{"gene":"FRMPD1","run_date":"2026-06-09T23:54:44","timeline":{"discoveries":[{"year":2008,"finding":"FRMPD1 binds directly to the tetratricopeptide repeat (TPR) domain of AGS3 (activator of G-protein signaling 3), as demonstrated by yeast two-hybrid and co-immunoprecipitation from cell lysates. FRMPD1 stabilizes AGS3 in a membrane fraction, and FRMPD1 knockdown in CAD neuronal cells decreases endogenous AGS3 in membrane fractions by ~50% and enhances alpha2-adrenergic receptor-mediated inhibition of forskolin-induced cAMP increases. The interaction of AGS3 with FRMPD1 and Gαi3 is mutually exclusive: as Gαi3 levels increase, AGS3 switches binding from FRMPD1 to Gαi3.","method":"Yeast two-hybrid screen, co-immunoprecipitation, cell fractionation, siRNA knockdown, fluorescence co-localization (GFP/mRFP cotransfection in COS7 cells), cAMP assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, siRNA knockdown with defined functional readout (membrane fractionation, cAMP assay), multiple orthogonal methods in one study","pmids":["18566450"],"is_preprint":false},{"year":2011,"finding":"FRMPD1 interacts with the TPR domain of LGN via a region homologous to a part of the mInsc LGN-binding domain. Crystal structure of the LGN-mInsc complex revealed the binding mode, and structure-based mutagenesis confirmed that FRMPD1 (and Frmpd4) interact with LGN TPR motifs in a manner that is mutually exclusive with mInsc, NuMA, and the LGN C-terminus. mInsc binds LGN with the highest affinity (KD ≈ 2.4 nM) and effectively displaces FRMPD1 from LGN.","method":"X-ray crystallography (2.6 Å structure of LGN-mInsc complex), structure-based mutagenesis, binding affinity measurements","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with structure-based mutagenesis and binding affinity quantification, replicated by independent structural study (PMID:23318951)","pmids":["22074847"],"is_preprint":false},{"year":2013,"finding":"Crystal structure of LGN-TPR in complex with FRMPD1 at 2.4 Å resolution revealed that a ~20-residue conserved fragment at the center of FRMPD1 is necessary and sufficient for LGN-TPR binding. The FRMPD1 fragment forms an extended structure running antiparallel along the concave channel of the TPR superhelix. A conserved 'E/QxEx4-5E/D/Qx1-2K/R' motif was identified as the core recognition element shared among LGN/Pins TPR-binding proteins.","method":"X-ray crystallography (2.4 Å resolution), biochemical binding assays, truncation/mutagenesis studies","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with biochemical validation and mutagenesis, independent replication of LGN-FRMPD1 interaction from prior study","pmids":["23318951"],"is_preprint":false},{"year":2019,"finding":"FRMPD1 interacts with the C-terminal PDZ-binding motif of WWC3 via its PDZ domain, promoting phosphorylation of LATS1 and thereby inhibiting nuclear translocation of YAP (Hippo pathway activation). Ectopic FRMPD1 expression suppressed proliferation and invasion of lung cancer cells, while FRMPD1 knockdown had opposite effects.","method":"Co-immunoprecipitation, immunoblotting (LATS1 phosphorylation), dual-luciferase assay (YAP transcriptional activity), immunofluorescence (YAP localization), gain-of-function/loss-of-function in vitro and in vivo","journal":"Cancer management and research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with functional follow-up (phosphorylation, nuclear translocation, proliferation/invasion), single lab, multiple orthogonal methods","pmids":["31114375"],"is_preprint":false},{"year":2019,"finding":"Frmpd1 expression in rod photoreceptors is driven by an alternative promoter bound by NRL and CRX transcription factors. CRISPR/Cas9 deletion of the NRL/CRX binding sites in vivo completely eliminated Frmpd1 expression in rods and dramatically reduced expression in rod bipolar cells, demonstrating cell type-specific transcriptional control of Frmpd1.","method":"Electroporation of reporter constructs in mouse retina, EMSA/binding assays for NRL and CRX, CRISPR/Cas9 genomic deletion in vivo, in vitro and in vivo reporter assays","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — CRISPR/Cas9 loss-of-function in vivo with direct transcriptional readout, confirmed by reporter assays and transcription factor binding experiments","pmids":["30445545"],"is_preprint":false},{"year":2022,"finding":"Frmpd1 directly interacts with Gpsm2 (G-protein signaling modulator 2, also known as LGN) in rod photoreceptors. Rod-specific loss of Frmpd1 causes delayed return of transducin (Gαt) from the synapse back to rod outer segments in the dark, compromising rod recovery from light adaptation, and impairs appropriate sensitization of rod-rod bipolar synaptic signaling under saturating light.","method":"Co-immunoprecipitation (Frmpd1-Gpsm2 interaction), conditional knockout mouse (rod-specific Frmpd1 deletion), immunofluorescence (Gαt localization), electrophysiology/synaptic transmission assays","journal":"eNeuro","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with defined subcellular trafficking phenotype, direct protein interaction confirmed by Co-IP, multiple functional readouts","pmids":["36180221"],"is_preprint":false},{"year":2025,"finding":"FBXO10 directly interacts with FRMPD1 and mediates its K63-linked polyubiquitination, leading to FRMPD1 stabilization (rather than degradation) independent of transcriptional regulation. FRMPD1 restoration rescues FBXO10-mediated HCC cell proliferation, placing FRMPD1 as a key downstream effector of FBXO10 in hepatocellular carcinoma.","method":"Co-immunoprecipitation (FBXO10-FRMPD1 interaction), ubiquitination assays (K63-linkage specificity), siRNA/overexpression functional rescue, proliferation assays","journal":"Current issues in molecular biology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP with ubiquitination assay and functional rescue, single lab, single study, limited methodological detail in abstract","pmids":["40699790"],"is_preprint":false}],"current_model":"FRMPD1 is a scaffold protein that (1) binds the TPR domain of LGN/Gpsm2 via a conserved extended motif (crystal structures resolved), positioning it in a network with mInsc, NuMA, and Frmpd4 that regulates asymmetric/symmetric cell division; (2) anchors AGS3 to membranes via TPR interaction, facilitating a regulated switch from FRMPD1 to Gαi3 binding; (3) activates the Hippo pathway by engaging WWC3 via its PDZ domain to promote LATS1 phosphorylation and YAP cytoplasmic retention; (4) in rod photoreceptors, interacts with Gpsm2 to facilitate light-dependent trafficking of transducin (Gαt) and modulate rod-bipolar synaptic transmission; and (5) is itself post-translationally regulated by FBXO10-mediated K63-linked ubiquitination that stabilizes FRMPD1."},"narrative":{"mechanistic_narrative":"FRMPD1 is a multidomain scaffold protein that organizes G-protein regulatory complexes and Hippo-pathway signaling at the membrane and in neural circuits [PMID:18566450, PMID:31114375, PMID:36180221]. Through its central conserved fragment, FRMPD1 binds the tetratricopeptide repeat (TPR) domain of the G-protein regulators AGS3 and LGN/Gpsm2: structural work shows the fragment runs antiparallel along the concave TPR channel via a shared 'E/QxEx4-5E/D/Qx1-2K/R' recognition motif, occupying a site that overlaps with mInsc, NuMA, and the LGN C-terminus, with mInsc binding at higher affinity and displacing FRMPD1 [PMID:22074847, PMID:23318951]. By binding AGS3 FRMPD1 stabilizes it in the membrane fraction and tunes alpha2-adrenergic receptor–mediated cAMP signaling; this anchoring is mutually exclusive with Gαi3, so rising Gαi3 switches AGS3 from FRMPD1 to Gαi3 [PMID:18566450]. In rod photoreceptors, FRMPD1 is transcribed from an alternative NRL/CRX-driven promoter and partners with Gpsm2 to support the dark-dependent return of transducin (Gαt) to outer segments and proper sensitization of rod–rod-bipolar synaptic signaling [PMID:30445545, PMID:36180221]. Independently, FRMPD1 uses its PDZ domain to engage the PDZ-binding motif of WWC3, promoting LATS1 phosphorylation and cytoplasmic retention of YAP, thereby acting as a tumor suppressor that restrains lung cancer proliferation and invasion [PMID:31114375]. FRMPD1 protein levels are post-translationally controlled by FBXO10, which mediates stabilizing K63-linked polyubiquitination of FRMPD1 in hepatocellular carcinoma [PMID:40699790].","teleology":[{"year":2008,"claim":"Established FRMPD1 as a membrane scaffold for AGS3 that modulates GPCR-coupled cAMP signaling, answering whether FRMPD1 has a defined role in G-protein regulation.","evidence":"Yeast two-hybrid, reciprocal Co-IP, cell fractionation and siRNA knockdown with cAMP readout in CAD neuronal cells","pmids":["18566450"],"confidence":"High","gaps":["Physiological context in which the FRMPD1-to-Gαi3 binding switch operates was not defined","No structural basis for the FRMPD1-AGS3 interaction was provided"]},{"year":2011,"claim":"Placed FRMPD1 within the LGN-TPR interaction network governing spindle orientation, showing its binding is mutually exclusive with mInsc, NuMA and the LGN C-terminus.","evidence":"Crystal structure of LGN-mInsc complex with structure-based mutagenesis and affinity measurements","pmids":["22074847"],"confidence":"High","gaps":["Cellular consequence of FRMPD1 occupancy of LGN versus mInsc was not tested","Direct FRMPD1-LGN structure not yet resolved at this stage"]},{"year":2013,"claim":"Defined the atomic mode of FRMPD1-LGN recognition, identifying a short conserved motif sufficient for TPR binding shared among LGN/Pins partners.","evidence":"2.4 Å crystal structure of LGN-TPR–FRMPD1 with truncation and mutagenesis","pmids":["23318951"],"confidence":"High","gaps":["Functional output of the FRMPD1-LGN complex in dividing cells not addressed","Regulation of competition among TPR ligands in vivo not established"]},{"year":2019,"claim":"Identified FRMPD1 as a Hippo-pathway activator and tumor suppressor, linking its PDZ domain to WWC3, LATS1 phosphorylation and YAP retention.","evidence":"Co-IP, LATS1 phospho-immunoblotting, YAP luciferase and localization assays, gain/loss-of-function in lung cancer cells and in vivo","pmids":["31114375"],"confidence":"Medium","gaps":["Single-lab study without independent replication","Whether scaffolding to WWC3 is direct or requires additional factors not fully resolved"]},{"year":2019,"claim":"Showed cell-type-specific transcriptional control of Frmpd1 via an alternative NRL/CRX-bound promoter, explaining its expression in rod and rod-bipolar cells.","evidence":"Retinal reporter electroporation, EMSA/binding assays, and in vivo CRISPR/Cas9 deletion of NRL/CRX sites","pmids":["30445545"],"confidence":"High","gaps":["Functional consequence of the rod-specific isoform not addressed in this study","Whether the same promoter operates in non-retinal tissues unknown"]},{"year":2022,"claim":"Defined a retinal function for FRMPD1 through its Gpsm2 interaction in transducin trafficking and rod synaptic sensitization, connecting the scaffold to phototransduction recovery.","evidence":"Co-IP, rod-specific conditional knockout mouse, Gαt immunofluorescence, and synaptic electrophysiology","pmids":["36180221"],"confidence":"High","gaps":["Mechanistic link between FRMPD1-Gpsm2 binding and transducin transport not resolved at molecular level","Whether the LGN-TPR binding motif mediates the retinal Gpsm2 interaction not tested"]},{"year":2025,"claim":"Revealed post-translational control of FRMPD1 abundance by FBXO10-mediated K63-linked ubiquitination, identifying FRMPD1 as a stabilized downstream effector in hepatocellular carcinoma.","evidence":"Co-IP, K63-linkage-specific ubiquitination assays, and functional rescue in HCC proliferation assays","pmids":["40699790"],"confidence":"Medium","gaps":["Single-lab study with limited methodological detail","Site(s) of K63 ubiquitination on FRMPD1 not mapped","Relationship between stabilized FRMPD1 and its Hippo/G-protein functions not addressed"]},{"year":null,"claim":"How FRMPD1's multiple binding modes (LGN/Gpsm2, AGS3, WWC3) are coordinated within a single cell and whether they operate in shared or distinct pathways remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No integrated model linking spindle-orientation, Hippo, and phototransduction roles","Regulatory hierarchy among competing TPR ligands in vivo undefined","Structure of full-length FRMPD1 and its domain organization uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,2,3]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,5]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,3]},{"term_id":"R-HSA-9709957","term_label":"Sensory Perception","supporting_discovery_ids":[4,5]}],"complexes":[],"partners":["GPSM2","GPSM1","WWC3","FBXO10"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q5SYB0","full_name":"FERM and PDZ domain-containing protein 1","aliases":["FERM domain-containing protein 2"],"length_aa":1578,"mass_kda":173.4,"function":"Stabilizes membrane-bound GPSM1, and thereby promotes its interaction with GNAI1","subcellular_location":"Cytoplasm, cytosol; Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q5SYB0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FRMPD1","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/FRMPD1","total_profiled":1310},"omim":[{"mim_id":"620757","title":"THROMBOCYTOPENIA 12 WITH OR WITHOUT MYOPATHY; THC12","url":"https://www.omim.org/entry/620757"},{"mim_id":"616919","title":"FERM AND PDZ DOMAINS-CONTAINING PROTEIN 1; FRMPD1","url":"https://www.omim.org/entry/616919"},{"mim_id":"609491","title":"G PROTEIN SIGNALING MODULATOR 1; GPSM1","url":"https://www.omim.org/entry/609491"},{"mim_id":"609245","title":"G PROTEIN SIGNALING MODULATOR 2; GPSM2","url":"https://www.omim.org/entry/609245"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"retina","ntpm":63.9}],"url":"https://www.proteinatlas.org/search/FRMPD1"},"hgnc":{"alias_symbol":["KIAA0967","FRMD2"],"prev_symbol":[]},"alphafold":{"accession":"Q5SYB0","domains":[{"cath_id":"2.30.42.10","chopping":"54-136","consensus_level":"high","plddt":82.59,"start":54,"end":136},{"cath_id":"2.30.29.30","chopping":"401-504","consensus_level":"medium","plddt":90.1421,"start":401,"end":504},{"cath_id":"1.20.1420.10","chopping":"1419-1576","consensus_level":"high","plddt":80.4503,"start":1419,"end":1576}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5SYB0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5SYB0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5SYB0-F1-predicted_aligned_error_v6.png","plddt_mean":52.47},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FRMPD1","jax_strain_url":"https://www.jax.org/strain/search?query=FRMPD1"},"sequence":{"accession":"Q5SYB0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5SYB0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5SYB0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5SYB0"}},"corpus_meta":[{"pmid":"22074847","id":"PMC_22074847","title":"Structural basis for interaction between the conserved cell polarity proteins Inscuteable and Leu-Gly-Asn repeat-enriched protein (LGN).","date":"2011","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/22074847","citation_count":64,"is_preprint":false},{"pmid":"17404222","id":"PMC_17404222","title":"Rat Mcs5a is a compound quantitative trait locus with orthologous human loci that associate with breast cancer risk.","date":"2007","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/17404222","citation_count":50,"is_preprint":false},{"pmid":"18566450","id":"PMC_18566450","title":"The PDZ and band 4.1 containing protein Frmpd1 regulates the subcellular location of activator of G-protein signaling 3 and its interaction with G-proteins.","date":"2008","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18566450","citation_count":30,"is_preprint":false},{"pmid":"25786224","id":"PMC_25786224","title":"Novel genetic locus implicated for HIV-1 acquisition with putative regulatory links to HIV replication and infectivity: a genome-wide association study.","date":"2015","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25786224","citation_count":22,"is_preprint":false},{"pmid":"31114375","id":"PMC_31114375","title":"FRMPD1 activates the Hippo pathway via interaction with WWC3 to suppress the proliferation and invasiveness of lung cancer cells.","date":"2019","source":"Cancer management and research","url":"https://pubmed.ncbi.nlm.nih.gov/31114375","citation_count":14,"is_preprint":false},{"pmid":"23318951","id":"PMC_23318951","title":"Structural and biochemical characterization of the interaction between LGN and Frmpd1.","date":"2013","source":"Journal of molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/23318951","citation_count":13,"is_preprint":false},{"pmid":"30445545","id":"PMC_30445545","title":"Targeted deletion of an NRL- and CRX-regulated alternative promoter specifically silences FERM and PDZ domain containing 1 (Frmpd1) in rod photoreceptors.","date":"2019","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30445545","citation_count":12,"is_preprint":false},{"pmid":"25664792","id":"PMC_25664792","title":"Structural basis for the recognition of the scaffold protein Frmpd4/Preso1 by the TPR domain of the adaptor protein LGN.","date":"2015","source":"Acta crystallographica. Section F, Structural biology communications","url":"https://pubmed.ncbi.nlm.nih.gov/25664792","citation_count":9,"is_preprint":false},{"pmid":"36180221","id":"PMC_36180221","title":"Frmpd1 Facilitates Trafficking of G-Protein Transducin and Modulates Synaptic Function in Rod Photoreceptors of Mammalian Retina.","date":"2022","source":"eNeuro","url":"https://pubmed.ncbi.nlm.nih.gov/36180221","citation_count":8,"is_preprint":false},{"pmid":"40699790","id":"PMC_40699790","title":"FBXO10 Drives Hepatocellular Carcinoma Proliferation via K63-Linked Ubiquitination and Stabilization of FRMPD1.","date":"2025","source":"Current issues in molecular biology","url":"https://pubmed.ncbi.nlm.nih.gov/40699790","citation_count":0,"is_preprint":false},{"pmid":"40525903","id":"PMC_40525903","title":"Identification of protein-coding genes associated with metastatic prostate cancer.","date":"2025","source":"Endocrine-related cancer","url":"https://pubmed.ncbi.nlm.nih.gov/40525903","citation_count":0,"is_preprint":false},{"pmid":"37734486","id":"PMC_37734486","title":"A genome-wide association scan reveals novel loci for facial traits of Koreans.","date":"2023","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/37734486","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8284,"output_tokens":2337,"usd":0.029954,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9394,"output_tokens":2951,"usd":0.060373,"stage2_stop_reason":"end_turn"},"total_usd":0.090327,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2008,\n      \"finding\": \"FRMPD1 binds directly to the tetratricopeptide repeat (TPR) domain of AGS3 (activator of G-protein signaling 3), as demonstrated by yeast two-hybrid and co-immunoprecipitation from cell lysates. FRMPD1 stabilizes AGS3 in a membrane fraction, and FRMPD1 knockdown in CAD neuronal cells decreases endogenous AGS3 in membrane fractions by ~50% and enhances alpha2-adrenergic receptor-mediated inhibition of forskolin-induced cAMP increases. The interaction of AGS3 with FRMPD1 and Gαi3 is mutually exclusive: as Gαi3 levels increase, AGS3 switches binding from FRMPD1 to Gαi3.\",\n      \"method\": \"Yeast two-hybrid screen, co-immunoprecipitation, cell fractionation, siRNA knockdown, fluorescence co-localization (GFP/mRFP cotransfection in COS7 cells), cAMP assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, siRNA knockdown with defined functional readout (membrane fractionation, cAMP assay), multiple orthogonal methods in one study\",\n      \"pmids\": [\"18566450\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"FRMPD1 interacts with the TPR domain of LGN via a region homologous to a part of the mInsc LGN-binding domain. Crystal structure of the LGN-mInsc complex revealed the binding mode, and structure-based mutagenesis confirmed that FRMPD1 (and Frmpd4) interact with LGN TPR motifs in a manner that is mutually exclusive with mInsc, NuMA, and the LGN C-terminus. mInsc binds LGN with the highest affinity (KD ≈ 2.4 nM) and effectively displaces FRMPD1 from LGN.\",\n      \"method\": \"X-ray crystallography (2.6 Å structure of LGN-mInsc complex), structure-based mutagenesis, binding affinity measurements\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with structure-based mutagenesis and binding affinity quantification, replicated by independent structural study (PMID:23318951)\",\n      \"pmids\": [\"22074847\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structure of LGN-TPR in complex with FRMPD1 at 2.4 Å resolution revealed that a ~20-residue conserved fragment at the center of FRMPD1 is necessary and sufficient for LGN-TPR binding. The FRMPD1 fragment forms an extended structure running antiparallel along the concave channel of the TPR superhelix. A conserved 'E/QxEx4-5E/D/Qx1-2K/R' motif was identified as the core recognition element shared among LGN/Pins TPR-binding proteins.\",\n      \"method\": \"X-ray crystallography (2.4 Å resolution), biochemical binding assays, truncation/mutagenesis studies\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with biochemical validation and mutagenesis, independent replication of LGN-FRMPD1 interaction from prior study\",\n      \"pmids\": [\"23318951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FRMPD1 interacts with the C-terminal PDZ-binding motif of WWC3 via its PDZ domain, promoting phosphorylation of LATS1 and thereby inhibiting nuclear translocation of YAP (Hippo pathway activation). Ectopic FRMPD1 expression suppressed proliferation and invasion of lung cancer cells, while FRMPD1 knockdown had opposite effects.\",\n      \"method\": \"Co-immunoprecipitation, immunoblotting (LATS1 phosphorylation), dual-luciferase assay (YAP transcriptional activity), immunofluorescence (YAP localization), gain-of-function/loss-of-function in vitro and in vivo\",\n      \"journal\": \"Cancer management and research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with functional follow-up (phosphorylation, nuclear translocation, proliferation/invasion), single lab, multiple orthogonal methods\",\n      \"pmids\": [\"31114375\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Frmpd1 expression in rod photoreceptors is driven by an alternative promoter bound by NRL and CRX transcription factors. CRISPR/Cas9 deletion of the NRL/CRX binding sites in vivo completely eliminated Frmpd1 expression in rods and dramatically reduced expression in rod bipolar cells, demonstrating cell type-specific transcriptional control of Frmpd1.\",\n      \"method\": \"Electroporation of reporter constructs in mouse retina, EMSA/binding assays for NRL and CRX, CRISPR/Cas9 genomic deletion in vivo, in vitro and in vivo reporter assays\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — CRISPR/Cas9 loss-of-function in vivo with direct transcriptional readout, confirmed by reporter assays and transcription factor binding experiments\",\n      \"pmids\": [\"30445545\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Frmpd1 directly interacts with Gpsm2 (G-protein signaling modulator 2, also known as LGN) in rod photoreceptors. Rod-specific loss of Frmpd1 causes delayed return of transducin (Gαt) from the synapse back to rod outer segments in the dark, compromising rod recovery from light adaptation, and impairs appropriate sensitization of rod-rod bipolar synaptic signaling under saturating light.\",\n      \"method\": \"Co-immunoprecipitation (Frmpd1-Gpsm2 interaction), conditional knockout mouse (rod-specific Frmpd1 deletion), immunofluorescence (Gαt localization), electrophysiology/synaptic transmission assays\",\n      \"journal\": \"eNeuro\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with defined subcellular trafficking phenotype, direct protein interaction confirmed by Co-IP, multiple functional readouts\",\n      \"pmids\": [\"36180221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FBXO10 directly interacts with FRMPD1 and mediates its K63-linked polyubiquitination, leading to FRMPD1 stabilization (rather than degradation) independent of transcriptional regulation. FRMPD1 restoration rescues FBXO10-mediated HCC cell proliferation, placing FRMPD1 as a key downstream effector of FBXO10 in hepatocellular carcinoma.\",\n      \"method\": \"Co-immunoprecipitation (FBXO10-FRMPD1 interaction), ubiquitination assays (K63-linkage specificity), siRNA/overexpression functional rescue, proliferation assays\",\n      \"journal\": \"Current issues in molecular biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP with ubiquitination assay and functional rescue, single lab, single study, limited methodological detail in abstract\",\n      \"pmids\": [\"40699790\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FRMPD1 is a scaffold protein that (1) binds the TPR domain of LGN/Gpsm2 via a conserved extended motif (crystal structures resolved), positioning it in a network with mInsc, NuMA, and Frmpd4 that regulates asymmetric/symmetric cell division; (2) anchors AGS3 to membranes via TPR interaction, facilitating a regulated switch from FRMPD1 to Gαi3 binding; (3) activates the Hippo pathway by engaging WWC3 via its PDZ domain to promote LATS1 phosphorylation and YAP cytoplasmic retention; (4) in rod photoreceptors, interacts with Gpsm2 to facilitate light-dependent trafficking of transducin (Gαt) and modulate rod-bipolar synaptic transmission; and (5) is itself post-translationally regulated by FBXO10-mediated K63-linked ubiquitination that stabilizes FRMPD1.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FRMPD1 is a multidomain scaffold protein that organizes G-protein regulatory complexes and Hippo-pathway signaling at the membrane and in neural circuits [#0, #3, #5]. Through its central conserved fragment, FRMPD1 binds the tetratricopeptide repeat (TPR) domain of the G-protein regulators AGS3 and LGN/Gpsm2: structural work shows the fragment runs antiparallel along the concave TPR channel via a shared 'E/QxEx4-5E/D/Qx1-2K/R' recognition motif, occupying a site that overlaps with mInsc, NuMA, and the LGN C-terminus, with mInsc binding at higher affinity and displacing FRMPD1 [#1, #2]. By binding AGS3 FRMPD1 stabilizes it in the membrane fraction and tunes alpha2-adrenergic receptor–mediated cAMP signaling; this anchoring is mutually exclusive with Gαi3, so rising Gαi3 switches AGS3 from FRMPD1 to Gαi3 [#0]. In rod photoreceptors, FRMPD1 is transcribed from an alternative NRL/CRX-driven promoter and partners with Gpsm2 to support the dark-dependent return of transducin (Gαt) to outer segments and proper sensitization of rod–rod-bipolar synaptic signaling [#4, #5]. Independently, FRMPD1 uses its PDZ domain to engage the PDZ-binding motif of WWC3, promoting LATS1 phosphorylation and cytoplasmic retention of YAP, thereby acting as a tumor suppressor that restrains lung cancer proliferation and invasion [#3]. FRMPD1 protein levels are post-translationally controlled by FBXO10, which mediates stabilizing K63-linked polyubiquitination of FRMPD1 in hepatocellular carcinoma [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Established FRMPD1 as a membrane scaffold for AGS3 that modulates GPCR-coupled cAMP signaling, answering whether FRMPD1 has a defined role in G-protein regulation.\",\n      \"evidence\": \"Yeast two-hybrid, reciprocal Co-IP, cell fractionation and siRNA knockdown with cAMP readout in CAD neuronal cells\",\n      \"pmids\": [\"18566450\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Physiological context in which the FRMPD1-to-Gαi3 binding switch operates was not defined\",\n        \"No structural basis for the FRMPD1-AGS3 interaction was provided\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Placed FRMPD1 within the LGN-TPR interaction network governing spindle orientation, showing its binding is mutually exclusive with mInsc, NuMA and the LGN C-terminus.\",\n      \"evidence\": \"Crystal structure of LGN-mInsc complex with structure-based mutagenesis and affinity measurements\",\n      \"pmids\": [\"22074847\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Cellular consequence of FRMPD1 occupancy of LGN versus mInsc was not tested\",\n        \"Direct FRMPD1-LGN structure not yet resolved at this stage\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the atomic mode of FRMPD1-LGN recognition, identifying a short conserved motif sufficient for TPR binding shared among LGN/Pins partners.\",\n      \"evidence\": \"2.4 Å crystal structure of LGN-TPR–FRMPD1 with truncation and mutagenesis\",\n      \"pmids\": [\"23318951\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Functional output of the FRMPD1-LGN complex in dividing cells not addressed\",\n        \"Regulation of competition among TPR ligands in vivo not established\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identified FRMPD1 as a Hippo-pathway activator and tumor suppressor, linking its PDZ domain to WWC3, LATS1 phosphorylation and YAP retention.\",\n      \"evidence\": \"Co-IP, LATS1 phospho-immunoblotting, YAP luciferase and localization assays, gain/loss-of-function in lung cancer cells and in vivo\",\n      \"pmids\": [\"31114375\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab study without independent replication\",\n        \"Whether scaffolding to WWC3 is direct or requires additional factors not fully resolved\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Showed cell-type-specific transcriptional control of Frmpd1 via an alternative NRL/CRX-bound promoter, explaining its expression in rod and rod-bipolar cells.\",\n      \"evidence\": \"Retinal reporter electroporation, EMSA/binding assays, and in vivo CRISPR/Cas9 deletion of NRL/CRX sites\",\n      \"pmids\": [\"30445545\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Functional consequence of the rod-specific isoform not addressed in this study\",\n        \"Whether the same promoter operates in non-retinal tissues unknown\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a retinal function for FRMPD1 through its Gpsm2 interaction in transducin trafficking and rod synaptic sensitization, connecting the scaffold to phototransduction recovery.\",\n      \"evidence\": \"Co-IP, rod-specific conditional knockout mouse, Gαt immunofluorescence, and synaptic electrophysiology\",\n      \"pmids\": [\"36180221\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Mechanistic link between FRMPD1-Gpsm2 binding and transducin transport not resolved at molecular level\",\n        \"Whether the LGN-TPR binding motif mediates the retinal Gpsm2 interaction not tested\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed post-translational control of FRMPD1 abundance by FBXO10-mediated K63-linked ubiquitination, identifying FRMPD1 as a stabilized downstream effector in hepatocellular carcinoma.\",\n      \"evidence\": \"Co-IP, K63-linkage-specific ubiquitination assays, and functional rescue in HCC proliferation assays\",\n      \"pmids\": [\"40699790\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Single-lab study with limited methodological detail\",\n        \"Site(s) of K63 ubiquitination on FRMPD1 not mapped\",\n        \"Relationship between stabilized FRMPD1 and its Hippo/G-protein functions not addressed\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How FRMPD1's multiple binding modes (LGN/Gpsm2, AGS3, WWC3) are coordinated within a single cell and whether they operate in shared or distinct pathways remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No integrated model linking spindle-orientation, Hippo, and phototransduction roles\",\n        \"Regulatory hierarchy among competing TPR ligands in vivo undefined\",\n        \"Structure of full-length FRMPD1 and its domain organization uncharacterized\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"R-HSA-9709957\", \"supporting_discovery_ids\": [4, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"GPSM2\", \"GPSM1\", \"WWC3\", \"FBXO10\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":6,"faith_pct":83.33333333333333}}