{"gene":"SLC11A2","run_date":"2026-06-10T07:46:32","timeline":{"discoveries":[{"year":1997,"finding":"A missense mutation (G185R) in Nramp2 (SLC11A2) was identified as the causative mutation in microcytic anemia (mk) mice, which have severe defects in intestinal iron absorption and erythroid iron utilization, establishing Nramp2 as an iron transporter.","method":"Positional cloning, missense mutation identification in mk/mk mice with microcytic hypochromic anemia phenotype","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — positional cloning with defined loss-of-function phenotype, independently replicated in Belgrade rat (PMID:9448300)","pmids":["9241278"],"is_preprint":false},{"year":1998,"finding":"The same G185R missense mutation in Nramp2 was found in the anemic Belgrade (b) rat, and functional studies confirmed this mutation disrupts iron transport. The phenotype implicates Nramp2 in both intestinal iron absorption and transport of iron out of the transferrin cycle endosome.","method":"Genetic linkage analysis, mutation identification, functional iron transport studies in transfected cells","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal genetic evidence in two independent animal models (mk mouse and Belgrade rat), functional transport assay confirming loss of function","pmids":["9448300"],"is_preprint":false},{"year":1998,"finding":"Site-directed mutagenesis of transmembrane domain 4 of Nramp2 showed that the G185R mutation causes near-total loss of iron transport function beyond what can be explained by reduced protein amount, indicating disruption of the transport mechanism itself rather than protein degradation.","method":"Site-directed mutagenesis, transfected cell iron transport assays, subcellular localization studies","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro mutagenesis with functional transport assay and localization studies in a single rigorous study","pmids":["9731075"],"is_preprint":false},{"year":1997,"finding":"Nramp2 (SLC11A2) functionally complements the yeast smf1/smf2 double null mutant's hypersensitivity to EGTA and alkaline pH, indicating Nramp2 can transport Mn2+ (and other divalent cations) in yeast; complementation required a functional protein as conserved-residue mutations abrogated activity.","method":"Yeast complementation assay with smf1/smf2 double mutant, mutagenesis of conserved residues","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — heterologous complementation assay with multiple mutants establishing necessity of conserved residues for function","pmids":["9360964"],"is_preprint":false},{"year":1999,"finding":"Nramp2 protein is localized to the apical brush border of duodenal enterocytes (columnar absorptive cells, not goblet cells), and isoform I is dramatically upregulated in the proximal duodenum under iron deprivation, supporting its role in transferrin-independent dietary iron uptake.","method":"Immunoblotting of membrane fractions, immunohistochemistry of intestinal tissue sections, dietary iron manipulation in mice","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct localization by immunofluorescence and fractionation with dietary iron regulation, replicated across multiple studies","pmids":["10361139"],"is_preprint":false},{"year":1999,"finding":"Nramp2/NRAMP2 is expressed as a 90–100 kDa heavily glycosylated integral membrane protein and localizes primarily to recycling endosomes (colocalizing with transferrin), not lysosomes, in macrophages and hematopoietic cells, suggesting its role is transport of Fe2+ across the endosomal membrane into the cytoplasm during the transferrin cycle.","method":"Immunoblotting, immunofluorescence, confocal microscopy, subcellular fractionation, glycosylation analysis","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal localization methods (confocal, fractionation, colocalization with transferrin), confirmed in multiple cell types","pmids":["10049947"],"is_preprint":false},{"year":1999,"finding":"Nramp2 is expressed at the apical membrane of human intestinal Caco-2 cells and mediates proton-dependent iron transport with substrate preference for iron over other divalent cations, accompanied by intracellular acidification.","method":"Iron transport assays in Caco-2 TC7 cells, pH-dependency studies, substrate competition","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional transport assay in human intestinal cell line with pH dependence, single lab","pmids":["10625641"],"is_preprint":false},{"year":2000,"finding":"Human NRAMP2/DMT1 co-sediments with LAMP-1 and LAMP-2-positive late endosomes and lysosomes (not with early endosome marker EEA1 or transferrin receptor) in HEp-2 cells, suggesting it transfers endosomal free Fe2+ into the cytoplasm in the transferrin cycle.","method":"Subcellular fractionation, immunofluorescence of endogenous and GFP-tagged NRAMP2, colocalization with organelle markers","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct localization with multiple markers but single lab and contradicted by other studies showing recycling endosome localization","pmids":["10751401"],"is_preprint":false},{"year":2000,"finding":"Nramp2 isoform II expressed at the plasma membrane of CHO cells transports Fe2+, Co2+, and Cd2+ (but not Mg2+) into the calcein-accessible labile iron pool; transport is time- and pH-dependent, saturable, and proportional to Nramp2 expression level. The TM7-TM8 loop is extracytoplasmic.","method":"Stable CHO transfectants, calcein fluorescence assay, membrane-permeant/impermeant chelators, surface biotinylation, ion selectivity experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro transport reconstitution with multiple substrates, topology determination, saturation kinetics; single lab with multiple orthogonal methods","pmids":["10942769"],"is_preprint":false},{"year":2002,"finding":"DMT1 generates four distinct protein isoforms through alternative use of a 5' exon (exon 1A) in combination with IRE/non-IRE 3' variants; the exon 1A is tissue-specifically expressed in duodenum and kidney and adds 29–31 conserved amino acids to the N-terminus. Both the 5' promoter/exon 1A and the IRE-containing terminal exon participate in tissue-specific iron regulation of DMT1.","method":"cDNA cloning, 5' RACE, quantitative RT-PCR, reporter assays for IRE and 5' exon regulation","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Moderate — molecular characterization with multiple orthogonal methods revealing four isoforms, single lab","pmids":["12209011"],"is_preprint":false},{"year":2003,"finding":"Two conserved histidines in transmembrane domain 6 of Nramp2/DMT1 (His267 and His272) regulate pH-dependent metal transport: inactive His267 and His272 mutants could be rescued by lowering pH, indicating these residues regulate proton coupling rather than directly binding metal substrates. Additionally, three conserved negatively charged residues in TM1, TM4, and TM7 are essential for cation transport.","method":"Site-directed mutagenesis, yeast complementation, mammalian cell iron transport assays, pH rescue experiments","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis with functional rescue experiments in both yeast and mammalian systems, mechanistically informative","pmids":["12522007"],"is_preprint":false},{"year":2003,"finding":"Nramp2 (isoform II) cycles between the plasma membrane and sorting/recycling endosomes (pH ~6.2, maintained by V-ATPase). Internalization is clathrin- and dynamin-dependent, and recycling to the plasma membrane is phosphatidylinositol 3-kinase-dependent. Cholesterol depletion does not affect internalization. Nramp2 and transferrin receptor colocalize and traffic in parallel, functionally coupling them for endosomal iron acquisition.","method":"pH-sensitive fluorescent labeling, 125I-antibody surface kinetics, pharmacological inhibitors (dynasore, wortmannin, cholesterol depletion), dual labeling confocal microscopy","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal trafficking methods with rigorous pharmacological dissection, single lab","pmids":["12724326"],"is_preprint":false},{"year":2003,"finding":"Nramp1 and Nramp2 have indistinguishable membrane topology and transport properties (Fe2+, Mn2+, Co2+) when both expressed at the plasma membrane; Nramp1 may be a more efficient Mn2+ transporter than Nramp2. This suggests Nramp1 divalent-metal transport at the phagosomal membrane is mechanistically similar to Nramp2 at endosomal membranes.","method":"Plasma membrane expression of HA-tagged Nramp1 and Nramp2 in CHO cells, immunofluorescence, surface biotinylation, calcein/Fura2 fluorescence assays, radioisotopic 55Fe2+/54Mn2+ transport assays","journal":"Blood","confidence":"High","confidence_rationale":"Tier 1 / Moderate — direct comparison of transport properties with multiple substrates and orthogonal methods in same system","pmids":["12750164"],"is_preprint":false},{"year":2001,"finding":"In erythroid cells, DMT1 isoform II (non-IRE) co-localizes with the transferrin receptor and is required for iron transport across the endosomal membrane after transferrin-bound iron release; mk/mk reticulocytes show impaired Fe2+ transport across the endosomal membrane (despite normal iron release from transferrin inside the endosome) and express little DMT1 despite robust transferrin receptor expression, indicating the G185R mutation affects both transport function and protein stability/targeting in erythroid cells.","method":"Immunoblotting of membrane fractions, double immunofluorescence and confocal microscopy, isoform-specific antisera, iron uptake and heme incorporation assays in mk/mk reticulocytes","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods with mechanistic dissection of the transferrin cycle step; confirmed in animal model","pmids":["11739192"],"is_preprint":false},{"year":2005,"finding":"Selective in vivo inactivation of murine Slc11a2 established that it is essential for intestinal non-heme iron absorption after birth and for normal hemoglobin production during erythroid precursor development, but is not required for materno-fetal iron transfer. Hepatocytes and most other cells have an alternative, unidentified iron uptake mechanism.","method":"Global and conditional Slc11a2 knockout mice, phenotypic analysis of iron absorption, hemoglobin production, and tissue iron levels","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — definitive in vivo loss-of-function with tissue-specific knockouts and multiple phenotypic readouts","pmids":["15849611"],"is_preprint":false},{"year":2000,"finding":"The G185R mutation in mk/mk mice impairs both the transport activity and the targeting of DMT1 to the apical membrane of duodenal enterocytes; despite a dramatic increase in DMT1 mRNA and protein expression in the duodenum, little protein is seen at the apical brush border, suggesting the mutation affects both function and membrane targeting.","method":"Northern blot, immunoblotting, immunohistochemical analysis of mk/mk vs. heterozygote duodenum","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple methods (mRNA, protein, IHC) demonstrating mislocalization in animal model","pmids":["11090085"],"is_preprint":false},{"year":2003,"finding":"The first external loop of DCT1/SLC11A2 is involved in metal ion binding and specificity: mutation G119A nearly abolishes transport; Q126D abolishes transport but D124A/Q126D double mutant partially restores it and shifts specificity toward Fe2+; D124A retains Fe2+ uptake but markedly reduces Mn2+ transport.","method":"Site-directed mutagenesis, yeast complementation (smf1Δ), Xenopus oocyte electrophysiology, 54Mn2+ uptake assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis with both functional and electrophysiological characterization in two systems","pmids":["12954986"],"is_preprint":false},{"year":2004,"finding":"The mutation F227I in transmembrane domain 4 of DCT1/SLC11A2 increases the coupling efficiency between metal ion and proton transport by up to 14-fold, demonstrating that the normal low coupling ratio results from a proton slippage mechanism that is not mechanistically obligatory.","method":"Site-directed mutagenesis, yeast complementation, Xenopus oocyte electrophysiology","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis with electrophysiology in two orthogonal systems revealing mechanistic proton slippage","pmids":["15475345"],"is_preprint":false},{"year":2005,"finding":"The carboxyl-terminus YLLNT motif of DMT1 isoform II is the major signal for internalization from the plasma membrane into recycling endosomes; deletion of this motif increases surface expression due to impaired internalization and redirects internalized DMT1 to lysosomes rather than recycling endosomes.","method":"Carboxyl- and amino-terminus truncation mutants stably expressed in LLC-PK1 cells, surface labeling with 125I-antibody kinetics, immunofluorescence, subcellular localization","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — mutagenesis with kinetic surface labeling and localization studies; mechanistic dissection of trafficking signal","pmids":["16142913"],"is_preprint":false},{"year":2006,"finding":"The two DMT1 isoforms (I/+IRE and II/-IRE) have distinct subcellular targeting and recycling properties in LLC-PK1 kidney cells: isoform I shows higher surface expression and slower internalization, and upon internalization is targeted to lysosomes rather than recycling endosomes (as isoform II is). Thus, alternative splicing at the C-terminus controls the subcellular site of Fe2+ transport.","method":"Stable transfection in LLC-PK1 cells, immunofluorescence, surface labeling, endocytosis kinetics, lysosomal/endosomal marker colocalization","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct isoform comparison with multiple trafficking assays; mechanistic link between C-terminus isoform and subcellular destination","pmids":["16475818"],"is_preprint":false},{"year":2006,"finding":"The R416C mutation in transmembrane domain 9 of human DMT1 causes multiple functional deficiencies including defective protein processing, loss of transport activity, impaired cell surface targeting, and retention in the ER. Conservative substitution R416K preserves function, demonstrating R416 is essential for proper folding and trafficking.","method":"Site-directed mutagenesis (R416C, R416A, R416K, R416E), LLC-PK1 expression, transport assays, immunofluorescence subcellular localization, protein processing analysis","journal":"Blood cells, molecules & diseases","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple mutations with functional and localization characterization; mechanistically informative about TM9 role","pmids":["16584902"],"is_preprint":false},{"year":2009,"finding":"Epitope-tagging topology mapping of Slc11a2 confirmed a 12-transmembrane domain architecture with intracellular N- and C-termini; loops TM4-5, TM6-7, and TM10-11 are intracellular, while loops TM5-6, TM7-8, and TM11-12 are extracellular. Insertions at positions 98, 131, 175, 403, and 432 abrogated transport, identifying functionally critical regions. Homology threading models show 2-fold structural symmetry for TM1-5 and TM6-10.","method":"HA epitope insertion mutagenesis at 13 positions, immunofluorescence in intact and permeabilized LLC-PK1 cells, transport activity assays, homology threading structural modeling","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — systematic topology mapping with 13 insertion positions and functional validation, single rigorous study","pmids":["19621945"],"is_preprint":false},{"year":2002,"finding":"Nramp2/DMT1 is recruited to the phagosomal membrane of macrophages (RAW264.7) and Sertoli cells after phagocytosis, associating with LAMP1-, cathepsin D-, and rab7-positive mature phagosomes, suggesting DMT1 transports divalent metals out of the phagosomal lumen, analogous to Nramp1.","method":"Immunofluorescence, in vitro biochemical studies with purified latex bead-containing phagosomes, erythrocyte and sperm phagocytosis assays","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct localization by biochemical fractionation and immunofluorescence, single lab, no functional transport measurement at phagosome","pmids":["12239176"],"is_preprint":false},{"year":2001,"finding":"DMT1 is localized intracellularly (not at plasma membranes) in the adult rat testis, expressed in both Sertoli and germ cells in a stage-dependent manner during the spermatogenic cycle, suggesting a role in intracellular iron handling between compartments rather than transepithelial iron transport.","method":"Northern blot, RT-PCR, immunoblotting, immunohistochemistry of developing and adult rat testis","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct localization with multiple methods but no functional transport measurement; single lab","pmids":["15355847"],"is_preprint":false},{"year":2001,"finding":"In rat kidney, DMT1 immunoreactivity is strongest in collecting ducts (both principal and intercalated cells) and distal convoluted tubules (apical staining), with intracellular staining throughout the nephron, consistent with DMT1 providing the molecular mechanism for apical iron entry in the distal nephron.","method":"Affinity-purified anti-DMT1 antibody, Western analysis, immunofluorescence, confocal microscopy in rat kidney sections","journal":"American journal of physiology. Renal physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct localization with multiple techniques, single lab, functional inference from localization","pmids":["11292622"],"is_preprint":false},{"year":2000,"finding":"DMT1 is expressed in human term placenta syncytiotrophoblast, localizing to both the cytoplasm and the basal (fetal-side) membrane, distinct from transferrin receptor which is on the apical (maternal) side, suggesting DMT1 mediates iron transfer from endosomes to cytoplasm and across the basal membrane to the fetus.","method":"Immunohistochemistry of frozen term human placenta sections, double staining with anti-TfR antibody","journal":"Placenta","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct immunolocalization in human tissue, single lab, functional inference from localization without transport assay","pmids":["11095929"],"is_preprint":false},{"year":2008,"finding":"Overexpression of DMT1 in CHO cells greatly increases ferrous iron uptake, with Fe(II) transported far more efficiently than Fe(III). Fe(III) transport by DMT1-expressing CHO cells can be inhibited by a membrane-impermeant oxidant, indicating that a membrane ferric reductase is needed to reduce Fe(III) to Fe(II) for DMT1-mediated transport.","method":"59Fe transport assays in Nramp2-transfected vs. control CHO cells, oxidant inhibition experiments","journal":"Experimental hematology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional transport assay with mechanistic pharmacological dissection, single lab","pmids":["18722041"],"is_preprint":false},{"year":2011,"finding":"The N491S mutation in human SLC11A2 causes abnormal protein trafficking (as demonstrated in HuH7 hepatic cells with dsRed2-tagged DMT1), while the G212V mutation does not affect trafficking; N491S together with G212V leads to microcytic anemia and liver iron overload in a patient.","method":"Fluorescent protein tagging and live-cell imaging of DMT1 trafficking in HuH7 cells, splicing analysis in patient leukocytes, real-time qPCR of DMT1 isoforms in human liver","journal":"Blood cells, molecules & diseases","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct trafficking assay with fluorescent fusion protein in human cell line, single lab","pmids":["21871825"],"is_preprint":false},{"year":2011,"finding":"The E399D mutation in DMT1 exon 12 does not affect protein stability, membrane targeting, endosomal trafficking, or transport activity in LLC-PK1 cells, establishing it as a functionally neutral polymorphism and indicating that disease in the patient bearing the 1285G>C mutation is caused by exon 12 skipping (reduced protein quantity) rather than the E399D amino acid change.","method":"Site-directed mutagenesis (E399D, E399Q, E399A) stably expressed in LLC-PK1 cells, transport assays, immunofluorescence","journal":"Blood cells, molecules & diseases","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro mutagenesis with functional and localization characterization; single lab negative-result finding","pmids":["16023393"],"is_preprint":false},{"year":2010,"finding":"Calcium reduces DMT1 protein expression at the apical cell membrane (not total cellular DMT1), as shown in fractionated Caco-2 cell lysates, suggesting that calcium inhibits non-heme iron absorption by decreasing DMT1 at the apical surface.","method":"Fractionation of Caco-2 cell membrane vs. whole cell lysates, Western blotting for DMT1 and ferroportin after iron and calcium treatments","journal":"Journal of agricultural and food chemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, fractionation-based localization without direct transport measurement or confirmation of functional consequence","pmids":["20597505"],"is_preprint":false},{"year":2007,"finding":"A single reciprocal mutation I144F in TM2 of DCT1/SLC11A2 abolishes metal ion transport and increases proton slip currents; a double mutant I144F/F227I restores uptake activity and reduces slip currents, demonstrating that TM2 and TM4 are functionally coupled in the proton-metal ion coupling mechanism.","method":"Site-directed mutagenesis, metal ion uptake assays, Xenopus oocyte electrophysiology","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1 / Moderate — mutagenesis with both functional and electrophysiological characterization revealing mechanistic inter-TM coupling","pmids":["17980698"],"is_preprint":false},{"year":2015,"finding":"A non-competitive inhibitor (pyrimidinone 8, Ki ~20 μM) of human DMT1 was discovered that does not affect cell surface expression of hDMT1, providing the first experimental evidence that DMT1 can be allosterically modulated by pharmacological agents.","method":"Ligand-based virtual screening, radiolabeled iron uptake assay in hDMT1-expressing cells, surface expression analysis","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional transport inhibition assay with surface expression control; single lab, allosteric mechanism inferred from non-competitive kinetics","pmids":["26047847"],"is_preprint":false},{"year":2023,"finding":"Microglial-specific knockdown of Slc11a2 in male mice blunts LPS-induced pro-inflammatory cytokine expression (Il6, Tnfα, Il1β), reduces plasma cytokines, upregulates iron export/recycling genes, and improves acute sickness behavior in a sex-specific manner (males but not females), establishing a feed-forward link between microglial iron import via DMT1 and pro-inflammatory activation in vivo.","method":"Tamoxifen-inducible Cx3cr1Cre-ERT2 microglial-specific Slc11a2 knockdown mice, LPS challenge, plasma cytokine measurement, bulk RNA-seq of isolated microglia","journal":"Brain, behavior, and immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo microglial-specific knockdown with behavioral and transcriptomic readouts; single lab but multiple orthogonal methods","pmids":["38141840"],"is_preprint":false},{"year":2022,"finding":"The G75R mutation in SLC11A2 causes improper DMT1 accumulation in lysosomes in HuTu 80 cells, leading to significantly decreased DMT1 protein levels in patient-derived lymphoblastoid cell lines, thus producing loss-of-function microcytic anemia with iron overload.","method":"Functional characterization of G75R in HuTu 80 cells by immunofluorescence colocalization with lysosomal markers; patient-derived LCL DMT1 protein quantification","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct localization in transfected cells with patient validation; single lab","pmids":["35457224"],"is_preprint":false}],"current_model":"SLC11A2 (DMT1/Nramp2/DCT1) is a 12-transmembrane-domain, heavily glycosylated integral membrane protein that functions as a proton-coupled divalent metal (Fe2+, Mn2+, Co2+, Cd2+) transporter: it mediates apical uptake of dietary non-heme iron at the duodenal brush border (isoform I/+IRE, which recycles through lysosomes) and transports Fe2+ out of acidified recycling endosomes into the cytoplasm during the transferrin cycle in most other cells (isoform II/-IRE, which internalizes via clathrin/dynamin and recycles back to the plasma membrane via a PI3K-dependent pathway); transport is driven by the proton electrochemical gradient, with conserved residues in TM1/TM4/TM7 essential for cation transport and His267/His272 in TM6 regulating pH-dependent coupling rather than direct metal binding; the G185R mutation found in mk mice and Belgrade rats disrupts both transport function and correct apical membrane targeting; the carboxyl-terminal YLLNT motif of isoform II is required for internalization and endosomal recycling; and DMT1 is also recruited to phagosomal membranes in macrophages, expressed in microglia where iron import feeds inflammatory signaling, and essential for erythropoiesis in vivo."},"narrative":{"mechanistic_narrative":"SLC11A2 (DMT1/Nramp2/DCT1) is a 12-transmembrane-domain, heavily glycosylated integral membrane protein that functions as a proton-coupled divalent metal transporter and is the principal route for cellular acquisition of non-heme iron, with loss-of-function disrupting both dietary iron absorption and erythroid iron utilization [PMID:9241278, PMID:9448300, PMID:19621945]. It transports Fe2+ (preferentially over Fe3+, which requires prior reduction by a membrane ferric reductase) as well as Mn2+, Co2+, and Cd2+ into the labile iron pool, driven by the proton electrochemical gradient with attendant intracellular acidification [PMID:10942769, PMID:12954986, PMID:18722041]. Transport mechanism has been mapped to conserved residues: negatively charged residues in TM1/TM4/TM7 and a first-extracellular-loop region (G119, D124, Q126) govern cation transport and metal specificity, His267/His272 in TM6 regulate proton coupling rather than directly binding metal, and coupling efficiency reflects a non-obligatory proton-slippage mechanism in which TM2 and TM4 are functionally coupled (F227I, I144F) [PMID:12522007, PMID:12954986, PMID:15475345, PMID:17980698]. DMT1 is generated as multiple isoforms through alternative 5' (exon 1A) and 3' (IRE/non-IRE) usage that direct tissue-specific iron regulation and distinct subcellular trafficking [PMID:12209011, PMID:16475818]. At the duodenal brush border it mediates apical uptake of dietary iron and is upregulated under iron deprivation (isoform I) [PMID:10361139], whereas in erythroid and other cells isoform II colocalizes and traffics in parallel with the transferrin receptor, cycling between the plasma membrane and acidified recycling endosomes to release endosomal Fe2+ into the cytoplasm during the transferrin cycle; its C-terminal YLLNT motif directs clathrin/dynamin-dependent internalization and PI3K-dependent recycling, and ablating it redirects DMT1 to lysosomes [PMID:10049947, PMID:12724326, PMID:11739192, PMID:16142913]. In vivo inactivation established DMT1 as essential for postnatal intestinal iron absorption and erythroid hemoglobin production but dispensable for materno-fetal iron transfer [PMID:15849611], and human disease mutations that impair folding, trafficking, or expression (e.g. R416C, N491S, G75R) cause microcytic anemia with hepatic iron overload [PMID:16584902, PMID:21871825, PMID:35457224]. Beyond canonical iron handling, DMT1 is recruited to mature macrophage phagosomes and supports microglial iron import that drives pro-inflammatory activation in vivo [PMID:12239176, PMID:38141840].","teleology":[{"year":1998,"claim":"Established that SLC11A2/Nramp2 is itself an iron transporter whose loss causes systemic iron deficiency, answering whether a single gene links intestinal absorption and erythroid iron utilization.","evidence":"Positional cloning of the G185R mutation in mk mice and the Belgrade rat with functional transport assays in transfected cells","pmids":["9241278","9448300","9731075"],"confidence":"High","gaps":["G185R conflates loss of transport with loss of membrane targeting","did not resolve substrate range or the driving force for transport"]},{"year":1998,"claim":"Demonstrated the transporter handles divalent cations beyond iron, framing it as a broad-specificity divalent metal transporter.","evidence":"Heterologous yeast smf1/smf2 double-null complementation with conserved-residue mutants","pmids":["9360964"],"confidence":"High","gaps":["yeast assay does not quantify relative substrate selectivity in mammalian cells","did not establish proton coupling directly"]},{"year":2000,"claim":"Defined the proton-coupled, saturable transport of Fe2+/Co2+/Cd2+ into the cytoplasmic labile iron pool and fixed key topological features.","evidence":"Calcein fluorescence and 55Fe transport assays in stable CHO transfectants with surface biotinylation and ion-selectivity tests","pmids":["10942769","10625641"],"confidence":"High","gaps":["the molecular determinants of proton coupling were not yet mapped","did not address physiological subcellular site of transport"]},{"year":2003,"claim":"Resolved the iron-acquisition mechanism in the transferrin cycle, showing DMT1 isoform II cycles with the transferrin receptor through acidified recycling endosomes via defined trafficking pathways.","evidence":"pH-sensitive labeling, surface kinetics, pharmacological inhibition (dynasore, wortmannin) and dual-label confocal microscopy; complemented by erythroid mk/mk reticulocyte analysis","pmids":["12724326","11739192","10049947"],"confidence":"High","gaps":["conflicting reports placed DMT1 in late endosomes/lysosomes versus recycling endosomes (#7)","molecular adaptors for clathrin/PI3K-dependent steps not identified"]},{"year":2005,"claim":"Mapped sequence determinants of trafficking, identifying the C-terminal YLLNT motif as the internalization/recycling signal and showing C-terminal splicing dictates the subcellular site of Fe2+ transport.","evidence":"Truncation and isoform-comparison mutants in LLC-PK1 cells with 125I-antibody surface kinetics and marker colocalization","pmids":["16142913","16475818"],"confidence":"High","gaps":["the trafficking machinery recognizing YLLNT was not identified","isoform-specific transport rates in native tissue not measured"]},{"year":2007,"claim":"Dissected the proton-metal coupling mechanism, showing coupling is non-obligatory proton slippage tunable by inter-helix interactions and gated by specific residues.","evidence":"Site-directed mutagenesis (His267/His272, TM1/TM4/TM7 residues, F227I, I144F, first-loop G119/D124/Q126) with Xenopus oocyte electrophysiology and uptake assays","pmids":["12522007","12954986","15475345","17980698"],"confidence":"High","gaps":["no atomic-resolution structure of the human transporter","exact coordination geometry of bound metal not defined"]},{"year":2009,"claim":"Provided a validated 12-TM topology with intracellular N/C termini and identified functionally critical insertion-sensitive regions, constraining structural models.","evidence":"Systematic HA-epitope insertion at 13 positions with permeabilized-cell immunofluorescence and homology threading","pmids":["19621945"],"confidence":"High","gaps":["threading model not validated against an experimental structure","conformational cycle during transport not resolved"]},{"year":2005,"claim":"Established the physiological non-redundant roles in vivo, separating intestinal/erythroid requirement from dispensability in materno-fetal transfer and revealing an alternative hepatocyte iron-uptake route.","evidence":"Global and conditional Slc11a2 knockout mice with iron-absorption, hemoglobin, and tissue-iron phenotyping","pmids":["15849611"],"confidence":"High","gaps":["the alternative iron-uptake mechanism in hepatocytes was not identified","cell-autonomous roles in non-erythroid tissues left open"]},{"year":2022,"claim":"Connected biochemical trafficking defects to human disease, showing folding/trafficking-disrupting mutations cause microcytic anemia with hepatic iron overload.","evidence":"Functional characterization of R416C, N491S, and G75R in human cell lines with patient-derived cell validation and splicing analysis","pmids":["16584902","21871825","35457224","16023393"],"confidence":"Medium","gaps":["single-lab functional assays for several variants","genotype-phenotype severity relationships not systematically established"]},{"year":2023,"claim":"Extended DMT1 function beyond classical iron handling to immune cells, linking microglial iron import to pro-inflammatory activation in vivo.","evidence":"Tamoxifen-inducible microglial-specific Slc11a2 knockdown mice with LPS challenge, plasma cytokine measurement, and microglial RNA-seq; plus phagosomal recruitment in macrophages","pmids":["38141840","12239176"],"confidence":"Medium","gaps":["sex-specific effect (males only) mechanism not explained","no direct measurement of transport at the phagosomal/microglial membrane"]},{"year":null,"claim":"How DMT1 is allosterically regulated and pharmacologically targeted, and the structural basis of its transport cycle, remain open.","evidence":"A non-competitive small-molecule inhibitor exists but the allosteric site and conformational mechanism are uncharacterized","pmids":[],"confidence":"Low","gaps":["no experimental structure of the human transporter","allosteric modulatory site not defined","endogenous regulators of trafficking unidentified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,8,16,26]},{"term_id":"GO:0140104","term_label":"molecular carrier activity","supporting_discovery_ids":[8,10,17]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[4,8,11]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[5,11,18]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[7,19,33]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,8,14]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[4,14]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[22,32]}],"complexes":[],"partners":["TFRC"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P49281","full_name":"Natural resistance-associated macrophage protein 2","aliases":["Divalent cation transporter 1","Divalent metal transporter 1","DMT-1","Solute carrier family 11 member 2"],"length_aa":568,"mass_kda":62.3,"function":"Proton-coupled metal ion symporter operating with a proton to metal ion stoichiometry of 1:1 (PubMed:17109629, PubMed:17293870, PubMed:22736759, PubMed:25326704, PubMed:25491917). Selectively transports various divalent metal cations, in decreasing affinity: Cd(2+) > Fe(2+) > Co(2+), Mn(2+) >> Zn(2+), Ni(2+), VO(2+) (PubMed:17109629, PubMed:17293870, PubMed:22736759, PubMed:25326704, PubMed:25491917). Essential for maintenance of iron homeostasis by modulating intestinal absorption of dietary Fe(2+) and TF-associated endosomal Fe(2+) transport in erythroid precursors and other cells (By similarity). Enables Fe(2+) and Mn(2+) ion entry into mitochondria, and is thus expected to promote mitochondrial heme synthesis, iron-sulfur cluster biogenesis and antioxidant defense (By similarity) (PubMed:24448823). 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SLC48A1","url":"https://www.omim.org/entry/612187"},{"mim_id":"612050","title":"NEDD4 FAMILY-INTERACTING PROTEIN 1; NDFIP1","url":"https://www.omim.org/entry/612050"},{"mim_id":"606464","title":"HEPCIDIN ANTIMICROBIAL PEPTIDE; HAMP","url":"https://www.omim.org/entry/606464"},{"mim_id":"600523","title":"SOLUTE CARRIER FAMILY 11 (PROTON-COUPLED DIVALENT METAL ION TRANSPORTER), MEMBER 2; SLC11A2","url":"https://www.omim.org/entry/600523"},{"mim_id":"235200","title":"HEMOCHROMATOSIS, TYPE 1; HFE1","url":"https://www.omim.org/entry/235200"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SLC11A2"},"hgnc":{"alias_symbol":["DCT1","DMT1","DMT-1","FLJ37416"],"prev_symbol":["NRAMP2"]},"alphafold":{"accession":"P49281","domains":[{"cath_id":"1.20.1740.10","chopping":"69-429","consensus_level":"high","plddt":90.7725,"start":69,"end":429}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P49281","model_url":"https://alphafold.ebi.ac.uk/files/AF-P49281-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P49281-F1-predicted_aligned_error_v6.png","plddt_mean":80.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SLC11A2","jax_strain_url":"https://www.jax.org/strain/search?query=SLC11A2"},"sequence":{"accession":"P49281","fasta_url":"https://rest.uniprot.org/uniprotkb/P49281.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P49281/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P49281"}},"corpus_meta":[{"pmid":"9241278","id":"PMC_9241278","title":"Microcytic 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hypochromic anemia phenotype\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — positional cloning with defined loss-of-function phenotype, independently replicated in Belgrade rat (PMID:9448300)\",\n      \"pmids\": [\"9241278\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"The same G185R missense mutation in Nramp2 was found in the anemic Belgrade (b) rat, and functional studies confirmed this mutation disrupts iron transport. The phenotype implicates Nramp2 in both intestinal iron absorption and transport of iron out of the transferrin cycle endosome.\",\n      \"method\": \"Genetic linkage analysis, mutation identification, functional iron transport studies in transfected cells\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal genetic evidence in two independent animal models (mk mouse and Belgrade rat), functional transport assay confirming loss of function\",\n      \"pmids\": [\"9448300\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Site-directed mutagenesis of transmembrane domain 4 of Nramp2 showed that the G185R mutation causes near-total loss of iron transport function beyond what can be explained by reduced protein amount, indicating disruption of the transport mechanism itself rather than protein degradation.\",\n      \"method\": \"Site-directed mutagenesis, transfected cell iron transport assays, subcellular localization studies\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro mutagenesis with functional transport assay and localization studies in a single rigorous study\",\n      \"pmids\": [\"9731075\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"Nramp2 (SLC11A2) functionally complements the yeast smf1/smf2 double null mutant's hypersensitivity to EGTA and alkaline pH, indicating Nramp2 can transport Mn2+ (and other divalent cations) in yeast; complementation required a functional protein as conserved-residue mutations abrogated activity.\",\n      \"method\": \"Yeast complementation assay with smf1/smf2 double mutant, mutagenesis of conserved residues\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — heterologous complementation assay with multiple mutants establishing necessity of conserved residues for function\",\n      \"pmids\": [\"9360964\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Nramp2 protein is localized to the apical brush border of duodenal enterocytes (columnar absorptive cells, not goblet cells), and isoform I is dramatically upregulated in the proximal duodenum under iron deprivation, supporting its role in transferrin-independent dietary iron uptake.\",\n      \"method\": \"Immunoblotting of membrane fractions, immunohistochemistry of intestinal tissue sections, dietary iron manipulation in mice\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct localization by immunofluorescence and fractionation with dietary iron regulation, replicated across multiple studies\",\n      \"pmids\": [\"10361139\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Nramp2/NRAMP2 is expressed as a 90–100 kDa heavily glycosylated integral membrane protein and localizes primarily to recycling endosomes (colocalizing with transferrin), not lysosomes, in macrophages and hematopoietic cells, suggesting its role is transport of Fe2+ across the endosomal membrane into the cytoplasm during the transferrin cycle.\",\n      \"method\": \"Immunoblotting, immunofluorescence, confocal microscopy, subcellular fractionation, glycosylation analysis\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal localization methods (confocal, fractionation, colocalization with transferrin), confirmed in multiple cell types\",\n      \"pmids\": [\"10049947\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Nramp2 is expressed at the apical membrane of human intestinal Caco-2 cells and mediates proton-dependent iron transport with substrate preference for iron over other divalent cations, accompanied by intracellular acidification.\",\n      \"method\": \"Iron transport assays in Caco-2 TC7 cells, pH-dependency studies, substrate competition\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional transport assay in human intestinal cell line with pH dependence, single lab\",\n      \"pmids\": [\"10625641\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Human NRAMP2/DMT1 co-sediments with LAMP-1 and LAMP-2-positive late endosomes and lysosomes (not with early endosome marker EEA1 or transferrin receptor) in HEp-2 cells, suggesting it transfers endosomal free Fe2+ into the cytoplasm in the transferrin cycle.\",\n      \"method\": \"Subcellular fractionation, immunofluorescence of endogenous and GFP-tagged NRAMP2, colocalization with organelle markers\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct localization with multiple markers but single lab and contradicted by other studies showing recycling endosome localization\",\n      \"pmids\": [\"10751401\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"Nramp2 isoform II expressed at the plasma membrane of CHO cells transports Fe2+, Co2+, and Cd2+ (but not Mg2+) into the calcein-accessible labile iron pool; transport is time- and pH-dependent, saturable, and proportional to Nramp2 expression level. The TM7-TM8 loop is extracytoplasmic.\",\n      \"method\": \"Stable CHO transfectants, calcein fluorescence assay, membrane-permeant/impermeant chelators, surface biotinylation, ion selectivity experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro transport reconstitution with multiple substrates, topology determination, saturation kinetics; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"10942769\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"DMT1 generates four distinct protein isoforms through alternative use of a 5' exon (exon 1A) in combination with IRE/non-IRE 3' variants; the exon 1A is tissue-specifically expressed in duodenum and kidney and adds 29–31 conserved amino acids to the N-terminus. Both the 5' promoter/exon 1A and the IRE-containing terminal exon participate in tissue-specific iron regulation of DMT1.\",\n      \"method\": \"cDNA cloning, 5' RACE, quantitative RT-PCR, reporter assays for IRE and 5' exon regulation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — molecular characterization with multiple orthogonal methods revealing four isoforms, single lab\",\n      \"pmids\": [\"12209011\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Two conserved histidines in transmembrane domain 6 of Nramp2/DMT1 (His267 and His272) regulate pH-dependent metal transport: inactive His267 and His272 mutants could be rescued by lowering pH, indicating these residues regulate proton coupling rather than directly binding metal substrates. Additionally, three conserved negatively charged residues in TM1, TM4, and TM7 are essential for cation transport.\",\n      \"method\": \"Site-directed mutagenesis, yeast complementation, mammalian cell iron transport assays, pH rescue experiments\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with functional rescue experiments in both yeast and mammalian systems, mechanistically informative\",\n      \"pmids\": [\"12522007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Nramp2 (isoform II) cycles between the plasma membrane and sorting/recycling endosomes (pH ~6.2, maintained by V-ATPase). Internalization is clathrin- and dynamin-dependent, and recycling to the plasma membrane is phosphatidylinositol 3-kinase-dependent. Cholesterol depletion does not affect internalization. Nramp2 and transferrin receptor colocalize and traffic in parallel, functionally coupling them for endosomal iron acquisition.\",\n      \"method\": \"pH-sensitive fluorescent labeling, 125I-antibody surface kinetics, pharmacological inhibitors (dynasore, wortmannin, cholesterol depletion), dual labeling confocal microscopy\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal trafficking methods with rigorous pharmacological dissection, single lab\",\n      \"pmids\": [\"12724326\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Nramp1 and Nramp2 have indistinguishable membrane topology and transport properties (Fe2+, Mn2+, Co2+) when both expressed at the plasma membrane; Nramp1 may be a more efficient Mn2+ transporter than Nramp2. This suggests Nramp1 divalent-metal transport at the phagosomal membrane is mechanistically similar to Nramp2 at endosomal membranes.\",\n      \"method\": \"Plasma membrane expression of HA-tagged Nramp1 and Nramp2 in CHO cells, immunofluorescence, surface biotinylation, calcein/Fura2 fluorescence assays, radioisotopic 55Fe2+/54Mn2+ transport assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct comparison of transport properties with multiple substrates and orthogonal methods in same system\",\n      \"pmids\": [\"12750164\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"In erythroid cells, DMT1 isoform II (non-IRE) co-localizes with the transferrin receptor and is required for iron transport across the endosomal membrane after transferrin-bound iron release; mk/mk reticulocytes show impaired Fe2+ transport across the endosomal membrane (despite normal iron release from transferrin inside the endosome) and express little DMT1 despite robust transferrin receptor expression, indicating the G185R mutation affects both transport function and protein stability/targeting in erythroid cells.\",\n      \"method\": \"Immunoblotting of membrane fractions, double immunofluorescence and confocal microscopy, isoform-specific antisera, iron uptake and heme incorporation assays in mk/mk reticulocytes\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods with mechanistic dissection of the transferrin cycle step; confirmed in animal model\",\n      \"pmids\": [\"11739192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Selective in vivo inactivation of murine Slc11a2 established that it is essential for intestinal non-heme iron absorption after birth and for normal hemoglobin production during erythroid precursor development, but is not required for materno-fetal iron transfer. Hepatocytes and most other cells have an alternative, unidentified iron uptake mechanism.\",\n      \"method\": \"Global and conditional Slc11a2 knockout mice, phenotypic analysis of iron absorption, hemoglobin production, and tissue iron levels\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — definitive in vivo loss-of-function with tissue-specific knockouts and multiple phenotypic readouts\",\n      \"pmids\": [\"15849611\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"The G185R mutation in mk/mk mice impairs both the transport activity and the targeting of DMT1 to the apical membrane of duodenal enterocytes; despite a dramatic increase in DMT1 mRNA and protein expression in the duodenum, little protein is seen at the apical brush border, suggesting the mutation affects both function and membrane targeting.\",\n      \"method\": \"Northern blot, immunoblotting, immunohistochemical analysis of mk/mk vs. heterozygote duodenum\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods (mRNA, protein, IHC) demonstrating mislocalization in animal model\",\n      \"pmids\": [\"11090085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The first external loop of DCT1/SLC11A2 is involved in metal ion binding and specificity: mutation G119A nearly abolishes transport; Q126D abolishes transport but D124A/Q126D double mutant partially restores it and shifts specificity toward Fe2+; D124A retains Fe2+ uptake but markedly reduces Mn2+ transport.\",\n      \"method\": \"Site-directed mutagenesis, yeast complementation (smf1Δ), Xenopus oocyte electrophysiology, 54Mn2+ uptake assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with both functional and electrophysiological characterization in two systems\",\n      \"pmids\": [\"12954986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The mutation F227I in transmembrane domain 4 of DCT1/SLC11A2 increases the coupling efficiency between metal ion and proton transport by up to 14-fold, demonstrating that the normal low coupling ratio results from a proton slippage mechanism that is not mechanistically obligatory.\",\n      \"method\": \"Site-directed mutagenesis, yeast complementation, Xenopus oocyte electrophysiology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with electrophysiology in two orthogonal systems revealing mechanistic proton slippage\",\n      \"pmids\": [\"15475345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"The carboxyl-terminus YLLNT motif of DMT1 isoform II is the major signal for internalization from the plasma membrane into recycling endosomes; deletion of this motif increases surface expression due to impaired internalization and redirects internalized DMT1 to lysosomes rather than recycling endosomes.\",\n      \"method\": \"Carboxyl- and amino-terminus truncation mutants stably expressed in LLC-PK1 cells, surface labeling with 125I-antibody kinetics, immunofluorescence, subcellular localization\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mutagenesis with kinetic surface labeling and localization studies; mechanistic dissection of trafficking signal\",\n      \"pmids\": [\"16142913\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The two DMT1 isoforms (I/+IRE and II/-IRE) have distinct subcellular targeting and recycling properties in LLC-PK1 kidney cells: isoform I shows higher surface expression and slower internalization, and upon internalization is targeted to lysosomes rather than recycling endosomes (as isoform II is). Thus, alternative splicing at the C-terminus controls the subcellular site of Fe2+ transport.\",\n      \"method\": \"Stable transfection in LLC-PK1 cells, immunofluorescence, surface labeling, endocytosis kinetics, lysosomal/endosomal marker colocalization\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct isoform comparison with multiple trafficking assays; mechanistic link between C-terminus isoform and subcellular destination\",\n      \"pmids\": [\"16475818\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"The R416C mutation in transmembrane domain 9 of human DMT1 causes multiple functional deficiencies including defective protein processing, loss of transport activity, impaired cell surface targeting, and retention in the ER. Conservative substitution R416K preserves function, demonstrating R416 is essential for proper folding and trafficking.\",\n      \"method\": \"Site-directed mutagenesis (R416C, R416A, R416K, R416E), LLC-PK1 expression, transport assays, immunofluorescence subcellular localization, protein processing analysis\",\n      \"journal\": \"Blood cells, molecules & diseases\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple mutations with functional and localization characterization; mechanistically informative about TM9 role\",\n      \"pmids\": [\"16584902\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Epitope-tagging topology mapping of Slc11a2 confirmed a 12-transmembrane domain architecture with intracellular N- and C-termini; loops TM4-5, TM6-7, and TM10-11 are intracellular, while loops TM5-6, TM7-8, and TM11-12 are extracellular. Insertions at positions 98, 131, 175, 403, and 432 abrogated transport, identifying functionally critical regions. Homology threading models show 2-fold structural symmetry for TM1-5 and TM6-10.\",\n      \"method\": \"HA epitope insertion mutagenesis at 13 positions, immunofluorescence in intact and permeabilized LLC-PK1 cells, transport activity assays, homology threading structural modeling\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — systematic topology mapping with 13 insertion positions and functional validation, single rigorous study\",\n      \"pmids\": [\"19621945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Nramp2/DMT1 is recruited to the phagosomal membrane of macrophages (RAW264.7) and Sertoli cells after phagocytosis, associating with LAMP1-, cathepsin D-, and rab7-positive mature phagosomes, suggesting DMT1 transports divalent metals out of the phagosomal lumen, analogous to Nramp1.\",\n      \"method\": \"Immunofluorescence, in vitro biochemical studies with purified latex bead-containing phagosomes, erythrocyte and sperm phagocytosis assays\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct localization by biochemical fractionation and immunofluorescence, single lab, no functional transport measurement at phagosome\",\n      \"pmids\": [\"12239176\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"DMT1 is localized intracellularly (not at plasma membranes) in the adult rat testis, expressed in both Sertoli and germ cells in a stage-dependent manner during the spermatogenic cycle, suggesting a role in intracellular iron handling between compartments rather than transepithelial iron transport.\",\n      \"method\": \"Northern blot, RT-PCR, immunoblotting, immunohistochemistry of developing and adult rat testis\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct localization with multiple methods but no functional transport measurement; single lab\",\n      \"pmids\": [\"15355847\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"In rat kidney, DMT1 immunoreactivity is strongest in collecting ducts (both principal and intercalated cells) and distal convoluted tubules (apical staining), with intracellular staining throughout the nephron, consistent with DMT1 providing the molecular mechanism for apical iron entry in the distal nephron.\",\n      \"method\": \"Affinity-purified anti-DMT1 antibody, Western analysis, immunofluorescence, confocal microscopy in rat kidney sections\",\n      \"journal\": \"American journal of physiology. Renal physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct localization with multiple techniques, single lab, functional inference from localization\",\n      \"pmids\": [\"11292622\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"DMT1 is expressed in human term placenta syncytiotrophoblast, localizing to both the cytoplasm and the basal (fetal-side) membrane, distinct from transferrin receptor which is on the apical (maternal) side, suggesting DMT1 mediates iron transfer from endosomes to cytoplasm and across the basal membrane to the fetus.\",\n      \"method\": \"Immunohistochemistry of frozen term human placenta sections, double staining with anti-TfR antibody\",\n      \"journal\": \"Placenta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct immunolocalization in human tissue, single lab, functional inference from localization without transport assay\",\n      \"pmids\": [\"11095929\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Overexpression of DMT1 in CHO cells greatly increases ferrous iron uptake, with Fe(II) transported far more efficiently than Fe(III). Fe(III) transport by DMT1-expressing CHO cells can be inhibited by a membrane-impermeant oxidant, indicating that a membrane ferric reductase is needed to reduce Fe(III) to Fe(II) for DMT1-mediated transport.\",\n      \"method\": \"59Fe transport assays in Nramp2-transfected vs. control CHO cells, oxidant inhibition experiments\",\n      \"journal\": \"Experimental hematology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional transport assay with mechanistic pharmacological dissection, single lab\",\n      \"pmids\": [\"18722041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The N491S mutation in human SLC11A2 causes abnormal protein trafficking (as demonstrated in HuH7 hepatic cells with dsRed2-tagged DMT1), while the G212V mutation does not affect trafficking; N491S together with G212V leads to microcytic anemia and liver iron overload in a patient.\",\n      \"method\": \"Fluorescent protein tagging and live-cell imaging of DMT1 trafficking in HuH7 cells, splicing analysis in patient leukocytes, real-time qPCR of DMT1 isoforms in human liver\",\n      \"journal\": \"Blood cells, molecules & diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct trafficking assay with fluorescent fusion protein in human cell line, single lab\",\n      \"pmids\": [\"21871825\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"The E399D mutation in DMT1 exon 12 does not affect protein stability, membrane targeting, endosomal trafficking, or transport activity in LLC-PK1 cells, establishing it as a functionally neutral polymorphism and indicating that disease in the patient bearing the 1285G>C mutation is caused by exon 12 skipping (reduced protein quantity) rather than the E399D amino acid change.\",\n      \"method\": \"Site-directed mutagenesis (E399D, E399Q, E399A) stably expressed in LLC-PK1 cells, transport assays, immunofluorescence\",\n      \"journal\": \"Blood cells, molecules & diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro mutagenesis with functional and localization characterization; single lab negative-result finding\",\n      \"pmids\": [\"16023393\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Calcium reduces DMT1 protein expression at the apical cell membrane (not total cellular DMT1), as shown in fractionated Caco-2 cell lysates, suggesting that calcium inhibits non-heme iron absorption by decreasing DMT1 at the apical surface.\",\n      \"method\": \"Fractionation of Caco-2 cell membrane vs. whole cell lysates, Western blotting for DMT1 and ferroportin after iron and calcium treatments\",\n      \"journal\": \"Journal of agricultural and food chemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, fractionation-based localization without direct transport measurement or confirmation of functional consequence\",\n      \"pmids\": [\"20597505\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"A single reciprocal mutation I144F in TM2 of DCT1/SLC11A2 abolishes metal ion transport and increases proton slip currents; a double mutant I144F/F227I restores uptake activity and reduces slip currents, demonstrating that TM2 and TM4 are functionally coupled in the proton-metal ion coupling mechanism.\",\n      \"method\": \"Site-directed mutagenesis, metal ion uptake assays, Xenopus oocyte electrophysiology\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — mutagenesis with both functional and electrophysiological characterization revealing mechanistic inter-TM coupling\",\n      \"pmids\": [\"17980698\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"A non-competitive inhibitor (pyrimidinone 8, Ki ~20 μM) of human DMT1 was discovered that does not affect cell surface expression of hDMT1, providing the first experimental evidence that DMT1 can be allosterically modulated by pharmacological agents.\",\n      \"method\": \"Ligand-based virtual screening, radiolabeled iron uptake assay in hDMT1-expressing cells, surface expression analysis\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional transport inhibition assay with surface expression control; single lab, allosteric mechanism inferred from non-competitive kinetics\",\n      \"pmids\": [\"26047847\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Microglial-specific knockdown of Slc11a2 in male mice blunts LPS-induced pro-inflammatory cytokine expression (Il6, Tnfα, Il1β), reduces plasma cytokines, upregulates iron export/recycling genes, and improves acute sickness behavior in a sex-specific manner (males but not females), establishing a feed-forward link between microglial iron import via DMT1 and pro-inflammatory activation in vivo.\",\n      \"method\": \"Tamoxifen-inducible Cx3cr1Cre-ERT2 microglial-specific Slc11a2 knockdown mice, LPS challenge, plasma cytokine measurement, bulk RNA-seq of isolated microglia\",\n      \"journal\": \"Brain, behavior, and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo microglial-specific knockdown with behavioral and transcriptomic readouts; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"38141840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The G75R mutation in SLC11A2 causes improper DMT1 accumulation in lysosomes in HuTu 80 cells, leading to significantly decreased DMT1 protein levels in patient-derived lymphoblastoid cell lines, thus producing loss-of-function microcytic anemia with iron overload.\",\n      \"method\": \"Functional characterization of G75R in HuTu 80 cells by immunofluorescence colocalization with lysosomal markers; patient-derived LCL DMT1 protein quantification\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct localization in transfected cells with patient validation; single lab\",\n      \"pmids\": [\"35457224\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SLC11A2 (DMT1/Nramp2/DCT1) is a 12-transmembrane-domain, heavily glycosylated integral membrane protein that functions as a proton-coupled divalent metal (Fe2+, Mn2+, Co2+, Cd2+) transporter: it mediates apical uptake of dietary non-heme iron at the duodenal brush border (isoform I/+IRE, which recycles through lysosomes) and transports Fe2+ out of acidified recycling endosomes into the cytoplasm during the transferrin cycle in most other cells (isoform II/-IRE, which internalizes via clathrin/dynamin and recycles back to the plasma membrane via a PI3K-dependent pathway); transport is driven by the proton electrochemical gradient, with conserved residues in TM1/TM4/TM7 essential for cation transport and His267/His272 in TM6 regulating pH-dependent coupling rather than direct metal binding; the G185R mutation found in mk mice and Belgrade rats disrupts both transport function and correct apical membrane targeting; the carboxyl-terminal YLLNT motif of isoform II is required for internalization and endosomal recycling; and DMT1 is also recruited to phagosomal membranes in macrophages, expressed in microglia where iron import feeds inflammatory signaling, and essential for erythropoiesis in vivo.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SLC11A2 (DMT1/Nramp2/DCT1) is a 12-transmembrane-domain, heavily glycosylated integral membrane protein that functions as a proton-coupled divalent metal transporter and is the principal route for cellular acquisition of non-heme iron, with loss-of-function disrupting both dietary iron absorption and erythroid iron utilization [#0, #1, #21]. It transports Fe2+ (preferentially over Fe3+, which requires prior reduction by a membrane ferric reductase) as well as Mn2+, Co2+, and Cd2+ into the labile iron pool, driven by the proton electrochemical gradient with attendant intracellular acidification [#8, #16, #26]. Transport mechanism has been mapped to conserved residues: negatively charged residues in TM1/TM4/TM7 and a first-extracellular-loop region (G119, D124, Q126) govern cation transport and metal specificity, His267/His272 in TM6 regulate proton coupling rather than directly binding metal, and coupling efficiency reflects a non-obligatory proton-slippage mechanism in which TM2 and TM4 are functionally coupled (F227I, I144F) [#10, #16, #17, #30]. DMT1 is generated as multiple isoforms through alternative 5' (exon 1A) and 3' (IRE/non-IRE) usage that direct tissue-specific iron regulation and distinct subcellular trafficking [#9, #19]. At the duodenal brush border it mediates apical uptake of dietary iron and is upregulated under iron deprivation (isoform I) [#4], whereas in erythroid and other cells isoform II colocalizes and traffics in parallel with the transferrin receptor, cycling between the plasma membrane and acidified recycling endosomes to release endosomal Fe2+ into the cytoplasm during the transferrin cycle; its C-terminal YLLNT motif directs clathrin/dynamin-dependent internalization and PI3K-dependent recycling, and ablating it redirects DMT1 to lysosomes [#5, #11, #13, #18]. In vivo inactivation established DMT1 as essential for postnatal intestinal iron absorption and erythroid hemoglobin production but dispensable for materno-fetal iron transfer [#14], and human disease mutations that impair folding, trafficking, or expression (e.g. R416C, N491S, G75R) cause microcytic anemia with hepatic iron overload [#20, #27, #33]. Beyond canonical iron handling, DMT1 is recruited to mature macrophage phagosomes and supports microglial iron import that drives pro-inflammatory activation in vivo [#22, #32].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that SLC11A2/Nramp2 is itself an iron transporter whose loss causes systemic iron deficiency, answering whether a single gene links intestinal absorption and erythroid iron utilization.\",\n      \"evidence\": \"Positional cloning of the G185R mutation in mk mice and the Belgrade rat with functional transport assays in transfected cells\",\n      \"pmids\": [\"9241278\", \"9448300\", \"9731075\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"G185R conflates loss of transport with loss of membrane targeting\", \"did not resolve substrate range or the driving force for transport\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Demonstrated the transporter handles divalent cations beyond iron, framing it as a broad-specificity divalent metal transporter.\",\n      \"evidence\": \"Heterologous yeast smf1/smf2 double-null complementation with conserved-residue mutants\",\n      \"pmids\": [\"9360964\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"yeast assay does not quantify relative substrate selectivity in mammalian cells\", \"did not establish proton coupling directly\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Defined the proton-coupled, saturable transport of Fe2+/Co2+/Cd2+ into the cytoplasmic labile iron pool and fixed key topological features.\",\n      \"evidence\": \"Calcein fluorescence and 55Fe transport assays in stable CHO transfectants with surface biotinylation and ion-selectivity tests\",\n      \"pmids\": [\"10942769\", \"10625641\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"the molecular determinants of proton coupling were not yet mapped\", \"did not address physiological subcellular site of transport\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Resolved the iron-acquisition mechanism in the transferrin cycle, showing DMT1 isoform II cycles with the transferrin receptor through acidified recycling endosomes via defined trafficking pathways.\",\n      \"evidence\": \"pH-sensitive labeling, surface kinetics, pharmacological inhibition (dynasore, wortmannin) and dual-label confocal microscopy; complemented by erythroid mk/mk reticulocyte analysis\",\n      \"pmids\": [\"12724326\", \"11739192\", \"10049947\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"conflicting reports placed DMT1 in late endosomes/lysosomes versus recycling endosomes (#7)\", \"molecular adaptors for clathrin/PI3K-dependent steps not identified\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Mapped sequence determinants of trafficking, identifying the C-terminal YLLNT motif as the internalization/recycling signal and showing C-terminal splicing dictates the subcellular site of Fe2+ transport.\",\n      \"evidence\": \"Truncation and isoform-comparison mutants in LLC-PK1 cells with 125I-antibody surface kinetics and marker colocalization\",\n      \"pmids\": [\"16142913\", \"16475818\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"the trafficking machinery recognizing YLLNT was not identified\", \"isoform-specific transport rates in native tissue not measured\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Dissected the proton-metal coupling mechanism, showing coupling is non-obligatory proton slippage tunable by inter-helix interactions and gated by specific residues.\",\n      \"evidence\": \"Site-directed mutagenesis (His267/His272, TM1/TM4/TM7 residues, F227I, I144F, first-loop G119/D124/Q126) with Xenopus oocyte electrophysiology and uptake assays\",\n      \"pmids\": [\"12522007\", \"12954986\", \"15475345\", \"17980698\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"no atomic-resolution structure of the human transporter\", \"exact coordination geometry of bound metal not defined\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Provided a validated 12-TM topology with intracellular N/C termini and identified functionally critical insertion-sensitive regions, constraining structural models.\",\n      \"evidence\": \"Systematic HA-epitope insertion at 13 positions with permeabilized-cell immunofluorescence and homology threading\",\n      \"pmids\": [\"19621945\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"threading model not validated against an experimental structure\", \"conformational cycle during transport not resolved\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Established the physiological non-redundant roles in vivo, separating intestinal/erythroid requirement from dispensability in materno-fetal transfer and revealing an alternative hepatocyte iron-uptake route.\",\n      \"evidence\": \"Global and conditional Slc11a2 knockout mice with iron-absorption, hemoglobin, and tissue-iron phenotyping\",\n      \"pmids\": [\"15849611\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"the alternative iron-uptake mechanism in hepatocytes was not identified\", \"cell-autonomous roles in non-erythroid tissues left open\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Connected biochemical trafficking defects to human disease, showing folding/trafficking-disrupting mutations cause microcytic anemia with hepatic iron overload.\",\n      \"evidence\": \"Functional characterization of R416C, N491S, and G75R in human cell lines with patient-derived cell validation and splicing analysis\",\n      \"pmids\": [\"16584902\", \"21871825\", \"35457224\", \"16023393\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"single-lab functional assays for several variants\", \"genotype-phenotype severity relationships not systematically established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Extended DMT1 function beyond classical iron handling to immune cells, linking microglial iron import to pro-inflammatory activation in vivo.\",\n      \"evidence\": \"Tamoxifen-inducible microglial-specific Slc11a2 knockdown mice with LPS challenge, plasma cytokine measurement, and microglial RNA-seq; plus phagosomal recruitment in macrophages\",\n      \"pmids\": [\"38141840\", \"12239176\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"sex-specific effect (males only) mechanism not explained\", \"no direct measurement of transport at the phagosomal/microglial membrane\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How DMT1 is allosterically regulated and pharmacologically targeted, and the structural basis of its transport cycle, remain open.\",\n      \"evidence\": \"A non-competitive small-molecule inhibitor exists but the allosteric site and conformational mechanism are uncharacterized\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"no experimental structure of the human transporter\", \"allosteric modulatory site not defined\", \"endogenous regulators of trafficking unidentified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 8, 16, 26]},\n      {\"term_id\": \"GO:0140104\", \"supporting_discovery_ids\": [8, 10, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [4, 8, 11]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [5, 11, 18]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [7, 19, 33]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 8, 14]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [4, 14]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [22, 32]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"TFRC\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}