{"gene":"CLEC4D","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":2004,"finding":"Human CLECSF8 (CLEC4D) is a type II membrane glycoprotein of 215 amino acids with a single carbohydrate recognition domain (CRD) and no consensus signaling motifs in its cytoplasmic tail. It is expressed in a monocyte/macrophage-restricted pattern, and cross-linking of the receptor leads to rapid internalization, identifying it as an endocytic receptor.","method":"cDNA cloning, biochemical characterization of transfected cells, cross-linking/internalization assay","journal":"European Journal of Immunology","confidence":"Medium","confidence_rationale":"Tier 2 — direct biochemical characterization and functional internalization assay in transfected cells, single lab","pmids":["14971047"],"is_preprint":false},{"year":2013,"finding":"Clec4d plays a non-redundant role in resolution of Gram-negative (Klebsiella pneumoniae) pneumonic sepsis: Clec4d-/- mice show progressive bacteremia, hyperinflammatory sepsis, and massive neutrophil accumulation in lungs, but Clec4d-/- neutrophils have no intrinsic defect in bacterial killing, suggesting Clec4d facilitates neutrophil turnover/resolution of inflammation rather than direct bactericidal activity.","method":"Clec4d knockout mouse infection model, bacterial burden quantification, histopathology, neutrophil functional assays","journal":"Journal of Leukocyte Biology","confidence":"Medium","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotype, single lab","pmids":["23709686"],"is_preprint":false},{"year":2015,"finding":"CLECSF8 (CLEC4D/MCL) is required for anti-mycobacterial host defense: Clecsf8-/- mice exhibit higher M. tuberculosis burdens, increased mortality, exacerbated pulmonary neutrophil recruitment, and reduced mycobacterial uptake by pulmonary leukocytes. Opsonization of bacteria rescued the phagocytic defect and reduced bacterial burdens, indicating CLEC4D mediates mycobacterial phagocytosis. A human CLECSF8 polymorphism associates with increased susceptibility to pulmonary tuberculosis.","method":"Clecsf8 knockout mouse M. tuberculosis infection model, bacterial burden measurement, flow cytometry of leukocyte populations, opsonization rescue experiment, human genetic association","journal":"Cell Host & Microbe","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (KO mouse, phagocytosis assay, opsonization rescue, human genetics) establishing a non-redundant in vivo function","pmids":["25674984"],"is_preprint":false},{"year":2018,"finding":"Dectin-3 (the mouse ortholog of CLEC4D, encoded by Clec4d) directly recognizes glucuronoxylomannan (GXM) from Cryptococcus neoformans serotype AD and C. gattii serotype B, activating NF-κB and ERK signaling pathways to induce pro-inflammatory cytokine production. Dectin-3- and CARD9-deficient mice are highly susceptible to pulmonary C.n-AD and C.g-B infection, with impaired alveolar macrophage accumulation and killing, and cytokine induction by these GXMs was abolished by Dectin-3 or CARD9 deficiency.","method":"Direct binding assay (Dectin-3 as GXM receptor), NF-κB/ERK reporter assays, Dectin-3 and CARD9 knockout mouse infection model, cytokine measurement, alveolar macrophage functional assays","journal":"Frontiers in Immunology","confidence":"High","confidence_rationale":"Tier 1-2 — direct receptor-ligand identification, signaling pathway dissection, and in vivo KO validation with multiple readouts","pmids":["30131805"],"is_preprint":false}],"current_model":"CLEC4D (CLECSF8) is a monocyte/macrophage-expressed type II transmembrane C-type lectin receptor that functions as an endocytic pattern recognition receptor; it directly recognizes mycobacterial ligands and fungal glucuronoxylomannan (GXM) to activate NF-κB and ERK signaling via CARD9, mediates phagocytosis of mycobacteria, and is required in vivo for resolution of bacterial and fungal pulmonary infections, in part by facilitating neutrophil turnover at sites of inflammation."},"narrative":{"teleology":[{"year":2004,"claim":"The molecular identity and basic receptor behavior of CLEC4D were established, revealing it as a monocyte/macrophage-restricted endocytic receptor with a single CRD but no cytoplasmic signaling motifs, raising the question of how it signals and what ligands it recognizes.","evidence":"cDNA cloning, biochemical characterization in transfected cells, cross-linking/internalization assay","pmids":["14971047"],"confidence":"Medium","gaps":["Natural ligands unidentified","Signaling mechanism unknown given absence of cytoplasmic signaling motifs","In vivo function not tested"]},{"year":2013,"claim":"Clec4d was shown to be non-redundantly required for resolution of Gram-negative pneumonic sepsis in vivo, but the mechanism was not direct bacterial killing — instead Clec4d facilitates neutrophil turnover at inflammatory sites, establishing a role in inflammation resolution rather than just pathogen recognition.","evidence":"Clec4d knockout mouse Klebsiella pneumoniae infection model with bacterial burden quantification, histopathology, and neutrophil functional assays","pmids":["23709686"],"confidence":"Medium","gaps":["Single-lab KO study; mechanism of neutrophil turnover regulation not defined","Direct ligand on Klebsiella not identified","Signaling pathway downstream of Clec4d in this context unknown"]},{"year":2015,"claim":"CLEC4D was established as a phagocytic receptor for mycobacteria: knockout mice had higher M. tuberculosis burdens and mortality, and the phagocytic defect was rescued by opsonization, directly linking CLEC4D to mycobacterial uptake. A human genetic association further connected CLEC4D to tuberculosis susceptibility.","evidence":"Clecsf8 knockout mouse M. tuberculosis infection, bacterial burden measurement, flow cytometry, opsonization rescue, human genetic association study","pmids":["25674984"],"confidence":"High","gaps":["Specific mycobacterial ligand for CLEC4D not identified","Human genetic association is correlative; causal mechanism in humans not proven","How CLEC4D signals without cytoplasmic signaling motifs during phagocytosis not resolved"]},{"year":2018,"claim":"The signaling question was resolved: CLEC4D directly binds fungal glucuronoxylomannan and activates NF-κB and ERK via the CARD9 adaptor, connecting receptor engagement to pro-inflammatory cytokine production and establishing the CLEC4D–CARD9 axis as essential for anti-cryptococcal immunity.","evidence":"Direct binding assay, NF-κB/ERK reporter assays, Dectin-3 and CARD9 knockout mouse Cryptococcus infection model, cytokine measurement, alveolar macrophage functional assays","pmids":["30131805"],"confidence":"High","gaps":["How CLEC4D couples to CARD9 without cytoplasmic signaling motifs (likely via an associated signaling chain such as FcRγ) not molecularly defined in these studies","Structural basis of GXM recognition by the CRD not determined","Whether the CARD9-dependent pathway also operates during antibacterial responses not tested"]},{"year":null,"claim":"The molecular mechanism by which CLEC4D, which lacks cytoplasmic signaling motifs, couples to the CARD9 signaling cascade remains undefined, and the specific microbial ligands recognized during bacterial (Klebsiella, M. tuberculosis) infections have not been identified.","evidence":"","pmids":[],"confidence":"Low","gaps":["Transmembrane signaling partner (e.g., FcRγ chain association) not biochemically validated","No structural model for CLEC4D–ligand interaction","Contribution to human disease beyond tuberculosis association not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,3]},{"term_id":"GO:0038024","term_label":"cargo receptor activity","supporting_discovery_ids":[0,2]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[1,2,3]}],"complexes":[],"partners":["CARD9"],"other_free_text":[]},"mechanistic_narrative":"CLEC4D is a monocyte/macrophage-restricted type II transmembrane C-type lectin receptor that functions as an endocytic pattern recognition receptor mediating phagocytosis and innate immune signaling against bacterial and fungal pathogens. It is a 215-amino acid glycoprotein with a single carbohydrate recognition domain that undergoes rapid internalization upon cross-linking and directly recognizes microbial ligands including fungal glucuronoxylomannan, activating NF-κB and ERK signaling via the CARD9 adaptor to drive pro-inflammatory cytokine production [PMID:14971047, PMID:30131805]. Clec4d-deficient mice display increased susceptibility to Klebsiella pneumoniae sepsis, Mycobacterium tuberculosis infection, and Cryptococcus pulmonary infection, with exacerbated neutrophil accumulation and impaired pathogen clearance, indicating a non-redundant role in both pathogen uptake and resolution of pulmonary inflammation [PMID:23709686, PMID:25674984, PMID:30131805]. A human CLEC4D polymorphism is associated with increased susceptibility to pulmonary tuberculosis [PMID:25674984]."},"prefetch_data":{"uniprot":{"accession":"Q8WXI8","full_name":"C-type lectin domain family 4 member D","aliases":["C-type lectin superfamily member 8","C-type lectin-like receptor 6","CLEC-6","Dendritic cell-associated C-type lectin 3","DC-associated C-type lectin 3","Dectin-3"],"length_aa":215,"mass_kda":24.7,"function":"Calcium-dependent lectin that acts as a pattern recognition receptor (PRR) of the innate immune system: recognizes damage-associated molecular patterns (DAMPs) of pathogen-associated molecular patterns (PAMPs) of bacteria and fungi (PubMed:23602766, PubMed:23911656). The PAMPs include alpha-mannans on C.albicans hypheas and mycobacterial trehalose 6,6'-dimycolate (TDM) (PubMed:23602766, PubMed:23911656). Interacts with signaling adapter Fc receptor gamma chain/FCER1G, likely via CLEC4E, to form a functional complex in myeloid cells (By similarity). Binding of mycobacterial TDM or C.albicans alpha-mannans to this receptor complex leads to phosphorylation of the immunoreceptor tyrosine-based activation motif (ITAM) of FCER1G, triggering activation of SYK, CARD9 and NF-kappa-B, consequently driving maturation of antigen-presenting cells and shaping antigen-specific priming of T-cells toward effector T-helper 1 and T-helper 17 cell subtypes (PubMed:23602766, PubMed:23911656). The heterodimer formed with CLEC6A is active against fungal infection (PubMed:23911656). Functions as an endocytic receptor (PubMed:14971047). May be involved in antigen uptake at the site of infection, either for clearance of the antigen, or for processing and further presentation to T-cells (PubMed:14971047)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q8WXI8/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CLEC4D","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/CLEC4D","total_profiled":1310},"omim":[{"mim_id":"619223","title":"IMMUNODEFICIENCY 77; IMD77","url":"https://www.omim.org/entry/619223"},{"mim_id":"613579","title":"C-TYPE LECTIN DOMAIN FAMILY 6, MEMBER A; CLEC6A","url":"https://www.omim.org/entry/613579"},{"mim_id":"609964","title":"C-TYPE LECTIN DOMAIN FAMILY 4, MEMBER D; CLEC4D","url":"https://www.omim.org/entry/609964"},{"mim_id":"609962","title":"C-TYPE LECTIN DOMAIN FAMILY 4, MEMBER E; CLEC4E","url":"https://www.omim.org/entry/609962"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"bone marrow","ntpm":61.1}],"url":"https://www.proteinatlas.org/search/CLEC4D"},"hgnc":{"alias_symbol":["Mpcl","CD368","MCL","Dectin-3"],"prev_symbol":["CLECSF8"]},"alphafold":{"accession":"Q8WXI8","domains":[{"cath_id":"3.10.100.10","chopping":"59-215","consensus_level":"medium","plddt":91.3611,"start":59,"end":215}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WXI8","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WXI8-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WXI8-F1-predicted_aligned_error_v6.png","plddt_mean":86.06},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CLEC4D","jax_strain_url":"https://www.jax.org/strain/search?query=CLEC4D"},"sequence":{"accession":"Q8WXI8","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8WXI8.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8WXI8/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WXI8"}},"corpus_meta":[{"pmid":"14668867","id":"PMC_14668867","title":"Development 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defines Mcl⁻1 survival dependency in neuroblastoma.","date":"2015","source":"Cancer biology & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/25756510","citation_count":20,"is_preprint":false},{"pmid":"30201826","id":"PMC_30201826","title":"Repurposing of mTOR Complex Inhibitors Attenuates MCL-1 and Sensitizes to PARP Inhibition.","date":"2018","source":"Molecular cancer research : MCR","url":"https://pubmed.ncbi.nlm.nih.gov/30201826","citation_count":20,"is_preprint":false},{"pmid":"31031018","id":"PMC_31031018","title":"Discovery of pyrazolopyrimidine derivatives as potent BTK inhibitors with effective anticancer activity in MCL.","date":"2019","source":"Bioorganic chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/31031018","citation_count":19,"is_preprint":false},{"pmid":"33658484","id":"PMC_33658484","title":"Phosphatase PP2A enhances MCL-1 protein half-life in multiple myeloma cells.","date":"2021","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/33658484","citation_count":18,"is_preprint":false},{"pmid":"33763603","id":"PMC_33763603","title":"Photocatalytic proximity labelling of MCL-1 by a BH3 ligand.","date":"2019","source":"Communications chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/33763603","citation_count":18,"is_preprint":false},{"pmid":"19285955","id":"PMC_19285955","title":"IEX-1-induced cell death requires BIM and is modulated by MCL-1.","date":"2009","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/19285955","citation_count":18,"is_preprint":false},{"pmid":"32587776","id":"PMC_32587776","title":"DYRK1A suppression restrains Mcl-1 expression and sensitizes NSCLC cells to Bcl-2 inhibitors.","date":"2020","source":"Cancer biology & medicine","url":"https://pubmed.ncbi.nlm.nih.gov/32587776","citation_count":17,"is_preprint":false},{"pmid":"24260268","id":"PMC_24260268","title":"MCL-1ES induces MCL-1L-dependent BAX- and BAK-independent mitochondrial apoptosis.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24260268","citation_count":17,"is_preprint":false},{"pmid":"28520795","id":"PMC_28520795","title":"BIRC6 mediates imatinib resistance independently of Mcl-1.","date":"2017","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/28520795","citation_count":17,"is_preprint":false},{"pmid":"19821820","id":"PMC_19821820","title":"Immunotoxin BL22 induces apoptosis in mantle cell lymphoma (MCL) cells dependent on Bcl-2 expression.","date":"2009","source":"British journal of haematology","url":"https://pubmed.ncbi.nlm.nih.gov/19821820","citation_count":17,"is_preprint":false},{"pmid":"36226498","id":"PMC_36226498","title":"Inhibition of casein kinase 2 sensitizes mantle cell lymphoma to venetoclax through MCL-1 downregulation.","date":"2023","source":"Haematologica","url":"https://pubmed.ncbi.nlm.nih.gov/36226498","citation_count":16,"is_preprint":false},{"pmid":"29016132","id":"PMC_29016132","title":"Toward Understanding Mcl-1 Promiscuous and Specific Binding Mode.","date":"2017","source":"Journal of chemical information and modeling","url":"https://pubmed.ncbi.nlm.nih.gov/29016132","citation_count":16,"is_preprint":false},{"pmid":"32088497","id":"PMC_32088497","title":"Design, synthesis and biological evaluation of tyrosine derivatives as Mcl-1 inhibitors.","date":"2020","source":"European journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/32088497","citation_count":16,"is_preprint":false},{"pmid":"29287727","id":"PMC_29287727","title":"Upregulation of Mcl-1 inhibits JQ1-triggered anticancer activity in hepatocellular carcinoma cells.","date":"2017","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/29287727","citation_count":16,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":47495,"output_tokens":1501,"usd":0.0825},"stage2":{"model":"claude-opus-4-6","input_tokens":4467,"output_tokens":1588,"usd":0.093052},"total_usd":0.175552,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard"},"stage1_raw":"Looking at the corpus, I need to identify papers about CLEC4D (also known as CLECSF8, MCL/Dectin-3 in mice) and extract mechanistic findings. The vast majority of papers are about MCL-1 (myeloid cell leukemia 1), an apoptosis-regulating protein that is completely different from CLEC4D (a C-type lectin receptor). I need to carefully distinguish these.\n\nCLEC4D-relevant papers:\n- PMID 25674984: Wilson et al. - CLECSF8/CLEC4D in anti-mycobacterial immunity\n- PMID 14971047: Arce et al. - Human CLECSF8 characterization\n- PMID 23709686: Steichen et al. - Clec4d in Gram-negative pneumonia\n- PMID 30131805: Huang et al. - Dectin-3 (MCL/Clec4d) recognizes GXM from Cryptococcus\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"Human CLECSF8 (CLEC4D) is a type II membrane glycoprotein of 215 amino acids with a single carbohydrate recognition domain (CRD) and no consensus signaling motifs in its cytoplasmic tail. It is expressed in a monocyte/macrophage-restricted pattern, and cross-linking of the receptor leads to rapid internalization, identifying it as an endocytic receptor.\",\n      \"method\": \"cDNA cloning, biochemical characterization of transfected cells, cross-linking/internalization assay\",\n      \"journal\": \"European Journal of Immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct biochemical characterization and functional internalization assay in transfected cells, single lab\",\n      \"pmids\": [\"14971047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Clec4d plays a non-redundant role in resolution of Gram-negative (Klebsiella pneumoniae) pneumonic sepsis: Clec4d-/- mice show progressive bacteremia, hyperinflammatory sepsis, and massive neutrophil accumulation in lungs, but Clec4d-/- neutrophils have no intrinsic defect in bacterial killing, suggesting Clec4d facilitates neutrophil turnover/resolution of inflammation rather than direct bactericidal activity.\",\n      \"method\": \"Clec4d knockout mouse infection model, bacterial burden quantification, histopathology, neutrophil functional assays\",\n      \"journal\": \"Journal of Leukocyte Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype, single lab\",\n      \"pmids\": [\"23709686\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CLECSF8 (CLEC4D/MCL) is required for anti-mycobacterial host defense: Clecsf8-/- mice exhibit higher M. tuberculosis burdens, increased mortality, exacerbated pulmonary neutrophil recruitment, and reduced mycobacterial uptake by pulmonary leukocytes. Opsonization of bacteria rescued the phagocytic defect and reduced bacterial burdens, indicating CLEC4D mediates mycobacterial phagocytosis. A human CLECSF8 polymorphism associates with increased susceptibility to pulmonary tuberculosis.\",\n      \"method\": \"Clecsf8 knockout mouse M. tuberculosis infection model, bacterial burden measurement, flow cytometry of leukocyte populations, opsonization rescue experiment, human genetic association\",\n      \"journal\": \"Cell Host & Microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (KO mouse, phagocytosis assay, opsonization rescue, human genetics) establishing a non-redundant in vivo function\",\n      \"pmids\": [\"25674984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Dectin-3 (the mouse ortholog of CLEC4D, encoded by Clec4d) directly recognizes glucuronoxylomannan (GXM) from Cryptococcus neoformans serotype AD and C. gattii serotype B, activating NF-κB and ERK signaling pathways to induce pro-inflammatory cytokine production. Dectin-3- and CARD9-deficient mice are highly susceptible to pulmonary C.n-AD and C.g-B infection, with impaired alveolar macrophage accumulation and killing, and cytokine induction by these GXMs was abolished by Dectin-3 or CARD9 deficiency.\",\n      \"method\": \"Direct binding assay (Dectin-3 as GXM receptor), NF-κB/ERK reporter assays, Dectin-3 and CARD9 knockout mouse infection model, cytokine measurement, alveolar macrophage functional assays\",\n      \"journal\": \"Frontiers in Immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct receptor-ligand identification, signaling pathway dissection, and in vivo KO validation with multiple readouts\",\n      \"pmids\": [\"30131805\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CLEC4D (CLECSF8) is a monocyte/macrophage-expressed type II transmembrane C-type lectin receptor that functions as an endocytic pattern recognition receptor; it directly recognizes mycobacterial ligands and fungal glucuronoxylomannan (GXM) to activate NF-κB and ERK signaling via CARD9, mediates phagocytosis of mycobacteria, and is required in vivo for resolution of bacterial and fungal pulmonary infections, in part by facilitating neutrophil turnover at sites of inflammation.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CLEC4D is a monocyte/macrophage-restricted type II transmembrane C-type lectin receptor that functions as an endocytic pattern recognition receptor mediating phagocytosis and innate immune signaling against bacterial and fungal pathogens. It is a 215-amino acid glycoprotein with a single carbohydrate recognition domain that undergoes rapid internalization upon cross-linking and directly recognizes microbial ligands including fungal glucuronoxylomannan, activating NF-κB and ERK signaling via the CARD9 adaptor to drive pro-inflammatory cytokine production [PMID:14971047, PMID:30131805]. Clec4d-deficient mice display increased susceptibility to Klebsiella pneumoniae sepsis, Mycobacterium tuberculosis infection, and Cryptococcus pulmonary infection, with exacerbated neutrophil accumulation and impaired pathogen clearance, indicating a non-redundant role in both pathogen uptake and resolution of pulmonary inflammation [PMID:23709686, PMID:25674984, PMID:30131805]. A human CLEC4D polymorphism is associated with increased susceptibility to pulmonary tuberculosis [PMID:25674984].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"The molecular identity and basic receptor behavior of CLEC4D were established, revealing it as a monocyte/macrophage-restricted endocytic receptor with a single CRD but no cytoplasmic signaling motifs, raising the question of how it signals and what ligands it recognizes.\",\n      \"evidence\": \"cDNA cloning, biochemical characterization in transfected cells, cross-linking/internalization assay\",\n      \"pmids\": [\"14971047\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Natural ligands unidentified\",\n        \"Signaling mechanism unknown given absence of cytoplasmic signaling motifs\",\n        \"In vivo function not tested\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Clec4d was shown to be non-redundantly required for resolution of Gram-negative pneumonic sepsis in vivo, but the mechanism was not direct bacterial killing — instead Clec4d facilitates neutrophil turnover at inflammatory sites, establishing a role in inflammation resolution rather than just pathogen recognition.\",\n      \"evidence\": \"Clec4d knockout mouse Klebsiella pneumoniae infection model with bacterial burden quantification, histopathology, and neutrophil functional assays\",\n      \"pmids\": [\"23709686\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab KO study; mechanism of neutrophil turnover regulation not defined\",\n        \"Direct ligand on Klebsiella not identified\",\n        \"Signaling pathway downstream of Clec4d in this context unknown\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"CLEC4D was established as a phagocytic receptor for mycobacteria: knockout mice had higher M. tuberculosis burdens and mortality, and the phagocytic defect was rescued by opsonization, directly linking CLEC4D to mycobacterial uptake. A human genetic association further connected CLEC4D to tuberculosis susceptibility.\",\n      \"evidence\": \"Clecsf8 knockout mouse M. tuberculosis infection, bacterial burden measurement, flow cytometry, opsonization rescue, human genetic association study\",\n      \"pmids\": [\"25674984\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Specific mycobacterial ligand for CLEC4D not identified\",\n        \"Human genetic association is correlative; causal mechanism in humans not proven\",\n        \"How CLEC4D signals without cytoplasmic signaling motifs during phagocytosis not resolved\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The signaling question was resolved: CLEC4D directly binds fungal glucuronoxylomannan and activates NF-κB and ERK via the CARD9 adaptor, connecting receptor engagement to pro-inflammatory cytokine production and establishing the CLEC4D–CARD9 axis as essential for anti-cryptococcal immunity.\",\n      \"evidence\": \"Direct binding assay, NF-κB/ERK reporter assays, Dectin-3 and CARD9 knockout mouse Cryptococcus infection model, cytokine measurement, alveolar macrophage functional assays\",\n      \"pmids\": [\"30131805\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How CLEC4D couples to CARD9 without cytoplasmic signaling motifs (likely via an associated signaling chain such as FcRγ) not molecularly defined in these studies\",\n        \"Structural basis of GXM recognition by the CRD not determined\",\n        \"Whether the CARD9-dependent pathway also operates during antibacterial responses not tested\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular mechanism by which CLEC4D, which lacks cytoplasmic signaling motifs, couples to the CARD9 signaling cascade remains undefined, and the specific microbial ligands recognized during bacterial (Klebsiella, M. tuberculosis) infections have not been identified.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Transmembrane signaling partner (e.g., FcRγ chain association) not biochemically validated\",\n        \"No structural model for CLEC4D–ligand interaction\",\n        \"Contribution to human disease beyond tuberculosis association not established\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"GO:0038024\", \"supporting_discovery_ids\": [0, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [1, 2, 3]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"CARD9\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}