{"gene":"SLC20A1","run_date":"2026-06-10T07:46:32","timeline":{"discoveries":[{"year":1992,"finding":"GLVR1/SLC20A1 protein is homologous to pho-4+, a phosphate permease of Neurospora crassa, predicting that GLVR1 functions as a transport protein; it also serves as the cell-surface receptor for gibbon ape leukemia virus (GALV).","method":"Sequence homology analysis; functional expression in mouse cells conferring GALV susceptibility","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional receptor role established by heterologous expression; transport prediction based on homology, single lab","pmids":["1531369"],"is_preprint":false},{"year":1993,"finding":"Human GLVR1 residues 550–551, located in a cluster of seven positions differing between human and mouse proteins, are the critical determinants that allow GALV infection; substitution or hybrid constructs demonstrated these residues are necessary and sufficient for viral entry.","method":"Construction of human/mouse hybrid proteins and site-directed mutants; infection susceptibility assay in mouse cells","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct mutagenesis with functional readout (infection), multiple mutants tested, confirmed by rat sequence polymorphism","pmids":["8411375"],"is_preprint":false},{"year":1999,"finding":"The human GLVR1 gene consists of 11 exons over ~18 kb; its promoter contains a GC-rich region with two SP1 binding sites required for high promoter activity in osteoblast-like SaOS-2 cells, as shown by reporter gene assays.","method":"Gene cloning, 5'-RACE, reporter gene (promoter) assays in transiently transfected SaOS-2 cells","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assays with deletion analysis; single lab, single cell type","pmids":["9889306"],"is_preprint":false},{"year":2000,"finding":"TGF-β1 selectively increases sodium-dependent Pi transport and Glvr-1 (SLC20A1) mRNA expression in chondrogenic ATDC5 cells via a mechanism dependent on new RNA and protein synthesis; the response does not involve protein kinase C or MAPK (ERK/p38) pathways but likely involves Smad-dependent signaling.","method":"Northern blotting, radiolabeled Pi uptake assays, pharmacological inhibitors (PKC, ERK, p38 inhibitors), and Smad pathway analysis in ATDC5 cells","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (transport assay, Northern blot, pathway inhibitors); single lab","pmids":["10830313"],"is_preprint":false},{"year":2009,"finding":"Substituted cysteine accessibility mutagenesis (SCAM) of SLC20A1 in live cells revealed a revised topology of 12 transmembrane helices and 7 extracellular regions, superseding earlier 10-helix models, and identified extracellular regions accessible to the cell surface milieu.","method":"Substituted cysteine accessibility mutagenesis (SCAM); HMMTOP hidden Markov model-constrained topology prediction","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct biochemical topology mapping by SCAM mutagenesis with live-cell accessibility readout, multiple positions tested","pmids":["19717569"],"is_preprint":false},{"year":2009,"finding":"Inorganic phosphate (Pi) up-regulates Glvr-1 (SLC20A1) expression in MO6-G3 odontoblast-like cells via ERK1/2 signaling; this effect requires extracellular calcium and is blocked by the ERK inhibitor UO126.","method":"Real-time RT-PCR, ERK1/2 phosphorylation assays, calcium-free conditions, UO126 pharmacological inhibition","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods (RT-PCR, kinase inhibitors, Ca-free conditions); single lab","pmids":["19232318"],"is_preprint":false},{"year":2010,"finding":"Complete deletion of PiT1/SLC20A1 in mice causes embryonic lethality at E12.5 due to severely hypoplastic fetal livers with decreased proliferation and massive apoptosis, leading to reduced hematopoiesis and anemia; hematopoietic progenitors show no cell-autonomous proliferation/differentiation defect, placing the essential function in fetal liver stroma.","method":"Mouse knockout/hypomorphic allelic series; histology, FACS, colony assays, embryo analysis","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo genetic loss-of-function with allelic series, multiple phenotypic readouts and transplantation epistasis","pmids":["20161774"],"is_preprint":false},{"year":2010,"finding":"PiT1/SLC20A1 has a transport-independent role in protecting cells from TNF-induced apoptosis: PiT1-depleted cells show increased caspase-8 activation and sustained JNK activation in response to TNF; re-expression of a Pi-uptake-deficient PiT1 mutant rescues the apoptosis phenotype as effectively as wild-type PiT1.","method":"RNA interference in HeLa cells; PiT1 knockout MEFs; re-expression of transport-deficient PiT1 mutant; caspase-8 and JNK activity assays; JNK-specific inhibitor rescue","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — transport-deficient mutant rescue in KO cells demonstrates transport-independent mechanism; multiple orthogonal approaches (RNAi, KO MEFs, inhibitors, caspase assays)","pmids":["20817733"],"is_preprint":false},{"year":2013,"finding":"Conditional deletion of PiT1/SLC20A1 in bone marrow causes a profound block in terminal erythroid differentiation and severe B-cell lymphopenia (pro-B cell block) and mild neutropenia; the phenotype is hematopoietic-cell-intrinsic, associated with a cell-cycle progression defect, and occurs independently of changes in serum phosphate or cellular phosphate uptake.","method":"Conditional knockout mice; transplantation experiments; flow cytometry; cell-cycle analysis","journal":"Experimental hematology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo conditional KO with transplantation establishing cell-intrinsic requirement, multiple cell-type phenotypes, phosphate-uptake independence shown","pmids":["23376999"],"is_preprint":false},{"year":2013,"finding":"SLC20A1/PiT1 silencing reduces Pi-induced mineralization of valve interstitial cells (VICs) and prevents Pi-mediated Akt-1 downregulation and apoptosis; pharmacological block of Pi transport (phosphonoformic acid) or siRNA against SLC20A1 restores Akt-1 levels; overexpression of Akt-1 prevents Pi-induced apoptosis and mineralization, placing SLC20A1 upstream of Akt-1 in this pathway.","method":"siRNA knockdown in VIC cultures; phosphonoformic acid inhibition; Akt-1 overexpression; mitochondrial membrane potential and cytochrome c assays","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple approaches (siRNA, inhibitor, overexpression rescue) in same cellular system; single lab","pmids":["23308213"],"is_preprint":false},{"year":2017,"finding":"Pi-regulated heterodimerization of PiT1/SLC20A1 and PiT2/SLC20A2 mediates extracellular Pi sensing independently of Pi uptake: deletion of either PiT blunts Pi-dependent ERK1/2 phosphorylation; transport-deficient PiT mutants rescue ERK1/2 signaling; cross-linking and BRET show Pi-regulated low-abundance PiT1-PiT2 heterodimers; mutation of putative Pi-binding residues Ser-128 (PiT1) and Ser-113 (PiT2) abolishes Pi regulation of heterodimerization.","method":"Genetic deletion (siRNA/KO); Pi-dependent ERK1/2 phosphorylation assay; chemical cross-linking; bioluminescence resonance energy transfer (BRET); site-directed mutagenesis of Pi-binding residues","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with mutagenesis, BRET, cross-linking, and transport-deficient mutant rescue; multiple orthogonal methods in single rigorous study","pmids":["29233890"],"is_preprint":false},{"year":2018,"finding":"PiT1/SLC20A1 localizes to the endoplasmic reticulum (not the plasma membrane) in chondrocytes, co-localizing with ER marker ERp46; it binds the ER chaperone protein disulfide isomerase (PDI) and is required for PDI reductase activity; PiT1 ablation causes uncompensated ER stress (elevated Chop, Atf4, Bip), intracellular retention of aggrecan and VEGF-A, and chondrocyte death; a phosphate transport-deficient PiT1 mutant rescues ER stress and cargo retention, establishing a transport-independent ER homeostasis function.","method":"Conditional gene deletion in chondrocytes; immunofluorescence co-localization with ER markers; co-immunoprecipitation (PiT1-PDI interaction); PDI reductase activity assay; ER stress markers (RT-PCR/immunoblot); rescue with transport-deficient PiT1 mutant","journal":"Journal of bone and mineral research","confidence":"High","confidence_rationale":"Tier 1 / Strong — Co-IP of binding partner, functional enzyme assay, ER localization, transport-deficient mutant rescue; multiple orthogonal methods in single rigorous study","pmids":["30347511"],"is_preprint":false},{"year":2019,"finding":"PiT1/SLC20A1 has a novel transport-independent role in LPS-induced NF-κB signaling: PiT1-deficient macrophages show reduced IκB degradation, lower p65 nuclear translocation, and impaired MCP-1/IL-6 production upon LPS stimulation; ChIP assays show p65 directly binds the mPit1 promoter, and an NF-κB inhibitor abolishes LPS-induced PiT1 expression, establishing a positive feedback loop between PiT1 and NF-κB.","method":"PiT1 conditional knockout macrophages; ELISA for cytokines; immunoblot for IκB/p65; in vivo LPS challenge; promoter-reporter assay; chromatin immunoprecipitation (ChIP)","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo KO, in vitro mechanistic dissection, ChIP demonstrating direct p65 promoter binding; multiple orthogonal methods","pmids":["30755642"],"is_preprint":false},{"year":2022,"finding":"ESCRT machinery negatively regulates SLC20A1/PiT1 protein abundance post-transcriptionally in phosphate-replete cells: ESCRT deficiency increases SLC20A1 protein levels and phosphate uptake; SLC20A1 co-localizes with ESCRT components, suggesting direct ESCRT-mediated lysosomal degradation of SLC20A1.","method":"Genome-wide CRISPR loss-of-function screen; immunofluorescence co-localization; phosphate uptake assays in ESCRT-deficient cells","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide CRISPR screen plus functional validation (uptake assay, co-localization); single lab","pmids":["35447110"],"is_preprint":false},{"year":2023,"finding":"PiT1/SLC20A1 interacts with NPP1 in podocytes under hyperinsulinemic conditions; knockdown of SLC20A1 in podocytes under normal conditions induces insulin resistance manifested as loss of insulin signaling and inhibition of GLUT4-mediated glucose uptake, placing PiT1 as a required factor in NPP1-mediated insulin signaling.","method":"Co-immunoprecipitation (NPP1/PiT1 interaction); siRNA knockdown of SLC20A1; insulin signaling assays; glucose uptake measurement via GLUT4","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — co-IP for interaction plus functional knockdown with defined signaling readouts; single lab","pmids":["37269459"],"is_preprint":false},{"year":2024,"finding":"PiT1/SLC20A1 is the receptor for syncytin-B (SynB), the endogenous retroviral fusogen responsible for mouse syncytiotrophoblast layer II (ST-II) formation: cell-cell fusion assays with ORFeome screening identified PiT1 (but not PiT2/SLC20A2) as the SynB receptor; the interaction was confirmed by immunoprecipitation; PiT1 N-terminus is the major determinant for SynB-mediated fusion; PiT1 null embryos display absence of ST-II syncytialization, phenocopying SynB null placenta.","method":"Cell-cell fusion assay with ORFeome library screening; immunoprecipitation; PiT1/PiT2 chimera and truncation experiments; RT-qPCR expression analysis; electron microscopy of PiT1 null placenta","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution in fusion assay, Co-IP, domain-mapping mutagenesis, and in vivo KO phenotype confirming biological role; multiple orthogonal methods","pmids":["39287391"],"is_preprint":false},{"year":2024,"finding":"Slc20a1 (PiT-1) promotes synaptic plasticity in the hippocampus via a likely Otoferlin-dependent regulation of synaptic vesicle trafficking that impacts the GABAergic system; this role is distinct from and independent of its phosphate transport activity, as demonstrated by behavioral and electrophysiological analyses in conditional knockout mice.","method":"Conditional knockout mice; electrophysiology; behavioral analysis; molecular analysis of Otoferlin and GABAergic markers","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo conditional KO with electrophysiology and behavior; single lab; Otoferlin link mechanistically proposed but pathway not fully reconstituted","pmids":["38195526"],"is_preprint":false},{"year":2023,"finding":"Slc20a1/SLC20A1 is required for chorioallantoic placental morphogenesis: Slc20a1-/- embryos at E9.5 show reduced placenta size and structural abnormalities in the chorioallantois, with reduced MCT1+ syncytiotrophoblast coverage; SLC20A1 mediates sodium-dependent Pi symport into syncytiotrophoblast cells supporting their differentiation.","method":"Knockout mouse analysis; P33 phosphate uptake assays in BeWo cells; microarray, RT-PCR, RNA-seq expression profiling; immunohistochemistry of trophoblast markers","journal":"Vascular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO with structural phenotype and in vitro transport assay; single lab","pmids":["36795703"],"is_preprint":false},{"year":2020,"finding":"Simultaneous conditional deletion of both Pit1 and Pit2 in skeletal muscle causes fatal muscle atrophy by P13; single or partial deletions produce a gene-dose-dependent reduction in running activity associated with reduced ERK1/2 activation and stimulated AMP kinase in skeletal muscle, indicating Pi transport-dependent and ERK1/2-dependent metabolic Pi sensing pathways for myofiber function.","method":"Skeletal muscle conditional double knockout mice; grip strength and running activity assays; ERK1/2 and AMPK immunoblots; C2C12 oxygen consumption rate assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo conditional KO with functional and molecular readouts; single lab; Pit1-specific effects partially confounded by Pit2 redundancy","pmids":["32080237"],"is_preprint":false}],"current_model":"SLC20A1/PiT1 is a 12-transmembrane-helix, sodium-dependent inorganic phosphate cotransporter and GALV/syncytin-B receptor that functions beyond phosphate transport: it senses extracellular Pi through Pi-regulated PiT1–PiT2 heterodimerization to activate ERK1/2 signaling; it is post-transcriptionally regulated by ESCRT-mediated lysosomal degradation; it localizes to the ER in chondrocytes where it binds PDI to maintain ER homeostasis and chondrocyte survival; it protects against TNF-induced apoptosis via a JNK/caspase-8 pathway and participates in NF-κB–dependent inflammatory signaling—all in a phosphate-transport-independent manner—and in the brain it promotes hippocampal synaptic plasticity through an Otoferlin-dependent, GABAergic mechanism."},"narrative":{"mechanistic_narrative":"SLC20A1 (PiT1/GLVR1) is a multifunctional 12-transmembrane sodium-dependent inorganic phosphate cotransporter whose biological roles extend well beyond ion transport into cell survival, inflammation, development, and viral entry [PMID:19717569, PMID:20817733, PMID:39287391]. As a membrane transport protein it carries out Na-dependent Pi symport, and it serves as the cell-surface receptor for gibbon ape leukemia virus, with residues 550–551 forming the critical determinants of viral entry [PMID:1531369, PMID:8411375]. Beyond uptake, PiT1 acts as an extracellular phosphate sensor: Pi-regulated, low-abundance heterodimerization of PiT1 with PiT2/SLC20A2 — dependent on a putative Pi-binding residue Ser-128 — drives Pi-dependent ERK1/2 phosphorylation independently of phosphate transport [PMID:29233890]. Several of PiT1's functions are explicitly transport-independent, demonstrated by rescue with Pi-uptake-deficient mutants: it protects cells from TNF-induced apoptosis by restraining caspase-8 and sustained JNK activation [PMID:20817733], it localizes to the endoplasmic reticulum in chondrocytes where it binds protein disulfide isomerase, supports PDI reductase activity, and prevents ER stress and intracellular cargo retention to maintain chondrocyte survival [PMID:30347511], and it sustains LPS-induced NF-κB signaling in macrophages within a positive feedback loop in which p65 directly binds the Pit1 promoter [PMID:30755642]. In vivo, PiT1 is essential for fetal liver hematopoiesis and embryonic viability, and is cell-intrinsically required for terminal erythroid differentiation and B-cell development through control of cell-cycle progression, independent of systemic phosphate [PMID:20161774, PMID:23376999]. It is required for chorioallantoic placental morphogenesis and serves as the receptor for the endogenous retroviral fusogen syncytin-B that drives syncytiotrophoblast layer II formation [PMID:39287391, PMID:36795703]. PiT1 protein abundance is negatively controlled post-transcriptionally by the ESCRT machinery, consistent with ESCRT-mediated lysosomal degradation [PMID:35447110]. Additional roles include promotion of hippocampal synaptic plasticity via an Otoferlin-dependent GABAergic mechanism [PMID:38195526] and participation in Pi-induced mineralization and apoptosis of valve interstitial cells upstream of Akt-1 [PMID:23308213].","teleology":[{"year":1992,"claim":"Established the dual identity of GLVR1/SLC20A1 as both a predicted phosphate transport protein and the cell-surface receptor for gibbon ape leukemia virus, framing the protein's two original functional axes.","evidence":"Sequence homology to Neurospora pho-4+ phosphate permease and functional expression conferring GALV susceptibility in mouse cells","pmids":["1531369"],"confidence":"Medium","gaps":["Transport activity was predicted by homology, not directly measured","Did not define which protein regions mediate receptor versus transport functions"]},{"year":1993,"claim":"Mapped the structural determinant of viral entry, showing that residues 550–551 are necessary and sufficient for GALV infection and thereby localizing the receptor function to a defined extracellular determinant.","evidence":"Human/mouse hybrid proteins and site-directed mutants assayed for infection susceptibility, confirmed by rat sequence polymorphism","pmids":["8411375"],"confidence":"High","gaps":["Did not address whether the receptor function relates to phosphate transport","No structural model of the receptor-virus interface"]},{"year":1999,"claim":"Defined the transcriptional control of the gene, identifying SP1-dependent promoter activity in osteoblast-like cells and connecting SLC20A1 expression to bone/mineralizing tissue contexts.","evidence":"Gene cloning, 5'-RACE, and reporter promoter-deletion assays in SaOS-2 cells","pmids":["9889306"],"confidence":"Medium","gaps":["Single cell type; physiological relevance of SP1 sites not tested in vivo","Did not connect promoter regulation to functional output"]},{"year":2009,"claim":"Resolved the membrane architecture and defined the regulatory logic of phosphate-responsive expression, revising the topology to 12 transmembrane helices and showing Pi up-regulates SLC20A1 via ERK1/2 signaling.","evidence":"SCAM live-cell topology mapping; RT-PCR and ERK1/2 phosphorylation with UO126 inhibition and calcium-free conditions in odontoblast-like cells","pmids":["19717569","19232318"],"confidence":"High","gaps":["Topology mapping did not assign substrate-binding or dimerization residues","Did not establish whether ERK activation depends on transport"]},{"year":2010,"claim":"Separated PiT1's survival function from its transport activity and established its in vivo essentiality, showing transport-independent protection from TNF apoptosis and embryonic lethality from defective fetal liver hematopoiesis.","evidence":"RNAi/KO MEFs with transport-deficient mutant rescue and caspase-8/JNK assays; mouse knockout allelic series with embryo histology and colony assays","pmids":["20817733","20161774"],"confidence":"High","gaps":["Molecular mechanism by which PiT1 restrains caspase-8/JNK undefined","Direct partner mediating apoptosis protection not identified"]},{"year":2013,"claim":"Demonstrated a cell-intrinsic, phosphate-independent requirement for PiT1 in hematopoietic differentiation and positioned it upstream of Akt-1 in Pi-driven mineralization, broadening its roles in cell-cycle and survival control.","evidence":"Conditional KO mice with transplantation and cell-cycle analysis; siRNA, phosphonoformic acid inhibition and Akt-1 overexpression in valve interstitial cells","pmids":["23376999","23308213"],"confidence":"High","gaps":["Cell-cycle target of PiT1 in hematopoiesis not defined","Mechanism linking PiT1 to Akt-1 regulation unresolved"]},{"year":2017,"claim":"Defined PiT1 as a bona fide extracellular phosphate sensor, showing Pi-regulated PiT1–PiT2 heterodimerization drives ERK1/2 signaling independently of Pi uptake and identified candidate Pi-binding residues.","evidence":"Genetic deletion, Pi-dependent ERK1/2 assays, chemical cross-linking, BRET, and transport-deficient/Pi-binding-residue mutagenesis","pmids":["29233890"],"confidence":"High","gaps":["Downstream effectors linking heterodimer to ERK not identified","Structural basis of Pi sensing not resolved"]},{"year":2018,"claim":"Revealed an intracellular ER-resident function, showing PiT1 binds PDI and maintains ER homeostasis and chondrocyte survival in a transport-independent manner, a localization distinct from its plasma-membrane transporter role.","evidence":"Conditional chondrocyte deletion, ER-marker co-localization, PiT1-PDI co-IP, PDI reductase assay, ER stress markers, and transport-deficient mutant rescue","pmids":["30347511"],"confidence":"High","gaps":["How PiT1 traffics to/is retained in the ER unknown","Whether ER localization occurs outside chondrocytes untested"]},{"year":2019,"claim":"Connected PiT1 to innate immune signaling, establishing a transport-independent role in LPS-induced NF-κB activation and a positive feedback loop in which p65 directly drives Pit1 transcription.","evidence":"Conditional KO macrophages, cytokine ELISA, IκB/p65 immunoblots, in vivo LPS challenge, promoter-reporter and ChIP assays","pmids":["30755642"],"confidence":"High","gaps":["Molecular step at which PiT1 acts in the NF-κB cascade undefined","Direct PiT1 effector partner in macrophages not identified"]},{"year":2022,"claim":"Identified post-transcriptional control of PiT1 abundance, implicating ESCRT-mediated lysosomal degradation in setting phosphate uptake capacity in phosphate-replete cells.","evidence":"Genome-wide CRISPR loss-of-function screen with co-localization and phosphate uptake validation","pmids":["35447110"],"confidence":"Medium","gaps":["Direct ubiquitination/ESCRT recognition of SLC20A1 not biochemically demonstrated","Trigger coupling phosphate status to degradation unknown"]},{"year":2023,"claim":"Extended PiT1 function to placental development and metabolic signaling, showing a transport-dependent requirement for chorioallantoic morphogenesis and an NPP1-associated role in podocyte insulin signaling.","evidence":"Knockout mouse placental analysis with BeWo Pi uptake assays; NPP1/PiT1 co-IP and siRNA with insulin signaling and GLUT4 glucose-uptake assays in podocytes","pmids":["36795703","37269459"],"confidence":"Medium","gaps":["Podocyte NPP1-PiT1 interaction shown by single Co-IP without reciprocal validation","Whether placental requirement is transport-dependent versus a sensing/structural role not fully separated"]},{"year":2024,"claim":"Defined a developmental receptor function and a neuronal role, identifying PiT1 as the syncytin-B fusogen receptor for syncytiotrophoblast formation and as a promoter of hippocampal synaptic plasticity via an Otoferlin-dependent GABAergic mechanism.","evidence":"Cell-cell fusion ORFeome screening, immunoprecipitation, chimera/truncation mapping and in vivo KO placental EM; conditional KO mice with electrophysiology, behavior, and Otoferlin/GABAergic marker analysis","pmids":["39287391","38195526"],"confidence":"High","gaps":["Structural basis of PiT1–syncytin-B recognition beyond N-terminus mapping unknown","Otoferlin link in synaptic plasticity mechanistically proposed but pathway not reconstituted"]},{"year":null,"claim":"How PiT1 integrates its transport, sensing, ER-resident, and receptor functions through shared structural determinants — and what distinguishes its many transport-independent activities mechanistically — remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No high-resolution structure assigning transport, dimerization, and receptor surfaces","Direct effectors mediating transport-independent apoptosis, NF-κB, and ER functions not identified","Mechanistic basis of tissue-specific localization (plasma membrane vs ER) unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,3,13,17]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[0,1,15]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[10]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[11]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,1,4]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[11]}],"pathway":[{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,17]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[10,18]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[12]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[7,9]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[6,15,17]}],"complexes":[],"partners":["SLC20A2","PDI","NPP1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8WUM9","full_name":"Sodium-dependent phosphate transporter 1","aliases":["Gibbon ape leukemia virus receptor 1","GLVR-1","Leukemia virus receptor 1 homolog","Phosphate transporter 1","PiT-1","Solute carrier family 20 member 1"],"length_aa":679,"mass_kda":73.7,"function":"Sodium-phosphate symporter which preferentially transports the monovalent form of phosphate with a stoichiometry of two sodium ions per phosphate ion (PubMed:11009570, PubMed:16790504, PubMed:17494632, PubMed:19726692, PubMed:7929240, PubMed:8041748). May play a role in extracellular matrix and cartilage calcification as well as in vascular calcification (PubMed:11009570). Essential for cell proliferation but this function is independent of its phosphate transporter activity (PubMed:19726692) (Microbial infection) May function as a retroviral receptor as it confers human cells susceptibility to infection to Gibbon Ape Leukemia Virus (GaLV), Simian sarcoma-associated virus (SSAV) and Feline leukemia virus subgroup B (FeLV-B) as well as 10A1 murine leukemia virus (10A1 MLV)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q8WUM9/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SLC20A1","classification":"Not Classified","n_dependent_lines":212,"n_total_lines":1208,"dependency_fraction":0.17549668874172186},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/SLC20A1","total_profiled":1310},"omim":[{"mim_id":"615007","title":"BASAL GANGLIA CALCIFICATION, IDIOPATHIC, 4; IBGC4","url":"https://www.omim.org/entry/615007"},{"mim_id":"613394","title":"MICRO RNA 138-1; MIR138-1","url":"https://www.omim.org/entry/613394"},{"mim_id":"600057","title":"BLADDER EXSTROPHY AND EPISPADIAS COMPLEX; BEEC","url":"https://www.omim.org/entry/600057"},{"mim_id":"258040","title":"OEIS COMPLEX","url":"https://www.omim.org/entry/258040"},{"mim_id":"190040","title":"PLATELET-DERIVED GROWTH FACTOR, BETA POLYPEPTIDE; PDGFB","url":"https://www.omim.org/entry/190040"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Plasma membrane","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/SLC20A1"},"hgnc":{"alias_symbol":["PiT-1","Glvr-1","PiT1"],"prev_symbol":["GLVR1"]},"alphafold":{"accession":"Q8WUM9","domains":[{"cath_id":"-","chopping":"18-262_506-675","consensus_level":"medium","plddt":91.9915,"start":18,"end":675}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WUM9","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WUM9-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WUM9-F1-predicted_aligned_error_v6.png","plddt_mean":70.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SLC20A1","jax_strain_url":"https://www.jax.org/strain/search?query=SLC20A1"},"sequence":{"accession":"Q8WUM9","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8WUM9.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8WUM9/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WUM9"}},"corpus_meta":[{"pmid":"1531369","id":"PMC_1531369","title":"GLVR1, a receptor for gibbon ape leukemia virus, is homologous to a phosphate permease of Neurospora crassa and is expressed at high levels in the brain and thymus.","date":"1992","source":"Journal of virology","url":"https://pubmed.ncbi.nlm.nih.gov/1531369","citation_count":129,"is_preprint":false},{"pmid":"29233890","id":"PMC_29233890","title":"Phosphate (Pi)-regulated heterodimerization of the high-affinity sodium-dependent Pi transporters PiT1/Slc20a1 and PiT2/Slc20a2 underlies extracellular Pi sensing independently of Pi uptake.","date":"2017","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/29233890","citation_count":90,"is_preprint":false},{"pmid":"20161774","id":"PMC_20161774","title":"The phosphate transporter PiT1 (Slc20a1) revealed as a new essential gene for mouse liver development.","date":"2010","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/20161774","citation_count":87,"is_preprint":false},{"pmid":"9916777","id":"PMC_9916777","title":"In vivo expression of transcripts encoding the Glvr-1 phosphate transporter/retrovirus receptor during bone development.","date":"1999","source":"Bone","url":"https://pubmed.ncbi.nlm.nih.gov/9916777","citation_count":76,"is_preprint":false},{"pmid":"8411375","id":"PMC_8411375","title":"Definition of a domain of GLVR1 which is necessary for infection by gibbon ape leukemia virus and which is highly polymorphic between species.","date":"1993","source":"Journal of virology","url":"https://pubmed.ncbi.nlm.nih.gov/8411375","citation_count":67,"is_preprint":false},{"pmid":"10830313","id":"PMC_10830313","title":"Transforming growth factor-beta stimulates inorganic phosphate transport and expression of the type III phosphate transporter Glvr-1 in chondrogenic ATDC5 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journal of the American Society for Bone and Mineral Research","url":"https://pubmed.ncbi.nlm.nih.gov/30347511","citation_count":30,"is_preprint":false},{"pmid":"23785462","id":"PMC_23785462","title":"Mice with hypomorphic expression of the sodium-phosphate cotransporter PiT1/Slc20a1 have an unexpected normal bone mineralization.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23785462","citation_count":29,"is_preprint":false},{"pmid":"30755642","id":"PMC_30755642","title":"Novel function of PiT1/SLC20A1 in LPS-related inflammation and wound healing.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/30755642","citation_count":28,"is_preprint":false},{"pmid":"16531124","id":"PMC_16531124","title":"The Na+/PO4 cotransporter SLC20A1 gene labels distinct restricted subdomains of the developing pronephros in Xenopus and zebrafish embryos.","date":"2006","source":"Gene expression patterns : GEP","url":"https://pubmed.ncbi.nlm.nih.gov/16531124","citation_count":28,"is_preprint":false},{"pmid":"19232318","id":"PMC_19232318","title":"Inorganic phosphate regulates Glvr-1 and -2 expression: role of calcium and ERK1/2.","date":"2009","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/19232318","citation_count":27,"is_preprint":false},{"pmid":"27184385","id":"PMC_27184385","title":"Vitamin-D receptor agonist calcitriol reduces calcification in vitro through selective upregulation of SLC20A2 but not SLC20A1 or XPR1.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27184385","citation_count":27,"is_preprint":false},{"pmid":"19717569","id":"PMC_19717569","title":"New structural arrangement of the extracellular regions of the phosphate transporter SLC20A1, the receptor for gibbon ape leukemia virus.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19717569","citation_count":24,"is_preprint":false},{"pmid":"32850778","id":"PMC_32850778","title":"SLC20A1 Is Involved in Urinary Tract and Urorectal Development.","date":"2020","source":"Frontiers in cell and developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/32850778","citation_count":23,"is_preprint":false},{"pmid":"32080237","id":"PMC_32080237","title":"Slc20a1/Pit1 and Slc20a2/Pit2 are essential for normal skeletal myofiber function and survival.","date":"2020","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/32080237","citation_count":21,"is_preprint":false},{"pmid":"23376999","id":"PMC_23376999","title":"Mice lacking the sodium-dependent phosphate import protein, PiT1 (SLC20A1), have a severe defect in terminal erythroid differentiation and early B cell development.","date":"2013","source":"Experimental hematology","url":"https://pubmed.ncbi.nlm.nih.gov/23376999","citation_count":21,"is_preprint":false},{"pmid":"29261175","id":"PMC_29261175","title":"Identification of SLC20A1 and SLC15A4 among other genes as potential risk factors for combined pituitary hormone deficiency.","date":"2017","source":"Genetics in medicine : official journal of the American College of Medical Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/29261175","citation_count":20,"is_preprint":false},{"pmid":"31934214","id":"PMC_31934214","title":"LincRNA-SLC20A1 (SLC20A1) promotes extracellular matrix degradation in nucleus pulposus cells in human intervertebral disc degeneration by targeting the miR-31-5p/MMP3 axis.","date":"2019","source":"International journal of clinical and experimental pathology","url":"https://pubmed.ncbi.nlm.nih.gov/31934214","citation_count":19,"is_preprint":false},{"pmid":"33419798","id":"PMC_33419798","title":"High SLC20A1 Expression Is Associated With Poor Prognoses in Claudin-low and Basal-like Breast Cancers.","date":"2021","source":"Anticancer research","url":"https://pubmed.ncbi.nlm.nih.gov/33419798","citation_count":18,"is_preprint":false},{"pmid":"24880124","id":"PMC_24880124","title":"High levels of the type III inorganic phosphate transporter PiT1 (SLC20A1) can confer faster cell adhesion.","date":"2014","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/24880124","citation_count":16,"is_preprint":false},{"pmid":"31432167","id":"PMC_31432167","title":"Impact of SLC20A1 on the Wnt/β‑catenin signaling pathway in somatotroph adenomas.","date":"2019","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/31432167","citation_count":13,"is_preprint":false},{"pmid":"12231177","id":"PMC_12231177","title":"Overexpression of gibbon ape leukemia virus (GALV) receptor (GLVR1) on human CD34(+) cells increases gene transfer mediated by GALV pseudotyped vectors.","date":"2002","source":"Molecular therapy : the journal of the American Society of Gene Therapy","url":"https://pubmed.ncbi.nlm.nih.gov/12231177","citation_count":13,"is_preprint":false},{"pmid":"38195526","id":"PMC_38195526","title":"Slc20a1 and Slc20a2 regulate neuronal plasticity and cognition independently of their phosphate transport ability.","date":"2024","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/38195526","citation_count":12,"is_preprint":false},{"pmid":"9889306","id":"PMC_9889306","title":"Characterization of the human Glvr-1 phosphate transporter/retrovirus receptor gene and promoter region.","date":"1999","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/9889306","citation_count":11,"is_preprint":false},{"pmid":"35447110","id":"PMC_35447110","title":"Cellular abundance of sodium phosphate cotransporter SLC20A1/PiT1 and phosphate uptake are controlled post-transcriptionally by ESCRT.","date":"2022","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/35447110","citation_count":10,"is_preprint":false},{"pmid":"38941542","id":"PMC_38941542","title":"Spitz Melanoma With SLC20A1::ALK Fusion: A Novel Fusion Previously Undescribed in Spitz Melanocytic Neoplasm.","date":"2024","source":"The American Journal of dermatopathology","url":"https://pubmed.ncbi.nlm.nih.gov/38941542","citation_count":7,"is_preprint":false},{"pmid":"35605014","id":"PMC_35605014","title":"High expression of SLC20A1 is less effective for endocrine therapy and predicts late recurrence in ER-positive breast cancer.","date":"2022","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/35605014","citation_count":6,"is_preprint":false},{"pmid":"39287391","id":"PMC_39287391","title":"Sodium-dependent phosphate transporter PiT1/SLC20A1 as the receptor for the endogenous retroviral envelope syncytin-B involved in mouse placenta formation.","date":"2024","source":"Journal of virology","url":"https://pubmed.ncbi.nlm.nih.gov/39287391","citation_count":5,"is_preprint":false},{"pmid":"37286379","id":"PMC_37286379","title":"Computational analysis of sodium-dependent phosphate transporter SLC20A1/PiT1 gene identifies missense variations C573F, and T58A as high-risk deleterious SNPs.","date":"2023","source":"Journal of biomolecular structure & dynamics","url":"https://pubmed.ncbi.nlm.nih.gov/37286379","citation_count":5,"is_preprint":false},{"pmid":"31613887","id":"PMC_31613887","title":"Transgenic mouse model for conditional expression of influenza hemagglutinin-tagged human SLC20A1/PIT1.","date":"2019","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/31613887","citation_count":4,"is_preprint":false},{"pmid":"36795703","id":"PMC_36795703","title":"SLC20a1/PiT-1 is required for chorioallantoic placental morphogenesis.","date":"2023","source":"Vascular biology (Bristol, England)","url":"https://pubmed.ncbi.nlm.nih.gov/36795703","citation_count":3,"is_preprint":false},{"pmid":"35349375","id":"PMC_35349375","title":"Long Noncoding RNA SLC20A1-1 Induces Nucleus Pulposus Apoptosis by Sponging miR-146a-5p.","date":"2022","source":"Genetic testing and molecular biomarkers","url":"https://pubmed.ncbi.nlm.nih.gov/35349375","citation_count":2,"is_preprint":false},{"pmid":"21796222","id":"PMC_21796222","title":"Association between SLC20A1 and sodium-lithium countertransport.","date":"2011","source":"American journal of hypertension","url":"https://pubmed.ncbi.nlm.nih.gov/21796222","citation_count":2,"is_preprint":false},{"pmid":"37269459","id":"PMC_37269459","title":"Pit 1 transporter (SLC20A1) as a key factor in the NPP1-mediated inhibition of insulin signaling in human podocytes.","date":"2023","source":"Journal of cellular physiology","url":"https://pubmed.ncbi.nlm.nih.gov/37269459","citation_count":2,"is_preprint":false},{"pmid":"41222719","id":"PMC_41222719","title":"A matrix stiffness gene signature identifies SLC20A1 as a novel mechano-immunological checkpoint enabling synergistic immunotherapy in pancreatic ductal adenocarcinoma.","date":"2025","source":"Cancer immunology, immunotherapy : CII","url":"https://pubmed.ncbi.nlm.nih.gov/41222719","citation_count":0,"is_preprint":false},{"pmid":"41953013","id":"PMC_41953013","title":"Investigating the role of the TGF-β-SLC20A1 axis in the spatial heterogeneity of hepatocellular carcinoma through single-cell and spatial transcriptomics.","date":"2026","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/41953013","citation_count":0,"is_preprint":false},{"pmid":"41281711","id":"PMC_41281711","title":"SLC20A1 knockout to stably express a fusogenic gibbon ape leukemia virus envelope glycoprotein for lentiviral vector 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Methods & clinical development","url":"https://pubmed.ncbi.nlm.nih.gov/41281711","citation_count":0,"is_preprint":false},{"pmid":"41906789","id":"PMC_41906789","title":"Homozygous Loss-of-Function Variant in SLC20A1 Coding for Ubiquitous Phosphate Transporter PiT1 Is Associated With Multiple Developmental Abnormalities.","date":"2026","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/41906789","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":23414,"output_tokens":5084,"usd":0.073251,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13409,"output_tokens":4635,"usd":0.09146,"stage2_stop_reason":"end_turn"},"total_usd":0.164711,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1992,\n      \"finding\": \"GLVR1/SLC20A1 protein is homologous to pho-4+, a phosphate permease of Neurospora crassa, predicting that GLVR1 functions as a transport protein; it also serves as the cell-surface receptor for gibbon ape leukemia virus (GALV).\",\n      \"method\": \"Sequence homology analysis; functional expression in mouse cells conferring GALV susceptibility\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional receptor role established by heterologous expression; transport prediction based on homology, single lab\",\n      \"pmids\": [\"1531369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Human GLVR1 residues 550–551, located in a cluster of seven positions differing between human and mouse proteins, are the critical determinants that allow GALV infection; substitution or hybrid constructs demonstrated these residues are necessary and sufficient for viral entry.\",\n      \"method\": \"Construction of human/mouse hybrid proteins and site-directed mutants; infection susceptibility assay in mouse cells\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct mutagenesis with functional readout (infection), multiple mutants tested, confirmed by rat sequence polymorphism\",\n      \"pmids\": [\"8411375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"The human GLVR1 gene consists of 11 exons over ~18 kb; its promoter contains a GC-rich region with two SP1 binding sites required for high promoter activity in osteoblast-like SaOS-2 cells, as shown by reporter gene assays.\",\n      \"method\": \"Gene cloning, 5'-RACE, reporter gene (promoter) assays in transiently transfected SaOS-2 cells\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assays with deletion analysis; single lab, single cell type\",\n      \"pmids\": [\"9889306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"TGF-β1 selectively increases sodium-dependent Pi transport and Glvr-1 (SLC20A1) mRNA expression in chondrogenic ATDC5 cells via a mechanism dependent on new RNA and protein synthesis; the response does not involve protein kinase C or MAPK (ERK/p38) pathways but likely involves Smad-dependent signaling.\",\n      \"method\": \"Northern blotting, radiolabeled Pi uptake assays, pharmacological inhibitors (PKC, ERK, p38 inhibitors), and Smad pathway analysis in ATDC5 cells\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (transport assay, Northern blot, pathway inhibitors); single lab\",\n      \"pmids\": [\"10830313\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Substituted cysteine accessibility mutagenesis (SCAM) of SLC20A1 in live cells revealed a revised topology of 12 transmembrane helices and 7 extracellular regions, superseding earlier 10-helix models, and identified extracellular regions accessible to the cell surface milieu.\",\n      \"method\": \"Substituted cysteine accessibility mutagenesis (SCAM); HMMTOP hidden Markov model-constrained topology prediction\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct biochemical topology mapping by SCAM mutagenesis with live-cell accessibility readout, multiple positions tested\",\n      \"pmids\": [\"19717569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Inorganic phosphate (Pi) up-regulates Glvr-1 (SLC20A1) expression in MO6-G3 odontoblast-like cells via ERK1/2 signaling; this effect requires extracellular calcium and is blocked by the ERK inhibitor UO126.\",\n      \"method\": \"Real-time RT-PCR, ERK1/2 phosphorylation assays, calcium-free conditions, UO126 pharmacological inhibition\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods (RT-PCR, kinase inhibitors, Ca-free conditions); single lab\",\n      \"pmids\": [\"19232318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Complete deletion of PiT1/SLC20A1 in mice causes embryonic lethality at E12.5 due to severely hypoplastic fetal livers with decreased proliferation and massive apoptosis, leading to reduced hematopoiesis and anemia; hematopoietic progenitors show no cell-autonomous proliferation/differentiation defect, placing the essential function in fetal liver stroma.\",\n      \"method\": \"Mouse knockout/hypomorphic allelic series; histology, FACS, colony assays, embryo analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo genetic loss-of-function with allelic series, multiple phenotypic readouts and transplantation epistasis\",\n      \"pmids\": [\"20161774\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PiT1/SLC20A1 has a transport-independent role in protecting cells from TNF-induced apoptosis: PiT1-depleted cells show increased caspase-8 activation and sustained JNK activation in response to TNF; re-expression of a Pi-uptake-deficient PiT1 mutant rescues the apoptosis phenotype as effectively as wild-type PiT1.\",\n      \"method\": \"RNA interference in HeLa cells; PiT1 knockout MEFs; re-expression of transport-deficient PiT1 mutant; caspase-8 and JNK activity assays; JNK-specific inhibitor rescue\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — transport-deficient mutant rescue in KO cells demonstrates transport-independent mechanism; multiple orthogonal approaches (RNAi, KO MEFs, inhibitors, caspase assays)\",\n      \"pmids\": [\"20817733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Conditional deletion of PiT1/SLC20A1 in bone marrow causes a profound block in terminal erythroid differentiation and severe B-cell lymphopenia (pro-B cell block) and mild neutropenia; the phenotype is hematopoietic-cell-intrinsic, associated with a cell-cycle progression defect, and occurs independently of changes in serum phosphate or cellular phosphate uptake.\",\n      \"method\": \"Conditional knockout mice; transplantation experiments; flow cytometry; cell-cycle analysis\",\n      \"journal\": \"Experimental hematology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo conditional KO with transplantation establishing cell-intrinsic requirement, multiple cell-type phenotypes, phosphate-uptake independence shown\",\n      \"pmids\": [\"23376999\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SLC20A1/PiT1 silencing reduces Pi-induced mineralization of valve interstitial cells (VICs) and prevents Pi-mediated Akt-1 downregulation and apoptosis; pharmacological block of Pi transport (phosphonoformic acid) or siRNA against SLC20A1 restores Akt-1 levels; overexpression of Akt-1 prevents Pi-induced apoptosis and mineralization, placing SLC20A1 upstream of Akt-1 in this pathway.\",\n      \"method\": \"siRNA knockdown in VIC cultures; phosphonoformic acid inhibition; Akt-1 overexpression; mitochondrial membrane potential and cytochrome c assays\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple approaches (siRNA, inhibitor, overexpression rescue) in same cellular system; single lab\",\n      \"pmids\": [\"23308213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Pi-regulated heterodimerization of PiT1/SLC20A1 and PiT2/SLC20A2 mediates extracellular Pi sensing independently of Pi uptake: deletion of either PiT blunts Pi-dependent ERK1/2 phosphorylation; transport-deficient PiT mutants rescue ERK1/2 signaling; cross-linking and BRET show Pi-regulated low-abundance PiT1-PiT2 heterodimers; mutation of putative Pi-binding residues Ser-128 (PiT1) and Ser-113 (PiT2) abolishes Pi regulation of heterodimerization.\",\n      \"method\": \"Genetic deletion (siRNA/KO); Pi-dependent ERK1/2 phosphorylation assay; chemical cross-linking; bioluminescence resonance energy transfer (BRET); site-directed mutagenesis of Pi-binding residues\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with mutagenesis, BRET, cross-linking, and transport-deficient mutant rescue; multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"29233890\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PiT1/SLC20A1 localizes to the endoplasmic reticulum (not the plasma membrane) in chondrocytes, co-localizing with ER marker ERp46; it binds the ER chaperone protein disulfide isomerase (PDI) and is required for PDI reductase activity; PiT1 ablation causes uncompensated ER stress (elevated Chop, Atf4, Bip), intracellular retention of aggrecan and VEGF-A, and chondrocyte death; a phosphate transport-deficient PiT1 mutant rescues ER stress and cargo retention, establishing a transport-independent ER homeostasis function.\",\n      \"method\": \"Conditional gene deletion in chondrocytes; immunofluorescence co-localization with ER markers; co-immunoprecipitation (PiT1-PDI interaction); PDI reductase activity assay; ER stress markers (RT-PCR/immunoblot); rescue with transport-deficient PiT1 mutant\",\n      \"journal\": \"Journal of bone and mineral research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — Co-IP of binding partner, functional enzyme assay, ER localization, transport-deficient mutant rescue; multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"30347511\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PiT1/SLC20A1 has a novel transport-independent role in LPS-induced NF-κB signaling: PiT1-deficient macrophages show reduced IκB degradation, lower p65 nuclear translocation, and impaired MCP-1/IL-6 production upon LPS stimulation; ChIP assays show p65 directly binds the mPit1 promoter, and an NF-κB inhibitor abolishes LPS-induced PiT1 expression, establishing a positive feedback loop between PiT1 and NF-κB.\",\n      \"method\": \"PiT1 conditional knockout macrophages; ELISA for cytokines; immunoblot for IκB/p65; in vivo LPS challenge; promoter-reporter assay; chromatin immunoprecipitation (ChIP)\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo KO, in vitro mechanistic dissection, ChIP demonstrating direct p65 promoter binding; multiple orthogonal methods\",\n      \"pmids\": [\"30755642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ESCRT machinery negatively regulates SLC20A1/PiT1 protein abundance post-transcriptionally in phosphate-replete cells: ESCRT deficiency increases SLC20A1 protein levels and phosphate uptake; SLC20A1 co-localizes with ESCRT components, suggesting direct ESCRT-mediated lysosomal degradation of SLC20A1.\",\n      \"method\": \"Genome-wide CRISPR loss-of-function screen; immunofluorescence co-localization; phosphate uptake assays in ESCRT-deficient cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide CRISPR screen plus functional validation (uptake assay, co-localization); single lab\",\n      \"pmids\": [\"35447110\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PiT1/SLC20A1 interacts with NPP1 in podocytes under hyperinsulinemic conditions; knockdown of SLC20A1 in podocytes under normal conditions induces insulin resistance manifested as loss of insulin signaling and inhibition of GLUT4-mediated glucose uptake, placing PiT1 as a required factor in NPP1-mediated insulin signaling.\",\n      \"method\": \"Co-immunoprecipitation (NPP1/PiT1 interaction); siRNA knockdown of SLC20A1; insulin signaling assays; glucose uptake measurement via GLUT4\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — co-IP for interaction plus functional knockdown with defined signaling readouts; single lab\",\n      \"pmids\": [\"37269459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PiT1/SLC20A1 is the receptor for syncytin-B (SynB), the endogenous retroviral fusogen responsible for mouse syncytiotrophoblast layer II (ST-II) formation: cell-cell fusion assays with ORFeome screening identified PiT1 (but not PiT2/SLC20A2) as the SynB receptor; the interaction was confirmed by immunoprecipitation; PiT1 N-terminus is the major determinant for SynB-mediated fusion; PiT1 null embryos display absence of ST-II syncytialization, phenocopying SynB null placenta.\",\n      \"method\": \"Cell-cell fusion assay with ORFeome library screening; immunoprecipitation; PiT1/PiT2 chimera and truncation experiments; RT-qPCR expression analysis; electron microscopy of PiT1 null placenta\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution in fusion assay, Co-IP, domain-mapping mutagenesis, and in vivo KO phenotype confirming biological role; multiple orthogonal methods\",\n      \"pmids\": [\"39287391\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Slc20a1 (PiT-1) promotes synaptic plasticity in the hippocampus via a likely Otoferlin-dependent regulation of synaptic vesicle trafficking that impacts the GABAergic system; this role is distinct from and independent of its phosphate transport activity, as demonstrated by behavioral and electrophysiological analyses in conditional knockout mice.\",\n      \"method\": \"Conditional knockout mice; electrophysiology; behavioral analysis; molecular analysis of Otoferlin and GABAergic markers\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo conditional KO with electrophysiology and behavior; single lab; Otoferlin link mechanistically proposed but pathway not fully reconstituted\",\n      \"pmids\": [\"38195526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Slc20a1/SLC20A1 is required for chorioallantoic placental morphogenesis: Slc20a1-/- embryos at E9.5 show reduced placenta size and structural abnormalities in the chorioallantois, with reduced MCT1+ syncytiotrophoblast coverage; SLC20A1 mediates sodium-dependent Pi symport into syncytiotrophoblast cells supporting their differentiation.\",\n      \"method\": \"Knockout mouse analysis; P33 phosphate uptake assays in BeWo cells; microarray, RT-PCR, RNA-seq expression profiling; immunohistochemistry of trophoblast markers\",\n      \"journal\": \"Vascular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO with structural phenotype and in vitro transport assay; single lab\",\n      \"pmids\": [\"36795703\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Simultaneous conditional deletion of both Pit1 and Pit2 in skeletal muscle causes fatal muscle atrophy by P13; single or partial deletions produce a gene-dose-dependent reduction in running activity associated with reduced ERK1/2 activation and stimulated AMP kinase in skeletal muscle, indicating Pi transport-dependent and ERK1/2-dependent metabolic Pi sensing pathways for myofiber function.\",\n      \"method\": \"Skeletal muscle conditional double knockout mice; grip strength and running activity assays; ERK1/2 and AMPK immunoblots; C2C12 oxygen consumption rate assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo conditional KO with functional and molecular readouts; single lab; Pit1-specific effects partially confounded by Pit2 redundancy\",\n      \"pmids\": [\"32080237\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SLC20A1/PiT1 is a 12-transmembrane-helix, sodium-dependent inorganic phosphate cotransporter and GALV/syncytin-B receptor that functions beyond phosphate transport: it senses extracellular Pi through Pi-regulated PiT1–PiT2 heterodimerization to activate ERK1/2 signaling; it is post-transcriptionally regulated by ESCRT-mediated lysosomal degradation; it localizes to the ER in chondrocytes where it binds PDI to maintain ER homeostasis and chondrocyte survival; it protects against TNF-induced apoptosis via a JNK/caspase-8 pathway and participates in NF-κB–dependent inflammatory signaling—all in a phosphate-transport-independent manner—and in the brain it promotes hippocampal synaptic plasticity through an Otoferlin-dependent, GABAergic mechanism.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SLC20A1 (PiT1/GLVR1) is a multifunctional 12-transmembrane sodium-dependent inorganic phosphate cotransporter whose biological roles extend well beyond ion transport into cell survival, inflammation, development, and viral entry [#4, #7, #15]. As a membrane transport protein it carries out Na-dependent Pi symport, and it serves as the cell-surface receptor for gibbon ape leukemia virus, with residues 550–551 forming the critical determinants of viral entry [#0, #1]. Beyond uptake, PiT1 acts as an extracellular phosphate sensor: Pi-regulated, low-abundance heterodimerization of PiT1 with PiT2/SLC20A2 — dependent on a putative Pi-binding residue Ser-128 — drives Pi-dependent ERK1/2 phosphorylation independently of phosphate transport [#10]. Several of PiT1's functions are explicitly transport-independent, demonstrated by rescue with Pi-uptake-deficient mutants: it protects cells from TNF-induced apoptosis by restraining caspase-8 and sustained JNK activation [#7], it localizes to the endoplasmic reticulum in chondrocytes where it binds protein disulfide isomerase, supports PDI reductase activity, and prevents ER stress and intracellular cargo retention to maintain chondrocyte survival [#11], and it sustains LPS-induced NF-κB signaling in macrophages within a positive feedback loop in which p65 directly binds the Pit1 promoter [#12]. In vivo, PiT1 is essential for fetal liver hematopoiesis and embryonic viability, and is cell-intrinsically required for terminal erythroid differentiation and B-cell development through control of cell-cycle progression, independent of systemic phosphate [#6, #8]. It is required for chorioallantoic placental morphogenesis and serves as the receptor for the endogenous retroviral fusogen syncytin-B that drives syncytiotrophoblast layer II formation [#15, #17]. PiT1 protein abundance is negatively controlled post-transcriptionally by the ESCRT machinery, consistent with ESCRT-mediated lysosomal degradation [#13]. Additional roles include promotion of hippocampal synaptic plasticity via an Otoferlin-dependent GABAergic mechanism [#16] and participation in Pi-induced mineralization and apoptosis of valve interstitial cells upstream of Akt-1 [#9].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Established the dual identity of GLVR1/SLC20A1 as both a predicted phosphate transport protein and the cell-surface receptor for gibbon ape leukemia virus, framing the protein's two original functional axes.\",\n      \"evidence\": \"Sequence homology to Neurospora pho-4+ phosphate permease and functional expression conferring GALV susceptibility in mouse cells\",\n      \"pmids\": [\"1531369\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Transport activity was predicted by homology, not directly measured\", \"Did not define which protein regions mediate receptor versus transport functions\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Mapped the structural determinant of viral entry, showing that residues 550–551 are necessary and sufficient for GALV infection and thereby localizing the receptor function to a defined extracellular determinant.\",\n      \"evidence\": \"Human/mouse hybrid proteins and site-directed mutants assayed for infection susceptibility, confirmed by rat sequence polymorphism\",\n      \"pmids\": [\"8411375\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address whether the receptor function relates to phosphate transport\", \"No structural model of the receptor-virus interface\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Defined the transcriptional control of the gene, identifying SP1-dependent promoter activity in osteoblast-like cells and connecting SLC20A1 expression to bone/mineralizing tissue contexts.\",\n      \"evidence\": \"Gene cloning, 5'-RACE, and reporter promoter-deletion assays in SaOS-2 cells\",\n      \"pmids\": [\"9889306\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single cell type; physiological relevance of SP1 sites not tested in vivo\", \"Did not connect promoter regulation to functional output\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Resolved the membrane architecture and defined the regulatory logic of phosphate-responsive expression, revising the topology to 12 transmembrane helices and showing Pi up-regulates SLC20A1 via ERK1/2 signaling.\",\n      \"evidence\": \"SCAM live-cell topology mapping; RT-PCR and ERK1/2 phosphorylation with UO126 inhibition and calcium-free conditions in odontoblast-like cells\",\n      \"pmids\": [\"19717569\", \"19232318\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Topology mapping did not assign substrate-binding or dimerization residues\", \"Did not establish whether ERK activation depends on transport\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Separated PiT1's survival function from its transport activity and established its in vivo essentiality, showing transport-independent protection from TNF apoptosis and embryonic lethality from defective fetal liver hematopoiesis.\",\n      \"evidence\": \"RNAi/KO MEFs with transport-deficient mutant rescue and caspase-8/JNK assays; mouse knockout allelic series with embryo histology and colony assays\",\n      \"pmids\": [\"20817733\", \"20161774\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular mechanism by which PiT1 restrains caspase-8/JNK undefined\", \"Direct partner mediating apoptosis protection not identified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Demonstrated a cell-intrinsic, phosphate-independent requirement for PiT1 in hematopoietic differentiation and positioned it upstream of Akt-1 in Pi-driven mineralization, broadening its roles in cell-cycle and survival control.\",\n      \"evidence\": \"Conditional KO mice with transplantation and cell-cycle analysis; siRNA, phosphonoformic acid inhibition and Akt-1 overexpression in valve interstitial cells\",\n      \"pmids\": [\"23376999\", \"23308213\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-cycle target of PiT1 in hematopoiesis not defined\", \"Mechanism linking PiT1 to Akt-1 regulation unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Defined PiT1 as a bona fide extracellular phosphate sensor, showing Pi-regulated PiT1–PiT2 heterodimerization drives ERK1/2 signaling independently of Pi uptake and identified candidate Pi-binding residues.\",\n      \"evidence\": \"Genetic deletion, Pi-dependent ERK1/2 assays, chemical cross-linking, BRET, and transport-deficient/Pi-binding-residue mutagenesis\",\n      \"pmids\": [\"29233890\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream effectors linking heterodimer to ERK not identified\", \"Structural basis of Pi sensing not resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed an intracellular ER-resident function, showing PiT1 binds PDI and maintains ER homeostasis and chondrocyte survival in a transport-independent manner, a localization distinct from its plasma-membrane transporter role.\",\n      \"evidence\": \"Conditional chondrocyte deletion, ER-marker co-localization, PiT1-PDI co-IP, PDI reductase assay, ER stress markers, and transport-deficient mutant rescue\",\n      \"pmids\": [\"30347511\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PiT1 traffics to/is retained in the ER unknown\", \"Whether ER localization occurs outside chondrocytes untested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Connected PiT1 to innate immune signaling, establishing a transport-independent role in LPS-induced NF-κB activation and a positive feedback loop in which p65 directly drives Pit1 transcription.\",\n      \"evidence\": \"Conditional KO macrophages, cytokine ELISA, IκB/p65 immunoblots, in vivo LPS challenge, promoter-reporter and ChIP assays\",\n      \"pmids\": [\"30755642\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular step at which PiT1 acts in the NF-κB cascade undefined\", \"Direct PiT1 effector partner in macrophages not identified\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified post-transcriptional control of PiT1 abundance, implicating ESCRT-mediated lysosomal degradation in setting phosphate uptake capacity in phosphate-replete cells.\",\n      \"evidence\": \"Genome-wide CRISPR loss-of-function screen with co-localization and phosphate uptake validation\",\n      \"pmids\": [\"35447110\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitination/ESCRT recognition of SLC20A1 not biochemically demonstrated\", \"Trigger coupling phosphate status to degradation unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Extended PiT1 function to placental development and metabolic signaling, showing a transport-dependent requirement for chorioallantoic morphogenesis and an NPP1-associated role in podocyte insulin signaling.\",\n      \"evidence\": \"Knockout mouse placental analysis with BeWo Pi uptake assays; NPP1/PiT1 co-IP and siRNA with insulin signaling and GLUT4 glucose-uptake assays in podocytes\",\n      \"pmids\": [\"36795703\", \"37269459\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Podocyte NPP1-PiT1 interaction shown by single Co-IP without reciprocal validation\", \"Whether placental requirement is transport-dependent versus a sensing/structural role not fully separated\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined a developmental receptor function and a neuronal role, identifying PiT1 as the syncytin-B fusogen receptor for syncytiotrophoblast formation and as a promoter of hippocampal synaptic plasticity via an Otoferlin-dependent GABAergic mechanism.\",\n      \"evidence\": \"Cell-cell fusion ORFeome screening, immunoprecipitation, chimera/truncation mapping and in vivo KO placental EM; conditional KO mice with electrophysiology, behavior, and Otoferlin/GABAergic marker analysis\",\n      \"pmids\": [\"39287391\", \"38195526\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of PiT1–syncytin-B recognition beyond N-terminus mapping unknown\", \"Otoferlin link in synaptic plasticity mechanistically proposed but pathway not reconstituted\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PiT1 integrates its transport, sensing, ER-resident, and receptor functions through shared structural determinants — and what distinguishes its many transport-independent activities mechanistically — remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No high-resolution structure assigning transport, dimerization, and receptor surfaces\", \"Direct effectors mediating transport-independent apoptosis, NF-κB, and ER functions not identified\", \"Mechanistic basis of tissue-specific localization (plasma membrane vs ER) unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 3, 13, 17]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [0, 1, 15]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [10]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 1, 4]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 17]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [10, 18]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [12]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [7, 9]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [6, 15, 17]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"SLC20A2\", \"PDI\", \"NPP1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}