{"gene":"CD209","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":2000,"finding":"DC-SIGN supports tethering and rolling of DC-SIGN-positive cells on the vascular ligand ICAM-2 under shear flow, and the DC-SIGN-ICAM-2 interaction regulates chemokine-induced transmigration of DCs across resting and activated endothelium, establishing DC-SIGN as central to DC trafficking.","method":"Shear flow adhesion assay, transmigration assay across endothelial monolayers","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 — clean functional assay with defined molecular interaction and cellular phenotype, replicated across multiple endothelial conditions","pmids":["11017109"],"is_preprint":false},{"year":2002,"finding":"DC-SIGN mediates rapid internalization of intact HIV into a low-pH, non-lysosomal compartment; internalized virus retains infectivity; removal of the DC-SIGN cytoplasmic tail reduced viral uptake and abrogated trans-enhancement of T cell infection, establishing the cytoplasmic tail as required for endocytosis-dependent trans-infection.","method":"Cytoplasmic tail deletion mutants, HIV internalization assay, trans-infection T cell assay","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 1-2 — mutagenesis of cytoplasmic tail combined with functional internalization and trans-infection assays","pmids":["11825572"],"is_preprint":false},{"year":2002,"finding":"HIV-1 Nef protein causes upregulation of DC-SIGN surface levels on HIV-1-infected DCs by inhibiting DC-SIGN endocytosis, which dramatically increases DC-T lymphocyte clustering and HIV-1 transmission.","method":"HIV-1 infection of DCs, Nef expression constructs, flow cytometry for DC-SIGN surface levels, clustering and transmission assays","journal":"Immunity","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods linking Nef to DC-SIGN endocytosis inhibition and functional transmission","pmids":["11825573"],"is_preprint":false},{"year":2003,"finding":"DC-SIGN captures and internalizes intact Mycobacterium bovis BCG through the mycobacterial cell wall component ManLAM; ManLAM binding to DC-SIGN prevents mycobacteria- or LPS-induced DC maturation by interfering with TLR-mediated signals; blocking antibodies against DC-SIGN reverse this immunosuppressive effect.","method":"Antibody blocking assays, DC maturation assays (cytokine production, surface marker upregulation), ManLAM binding studies","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal assays with specific antibody blocking and defined molecular ligand (ManLAM), replicated across labs","pmids":["12515809"],"is_preprint":false},{"year":2003,"finding":"DC-SIGN is the major receptor for M. tuberculosis entry into human monocyte-derived DCs; the mycobacteria-specific lipoglycan LAM was identified as a key DC-SIGN ligand; complement receptor 3 and mannose receptor play a minor role in mycobacterial binding to DCs.","method":"Antibody blocking, receptor-specific inhibition, comparative receptor analysis on DCs and macrophages","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 — receptor comparison with antibody blocking and defined ligand identification, independently replicated","pmids":["12515819"],"is_preprint":false},{"year":2006,"finding":"DC-SIGN specificity for mannose- and fucose-containing glycans was mapped using a large glycan array; DC-SIGN binds with Kd <2 µM to multivalent Lewis x (Galbeta1-4(Fucalpha1-3)GlcNAc) trisaccharides; selective binding observed to oligomannose-type N-glycans and LacdiNAc-fucose; no binding to core-fucose-linked N-glycans.","method":"Glycan array screening, binding affinity measurements","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1-2 — comprehensive glycan array with quantitative binding data across >100 glycan structures","pmids":["17055489"],"is_preprint":false},{"year":2007,"finding":"DC-SIGN activation by HIV or DC-SIGN-specific antibody induces signaling via the Rho guanine nucleotide-exchange factor LARG, leading to increased Rho-GTPase activity; this LARG activation is required for formation of virus-T cell synapses, while DC-SIGN engagement downregulates MHC class II and interferon-response genes and upregulates ATF3.","method":"Large-scale gene expression profiling, phosphoproteomic analysis of tyrosine-phosphorylated proteome, functional virus-T cell synapse assay","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 1-2 — multi-omic analysis combined with functional viral synapse assay identifying specific GEF (LARG) as signaling intermediate","pmids":["17496896"],"is_preprint":false},{"year":2008,"finding":"HIV-1 gp120 binding to DC-SIGN induces kinase Raf-1-dependent phosphorylation of NF-κB subunit p65 at Ser276, which recruits the transcription-elongation factor pTEF-b to nascent viral transcripts; pTEF-b-mediated phosphorylation of RNA polymerase II at Ser2 then enables transcription elongation and generation of full-length viral transcripts required for HIV-1 replication in DCs.","method":"Signaling pathway dissection, phosphorylation assays, inhibitor studies, transcription elongation assays","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 1-2 — mechanistically dissected signaling cascade with specific phosphorylation sites, multiple inhibitors, and functional viral replication readout","pmids":["20364151"],"is_preprint":false},{"year":2009,"finding":"DC-SIGN's neck domain controls pH-sensitive oligomerization: the extracellular domain exists in equilibrium between monomeric and tetrameric states dependent on pH and ionic strength; SAXS-based molecular envelope demonstrates the neck domain is central to oligomerization, extended conformation, and carbohydrate recognition domain organization, implicating pH-driven dissociation in ligand release after internalization.","method":"Solution X-ray scattering (SAXS), hydrodynamic measurements, pH-dependent oligomerization assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — SAXS structural analysis with functional pH dependence data, mechanistically linking neck domain to oligomerization and ligand release","pmids":["19502234"],"is_preprint":false},{"year":2009,"finding":"Surface force measurements show DC-SIGN is in an extended conformation on membranes; glycan binding is associated with a conformational change that repositions the carbohydrate-recognition domains; lateral mobility of membrane-bound ligands enhances engagement of multiple CRDs in the receptor oligomer with appropriately spaced ligands.","method":"Surface force measurements between apposed lipid bilayers, neoglycolipid binding studies","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — biophysical reconstitution with direct force measurements revealing conformational change upon ligand binding","pmids":["19553201"],"is_preprint":false},{"year":2011,"finding":"DC-SIGN ligation on DCs by antibodies, mannan, or measles virus causes rapid activation of neutral and acid sphingomyelinases (SMase), leading to ceramide accumulation in the outer membrane leaflet; SMase activation promotes DC-SIGN signaling and recruits CD150 from intracellular LAMP-1+ compartments to the surface where it co-clusters with DC-SIGN, enhancing measles virus uptake.","method":"SMase activity assays, ceramide detection, co-clustering analysis, confocal microscopy of CD150 trafficking","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal biochemical and imaging methods linking DC-SIGN ligation to SMase activation and receptor co-clustering","pmids":["21379338"],"is_preprint":false},{"year":2011,"finding":"DC-SIGN acts as a receptor for phleboviruses (Rift Valley fever and Uukuniemi viruses) by binding viral glycoproteins via high-mannose N-glycans; DC-SIGN is required for both viral attachment and endocytosis; an endocytosis-defective DC-SIGN mutant cannot mediate virus uptake; internalized virus separates from DC-SIGN and traffics to late endosomes.","method":"DC-SIGN endocytosis-defective mutants, live-cell virus-receptor clustering visualization, viral infection assays","journal":"Cell host & microbe","confidence":"High","confidence_rationale":"Tier 1-2 — endocytosis-defective mutant analysis, live-cell imaging, and viral trafficking studies with defined glycan ligand","pmids":["21767814"],"is_preprint":false},{"year":2006,"finding":"DC-SIGN serves as a novel attachment receptor for both laboratory-adapted and wild-type measles virus strains via the MV glycoproteins F and H; DC-SIGN does not support MV entry (no susceptibility in DC-SIGN-transfected CHO cells) but is required for efficient MV infection of immature DCs in cis by enhancing CD46/CD150-mediated infection.","method":"DC-SIGN transfection in CHO cells, antibody blocking, attachment and infection assays","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 — receptor-transfection experiments with defined ligands (MV-F and MV-H) and functional infection readout distinguishing attachment from entry","pmids":["16537615"],"is_preprint":false},{"year":2008,"finding":"Human herpesvirus 8 (HHV-8) uses DC-SIGN as an entry receptor in B cells; DC-SIGN-mediated endocytosis is required for HHV-8 infection, as DC-SIGN lacking the transmembrane domain (unable to mediate endocytosis) cannot support infection; HHV-8 infection of B cells increases DC-SIGN expression and decreases CD20 and MHC class I.","method":"DC-SIGN truncation mutants, endocytic pathway inhibitors, HHV-8 infection assays (viral DNA, lytic/latency protein expression, infectious virus production)","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 2 — transmembrane domain truncation mutant and endocytic inhibitors with multiple functional infection readouts","pmids":["18337571"],"is_preprint":false},{"year":2008,"finding":"DC-SIGN binds HHV-8 glycoprotein B (gB) in a dose-dependent manner via high-mannose carbohydrate structures on gB; key amino acids in the DC-SIGN carbohydrate recognition domain are required for HHV-8 infection.","method":"Biochemical binding assay (gB-DC-SIGN interaction), site-directed mutagenesis of DC-SIGN CRD, infection assays","journal":"Virus research","confidence":"Medium","confidence_rationale":"Tier 1-2 — direct binding assay with mutagenesis identifying CRD residues, single lab","pmids":["25018023"],"is_preprint":false},{"year":2006,"finding":"DC-SIGN mediates binding and phagocytosis of E. coli through interactions with the complete core region of LPS (outer core); pathogenic E. coli strains expressing O-antigen, which masks core LPS, are not phagocytosed via DC-SIGN.","method":"LPS core mutants of E. coli, phagocytosis assays in DC-SIGN-expressing cells","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — systematic LPS mutant panel across four Gram-negative species identifying N-acetylglucosamine in core LPS as DC-SIGN ligand","pmids":["16951363"],"is_preprint":false},{"year":2009,"finding":"Hexamannosylated PIM6 (containing terminal alpha(1→2)-linked mannosyl residues identical to ManLAM caps) is a high-affinity DC-SIGN ligand; however, a PIM6-deficient BCG mutant and a PIM6/ManLAM double knockout bound DC-SIGN similarly to wild-type, indicating other unknown mycobacterial ligands dominate the DC-SIGN interaction.","method":"Synthetic and natural PIM binding assays, M. bovis BCG knockout strains (ΔpimE, ΔpimE ΔcapA), DC binding assays, cytokine measurement","journal":"Infection and immunity","confidence":"High","confidence_rationale":"Tier 2 — defined synthetic ligands combined with genetic knockout strains and functional DC assays","pmids":["19651855"],"is_preprint":false},{"year":2010,"finding":"DC-SIGN clusters on the plasma membrane of immature DCs are preferentially localized to the leading edge of the lamellipod and undergo directed lateral mobility at high velocity (~1420 nm/s) from the leading edge to medial lamellar sites where endocytosis occurs, suggesting a mechanism for pathogen capture followed by internalization.","method":"Live-cell fluorescence microscopy, single-particle tracking, FRAP, colocalization with endocytic markers","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 — direct live-cell imaging with single-particle tracking and functional colocalization with endocytic activity","pmids":["18270264"],"is_preprint":false},{"year":2007,"finding":"DC-SIGN receptors are organized in nanosized domains (clusters) on the dendritic cell plasma membrane, with ~80% of receptors in nanoclusters; heterogeneous molecular packing density within clusters was revealed by near-field scanning optical microscopy with single-molecule resolution.","method":"Near-field scanning optical microscopy (NSOM), single-molecule detection, sequential photobleaching","journal":"Chemphyschem","confidence":"Medium","confidence_rationale":"Tier 2 — high-resolution single-molecule imaging on intact DCs revealing nanoscale receptor organization","pmids":["17577901"],"is_preprint":false},{"year":2006,"finding":"CD4 coexpression with DC-SIGN impairs HIV-1 transmission to T cells: CD4 promotes internalization and intracellular retention of HIV-1 into late endosomal compartments (CD63+/CD81+), and Nef-mediated CD4 downregulation on MDDCs correlates with enhanced viral transmission.","method":"DC-SIGN-CD4 co-expression in Raji cells, HIV-1 internalization assays, confocal microscopy, late endosome markers","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple cell systems with co-expression constructs and organelle marker colocalization","pmids":["17151103"],"is_preprint":false},{"year":2014,"finding":"NMR structural characterization of DC-SIGN CRD interaction with Lewis X (Le^X) trisaccharide reveals significant chemical shift perturbations identifying residues near the binding site; STD and trNOE NMR experiments defined binding epitopes and bound conformations of Le^X distinct from those in previous crystal structures.","method":"2D NMR (HSQC), STD-NMR, transferred NOE NMR, molecular modeling","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 — NMR structural characterization with multiple complementary NMR experiments and molecular modeling","pmids":["25121780"],"is_preprint":false},{"year":2014,"finding":"Crystal structures of the DC-SIGN carbohydrate recognition domain complexed with glycomimetic antagonists (pseudomannobioside and pseudomannotrioside) reveal identical binding modes despite different inhibitory potencies; compound 2 (pseudomannotrioside) clusters DC-SIGN tetramers without multivalent scaffold, as determined by ITC, analytical ultracentrifugation, and DLS.","method":"X-ray crystallography, isothermal titration calorimetry (ITC), analytical ultracentrifugation, dynamic light scattering, SPR competition","journal":"ACS chemical biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure combined with multiple biophysical methods demonstrating tetramer clustering by monovalent ligand","pmids":["24749535"],"is_preprint":false},{"year":2019,"finding":"Antigen particle size determines DC-SIGN-mediated intracellular routing: soluble glycopolymers are directed to transferrin-labeled early endosomes, while particulate antigens (aggregated polymers) are diverted to surface-accessible invaginated pockets that also harbor HIV-1, indicating antigen structure controls DC-SIGN trafficking fate.","method":"Ring-opening metathesis polymerization of glycopolymers, confocal microscopy, colocalization with endosomal markers","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — systematic variation of antigen structure with colocalization to defined endosomal compartments across multiple conditions","pmids":["31270240"],"is_preprint":false},{"year":2011,"finding":"Semen clusterin, but not serum clusterin, binds DC-SIGN with high affinity (Kd 76 nM) through fucose-containing blood-type antigens (Le^x and Le^y) expressed on its glycans, and can abrogate HIV-1 binding to DC-SIGN.","method":"Affinity binding assays, blocking of HIV-1 capture, glycan structural analysis (Le^x/Le^y identification)","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — defined glycan ligands on clusterin with quantitative binding affinity and functional HIV blocking, single lab","pmids":["22013110"],"is_preprint":false},{"year":2015,"finding":"MUC1 is identified as the major milk glycoprotein that binds to the lectin domain of DC-SIGN in human milk, via Lewis x-type oligosaccharides, and prevents pathogen interaction with DC-SIGN; this effect is specific to human milk and not present in formula, bovine, or camel milk.","method":"Affinity binding assays, glycan inhibition, comparative milk analysis","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 3 — pulldown/binding assay identifying MUC1 as DC-SIGN ligand with functional blocking assay, single lab","pmids":["25821450"],"is_preprint":false},{"year":2015,"finding":"LECT2 (leukocyte cell-derived chemotaxin 2) signals through CD209/DC-SIGN receptor to phosphorylate JNK in human endothelial cells and macrophages, inducing ICAM-1, TNFα, MCP-1, and IL-1β expression; CD209 siRNA knockdown abolishes LECT2-induced JNK phosphorylation and downstream inflammatory responses.","method":"siRNA knockdown of CD209, Western blot for JNK phosphorylation, qPCR for inflammatory mediators, JNK inhibitor studies","journal":"Metabolism: clinical and experimental","confidence":"Medium","confidence_rationale":"Tier 2 — siRNA knockdown with pathway inhibition establishing CD209 as LECT2 receptor mediating JNK signaling, single lab","pmids":["26123523"],"is_preprint":false},{"year":2008,"finding":"DC-SIGN acts as a receptor for avian H5N1 influenza virus; DC-SIGN-expressing cells (B-THP-1/DC-SIGN and T-THP-1/DC-SIGN) capture and transfer H5N1 pseudotyped and reverse-genetics virus particles to target cells (cis and trans infection); anti-DC-SIGN monoclonal antibodies block this transfer.","method":"Capture and transfer assays, DC-SIGN-expressing cell lines, antibody blocking, electron microscopy","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — defined cell lines expressing DC-SIGN with antibody blocking and functional transfer assays","pmids":["18593570"],"is_preprint":false},{"year":2010,"finding":"DC-SIGN-mediated uptake of M. tuberculosis-induced apoptotic neutrophils activates dendritic cells; inhibitory studies showed that DC contact-dependent DC activation requires binding of PMN Mac-1 (CD11b/CD18) to DC-SIGN, with endocytic activity involving αvβ5 but not scavenger receptor CD36.","method":"Antibody blocking assays for DC-SIGN, Mac-1, αvβ5, CD36; DC maturation readouts after apoptotic PMN-DC contact","journal":"Human immunology","confidence":"Medium","confidence_rationale":"Tier 2 — receptor-specific antibody blocking with defined counter-receptor (Mac-1) and functional DC maturation readout","pmids":["20219612"],"is_preprint":false},{"year":2010,"finding":"IL-4 increases CD209 expression on human Schwann cells, leading to increased binding and uptake of M. leprae; CD209-positive Schwann cells show higher M. leprae binding than CD209-negative Schwann cells; Th1 cytokines do not induce CD209 on Schwann cells.","method":"CD209 expression analysis in primary Schwann cells and cell lines, M. leprae binding assays, cytokine treatment (IL-4 vs. Th1 cytokines)","journal":"Infection and immunity","confidence":"Medium","confidence_rationale":"Tier 2 — IL-4-mediated CD209 induction linked to M. leprae binding with functional comparisons across CD209+/- cells","pmids":["20713631"],"is_preprint":false},{"year":2021,"finding":"CD209/DC-SIGN interacts with the SARS-CoV-2 spike receptor-binding domain (S-RBD) and can mediate SARS-CoV-2 entry into human cells; CD209 knockdown inhibits virus entry; CD209 functions as an alternative SARS-CoV-2 receptor relevant in tissues with low ACE2 expression.","method":"Biochemical binding assays with purified recombinant S-RBD, siRNA knockdown, SARS-CoV-2 infection assays in endothelial cells","journal":"ACS central science","confidence":"High","confidence_rationale":"Tier 2 — multiple biochemical assays plus siRNA knockdown and direct virus infection with functional entry readout","pmids":["34341769"],"is_preprint":false},{"year":2019,"finding":"DC-SIGN physically interacts with Lyn kinase; DC-SIGN activation recruits Lyn and p85 to form a DC-SIGN-Lyn-p85 complex that promotes PI3K/Akt/β-catenin signaling in colorectal cancer cells, increasing transcription of MMP-9 and VEGF and promoting TCF1/LEF1-mediated suppression of miR-185.","method":"Co-immunoprecipitation, Western blot, knockdown/overexpression experiments, in vitro and in vivo metastasis assays","journal":"Cell death and differentiation","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP identifying complex plus functional pathway assays, but mechanistic data primarily from cancer cell context","pmids":["31217502"],"is_preprint":false},{"year":2017,"finding":"DC-SIGN functions as more than just an attachment factor for dengue virus; using internalization-deficient DC-SIGN mutants (alanine substitutions in 3 cytoplasmic internalization motifs, or cytoplasmic truncation), DC-SIGN co-localizes with DENV inside cells and all 3 DC-SIGN molecules still support cell infection, implying involvement of a co-receptor for internalization-deficient forms.","method":"Internalization-deficient DC-SIGN mutants, confocal and super-resolution imaging, single-particle tracking, infectivity assays","journal":"Traffic (Copenhagen, Denmark)","confidence":"Medium","confidence_rationale":"Tier 2 — systematic mutant analysis with high-resolution imaging and infection readout","pmids":["28128492"],"is_preprint":false},{"year":2018,"finding":"TLR4 triggering simultaneously with DC-SIGN causes translocation of DC-SIGN cargo to the cytosol in human DCs, leading to proteasome-dependent processing and increased CD8+ T cell activation (cross-presentation), revealing a TLR4-DC-SIGN cooperation pathway for cytosolic antigen routing.","method":"Imaging flow cytometry, antigen-specific CD8+ T cell activation assays, proteasome inhibitors, TLR4 ligand co-stimulation","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 — imaging flow cytometry combined with functional T cell assay and proteasome inhibition, single lab","pmids":["29963041"],"is_preprint":false},{"year":2011,"finding":"The DC-SIGN neck domain, but not the CRD, confers higher binding affinity to HIV gp120 via formation of tetramers; chimera and truncate analysis of DC-SIGN and DCIR demonstrates DC-SIGN's superior HIV-1 capture and transfer capability is neck-domain dependent.","method":"Soluble DC-SIGN/DCIR truncation and chimeric constructs, HIV capture and transfer assays","journal":"Virology","confidence":"Medium","confidence_rationale":"Tier 2 — systematic truncation and chimera analysis with functional gp120 binding and HIV transfer assays","pmids":["24928041"],"is_preprint":false},{"year":2010,"finding":"During DC-SIGN expression upregulation at the CD209 locus upon monocyte-to-DC differentiation, two CpG dinucleotides (CpG2 and CpG3) in the CD209 promoter show marked demethylation, and 'active' histone modifications are acquired while 'repressive' marks are lost, establishing an epigenetic mechanism for CD209 gene activation.","method":"Bisulfite sequencing, ChIP for histone modifications, gene expression analysis during differentiation","journal":"Epigenetics","confidence":"Medium","confidence_rationale":"Tier 2 — bisulfite sequencing and ChIP with functional differentiation model, single lab","pmids":["20818162"],"is_preprint":false}],"current_model":"CD209/DC-SIGN is a C-type lectin receptor on dendritic cells that forms pH-sensitive tetramers via its neck domain, binds mannose- and fucose-containing glycans on pathogens (HIV gp120, ManLAM, high-mannose N-glycans) and self-ligands (ICAM-2, ICAM-3, Lewis x glycans) through its carbohydrate recognition domain, mediates DC trafficking via ICAM-2 interaction under shear flow, internalizes bound cargo via its cytoplasmic tail into non-lysosomal endosomal compartments (or late endosomes depending on context), and initiates intracellular signaling through Raf-1-dependent p65 phosphorylation and LARG-mediated Rho-GTPase activation that modulates TLR signaling and NF-κB-dependent transcription to tailor immune responses to diverse pathogens."},"narrative":{"teleology":[{"year":2000,"claim":"DC-SIGN was established as an adhesion receptor mediating dendritic cell trafficking, resolving the question of how DCs interact with endothelium under physiological shear flow.","evidence":"Shear flow adhesion and transmigration assays across endothelial monolayers using ICAM-2 as vascular ligand","pmids":["11017109"],"confidence":"High","gaps":["Signaling downstream of ICAM-2 engagement not characterized","In vivo relevance in human DC migration not demonstrated"]},{"year":2002,"claim":"The cytoplasmic tail was shown to be required for DC-SIGN-mediated HIV internalization into a non-lysosomal compartment and for trans-infection of T cells, establishing the endocytic function as central to DC-SIGN's role in HIV pathogenesis.","evidence":"Cytoplasmic tail deletion mutants combined with HIV internalization and trans-infection assays; Nef-mediated inhibition of DC-SIGN endocytosis enhancing viral transmission","pmids":["11825572","11825573"],"confidence":"High","gaps":["Identity of the non-lysosomal compartment not defined at molecular level","Cytoplasmic tail binding partners mediating endocytosis not identified"]},{"year":2003,"claim":"DC-SIGN was identified as the dominant receptor for M. tuberculosis entry into DCs via ManLAM binding, and ManLAM engagement was shown to suppress TLR-mediated DC maturation, revealing pathogen subversion of innate immunity through DC-SIGN.","evidence":"Antibody blocking with ManLAM binding studies and DC maturation assays across mycobacterial species","pmids":["12515809","12515819"],"confidence":"High","gaps":["Signaling pathway from DC-SIGN to TLR suppression not molecularly defined","Later knockout studies showed ManLAM/PIM6 are not the sole mycobacterial DC-SIGN ligands (PMID:19651855)"]},{"year":2006,"claim":"Comprehensive glycan array screening defined DC-SIGN's dual specificity for mannose and fucose glycans, mapped its ligand repertoire to oligomannose N-glycans and Lewis x trisaccharides, and extended its pathogen recognition to E. coli LPS core and measles virus glycoproteins.","evidence":"Glycan array with >100 structures and quantitative binding; LPS core mutant panel for E. coli phagocytosis; MV attachment versus entry dissection in transfected cells","pmids":["17055489","16951363","16537615"],"confidence":"High","gaps":["How dual mannose/fucose specificity is structurally accommodated in a single CRD binding site not fully resolved","Relative contribution of each glycan type to in vivo pathogen capture unknown"]},{"year":2007,"claim":"DC-SIGN was found to organize into nanoclusters on the DC surface and to signal through the Rho-GEF LARG upon HIV engagement, establishing that DC-SIGN is not merely an adhesion/capture receptor but actively transduces intracellular signals that promote viral synapse formation.","evidence":"Near-field scanning optical microscopy for nanocluster visualization; phosphoproteomics and gene expression profiling identifying LARG-Rho pathway and ATF3 upregulation","pmids":["17577901","17496896"],"confidence":"High","gaps":["How cytoplasmic tail connects to LARG activation molecularly unclear","Whether LARG pathway is engaged by non-viral DC-SIGN ligands not tested"]},{"year":2008,"claim":"A Raf-1–NF-κB p65 Ser276 phosphorylation–pTEF-b axis was identified downstream of DC-SIGN/gp120 engagement, revealing how DC-SIGN signaling co-opts transcription elongation machinery to support HIV-1 replication in DCs.","evidence":"Signaling pathway dissection with kinase inhibitors, phosphorylation site mapping, and transcription elongation assays","pmids":["20364151"],"confidence":"High","gaps":["Relationship between Raf-1 and LARG signaling arms not clarified","Whether Raf-1 pathway modulates immune gene transcription beyond viral genes not fully explored"]},{"year":2009,"claim":"Biophysical studies resolved DC-SIGN's quaternary structure as a pH-sensitive tetramer mediated by the neck domain, with an extended conformation on membranes that undergoes conformational change upon glycan binding, explaining avidity-based pathogen capture and pH-triggered ligand release in endosomes.","evidence":"SAXS-based molecular envelope and pH-dependent oligomerization; surface force measurements between lipid bilayers with neoglycolipid ligands","pmids":["19502234","19553201"],"confidence":"High","gaps":["Full atomic-resolution structure of the intact tetramer not determined","How conformational change is transmitted to cytoplasmic signaling unknown"]},{"year":2010,"claim":"Live-cell imaging revealed directed lateral mobility of DC-SIGN clusters from the leading edge to medial lamellar endocytic sites, and DC-SIGN was shown to recognize apoptotic neutrophil Mac-1 and to be epigenetically regulated during DC differentiation, broadening its functional context beyond pathogen capture.","evidence":"Single-particle tracking and FRAP on immature DCs; antibody blocking of Mac-1–DC-SIGN interaction with DC maturation readout; bisulfite sequencing and histone ChIP during monocyte-to-DC differentiation","pmids":["18270264","20219612","20818162"],"confidence":"Medium","gaps":["Motor or cytoskeletal mechanism driving directed DC-SIGN mobility not identified","Functional consequence of epigenetic regulation on pathogen handling not tested"]},{"year":2011,"claim":"DC-SIGN ligation was shown to activate sphingomyelinases generating ceramide that reorganizes receptor nanoclusters and recruits CD150 to enhance measles virus uptake, and the neck domain was confirmed as the determinant of superior HIV-1 capture through tetramerization.","evidence":"SMase activity assays with ceramide detection and CD150 co-clustering analysis; DC-SIGN/DCIR chimera and truncation constructs with HIV capture assays","pmids":["21379338","24928041"],"confidence":"High","gaps":["Whether ceramide-mediated reorganization applies to all DC-SIGN ligands or is measles-specific","Direct structural basis of neck-domain tetramerization at atomic level lacking"]},{"year":2014,"claim":"Atomic-resolution structural studies by NMR and X-ray crystallography detailed the CRD binding mode for Lewis x and glycomimetic antagonists, revealing that a monovalent pseudomannotrioside can cluster DC-SIGN tetramers, providing a basis for therapeutic antagonist design.","evidence":"NMR (HSQC, STD, trNOE) of CRD–Lewis x; X-ray co-crystal structures with glycomimetics; ITC, AUC, and DLS demonstrating tetramer clustering","pmids":["25121780","24749535"],"confidence":"High","gaps":["In vivo efficacy of glycomimetic antagonists not tested","Whether tetramer clustering by monovalent ligand occurs on intact cell membranes unknown"]},{"year":2018,"claim":"TLR4 co-stimulation was found to redirect DC-SIGN cargo to the cytosol for proteasome-dependent cross-presentation to CD8+ T cells, revealing cooperative innate receptor crosstalk that shapes adaptive immunity.","evidence":"Imaging flow cytometry with proteasome inhibitors and antigen-specific CD8+ T cell activation assays in human DCs","pmids":["29963041"],"confidence":"Medium","gaps":["Molecular mechanism of cargo translocation from endosome to cytosol not identified","Whether this pathway operates for all DC-SIGN-captured antigens or only specific ligands unclear"]},{"year":2019,"claim":"Antigen particle size was demonstrated to determine DC-SIGN intracellular routing fate—soluble antigens to early endosomes versus particulate antigens to surface-accessible invaginated pockets—and a DC-SIGN–Lyn–PI3K signaling axis was identified in cancer cells, extending DC-SIGN function beyond immune contexts.","evidence":"Glycopolymers of defined size with endosomal marker colocalization; co-immunoprecipitation of DC-SIGN–Lyn–p85 complex with functional metastasis assays","pmids":["31270240","31217502"],"confidence":"Medium","gaps":["Mechanism determining size-dependent sorting at the molecular level unknown","Lyn–PI3K pathway identified only in colorectal cancer cells, not confirmed in primary DCs"]},{"year":2021,"claim":"CD209 was identified as an alternative entry receptor for SARS-CoV-2 via spike RBD binding, relevant in tissues with low ACE2 expression, expanding the pandemic significance of DC-SIGN.","evidence":"Purified S-RBD binding assays, siRNA knockdown of CD209, and SARS-CoV-2 infection of endothelial cells","pmids":["34341769"],"confidence":"High","gaps":["Glycan dependence of spike–DC-SIGN interaction not fully characterized","Relative contribution of DC-SIGN versus ACE2 in vivo across tissues not quantified"]},{"year":null,"claim":"Key unresolved questions include the full atomic structure of the intact DC-SIGN tetramer with neck domain, the molecular mechanism coupling CRD ligand engagement to cytoplasmic signaling through LARG, Raf-1, and sphingomyelinase pathways, the identity of additional mycobacterial DC-SIGN ligands beyond ManLAM/PIM6, and the in vivo hierarchy of DC-SIGN among alternative pathogen receptors.","evidence":"","pmids":[],"confidence":"Low","gaps":["Full-length tetramer atomic structure unavailable","Cytoplasmic tail–signaling adaptor interactions not structurally resolved","In vivo mouse models limited by absence of true DC-SIGN ortholog"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,3,6,7,29]},{"term_id":"GO:0038024","term_label":"cargo receptor activity","supporting_discovery_ids":[1,11,13]},{"term_id":"GO:0098631","term_label":"cell adhesion mediator activity","supporting_discovery_ids":[0,27]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[17,18]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[1,11,22]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[22]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,6,7,10,32]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[6,7,25,30]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[1,11,22]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,2,29]}],"complexes":["DC-SIGN tetramer"],"partners":["ICAM2","ARHGEF12","RAF1","LYN","PIK3R1","SMPD2","SMPD1"],"other_free_text":[]},"mechanistic_narrative":"CD209/DC-SIGN is a C-type lectin receptor on dendritic cells that functions as a pattern-recognition receptor for mannose- and fucose-containing glycans on diverse pathogens and as an adhesion receptor mediating dendritic cell trafficking. Its carbohydrate recognition domain binds high-mannose N-glycans and Lewis x-type structures on pathogens including HIV-1 gp120, mycobacterial ManLAM, SARS-CoV-2 spike protein, and various viral glycoproteins, while its neck domain drives pH-sensitive tetramerization that enhances ligand avidity and enables pH-dependent ligand release after internalization into endosomal compartments [PMID:19502234, PMID:17055489, PMID:34341769]. The cytoplasmic tail is required for receptor-mediated endocytosis and routing of captured cargo to distinct intracellular compartments—early endosomes for soluble antigens versus surface-accessible invaginated pockets for particulate antigens—with antigen size governing trafficking fate and functional outcomes including trans-infection of T cells by HIV-1 [PMID:11825572, PMID:31270240]. DC-SIGN ligation activates intracellular signaling through LARG-mediated Rho-GTPase activation for viral synapse formation, Raf-1-dependent phosphorylation of NF-κB p65 at Ser276 to promote transcription elongation, and sphingomyelinase-driven ceramide generation that reorganizes receptor nanoclusters, collectively modulating TLR-dependent immune responses and pathogen exploitation of dendritic cells [PMID:17496896, PMID:20364151, PMID:21379338, PMID:12515809]."},"prefetch_data":{"uniprot":{"accession":"Q9NNX6","full_name":"CD209 antigen","aliases":["C-type lectin domain family 4 member L","Dendritic cell-specific ICAM-3-grabbing non-integrin 1","DC-SIGN","DC-SIGN1"],"length_aa":404,"mass_kda":45.8,"function":"Pathogen-recognition receptor expressed on the surface of immature dendritic cells (DCs) and involved in initiation of primary immune response. Thought to mediate the endocytosis of pathogens which are subsequently degraded in lysosomal compartments. The receptor returns to the cell membrane surface and the pathogen-derived antigens are presented to resting T-cells via MHC class II proteins to initiate the adaptive immune response On dendritic cells (DCs) it is a high affinity receptor for ICAM2 and ICAM3 by binding to mannose-like carbohydrates (PubMed:10721994, PubMed:10721995, PubMed:11017109, PubMed:12574325). May act as a DC rolling receptor that mediates transendothelial migration of DC presursors from blood to tissues by binding endothelial ICAM2 (PubMed:11017109). Forms a first contact between DC and resting T cell, througth ICAM3 binding, facilitating the downstream DC-T cell clustering process and DC-induced proliferation of resting T Cells (PubMed:10721994, PubMed:10721995) (Microbial infection) Acts as an attachment receptor for HIV-1 and HIV-2 (Microbial infection) Acts as an attachment receptor for Ebolavirus (Microbial infection) Acts as an attachment receptor for Cytomegalovirus (Microbial infection) Acts as an attachment receptor for HCV (Microbial infection) Acts as an attachment receptor for Dengue virus (Microbial infection) Acts as an attachment receptor for Measles virus (Microbial infection) Acts as an attachment receptor for Herpes simplex virus 1 (Microbial infection) Acts as an attachment receptor for Influenzavirus A (Microbial infection) Acts as an attachment receptor for SARS-CoV (Microbial infection) Acts as an attachment receptor for Japanese encephalitis virus (Microbial infection) Acts as an attachment receptor for Lassa virus (PubMed:23966408). Acts as an attachment receptor for Marburg virusn (Microbial infection) Acts as an attachment receptor for Respiratory syncytial virus (Microbial infection) Acts as an attachment receptor for Rift valley fever virus and uukuniemi virus (Microbial infection) Acts as an attachment receptor for West-nile virus (Microbial infection) Probably recognizes in a calcium-dependent manner high mannose N-linked oligosaccharides in a variety of bacterial pathogen antigens, including Leishmania pifanoi LPG, Lewis-x antigen in Helicobacter pylori LPS, mannose in Klebsiella pneumonae LPS, di-mannose and tri-mannose in Mycobacterium tuberculosis ManLAM and Lewis-x antigen in Schistosoma mansoni SEA (PubMed:16379498). Recognition of M.tuberculosis by dendritic cells occurs partially via this molecule (PubMed:16092920, PubMed:21203928)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q9NNX6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CD209","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CD209","total_profiled":1310},"omim":[{"mim_id":"616256","title":"C-TYPE LECTIN DOMAIN FAMILY 4, MEMBER G; CLEC4G","url":"https://www.omim.org/entry/616256"},{"mim_id":"614371","title":"DENGUE VIRUS, SUSCEPTIBILITY TO","url":"https://www.omim.org/entry/614371"},{"mim_id":"609532","title":"HEPATITIS C VIRUS, SUSCEPTIBILITY TO","url":"https://www.omim.org/entry/609532"},{"mim_id":"609423","title":"HUMAN IMMUNODEFICIENCY VIRUS TYPE 1, SUSCEPTIBILITY TO","url":"https://www.omim.org/entry/609423"},{"mim_id":"608487","title":"TRIPARTITE MOTIF-CONTAINING PROTEIN 5; TRIM5","url":"https://www.omim.org/entry/608487"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"adipose tissue","ntpm":32.0},{"tissue":"placenta","ntpm":21.4}],"url":"https://www.proteinatlas.org/search/CD209"},"hgnc":{"alias_symbol":["DC-SIGN","hDC-SIGN","CDSIGN","DC-SIGN1","CLEC4L"],"prev_symbol":[]},"alphafold":{"accession":"Q9NNX6","domains":[{"cath_id":"1.20.1440,1.20.1480","chopping":"69-160","consensus_level":"high","plddt":64.5866,"start":69,"end":160},{"cath_id":"3.10.100.10","chopping":"261-381","consensus_level":"high","plddt":96.4601,"start":261,"end":381},{"cath_id":"1.20.1440","chopping":"164-253","consensus_level":"high","plddt":79.649,"start":164,"end":253}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NNX6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NNX6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NNX6-F1-predicted_aligned_error_v6.png","plddt_mean":71.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CD209","jax_strain_url":"https://www.jax.org/strain/search?query=CD209"},"sequence":{"accession":"Q9NNX6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NNX6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NNX6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NNX6"}},"corpus_meta":[{"pmid":"12515809","id":"PMC_12515809","title":"Mycobacteria 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immunology","url":"https://pubmed.ncbi.nlm.nih.gov/17496896","citation_count":156,"is_preprint":false},{"pmid":"23608151","id":"PMC_23608151","title":"The physiological role of DC-SIGN: a tale of mice and men.","date":"2013","source":"Trends in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/23608151","citation_count":147,"is_preprint":false},{"pmid":"12797442","id":"PMC_12797442","title":"DC-SIGN: a novel HIV receptor on DCs that mediates HIV-1 transmission.","date":"2003","source":"Current topics in microbiology and immunology","url":"https://pubmed.ncbi.nlm.nih.gov/12797442","citation_count":142,"is_preprint":false},{"pmid":"18998127","id":"PMC_18998127","title":"Innate signaling by the C-type lectin DC-SIGN dictates immune responses.","date":"2008","source":"Cancer immunology, immunotherapy : CII","url":"https://pubmed.ncbi.nlm.nih.gov/18998127","citation_count":124,"is_preprint":false},{"pmid":"15096474","id":"PMC_15096474","title":"Functional comparison of the mouse DC-SIGN, 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immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean functional assay with defined molecular interaction and cellular phenotype, replicated across multiple endothelial conditions\",\n      \"pmids\": [\"11017109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"DC-SIGN mediates rapid internalization of intact HIV into a low-pH, non-lysosomal compartment; internalized virus retains infectivity; removal of the DC-SIGN cytoplasmic tail reduced viral uptake and abrogated trans-enhancement of T cell infection, establishing the cytoplasmic tail as required for endocytosis-dependent trans-infection.\",\n      \"method\": \"Cytoplasmic tail deletion mutants, HIV internalization assay, trans-infection T cell assay\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mutagenesis of cytoplasmic tail combined with functional internalization and trans-infection assays\",\n      \"pmids\": [\"11825572\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"HIV-1 Nef protein causes upregulation of DC-SIGN surface levels on HIV-1-infected DCs by inhibiting DC-SIGN endocytosis, which dramatically increases DC-T lymphocyte clustering and HIV-1 transmission.\",\n      \"method\": \"HIV-1 infection of DCs, Nef expression constructs, flow cytometry for DC-SIGN surface levels, clustering and transmission assays\",\n      \"journal\": \"Immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods linking Nef to DC-SIGN endocytosis inhibition and functional transmission\",\n      \"pmids\": [\"11825573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"DC-SIGN captures and internalizes intact Mycobacterium bovis BCG through the mycobacterial cell wall component ManLAM; ManLAM binding to DC-SIGN prevents mycobacteria- or LPS-induced DC maturation by interfering with TLR-mediated signals; blocking antibodies against DC-SIGN reverse this immunosuppressive effect.\",\n      \"method\": \"Antibody blocking assays, DC maturation assays (cytokine production, surface marker upregulation), ManLAM binding studies\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal assays with specific antibody blocking and defined molecular ligand (ManLAM), replicated across labs\",\n      \"pmids\": [\"12515809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"DC-SIGN is the major receptor for M. tuberculosis entry into human monocyte-derived DCs; the mycobacteria-specific lipoglycan LAM was identified as a key DC-SIGN ligand; complement receptor 3 and mannose receptor play a minor role in mycobacterial binding to DCs.\",\n      \"method\": \"Antibody blocking, receptor-specific inhibition, comparative receptor analysis on DCs and macrophages\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — receptor comparison with antibody blocking and defined ligand identification, independently replicated\",\n      \"pmids\": [\"12515819\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"DC-SIGN specificity for mannose- and fucose-containing glycans was mapped using a large glycan array; DC-SIGN binds with Kd <2 µM to multivalent Lewis x (Galbeta1-4(Fucalpha1-3)GlcNAc) trisaccharides; selective binding observed to oligomannose-type N-glycans and LacdiNAc-fucose; no binding to core-fucose-linked N-glycans.\",\n      \"method\": \"Glycan array screening, binding affinity measurements\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — comprehensive glycan array with quantitative binding data across >100 glycan structures\",\n      \"pmids\": [\"17055489\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"DC-SIGN activation by HIV or DC-SIGN-specific antibody induces signaling via the Rho guanine nucleotide-exchange factor LARG, leading to increased Rho-GTPase activity; this LARG activation is required for formation of virus-T cell synapses, while DC-SIGN engagement downregulates MHC class II and interferon-response genes and upregulates ATF3.\",\n      \"method\": \"Large-scale gene expression profiling, phosphoproteomic analysis of tyrosine-phosphorylated proteome, functional virus-T cell synapse assay\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multi-omic analysis combined with functional viral synapse assay identifying specific GEF (LARG) as signaling intermediate\",\n      \"pmids\": [\"17496896\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"HIV-1 gp120 binding to DC-SIGN induces kinase Raf-1-dependent phosphorylation of NF-κB subunit p65 at Ser276, which recruits the transcription-elongation factor pTEF-b to nascent viral transcripts; pTEF-b-mediated phosphorylation of RNA polymerase II at Ser2 then enables transcription elongation and generation of full-length viral transcripts required for HIV-1 replication in DCs.\",\n      \"method\": \"Signaling pathway dissection, phosphorylation assays, inhibitor studies, transcription elongation assays\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — mechanistically dissected signaling cascade with specific phosphorylation sites, multiple inhibitors, and functional viral replication readout\",\n      \"pmids\": [\"20364151\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"DC-SIGN's neck domain controls pH-sensitive oligomerization: the extracellular domain exists in equilibrium between monomeric and tetrameric states dependent on pH and ionic strength; SAXS-based molecular envelope demonstrates the neck domain is central to oligomerization, extended conformation, and carbohydrate recognition domain organization, implicating pH-driven dissociation in ligand release after internalization.\",\n      \"method\": \"Solution X-ray scattering (SAXS), hydrodynamic measurements, pH-dependent oligomerization assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — SAXS structural analysis with functional pH dependence data, mechanistically linking neck domain to oligomerization and ligand release\",\n      \"pmids\": [\"19502234\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Surface force measurements show DC-SIGN is in an extended conformation on membranes; glycan binding is associated with a conformational change that repositions the carbohydrate-recognition domains; lateral mobility of membrane-bound ligands enhances engagement of multiple CRDs in the receptor oligomer with appropriately spaced ligands.\",\n      \"method\": \"Surface force measurements between apposed lipid bilayers, neoglycolipid binding studies\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — biophysical reconstitution with direct force measurements revealing conformational change upon ligand binding\",\n      \"pmids\": [\"19553201\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"DC-SIGN ligation on DCs by antibodies, mannan, or measles virus causes rapid activation of neutral and acid sphingomyelinases (SMase), leading to ceramide accumulation in the outer membrane leaflet; SMase activation promotes DC-SIGN signaling and recruits CD150 from intracellular LAMP-1+ compartments to the surface where it co-clusters with DC-SIGN, enhancing measles virus uptake.\",\n      \"method\": \"SMase activity assays, ceramide detection, co-clustering analysis, confocal microscopy of CD150 trafficking\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal biochemical and imaging methods linking DC-SIGN ligation to SMase activation and receptor co-clustering\",\n      \"pmids\": [\"21379338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"DC-SIGN acts as a receptor for phleboviruses (Rift Valley fever and Uukuniemi viruses) by binding viral glycoproteins via high-mannose N-glycans; DC-SIGN is required for both viral attachment and endocytosis; an endocytosis-defective DC-SIGN mutant cannot mediate virus uptake; internalized virus separates from DC-SIGN and traffics to late endosomes.\",\n      \"method\": \"DC-SIGN endocytosis-defective mutants, live-cell virus-receptor clustering visualization, viral infection assays\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — endocytosis-defective mutant analysis, live-cell imaging, and viral trafficking studies with defined glycan ligand\",\n      \"pmids\": [\"21767814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"DC-SIGN serves as a novel attachment receptor for both laboratory-adapted and wild-type measles virus strains via the MV glycoproteins F and H; DC-SIGN does not support MV entry (no susceptibility in DC-SIGN-transfected CHO cells) but is required for efficient MV infection of immature DCs in cis by enhancing CD46/CD150-mediated infection.\",\n      \"method\": \"DC-SIGN transfection in CHO cells, antibody blocking, attachment and infection assays\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — receptor-transfection experiments with defined ligands (MV-F and MV-H) and functional infection readout distinguishing attachment from entry\",\n      \"pmids\": [\"16537615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Human herpesvirus 8 (HHV-8) uses DC-SIGN as an entry receptor in B cells; DC-SIGN-mediated endocytosis is required for HHV-8 infection, as DC-SIGN lacking the transmembrane domain (unable to mediate endocytosis) cannot support infection; HHV-8 infection of B cells increases DC-SIGN expression and decreases CD20 and MHC class I.\",\n      \"method\": \"DC-SIGN truncation mutants, endocytic pathway inhibitors, HHV-8 infection assays (viral DNA, lytic/latency protein expression, infectious virus production)\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — transmembrane domain truncation mutant and endocytic inhibitors with multiple functional infection readouts\",\n      \"pmids\": [\"18337571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"DC-SIGN binds HHV-8 glycoprotein B (gB) in a dose-dependent manner via high-mannose carbohydrate structures on gB; key amino acids in the DC-SIGN carbohydrate recognition domain are required for HHV-8 infection.\",\n      \"method\": \"Biochemical binding assay (gB-DC-SIGN interaction), site-directed mutagenesis of DC-SIGN CRD, infection assays\",\n      \"journal\": \"Virus research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — direct binding assay with mutagenesis identifying CRD residues, single lab\",\n      \"pmids\": [\"25018023\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"DC-SIGN mediates binding and phagocytosis of E. coli through interactions with the complete core region of LPS (outer core); pathogenic E. coli strains expressing O-antigen, which masks core LPS, are not phagocytosed via DC-SIGN.\",\n      \"method\": \"LPS core mutants of E. coli, phagocytosis assays in DC-SIGN-expressing cells\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic LPS mutant panel across four Gram-negative species identifying N-acetylglucosamine in core LPS as DC-SIGN ligand\",\n      \"pmids\": [\"16951363\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Hexamannosylated PIM6 (containing terminal alpha(1→2)-linked mannosyl residues identical to ManLAM caps) is a high-affinity DC-SIGN ligand; however, a PIM6-deficient BCG mutant and a PIM6/ManLAM double knockout bound DC-SIGN similarly to wild-type, indicating other unknown mycobacterial ligands dominate the DC-SIGN interaction.\",\n      \"method\": \"Synthetic and natural PIM binding assays, M. bovis BCG knockout strains (ΔpimE, ΔpimE ΔcapA), DC binding assays, cytokine measurement\",\n      \"journal\": \"Infection and immunity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — defined synthetic ligands combined with genetic knockout strains and functional DC assays\",\n      \"pmids\": [\"19651855\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"DC-SIGN clusters on the plasma membrane of immature DCs are preferentially localized to the leading edge of the lamellipod and undergo directed lateral mobility at high velocity (~1420 nm/s) from the leading edge to medial lamellar sites where endocytosis occurs, suggesting a mechanism for pathogen capture followed by internalization.\",\n      \"method\": \"Live-cell fluorescence microscopy, single-particle tracking, FRAP, colocalization with endocytic markers\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct live-cell imaging with single-particle tracking and functional colocalization with endocytic activity\",\n      \"pmids\": [\"18270264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"DC-SIGN receptors are organized in nanosized domains (clusters) on the dendritic cell plasma membrane, with ~80% of receptors in nanoclusters; heterogeneous molecular packing density within clusters was revealed by near-field scanning optical microscopy with single-molecule resolution.\",\n      \"method\": \"Near-field scanning optical microscopy (NSOM), single-molecule detection, sequential photobleaching\",\n      \"journal\": \"Chemphyschem\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — high-resolution single-molecule imaging on intact DCs revealing nanoscale receptor organization\",\n      \"pmids\": [\"17577901\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"CD4 coexpression with DC-SIGN impairs HIV-1 transmission to T cells: CD4 promotes internalization and intracellular retention of HIV-1 into late endosomal compartments (CD63+/CD81+), and Nef-mediated CD4 downregulation on MDDCs correlates with enhanced viral transmission.\",\n      \"method\": \"DC-SIGN-CD4 co-expression in Raji cells, HIV-1 internalization assays, confocal microscopy, late endosome markers\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple cell systems with co-expression constructs and organelle marker colocalization\",\n      \"pmids\": [\"17151103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"NMR structural characterization of DC-SIGN CRD interaction with Lewis X (Le^X) trisaccharide reveals significant chemical shift perturbations identifying residues near the binding site; STD and trNOE NMR experiments defined binding epitopes and bound conformations of Le^X distinct from those in previous crystal structures.\",\n      \"method\": \"2D NMR (HSQC), STD-NMR, transferred NOE NMR, molecular modeling\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — NMR structural characterization with multiple complementary NMR experiments and molecular modeling\",\n      \"pmids\": [\"25121780\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Crystal structures of the DC-SIGN carbohydrate recognition domain complexed with glycomimetic antagonists (pseudomannobioside and pseudomannotrioside) reveal identical binding modes despite different inhibitory potencies; compound 2 (pseudomannotrioside) clusters DC-SIGN tetramers without multivalent scaffold, as determined by ITC, analytical ultracentrifugation, and DLS.\",\n      \"method\": \"X-ray crystallography, isothermal titration calorimetry (ITC), analytical ultracentrifugation, dynamic light scattering, SPR competition\",\n      \"journal\": \"ACS chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure combined with multiple biophysical methods demonstrating tetramer clustering by monovalent ligand\",\n      \"pmids\": [\"24749535\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Antigen particle size determines DC-SIGN-mediated intracellular routing: soluble glycopolymers are directed to transferrin-labeled early endosomes, while particulate antigens (aggregated polymers) are diverted to surface-accessible invaginated pockets that also harbor HIV-1, indicating antigen structure controls DC-SIGN trafficking fate.\",\n      \"method\": \"Ring-opening metathesis polymerization of glycopolymers, confocal microscopy, colocalization with endosomal markers\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic variation of antigen structure with colocalization to defined endosomal compartments across multiple conditions\",\n      \"pmids\": [\"31270240\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Semen clusterin, but not serum clusterin, binds DC-SIGN with high affinity (Kd 76 nM) through fucose-containing blood-type antigens (Le^x and Le^y) expressed on its glycans, and can abrogate HIV-1 binding to DC-SIGN.\",\n      \"method\": \"Affinity binding assays, blocking of HIV-1 capture, glycan structural analysis (Le^x/Le^y identification)\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — defined glycan ligands on clusterin with quantitative binding affinity and functional HIV blocking, single lab\",\n      \"pmids\": [\"22013110\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"MUC1 is identified as the major milk glycoprotein that binds to the lectin domain of DC-SIGN in human milk, via Lewis x-type oligosaccharides, and prevents pathogen interaction with DC-SIGN; this effect is specific to human milk and not present in formula, bovine, or camel milk.\",\n      \"method\": \"Affinity binding assays, glycan inhibition, comparative milk analysis\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — pulldown/binding assay identifying MUC1 as DC-SIGN ligand with functional blocking assay, single lab\",\n      \"pmids\": [\"25821450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"LECT2 (leukocyte cell-derived chemotaxin 2) signals through CD209/DC-SIGN receptor to phosphorylate JNK in human endothelial cells and macrophages, inducing ICAM-1, TNFα, MCP-1, and IL-1β expression; CD209 siRNA knockdown abolishes LECT2-induced JNK phosphorylation and downstream inflammatory responses.\",\n      \"method\": \"siRNA knockdown of CD209, Western blot for JNK phosphorylation, qPCR for inflammatory mediators, JNK inhibitor studies\",\n      \"journal\": \"Metabolism: clinical and experimental\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — siRNA knockdown with pathway inhibition establishing CD209 as LECT2 receptor mediating JNK signaling, single lab\",\n      \"pmids\": [\"26123523\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"DC-SIGN acts as a receptor for avian H5N1 influenza virus; DC-SIGN-expressing cells (B-THP-1/DC-SIGN and T-THP-1/DC-SIGN) capture and transfer H5N1 pseudotyped and reverse-genetics virus particles to target cells (cis and trans infection); anti-DC-SIGN monoclonal antibodies block this transfer.\",\n      \"method\": \"Capture and transfer assays, DC-SIGN-expressing cell lines, antibody blocking, electron microscopy\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — defined cell lines expressing DC-SIGN with antibody blocking and functional transfer assays\",\n      \"pmids\": [\"18593570\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"DC-SIGN-mediated uptake of M. tuberculosis-induced apoptotic neutrophils activates dendritic cells; inhibitory studies showed that DC contact-dependent DC activation requires binding of PMN Mac-1 (CD11b/CD18) to DC-SIGN, with endocytic activity involving αvβ5 but not scavenger receptor CD36.\",\n      \"method\": \"Antibody blocking assays for DC-SIGN, Mac-1, αvβ5, CD36; DC maturation readouts after apoptotic PMN-DC contact\",\n      \"journal\": \"Human immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — receptor-specific antibody blocking with defined counter-receptor (Mac-1) and functional DC maturation readout\",\n      \"pmids\": [\"20219612\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"IL-4 increases CD209 expression on human Schwann cells, leading to increased binding and uptake of M. leprae; CD209-positive Schwann cells show higher M. leprae binding than CD209-negative Schwann cells; Th1 cytokines do not induce CD209 on Schwann cells.\",\n      \"method\": \"CD209 expression analysis in primary Schwann cells and cell lines, M. leprae binding assays, cytokine treatment (IL-4 vs. Th1 cytokines)\",\n      \"journal\": \"Infection and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — IL-4-mediated CD209 induction linked to M. leprae binding with functional comparisons across CD209+/- cells\",\n      \"pmids\": [\"20713631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CD209/DC-SIGN interacts with the SARS-CoV-2 spike receptor-binding domain (S-RBD) and can mediate SARS-CoV-2 entry into human cells; CD209 knockdown inhibits virus entry; CD209 functions as an alternative SARS-CoV-2 receptor relevant in tissues with low ACE2 expression.\",\n      \"method\": \"Biochemical binding assays with purified recombinant S-RBD, siRNA knockdown, SARS-CoV-2 infection assays in endothelial cells\",\n      \"journal\": \"ACS central science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple biochemical assays plus siRNA knockdown and direct virus infection with functional entry readout\",\n      \"pmids\": [\"34341769\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"DC-SIGN physically interacts with Lyn kinase; DC-SIGN activation recruits Lyn and p85 to form a DC-SIGN-Lyn-p85 complex that promotes PI3K/Akt/β-catenin signaling in colorectal cancer cells, increasing transcription of MMP-9 and VEGF and promoting TCF1/LEF1-mediated suppression of miR-185.\",\n      \"method\": \"Co-immunoprecipitation, Western blot, knockdown/overexpression experiments, in vitro and in vivo metastasis assays\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP identifying complex plus functional pathway assays, but mechanistic data primarily from cancer cell context\",\n      \"pmids\": [\"31217502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"DC-SIGN functions as more than just an attachment factor for dengue virus; using internalization-deficient DC-SIGN mutants (alanine substitutions in 3 cytoplasmic internalization motifs, or cytoplasmic truncation), DC-SIGN co-localizes with DENV inside cells and all 3 DC-SIGN molecules still support cell infection, implying involvement of a co-receptor for internalization-deficient forms.\",\n      \"method\": \"Internalization-deficient DC-SIGN mutants, confocal and super-resolution imaging, single-particle tracking, infectivity assays\",\n      \"journal\": \"Traffic (Copenhagen, Denmark)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic mutant analysis with high-resolution imaging and infection readout\",\n      \"pmids\": [\"28128492\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TLR4 triggering simultaneously with DC-SIGN causes translocation of DC-SIGN cargo to the cytosol in human DCs, leading to proteasome-dependent processing and increased CD8+ T cell activation (cross-presentation), revealing a TLR4-DC-SIGN cooperation pathway for cytosolic antigen routing.\",\n      \"method\": \"Imaging flow cytometry, antigen-specific CD8+ T cell activation assays, proteasome inhibitors, TLR4 ligand co-stimulation\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — imaging flow cytometry combined with functional T cell assay and proteasome inhibition, single lab\",\n      \"pmids\": [\"29963041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The DC-SIGN neck domain, but not the CRD, confers higher binding affinity to HIV gp120 via formation of tetramers; chimera and truncate analysis of DC-SIGN and DCIR demonstrates DC-SIGN's superior HIV-1 capture and transfer capability is neck-domain dependent.\",\n      \"method\": \"Soluble DC-SIGN/DCIR truncation and chimeric constructs, HIV capture and transfer assays\",\n      \"journal\": \"Virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic truncation and chimera analysis with functional gp120 binding and HIV transfer assays\",\n      \"pmids\": [\"24928041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"During DC-SIGN expression upregulation at the CD209 locus upon monocyte-to-DC differentiation, two CpG dinucleotides (CpG2 and CpG3) in the CD209 promoter show marked demethylation, and 'active' histone modifications are acquired while 'repressive' marks are lost, establishing an epigenetic mechanism for CD209 gene activation.\",\n      \"method\": \"Bisulfite sequencing, ChIP for histone modifications, gene expression analysis during differentiation\",\n      \"journal\": \"Epigenetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — bisulfite sequencing and ChIP with functional differentiation model, single lab\",\n      \"pmids\": [\"20818162\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CD209/DC-SIGN is a C-type lectin receptor on dendritic cells that forms pH-sensitive tetramers via its neck domain, binds mannose- and fucose-containing glycans on pathogens (HIV gp120, ManLAM, high-mannose N-glycans) and self-ligands (ICAM-2, ICAM-3, Lewis x glycans) through its carbohydrate recognition domain, mediates DC trafficking via ICAM-2 interaction under shear flow, internalizes bound cargo via its cytoplasmic tail into non-lysosomal endosomal compartments (or late endosomes depending on context), and initiates intracellular signaling through Raf-1-dependent p65 phosphorylation and LARG-mediated Rho-GTPase activation that modulates TLR signaling and NF-κB-dependent transcription to tailor immune responses to diverse pathogens.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CD209/DC-SIGN is a C-type lectin receptor on dendritic cells that functions as a pattern-recognition receptor for mannose- and fucose-containing glycans on diverse pathogens and as an adhesion receptor mediating dendritic cell trafficking. Its carbohydrate recognition domain binds high-mannose N-glycans and Lewis x-type structures on pathogens including HIV-1 gp120, mycobacterial ManLAM, SARS-CoV-2 spike protein, and various viral glycoproteins, while its neck domain drives pH-sensitive tetramerization that enhances ligand avidity and enables pH-dependent ligand release after internalization into endosomal compartments [PMID:19502234, PMID:17055489, PMID:34341769]. The cytoplasmic tail is required for receptor-mediated endocytosis and routing of captured cargo to distinct intracellular compartments—early endosomes for soluble antigens versus surface-accessible invaginated pockets for particulate antigens—with antigen size governing trafficking fate and functional outcomes including trans-infection of T cells by HIV-1 [PMID:11825572, PMID:31270240]. DC-SIGN ligation activates intracellular signaling through LARG-mediated Rho-GTPase activation for viral synapse formation, Raf-1-dependent phosphorylation of NF-κB p65 at Ser276 to promote transcription elongation, and sphingomyelinase-driven ceramide generation that reorganizes receptor nanoclusters, collectively modulating TLR-dependent immune responses and pathogen exploitation of dendritic cells [PMID:17496896, PMID:20364151, PMID:21379338, PMID:12515809].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"DC-SIGN was established as an adhesion receptor mediating dendritic cell trafficking, resolving the question of how DCs interact with endothelium under physiological shear flow.\",\n      \"evidence\": \"Shear flow adhesion and transmigration assays across endothelial monolayers using ICAM-2 as vascular ligand\",\n      \"pmids\": [\"11017109\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling downstream of ICAM-2 engagement not characterized\", \"In vivo relevance in human DC migration not demonstrated\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"The cytoplasmic tail was shown to be required for DC-SIGN-mediated HIV internalization into a non-lysosomal compartment and for trans-infection of T cells, establishing the endocytic function as central to DC-SIGN's role in HIV pathogenesis.\",\n      \"evidence\": \"Cytoplasmic tail deletion mutants combined with HIV internalization and trans-infection assays; Nef-mediated inhibition of DC-SIGN endocytosis enhancing viral transmission\",\n      \"pmids\": [\"11825572\", \"11825573\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the non-lysosomal compartment not defined at molecular level\", \"Cytoplasmic tail binding partners mediating endocytosis not identified\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"DC-SIGN was identified as the dominant receptor for M. tuberculosis entry into DCs via ManLAM binding, and ManLAM engagement was shown to suppress TLR-mediated DC maturation, revealing pathogen subversion of innate immunity through DC-SIGN.\",\n      \"evidence\": \"Antibody blocking with ManLAM binding studies and DC maturation assays across mycobacterial species\",\n      \"pmids\": [\"12515809\", \"12515819\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling pathway from DC-SIGN to TLR suppression not molecularly defined\", \"Later knockout studies showed ManLAM/PIM6 are not the sole mycobacterial DC-SIGN ligands (PMID:19651855)\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Comprehensive glycan array screening defined DC-SIGN's dual specificity for mannose and fucose glycans, mapped its ligand repertoire to oligomannose N-glycans and Lewis x trisaccharides, and extended its pathogen recognition to E. coli LPS core and measles virus glycoproteins.\",\n      \"evidence\": \"Glycan array with >100 structures and quantitative binding; LPS core mutant panel for E. coli phagocytosis; MV attachment versus entry dissection in transfected cells\",\n      \"pmids\": [\"17055489\", \"16951363\", \"16537615\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How dual mannose/fucose specificity is structurally accommodated in a single CRD binding site not fully resolved\", \"Relative contribution of each glycan type to in vivo pathogen capture unknown\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"DC-SIGN was found to organize into nanoclusters on the DC surface and to signal through the Rho-GEF LARG upon HIV engagement, establishing that DC-SIGN is not merely an adhesion/capture receptor but actively transduces intracellular signals that promote viral synapse formation.\",\n      \"evidence\": \"Near-field scanning optical microscopy for nanocluster visualization; phosphoproteomics and gene expression profiling identifying LARG-Rho pathway and ATF3 upregulation\",\n      \"pmids\": [\"17577901\", \"17496896\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How cytoplasmic tail connects to LARG activation molecularly unclear\", \"Whether LARG pathway is engaged by non-viral DC-SIGN ligands not tested\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"A Raf-1–NF-κB p65 Ser276 phosphorylation–pTEF-b axis was identified downstream of DC-SIGN/gp120 engagement, revealing how DC-SIGN signaling co-opts transcription elongation machinery to support HIV-1 replication in DCs.\",\n      \"evidence\": \"Signaling pathway dissection with kinase inhibitors, phosphorylation site mapping, and transcription elongation assays\",\n      \"pmids\": [\"20364151\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relationship between Raf-1 and LARG signaling arms not clarified\", \"Whether Raf-1 pathway modulates immune gene transcription beyond viral genes not fully explored\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Biophysical studies resolved DC-SIGN's quaternary structure as a pH-sensitive tetramer mediated by the neck domain, with an extended conformation on membranes that undergoes conformational change upon glycan binding, explaining avidity-based pathogen capture and pH-triggered ligand release in endosomes.\",\n      \"evidence\": \"SAXS-based molecular envelope and pH-dependent oligomerization; surface force measurements between lipid bilayers with neoglycolipid ligands\",\n      \"pmids\": [\"19502234\", \"19553201\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full atomic-resolution structure of the intact tetramer not determined\", \"How conformational change is transmitted to cytoplasmic signaling unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Live-cell imaging revealed directed lateral mobility of DC-SIGN clusters from the leading edge to medial lamellar endocytic sites, and DC-SIGN was shown to recognize apoptotic neutrophil Mac-1 and to be epigenetically regulated during DC differentiation, broadening its functional context beyond pathogen capture.\",\n      \"evidence\": \"Single-particle tracking and FRAP on immature DCs; antibody blocking of Mac-1–DC-SIGN interaction with DC maturation readout; bisulfite sequencing and histone ChIP during monocyte-to-DC differentiation\",\n      \"pmids\": [\"18270264\", \"20219612\", \"20818162\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Motor or cytoskeletal mechanism driving directed DC-SIGN mobility not identified\", \"Functional consequence of epigenetic regulation on pathogen handling not tested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"DC-SIGN ligation was shown to activate sphingomyelinases generating ceramide that reorganizes receptor nanoclusters and recruits CD150 to enhance measles virus uptake, and the neck domain was confirmed as the determinant of superior HIV-1 capture through tetramerization.\",\n      \"evidence\": \"SMase activity assays with ceramide detection and CD150 co-clustering analysis; DC-SIGN/DCIR chimera and truncation constructs with HIV capture assays\",\n      \"pmids\": [\"21379338\", \"24928041\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ceramide-mediated reorganization applies to all DC-SIGN ligands or is measles-specific\", \"Direct structural basis of neck-domain tetramerization at atomic level lacking\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Atomic-resolution structural studies by NMR and X-ray crystallography detailed the CRD binding mode for Lewis x and glycomimetic antagonists, revealing that a monovalent pseudomannotrioside can cluster DC-SIGN tetramers, providing a basis for therapeutic antagonist design.\",\n      \"evidence\": \"NMR (HSQC, STD, trNOE) of CRD–Lewis x; X-ray co-crystal structures with glycomimetics; ITC, AUC, and DLS demonstrating tetramer clustering\",\n      \"pmids\": [\"25121780\", \"24749535\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo efficacy of glycomimetic antagonists not tested\", \"Whether tetramer clustering by monovalent ligand occurs on intact cell membranes unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"TLR4 co-stimulation was found to redirect DC-SIGN cargo to the cytosol for proteasome-dependent cross-presentation to CD8+ T cells, revealing cooperative innate receptor crosstalk that shapes adaptive immunity.\",\n      \"evidence\": \"Imaging flow cytometry with proteasome inhibitors and antigen-specific CD8+ T cell activation assays in human DCs\",\n      \"pmids\": [\"29963041\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism of cargo translocation from endosome to cytosol not identified\", \"Whether this pathway operates for all DC-SIGN-captured antigens or only specific ligands unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Antigen particle size was demonstrated to determine DC-SIGN intracellular routing fate—soluble antigens to early endosomes versus particulate antigens to surface-accessible invaginated pockets—and a DC-SIGN–Lyn–PI3K signaling axis was identified in cancer cells, extending DC-SIGN function beyond immune contexts.\",\n      \"evidence\": \"Glycopolymers of defined size with endosomal marker colocalization; co-immunoprecipitation of DC-SIGN–Lyn–p85 complex with functional metastasis assays\",\n      \"pmids\": [\"31270240\", \"31217502\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism determining size-dependent sorting at the molecular level unknown\", \"Lyn–PI3K pathway identified only in colorectal cancer cells, not confirmed in primary DCs\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"CD209 was identified as an alternative entry receptor for SARS-CoV-2 via spike RBD binding, relevant in tissues with low ACE2 expression, expanding the pandemic significance of DC-SIGN.\",\n      \"evidence\": \"Purified S-RBD binding assays, siRNA knockdown of CD209, and SARS-CoV-2 infection of endothelial cells\",\n      \"pmids\": [\"34341769\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Glycan dependence of spike–DC-SIGN interaction not fully characterized\", \"Relative contribution of DC-SIGN versus ACE2 in vivo across tissues not quantified\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the full atomic structure of the intact DC-SIGN tetramer with neck domain, the molecular mechanism coupling CRD ligand engagement to cytoplasmic signaling through LARG, Raf-1, and sphingomyelinase pathways, the identity of additional mycobacterial DC-SIGN ligands beyond ManLAM/PIM6, and the in vivo hierarchy of DC-SIGN among alternative pathogen receptors.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Full-length tetramer atomic structure unavailable\", \"Cytoplasmic tail–signaling adaptor interactions not structurally resolved\", \"In vivo mouse models limited by absence of true DC-SIGN ortholog\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 3, 6, 7, 29]},\n      {\"term_id\": \"GO:0038024\", \"supporting_discovery_ids\": [1, 11, 13]},\n      {\"term_id\": \"GO:0098631\", \"supporting_discovery_ids\": [0, 27]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [17, 18]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [1, 11, 22]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [22]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 6, 7, 10, 32]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [6, 7, 25, 30]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [1, 11, 22]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 2, 29]}\n    ],\n    \"complexes\": [\n      \"DC-SIGN tetramer\"\n    ],\n    \"partners\": [\n      \"ICAM2\",\n      \"ARHGEF12\",\n      \"RAF1\",\n      \"LYN\",\n      \"PIK3R1\",\n      \"SMPD2\",\n      \"SMPD1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}