{"gene":"PITPNM3","run_date":"2026-06-10T06:43:35","timeline":{"discoveries":[{"year":2011,"finding":"PITPNM3 functions as a receptor for CCL18 on breast cancer cells; CCL18 binding to PITPNM3 triggers integrin clustering, enhances adherence to extracellular matrix, activates intracellular calcium signaling, and promotes invasion and metastasis. Suppression of PITPNM3 abrogates CCL18-induced invasion and metastasis in xenograft models.","method":"siRNA knockdown of PITPNM3, intracellular calcium signaling assay, integrin clustering assay, invasion assay, breast cancer xenograft mouse model","journal":"Cancer Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — receptor identification supported by multiple orthogonal methods (knockdown, calcium signaling, integrin assays, in vivo xenograft), replicated in subsequent studies","pmids":["21481794"],"is_preprint":false},{"year":2013,"finding":"CCL18 binding to PITPNM3 (Nir1) promotes phosphorylation of Akt, LIMK, and cofilin (facilitating actin polymerization), and stabilizes Snail via the PI3K/Akt/GSK3β signaling pathway, thereby inducing epithelial-mesenchymal transition (EMT) and breast cancer invasion. LY294002 (PI3K inhibitor) blocked lung metastasis in vivo.","method":"Western blot for phosphorylation, siRNA knockdown, in vivo lung metastasis model, PI3K inhibitor (LY294002) treatment","journal":"European Journal of Cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single lab, multiple downstream signaling readouts with pharmacological validation and in vivo confirmation","pmids":["24001613"],"is_preprint":false},{"year":2015,"finding":"CCL18 binding to PITPNM3 activates NF-κB signaling (phosphorylation of IKK and IκBα, p65 nuclear translocation) to promote hepatocellular carcinoma cell migration, invasion, and EMT. siRNA silencing of PITPNM3 abolished these effects in PITPNM3-positive HCC cells.","method":"siRNA knockdown of PITPNM3, Western blot for IKK/IκBα phosphorylation, p65 nuclear translocation assay, migration/invasion assay","journal":"Tumour Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single lab, multiple orthogonal methods (signaling, nuclear translocation, functional assays), genetic loss-of-function","pmids":["26449829"],"is_preprint":false},{"year":2016,"finding":"CCL18 binding to PITPNM3 (Nir1) in NSCLC cells modulates cytoskeleton reorganization via RAC1 activation in an ELMO1-dependent manner, and enhances cell adhesion by activating ELMO1-integrin β1 signaling.","method":"siRNA knockdown, RAC1 activation assay, ELMO1 co-signaling analysis, adhesion assay, invasion assay","journal":"Molecular Carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single lab, multiple downstream signaling readouts with genetic knockdown","pmids":["26756176"],"is_preprint":false},{"year":2007,"finding":"A missense mutation Q626H in the C-terminal PYK2-binding domain of PITPNM3 causes autosomal dominant cone dystrophy (CORD5), indicating that the interaction between PITPNM3 and PYK2 is important for its function in mammalian phototransduction.","method":"Genetic linkage refinement, direct sequencing of PITPNM3 in CORD5 families, mutation mapping to PYK2-interacting domain","journal":"European Journal of Human Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — disease-causing mutation mapped to functional domain in two independent families; domain-function inference without direct in vitro reconstitution","pmids":["17377520"],"is_preprint":false},{"year":2020,"finding":"CCL18 binding to PITPNM3 (NIR1) in oral squamous cell carcinoma cells activates the JAK2/STAT3 signaling pathway to promote cancer cell growth, metastasis, and EMT. Knockdown of NIR1 or treatment with JAK inhibitor AG490 blocked rCCL18-induced effects.","method":"siRNA knockdown of NIR1, Western blot for JAK2/STAT3 phosphorylation, pharmacological inhibition (AG490), proliferation/invasion/migration assays","journal":"BMC Cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — single lab, multiple orthogonal methods (genetic, pharmacological, functional assays)","pmids":["32641093"],"is_preprint":false},{"year":2022,"finding":"PITPNM3 (Nir1) constitutively localizes at ER-PM junctions and interacts with Nir2 via a region between the FFAT motif and the DDHD domain. Nir1 potentiates Nir2 targeting to ER-PM junctions during receptor-mediated signaling and is required for efficient plasma membrane PIP2 replenishment.","method":"Live-cell imaging (constitutive ER-PM junction localization), biochemical co-immunoprecipitation (Nir1-Nir2 interaction), domain-mapping analysis, PIP2 replenishment assay","journal":"Molecular Biology of the Cell","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — direct localization by live-cell imaging with functional consequence (PIP2 homeostasis), reciprocal interaction and domain mapping by biochemical assay, multiple orthogonal methods in one study","pmids":["35020418"],"is_preprint":false},{"year":2022,"finding":"In human microglial cells, CCL18-induced phagocytosis is mediated by CCR8 rather than PITPNM3; selective knockdown of CCR8 (not PITPNM3) blocked CCL18-induced phagocytosis through the NF-κB/Src signaling pathway. PITPNM3 knockdown did not affect microglial phagocytosis.","method":"siRNA selective knockdown of CCR8 vs PITPNM3, phagocytosis assay (amyloid-β and dextran uptake), Western blot for NF-κB/Src signaling","journal":"Journal of Interferon & Cytokine Research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, direct genetic knockdown comparing two receptors; negative result for PITPNM3 in this specific cell context is mechanistically informative","pmids":["35041514"],"is_preprint":false},{"year":2020,"finding":"Mfn-2 suppresses PITPNM3 expression by interacting with transcription factor SP1, thereby reducing SP1 binding to the PITPNM3 promoter. SP1 overexpression increases PITPNM3 mRNA and promotes tumor growth; Mfn-2 overexpression reverses these effects.","method":"Co-immunoprecipitation (Mfn-2/SP1 interaction), ChIP assay (SP1 binding to PITPNM3 promoter), RT-PCR for PITPNM3 mRNA, in vivo tumorigenicity assay in nude mice","journal":"Medical Science Monitor","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — single lab, Co-IP and ChIP used together with in vivo validation, but single study without independent replication","pmids":["31955176"],"is_preprint":false},{"year":2025,"finding":"The LNS2 domain of PITPNM3 (Nir1) binds phosphatidic acid (PA) and PIP2 in vitro (liposome binding assays), but only PA is necessary and sufficient for membrane localization in cells. This PILS-Nir1 domain functions as a sensitive PA biosensor in live cells.","method":"Liposome binding assay, live-cell fluorescence imaging of PILS-Nir1 biosensor, pharmacological and genetic manipulation in HEK293A cells","journal":"bioRxiv (preprint)","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro liposome binding and live-cell imaging with functional domain use; preprint, single study, not yet peer-reviewed","pmids":["38464273"],"is_preprint":true}],"current_model":"PITPNM3 is a membrane-associated phosphatidylinositol transfer protein that (1) constitutively localizes at ER-PM junctions where it promotes Nir2 recruitment and plasma membrane PIP2 homeostasis via interaction through a region between its FFAT motif and DDHD domain, (2) serves as a functional receptor for CCL18 that activates intracellular calcium signaling, integrin clustering, and downstream pathways (PI3K/Akt/GSK3β/Snail, NF-κB, JAK2/STAT3, ELMO1/RAC1) to drive cancer cell invasion and EMT, and (3) harbors a disease-causing mutation (Q626H) in its PYK2-binding domain that causes autosomal dominant cone dystrophy (CORD5), implicating PITPNM3–PYK2 interaction in photoreceptor maintenance."},"narrative":{"mechanistic_narrative":"PITPNM3 (Nir1) is a membrane-associated phosphatidylinositol-transfer protein that operates at ER–plasma membrane junctions and additionally functions as a signaling receptor for the chemokine CCL18 [PMID:35020418, PMID:21481794]. At ER–PM junctions, where it constitutively localizes, PITPNM3 binds Nir2 through a region between its FFAT motif and DDHD domain and potentiates Nir2 targeting during receptor-mediated signaling, an activity required for efficient replenishment of plasma membrane PIP2 [PMID:35020418]. Its LNS2 domain binds phosphatidic acid and PIP2 in vitro, with phosphatidic acid being necessary and sufficient for membrane localization [PMID:38464273]. As a CCL18 receptor on epithelial cancer cells, PITPNM3 engagement triggers integrin clustering, intracellular calcium signaling, and enhanced extracellular-matrix adherence, driving invasion and metastasis [PMID:21481794]; downstream of this receptor, CCL18 activates multiple effector cascades that converge on epithelial-mesenchymal transition and motility, including PI3K/Akt/GSK3β-dependent Snail stabilization and actin remodeling via LIMK/cofilin [PMID:24001613], NF-κB activation [PMID:26449829], ELMO1-dependent RAC1 and integrin β1 signaling [PMID:26756176], and JAK2/STAT3 signaling [PMID:32641093]. PITPNM3 expression is transcriptionally controlled by SP1, whose activity is suppressed by Mfn-2 [PMID:31955176]. A missense mutation (Q626H) in the C-terminal PYK2-binding domain of PITPNM3 causes autosomal dominant cone dystrophy (CORD5), linking the protein to photoreceptor maintenance [PMID:17377520].","teleology":[{"year":2007,"claim":"Established the first disease link for PITPNM3 by mapping a cone dystrophy mutation to its C-terminal PYK2-binding domain, implicating the protein in phototransduction.","evidence":"Genetic linkage refinement and direct sequencing in CORD5 families, with mutation mapped to the PYK2-interacting domain","pmids":["17377520"],"confidence":"Medium","gaps":["No in vitro reconstitution of the PITPNM3–PYK2 interaction","Mechanism of photoreceptor maintenance not defined","Functional consequence of Q626H on PYK2 binding not directly tested"]},{"year":2011,"claim":"Identified PITPNM3 as a functional receptor for CCL18, answering how this chemokine drives cancer cell invasion and metastasis.","evidence":"siRNA knockdown with calcium signaling, integrin clustering, invasion assays, and breast cancer xenograft model","pmids":["21481794"],"confidence":"High","gaps":["Structural basis of CCL18–PITPNM3 binding not resolved","Direct ligand-binding affinity not quantified"]},{"year":2013,"claim":"Defined a downstream effector route by showing CCL18–PITPNM3 stabilizes Snail and drives EMT through PI3K/Akt/GSK3β and actin-remodeling kinases.","evidence":"Western blot for phospho-Akt/LIMK/cofilin, siRNA knockdown, PI3K inhibitor (LY294002), in vivo lung metastasis model","pmids":["24001613"],"confidence":"Medium","gaps":["Direct coupling between receptor and PI3K not established","Single lab"]},{"year":2015,"claim":"Extended PITPNM3 receptor signaling to NF-κB activation in a second cancer type (hepatocellular carcinoma).","evidence":"siRNA knockdown, Western blot for IKK/IκBα phosphorylation, p65 nuclear translocation, migration/invasion assays","pmids":["26449829"],"confidence":"Medium","gaps":["Receptor-proximal events linking PITPNM3 to IKK not defined","Single lab"]},{"year":2016,"claim":"Connected PITPNM3 to cytoskeletal control via an ELMO1/RAC1 and integrin β1 axis in lung cancer.","evidence":"siRNA knockdown, RAC1 activation assay, ELMO1 co-signaling analysis, adhesion and invasion assays","pmids":["26756176"],"confidence":"Medium","gaps":["Whether ELMO1 physically associates with PITPNM3 not shown","Single lab"]},{"year":2020,"claim":"Added JAK2/STAT3 as a CCL18–PITPNM3 effector pathway in oral squamous cell carcinoma.","evidence":"siRNA knockdown, Western blot for JAK2/STAT3 phosphorylation, JAK inhibitor AG490, proliferation/invasion/migration assays","pmids":["32641093"],"confidence":"Medium","gaps":["Mechanism linking receptor engagement to JAK2 activation unresolved","Single lab"]},{"year":2020,"claim":"Identified an upstream transcriptional control mechanism, showing SP1 drives PITPNM3 expression and Mfn-2 represses it via SP1.","evidence":"Co-IP (Mfn-2/SP1), ChIP (SP1 on PITPNM3 promoter), RT-PCR, in vivo tumorigenicity in nude mice","pmids":["31955176"],"confidence":"Medium","gaps":["Direct effect of Mfn-2 on PITPNM3 not separated from SP1-independent routes","Single study without replication"]},{"year":2022,"claim":"Defined a distinct lipid-homeostasis function, showing PITPNM3 resides at ER-PM junctions and recruits Nir2 to support PIP2 replenishment.","evidence":"Live-cell imaging, co-immunoprecipitation, domain mapping, and PIP2 replenishment assay","pmids":["35020418"],"confidence":"High","gaps":["How junctional lipid-transfer role relates to its CCL18-receptor role not integrated","Tethering partners at ER-PM junctions not fully enumerated"]},{"year":2022,"claim":"Delimited PITPNM3's receptor role by showing that CCL18-induced microglial phagocytosis depends on CCR8, not PITPNM3.","evidence":"Selective siRNA knockdown of CCR8 vs PITPNM3, phagocytosis assays, Western blot for NF-κB/Src signaling","pmids":["35041514"],"confidence":"Medium","gaps":["Cell-type specificity of CCL18 receptor usage not mechanistically explained","Single lab negative result"]},{"year":2025,"claim":"Resolved the lipid-binding basis of PITPNM3 membrane targeting, showing its LNS2 domain binds PA and PIP2 but requires PA for localization.","evidence":"Liposome binding assays and live-cell PILS-Nir1 biosensor imaging in HEK293A cells (preprint)","pmids":["38464273"],"confidence":"Medium","gaps":["Preprint, not yet peer-reviewed","Physiological role of PA sensing in full-length PITPNM3 function not established"]},{"year":null,"claim":"How PITPNM3's ER-PM junctional lipid-transfer activity, its CCL18-receptor signaling, and its PYK2-dependent role in photoreceptors are mechanistically unified within one protein remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of full-length PITPNM3","No reconciliation of receptor vs lipid-transfer functions","PYK2-binding domain function untested biochemically"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[9]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0]},{"term_id":"GO:0140104","term_label":"molecular carrier activity","supporting_discovery_ids":[6]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[6]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[6]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,5]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[6,9]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[4]}],"complexes":[],"partners":["CCL18","NIR2","PYK2","ELMO1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9BZ71","full_name":"Membrane-associated phosphatidylinositol transfer protein 3","aliases":["Phosphatidylinositol transfer protein, membrane-associated 3","PITPnm 3","Pyk2 N-terminal domain-interacting receptor 1","NIR-1"],"length_aa":974,"mass_kda":106.8,"function":"Catalyzes the transfer of phosphatidylinositol and phosphatidylcholine between membranes (in vitro) (By similarity). Binds calcium ions","subcellular_location":"Endomembrane system","url":"https://www.uniprot.org/uniprotkb/Q9BZ71/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PITPNM3","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PITPNM3","total_profiled":1310},"omim":[{"mim_id":"608921","title":"PHOSPHATIDYLINOSITOL TRANSFER PROTEIN, MEMBRANE-ASSOCIATED, 3; PITPNM3","url":"https://www.omim.org/entry/608921"},{"mim_id":"608920","title":"PHOSPHATIDYLINOSITOL TRANSFER PROTEIN, MEMBRANE-ASSOCIATED, 2; PITPNM2","url":"https://www.omim.org/entry/608920"},{"mim_id":"600977","title":"CONE-ROD DYSTROPHY 5; CORD5","url":"https://www.omim.org/entry/600977"},{"mim_id":"120970","title":"CONE-ROD DYSTROPHY 2; CORD2","url":"https://www.omim.org/entry/120970"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"brain","ntpm":37.5},{"tissue":"lymphoid tissue","ntpm":57.5}],"url":"https://www.proteinatlas.org/search/PITPNM3"},"hgnc":{"alias_symbol":["NIR1","RDGBA3","ACKR6"],"prev_symbol":["CORD5"]},"alphafold":{"accession":"Q9BZ71","domains":[{"cath_id":"-","chopping":"130-201_212-282_388-483_546-602","consensus_level":"high","plddt":85.494,"start":130,"end":602},{"cath_id":"2.60.40.380","chopping":"621-733","consensus_level":"medium","plddt":87.2048,"start":621,"end":733},{"cath_id":"3.40.50.1000","chopping":"737-913","consensus_level":"medium","plddt":80.2303,"start":737,"end":913}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BZ71","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BZ71-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9BZ71-F1-predicted_aligned_error_v6.png","plddt_mean":66.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PITPNM3","jax_strain_url":"https://www.jax.org/strain/search?query=PITPNM3"},"sequence":{"accession":"Q9BZ71","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9BZ71.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9BZ71/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9BZ71"}},"corpus_meta":[{"pmid":"21481794","id":"PMC_21481794","title":"CCL18 from tumor-associated macrophages promotes breast cancer metastasis via PITPNM3.","date":"2011","source":"Cancer cell","url":"https://pubmed.ncbi.nlm.nih.gov/21481794","citation_count":535,"is_preprint":false},{"pmid":"8586428","id":"PMC_8586428","title":"A gene for autosomal dominant progressive cone dystrophy (CORD5) maps to chromosome 17p12-p13.","date":"1995","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/8586428","citation_count":71,"is_preprint":false},{"pmid":"24001613","id":"PMC_24001613","title":"Nir1 promotes invasion of breast cancer cells by binding to chemokine (C-C motif) ligand 18 through the PI3K/Akt/GSK3β/Snail signalling pathway.","date":"2013","source":"European journal of cancer (Oxford, England : 1990)","url":"https://pubmed.ncbi.nlm.nih.gov/24001613","citation_count":61,"is_preprint":false},{"pmid":"26449829","id":"PMC_26449829","title":"CCL18/PITPNM3 enhances migration, invasion, and EMT through the NF-κB signaling pathway in hepatocellular 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interactions","date":"2024-12-22","source":"bioRxiv","url":"https://doi.org/10.1101/2024.12.21.629891","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13964,"output_tokens":2700,"usd":0.041196,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9913,"output_tokens":3309,"usd":0.066145,"stage2_stop_reason":"end_turn"},"total_usd":0.107341,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"PITPNM3 functions as a receptor for CCL18 on breast cancer cells; CCL18 binding to PITPNM3 triggers integrin clustering, enhances adherence to extracellular matrix, activates intracellular calcium signaling, and promotes invasion and metastasis. Suppression of PITPNM3 abrogates CCL18-induced invasion and metastasis in xenograft models.\",\n      \"method\": \"siRNA knockdown of PITPNM3, intracellular calcium signaling assay, integrin clustering assay, invasion assay, breast cancer xenograft mouse model\",\n      \"journal\": \"Cancer Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — receptor identification supported by multiple orthogonal methods (knockdown, calcium signaling, integrin assays, in vivo xenograft), replicated in subsequent studies\",\n      \"pmids\": [\"21481794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CCL18 binding to PITPNM3 (Nir1) promotes phosphorylation of Akt, LIMK, and cofilin (facilitating actin polymerization), and stabilizes Snail via the PI3K/Akt/GSK3β signaling pathway, thereby inducing epithelial-mesenchymal transition (EMT) and breast cancer invasion. LY294002 (PI3K inhibitor) blocked lung metastasis in vivo.\",\n      \"method\": \"Western blot for phosphorylation, siRNA knockdown, in vivo lung metastasis model, PI3K inhibitor (LY294002) treatment\",\n      \"journal\": \"European Journal of Cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single lab, multiple downstream signaling readouts with pharmacological validation and in vivo confirmation\",\n      \"pmids\": [\"24001613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CCL18 binding to PITPNM3 activates NF-κB signaling (phosphorylation of IKK and IκBα, p65 nuclear translocation) to promote hepatocellular carcinoma cell migration, invasion, and EMT. siRNA silencing of PITPNM3 abolished these effects in PITPNM3-positive HCC cells.\",\n      \"method\": \"siRNA knockdown of PITPNM3, Western blot for IKK/IκBα phosphorylation, p65 nuclear translocation assay, migration/invasion assay\",\n      \"journal\": \"Tumour Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single lab, multiple orthogonal methods (signaling, nuclear translocation, functional assays), genetic loss-of-function\",\n      \"pmids\": [\"26449829\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CCL18 binding to PITPNM3 (Nir1) in NSCLC cells modulates cytoskeleton reorganization via RAC1 activation in an ELMO1-dependent manner, and enhances cell adhesion by activating ELMO1-integrin β1 signaling.\",\n      \"method\": \"siRNA knockdown, RAC1 activation assay, ELMO1 co-signaling analysis, adhesion assay, invasion assay\",\n      \"journal\": \"Molecular Carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single lab, multiple downstream signaling readouts with genetic knockdown\",\n      \"pmids\": [\"26756176\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"A missense mutation Q626H in the C-terminal PYK2-binding domain of PITPNM3 causes autosomal dominant cone dystrophy (CORD5), indicating that the interaction between PITPNM3 and PYK2 is important for its function in mammalian phototransduction.\",\n      \"method\": \"Genetic linkage refinement, direct sequencing of PITPNM3 in CORD5 families, mutation mapping to PYK2-interacting domain\",\n      \"journal\": \"European Journal of Human Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — disease-causing mutation mapped to functional domain in two independent families; domain-function inference without direct in vitro reconstitution\",\n      \"pmids\": [\"17377520\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"CCL18 binding to PITPNM3 (NIR1) in oral squamous cell carcinoma cells activates the JAK2/STAT3 signaling pathway to promote cancer cell growth, metastasis, and EMT. Knockdown of NIR1 or treatment with JAK inhibitor AG490 blocked rCCL18-induced effects.\",\n      \"method\": \"siRNA knockdown of NIR1, Western blot for JAK2/STAT3 phosphorylation, pharmacological inhibition (AG490), proliferation/invasion/migration assays\",\n      \"journal\": \"BMC Cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — single lab, multiple orthogonal methods (genetic, pharmacological, functional assays)\",\n      \"pmids\": [\"32641093\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PITPNM3 (Nir1) constitutively localizes at ER-PM junctions and interacts with Nir2 via a region between the FFAT motif and the DDHD domain. Nir1 potentiates Nir2 targeting to ER-PM junctions during receptor-mediated signaling and is required for efficient plasma membrane PIP2 replenishment.\",\n      \"method\": \"Live-cell imaging (constitutive ER-PM junction localization), biochemical co-immunoprecipitation (Nir1-Nir2 interaction), domain-mapping analysis, PIP2 replenishment assay\",\n      \"journal\": \"Molecular Biology of the Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — direct localization by live-cell imaging with functional consequence (PIP2 homeostasis), reciprocal interaction and domain mapping by biochemical assay, multiple orthogonal methods in one study\",\n      \"pmids\": [\"35020418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In human microglial cells, CCL18-induced phagocytosis is mediated by CCR8 rather than PITPNM3; selective knockdown of CCR8 (not PITPNM3) blocked CCL18-induced phagocytosis through the NF-κB/Src signaling pathway. PITPNM3 knockdown did not affect microglial phagocytosis.\",\n      \"method\": \"siRNA selective knockdown of CCR8 vs PITPNM3, phagocytosis assay (amyloid-β and dextran uptake), Western blot for NF-κB/Src signaling\",\n      \"journal\": \"Journal of Interferon & Cytokine Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single lab, direct genetic knockdown comparing two receptors; negative result for PITPNM3 in this specific cell context is mechanistically informative\",\n      \"pmids\": [\"35041514\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Mfn-2 suppresses PITPNM3 expression by interacting with transcription factor SP1, thereby reducing SP1 binding to the PITPNM3 promoter. SP1 overexpression increases PITPNM3 mRNA and promotes tumor growth; Mfn-2 overexpression reverses these effects.\",\n      \"method\": \"Co-immunoprecipitation (Mfn-2/SP1 interaction), ChIP assay (SP1 binding to PITPNM3 promoter), RT-PCR for PITPNM3 mRNA, in vivo tumorigenicity assay in nude mice\",\n      \"journal\": \"Medical Science Monitor\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — single lab, Co-IP and ChIP used together with in vivo validation, but single study without independent replication\",\n      \"pmids\": [\"31955176\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The LNS2 domain of PITPNM3 (Nir1) binds phosphatidic acid (PA) and PIP2 in vitro (liposome binding assays), but only PA is necessary and sufficient for membrane localization in cells. This PILS-Nir1 domain functions as a sensitive PA biosensor in live cells.\",\n      \"method\": \"Liposome binding assay, live-cell fluorescence imaging of PILS-Nir1 biosensor, pharmacological and genetic manipulation in HEK293A cells\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro liposome binding and live-cell imaging with functional domain use; preprint, single study, not yet peer-reviewed\",\n      \"pmids\": [\"38464273\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"PITPNM3 is a membrane-associated phosphatidylinositol transfer protein that (1) constitutively localizes at ER-PM junctions where it promotes Nir2 recruitment and plasma membrane PIP2 homeostasis via interaction through a region between its FFAT motif and DDHD domain, (2) serves as a functional receptor for CCL18 that activates intracellular calcium signaling, integrin clustering, and downstream pathways (PI3K/Akt/GSK3β/Snail, NF-κB, JAK2/STAT3, ELMO1/RAC1) to drive cancer cell invasion and EMT, and (3) harbors a disease-causing mutation (Q626H) in its PYK2-binding domain that causes autosomal dominant cone dystrophy (CORD5), implicating PITPNM3–PYK2 interaction in photoreceptor maintenance.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PITPNM3 (Nir1) is a membrane-associated phosphatidylinositol-transfer protein that operates at ER–plasma membrane junctions and additionally functions as a signaling receptor for the chemokine CCL18 [#6, #0]. At ER–PM junctions, where it constitutively localizes, PITPNM3 binds Nir2 through a region between its FFAT motif and DDHD domain and potentiates Nir2 targeting during receptor-mediated signaling, an activity required for efficient replenishment of plasma membrane PIP2 [#6]. Its LNS2 domain binds phosphatidic acid and PIP2 in vitro, with phosphatidic acid being necessary and sufficient for membrane localization [#9]. As a CCL18 receptor on epithelial cancer cells, PITPNM3 engagement triggers integrin clustering, intracellular calcium signaling, and enhanced extracellular-matrix adherence, driving invasion and metastasis [#0]; downstream of this receptor, CCL18 activates multiple effector cascades that converge on epithelial-mesenchymal transition and motility, including PI3K/Akt/GSK3β-dependent Snail stabilization and actin remodeling via LIMK/cofilin [#1], NF-κB activation [#2], ELMO1-dependent RAC1 and integrin β1 signaling [#3], and JAK2/STAT3 signaling [#5]. PITPNM3 expression is transcriptionally controlled by SP1, whose activity is suppressed by Mfn-2 [#8]. A missense mutation (Q626H) in the C-terminal PYK2-binding domain of PITPNM3 causes autosomal dominant cone dystrophy (CORD5), linking the protein to photoreceptor maintenance [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2007,\n      \"claim\": \"Established the first disease link for PITPNM3 by mapping a cone dystrophy mutation to its C-terminal PYK2-binding domain, implicating the protein in phototransduction.\",\n      \"evidence\": \"Genetic linkage refinement and direct sequencing in CORD5 families, with mutation mapped to the PYK2-interacting domain\",\n      \"pmids\": [\"17377520\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vitro reconstitution of the PITPNM3–PYK2 interaction\", \"Mechanism of photoreceptor maintenance not defined\", \"Functional consequence of Q626H on PYK2 binding not directly tested\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identified PITPNM3 as a functional receptor for CCL18, answering how this chemokine drives cancer cell invasion and metastasis.\",\n      \"evidence\": \"siRNA knockdown with calcium signaling, integrin clustering, invasion assays, and breast cancer xenograft model\",\n      \"pmids\": [\"21481794\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of CCL18–PITPNM3 binding not resolved\", \"Direct ligand-binding affinity not quantified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined a downstream effector route by showing CCL18–PITPNM3 stabilizes Snail and drives EMT through PI3K/Akt/GSK3β and actin-remodeling kinases.\",\n      \"evidence\": \"Western blot for phospho-Akt/LIMK/cofilin, siRNA knockdown, PI3K inhibitor (LY294002), in vivo lung metastasis model\",\n      \"pmids\": [\"24001613\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct coupling between receptor and PI3K not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Extended PITPNM3 receptor signaling to NF-κB activation in a second cancer type (hepatocellular carcinoma).\",\n      \"evidence\": \"siRNA knockdown, Western blot for IKK/IκBα phosphorylation, p65 nuclear translocation, migration/invasion assays\",\n      \"pmids\": [\"26449829\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor-proximal events linking PITPNM3 to IKK not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Connected PITPNM3 to cytoskeletal control via an ELMO1/RAC1 and integrin β1 axis in lung cancer.\",\n      \"evidence\": \"siRNA knockdown, RAC1 activation assay, ELMO1 co-signaling analysis, adhesion and invasion assays\",\n      \"pmids\": [\"26756176\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether ELMO1 physically associates with PITPNM3 not shown\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Added JAK2/STAT3 as a CCL18–PITPNM3 effector pathway in oral squamous cell carcinoma.\",\n      \"evidence\": \"siRNA knockdown, Western blot for JAK2/STAT3 phosphorylation, JAK inhibitor AG490, proliferation/invasion/migration assays\",\n      \"pmids\": [\"32641093\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking receptor engagement to JAK2 activation unresolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identified an upstream transcriptional control mechanism, showing SP1 drives PITPNM3 expression and Mfn-2 represses it via SP1.\",\n      \"evidence\": \"Co-IP (Mfn-2/SP1), ChIP (SP1 on PITPNM3 promoter), RT-PCR, in vivo tumorigenicity in nude mice\",\n      \"pmids\": [\"31955176\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct effect of Mfn-2 on PITPNM3 not separated from SP1-independent routes\", \"Single study without replication\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a distinct lipid-homeostasis function, showing PITPNM3 resides at ER-PM junctions and recruits Nir2 to support PIP2 replenishment.\",\n      \"evidence\": \"Live-cell imaging, co-immunoprecipitation, domain mapping, and PIP2 replenishment assay\",\n      \"pmids\": [\"35020418\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How junctional lipid-transfer role relates to its CCL18-receptor role not integrated\", \"Tethering partners at ER-PM junctions not fully enumerated\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Delimited PITPNM3's receptor role by showing that CCL18-induced microglial phagocytosis depends on CCR8, not PITPNM3.\",\n      \"evidence\": \"Selective siRNA knockdown of CCR8 vs PITPNM3, phagocytosis assays, Western blot for NF-κB/Src signaling\",\n      \"pmids\": [\"35041514\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cell-type specificity of CCL18 receptor usage not mechanistically explained\", \"Single lab negative result\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Resolved the lipid-binding basis of PITPNM3 membrane targeting, showing its LNS2 domain binds PA and PIP2 but requires PA for localization.\",\n      \"evidence\": \"Liposome binding assays and live-cell PILS-Nir1 biosensor imaging in HEK293A cells (preprint)\",\n      \"pmids\": [\"38464273\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not yet peer-reviewed\", \"Physiological role of PA sensing in full-length PITPNM3 function not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PITPNM3's ER-PM junctional lipid-transfer activity, its CCL18-receptor signaling, and its PYK2-dependent role in photoreceptors are mechanistically unified within one protein remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of full-length PITPNM3\", \"No reconciliation of receptor vs lipid-transfer functions\", \"PYK2-binding domain function untested biochemically\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [9]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0140104\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 5]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [6, 9]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CCL18\", \"Nir2\", \"PYK2\", \"ELMO1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}