{"gene":"KLHL6","run_date":"2026-04-28T18:30:27","timeline":{"discoveries":[{"year":2005,"finding":"KLHL6 is required for B-cell antigen receptor (BCR) signal transduction and germinal center formation. KLHL6-deficient mice show reduced transitional and mature B cells, blunted germinal center reactions, and B cells exhibit decreased proliferation, Ca2+ response, and phospholipase Cγ2 activation upon BCR cross-linking. The requirement is B-cell-intrinsic.","method":"Conditional and global knockout mouse models; B-cell proliferation assays; Ca2+ flux measurements; PLCγ2 activation assays; B-cell-specific rescue experiments","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — clean KO with multiple orthogonal functional readouts, B-cell-intrinsic requirement demonstrated by conditional KO","pmids":["16166635"],"is_preprint":false},{"year":2017,"finding":"KLHL6 functions as a substrate adaptor for the Cullin3 E3 ubiquitin ligase complex; KLHL6 also interacts with HBXIP/Lamtor5, a protein involved in cell-cycle regulation and cytokinesis. KLHL6 deficiency causes a block in transitional type 1 B cell survival and progression to transitional type 2 B cells, with overexpression of APC/C target genes linked to cell proliferation.","method":"Co-immunoprecipitation in BL2 Burkitt lymphoma cells; gene expression profiling of Klhl6-deficient B cells; flow cytometry of B cell developmental stages","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 3 — single Co-IP for HBXIP interaction; Cullin3 interaction supported by prior and subsequent work; developmental phenotype well characterized","pmids":["28807996"],"is_preprint":false},{"year":2018,"finding":"KLHL6 assembles with Cullin3 to form a functional Cullin-RING ubiquitin ligase. The mRNA decay factor roquin2 is a direct substrate of KLHL6; roquin2 degradation is triggered by BCR activation and requires the integrity of Tyr691 in roquin2 for its interaction with KLHL6. Cancer-associated KLHL6 mutations disrupt its interaction with Cullin3, abolishing ligase activity. Stabilized roquin2 promotes mRNA decay of TNFAIP3 (A20), an NF-κB inhibitor, thereby promoting DLBCL growth and survival.","method":"Affinity purification mass spectrometry (AP-MS); Co-immunoprecipitation; ubiquitination assays; site-directed mutagenesis (Y691F roquin2); xenograft models; RNA decay assays","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including AP-MS substrate identification, mutagenesis validation, in vivo xenograft, and RNA decay functional readout in a single study","pmids":["29695787"],"is_preprint":false},{"year":2023,"finding":"Full-length KLHL6 adopts a homomultimeric form in solution. Binding to Cullin3 N-terminal domain (Cul3NTD) enhances KLHL6 stability and homogeneity by forming a complex, as visualized by gel filtration and negative-staining electron microscopy.","method":"Recombinant protein expression and purification; gel filtration chromatography; negative-staining electron microscopy","journal":"Protein expression and purification","confidence":"Medium","confidence_rationale":"Tier 2 — direct structural/biochemical characterization of purified protein with two orthogonal methods; single study","pmids":["37286065"],"is_preprint":false},{"year":2024,"finding":"KLHL6 directly targets the BCR signaling subunits CD79A and CD79B for ubiquitin-mediated degradation, thereby regulating surface BCR levels and downstream BCR signaling. Mutations in the BTB domain of KLHL6 disrupt its localization and heterodimerization, increasing surface BCR levels and signaling, whereas Kelch domain mutants have the opposite effect. Loss of physiologic KLHL6 expression is associated with higher CD79B levels in MCD/C5-like activated B-cell DLBCLs.","method":"High-throughput protein interactome screens; Co-immunoprecipitation; flow cytometry; functional BCR signaling assays; domain-specific mutagenesis; KLHL6 silencing","journal":"Blood cancer discovery","confidence":"High","confidence_rationale":"Tier 2 — interactome screen plus multiple orthogonal functional validations including mutagenesis and silencing with distinct phenotypic readouts","pmids":["38630892"],"is_preprint":false},{"year":2026,"finding":"KLHL6 functions as a dual negative regulator of T cell exhaustion and mitochondrial dysfunction. Mechanistically, KLHL6 promotes TOX poly-ubiquitination and proteasomal degradation, attenuating the transition of progenitor exhausted T cells to terminal exhaustion. Simultaneously, KLHL6 maintains mitochondrial fitness by constraining excessive mitochondrial fission via post-translational regulation of the PGAM5-Drp1 axis. KLHL6 is naturally downregulated by TCR ligation through PI3K-AKT-mediated inhibition of FOXO1, and enforcing KLHL6 expression improves anti-tumor T cell efficacy in vivo.","method":"In vivo CRISPR screens; ubiquitination assays; co-immunoprecipitation; mitochondrial fission assays; adoptive T cell transfer in vivo tumor/viral models; computational atlas analyses","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1-2 — in vivo CRISPR screen, ubiquitination assays with substrate identification, multiple functional readouts in vivo, mechanistic pathway placement via mutagenesis and epistasis","pmids":["41535474"],"is_preprint":false}],"current_model":"KLHL6 is a BTB-Kelch substrate adaptor for Cullin3-RING E3 ubiquitin ligase complexes that forms homomultimers and, upon BCR activation, ubiquitinates substrates including roquin2 and the BCR subunits CD79A/CD79B to regulate BCR signaling homeostasis and germinal center B cell responses; in T cells, KLHL6 additionally ubiquitinates TOX to suppress exhaustion and regulates the PGAM5-Drp1 axis to maintain mitochondrial fitness, while its expression is suppressed by chronic TCR stimulation via PI3K-AKT/FOXO1 signaling."},"narrative":{"teleology":[{"year":2005,"claim":"Establishing that KLHL6 is required cell-intrinsically for BCR signal transduction and germinal center B cell biology answered the foundational question of whether this uncharacterized BTB-Kelch protein has a physiological role in the immune system.","evidence":"Global and conditional knockout mice with B-cell proliferation, Ca²⁺ flux, and PLCγ2 activation assays","pmids":["16166635"],"confidence":"High","gaps":["Molecular mechanism of how KLHL6 influences BCR signaling was unknown","No substrates or E3 ligase activity had been demonstrated","Role in non-B lymphocytes unexplored"]},{"year":2017,"claim":"Identification of KLHL6 as a Cullin3 adaptor and its interaction with HBXIP/Lamtor5 placed KLHL6 within the CRL3 ubiquitin ligase framework and linked it to cell-cycle gene regulation during the transitional B cell checkpoint.","evidence":"Co-immunoprecipitation in BL2 cells; gene expression profiling and flow cytometry of Klhl6-deficient B cells","pmids":["28807996"],"confidence":"Medium","gaps":["HBXIP interaction shown by single Co-IP without reciprocal validation","No direct ubiquitination substrates identified","Causal relationship between APC/C target gene upregulation and B cell block not established"]},{"year":2018,"claim":"Demonstrating that KLHL6–Cullin3 ubiquitinates roquin2 upon BCR activation, and that cancer-associated KLHL6 mutations abolish this activity, provided the first defined substrate and a direct mechanistic link between KLHL6 loss-of-function and DLBCL pathogenesis via TNFAIP3/NF-κB deregulation.","evidence":"AP-MS, Co-IP, ubiquitination assays, Y691F mutagenesis of roquin2, xenograft models, RNA decay assays","pmids":["29695787"],"confidence":"High","gaps":["Whether roquin2 is the primary BCR-signaling-relevant substrate was unclear","Structural basis of KLHL6–substrate recognition unknown","Extent of the KLHL6 substrate repertoire beyond roquin2 not addressed"]},{"year":2023,"claim":"Biochemical and structural characterization revealed that full-length KLHL6 forms homomultimers stabilized by Cullin3 binding, providing an architectural basis for understanding how the CRL3-KLHL6 complex assembles.","evidence":"Recombinant protein gel filtration and negative-staining electron microscopy","pmids":["37286065"],"confidence":"Medium","gaps":["No high-resolution structure was obtained","Functional significance of homomultimerization for ligase activity not tested","Single study without independent replication"]},{"year":2024,"claim":"Identification of CD79A and CD79B as direct KLHL6 ubiquitination targets resolved how KLHL6 tunes surface BCR levels and explained the domain-specific consequences of cancer mutations — BTB mutants increase and Kelch mutants decrease BCR signaling.","evidence":"High-throughput interactome screens, Co-IP, flow cytometry, domain-specific mutagenesis, KLHL6 silencing","pmids":["38630892"],"confidence":"High","gaps":["Structural basis of Kelch domain recognition of CD79A/B not determined","In vivo validation in mouse models not reported","Whether CD79A/B and roquin2 targeting are coordinated or independent events unknown"]},{"year":2026,"claim":"Extending KLHL6 function to T cells, this work showed KLHL6 ubiquitinates TOX to prevent terminal exhaustion and restrains PGAM5–Drp1-mediated mitochondrial fission, while its own expression is negatively regulated by PI3K–AKT/FOXO1 upon chronic TCR stimulation, establishing KLHL6 as a therapeutic target for reinvigorating anti-tumor immunity.","evidence":"In vivo CRISPR screens, ubiquitination assays, Co-IP, mitochondrial fission assays, adoptive T cell transfer in tumor and viral models","pmids":["41535474"],"confidence":"High","gaps":["Whether TOX and PGAM5 ubiquitination share structural determinants recognized by the Kelch domain is unknown","Relative contribution of TOX degradation vs. mitochondrial fitness to T cell rejuvenation not disentangled","Potential off-target effects of enforced KLHL6 expression on other CRL3 substrates not assessed"]},{"year":null,"claim":"A high-resolution structure of the KLHL6–Cullin3 complex bound to substrate, and a comprehensive substrate catalog across lymphocyte lineages, are needed to unify the diverse substrate specificities and inform therapeutic strategies.","evidence":"","pmids":[],"confidence":"High","gaps":["No high-resolution cryo-EM or crystal structure of KLHL6–Cullin3–substrate ternary complex","Full substrate repertoire across B, T, and other cell types not systematically defined","In vivo consequences of enforcing KLHL6 expression for immunotherapy not clinically evaluated"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,4,5]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[1,2,4]}],"localization":[],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,2,4,5]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[2,4,5]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,4,5]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[2,4]}],"complexes":["CRL3-KLHL6 (Cullin3-RING E3 ubiquitin ligase)"],"partners":["CUL3","RC3H2","CD79A","CD79B","TOX","PGAM5","LAMTOR5"],"other_free_text":[]},"mechanistic_narrative":"KLHL6 is a BTB-Kelch family substrate adaptor for Cullin3-RING E3 ubiquitin ligase complexes that controls lymphocyte signaling homeostasis by targeting key substrates for proteasomal degradation. In B cells, KLHL6 is essential for BCR signal transduction and germinal center formation; BCR activation triggers KLHL6-dependent ubiquitination of roquin2 and the BCR subunits CD79A/CD79B, thereby tuning surface BCR levels and downstream NF-κB signaling [PMID:16166635, PMID:29695787, PMID:38630892]. In T cells, KLHL6 ubiquitinates TOX to restrain terminal exhaustion and regulates the PGAM5–Drp1 axis to maintain mitochondrial fitness, with its expression suppressed by chronic TCR stimulation through PI3K–AKT/FOXO1 signaling [PMID:41535474]. Cancer-associated KLHL6 mutations disrupt Cullin3 binding or alter substrate engagement, and loss of KLHL6 function contributes to activated B-cell diffuse large B-cell lymphoma pathogenesis [PMID:29695787, PMID:38630892]."},"prefetch_data":{"uniprot":{"accession":"Q8WZ60","full_name":"Kelch-like protein 6","aliases":[],"length_aa":621,"mass_kda":70.4,"function":"Involved in B-lymphocyte antigen receptor signaling and germinal center formation","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/Q8WZ60/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KLHL6","classification":"Not 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Cγ2 upon BCR cross-linking, and exhibit blunted germinal center formation in a B-cell-intrinsic manner.\",\n      \"method\": \"Knockout mouse model (global and B-cell-specific), BCR cross-linking assays measuring proliferation, Ca2+ flux, and PLCγ2 activation; comparison of global vs. conditional knockouts for epistasis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype, multiple orthogonal readouts, cell-intrinsic requirement confirmed by conditional KO\",\n      \"pmids\": [\"16166635\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"KLHL6 assembles with Cullin3 to form a functional Cullin-RING ubiquitin E3 ligase; cancer-associated mutations in KLHL6 disrupt interaction with Cullin3 and abolish ligase activity. The mRNA decay factor Roquin2 is a direct substrate of KLHL6; its degradation is dependent on BCR activation and requires Tyr691 on Roquin2 for interaction with KLHL6. Loss of KLHL6 stabilizes Roquin2, which promotes mRNA decay of TNFAIP3 (A20), an NF-κB pathway inhibitor.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry interactome, in vitro ubiquitination assay, site-directed mutagenesis (Y691F Roquin2), xenograft models, RNA-binding mutant analysis\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro ubiquitination assay with mutagenesis, reciprocal Co-IP/MS, functional rescue experiments, multiple orthogonal methods\",\n      \"pmids\": [\"29695787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"KLHL6 interacts with Cullin3 and also binds HBXIP/Lamtor5 (a protein involved in cell-cycle regulation and cytokinesis) in the BL2 Burkitt lymphoma cell line. KLHL6 deficiency causes a survival and differentiation block specifically at the transitional type 1 B-cell stage, associated with overexpression of anaphase-promoting complex/cyclosome target genes.\",\n      \"method\": \"Co-immunoprecipitation in BL2 cells, knockout mouse analysis with flow cytometry and gene expression profiling\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP for HBXIP interaction; KO phenotype with gene expression data supports mechanistic model\",\n      \"pmids\": [\"28807996\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"KLHL6 targets the BCR signaling subunits CD79A and CD79B for ubiquitin-mediated degradation, thereby regulating surface BCR homeostasis. BTB domain mutations in KLHL6 disrupt its localization and homodimerization, increasing surface BCR levels and signaling, while Kelch domain mutants have the opposite effect.\",\n      \"method\": \"High-throughput protein interactome screens, functional characterization, domain-specific mutagenesis (BTB vs. Kelch mutants), surface BCR quantification, KLHL6 silencing vs. mutation comparison\",\n      \"journal\": \"Blood cancer discovery\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — interactome screen plus mutagenesis distinguishing domain-specific phenotypes, functional characterization of multiple mutants with defined molecular readouts\",\n      \"pmids\": [\"38630892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Full-length KLHL6 adopts a homomultimeric form in solution, and the N-terminal domain of Cullin3 (Cul3NTD) enhances the stability and homogeneity of KLHL6 by forming a complex with it, as characterized by gel filtration and negative-staining electron microscopy.\",\n      \"method\": \"Protein expression/purification, gel filtration chromatography, negative-staining electron microscopy\",\n      \"journal\": \"Protein expression and purification\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct structural/biophysical characterization of KLHL6 oligomeric state and Cul3 complex formation in vitro\",\n      \"pmids\": [\"37286065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"KLHL6 promotes TOX poly-ubiquitination and proteasomal degradation, attenuating the transition of progenitor exhausted CD8+ T cells to terminal exhaustion. Simultaneously, KLHL6 maintains mitochondrial fitness by post-translationally regulating the PGAM5-Drp1 axis to constrain excessive mitochondrial fission during chronic TCR stimulation. KLHL6 is naturally downregulated by TCR ligation via PI3K-AKT-mediated inhibition of FOXO1.\",\n      \"method\": \"In vivo CRISPR screens, enforced KLHL6 expression in T cells, poly-ubiquitination assays, mitochondrial fission assays, tumor and viral infection in vivo models\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vivo CRISPR screen, ubiquitination assays, multiple orthogonal functional readouts in vivo, mechanistic dissection of two independent pathways\",\n      \"pmids\": [\"41535474\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KLHL6 functions as a substrate-adaptor for a Cullin3-RING E3 ubiquitin ligase complex that regulates BCR signaling by targeting CD79A/CD79B and Roquin2 for ubiquitin-mediated degradation in B cells, and in T cells promotes degradation of TOX and PGAM5 to suppress exhaustion and maintain mitochondrial fitness; cancer-associated mutations disrupt its BTB-mediated dimerization/localization or Kelch-mediated substrate recognition, corrupting these homeostatic ubiquitination functions.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"KLHL6 is required for B-cell antigen receptor (BCR) signal transduction and germinal center formation. KLHL6-deficient mice show reduced transitional and mature B cells, blunted germinal center reactions, and B cells exhibit decreased proliferation, Ca2+ response, and phospholipase Cγ2 activation upon BCR cross-linking. The requirement is B-cell-intrinsic.\",\n      \"method\": \"Conditional and global knockout mouse models; B-cell proliferation assays; Ca2+ flux measurements; PLCγ2 activation assays; B-cell-specific rescue experiments\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with multiple orthogonal functional readouts, B-cell-intrinsic requirement demonstrated by conditional KO\",\n      \"pmids\": [\"16166635\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"KLHL6 functions as a substrate adaptor for the Cullin3 E3 ubiquitin ligase complex; KLHL6 also interacts with HBXIP/Lamtor5, a protein involved in cell-cycle regulation and cytokinesis. KLHL6 deficiency causes a block in transitional type 1 B cell survival and progression to transitional type 2 B cells, with overexpression of APC/C target genes linked to cell proliferation.\",\n      \"method\": \"Co-immunoprecipitation in BL2 Burkitt lymphoma cells; gene expression profiling of Klhl6-deficient B cells; flow cytometry of B cell developmental stages\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP for HBXIP interaction; Cullin3 interaction supported by prior and subsequent work; developmental phenotype well characterized\",\n      \"pmids\": [\"28807996\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"KLHL6 assembles with Cullin3 to form a functional Cullin-RING ubiquitin ligase. The mRNA decay factor roquin2 is a direct substrate of KLHL6; roquin2 degradation is triggered by BCR activation and requires the integrity of Tyr691 in roquin2 for its interaction with KLHL6. Cancer-associated KLHL6 mutations disrupt its interaction with Cullin3, abolishing ligase activity. Stabilized roquin2 promotes mRNA decay of TNFAIP3 (A20), an NF-κB inhibitor, thereby promoting DLBCL growth and survival.\",\n      \"method\": \"Affinity purification mass spectrometry (AP-MS); Co-immunoprecipitation; ubiquitination assays; site-directed mutagenesis (Y691F roquin2); xenograft models; RNA decay assays\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including AP-MS substrate identification, mutagenesis validation, in vivo xenograft, and RNA decay functional readout in a single study\",\n      \"pmids\": [\"29695787\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Full-length KLHL6 adopts a homomultimeric form in solution. Binding to Cullin3 N-terminal domain (Cul3NTD) enhances KLHL6 stability and homogeneity by forming a complex, as visualized by gel filtration and negative-staining electron microscopy.\",\n      \"method\": \"Recombinant protein expression and purification; gel filtration chromatography; negative-staining electron microscopy\",\n      \"journal\": \"Protein expression and purification\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct structural/biochemical characterization of purified protein with two orthogonal methods; single study\",\n      \"pmids\": [\"37286065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"KLHL6 directly targets the BCR signaling subunits CD79A and CD79B for ubiquitin-mediated degradation, thereby regulating surface BCR levels and downstream BCR signaling. Mutations in the BTB domain of KLHL6 disrupt its localization and heterodimerization, increasing surface BCR levels and signaling, whereas Kelch domain mutants have the opposite effect. Loss of physiologic KLHL6 expression is associated with higher CD79B levels in MCD/C5-like activated B-cell DLBCLs.\",\n      \"method\": \"High-throughput protein interactome screens; Co-immunoprecipitation; flow cytometry; functional BCR signaling assays; domain-specific mutagenesis; KLHL6 silencing\",\n      \"journal\": \"Blood cancer discovery\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — interactome screen plus multiple orthogonal functional validations including mutagenesis and silencing with distinct phenotypic readouts\",\n      \"pmids\": [\"38630892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"KLHL6 functions as a dual negative regulator of T cell exhaustion and mitochondrial dysfunction. Mechanistically, KLHL6 promotes TOX poly-ubiquitination and proteasomal degradation, attenuating the transition of progenitor exhausted T cells to terminal exhaustion. Simultaneously, KLHL6 maintains mitochondrial fitness by constraining excessive mitochondrial fission via post-translational regulation of the PGAM5-Drp1 axis. KLHL6 is naturally downregulated by TCR ligation through PI3K-AKT-mediated inhibition of FOXO1, and enforcing KLHL6 expression improves anti-tumor T cell efficacy in vivo.\",\n      \"method\": \"In vivo CRISPR screens; ubiquitination assays; co-immunoprecipitation; mitochondrial fission assays; adoptive T cell transfer in vivo tumor/viral models; computational atlas analyses\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vivo CRISPR screen, ubiquitination assays with substrate identification, multiple functional readouts in vivo, mechanistic pathway placement via mutagenesis and epistasis\",\n      \"pmids\": [\"41535474\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KLHL6 is a BTB-Kelch substrate adaptor for Cullin3-RING E3 ubiquitin ligase complexes that forms homomultimers and, upon BCR activation, ubiquitinates substrates including roquin2 and the BCR subunits CD79A/CD79B to regulate BCR signaling homeostasis and germinal center B cell responses; in T cells, KLHL6 additionally ubiquitinates TOX to suppress exhaustion and regulates the PGAM5-Drp1 axis to maintain mitochondrial fitness, while its expression is suppressed by chronic TCR stimulation via PI3K-AKT/FOXO1 signaling.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KLHL6 is a substrate-adaptor of the Cullin3-RING E3 ubiquitin ligase complex that controls antigen receptor signaling and cellular homeostasis in both B and T lymphocytes. In B cells, KLHL6 is required for BCR signal transduction, germinal center formation, and transitional B-cell differentiation; it targets the BCR signaling subunits CD79A/CD79B for ubiquitin-mediated degradation to regulate surface BCR levels, and degrades the mRNA decay factor Roquin2 upon BCR activation to stabilize the NF-κB inhibitor TNFAIP3/A20 [PMID:16166635, PMID:29695787, PMID:38630892]. In CD8+ T cells, KLHL6 promotes poly-ubiquitination and proteasomal degradation of TOX to restrain terminal exhaustion, and regulates the PGAM5–Drp1 axis to maintain mitochondrial fitness during chronic TCR stimulation; TCR ligation naturally downregulates KLHL6 via PI3K–AKT-mediated suppression of FOXO1 [PMID:41535474]. Cancer-associated mutations segregate by domain: BTB domain mutations disrupt homodimerization, Cullin3 interaction, and subcellular localization, while Kelch domain mutations alter substrate recognition, with each class producing distinct effects on BCR surface levels and signaling [PMID:29695787, PMID:38630892].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Establishing that KLHL6 is essential for BCR signal transduction answered whether this uncharacterized BTB-Kelch protein has a lymphocyte function, revealing a B-cell-intrinsic requirement for proliferation, Ca²⁺ flux, PLCγ2 activation, and germinal center formation.\",\n      \"evidence\": \"Global and B-cell-conditional knockout mice with BCR cross-linking assays measuring multiple signaling readouts\",\n      \"pmids\": [\"16166635\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular mechanism linking KLHL6 to BCR signaling was unknown\",\n        \"Whether KLHL6 acts as an E3 ligase adaptor was not tested\",\n        \"Role in lymphocyte subsets other than B cells was unexplored\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identifying KLHL6 interaction with Cullin3 and HBXIP/Lamtor5 in B-lymphoma cells, and demonstrating a differentiation block at the transitional type 1 B-cell stage, began connecting KLHL6 to ubiquitin ligase machinery and cell-cycle control.\",\n      \"evidence\": \"Co-immunoprecipitation in BL2 Burkitt lymphoma cells; KLHL6-knockout mouse flow cytometry and gene expression profiling\",\n      \"pmids\": [\"28807996\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"HBXIP interaction based on single Co-IP without reciprocal validation\",\n        \"Direct substrates of KLHL6 ubiquitination were not identified\",\n        \"Relationship between cell-cycle gene deregulation and KLHL6 ligase activity was not established\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating that KLHL6 assembles with Cullin3 into a functional E3 ubiquitin ligase and that Roquin2 is a direct, BCR-activation-dependent substrate established the first complete substrate-to-pathway mechanism: KLHL6 degrades Roquin2 to protect TNFAIP3/A20 mRNA and restrain NF-κB signaling.\",\n      \"evidence\": \"In vitro ubiquitination assay, reciprocal Co-IP/mass spectrometry, Roquin2 Y691F mutagenesis, xenograft models\",\n      \"pmids\": [\"29695787\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether Roquin2 is the substrate responsible for the original BCR signaling defect in KO mice was not resolved\",\n        \"Full substrate repertoire of the CRL3-KLHL6 complex remained unknown\",\n        \"How cancer mutations specifically corrupt ligase function at the structural level was unclear\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Biophysical characterization showing that full-length KLHL6 forms homomultimers and that Cullin3-NTD stabilizes the complex provided the first structural insight into how the functional ligase is assembled.\",\n      \"evidence\": \"Gel filtration chromatography and negative-staining electron microscopy of purified KLHL6 and KLHL6–Cul3NTD complexes\",\n      \"pmids\": [\"37286065\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"High-resolution structure of KLHL6 or its Cullin3 complex was not determined\",\n        \"Stoichiometry of the multimer and how it relates to substrate engagement was unresolved\",\n        \"Structural basis for cancer mutation effects on dimerization was not modeled\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of CD79A and CD79B as direct KLHL6 ubiquitination targets, together with domain-specific mutant analysis, resolved how KLHL6 controls surface BCR homeostasis and explained the divergent oncogenic consequences of BTB versus Kelch domain mutations.\",\n      \"evidence\": \"High-throughput protein interactome screens, domain-specific mutagenesis (BTB and Kelch), surface BCR quantification, KLHL6 silencing\",\n      \"pmids\": [\"38630892\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether CD79A/CD79B degradation fully accounts for the KO BCR signaling phenotype was not tested\",\n        \"Integration of Roquin2 and CD79A/B degradation into a unified signaling model was not performed\",\n        \"Effect of Kelch domain gain-of-function mutations on non-BCR substrates was unexplored\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extending KLHL6 function to CD8+ T cells revealed it counteracts exhaustion via two parallel ubiquitin-dependent mechanisms — degrading TOX to limit exhaustion commitment and degrading PGAM5 to preserve mitochondrial integrity — while itself being transcriptionally controlled by FOXO1 downstream of TCR–PI3K–AKT signaling.\",\n      \"evidence\": \"In vivo CRISPR screens, enforced KLHL6 expression in T cells, poly-ubiquitination assays, mitochondrial fission assays, tumor and viral infection models\",\n      \"pmids\": [\"41535474\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether B-cell substrates (CD79A/B, Roquin2) are also regulated by KLHL6 in T cells was not addressed\",\n        \"Relative contribution of TOX versus PGAM5 degradation to anti-exhaustion phenotype was not dissected\",\n        \"Therapeutic applicability of enforced KLHL6 expression in adoptive T-cell therapy was not tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A unified structural and signaling model integrating KLHL6's multiple substrates across B and T cells, its oligomeric architecture, and the precise structural basis by which cancer mutations corrupt its function remains to be established.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No high-resolution structure of the KLHL6–Cullin3 complex or substrate-bound state exists\",\n        \"Complete substrate repertoire across immune cell types is unknown\",\n        \"Whether KLHL6 has functions outside the immune system has not been systematically investigated\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 3, 5]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 3, 5]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 3, 5]}\n    ],\n    \"complexes\": [\"CRL3-KLHL6 (Cullin3-RING E3 ligase)\"],\n    \"partners\": [\"CUL3\", \"CD79A\", \"CD79B\", \"RC3H2\", \"TOX\", \"PGAM5\", \"LAMTOR5\"],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"KLHL6 is a BTB-Kelch family substrate adaptor for Cullin3-RING E3 ubiquitin ligase complexes that controls lymphocyte signaling homeostasis by targeting key substrates for proteasomal degradation. In B cells, KLHL6 is essential for BCR signal transduction and germinal center formation; BCR activation triggers KLHL6-dependent ubiquitination of roquin2 and the BCR subunits CD79A/CD79B, thereby tuning surface BCR levels and downstream NF-κB signaling [PMID:16166635, PMID:29695787, PMID:38630892]. In T cells, KLHL6 ubiquitinates TOX to restrain terminal exhaustion and regulates the PGAM5–Drp1 axis to maintain mitochondrial fitness, with its expression suppressed by chronic TCR stimulation through PI3K–AKT/FOXO1 signaling [PMID:41535474]. Cancer-associated KLHL6 mutations disrupt Cullin3 binding or alter substrate engagement, and loss of KLHL6 function contributes to activated B-cell diffuse large B-cell lymphoma pathogenesis [PMID:29695787, PMID:38630892].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Establishing that KLHL6 is required cell-intrinsically for BCR signal transduction and germinal center B cell biology answered the foundational question of whether this uncharacterized BTB-Kelch protein has a physiological role in the immune system.\",\n      \"evidence\": \"Global and conditional knockout mice with B-cell proliferation, Ca²⁺ flux, and PLCγ2 activation assays\",\n      \"pmids\": [\"16166635\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Molecular mechanism of how KLHL6 influences BCR signaling was unknown\",\n        \"No substrates or E3 ligase activity had been demonstrated\",\n        \"Role in non-B lymphocytes unexplored\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identification of KLHL6 as a Cullin3 adaptor and its interaction with HBXIP/Lamtor5 placed KLHL6 within the CRL3 ubiquitin ligase framework and linked it to cell-cycle gene regulation during the transitional B cell checkpoint.\",\n      \"evidence\": \"Co-immunoprecipitation in BL2 cells; gene expression profiling and flow cytometry of Klhl6-deficient B cells\",\n      \"pmids\": [\"28807996\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"HBXIP interaction shown by single Co-IP without reciprocal validation\",\n        \"No direct ubiquitination substrates identified\",\n        \"Causal relationship between APC/C target gene upregulation and B cell block not established\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating that KLHL6–Cullin3 ubiquitinates roquin2 upon BCR activation, and that cancer-associated KLHL6 mutations abolish this activity, provided the first defined substrate and a direct mechanistic link between KLHL6 loss-of-function and DLBCL pathogenesis via TNFAIP3/NF-κB deregulation.\",\n      \"evidence\": \"AP-MS, Co-IP, ubiquitination assays, Y691F mutagenesis of roquin2, xenograft models, RNA decay assays\",\n      \"pmids\": [\"29695787\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether roquin2 is the primary BCR-signaling-relevant substrate was unclear\",\n        \"Structural basis of KLHL6–substrate recognition unknown\",\n        \"Extent of the KLHL6 substrate repertoire beyond roquin2 not addressed\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Biochemical and structural characterization revealed that full-length KLHL6 forms homomultimers stabilized by Cullin3 binding, providing an architectural basis for understanding how the CRL3-KLHL6 complex assembles.\",\n      \"evidence\": \"Recombinant protein gel filtration and negative-staining electron microscopy\",\n      \"pmids\": [\"37286065\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No high-resolution structure was obtained\",\n        \"Functional significance of homomultimerization for ligase activity not tested\",\n        \"Single study without independent replication\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identification of CD79A and CD79B as direct KLHL6 ubiquitination targets resolved how KLHL6 tunes surface BCR levels and explained the domain-specific consequences of cancer mutations — BTB mutants increase and Kelch mutants decrease BCR signaling.\",\n      \"evidence\": \"High-throughput interactome screens, Co-IP, flow cytometry, domain-specific mutagenesis, KLHL6 silencing\",\n      \"pmids\": [\"38630892\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis of Kelch domain recognition of CD79A/B not determined\",\n        \"In vivo validation in mouse models not reported\",\n        \"Whether CD79A/B and roquin2 targeting are coordinated or independent events unknown\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extending KLHL6 function to T cells, this work showed KLHL6 ubiquitinates TOX to prevent terminal exhaustion and restrains PGAM5–Drp1-mediated mitochondrial fission, while its own expression is negatively regulated by PI3K–AKT/FOXO1 upon chronic TCR stimulation, establishing KLHL6 as a therapeutic target for reinvigorating anti-tumor immunity.\",\n      \"evidence\": \"In vivo CRISPR screens, ubiquitination assays, Co-IP, mitochondrial fission assays, adoptive T cell transfer in tumor and viral models\",\n      \"pmids\": [\"41535474\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether TOX and PGAM5 ubiquitination share structural determinants recognized by the Kelch domain is unknown\",\n        \"Relative contribution of TOX degradation vs. mitochondrial fitness to T cell rejuvenation not disentangled\",\n        \"Potential off-target effects of enforced KLHL6 expression on other CRL3 substrates not assessed\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structure of the KLHL6–Cullin3 complex bound to substrate, and a comprehensive substrate catalog across lymphocyte lineages, are needed to unify the diverse substrate specificities and inform therapeutic strategies.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No high-resolution cryo-EM or crystal structure of KLHL6–Cullin3–substrate ternary complex\",\n        \"Full substrate repertoire across B, T, and other cell types not systematically defined\",\n        \"In vivo consequences of enforcing KLHL6 expression for immunotherapy not clinically evaluated\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 4, 5]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [1, 2, 4]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 2, 4, 5]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [2, 4, 5]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 4, 5]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"complexes\": [\n      \"CRL3-KLHL6 (Cullin3-RING E3 ubiquitin ligase)\"\n    ],\n    \"partners\": [\n      \"CUL3\",\n      \"RC3H2\",\n      \"CD79A\",\n      \"CD79B\",\n      \"TOX\",\n      \"PGAM5\",\n      \"LAMTOR5\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}