{"gene":"DUSP9","run_date":"2026-06-09T23:54:42","timeline":{"discoveries":[{"year":1997,"finding":"MKP-4/DUSP9 is a dual-specificity phosphatase that catalyzes vanadate-sensitive dephosphorylation of p-nitrophenyl phosphate and directly inactivates purified ERK2 in vitro. When expressed in COS-7 cells, it inactivates MAP kinases with selectivity ERK > p38 = JNK/SAPK. It contains two N-terminal CH2 domains homologous to Cdc25 and the extended active-site motif VXVHCXAGXSRSXTX3AYLM conserved in dual-specificity phosphatases. Immunocytochemical analysis showed MKP-4 to be predominantly cytosolic, with punctate nuclear staining co-localizing with promyelocytic protein in a subpopulation of cells.","method":"In vitro phosphatase assay with purified ERK2, COS-7 cell overexpression, immunocytochemistry, Northern analysis, chromosomal localization","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic reconstitution with purified substrate plus cellular overexpression, foundational characterization paper replicated by subsequent studies","pmids":["9030581"],"is_preprint":false},{"year":2005,"finding":"MKP-4/DUSP9 and an MKP-4/p38 complex purified via baculovirus expression both exhibit phosphatase activity toward surrogate substrates; the MKP-4/p38 complex provides substantially higher phosphatase activity than MKP-4 alone, demonstrating that p38 binding activates DUSP9 catalysis, analogous to the activation of MKP-3 by ERK2.","method":"Baculovirus expression, affinity and gel-filtration purification, in vitro spectrophotometric and fluorescence phosphatase assays with kinetic parameter determination","journal":"Bioorganic chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with purified protein complex and kinetic characterization; single lab but multiple substrate assays","pmids":["15668181"],"is_preprint":false},{"year":2005,"finding":"DUSP9 knockout (X-linked gene; paternal X inactivated in extraembryonic tissues) in mice causes embryonic lethality due to failure of placental labyrinth development. The lethal phenotype maps specifically to trophoblast giant cells and labyrinth where DUSP9 is normally expressed. When the placental defect was rescued, DUSP9-null male embryos developed normally and were fertile, indicating DUSP9 is essential for placental organogenesis but dispensable for embryonic development.","method":"Gene targeting (knockout mouse), histological analysis of embryos 8–10.5 dpc, placental rescue experiments","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic KO with defined developmental phenotype, placental rescue experiment, replicated by independent pre-eclampsia study","pmids":["16135819"],"is_preprint":false},{"year":2008,"finding":"Overexpression of MKP-4/DUSP9 in 3T3-L1 adipocytes inhibits ERK and JNK phosphorylation and, to a lesser extent, p38 phosphorylation, thereby preventing anisomycin-induced IRS-1 Ser307 phosphorylation. This restores insulin-stimulated IRS-1 tyrosine phosphorylation, IRS-1 docking with PI3K, and Akt phosphorylation, and reverses TNF-α-induced inhibition of insulin signaling and glucose uptake. Adenoviral overexpression in ob/ob mouse liver decreased ERK and JNK phosphorylation, reducing glycemia and improving glucose tolerance.","method":"Stable overexpression in 3T3-L1 cells, immunoblotting for phospho-ERK/JNK/p38/IRS-1/Akt, PI3K co-immunoprecipitation, glucose uptake assay, adenoviral hepatic overexpression in ob/ob mice","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal signaling readouts in both cell and in vivo models, multiple orthogonal methods establishing pathway position","pmids":["18296638"],"is_preprint":false},{"year":2010,"finding":"Crystal structure of the DUSP9/MKP-4 catalytic domain (MKP-4C) resolved at 2.7 Å reveals significant deviations from canonical DUSP active conformations, with notable gaps between the catalytic core and surrounding loops. Virtual library screening identified inhibitor-binding sites near these gaps distinct from the active site, suggesting allosteric inhibition could prevent transition to the fully active conformation.","method":"X-ray crystallography at 2.7 Å resolution, virtual library screening","journal":"Acta crystallographica. Section D, Biological crystallography","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure determination is Tier 1; structural deviation from canonical DUSP conformation identified; single lab","pmids":["21206059"],"is_preprint":false},{"year":2017,"finding":"DUSP9 is upregulated in female compared to male mouse ESCs due to its X-linked location (two active X chromosomes in female ESCs). Heterozygous loss of DUSP9 in female ESCs leads to male-like (hypermethylated) DNA methylation levels genome-wide. Cell fusion experiments showed that the ratio of X chromosomes to autosomes dictates methylation levels, placing DUSP9 as a mediator of X-dosage-dependent epigenetic regulation.","method":"Genome-wide methylation profiling, cell fusion experiments, CRISPR-mediated heterozygous DUSP9 deletion in female ESCs, RNA-seq","journal":"Cell stem cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with defined epigenetic phenotype, cell fusion epistasis, multiple orthogonal genomic methods","pmids":["28366588"],"is_preprint":false},{"year":2018,"finding":"In triple-negative breast cancer, HIF-1 transcriptionally induces DUSP9 expression in response to chemotherapy, leading to ERK dephosphorylation/inhibition. This ERK inhibition causes decreased inactivating phosphorylation of FoxO3, driving transcriptional induction of pluripotency factor Nanog and promoting breast cancer stem cell specification.","method":"siRNA knockdown of HIF1/DUSP9 in TNBC cells, immunoblotting for phospho-ERK/FoxO3, Nanog reporter assays, mammosphere formation, ALDH flow cytometry","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic knockdown with mechanistic pathway readouts, single lab, multiple orthogonal assays but no in vitro reconstitution","pmids":["29880481"],"is_preprint":false},{"year":2019,"finding":"ERK1/2 were identified as direct binding partners of MKP-4/DUSP9 by immunoprecipitation-mass spectrometry. MKP-4 negatively regulates ERK1/2 phosphorylation and reduces downstream CyclinD1 and c-Myc expression in hepatocellular carcinoma cells. Knockdown of MKP-4 increases cell proliferation and cancer stem cell traits, while upregulation of MKP-4 or ERK1/2 inhibitor treatment reverses these effects.","method":"Immunoprecipitation-mass spectrometry (IP-MS), western blot, colony formation, EdU incorporation, sphere formation assays, xenograft tumor models","journal":"Cancer cell international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — IP-MS for binding partner identification plus functional KD/OE in cells and in vivo; single lab","pmids":["30923463"],"is_preprint":false},{"year":2015,"finding":"DUSP9/MKP-4 is constitutively expressed in mouse plasmacytoid dendritic cells (pDCs) but not conventional DCs, and its expression correlates with impaired ERK1/2 phosphorylation upon TLR9 stimulation. Enforced retroviral expression of Dusp9 in GM-CSF-induced cDCs increased TLR9-induced IL-12p40 and IFN-β but not IL-10. Conditional deletion of Dusp9 in pDCs did not restore ERK1/2 activation after TLR9 stimulation and only weakly affected IFN-β and IL-12p40 production, indicating Dusp9 is sufficient but not essential for high-level IFN-β production in pDCs.","method":"Transcriptome analysis, retroviral overexpression in cDCs, conditional knockout (Dusp9flox/flox; CD11c-Cre), ELISA for cytokines, flow cytometry for phospho-ERK","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function and conditional KO, multiple cytokine readouts; single lab; KO result was weakly negative for IFN-β","pmids":["26170386"],"is_preprint":false},{"year":2022,"finding":"DUSP9 directly binds to apoptosis signal-regulating kinase 1 (ASK1) and inhibits ASK1 phosphorylation, thereby decreasing TRAF6 levels, K63-linked ubiquitination, and downstream p38/JNK1 (but not ERK1) phosphorylation in hepatic ischemia/reperfusion injury. This mechanism is distinct from canonical ERK-focused DUSP9 activity.","method":"Co-immunoprecipitation (DUSP9–ASK1 binding), western blot for phospho-ASK1/p38/JNK1/ERK1, TRAF6/ubiquitin immunoprecipitation, adenoviral overexpression and siRNA knockdown in vivo and in vitro","journal":"Acta biochimica et biophysica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for direct binding, functional gain/loss experiments with mechanistic readouts; single lab","pmids":["36789693"],"is_preprint":false},{"year":2024,"finding":"HDAC9 represses DUSP9 expression by deacetylating histone H4K12 (H4K12ac) at the DUSP9 promoter, thereby activating downstream MAPK signaling and promoting particulate matter-induced airway inflammation. HDAC9 upregulation is mediated upstream by the METTL3/m6A/IGF2BP3 pathway acting on HDAC9 mRNA.","method":"ChIP for H4K12ac at DUSP9 promoter, siRNA knockdown of HDAC9/DUSP9, western blot for MAPK pathway, in vivo mouse airway inflammation model","journal":"Journal of hazardous materials","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP establishes epigenetic writing mechanism at DUSP9 promoter; functional knockdown with MAPK readout; single lab","pmids":["39088948"],"is_preprint":false},{"year":2025,"finding":"DUSP9 directly interacts with insulin receptor substrate 1 (IRS1) and inhibits IRS1 phosphorylation at Tyr632, impairing downstream IRS1/PI3K/AKT insulin signaling. This interaction was demonstrated by co-immunoprecipitation and pull-down assays in high-glucose-treated trophoblast cells, and DUSP9 knockdown in a GDM mouse model restored IRS1/PI3K/AKT pathway activation.","method":"Co-immunoprecipitation, pull-down assay, western blot for phospho-IRS1(Tyr632)/PI3K/AKT, lentivirus-mediated shRNA knockdown in GDM mouse model","journal":"Human immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and pull-down for direct binding, in vivo KD with defined phosphorylation readout; single lab","pmids":["40020430"],"is_preprint":false},{"year":2025,"finding":"DUSP9 dephosphorylates STAT3 to negatively regulate PD-L1 expression in tumor cells. Mechanistic experiments showed that DUSP9 overexpression reduced phospho-STAT3 levels, leading to decreased PD-L1 transcription, while DUSP9 knockdown increased PD-L1 expression. Combining DUSP9 targeting with anti-PD-1 antibody enhanced therapeutic sensitivity in syngeneic tumor models.","method":"DUSP9 overexpression/knockdown, immunoblotting for phospho-STAT3 and PD-L1, syngeneic tumor models with anti-PD-1 combination","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain-of-function and loss-of-function with mechanistic phosphorylation readout for STAT3; single lab, no in vitro phosphatase reconstitution with STAT3","pmids":["41405398"],"is_preprint":false},{"year":2025,"finding":"FBXO3 E3 ubiquitin ligase directly interacts with DUSP9 and promotes its ubiquitination and degradation, thereby activating the MAPK pathway and maintaining leukemia stem cell activity in CML. DUSP9 knockdown partially reverses the LSC elimination caused by FBXO3 deficiency, placing DUSP9 downstream of FBXO3 in this pathway.","method":"Co-immunoprecipitation (FBXO3–DUSP9 interaction), ubiquitination assay, FBXO3 KO/DUSP9 KD in CML cell lines and primary LSCs, in vivo LSC models","journal":"Cell reports. Medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for binding, ubiquitination assay for PTM mechanism, epistasis by double KO/KD; single lab","pmids":["41850237"],"is_preprint":false},{"year":2025,"finding":"Caffeine directly targets DUSP9 (identified by surface plasmon resonance, CETSA, and DARTS assays) and restores hepatic DUSP9 expression reduced by high-fat/high-carbohydrate diet. DUSP9 knockdown in vivo counteracted the therapeutic effects of caffeine on MASH, including glycolipid metabolism disorders. The downstream mechanism involves DUSP9-mediated inactivation of the ASK1-p38/JNK signaling pathway.","method":"Surface plasmon resonance (SPR), CETSA, DARTS for direct target identification; DUSP9 knockdown in vivo; western blot for ASK1/p38/JNK; metabolic phenotyping in MASH mouse models","journal":"Redox biology","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — three orthogonal direct binding assays (SPR, CETSA, DARTS) establish physical interaction; in vivo functional validation; single lab","pmids":["39879738"],"is_preprint":false},{"year":2020,"finding":"DUSP9 suppresses proliferation and migration of clear cell renal cell carcinoma cells and inhibits phosphorylation of mTOR and expression of downstream mTOR pathway proteins Sox2, c-Myc, and HIF-1α. This was confirmed by in vitro assays and xenograft tumor models.","method":"DUSP9 overexpression in ccRCC cell lines, western blot for p-mTOR/Sox2/c-Myc/HIF-1α, CCK-8 proliferation, wound-healing and transwell migration assays, nude mouse xenograft","journal":"OncoTargets and therapy","confidence":"Low","confidence_rationale":"Tier 3 / Weak — overexpression with downstream signaling readout; no direct biochemical demonstration of DUSP9–mTOR interaction; single lab, single approach","pmids":["32103999"],"is_preprint":false}],"current_model":"DUSP9/MKP-4 is an X-linked cytoplasmic dual-specificity MAP kinase phosphatase that dephosphorylates ERK1/2 (preferred substrate), p38, JNK, and ASK1 by targeting both phospho-threonine and phospho-tyrosine residues; its catalytic activity is allosterically enhanced by substrate (p38) binding, it is subject to FBXO3-mediated ubiquitination and HDAC9-mediated epigenetic silencing, it directly interacts with IRS1 to modulate insulin signaling, and it dephosphorylates STAT3 to suppress PD-L1 expression, with its essential physiological role in placental labyrinth development established by knockout studies in mice."},"narrative":{"mechanistic_narrative":"DUSP9/MKP-4 is a predominantly cytosolic dual-specificity MAP kinase phosphatase that inactivates MAP kinases with a substrate preference of ERK > p38 = JNK by dephosphorylating both phospho-threonine and phospho-tyrosine residues, establishing it as a negative regulator of MAPK signaling [PMID:9030581]. Its catalytic activity is allosterically enhanced upon substrate binding, as the MKP-4/p38 complex displays substantially higher phosphatase activity than the enzyme alone [PMID:15668181], and crystallography of the catalytic domain shows deviations from canonical active DUSP conformations consistent with a regulated transition to full activity [PMID:21206059]. Beyond canonical MAPK targets, DUSP9 directly binds ASK1 to suppress its phosphorylation and downstream TRAF6/p38/JNK signaling [PMID:36789693], directly engages IRS1 to inhibit Tyr632 phosphorylation and dampen IRS1/PI3K/AKT insulin signaling [PMID:40020430], and dephosphorylates STAT3 to repress PD-L1 transcription in tumor cells [PMID:41405398]. Through these activities DUSP9 functions as a brake on MAPK-driven proliferation and stemness in multiple cancers, suppressing ERK-dependent CyclinD1/c-Myc output [PMID:30923463] and breast cancer stem cell specification [PMID:29880481], and its loss is restrained by FBXO3-mediated ubiquitination and degradation that reactivates MAPK signaling in leukemia stem cells [PMID:41850237] and by HDAC9-mediated promoter deacetylation that silences DUSP9 [PMID:39088948]. Genetically, DUSP9 is X-linked and essential for placental labyrinth development, with knockout causing embryonic lethality through a trophoblast/labyrinth defect while embryos rescued of the placental defect develop normally [PMID:16135819], and its X-dosage-dependent expression mediates epigenetic control of genome-wide DNA methylation in embryonic stem cells [PMID:28366588].","teleology":[{"year":1997,"claim":"Established DUSP9 as a bona fide dual-specificity phosphatase that directly inactivates MAP kinases, defining its core enzymatic identity and substrate hierarchy.","evidence":"in vitro phosphatase assays with purified ERK2 and MAPK inactivation in COS-7 cells, plus immunocytochemistry and chromosomal mapping","pmids":["9030581"],"confidence":"High","gaps":["Quantitative kinetics toward p38/JNK not resolved","Physiological substrate context in vivo not addressed"]},{"year":2005,"claim":"Showed DUSP9 catalysis is substrate-activated, explaining how its phosphatase activity is allosterically tuned by binding its kinase substrate.","evidence":"baculovirus-expressed MKP-4 and MKP-4/p38 complex with kinetic phosphatase assays on surrogate substrates","pmids":["15668181"],"confidence":"High","gaps":["Structural basis of activation not defined here","Whether ERK binding activates similarly not tested in this study"]},{"year":2005,"claim":"Defined an essential, non-redundant physiological role for DUSP9 in placental organogenesis via X-linked gene targeting.","evidence":"knockout mouse with histological embryo analysis and placental rescue experiments","pmids":["16135819"],"confidence":"High","gaps":["Which MAPK substrate dysregulation drives the labyrinth defect not pinpointed","Cell-autonomous trophoblast mechanism not dissected"]},{"year":2008,"claim":"Positioned DUSP9 as a regulator of insulin signaling by suppressing stress-kinase-mediated IRS-1 inhibition, linking MAPK phosphatase activity to glucose homeostasis.","evidence":"stable/adenoviral overexpression in adipocytes and ob/ob liver with insulin-pathway immunoblotting and glucose tolerance","pmids":["18296638"],"confidence":"High","gaps":["Direct DUSP9 binding to IRS-1 not shown in this study","Loss-of-function metabolic phenotype not tested"]},{"year":2010,"claim":"Provided a structural framework showing the catalytic domain adopts a non-canonical conformation, rationalizing allosteric regulation and inhibitor design.","evidence":"X-ray crystallography at 2.7 Å with virtual library screening","pmids":["21206059"],"confidence":"High","gaps":["Substrate-bound active conformation not captured","Predicted allosteric inhibitor sites not experimentally validated"]},{"year":2017,"claim":"Identified DUSP9 as the X-dosage-sensitive mediator coupling X-chromosome number to genome-wide DNA methylation levels in ESCs.","evidence":"CRISPR heterozygous deletion, cell fusion epistasis, and genome-wide methylation/RNA-seq","pmids":["28366588"],"confidence":"High","gaps":["Molecular path from DUSP9 to the methylation machinery not defined","Relevance to human X-dosage compensation not established here"]},{"year":2015,"claim":"Tested DUSP9's role in innate immune MAPK control, showing it is sufficient but not essential for dampening ERK and shaping pDC cytokine output.","evidence":"retroviral overexpression in cDCs and conditional knockout in pDCs with cytokine ELISA and phospho-ERK flow cytometry","pmids":["26170386"],"confidence":"Medium","gaps":["Conditional KO failed to restore ERK activation, indicating redundancy","Compensating phosphatases not identified"]},{"year":2018,"claim":"Placed DUSP9 within a HIF-1-driven chemotherapy response that promotes breast cancer stem cells through ERK/FoxO3/Nanog signaling.","evidence":"siRNA knockdown in TNBC cells with phospho-ERK/FoxO3 immunoblotting, Nanog reporter, mammosphere and ALDH assays","pmids":["29880481"],"confidence":"Medium","gaps":["Direct DUSP9 dephosphorylation of ERK in this context not reconstituted","Single lab, no in vivo confirmation of stemness axis"]},{"year":2019,"claim":"Confirmed ERK1/2 as direct DUSP9 binding partners and established a tumor-suppressive role in hepatocellular carcinoma proliferation and stemness.","evidence":"IP-MS for binding, knockdown/overexpression with colony/EdU/sphere assays and xenografts","pmids":["30923463"],"confidence":"Medium","gaps":["Binding stoichiometry and dephosphorylation kinetics not quantified","Single lab"]},{"year":2022,"claim":"Expanded DUSP9 substrate scope beyond MAPKs by showing direct binding and inhibition of ASK1, defining a non-canonical p38/JNK-selective branch.","evidence":"Co-IP for DUSP9–ASK1 binding with phospho-ASK1/p38/JNK immunoblotting and TRAF6/ubiquitin IP in hepatic I/R models","pmids":["36789693"],"confidence":"Medium","gaps":["Direct dephosphorylation of ASK1 not reconstituted in vitro","Reciprocal validation of binding limited to single Co-IP"]},{"year":2024,"claim":"Defined an upstream epigenetic silencing mechanism whereby HDAC9 deacetylates H4K12 at the DUSP9 promoter to derepress MAPK signaling in airway inflammation.","evidence":"ChIP for H4K12ac at DUSP9 promoter, HDAC9/DUSP9 knockdown, MAPK immunoblotting and in vivo airway model","pmids":["39088948"],"confidence":"Medium","gaps":["Direct HDAC9 occupancy versus indirect effects not fully separated","Single lab"]},{"year":2025,"claim":"Demonstrated direct DUSP9–IRS1 interaction and Tyr632 dephosphorylation, providing the binding mechanism underlying its insulin-signaling control in gestational diabetes.","evidence":"Co-IP and pull-down in trophoblast cells with phospho-IRS1/PI3K/AKT immunoblotting and shRNA knockdown in GDM mice","pmids":["40020430"],"confidence":"Medium","gaps":["Whether DUSP9 directly dephosphorylates IRS1 versus acting via kinases not resolved","Single lab"]},{"year":2025,"claim":"Identified STAT3 as a DUSP9 target controlling PD-L1 transcription, linking DUSP9 to tumor immune evasion and checkpoint therapy sensitivity.","evidence":"DUSP9 overexpression/knockdown with phospho-STAT3 and PD-L1 immunoblotting and anti-PD-1 syngeneic tumor models","pmids":["41405398"],"confidence":"Medium","gaps":["No in vitro phosphatase reconstitution with STAT3","Direct versus indirect dephosphorylation not distinguished"]},{"year":2025,"claim":"Established FBXO3-mediated ubiquitination and degradation as the post-translational control that limits DUSP9 to sustain MAPK-driven leukemia stem cell activity.","evidence":"Co-IP, ubiquitination assay, and FBXO3 KO/DUSP9 KD epistasis in CML lines, primary LSCs, and in vivo models","pmids":["41850237"],"confidence":"Medium","gaps":["Ubiquitination site on DUSP9 not mapped","Single lab"]},{"year":2025,"claim":"Identified DUSP9 as a small-molecule (caffeine) target whose restoration ameliorates metabolic disease through ASK1-p38/JNK inactivation.","evidence":"SPR, CETSA, and DARTS direct binding assays plus in vivo DUSP9 knockdown and MAPK immunoblotting in MASH models","pmids":["39879738"],"confidence":"Medium","gaps":["Caffeine binding site on DUSP9 not structurally defined","Single lab"]},{"year":null,"claim":"How DUSP9's substrate selectivity, allosteric activation, and degradation are integrated to assign it to canonical ERK versus non-canonical ASK1/IRS1/STAT3 branches in a given cell type remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified structural model of substrate-bound active DUSP9","Direct in vitro dephosphorylation not reconstituted for ASK1, IRS1, or STAT3","Tissue-specific determinants of substrate choice unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,9,11,12]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,7,9]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,3,9]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2]},{"term_id":"R-HSA-4839726","term_label":"Chromatin organization","supporting_discovery_ids":[5,10]}],"complexes":[],"partners":["MAPK1","MAPK3","MAP3K5","IRS1","STAT3","FBXO3","MAPK14"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q99956","full_name":"Dual specificity protein phosphatase 9","aliases":["Mitogen-activated protein kinase phosphatase 4","MAP kinase phosphatase 4","MKP-4"],"length_aa":384,"mass_kda":41.9,"function":"Inactivates MAP kinases. Has a specificity for the ERK family","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q99956/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/DUSP9","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/DUSP9","total_profiled":1310},"omim":[{"mim_id":"607175","title":"DUAL-SPECIFICITY PHOSPHATASE 16; DUSP16","url":"https://www.omim.org/entry/607175"},{"mim_id":"300134","title":"DUAL-SPECIFICITY PHOSPHATASE 9; DUSP9","url":"https://www.omim.org/entry/300134"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Endoplasmic reticulum","reliability":"Approved"}],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"kidney","ntpm":52.1},{"tissue":"placenta","ntpm":68.3}],"url":"https://www.proteinatlas.org/search/DUSP9"},"hgnc":{"alias_symbol":["MKP-4","MKP4"],"prev_symbol":[]},"alphafold":{"accession":"Q99956","domains":[{"cath_id":"3.40.250.10","chopping":"6-86_103-142","consensus_level":"high","plddt":85.7864,"start":6,"end":142},{"cath_id":"3.90.190.10","chopping":"206-350","consensus_level":"high","plddt":95.4941,"start":206,"end":350}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q99956","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q99956-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q99956-F1-predicted_aligned_error_v6.png","plddt_mean":75.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=DUSP9","jax_strain_url":"https://www.jax.org/strain/search?query=DUSP9"},"sequence":{"accession":"Q99956","fasta_url":"https://rest.uniprot.org/uniprotkb/Q99956.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q99956/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q99956"}},"corpus_meta":[{"pmid":"9030581","id":"PMC_9030581","title":"Molecular cloning and functional characterization of a novel mitogen-activated protein kinase phosphatase, MKP-4.","date":"1997","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9030581","citation_count":135,"is_preprint":false},{"pmid":"18296638","id":"PMC_18296638","title":"Overexpression of the dual-specificity phosphatase MKP-4/DUSP-9 protects against stress-induced insulin resistance.","date":"2008","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/18296638","citation_count":96,"is_preprint":false},{"pmid":"29880481","id":"PMC_29880481","title":"Reciprocal Regulation of DUSP9 and DUSP16 Expression by HIF1 Controls ERK and p38 MAP Kinase Activity and Mediates Chemotherapy-Induced Breast Cancer Stem Cell Enrichment.","date":"2018","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/29880481","citation_count":75,"is_preprint":false},{"pmid":"16135819","id":"PMC_16135819","title":"The dual-specificity protein phosphatase DUSP9/MKP-4 is essential for placental function but is not required for normal embryonic development.","date":"2005","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/16135819","citation_count":60,"is_preprint":false},{"pmid":"28366588","id":"PMC_28366588","title":"DUSP9 Modulates DNA Hypomethylation in Female Mouse Pluripotent Stem Cells.","date":"2017","source":"Cell stem cell","url":"https://pubmed.ncbi.nlm.nih.gov/28366588","citation_count":56,"is_preprint":false},{"pmid":"23029454","id":"PMC_23029454","title":"A single nucleotide polymorphism within DUSP9 is associated with susceptibility to type 2 diabetes in a Japanese population.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23029454","citation_count":35,"is_preprint":false},{"pmid":"18058922","id":"PMC_18058922","title":"Expression of ERK signaling inhibitors Dusp6, Dusp7, and Dusp9 during mouse ear development.","date":"2008","source":"Developmental dynamics : an official publication of the American Association of Anatomists","url":"https://pubmed.ncbi.nlm.nih.gov/18058922","citation_count":33,"is_preprint":false},{"pmid":"34768967","id":"PMC_34768967","title":"DUSP9, a Dual-Specificity Phosphatase with a Key Role in Cell Biology and Human Diseases.","date":"2021","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/34768967","citation_count":30,"is_preprint":false},{"pmid":"25998184","id":"PMC_25998184","title":"Epigenetic silencing of DUSP9 induces the proliferation of human gastric cancer by activating JNK signaling.","date":"2015","source":"Oncology reports","url":"https://pubmed.ncbi.nlm.nih.gov/25998184","citation_count":29,"is_preprint":false},{"pmid":"33163285","id":"PMC_33163285","title":"DUSP9-mediated reduction of pERK1/2 supports cancer stem cell-like traits and promotes triple negative breast cancer.","date":"2020","source":"American journal of cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/33163285","citation_count":18,"is_preprint":false},{"pmid":"32103999","id":"PMC_32103999","title":"DUSP9 Suppresses Proliferation and Migration of Clear Cell Renal Cell Carcinoma via the mTOR Pathway.","date":"2020","source":"OncoTargets and therapy","url":"https://pubmed.ncbi.nlm.nih.gov/32103999","citation_count":16,"is_preprint":false},{"pmid":"30923463","id":"PMC_30923463","title":"MKP-4 suppresses hepatocarcinogenesis by targeting ERK1/2 pathway.","date":"2019","source":"Cancer cell 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materials","url":"https://pubmed.ncbi.nlm.nih.gov/39088948","citation_count":11,"is_preprint":false},{"pmid":"21206059","id":"PMC_21206059","title":"Exploring binding sites other than the catalytic core in the crystal structure of the catalytic domain of MKP-4.","date":"2010","source":"Acta crystallographica. Section D, Biological crystallography","url":"https://pubmed.ncbi.nlm.nih.gov/21206059","citation_count":11,"is_preprint":false},{"pmid":"39218968","id":"PMC_39218968","title":"Inhibition of miR-194-5p avoids DUSP9 downregulation thus limiting sepsis-induced cardiomyopathy.","date":"2024","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/39218968","citation_count":10,"is_preprint":false},{"pmid":"26170386","id":"PMC_26170386","title":"Selective Expression of the MAPK Phosphatase Dusp9/MKP-4 in Mouse Plasmacytoid Dendritic Cells and Regulation of IFN-β Production.","date":"2015","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/26170386","citation_count":8,"is_preprint":false},{"pmid":"36789693","id":"PMC_36789693","title":"DUSP9 alleviates hepatic ischemia/reperfusion injury by restraining both mitogen-activated protein kinase and IKK in an apoptosis signal-regulating kinase 1-dependent manner.","date":"2022","source":"Acta biochimica et biophysica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/36789693","citation_count":7,"is_preprint":false},{"pmid":"15668181","id":"PMC_15668181","title":"Expression, purification, and enzymatic characterization of the dual specificity mitogen-activated protein kinase phosphatase, MKP-4.","date":"2005","source":"Bioorganic chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15668181","citation_count":7,"is_preprint":false},{"pmid":"40020430","id":"PMC_40020430","title":"DUSP9-mediated inhibition of IRS1/PI3K/AKT pathway contributes to insulin resistance and metabolic dysfunction in gestational diabetes mellitus.","date":"2025","source":"Human immunology","url":"https://pubmed.ncbi.nlm.nih.gov/40020430","citation_count":5,"is_preprint":false},{"pmid":"36980809","id":"PMC_36980809","title":"Genetic Variants of HNF4A, WFS1, DUSP9, FTO, and ZFAND6 Genes Are Associated with Prediabetes Susceptibility and Inflammatory Markers in the Saudi Arabian Population.","date":"2023","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/36980809","citation_count":5,"is_preprint":false},{"pmid":"35163786","id":"PMC_35163786","title":"miR-132-3p Modulates DUSP9-Dependent p38/JNK Signaling Pathways to Enhance Inflammation in the Amnion Leading to Labor.","date":"2022","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35163786","citation_count":5,"is_preprint":false},{"pmid":"40861803","id":"PMC_40861803","title":"DUSP9 is Up-Regulated and Promotes Tumor Progression in Head and Neck Squamous Cell Carcinoma.","date":"2025","source":"Journal of Cancer","url":"https://pubmed.ncbi.nlm.nih.gov/40861803","citation_count":4,"is_preprint":false},{"pmid":"30835362","id":"PMC_30835362","title":"[Association of DUSP9 gene polymorphisms with gestational diabetes mellitus].","date":"2019","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30835362","citation_count":4,"is_preprint":false},{"pmid":"41405398","id":"PMC_41405398","title":"Mutual Exclusion Analysis Shows that DUSP9 Negatively Regulates PD-L1 Expression and Acts as a Target to Enhance Anti-PD-1 Efficacy.","date":"2025","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/41405398","citation_count":1,"is_preprint":false},{"pmid":"41508037","id":"PMC_41508037","title":"Single-cell multi-omics reveals DUSP9 as a key regulator of cancer stemness and a potential therapeutic target in hepatocellular carcinoma.","date":"2026","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41508037","citation_count":0,"is_preprint":false},{"pmid":"41850237","id":"PMC_41850237","title":"FBXO3-mediated DUSP9 ubiquitination promotes leukemia stem cell maintenance and tyrosine kinase inhibitor resistance in chronic myeloid leukemia.","date":"2026","source":"Cell reports. Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41850237","citation_count":0,"is_preprint":false},{"pmid":"40005897","id":"PMC_40005897","title":"Early Enhancement in Contrast-Enhanced Computed Tomography Is an Index of DUSP9, SLPI, ALDH1L2, and SLC1A1 Expression in Canine Hepatocellular Carcinoma: A Preliminary Study.","date":"2025","source":"Veterinary sciences","url":"https://pubmed.ncbi.nlm.nih.gov/40005897","citation_count":0,"is_preprint":false},{"pmid":"40564984","id":"PMC_40564984","title":"Cells of the Maternal-Fetal Interface May Contribute to Epidural-Related Maternal Fever After Administration of Ropivacaine: The Role of Phosphatases DUSP9 and PHLPP1.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/40564984","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18404,"output_tokens":4768,"usd":0.063366,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12900,"output_tokens":4523,"usd":0.088788,"stage2_stop_reason":"end_turn"},"total_usd":0.152154,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"MKP-4/DUSP9 is a dual-specificity phosphatase that catalyzes vanadate-sensitive dephosphorylation of p-nitrophenyl phosphate and directly inactivates purified ERK2 in vitro. When expressed in COS-7 cells, it inactivates MAP kinases with selectivity ERK > p38 = JNK/SAPK. It contains two N-terminal CH2 domains homologous to Cdc25 and the extended active-site motif VXVHCXAGXSRSXTX3AYLM conserved in dual-specificity phosphatases. Immunocytochemical analysis showed MKP-4 to be predominantly cytosolic, with punctate nuclear staining co-localizing with promyelocytic protein in a subpopulation of cells.\",\n      \"method\": \"In vitro phosphatase assay with purified ERK2, COS-7 cell overexpression, immunocytochemistry, Northern analysis, chromosomal localization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic reconstitution with purified substrate plus cellular overexpression, foundational characterization paper replicated by subsequent studies\",\n      \"pmids\": [\"9030581\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MKP-4/DUSP9 and an MKP-4/p38 complex purified via baculovirus expression both exhibit phosphatase activity toward surrogate substrates; the MKP-4/p38 complex provides substantially higher phosphatase activity than MKP-4 alone, demonstrating that p38 binding activates DUSP9 catalysis, analogous to the activation of MKP-3 by ERK2.\",\n      \"method\": \"Baculovirus expression, affinity and gel-filtration purification, in vitro spectrophotometric and fluorescence phosphatase assays with kinetic parameter determination\",\n      \"journal\": \"Bioorganic chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with purified protein complex and kinetic characterization; single lab but multiple substrate assays\",\n      \"pmids\": [\"15668181\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"DUSP9 knockout (X-linked gene; paternal X inactivated in extraembryonic tissues) in mice causes embryonic lethality due to failure of placental labyrinth development. The lethal phenotype maps specifically to trophoblast giant cells and labyrinth where DUSP9 is normally expressed. When the placental defect was rescued, DUSP9-null male embryos developed normally and were fertile, indicating DUSP9 is essential for placental organogenesis but dispensable for embryonic development.\",\n      \"method\": \"Gene targeting (knockout mouse), histological analysis of embryos 8–10.5 dpc, placental rescue experiments\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic KO with defined developmental phenotype, placental rescue experiment, replicated by independent pre-eclampsia study\",\n      \"pmids\": [\"16135819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Overexpression of MKP-4/DUSP9 in 3T3-L1 adipocytes inhibits ERK and JNK phosphorylation and, to a lesser extent, p38 phosphorylation, thereby preventing anisomycin-induced IRS-1 Ser307 phosphorylation. This restores insulin-stimulated IRS-1 tyrosine phosphorylation, IRS-1 docking with PI3K, and Akt phosphorylation, and reverses TNF-α-induced inhibition of insulin signaling and glucose uptake. Adenoviral overexpression in ob/ob mouse liver decreased ERK and JNK phosphorylation, reducing glycemia and improving glucose tolerance.\",\n      \"method\": \"Stable overexpression in 3T3-L1 cells, immunoblotting for phospho-ERK/JNK/p38/IRS-1/Akt, PI3K co-immunoprecipitation, glucose uptake assay, adenoviral hepatic overexpression in ob/ob mice\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal signaling readouts in both cell and in vivo models, multiple orthogonal methods establishing pathway position\",\n      \"pmids\": [\"18296638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Crystal structure of the DUSP9/MKP-4 catalytic domain (MKP-4C) resolved at 2.7 Å reveals significant deviations from canonical DUSP active conformations, with notable gaps between the catalytic core and surrounding loops. Virtual library screening identified inhibitor-binding sites near these gaps distinct from the active site, suggesting allosteric inhibition could prevent transition to the fully active conformation.\",\n      \"method\": \"X-ray crystallography at 2.7 Å resolution, virtual library screening\",\n      \"journal\": \"Acta crystallographica. Section D, Biological crystallography\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure determination is Tier 1; structural deviation from canonical DUSP conformation identified; single lab\",\n      \"pmids\": [\"21206059\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"DUSP9 is upregulated in female compared to male mouse ESCs due to its X-linked location (two active X chromosomes in female ESCs). Heterozygous loss of DUSP9 in female ESCs leads to male-like (hypermethylated) DNA methylation levels genome-wide. Cell fusion experiments showed that the ratio of X chromosomes to autosomes dictates methylation levels, placing DUSP9 as a mediator of X-dosage-dependent epigenetic regulation.\",\n      \"method\": \"Genome-wide methylation profiling, cell fusion experiments, CRISPR-mediated heterozygous DUSP9 deletion in female ESCs, RNA-seq\",\n      \"journal\": \"Cell stem cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with defined epigenetic phenotype, cell fusion epistasis, multiple orthogonal genomic methods\",\n      \"pmids\": [\"28366588\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In triple-negative breast cancer, HIF-1 transcriptionally induces DUSP9 expression in response to chemotherapy, leading to ERK dephosphorylation/inhibition. This ERK inhibition causes decreased inactivating phosphorylation of FoxO3, driving transcriptional induction of pluripotency factor Nanog and promoting breast cancer stem cell specification.\",\n      \"method\": \"siRNA knockdown of HIF1/DUSP9 in TNBC cells, immunoblotting for phospho-ERK/FoxO3, Nanog reporter assays, mammosphere formation, ALDH flow cytometry\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic knockdown with mechanistic pathway readouts, single lab, multiple orthogonal assays but no in vitro reconstitution\",\n      \"pmids\": [\"29880481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"ERK1/2 were identified as direct binding partners of MKP-4/DUSP9 by immunoprecipitation-mass spectrometry. MKP-4 negatively regulates ERK1/2 phosphorylation and reduces downstream CyclinD1 and c-Myc expression in hepatocellular carcinoma cells. Knockdown of MKP-4 increases cell proliferation and cancer stem cell traits, while upregulation of MKP-4 or ERK1/2 inhibitor treatment reverses these effects.\",\n      \"method\": \"Immunoprecipitation-mass spectrometry (IP-MS), western blot, colony formation, EdU incorporation, sphere formation assays, xenograft tumor models\",\n      \"journal\": \"Cancer cell international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — IP-MS for binding partner identification plus functional KD/OE in cells and in vivo; single lab\",\n      \"pmids\": [\"30923463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"DUSP9/MKP-4 is constitutively expressed in mouse plasmacytoid dendritic cells (pDCs) but not conventional DCs, and its expression correlates with impaired ERK1/2 phosphorylation upon TLR9 stimulation. Enforced retroviral expression of Dusp9 in GM-CSF-induced cDCs increased TLR9-induced IL-12p40 and IFN-β but not IL-10. Conditional deletion of Dusp9 in pDCs did not restore ERK1/2 activation after TLR9 stimulation and only weakly affected IFN-β and IL-12p40 production, indicating Dusp9 is sufficient but not essential for high-level IFN-β production in pDCs.\",\n      \"method\": \"Transcriptome analysis, retroviral overexpression in cDCs, conditional knockout (Dusp9flox/flox; CD11c-Cre), ELISA for cytokines, flow cytometry for phospho-ERK\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function and conditional KO, multiple cytokine readouts; single lab; KO result was weakly negative for IFN-β\",\n      \"pmids\": [\"26170386\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"DUSP9 directly binds to apoptosis signal-regulating kinase 1 (ASK1) and inhibits ASK1 phosphorylation, thereby decreasing TRAF6 levels, K63-linked ubiquitination, and downstream p38/JNK1 (but not ERK1) phosphorylation in hepatic ischemia/reperfusion injury. This mechanism is distinct from canonical ERK-focused DUSP9 activity.\",\n      \"method\": \"Co-immunoprecipitation (DUSP9–ASK1 binding), western blot for phospho-ASK1/p38/JNK1/ERK1, TRAF6/ubiquitin immunoprecipitation, adenoviral overexpression and siRNA knockdown in vivo and in vitro\",\n      \"journal\": \"Acta biochimica et biophysica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for direct binding, functional gain/loss experiments with mechanistic readouts; single lab\",\n      \"pmids\": [\"36789693\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"HDAC9 represses DUSP9 expression by deacetylating histone H4K12 (H4K12ac) at the DUSP9 promoter, thereby activating downstream MAPK signaling and promoting particulate matter-induced airway inflammation. HDAC9 upregulation is mediated upstream by the METTL3/m6A/IGF2BP3 pathway acting on HDAC9 mRNA.\",\n      \"method\": \"ChIP for H4K12ac at DUSP9 promoter, siRNA knockdown of HDAC9/DUSP9, western blot for MAPK pathway, in vivo mouse airway inflammation model\",\n      \"journal\": \"Journal of hazardous materials\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP establishes epigenetic writing mechanism at DUSP9 promoter; functional knockdown with MAPK readout; single lab\",\n      \"pmids\": [\"39088948\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DUSP9 directly interacts with insulin receptor substrate 1 (IRS1) and inhibits IRS1 phosphorylation at Tyr632, impairing downstream IRS1/PI3K/AKT insulin signaling. This interaction was demonstrated by co-immunoprecipitation and pull-down assays in high-glucose-treated trophoblast cells, and DUSP9 knockdown in a GDM mouse model restored IRS1/PI3K/AKT pathway activation.\",\n      \"method\": \"Co-immunoprecipitation, pull-down assay, western blot for phospho-IRS1(Tyr632)/PI3K/AKT, lentivirus-mediated shRNA knockdown in GDM mouse model\",\n      \"journal\": \"Human immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and pull-down for direct binding, in vivo KD with defined phosphorylation readout; single lab\",\n      \"pmids\": [\"40020430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"DUSP9 dephosphorylates STAT3 to negatively regulate PD-L1 expression in tumor cells. Mechanistic experiments showed that DUSP9 overexpression reduced phospho-STAT3 levels, leading to decreased PD-L1 transcription, while DUSP9 knockdown increased PD-L1 expression. Combining DUSP9 targeting with anti-PD-1 antibody enhanced therapeutic sensitivity in syngeneic tumor models.\",\n      \"method\": \"DUSP9 overexpression/knockdown, immunoblotting for phospho-STAT3 and PD-L1, syngeneic tumor models with anti-PD-1 combination\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain-of-function and loss-of-function with mechanistic phosphorylation readout for STAT3; single lab, no in vitro phosphatase reconstitution with STAT3\",\n      \"pmids\": [\"41405398\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FBXO3 E3 ubiquitin ligase directly interacts with DUSP9 and promotes its ubiquitination and degradation, thereby activating the MAPK pathway and maintaining leukemia stem cell activity in CML. DUSP9 knockdown partially reverses the LSC elimination caused by FBXO3 deficiency, placing DUSP9 downstream of FBXO3 in this pathway.\",\n      \"method\": \"Co-immunoprecipitation (FBXO3–DUSP9 interaction), ubiquitination assay, FBXO3 KO/DUSP9 KD in CML cell lines and primary LSCs, in vivo LSC models\",\n      \"journal\": \"Cell reports. Medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for binding, ubiquitination assay for PTM mechanism, epistasis by double KO/KD; single lab\",\n      \"pmids\": [\"41850237\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Caffeine directly targets DUSP9 (identified by surface plasmon resonance, CETSA, and DARTS assays) and restores hepatic DUSP9 expression reduced by high-fat/high-carbohydrate diet. DUSP9 knockdown in vivo counteracted the therapeutic effects of caffeine on MASH, including glycolipid metabolism disorders. The downstream mechanism involves DUSP9-mediated inactivation of the ASK1-p38/JNK signaling pathway.\",\n      \"method\": \"Surface plasmon resonance (SPR), CETSA, DARTS for direct target identification; DUSP9 knockdown in vivo; western blot for ASK1/p38/JNK; metabolic phenotyping in MASH mouse models\",\n      \"journal\": \"Redox biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — three orthogonal direct binding assays (SPR, CETSA, DARTS) establish physical interaction; in vivo functional validation; single lab\",\n      \"pmids\": [\"39879738\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"DUSP9 suppresses proliferation and migration of clear cell renal cell carcinoma cells and inhibits phosphorylation of mTOR and expression of downstream mTOR pathway proteins Sox2, c-Myc, and HIF-1α. This was confirmed by in vitro assays and xenograft tumor models.\",\n      \"method\": \"DUSP9 overexpression in ccRCC cell lines, western blot for p-mTOR/Sox2/c-Myc/HIF-1α, CCK-8 proliferation, wound-healing and transwell migration assays, nude mouse xenograft\",\n      \"journal\": \"OncoTargets and therapy\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — overexpression with downstream signaling readout; no direct biochemical demonstration of DUSP9–mTOR interaction; single lab, single approach\",\n      \"pmids\": [\"32103999\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"DUSP9/MKP-4 is an X-linked cytoplasmic dual-specificity MAP kinase phosphatase that dephosphorylates ERK1/2 (preferred substrate), p38, JNK, and ASK1 by targeting both phospho-threonine and phospho-tyrosine residues; its catalytic activity is allosterically enhanced by substrate (p38) binding, it is subject to FBXO3-mediated ubiquitination and HDAC9-mediated epigenetic silencing, it directly interacts with IRS1 to modulate insulin signaling, and it dephosphorylates STAT3 to suppress PD-L1 expression, with its essential physiological role in placental labyrinth development established by knockout studies in mice.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"DUSP9/MKP-4 is a predominantly cytosolic dual-specificity MAP kinase phosphatase that inactivates MAP kinases with a substrate preference of ERK > p38 = JNK by dephosphorylating both phospho-threonine and phospho-tyrosine residues, establishing it as a negative regulator of MAPK signaling [#0]. Its catalytic activity is allosterically enhanced upon substrate binding, as the MKP-4/p38 complex displays substantially higher phosphatase activity than the enzyme alone [#1], and crystallography of the catalytic domain shows deviations from canonical active DUSP conformations consistent with a regulated transition to full activity [#4]. Beyond canonical MAPK targets, DUSP9 directly binds ASK1 to suppress its phosphorylation and downstream TRAF6/p38/JNK signaling [#9], directly engages IRS1 to inhibit Tyr632 phosphorylation and dampen IRS1/PI3K/AKT insulin signaling [#11], and dephosphorylates STAT3 to repress PD-L1 transcription in tumor cells [#12]. Through these activities DUSP9 functions as a brake on MAPK-driven proliferation and stemness in multiple cancers, suppressing ERK-dependent CyclinD1/c-Myc output [#7] and breast cancer stem cell specification [#6], and its loss is restrained by FBXO3-mediated ubiquitination and degradation that reactivates MAPK signaling in leukemia stem cells [#13] and by HDAC9-mediated promoter deacetylation that silences DUSP9 [#10]. Genetically, DUSP9 is X-linked and essential for placental labyrinth development, with knockout causing embryonic lethality through a trophoblast/labyrinth defect while embryos rescued of the placental defect develop normally [#2], and its X-dosage-dependent expression mediates epigenetic control of genome-wide DNA methylation in embryonic stem cells [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established DUSP9 as a bona fide dual-specificity phosphatase that directly inactivates MAP kinases, defining its core enzymatic identity and substrate hierarchy.\",\n      \"evidence\": \"in vitro phosphatase assays with purified ERK2 and MAPK inactivation in COS-7 cells, plus immunocytochemistry and chromosomal mapping\",\n      \"pmids\": [\"9030581\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Quantitative kinetics toward p38/JNK not resolved\", \"Physiological substrate context in vivo not addressed\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Showed DUSP9 catalysis is substrate-activated, explaining how its phosphatase activity is allosterically tuned by binding its kinase substrate.\",\n      \"evidence\": \"baculovirus-expressed MKP-4 and MKP-4/p38 complex with kinetic phosphatase assays on surrogate substrates\",\n      \"pmids\": [\"15668181\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of activation not defined here\", \"Whether ERK binding activates similarly not tested in this study\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Defined an essential, non-redundant physiological role for DUSP9 in placental organogenesis via X-linked gene targeting.\",\n      \"evidence\": \"knockout mouse with histological embryo analysis and placental rescue experiments\",\n      \"pmids\": [\"16135819\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which MAPK substrate dysregulation drives the labyrinth defect not pinpointed\", \"Cell-autonomous trophoblast mechanism not dissected\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Positioned DUSP9 as a regulator of insulin signaling by suppressing stress-kinase-mediated IRS-1 inhibition, linking MAPK phosphatase activity to glucose homeostasis.\",\n      \"evidence\": \"stable/adenoviral overexpression in adipocytes and ob/ob liver with insulin-pathway immunoblotting and glucose tolerance\",\n      \"pmids\": [\"18296638\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct DUSP9 binding to IRS-1 not shown in this study\", \"Loss-of-function metabolic phenotype not tested\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Provided a structural framework showing the catalytic domain adopts a non-canonical conformation, rationalizing allosteric regulation and inhibitor design.\",\n      \"evidence\": \"X-ray crystallography at 2.7 Å with virtual library screening\",\n      \"pmids\": [\"21206059\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrate-bound active conformation not captured\", \"Predicted allosteric inhibitor sites not experimentally validated\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified DUSP9 as the X-dosage-sensitive mediator coupling X-chromosome number to genome-wide DNA methylation levels in ESCs.\",\n      \"evidence\": \"CRISPR heterozygous deletion, cell fusion epistasis, and genome-wide methylation/RNA-seq\",\n      \"pmids\": [\"28366588\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular path from DUSP9 to the methylation machinery not defined\", \"Relevance to human X-dosage compensation not established here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Tested DUSP9's role in innate immune MAPK control, showing it is sufficient but not essential for dampening ERK and shaping pDC cytokine output.\",\n      \"evidence\": \"retroviral overexpression in cDCs and conditional knockout in pDCs with cytokine ELISA and phospho-ERK flow cytometry\",\n      \"pmids\": [\"26170386\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Conditional KO failed to restore ERK activation, indicating redundancy\", \"Compensating phosphatases not identified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Placed DUSP9 within a HIF-1-driven chemotherapy response that promotes breast cancer stem cells through ERK/FoxO3/Nanog signaling.\",\n      \"evidence\": \"siRNA knockdown in TNBC cells with phospho-ERK/FoxO3 immunoblotting, Nanog reporter, mammosphere and ALDH assays\",\n      \"pmids\": [\"29880481\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct DUSP9 dephosphorylation of ERK in this context not reconstituted\", \"Single lab, no in vivo confirmation of stemness axis\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Confirmed ERK1/2 as direct DUSP9 binding partners and established a tumor-suppressive role in hepatocellular carcinoma proliferation and stemness.\",\n      \"evidence\": \"IP-MS for binding, knockdown/overexpression with colony/EdU/sphere assays and xenografts\",\n      \"pmids\": [\"30923463\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding stoichiometry and dephosphorylation kinetics not quantified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Expanded DUSP9 substrate scope beyond MAPKs by showing direct binding and inhibition of ASK1, defining a non-canonical p38/JNK-selective branch.\",\n      \"evidence\": \"Co-IP for DUSP9–ASK1 binding with phospho-ASK1/p38/JNK immunoblotting and TRAF6/ubiquitin IP in hepatic I/R models\",\n      \"pmids\": [\"36789693\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct dephosphorylation of ASK1 not reconstituted in vitro\", \"Reciprocal validation of binding limited to single Co-IP\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined an upstream epigenetic silencing mechanism whereby HDAC9 deacetylates H4K12 at the DUSP9 promoter to derepress MAPK signaling in airway inflammation.\",\n      \"evidence\": \"ChIP for H4K12ac at DUSP9 promoter, HDAC9/DUSP9 knockdown, MAPK immunoblotting and in vivo airway model\",\n      \"pmids\": [\"39088948\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct HDAC9 occupancy versus indirect effects not fully separated\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated direct DUSP9–IRS1 interaction and Tyr632 dephosphorylation, providing the binding mechanism underlying its insulin-signaling control in gestational diabetes.\",\n      \"evidence\": \"Co-IP and pull-down in trophoblast cells with phospho-IRS1/PI3K/AKT immunoblotting and shRNA knockdown in GDM mice\",\n      \"pmids\": [\"40020430\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether DUSP9 directly dephosphorylates IRS1 versus acting via kinases not resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified STAT3 as a DUSP9 target controlling PD-L1 transcription, linking DUSP9 to tumor immune evasion and checkpoint therapy sensitivity.\",\n      \"evidence\": \"DUSP9 overexpression/knockdown with phospho-STAT3 and PD-L1 immunoblotting and anti-PD-1 syngeneic tumor models\",\n      \"pmids\": [\"41405398\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro phosphatase reconstitution with STAT3\", \"Direct versus indirect dephosphorylation not distinguished\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Established FBXO3-mediated ubiquitination and degradation as the post-translational control that limits DUSP9 to sustain MAPK-driven leukemia stem cell activity.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, and FBXO3 KO/DUSP9 KD epistasis in CML lines, primary LSCs, and in vivo models\",\n      \"pmids\": [\"41850237\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitination site on DUSP9 not mapped\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified DUSP9 as a small-molecule (caffeine) target whose restoration ameliorates metabolic disease through ASK1-p38/JNK inactivation.\",\n      \"evidence\": \"SPR, CETSA, and DARTS direct binding assays plus in vivo DUSP9 knockdown and MAPK immunoblotting in MASH models\",\n      \"pmids\": [\"39879738\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Caffeine binding site on DUSP9 not structurally defined\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How DUSP9's substrate selectivity, allosteric activation, and degradation are integrated to assign it to canonical ERK versus non-canonical ASK1/IRS1/STAT3 branches in a given cell type remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified structural model of substrate-bound active DUSP9\", \"Direct in vitro dephosphorylation not reconstituted for ASK1, IRS1, or STAT3\", \"Tissue-specific determinants of substrate choice unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 9, 11, 12]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 7, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 3, 9]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [5, 10]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MAPK1\", \"MAPK3\", \"MAP3K5\", \"IRS1\", \"STAT3\", \"FBXO3\", \"MAPK14\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}