins, multiple kinase and functional readouts in vivo\",\n      \"pmids\": [\"17143273\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"MEKK1 controls mammary tumor cell dissemination and lung metastasis by regulating urokinase-type plasminogen activator (uPA) expression, gelatinase activity, and cell migration/invasion; MEKK1-/- mice with PyMT mammary tumors show delayed tumor cell dissemination associated with reduced uPA and gelatinase activity and prolonged basement membrane integrity.\",\n      \"method\": \"MEKK1-/- mouse model with PyMT transgene, siRNA knockdown in MDA-MB-231 cells, gelatin zymography, invasion assay, lung metastasis counts\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic knockout and siRNA knockdown with mechanistic pathway readouts (uPA, gelatinase); replicated in human cancer cell line\",\n      \"pmids\": [\"16568086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"MEKK1 is an essential component of antiviral signaling downstream of IPS-1 in the RIG-I-like helicase pathway; forced expression of MEKK1 with IRF3 induces IFN-β, whereas MEKK1 siRNA knockdown inhibits IFN-β induction by poly(I:C); MEKK1 mediates NF-κB and MAPK activation but not IRF3 activation in this pathway.\",\n      \"method\": \"siRNA knockdown, forced expression, IFN-β promoter reporter assay, TRAF6-/- and TAK1-/- MEF comparison\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — siRNA and overexpression with reporter assays; genetic comparison to other pathway components; single lab\",\n      \"pmids\": [\"18984593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MEKK-1 mediates IL-1β-induced increase in intestinal epithelial tight junction permeability through activation of the canonical NF-κB pathway and MLCK gene activation; MEKK-1 knockdown inhibits these effects, while NIK (non-canonical pathway) knockdown does not affect TJ permeability.\",\n      \"method\": \"siRNA knockdown in Caco-2 monolayers, transepithelial resistance measurement, NF-κB pathway inhibitors\",\n      \"journal\": \"The American journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — siRNA with functional barrier readout; pathway specificity shown by NIK vs MEKK-1 comparison; single lab\",\n      \"pmids\": [\"21048223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"MAP3K1 interacts with Axin1; the Axin1-MAP3K1 interaction is induced and modulated by Wnt stimulation; MAP3K1 E3 ubiquitin ligase activity (not kinase activity) is required for Wnt/β-catenin-TCF/LEF transcriptional activity; MAP3K1 siRNA abolishes TCF/LEF-driven transcription and Wnt3A-driven endogenous gene expression.\",\n      \"method\": \"Immunoprecipitation-coupled proteomics (Axin1 IP-MS), co-IP in HEK293T cells, siRNA knockdown, ubiquitin ligase-dead and kinase-dead mutant transfection, TCF reporter assay\",\n      \"journal\": \"Biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics identification confirmed by co-IP, functional mutant analysis with two independent mutations; single lab\",\n      \"pmids\": [\"20128690\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"The WD40-repeat scaffold protein Han11 directly binds MEKK1 in vitro and regulates the threshold and amplitude of MEKK1-triggered stress signaling; Han11 couples MEKK1 to DYRK1 and HIPK2 in a signaling complex; knockdown of Han11 alters the kinetics and amplitude of MEKK1-triggered gene expression.\",\n      \"method\": \"In vitro binding assays, knockdown experiments, reporter assays for MEKK1-triggered gene expression\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding confirmed in vitro, functional consequences of knockdown shown; single lab\",\n      \"pmids\": [\"20940704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MAP3K1 integrates TGF-α/EGFR-RhoA signals and JNK-c-Jun signals during eyelid closure; c-Jun (induced by EGFR-RhoA) binds the Map3k1 promoter in a phosphorylation-independent manner to drive MAP3K1 expression; MAP3K1 then phosphorylates JNK-c-Jun to activate AP-1 and downstream targets (PAI-1), forming an intracrine regulatory loop.\",\n      \"method\": \"ChIP (c-Jun binding to Map3k1 promoter), RhoA knockout mice, Map3k1 hemizygote mice, JNK-c-Jun phosphorylation assays, PAI-1 expression\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP for direct promoter binding, genetic mouse models (RhoA knockout, Map3k1 hemizygote), multiple pathway readouts\",\n      \"pmids\": [\"21969564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MAP3K1 missense mutations causing 46,XY disorder of sex development increase binding of RHOA, MAP3K4, and FRAT1 while reducing SOX9/FGF9/SRY expression and increasing WNT/β-catenin/FOXL2 activity; these effects are partially rescued by co-transfection with wild-type MAP3K4.\",\n      \"method\": \"Cell transfection with wild-type or mutant MAP3K1 in B-lymphoblastoid and NT2/D1 cells, Western blot for phosphorylation of downstream targets, siRNA phenocopying\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-factor binding and downstream phosphorylation shown in cell lines, rescue experiment; gain-of-function nature established but mechanistic detail limited\",\n      \"pmids\": [\"24135036\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"MAP3K1 encodes both a kinase domain and a PHD/RING finger E3 ubiquitin ligase domain; full-length MAP3K1 regulates cell migration and pro-survival signaling, while its caspase-3 cleavage product promotes apoptosis; the E3 ligase domain ubiquitylates c-Jun and ERK1/2.\",\n      \"method\": \"Review synthesizing genetic knockouts, biochemical assays, and ubiquitination assays from multiple studies (not a primary experimental paper, but summarizes established experimental findings)\",\n      \"journal\": \"Genes & cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Strong — review citing multiple independent experimental demonstrations; included because it summarizes validated mechanisms about ERK1/2 ubiquitination (not fully covered elsewhere in corpus)\",\n      \"pmids\": [\"24386504\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The MEKK1 PHD motif functions as an E3 ubiquitin ligase that mediates Lys63-linked poly-ubiquitination of TAB1, using the conjugating enzyme UBE2N; this ubiquitination of TAB1 regulates TAK1 and MAPK (p38 and JNK) activation by TGF-β and EGF; PHD-inactive knockin (Map3k1(mPHD)) cells show defective MAPK responses to TGF-β, EGF, and microtubule disruption but not to hyperosmotic stress.\",\n      \"method\": \"Map3k1(mPHD) knockin ES cells and mice, protein microarray substrate profiling, ubiquitination assays (Lys63 linkage), in vitro E3 ligase reconstitution\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of E3 ligase activity, substrate identification by microarray, linkage specificity (K63), knockin mouse genetics with multiple pathway readouts\",\n      \"pmids\": [\"25260751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"MarvelD3, a tight junction transmembrane component, recruits MEKK1 to junctions; MarvelD3 expression inversely correlates with JNK activity; loss of MarvelD3 increases MEKK1-JNK signaling, cell migration, and proliferation, while re-expression in metastatic cells inhibits these processes.\",\n      \"method\": \"MarvelD3 depletion and re-expression, JNK phosphorylation assays, cell migration and proliferation assays, in vivo tumor formation, MEKK1 co-immunoprecipitation\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional link between MarvelD3-MEKK1 junction recruitment and JNK activation established; Co-IP and multiple cell-based readouts; single lab\",\n      \"pmids\": [\"24567356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Loss-of-function mutations in MAP3K1 disable the JNK-JUN-mediated feedback loop activated by MEK inhibition (via DUSP4 suppression and HER RTK activation), causing sensitivity to MEK inhibitors; this was confirmed in PDX tumor models.\",\n      \"method\": \"Genetic analysis with MEK inhibitor treatment in cancer cell lines and 168 PDX tumors, JNK-JUN pathway readouts, DUSP4 siRNA epistasis\",\n      \"journal\": \"Cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic dissection of JNK-JUN feedback loop, validated in vivo in large PDX cohort, epistasis via DUSP4 siRNA\",\n      \"pmids\": [\"29795445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MAP3K1 disruption enhances AKT phosphorylation and IRS-1 stability, promotes IRS-1 binding to p85 and PI3Kα activity; this results from deficient MAP3K1-JNK signaling increasing IRS-1 stability, thereby conferring resistance to AKT inhibitors.\",\n      \"method\": \"CRISPR knockout of MAP3K1 in PIK3CA-mutant cell lines, Western blot for p-AKT/IRS-1, co-immunoprecipitation (IRS-1/p85), 3D MCF10A models, in vivo xenograft\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR knockout with mechanistic pathway readouts (IRS-1/p85 co-IP, p-AKT), confirmed in vivo; single lab\",\n      \"pmids\": [\"29765551\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MAP3K1 mutations causing 46,XY gonadal dysgenesis cluster in three semi-contiguous domains: an N-terminal Guanine Exchange Factor-homology domain (residues 164–231), a PHD domain (residues 442–495), and an ARMadillo repeat domain (residues 566–862); these mutations increase binding of RHOA, MAP3K4, and FRAT1 and decrease binding of RAC1, with differential effects depending on domain location.\",\n      \"method\": \"Structural modeling, transfection of mutant MAP3K1 constructs, co-immunoprecipitation for co-factor binding, downstream phosphorylation assays\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — domain mapping via structural modeling and co-IP binding assays; consistent with prior functional data but primarily structural/binding characterization in a single study\",\n      \"pmids\": [\"30608580\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MAP3K1 (MEKK1) is a dual-function serine/threonine kinase and PHD/RING-finger E3 ubiquitin ligase that serves as a central signaling hub: its kinase domain phosphorylates SEK1/MKK4/MKK7 to activate the JNK pathway and can also activate MEK1/2-ERK and IKK-NF-κB cascades in response to diverse stimuli including cytokines, growth factors, microtubule disruption, osmotic stress, and apoptotic signals; caspase-3 cleaves MEKK1 at D68 (or a DEVD motif), releasing and activating a C-terminal kinase fragment that amplifies apoptosis via a positive feedback loop; its PHD motif catalyzes K63-linked ubiquitination of substrates including c-Jun, ERK1/2, and TAB1 (using UBE2N) to regulate their stability and TAK1/MAPK activation; the long N-terminal regulatory domain scaffolds interacting proteins including α-actinin, RhoA, GCK/TRAF2, GSK3β, RIP, and Axin1, localizing MEKK1 to stress fibers and focal adhesions and enabling context-dependent pathway selectivity; full-length MAP3K1 supports cell survival, migration, and uPA-dependent invasion, while the caspase-generated fragment promotes apoptosis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MAP3K1 (MEKK1) is a central stress- and survival-signaling hub that couples diverse extracellular and intracellular cues to the JNK, ERK, and NF-\\u03baB cascades through dual kinase and E3 ubiquitin ligase activities [#0, #32]. Its kinase domain directly phosphorylates and activates the JNK activator SEK1/MKK4 [#1], can phosphorylate MEK1 at S218/S222 [#2], and directly activates the I\\u03baB\\u03b1/IKK complex to drive NF-\\u03baB [#3, #5], establishing parallel control of the c-Jun/JNK and NF-\\u03baB stress pathways. Activation requires autophosphorylation in the kinase activation loop and is triggered by oligomerization (GCK/TRAF2), upstream phosphorylation (RIP at S957/S994, PKG, GSK3\\u03b2), and small-GTPase binding (Rho-GTP), with a long N-terminal regulatory domain serving as a scaffold that integrates these inputs [#16, #15, #20, #19]. A distinct PHD/RING domain confers E3 ligase activity that mediates K63-linked ubiquitination of TAB1 via UBE2N to control TAK1/MAPK activation, and ubiquitin-dependent degradation of c-Jun, functions genetically separable from its kinase activity [#33, #23]. The N-terminal domain anchors MEKK1 to \\u03b1-actinin along stress fibers and focal adhesions and to tight junctions, linking it to cytoskeletal context and cell migration [#8, #34]. Functionally, full-length MAP3K1 supports cell survival, migration, and uPA-dependent invasion and metastasis [#17, #25], whereas caspase-3 cleavage at D68/a DEVD motif liberates a C-terminal fragment that amplifies apoptosis through a caspase\\u2013MEKK1 feedback loop [#4, #7]. Genetically, MAP3K1 missense mutations cause 46,XY disorder of sex development by altering cofactor binding (RHOA, MAP3K4, FRAT1) and shifting the SOX9-versus-WNT/\\u03b2-catenin balance in the gonad [#31, #37].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established MEKK1 as a JNK-pathway-selective MAP3K acting downstream of Ras and biochemically distinct from the Raf\\u2192ERK route, defining two parallel Ras-dependent MAPK cascades.\",\n      \"evidence\": \"Dominant-negative and overexpression constructs plus in vitro kinase assays showing direct phosphorylation of SEK1, in mammalian cells\",\n      \"pmids\": [\"7992057\", \"7997270\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous physiological stimuli not yet defined\", \"ERK activation only under overexpression, leaving native ERK role ambiguous\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Showed MEKK1 can directly phosphorylate MEK1 at its activating sites, raising the question of pathway selectivity between JNK and ERK modules.\",\n      \"evidence\": \"In vitro kinase assay with bacterial MEKK-C, yeast two-hybrid, and transfection\",\n      \"pmids\": [\"7624324\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Inefficient ERK2 activation vs EGF leaves physiological relevance of MEK1 phosphorylation unclear\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Extended MEKK1 beyond JNK to the NF-\\u03baB axis by demonstrating direct activation of the I\\u03baB\\u03b1 kinase complex, positioning it at the junction of two stress pathways.\",\n      \"evidence\": \"In vitro IKK activation assay and in vivo I\\u03baB\\u03b1 phosphorylation\",\n      \"pmids\": [\"9008162\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a single kinase selects JNK vs NF-\\u03baB output not resolved\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Revealed a caspase\\u2013MEKK1 positive feedback loop in which caspase cleavage activates MEKK1 to amplify apoptosis, distinguishing pro-apoptotic from survival functions.\",\n      \"evidence\": \"Cleavage-resistant and kinase-inactive mutants with caspase inhibitors and anoikis assays\",\n      \"pmids\": [\"9244305\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise cleavage site refined later\", \"Balance between survival and apoptotic outputs context-dependent and not quantified\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Mapped the apoptotic cleavage to caspase-3 at D68 and linked it to subcellular redistribution, clarifying how cleavage repartitions MEKK1 activity.\",\n      \"evidence\": \"Cleavage-product sequencing, immunofluorescence, and subcellular fractionation with caspase inhibitors during Fas-induced apoptosis\",\n      \"pmids\": [\"9576928\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of particulate-to-soluble redistribution not mechanistically dissected\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Defined IKK-\\u03b1 and IKK-\\u03b2 as MEKK1 targets and identified viral Tax as an N-terminus-binding activator, showing the regulatory domain controls NF-\\u03baB output.\",\n      \"evidence\": \"In vitro phosphorylation, co-IP of the IKK complex, and Tax dominant-negative studies\",\n      \"pmids\": [\"9689078\", \"9630230\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and assembly of the high-MW IKK complex incompletely defined\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified the N-terminal domain as a cytoskeletal scaffold by mapping direct \\u03b1-actinin binding and localization to stress fibers/focal adhesions independent of kinase activity.\",\n      \"evidence\": \"Yeast two-hybrid, reciprocal co-IP, in vitro binding with purified \\u03b1-actinin, and immunofluorescence colocalization\",\n      \"pmids\": [\"10401575\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling consequence of cytoskeletal anchoring not yet linked to pathway output\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Genetic knockouts established a non-redundant requirement for MEKK1 in JNK activation by specific stresses (microtubule disruption, oxidative stress) and in cytoprotection.\",\n      \"evidence\": \"Targeted disruption in ES cells and cardiac myocytes with JNK/p38 kinase assays, TNF-\\u03b1 measurement, and apoptosis readouts\",\n      \"pmids\": [\"10212239\", \"10611349\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stimulus-selectivity mechanism (why some stresses require MEKK1 and others do not) unexplained\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Suggested MEKK1 can scaffold the entire ERK module and relay Raf-induced NF-\\u03baB, expanding its role from kinase to multi-pathway organizer.\",\n      \"evidence\": \"Endogenous co-IP of ERK2/MEK1/Raf-1 and dominant-negative epistasis in NF-\\u03baB reporter assays\",\n      \"pmids\": [\"10969079\", \"10758165\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Co-IP and epistasis only; no direct biochemical demonstration of scaffolding stoichiometry\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Provided the first in vitro reconstitution of MEKK1 activation, defining oligomerization-induced activation-loop autophosphorylation by GCK/TRAF2 as the core activation mechanism.\",\n      \"evidence\": \"In vitro activation with purified GCK and TRAF2, forced-oligomerization assay, and kinase-domain mutagenesis\",\n      \"pmids\": [\"11784851\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Endogenous triggers of oligomerization in specific pathways not enumerated\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Connected MEKK1 to physiology and disease by showing it is essential for G\\u03b1q-induced cardiac hypertrophy and for inducible uPA expression driving invasion.\",\n      \"evidence\": \"MEKK1 knockout mice/ES-derived cardiomyocytes and MEKK1-/- fibroblasts with rescue, plus uPA activity assays and MKK/JNK dominant-negatives\",\n      \"pmids\": [\"11891332\", \"12493778\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct substrates linking JNK to uPA transcription not identified\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Mapped multiple direct upstream activators (RIP phosphorylation, RhoA-GTP binding, GSK3\\u03b2) onto the regulatory domain, explaining context-dependent activation.\",\n      \"evidence\": \"Co-IP, in vitro kinase assays with purified proteins, site-directed mutagenesis, GST pulldown, and knockout-cell rescue\",\n      \"pmids\": [\"11369754\", \"14581471\", \"12584189\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How competing activator inputs are integrated into distinct outputs unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined the PHD/RING domain as a functional E3 ligase, with c-Jun ubiquitination/degradation as a kinase-independent output controlling apoptosis.\",\n      \"evidence\": \"In vitro ubiquitination reconstitution, MEKK1-/- cells, and rescue under osmotic stress\",\n      \"pmids\": [\"17101801\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full substrate repertoire of the E3 activity not yet defined at this stage\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrated an in vivo immune role via CD40/TRAF2 recruitment driving JNK/p38/c-Jun and germinal center formation.\",\n      \"evidence\": \"Map3k1 kinase-domain knockin mice, co-IP of CD40-TRAF2-MEKK1, and in vivo immunization\",\n      \"pmids\": [\"17143273\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether kinase or E3 activity dominates in B-cell signaling not separated\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified the E3 ligase activity as required for Wnt/\\u03b2-catenin transcription via Axin1, broadening the ubiquitin-dependent functions of MEKK1.\",\n      \"evidence\": \"Axin1 IP-MS, co-IP, ligase-dead/kinase-dead mutants, and TCF/LEF reporter assays\",\n      \"pmids\": [\"20128690\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; relevant ubiquitination substrate in the Wnt pathway not identified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Established a developmental intracrine feedback loop in eyelid closure where c-Jun drives Map3k1 transcription and MAP3K1 reactivates JNK-c-Jun/AP-1.\",\n      \"evidence\": \"ChIP of c-Jun on the Map3k1 promoter, RhoA knockout and Map3k1 hemizygote mice, and pathway phosphorylation readouts\",\n      \"pmids\": [\"21969564\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generality of the autoregulatory loop beyond eyelid morphogenesis untested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Resolved the E3 mechanism: the PHD motif uses UBE2N to build K63-linked chains on TAB1, controlling TAK1/MAPK responses to specific stimuli.\",\n      \"evidence\": \"Map3k1(mPHD) knockin ES cells/mice, protein-microarray substrate profiling, K63-linkage ubiquitination assays, and in vitro reconstitution\",\n      \"pmids\": [\"25260751\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why hyperosmotic-stress MAPK responses are PHD-independent not explained\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Linked MAP3K1 mutations to 46,XY disorder of sex development through altered cofactor binding that tips the gonadal SOX9-versus-WNT balance.\",\n      \"evidence\": \"Transfection of mutant MAP3K1 with cofactor co-IP, downstream phosphorylation, structural domain mapping, and MAP3K4 rescue\",\n      \"pmids\": [\"24135036\", \"30608580\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic basis of gain-of-function binding changes only partially defined\", \"In vivo gonadal validation lacking\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed MAP3K1 loss-of-function rewires drug sensitivity by disabling JNK-JUN feedback (sensitizing to MEK inhibitors) and stabilizing IRS-1 (conferring AKT-inhibitor resistance).\",\n      \"evidence\": \"CRISPR/genetic knockout in cancer cell lines and 168 PDX tumors, DUSP4 siRNA epistasis, and IRS-1/p85 co-IP\",\n      \"pmids\": [\"29795445\", \"29765551\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Predictive value across tumor types not generalized\", \"Relative contribution of kinase vs E3 loss to these phenotypes not dissected\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How MEKK1 integrates competing upstream activators and partitions output between its kinase and E3 ligase activities to select among JNK, ERK, NF-\\u03baB, and ubiquitination programs remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the full-length kinase/E3 protein\", \"Quantitative rules for kinase-vs-ligase output selection unknown\", \"Complete in vivo substrate map of the E3 activity incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 2, 3, 5]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [1, 2, 16]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [23, 33, 28]},\n      {\"term_id\": \"GO:0140097\", \"supporting_discovery_ids\": [23, 33]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 16, 19]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [8]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [34]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 3, 16]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [4, 7, 23]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [24, 26, 11]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [30, 31]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [31, 35, 25]}\n    ],\n    \"complexes\": [\"I\\u03baB\\u03b1/IKK kinase complex\", \"Han11-DYRK1-HIPK2 complex\"],\n    \"partners\": [\"MAP2K4\", \"MAP2K1\", \"RIPK1\", \"TRAF2\", \"RHOA\", \"GSK3B\", \"ACTN1\", \"AXIN1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}