{"gene":"PTGFRN","run_date":"2026-04-28T19:45:45","timeline":{"discoveries":[{"year":2000,"finding":"PTGFRN (FPRP) associates specifically and at very high stoichiometry (~100%) with tetraspanins CD81 and CD9 at the cell surface, forming discrete complexes (<4×10^6 Da) that are distinct from integrin-containing CD81 complexes and remain intact after cholesterol-rich microdomain disruption by methyl-β-cyclodextrin.","method":"Immunoprecipitation, immunodepletion, gel permeation chromatography, methyl-β-cyclodextrin treatment","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP plus orthogonal biochemical methods, replicated across conditions","pmids":["11087758"],"is_preprint":false},{"year":1996,"finding":"PTGFRN (FPRP) acts as a negative regulator of the prostaglandin F2α receptor (FP): expression of FPRP cDNA in COS cells inhibits [3H]PGF2α binding to FP in a dose-dependent manner (up to ~80%), reducing apparent receptor number (not affinity), requiring co-expression in the same cell; molecular dissection identified two regions of FPRP involved in inhibition.","method":"Radioligand binding assay ([3H]PGF2α), Scatchard analysis, domain deletion/molecular dissection, transient transfection in COS cells","journal":"Prostaglandins, leukotrienes, and essential fatty acids","confidence":"High","confidence_rationale":"Tier 1 — in vitro binding assay with mutagenesis/domain dissection in same paper","pmids":["8804121"],"is_preprint":false},{"year":2006,"finding":"EWI-F (PTGFRN) directly interacts with ezrin-radixin-moesin (ERM) proteins via a basic charged amino acid stretch in its cytoplasmic domain, colocalizes with ERMs at microspikes, microvilli, and the uropod of polarized leukocytes; silencing EWI-F/EWI-2 augments cell migration and ERM phosphorylation, linking tetraspanin microdomains to the actin cytoskeleton.","method":"GST pulldown, protein-protein binding assay, co-immunoprecipitation, confocal microscopy, dominant-negative moesin transfection, siRNA knockdown","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — direct in vitro binding with GST fusion proteins plus in vivo co-IP and functional validation by DN-moesin and siRNA","pmids":["16690612"],"is_preprint":false},{"year":2009,"finding":"PTGFRN (CD9P-1/EWI-F) negatively regulates CD81-dependent Plasmodium yoelii hepatocyte infection: CD9P-1 silencing increases susceptibility to sporozoite infection, overexpression reduces it, and a CD9P-1 chimera that no longer associates with CD81 loses this regulatory effect, demonstrating the interaction with CD81 is required for the regulatory function.","method":"siRNA knockdown, overexpression, chimeric protein analysis, infection assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — gain- and loss-of-function with chimeric protein epistasis clearly mapping function to CD81 interaction","pmids":["19762465"],"is_preprint":false},{"year":2009,"finding":"PTGFRN (CD9P-1) forms cis-oligomers at the cell surface independently of its association with tetraspanins CD9 or CD81; however, expression levels of CD9 or CD81 positively modulate CD9P-1 oligomerization efficiency.","method":"In situ chemical cross-linking on living cells, affinity purification, LC-MS/MS, western blot with differentially tagged constructs","journal":"Journal of proteomics","confidence":"Medium","confidence_rationale":"Tier 2 — cross-linking plus MS plus tagged-protein validation in single lab","pmids":["19703604"],"is_preprint":false},{"year":2011,"finding":"PTGFRN (CD9P-1) is required for VEGF-dependent in vitro angiogenesis in human endothelial cells; knockdown inhibits capillary tube-like formation; a truncated form (GS-168AT2) corresponding to the CD9P-1/CD81 interaction sequence inhibits angiogenesis, endothelial migration, and depletes CD151, CD9, and CD9P-1 from the cell surface.","method":"siRNA knockdown, recombinant truncated protein treatment, co-precipitation, in vitro tube formation assay, in vivo xenograft tumor angiogenesis assay","journal":"British journal of cancer","confidence":"Medium","confidence_rationale":"Tier 2 — KD phenotype plus co-precipitation mapping interaction domain plus in vivo validation","pmids":["21863033"],"is_preprint":false},{"year":2011,"finding":"IFITM5 expression disrupts the FKBP11-CD81-[FPRP/CD9] complex by dissociating CD9, and this remodeling leads to increased expression of interferon-induced genes (Bst2, Irgm, Ifit3, B2m, MHC class I) in osteoblasts.","method":"Co-immunoprecipitation, gene expression analysis, transfection-based protein interaction network mapping","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP plus expression changes in single lab, one method type","pmids":["21600883"],"is_preprint":false},{"year":2020,"finding":"Cryo-EM structure of CD9 in complex with EWI-F (PTGFRN) reveals a tetrameric arrangement: two central EWI-F molecules dimerized through their ectodomains, flanked by two CD9 molecules each binding to one EWI-F transmembrane helix via CD9 helices h3 and h4; the complex adopts flexible arrangements suggesting a concatenation model for tetraspanin-enriched microdomain assembly.","method":"Cryo-EM structure determination, crystal structures of CD9 large extracellular loop with nanobodies","journal":"Life science alliance","confidence":"High","confidence_rationale":"Tier 1 — cryo-EM structural determination with crystallographic validation","pmids":["32958604"],"is_preprint":false},{"year":2019,"finding":"PTGFRN knockdown in glioblastoma cells reduces PI3K p110β protein stability and phosphorylated AKT levels, decreases nuclear p110β, impairs DNA damage sensing and repair, and radiosensitizes GBM cells.","method":"shRNA knockdown, western blot for p110β/pAKT, nuclear fractionation, DNA damage repair assays, functional knockdown screen","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 2 — KD with multiple pathway readouts in single lab","pmids":["31377205"],"is_preprint":false},{"year":2024,"finding":"PTGFRN directly binds Integrin β1 and E-Cadherin (identified as a novel direct binding partner); PTGFRN knockdown impacts autophagy; overexpression of PTGFRN increases and silencing decreases cancer cell proliferation, migration, colony formation, and spheroid growth.","method":"Co-immunoprecipitation, stable shRNA/cDNA transfection, proliferation/migration/colony assays, autophagy assays","journal":"Journal of cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP identifying binding partners plus functional KD/OE in single lab","pmids":["38924562"],"is_preprint":false},{"year":2024,"finding":"Co-immunoprecipitation proteomics of PTGFRN in A431 cells identifies association with proteins involved in protein processing/metabolism and VEGF signaling molecules; PTGFRN knockdown upregulates innate immune response pathways and downregulates metabolic precursor synthesis and protein processing pathways.","method":"Co-immunoprecipitation with anti-PTGFRN antibody, LC-MS/MS proteomics, shRNA knockdown proteomics","journal":"ACS omega","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP/MS interactome in single lab, moderate follow-up","pmids":["38559916"],"is_preprint":false},{"year":2025,"finding":"PTGFRN interacts with STAT3 and inhibits its degradation, leading to STAT3 accumulation, enhanced STAT3 binding to the BCAT1 gene promoter, increased BCAT1 expression, and elevated branched-chain amino acid (BCAA) metabolism in non-small cell lung cancer cells.","method":"Co-immunoprecipitation, ChIP (STAT3 binding to BCAT1 promoter), shRNA knockdown, western blot, metabolic assays","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — co-IP plus ChIP plus functional KD placing PTGFRN upstream of STAT3/BCAT1 axis in single lab","pmids":["41130302"],"is_preprint":false},{"year":2007,"finding":"PTGFRN (CD9P-1) carries N-linked glycans at all nine potential N-glycosylation sites and exists in at least 17 glycosylated isoforms at the cell surface; all isoforms associate with CD9.","method":"PNGase F deglycosylation, FTICR-MS, MALDI-TOF MS, ESI-MS/MS, GC-MS, 2-D PAGE, lectin blot, immunoprecipitation","journal":"Proteomics","confidence":"Medium","confidence_rationale":"Tier 1 — multiple orthogonal mass spectrometry methods establishing glycosylation sites and structures","pmids":["17960739"],"is_preprint":false},{"year":2021,"finding":"PTGFRN is internalized upon antibody (33B7) binding at the cancer cell surface, enabling antibody-drug conjugate delivery; PTGFRN-positive cells internalize the antibody while PTGFRN-negative cells do not.","method":"Flow cytometry, in vitro internalization assay, immunoprecipitation/MS for target identification, in vivo mouse xenograft","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — direct internalization assay with PTGFRN-positive vs negative cell comparison","pmids":["33503070"],"is_preprint":false}],"current_model":"PTGFRN (EWI-F/FPRP/CD9P-1) is a transmembrane Ig superfamily protein that forms highly stoichiometric complexes with tetraspanins CD9 and CD81—as revealed by cryo-EM structure showing a CD9–EWI-F tetramer—and connects tetraspanin-enriched microdomains to the actin cytoskeleton by directly binding ERM proteins through its cytoplasmic basic domain; it negatively regulates the prostaglandin F2α receptor (FP) by reducing available receptor number, inhibits CD81-dependent Plasmodium infection, forms cis-oligomers at the cell surface, directly binds Integrin β1 and E-Cadherin, stabilizes STAT3 protein to drive BCAT1-mediated BCAA metabolism, and supports PI3K p110β stability and AKT signaling to promote cell survival and DNA damage repair."},"narrative":{"teleology":[{"year":1996,"claim":"The first functional role assigned to PTGFRN was as a negative regulator of prostaglandin F2α receptor signaling, establishing that this Ig superfamily protein reduces available FP receptor number rather than affinity, with two discrete regions mediating inhibition.","evidence":"Radioligand binding assays with Scatchard analysis and domain deletion in COS cells","pmids":["8804121"],"confidence":"High","gaps":["Mechanism by which PTGFRN reduces FP receptor number (sequestration vs. degradation vs. trafficking) not determined","No in vivo validation of FP receptor regulation","Endogenous co-expression context not established"]},{"year":2000,"claim":"PTGFRN was shown to associate with tetraspanins CD9 and CD81 at near-complete stoichiometry, forming discrete low-molecular-weight complexes distinct from integrin-containing tetraspanin webs, establishing PTGFRN as a primary tetraspanin partner rather than a peripheral associate.","evidence":"Reciprocal co-IP, immunodepletion, gel permeation chromatography, and methyl-β-cyclodextrin treatment","pmids":["11087758"],"confidence":"High","gaps":["Structural basis of the tetraspanin interaction unknown at this stage","Functional consequence of the CD9/CD81 partnership not yet demonstrated"]},{"year":2006,"claim":"Discovery that PTGFRN bridges tetraspanin microdomains to the actin cytoskeleton by directly binding ERM proteins through its cytoplasmic basic domain resolved how tetraspanin complexes connect to cortical actin and established a mechanism by which PTGFRN restrains cell migration.","evidence":"GST pulldown, co-IP, confocal colocalization at microvilli/uropod, dominant-negative moesin and siRNA knockdown","pmids":["16690612"],"confidence":"High","gaps":["Which specific ERM family member is the dominant partner in vivo not resolved","Structural detail of the cytoplasmic interaction not determined"]},{"year":2007,"claim":"Comprehensive glycosylation mapping revealed that all nine potential N-glycosylation sites on PTGFRN are occupied, generating at least 17 glycoforms, establishing the protein as one of the most extensively glycosylated tetraspanin partners and raising questions about how glycan heterogeneity influences its interactions.","evidence":"PNGase F deglycosylation, FTICR-MS, MALDI-TOF, ESI-MS/MS, 2-D PAGE, lectin blot","pmids":["17960739"],"confidence":"Medium","gaps":["Functional significance of glycan diversity for CD9/CD81 binding or signaling not tested","Glycoform distribution across tissues unknown"]},{"year":2009,"claim":"Two studies revealed that PTGFRN forms cis-oligomers at the cell surface and that its interaction with CD81 is functionally required for inhibiting Plasmodium sporozoite infection of hepatocytes, moving PTGFRN from a structural scaffold to an active regulator of pathogen entry.","evidence":"Chemical cross-linking/LC-MS/MS for oligomerization; siRNA, overexpression, and CD81-binding-deficient chimera for infection regulation","pmids":["19703604","19762465"],"confidence":"High","gaps":["Whether oligomerization state modulates anti-parasitic function not tested","Mechanism of CD81-dependent Plasmodium entry inhibition (receptor masking vs. membrane organization) not resolved"]},{"year":2011,"claim":"PTGFRN was shown to be required for VEGF-dependent angiogenesis, and disruption of PTGFRN-CD81 association by IFITM5 remodeled tetraspanin complexes to activate interferon-induced gene expression, broadening PTGFRN's role to vascular biology and innate immune regulation.","evidence":"siRNA knockdown in endothelial tube formation assays; truncated protein treatment; co-IP of FKBP11-CD81-PTGFRN complex with IFITM5","pmids":["21863033","21600883"],"confidence":"Medium","gaps":["Direct mechanism linking PTGFRN to VEGFR signaling not identified","IFITM5-mediated complex remodeling studied only in osteoblasts"]},{"year":2019,"claim":"PTGFRN was found to stabilize PI3K p110β protein and sustain AKT phosphorylation, with knockdown impairing nuclear p110β localization, DNA damage sensing/repair, and radiosensitizing glioblastoma cells, connecting PTGFRN to survival signaling and genomic integrity.","evidence":"shRNA knockdown, western blot for p110β/pAKT, nuclear fractionation, DNA damage repair assays in GBM cells","pmids":["31377205"],"confidence":"Medium","gaps":["Whether PTGFRN directly binds p110β or acts indirectly through tetraspanin complexes not resolved","Mechanism of p110β stabilization (proteasomal, lysosomal) not defined","Single cancer type studied"]},{"year":2020,"claim":"Cryo-EM structure of the CD9–EWI-F complex revealed the precise architecture: an EWI-F ectodomain dimer flanked by two CD9 molecules contacting EWI-F transmembrane helices via CD9 helices h3/h4, providing the first atomic-level model for how tetraspanin-enriched microdomains are assembled through concatenation.","evidence":"Cryo-EM structure determination complemented by crystal structures of CD9 large extracellular loop with nanobodies","pmids":["32958604"],"confidence":"High","gaps":["Structure of the analogous CD81–EWI-F complex not determined","How ERM binding at the cytoplasmic face is coordinated with ectodomain dimerization unknown"]},{"year":2024,"claim":"PTGFRN's interactome was expanded to include direct binding to Integrin β1 and E-Cadherin, and proteomic profiling linked it to protein processing/metabolism and VEGF signaling networks, while its loss upregulated innate immune pathways.","evidence":"Co-IP, co-IP/LC-MS/MS proteomics, shRNA knockdown with proteomic and functional readouts in cancer cell lines","pmids":["38924562","38559916"],"confidence":"Medium","gaps":["Whether Integrin β1 and E-Cadherin bind PTGFRN independently of CD9/CD81 not determined","Autophagy regulation mechanism downstream of PTGFRN not elucidated"]},{"year":2025,"claim":"PTGFRN was placed upstream of a STAT3–BCAT1 metabolic axis: it stabilizes STAT3 protein, enhancing STAT3 occupancy on the BCAT1 promoter and driving branched-chain amino acid metabolism in NSCLC, extending PTGFRN's role to metabolic reprogramming in cancer.","evidence":"Co-IP, ChIP for STAT3 at BCAT1 promoter, shRNA knockdown, metabolic assays in NSCLC cells","pmids":["41130302"],"confidence":"Medium","gaps":["Direct vs. indirect nature of PTGFRN–STAT3 interaction not distinguished by structural or in vitro reconstitution methods","Whether STAT3 stabilization is a general PTGFRN function or cancer-specific is unknown"]},{"year":null,"claim":"Key unresolved questions include how PTGFRN's extensive glycosylation modulates its partner selectivity, the structural basis of the CD81–EWI-F complex, whether PTGFRN's roles in PI3K/AKT and STAT3 stabilization proceed through tetraspanin-dependent or -independent mechanisms, and how ERM-mediated cytoskeletal coupling is coordinated with ectodomain dimerization.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structure of CD81–PTGFRN complex","No reconstituted system distinguishing tetraspanin-dependent from -independent signaling","Functional relevance of 17 glycoforms untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,3,8,11]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[2]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,7]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,4,7,12,13]},{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[2]}],"pathway":[{"term_id":"GO:0005856","term_label":"cytoskeleton","supporting_discovery_ids":[2]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[1,8,11]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,6]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[9]}],"complexes":["CD9-EWI-F tetramer","FKBP11-CD81-PTGFRN-CD9 complex"],"partners":["CD9","CD81","EZR","RDX","MSN","ITGB1","CDH1","STAT3"],"other_free_text":[]},"mechanistic_narrative":"PTGFRN (EWI-F/CD9P-1/FPRP) is a heavily glycosylated transmembrane immunoglobulin superfamily protein that serves as a central organizer of tetraspanin-enriched microdomains, linking them to the actin cytoskeleton and modulating diverse signaling pathways at the cell surface. It forms near-stoichiometric complexes with tetraspanins CD9 and CD81 through transmembrane helix contacts, as demonstrated by cryo-EM, and these interactions are required for its regulatory functions including inhibition of CD81-dependent Plasmodium hepatocyte infection and modulation of VEGF-dependent angiogenesis [PMID:11087758, PMID:32958604, PMID:19762465, PMID:21863033]. PTGFRN connects tetraspanin microdomains to the cortical cytoskeleton by directly binding ERM proteins through a cytoplasmic basic domain, negatively regulating cell migration and ERM phosphorylation, and also directly interacts with Integrin β1, E-Cadherin, and STAT3 to influence adhesion, autophagy, and branched-chain amino acid metabolism [PMID:16690612, PMID:38924562, PMID:41130302]. Additionally, PTGFRN negatively regulates prostaglandin F2α receptor availability by reducing receptor number in a dose-dependent manner, and stabilizes PI3K p110β to sustain AKT signaling and DNA damage repair [PMID:8804121, PMID:31377205]."},"prefetch_data":{"uniprot":{"accession":"Q9P2B2","full_name":"Prostaglandin F2 receptor negative regulator","aliases":["CD9 partner 1","CD9P-1","Glu-Trp-Ile EWI motif-containing protein F","EWI-F","Prostaglandin F2-alpha receptor regulatory protein","Prostaglandin F2-alpha receptor-associated protein"],"length_aa":879,"mass_kda":98.6,"function":"Inhibits the binding of prostaglandin F2-alpha (PGF2-alpha) to its specific FP receptor, by decreasing the receptor number rather than the affinity constant. Functional coupling with the prostaglandin F2-alpha receptor seems to occur (By similarity). In myoblasts, associates with tetraspanins CD9 and CD81 to prevent myotube fusion during muscle regeneration (By similarity)","subcellular_location":"Endoplasmic reticulum membrane; Golgi apparatus, trans-Golgi network membrane","url":"https://www.uniprot.org/uniprotkb/Q9P2B2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PTGFRN","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CD81","stoichiometry":0.2},{"gene":"CD9","stoichiometry":0.2},{"gene":"SLC25A17","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PTGFRN","total_profiled":1310},"omim":[{"mim_id":"612875","title":"GONADOTROPIN-RELEASING HORMONE RECEPTOR 2; GNRHR2","url":"https://www.omim.org/entry/612875"},{"mim_id":"601204","title":"PROSTAGLANDIN F2 RECEPTOR NEGATIVE REGULATOR; PTGFRN","url":"https://www.omim.org/entry/601204"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PTGFRN"},"hgnc":{"alias_symbol":["FPRP","EWI-F","CD9P-1","FLJ11001","KIAA1436","SMAP-6","CD315"],"prev_symbol":[]},"alphafold":{"accession":"Q9P2B2","domains":[{"cath_id":"2.60.40.10","chopping":"21-142","consensus_level":"high","plddt":93.4602,"start":21,"end":142},{"cath_id":"2.60.40.10","chopping":"147-276","consensus_level":"high","plddt":90.7534,"start":147,"end":276},{"cath_id":"2.60.40.10","chopping":"280-401","consensus_level":"high","plddt":86.393,"start":280,"end":401},{"cath_id":"2.60.40.10","chopping":"410-542","consensus_level":"high","plddt":83.9335,"start":410,"end":542},{"cath_id":"2.60.40.10","chopping":"550-682","consensus_level":"high","plddt":80.9204,"start":550,"end":682},{"cath_id":"2.60.40.10","chopping":"690-826","consensus_level":"high","plddt":86.5188,"start":690,"end":826}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P2B2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P2B2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P2B2-F1-predicted_aligned_error_v6.png","plddt_mean":84.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PTGFRN","jax_strain_url":"https://www.jax.org/strain/search?query=PTGFRN"},"sequence":{"accession":"Q9P2B2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9P2B2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9P2B2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P2B2"}},"corpus_meta":[{"pmid":"16690612","id":"PMC_16690612","title":"EWI-2 and EWI-F link the tetraspanin web to the actin cytoskeleton through their direct association with ezrin-radixin-moesin proteins.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16690612","citation_count":165,"is_preprint":false},{"pmid":"11087758","id":"PMC_11087758","title":"FPRP, a major, highly stoichiometric, highly specific CD81- and CD9-associated protein.","date":"2000","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11087758","citation_count":118,"is_preprint":false},{"pmid":"21600883","id":"PMC_21600883","title":"Osteoblast-enriched membrane protein IFITM5 regulates the association of CD9 with an FKBP11-CD81-FPRP complex and stimulates expression of interferon-induced genes.","date":"2011","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/21600883","citation_count":40,"is_preprint":false},{"pmid":"17407154","id":"PMC_17407154","title":"The transferrin receptor and the tetraspanin web molecules CD9, CD81, and CD9P-1 are differentially sorted into exosomes after TPA treatment of K562 cells.","date":"2007","source":"Journal of cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17407154","citation_count":36,"is_preprint":false},{"pmid":"31377205","id":"PMC_31377205","title":"The Ig superfamily protein PTGFRN coordinates survival signaling in glioblastoma multiforme.","date":"2019","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/31377205","citation_count":28,"is_preprint":false},{"pmid":"32958604","id":"PMC_32958604","title":"Implications for tetraspanin-enriched microdomain assembly based on structures of CD9 with EWI-F.","date":"2020","source":"Life science alliance","url":"https://pubmed.ncbi.nlm.nih.gov/32958604","citation_count":28,"is_preprint":false},{"pmid":"8804121","id":"PMC_8804121","title":"Negative regulatory activity of a prostaglandin F2 alpha receptor associated protein (FPRP).","date":"1996","source":"Prostaglandins, leukotrienes, and essential fatty acids","url":"https://pubmed.ncbi.nlm.nih.gov/8804121","citation_count":27,"is_preprint":false},{"pmid":"35690717","id":"PMC_35690717","title":"Integrative analysis of cell adhesion molecules in glioblastoma identified prostaglandin F2 receptor inhibitor (PTGFRN) as an essential gene.","date":"2022","source":"BMC cancer","url":"https://pubmed.ncbi.nlm.nih.gov/35690717","citation_count":26,"is_preprint":false},{"pmid":"19762465","id":"PMC_19762465","title":"The Ig domain protein CD9P-1 down-regulates CD81 ability to support Plasmodium yoelii infection.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/19762465","citation_count":20,"is_preprint":false},{"pmid":"21863033","id":"PMC_21863033","title":"A truncated form of CD9-partner 1 (CD9P-1), GS-168AT2, potently inhibits in vivo tumour-induced angiogenesis and tumour growth.","date":"2011","source":"British journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/21863033","citation_count":20,"is_preprint":false},{"pmid":"21206492","id":"PMC_21206492","title":"CD9P-1 expression correlates with the metastatic status of lung cancer, and a truncated form of CD9P-1, GS-168AT2, inhibits in vivo tumour growth.","date":"2011","source":"British journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/21206492","citation_count":18,"is_preprint":false},{"pmid":"17960739","id":"PMC_17960739","title":"Glycosylation status of the membrane protein CD9P-1.","date":"2007","source":"Proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/17960739","citation_count":16,"is_preprint":false},{"pmid":"19703604","id":"PMC_19703604","title":"In situ chemical cross-linking on living cells reveals CD9P-1 cis-oligomer at cell surface.","date":"2009","source":"Journal of proteomics","url":"https://pubmed.ncbi.nlm.nih.gov/19703604","citation_count":16,"is_preprint":false},{"pmid":"27265091","id":"PMC_27265091","title":"The SDF-1 rs1801157 Polymorphism is Associated with Cancer Risk: An Update Pooled Analysis and FPRP Test of 17,876 Participants.","date":"2016","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/27265091","citation_count":15,"is_preprint":false},{"pmid":"26629098","id":"PMC_26629098","title":"The MIF -173G/C gene polymorphism increase gastrointestinal cancer and hematological malignancy risk: evidence from a meta-analysis and FPRP test.","date":"2015","source":"International journal of clinical and experimental medicine","url":"https://pubmed.ncbi.nlm.nih.gov/26629098","citation_count":11,"is_preprint":false},{"pmid":"27472712","id":"PMC_27472712","title":"The BTNL2 G16071A gene polymorphism increases granulomatous disease susceptibility: A meta-analysis including FPRP test of 8710 participants.","date":"2016","source":"Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27472712","citation_count":9,"is_preprint":false},{"pmid":"38559916","id":"PMC_38559916","title":"Effect of PTFGRN Expression on the Proteomic Profile of A431 Cells and Determination of the PTGFRN Interactome.","date":"2024","source":"ACS omega","url":"https://pubmed.ncbi.nlm.nih.gov/38559916","citation_count":7,"is_preprint":false},{"pmid":"33503070","id":"PMC_33503070","title":"Identification of Prostaglandin F2 Receptor Negative Regulator (PTGFRN) as an internalizable target in cancer cells for antibody-drug conjugate development.","date":"2021","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/33503070","citation_count":7,"is_preprint":false},{"pmid":"38924562","id":"PMC_38924562","title":"Prostaglandin F2 Receptor Negative Regulator (PTGFRN) Expression Correlates With a Metastatic-like Phenotype in Epidermoid Carcinoma, Pediatric Medulloblastoma, and Mesothelioma.","date":"2024","source":"Journal of cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/38924562","citation_count":5,"is_preprint":false},{"pmid":"40551322","id":"PMC_40551322","title":"8C7: A Fully Human Anti-PTGFRN Monoclonal Antibody-Drug Conjugate Inhibiting Tumour Growth of Mesothelioma and Paediatric Medulloblastoma Cell Lines.","date":"2025","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/40551322","citation_count":1,"is_preprint":false},{"pmid":"41130302","id":"PMC_41130302","title":"PTGFRN promotes non-small cell lung cancer malignant progression and reprograms BCAA metabolism by activating STAT3/BCAT1 pathway.","date":"2025","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/41130302","citation_count":1,"is_preprint":false},{"pmid":"41748870","id":"PMC_41748870","title":"Pan-cancer analysis reveals the oncogenic and immunomodulatory roles of PTGFRN across human cancers.","date":"2026","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/41748870","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":12945,"output_tokens":3322,"usd":0.044332},"stage2":{"model":"claude-opus-4-6","input_tokens":6767,"output_tokens":3081,"usd":0.16629},"total_usd":0.210622,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"PTGFRN (FPRP) associates specifically and at very high stoichiometry (~100%) with tetraspanins CD81 and CD9 at the cell surface, forming discrete complexes (<4×10^6 Da) that are distinct from integrin-containing CD81 complexes and remain intact after cholesterol-rich microdomain disruption by methyl-β-cyclodextrin.\",\n      \"method\": \"Immunoprecipitation, immunodepletion, gel permeation chromatography, methyl-β-cyclodextrin treatment\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP plus orthogonal biochemical methods, replicated across conditions\",\n      \"pmids\": [\"11087758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"PTGFRN (FPRP) acts as a negative regulator of the prostaglandin F2α receptor (FP): expression of FPRP cDNA in COS cells inhibits [3H]PGF2α binding to FP in a dose-dependent manner (up to ~80%), reducing apparent receptor number (not affinity), requiring co-expression in the same cell; molecular dissection identified two regions of FPRP involved in inhibition.\",\n      \"method\": \"Radioligand binding assay ([3H]PGF2α), Scatchard analysis, domain deletion/molecular dissection, transient transfection in COS cells\",\n      \"journal\": \"Prostaglandins, leukotrienes, and essential fatty acids\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro binding assay with mutagenesis/domain dissection in same paper\",\n      \"pmids\": [\"8804121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"EWI-F (PTGFRN) directly interacts with ezrin-radixin-moesin (ERM) proteins via a basic charged amino acid stretch in its cytoplasmic domain, colocalizes with ERMs at microspikes, microvilli, and the uropod of polarized leukocytes; silencing EWI-F/EWI-2 augments cell migration and ERM phosphorylation, linking tetraspanin microdomains to the actin cytoskeleton.\",\n      \"method\": \"GST pulldown, protein-protein binding assay, co-immunoprecipitation, confocal microscopy, dominant-negative moesin transfection, siRNA knockdown\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — direct in vitro binding with GST fusion proteins plus in vivo co-IP and functional validation by DN-moesin and siRNA\",\n      \"pmids\": [\"16690612\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PTGFRN (CD9P-1/EWI-F) negatively regulates CD81-dependent Plasmodium yoelii hepatocyte infection: CD9P-1 silencing increases susceptibility to sporozoite infection, overexpression reduces it, and a CD9P-1 chimera that no longer associates with CD81 loses this regulatory effect, demonstrating the interaction with CD81 is required for the regulatory function.\",\n      \"method\": \"siRNA knockdown, overexpression, chimeric protein analysis, infection assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — gain- and loss-of-function with chimeric protein epistasis clearly mapping function to CD81 interaction\",\n      \"pmids\": [\"19762465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PTGFRN (CD9P-1) forms cis-oligomers at the cell surface independently of its association with tetraspanins CD9 or CD81; however, expression levels of CD9 or CD81 positively modulate CD9P-1 oligomerization efficiency.\",\n      \"method\": \"In situ chemical cross-linking on living cells, affinity purification, LC-MS/MS, western blot with differentially tagged constructs\",\n      \"journal\": \"Journal of proteomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — cross-linking plus MS plus tagged-protein validation in single lab\",\n      \"pmids\": [\"19703604\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PTGFRN (CD9P-1) is required for VEGF-dependent in vitro angiogenesis in human endothelial cells; knockdown inhibits capillary tube-like formation; a truncated form (GS-168AT2) corresponding to the CD9P-1/CD81 interaction sequence inhibits angiogenesis, endothelial migration, and depletes CD151, CD9, and CD9P-1 from the cell surface.\",\n      \"method\": \"siRNA knockdown, recombinant truncated protein treatment, co-precipitation, in vitro tube formation assay, in vivo xenograft tumor angiogenesis assay\",\n      \"journal\": \"British journal of cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD phenotype plus co-precipitation mapping interaction domain plus in vivo validation\",\n      \"pmids\": [\"21863033\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"IFITM5 expression disrupts the FKBP11-CD81-[FPRP/CD9] complex by dissociating CD9, and this remodeling leads to increased expression of interferon-induced genes (Bst2, Irgm, Ifit3, B2m, MHC class I) in osteoblasts.\",\n      \"method\": \"Co-immunoprecipitation, gene expression analysis, transfection-based protein interaction network mapping\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP plus expression changes in single lab, one method type\",\n      \"pmids\": [\"21600883\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Cryo-EM structure of CD9 in complex with EWI-F (PTGFRN) reveals a tetrameric arrangement: two central EWI-F molecules dimerized through their ectodomains, flanked by two CD9 molecules each binding to one EWI-F transmembrane helix via CD9 helices h3 and h4; the complex adopts flexible arrangements suggesting a concatenation model for tetraspanin-enriched microdomain assembly.\",\n      \"method\": \"Cryo-EM structure determination, crystal structures of CD9 large extracellular loop with nanobodies\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — cryo-EM structural determination with crystallographic validation\",\n      \"pmids\": [\"32958604\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PTGFRN knockdown in glioblastoma cells reduces PI3K p110β protein stability and phosphorylated AKT levels, decreases nuclear p110β, impairs DNA damage sensing and repair, and radiosensitizes GBM cells.\",\n      \"method\": \"shRNA knockdown, western blot for p110β/pAKT, nuclear fractionation, DNA damage repair assays, functional knockdown screen\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD with multiple pathway readouts in single lab\",\n      \"pmids\": [\"31377205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PTGFRN directly binds Integrin β1 and E-Cadherin (identified as a novel direct binding partner); PTGFRN knockdown impacts autophagy; overexpression of PTGFRN increases and silencing decreases cancer cell proliferation, migration, colony formation, and spheroid growth.\",\n      \"method\": \"Co-immunoprecipitation, stable shRNA/cDNA transfection, proliferation/migration/colony assays, autophagy assays\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP identifying binding partners plus functional KD/OE in single lab\",\n      \"pmids\": [\"38924562\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Co-immunoprecipitation proteomics of PTGFRN in A431 cells identifies association with proteins involved in protein processing/metabolism and VEGF signaling molecules; PTGFRN knockdown upregulates innate immune response pathways and downregulates metabolic precursor synthesis and protein processing pathways.\",\n      \"method\": \"Co-immunoprecipitation with anti-PTGFRN antibody, LC-MS/MS proteomics, shRNA knockdown proteomics\",\n      \"journal\": \"ACS omega\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP/MS interactome in single lab, moderate follow-up\",\n      \"pmids\": [\"38559916\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PTGFRN interacts with STAT3 and inhibits its degradation, leading to STAT3 accumulation, enhanced STAT3 binding to the BCAT1 gene promoter, increased BCAT1 expression, and elevated branched-chain amino acid (BCAA) metabolism in non-small cell lung cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, ChIP (STAT3 binding to BCAT1 promoter), shRNA knockdown, western blot, metabolic assays\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — co-IP plus ChIP plus functional KD placing PTGFRN upstream of STAT3/BCAT1 axis in single lab\",\n      \"pmids\": [\"41130302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"PTGFRN (CD9P-1) carries N-linked glycans at all nine potential N-glycosylation sites and exists in at least 17 glycosylated isoforms at the cell surface; all isoforms associate with CD9.\",\n      \"method\": \"PNGase F deglycosylation, FTICR-MS, MALDI-TOF MS, ESI-MS/MS, GC-MS, 2-D PAGE, lectin blot, immunoprecipitation\",\n      \"journal\": \"Proteomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal mass spectrometry methods establishing glycosylation sites and structures\",\n      \"pmids\": [\"17960739\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PTGFRN is internalized upon antibody (33B7) binding at the cancer cell surface, enabling antibody-drug conjugate delivery; PTGFRN-positive cells internalize the antibody while PTGFRN-negative cells do not.\",\n      \"method\": \"Flow cytometry, in vitro internalization assay, immunoprecipitation/MS for target identification, in vivo mouse xenograft\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct internalization assay with PTGFRN-positive vs negative cell comparison\",\n      \"pmids\": [\"33503070\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTGFRN (EWI-F/FPRP/CD9P-1) is a transmembrane Ig superfamily protein that forms highly stoichiometric complexes with tetraspanins CD9 and CD81—as revealed by cryo-EM structure showing a CD9–EWI-F tetramer—and connects tetraspanin-enriched microdomains to the actin cytoskeleton by directly binding ERM proteins through its cytoplasmic basic domain; it negatively regulates the prostaglandin F2α receptor (FP) by reducing available receptor number, inhibits CD81-dependent Plasmodium infection, forms cis-oligomers at the cell surface, directly binds Integrin β1 and E-Cadherin, stabilizes STAT3 protein to drive BCAT1-mediated BCAA metabolism, and supports PI3K p110β stability and AKT signaling to promote cell survival and DNA damage repair.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PTGFRN (EWI-F/CD9P-1/FPRP) is a heavily glycosylated transmembrane immunoglobulin superfamily protein that serves as a central organizer of tetraspanin-enriched microdomains, linking them to the actin cytoskeleton and modulating diverse signaling pathways at the cell surface. It forms near-stoichiometric complexes with tetraspanins CD9 and CD81 through transmembrane helix contacts, as demonstrated by cryo-EM, and these interactions are required for its regulatory functions including inhibition of CD81-dependent Plasmodium hepatocyte infection and modulation of VEGF-dependent angiogenesis [PMID:11087758, PMID:32958604, PMID:19762465, PMID:21863033]. PTGFRN connects tetraspanin microdomains to the cortical cytoskeleton by directly binding ERM proteins through a cytoplasmic basic domain, negatively regulating cell migration and ERM phosphorylation, and also directly interacts with Integrin β1, E-Cadherin, and STAT3 to influence adhesion, autophagy, and branched-chain amino acid metabolism [PMID:16690612, PMID:38924562, PMID:41130302]. Additionally, PTGFRN negatively regulates prostaglandin F2α receptor availability by reducing receptor number in a dose-dependent manner, and stabilizes PI3K p110β to sustain AKT signaling and DNA damage repair [PMID:8804121, PMID:31377205].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"The first functional role assigned to PTGFRN was as a negative regulator of prostaglandin F2α receptor signaling, establishing that this Ig superfamily protein reduces available FP receptor number rather than affinity, with two discrete regions mediating inhibition.\",\n      \"evidence\": \"Radioligand binding assays with Scatchard analysis and domain deletion in COS cells\",\n      \"pmids\": [\"8804121\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which PTGFRN reduces FP receptor number (sequestration vs. degradation vs. trafficking) not determined\", \"No in vivo validation of FP receptor regulation\", \"Endogenous co-expression context not established\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"PTGFRN was shown to associate with tetraspanins CD9 and CD81 at near-complete stoichiometry, forming discrete low-molecular-weight complexes distinct from integrin-containing tetraspanin webs, establishing PTGFRN as a primary tetraspanin partner rather than a peripheral associate.\",\n      \"evidence\": \"Reciprocal co-IP, immunodepletion, gel permeation chromatography, and methyl-β-cyclodextrin treatment\",\n      \"pmids\": [\"11087758\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the tetraspanin interaction unknown at this stage\", \"Functional consequence of the CD9/CD81 partnership not yet demonstrated\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Discovery that PTGFRN bridges tetraspanin microdomains to the actin cytoskeleton by directly binding ERM proteins through its cytoplasmic basic domain resolved how tetraspanin complexes connect to cortical actin and established a mechanism by which PTGFRN restrains cell migration.\",\n      \"evidence\": \"GST pulldown, co-IP, confocal colocalization at microvilli/uropod, dominant-negative moesin and siRNA knockdown\",\n      \"pmids\": [\"16690612\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Which specific ERM family member is the dominant partner in vivo not resolved\", \"Structural detail of the cytoplasmic interaction not determined\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Comprehensive glycosylation mapping revealed that all nine potential N-glycosylation sites on PTGFRN are occupied, generating at least 17 glycoforms, establishing the protein as one of the most extensively glycosylated tetraspanin partners and raising questions about how glycan heterogeneity influences its interactions.\",\n      \"evidence\": \"PNGase F deglycosylation, FTICR-MS, MALDI-TOF, ESI-MS/MS, 2-D PAGE, lectin blot\",\n      \"pmids\": [\"17960739\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional significance of glycan diversity for CD9/CD81 binding or signaling not tested\", \"Glycoform distribution across tissues unknown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Two studies revealed that PTGFRN forms cis-oligomers at the cell surface and that its interaction with CD81 is functionally required for inhibiting Plasmodium sporozoite infection of hepatocytes, moving PTGFRN from a structural scaffold to an active regulator of pathogen entry.\",\n      \"evidence\": \"Chemical cross-linking/LC-MS/MS for oligomerization; siRNA, overexpression, and CD81-binding-deficient chimera for infection regulation\",\n      \"pmids\": [\"19703604\", \"19762465\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether oligomerization state modulates anti-parasitic function not tested\", \"Mechanism of CD81-dependent Plasmodium entry inhibition (receptor masking vs. membrane organization) not resolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"PTGFRN was shown to be required for VEGF-dependent angiogenesis, and disruption of PTGFRN-CD81 association by IFITM5 remodeled tetraspanin complexes to activate interferon-induced gene expression, broadening PTGFRN's role to vascular biology and innate immune regulation.\",\n      \"evidence\": \"siRNA knockdown in endothelial tube formation assays; truncated protein treatment; co-IP of FKBP11-CD81-PTGFRN complex with IFITM5\",\n      \"pmids\": [\"21863033\", \"21600883\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mechanism linking PTGFRN to VEGFR signaling not identified\", \"IFITM5-mediated complex remodeling studied only in osteoblasts\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"PTGFRN was found to stabilize PI3K p110β protein and sustain AKT phosphorylation, with knockdown impairing nuclear p110β localization, DNA damage sensing/repair, and radiosensitizing glioblastoma cells, connecting PTGFRN to survival signaling and genomic integrity.\",\n      \"evidence\": \"shRNA knockdown, western blot for p110β/pAKT, nuclear fractionation, DNA damage repair assays in GBM cells\",\n      \"pmids\": [\"31377205\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether PTGFRN directly binds p110β or acts indirectly through tetraspanin complexes not resolved\", \"Mechanism of p110β stabilization (proteasomal, lysosomal) not defined\", \"Single cancer type studied\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Cryo-EM structure of the CD9–EWI-F complex revealed the precise architecture: an EWI-F ectodomain dimer flanked by two CD9 molecules contacting EWI-F transmembrane helices via CD9 helices h3/h4, providing the first atomic-level model for how tetraspanin-enriched microdomains are assembled through concatenation.\",\n      \"evidence\": \"Cryo-EM structure determination complemented by crystal structures of CD9 large extracellular loop with nanobodies\",\n      \"pmids\": [\"32958604\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of the analogous CD81–EWI-F complex not determined\", \"How ERM binding at the cytoplasmic face is coordinated with ectodomain dimerization unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"PTGFRN's interactome was expanded to include direct binding to Integrin β1 and E-Cadherin, and proteomic profiling linked it to protein processing/metabolism and VEGF signaling networks, while its loss upregulated innate immune pathways.\",\n      \"evidence\": \"Co-IP, co-IP/LC-MS/MS proteomics, shRNA knockdown with proteomic and functional readouts in cancer cell lines\",\n      \"pmids\": [\"38924562\", \"38559916\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether Integrin β1 and E-Cadherin bind PTGFRN independently of CD9/CD81 not determined\", \"Autophagy regulation mechanism downstream of PTGFRN not elucidated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"PTGFRN was placed upstream of a STAT3–BCAT1 metabolic axis: it stabilizes STAT3 protein, enhancing STAT3 occupancy on the BCAT1 promoter and driving branched-chain amino acid metabolism in NSCLC, extending PTGFRN's role to metabolic reprogramming in cancer.\",\n      \"evidence\": \"Co-IP, ChIP for STAT3 at BCAT1 promoter, shRNA knockdown, metabolic assays in NSCLC cells\",\n      \"pmids\": [\"41130302\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs. indirect nature of PTGFRN–STAT3 interaction not distinguished by structural or in vitro reconstitution methods\", \"Whether STAT3 stabilization is a general PTGFRN function or cancer-specific is unknown\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include how PTGFRN's extensive glycosylation modulates its partner selectivity, the structural basis of the CD81–EWI-F complex, whether PTGFRN's roles in PI3K/AKT and STAT3 stabilization proceed through tetraspanin-dependent or -independent mechanisms, and how ERM-mediated cytoskeletal coupling is coordinated with ectodomain dimerization.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structure of CD81–PTGFRN complex\", \"No reconstituted system distinguishing tetraspanin-dependent from -independent signaling\", \"Functional relevance of 17 glycoforms untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 3, 8, 11]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 4, 7, 12, 13]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 8, 11]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 6]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"complexes\": [\n      \"CD9-EWI-F tetramer\",\n      \"FKBP11-CD81-PTGFRN-CD9 complex\"\n    ],\n    \"partners\": [\n      \"CD9\",\n      \"CD81\",\n      \"EZR\",\n      \"RDX\",\n      \"MSN\",\n      \"ITGB1\",\n      \"CDH1\",\n      \"STAT3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}