{"gene":"LZTS3","run_date":"2026-06-10T02:59:50","timeline":{"discoveries":[{"year":2006,"finding":"ProSAPiP1 (LZTS3) was identified as a novel binding partner for the PDZ domain of ProSAP2/Shank3 at the postsynaptic density; ProSAP2/Shank3 co-immunoprecipitates with ProSAPiP1. ProSAPiP1 also binds SPAR via a central coiled-coil region containing a leucine zipper motif, and recruits SPAR to synapses. The same coiled-coil region mediates homo- and heteromultimerization of ProSAPiP1 and PSD-Zip70.","method":"Co-immunoprecipitation, yeast two-hybrid, subcellular co-localization, domain mapping","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, domain mapping, co-localization, replicated interactions with multiple binding partners in a single rigorous study","pmids":["16522626"],"is_preprint":false},{"year":2015,"finding":"Sipa1l3/SPAR3 interacts with ProSAPiP1/Lzts3 via its C-terminus, which functions as an interaction module for Fezzin family proteins including ProSAPiP1/Lzts3; this interaction contributes to postsynaptic targeting of SPAR3.","method":"Co-immunoprecipitation, pulldown, co-localization in neurons, domain truncation experiments","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and domain mapping in a single lab, multiple methods","pmids":["26364583"],"is_preprint":false},{"year":2016,"finding":"ProSAPiP1 (LZTS3) regulates SPAR protein levels at the postsynaptic density and the maturation of dendritic spines in hippocampal neurons, but is dispensable for the formation of pre- and postsynaptic specializations per se.","method":"Lentiviral-mediated overexpression and knockdown of ProSAPiP1 in primary hippocampal neurons, quantitative immunofluorescence","journal":"Frontiers in synaptic neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function and gain-of-function with defined cellular phenotype, single lab","pmids":["27252646"],"is_preprint":false},{"year":2017,"finding":"mTORC1-dependent translation of Prosapip1 is increased in the nucleus accumbens (NAc) of alcohol-consuming mice. Increased Prosapip1 promotes actin filament formation and changes in dendritic spine morphology of NAc medium spiny neurons. Prosapip1 is required for alcohol-dependent synaptic localization of GluA2-lacking AMPA receptors in NAc shell MSNs.","method":"RNA-seq, lentiviral knockdown, phalloidin staining for actin, immunofluorescence for synaptic AMPA receptor subunits, alcohol self-administration behavioral assays","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (RNA-seq, knockdown, structural imaging, receptor localization, behavioral readout) in a single rigorous study","pmids":["28890345"],"is_preprint":false},{"year":2025,"finding":"Neuronal knockout of Prosapip1 (encoded by Lzts3) in the dorsal hippocampus reduces synaptic localization of SPAR, PSD-95, and GluN2B subunit of the NMDA receptor, impairs NMDAR-mediated transmission and long-term potentiation (LTP) in CA1, and causes deficits in recognition, social, and spatial learning and memory.","method":"Cre-loxP neuronal knockout mouse, biochemical fractionation, electrophysiology (LTP in CA1), behavioral memory tasks","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with multiple orthogonal readouts (biochemistry, electrophysiology, behavior), replicated across preprint and peer-reviewed publication","pmids":["41295083","38915579"],"is_preprint":false},{"year":2025,"finding":"CK1δ protein kinase interacts with LZTS3 and phosphorylates it, enabling recognition by the E3 ubiquitin ligase β-TrCP, leading to ubiquitin-proteasome-mediated degradation of LZTS3. Two conserved degrons (DSGRNS and DSGRAS) in LZTS3 are essential for this ubiquitinated degradation.","method":"Co-immunoprecipitation, ubiquitination assays, degron mutagenesis, proteasome inhibitor experiments, in vitro and in vivo proliferation/radioresistance assays","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, mutagenesis of degrons, functional validation in vitro and in vivo, single lab","pmids":["39956246"],"is_preprint":false},{"year":2023,"finding":"LZTS3 overexpression inhibits tumor cell proliferation and migration in colorectal adenocarcinoma cells, regulates actin cytoskeleton organization, and TAGLN was identified as a downstream target of LZTS3. LZTS3 may exert biological effects by targeting the NOTCH signaling pathway.","method":"Gene overexpression and silencing, RTCA proliferation assay, Transwell migration assay, actin staining, in vivo nude mouse xenograft model","journal":"Archives of medical research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — loss-of-function and gain-of-function with defined cellular phenotypes and in vivo validation, pathway placement partly inferential","pmids":["37806182"],"is_preprint":false},{"year":2018,"finding":"miR-1275 directly binds to the 3'UTR of LZTS3 mRNA, as validated by dual luciferase reporter assay, and knockdown of miR-1275 increases LZTS3 protein levels and inhibits NSCLC cell proliferation, invasion and metastasis. NOTE: This paper (PMID 29771419) was subsequently retracted (PMID 35442501) due to ethical concerns.","method":"Dual luciferase reporter assay, qRT-PCR, Western blotting, functional cell assays","journal":"European review for medical and pharmacological sciences","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single method for binding validation; paper was retracted due to ethical concerns","pmids":["29771419","35442501"],"is_preprint":false}],"current_model":"LZTS3/ProSAPiP1 is a brain-enriched postsynaptic density scaffolding protein (a 'Fezzin') that binds ProSAP2/Shank3 via its PDZ domain and recruits SPAR-family RapGAPs (SPAR, SPAR3) via a coiled-coil/leucine zipper region; it controls the synaptic localization of SPAR, PSD-95, and GluN2B-containing NMDA receptors in the dorsal hippocampus, thereby supporting LTP and memory, and in the nucleus accumbens it drives mTORC1-dependent actin remodeling and AMPA receptor insertion that mediates alcohol reward; its protein stability is regulated by CK1δ-phosphorylation-dependent recognition by the E3 ligase β-TrCP at two degrons (DSGRNS/DSGRAS) leading to proteasomal degradation, and in non-neuronal contexts LZTS3 suppresses cell proliferation and migration with TAGLN as a downstream effector."},"narrative":{"mechanistic_narrative":"LZTS3 (ProSAPiP1) is a postsynaptic density scaffolding protein of the Fezzin family that organizes excitatory synapse signaling by physically linking ProSAP2/Shank3 to SPAR-family RapGAPs [PMID:16522626]. It binds the PDZ domain of ProSAP2/Shank3 and, through a central coiled-coil/leucine zipper region, recruits SPAR to synapses while also self-associating and heteromultimerizing with PSD-Zip70 [PMID:16522626]; the same family extends to SPAR3/Sipa1l3, which is targeted to the postsynapse via interaction with LZTS3 [PMID:26364583]. Functionally, LZTS3 sets SPAR protein levels at the PSD and drives dendritic spine maturation without being required for synapse formation per se [PMID:27252646]. In the dorsal hippocampus, neuronal loss of LZTS3 depletes synaptic SPAR, PSD-95, and GluN2B-containing NMDA receptors, impairing NMDAR-mediated transmission, CA1 long-term potentiation, and recognition, social, and spatial memory [PMID:41295083, PMID:38915579]. In the nucleus accumbens, mTORC1-dependent upregulation of LZTS3 promotes actin filament formation, spine remodeling, and synaptic insertion of GluA2-lacking AMPA receptors that mediate alcohol reward [PMID:28890345]. LZTS3 protein stability is controlled by CK1δ-dependent phosphorylation that licenses recognition by the E3 ligase β-TrCP at two degrons (DSGRNS/DSGRAS), driving ubiquitin-proteasomal degradation [PMID:39956246]. In non-neuronal cancer contexts, LZTS3 suppresses proliferation and migration and reorganizes the actin cytoskeleton with TAGLN as a downstream effector [PMID:37806182].","teleology":[{"year":2006,"claim":"Established LZTS3/ProSAPiP1 as a molecular bridge at the postsynaptic density, answering how SPAR RapGAP activity is coupled to the Shank scaffold.","evidence":"Co-immunoprecipitation, yeast two-hybrid, domain mapping and co-localization identifying ProSAP2/Shank3 (PDZ) and SPAR (coiled-coil/leucine zipper) binding plus self-/PSD-Zip70 multimerization","pmids":["16522626"],"confidence":"High","gaps":["Stoichiometry and structure of the Shank3–LZTS3–SPAR assembly not resolved","Functional consequence of multimerization not defined"]},{"year":2015,"claim":"Extended the scaffolding logic by showing a second SPAR-family RapGAP, SPAR3/Sipa1l3, uses LZTS3 as a postsynaptic targeting module.","evidence":"Co-IP, pulldown, neuronal co-localization, and domain truncation mapping the C-terminal Fezzin-interaction module","pmids":["26364583"],"confidence":"Medium","gaps":["Single lab; reciprocal in vivo validation absent","Relative contributions of SPAR vs SPAR3 to LZTS3 function unresolved"]},{"year":2016,"claim":"Defined the cellular role of LZTS3 in synapse biology, distinguishing spine maturation from synapse assembly.","evidence":"Lentiviral overexpression and knockdown in primary hippocampal neurons with quantitative immunofluorescence of SPAR and spine morphology","pmids":["27252646"],"confidence":"Medium","gaps":["In vitro neuronal system only","Mechanism linking SPAR level to spine maturation not dissected"]},{"year":2017,"claim":"Placed LZTS3 downstream of mTORC1 in a circuit-specific pathway, revealing its role in alcohol-driven synaptic plasticity.","evidence":"RNA-seq, lentiviral knockdown, phalloidin actin imaging, synaptic AMPA receptor immunofluorescence and alcohol self-administration in NAc","pmids":["28890345"],"confidence":"High","gaps":["Direct mechanism connecting LZTS3 to GluA2-lacking AMPAR trafficking not established","How mTORC1 selectively engages Prosapip1 translation unclear"]},{"year":2025,"claim":"Provided in vivo genetic proof that LZTS3 is required for hippocampal NMDAR signaling, LTP, and memory, anchoring its scaffolding role to behavior.","evidence":"Cre-loxP neuronal knockout mouse with biochemical fractionation, CA1 electrophysiology, and behavioral memory tasks (replicated across preprint and peer-reviewed report)","pmids":["41295083","38915579"],"confidence":"High","gaps":["Whether GluN2B/PSD-95 loss is a direct consequence of SPAR mislocalization not separated","Cell-type specificity within hippocampal circuits not resolved"]},{"year":2025,"claim":"Identified the post-translational control of LZTS3 abundance, defining a CK1δ–β-TrCP degron axis governing its stability.","evidence":"Co-IP, ubiquitination assays, degron mutagenesis (DSGRNS/DSGRAS), proteasome inhibition, and proliferation/radioresistance assays in vitro and in vivo","pmids":["39956246"],"confidence":"Medium","gaps":["Single lab; degron phosphosites not directly mapped by mass spectrometry","Whether this degradation operates in neurons not tested"]},{"year":2023,"claim":"Demonstrated a non-neuronal tumor-suppressive function of LZTS3 acting through cytoskeletal regulation.","evidence":"Overexpression/silencing, RTCA proliferation, Transwell migration, actin staining, and nude mouse xenografts in colorectal adenocarcinoma cells identifying TAGLN as a downstream target","pmids":["37806182"],"confidence":"Medium","gaps":["NOTCH pathway placement partly inferential","Direct vs indirect regulation of TAGLN not established"]},{"year":null,"claim":"How LZTS3 mechanistically couples its scaffolding role to AMPA/NMDA receptor trafficking and whether the CK1δ–β-TrCP degradation axis tunes synaptic LZTS3 levels in neurons remain unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of the Shank3–LZTS3–SPAR complex","Link between protein stability control and neuronal function untested","Mechanism of receptor insertion downstream of LZTS3 unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,1]},{"term_id":"GO:0008092","term_label":"cytoskeletal protein binding","supporting_discovery_ids":[3,6]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,2,4]}],"pathway":[{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[3,4]}],"complexes":["postsynaptic density"],"partners":["SHANK3","SPAR","SIPA1L3","PSD-ZIP70","CSNK1D","BTRC"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O60299","full_name":"Leucine zipper putative tumor suppressor 3","aliases":["ProSAP-interacting protein 1","ProSAPiP1"],"length_aa":673,"mass_kda":71.8,"function":"May be involved in promoting the maturation of dendritic spines, probably via regulating SIPA1L1 levels at the postsynaptic density of synapses","subcellular_location":"Synapse; Postsynaptic density; Cell projection, dendritic spine; Cell projection, dendrite; Cytoplasm, cytoskeleton","url":"https://www.uniprot.org/uniprotkb/O60299/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/LZTS3","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/LZTS3","total_profiled":1310},"omim":[],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"brain","ntpm":175.2}],"url":"https://www.proteinatlas.org/search/LZTS3"},"hgnc":{"alias_symbol":["ProSAPiP1","KIAA0552"],"prev_symbol":[]},"alphafold":{"accession":"O60299","domains":[{"cath_id":"-","chopping":"320-502_602-634","consensus_level":"medium","plddt":96.1608,"start":320,"end":634}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O60299","model_url":"https://alphafold.ebi.ac.uk/files/AF-O60299-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O60299-F1-predicted_aligned_error_v6.png","plddt_mean":63.12},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=LZTS3","jax_strain_url":"https://www.jax.org/strain/search?query=LZTS3"},"sequence":{"accession":"O60299","fasta_url":"https://rest.uniprot.org/uniprotkb/O60299.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O60299/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O60299"}},"corpus_meta":[{"pmid":"16522626","id":"PMC_16522626","title":"ProSAP-interacting protein 1 (ProSAPiP1), a novel protein of the postsynaptic density that links the spine-associated Rap-Gap (SPAR) to the scaffolding protein ProSAP2/Shank3.","date":"2006","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16522626","citation_count":49,"is_preprint":false},{"pmid":"28890345","id":"PMC_28890345","title":"Prosapip1-Dependent Synaptic Adaptations in the Nucleus Accumbens Drive Alcohol Intake, Seeking, and Reward.","date":"2017","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/28890345","citation_count":49,"is_preprint":false},{"pmid":"33315502","id":"PMC_33315502","title":"Long non-coding RNA (lncRNA) PGM5P4-AS1 inhibits lung cancer progression by up-regulating leucine zipper tumor suppressor (LZTS3) through sponging microRNA miR-1275.","date":"2021","source":"Bioengineered","url":"https://pubmed.ncbi.nlm.nih.gov/33315502","citation_count":29,"is_preprint":false},{"pmid":"29771419","id":"PMC_29771419","title":"MiR-1275 promotes non-small cell lung cancer cell proliferation and metastasis by regulating LZTS3 expression.","date":"2018","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/29771419","citation_count":23,"is_preprint":false},{"pmid":"26364583","id":"PMC_26364583","title":"Sipa1l3/SPAR3 is targeted to postsynaptic specializations and interacts with the Fezzin ProSAPiP1/Lzts3.","date":"2015","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26364583","citation_count":20,"is_preprint":false},{"pmid":"16012743","id":"PMC_16012743","title":"In silico characterization of LZTS3, a potential tumor suppressor.","date":"2005","source":"Oncology reports","url":"https://pubmed.ncbi.nlm.nih.gov/16012743","citation_count":15,"is_preprint":false},{"pmid":"27252646","id":"PMC_27252646","title":"The Shank3 Interaction Partner ProSAPiP1 Regulates Postsynaptic SPAR Levels and the Maturation of Dendritic Spines in Hippocampal Neurons.","date":"2016","source":"Frontiers in synaptic neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/27252646","citation_count":11,"is_preprint":false},{"pmid":"37806182","id":"PMC_37806182","title":"LZTS3/TAGLN Suppresses Cancer Progression in Human Colorectal Adenocarcinoma Through Regulating Cell Proliferation, Migration, and Actin Cytoskeleton.","date":"2023","source":"Archives of medical research","url":"https://pubmed.ncbi.nlm.nih.gov/37806182","citation_count":7,"is_preprint":false},{"pmid":"35442501","id":"PMC_35442501","title":"MiR-1275 promotes non-small cell lung cancer cell proliferation and metastasis by regulating LZTS3 expression.","date":"2022","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/35442501","citation_count":5,"is_preprint":false},{"pmid":"39334314","id":"PMC_39334314","title":"Thalidomide attenuates radiation-induced apoptosis and pro-inflammatory cytokine secretion in oral epithelial cells by promoting LZTS3 expression.","date":"2024","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/39334314","citation_count":3,"is_preprint":false},{"pmid":"39956246","id":"PMC_39956246","title":"LZTS3 represses tumorigenesis and radioresistance via CK1δ and β-TrCP-mediated ubiquitination pathway in lung cancer.","date":"2025","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/39956246","citation_count":2,"is_preprint":false},{"pmid":"39810258","id":"PMC_39810258","title":"Regulatory roles of eugenol in paraquat-altered SNCA/LZTS3/MAPT in the cerebellum of Wistar rats.","date":"2025","source":"Laboratory animal research","url":"https://pubmed.ncbi.nlm.nih.gov/39810258","citation_count":1,"is_preprint":false},{"pmid":"38915579","id":"PMC_38915579","title":"Prosapip1 in the dorsal hippocampus mediates synaptic protein composition, long-term potentiation, and spatial memory.","date":"2025","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/38915579","citation_count":0,"is_preprint":false},{"pmid":"41295083","id":"PMC_41295083","title":"Prosapip1 (encoded by the Lzts3 gene) in the dorsal hippocampus mediates synaptic protein composition, long-term potentiation, and spatial memory.","date":"2025","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/41295083","citation_count":0,"is_preprint":false},{"pmid":"39744581","id":"PMC_39744581","title":"Identification of the oncogenic role and clinical implication of LZTS3 in Colon Adenocarcinoma.","date":"2025","source":"Journal of Cancer","url":"https://pubmed.ncbi.nlm.nih.gov/39744581","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9167,"output_tokens":2217,"usd":0.030378,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9203,"output_tokens":2828,"usd":0.058357,"stage2_stop_reason":"end_turn"},"total_usd":0.088735,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"ProSAPiP1 (LZTS3) was identified as a novel binding partner for the PDZ domain of ProSAP2/Shank3 at the postsynaptic density; ProSAP2/Shank3 co-immunoprecipitates with ProSAPiP1. ProSAPiP1 also binds SPAR via a central coiled-coil region containing a leucine zipper motif, and recruits SPAR to synapses. The same coiled-coil region mediates homo- and heteromultimerization of ProSAPiP1 and PSD-Zip70.\",\n      \"method\": \"Co-immunoprecipitation, yeast two-hybrid, subcellular co-localization, domain mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, domain mapping, co-localization, replicated interactions with multiple binding partners in a single rigorous study\",\n      \"pmids\": [\"16522626\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Sipa1l3/SPAR3 interacts with ProSAPiP1/Lzts3 via its C-terminus, which functions as an interaction module for Fezzin family proteins including ProSAPiP1/Lzts3; this interaction contributes to postsynaptic targeting of SPAR3.\",\n      \"method\": \"Co-immunoprecipitation, pulldown, co-localization in neurons, domain truncation experiments\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and domain mapping in a single lab, multiple methods\",\n      \"pmids\": [\"26364583\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"ProSAPiP1 (LZTS3) regulates SPAR protein levels at the postsynaptic density and the maturation of dendritic spines in hippocampal neurons, but is dispensable for the formation of pre- and postsynaptic specializations per se.\",\n      \"method\": \"Lentiviral-mediated overexpression and knockdown of ProSAPiP1 in primary hippocampal neurons, quantitative immunofluorescence\",\n      \"journal\": \"Frontiers in synaptic neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function and gain-of-function with defined cellular phenotype, single lab\",\n      \"pmids\": [\"27252646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"mTORC1-dependent translation of Prosapip1 is increased in the nucleus accumbens (NAc) of alcohol-consuming mice. Increased Prosapip1 promotes actin filament formation and changes in dendritic spine morphology of NAc medium spiny neurons. Prosapip1 is required for alcohol-dependent synaptic localization of GluA2-lacking AMPA receptors in NAc shell MSNs.\",\n      \"method\": \"RNA-seq, lentiviral knockdown, phalloidin staining for actin, immunofluorescence for synaptic AMPA receptor subunits, alcohol self-administration behavioral assays\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (RNA-seq, knockdown, structural imaging, receptor localization, behavioral readout) in a single rigorous study\",\n      \"pmids\": [\"28890345\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Neuronal knockout of Prosapip1 (encoded by Lzts3) in the dorsal hippocampus reduces synaptic localization of SPAR, PSD-95, and GluN2B subunit of the NMDA receptor, impairs NMDAR-mediated transmission and long-term potentiation (LTP) in CA1, and causes deficits in recognition, social, and spatial learning and memory.\",\n      \"method\": \"Cre-loxP neuronal knockout mouse, biochemical fractionation, electrophysiology (LTP in CA1), behavioral memory tasks\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with multiple orthogonal readouts (biochemistry, electrophysiology, behavior), replicated across preprint and peer-reviewed publication\",\n      \"pmids\": [\"41295083\", \"38915579\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CK1δ protein kinase interacts with LZTS3 and phosphorylates it, enabling recognition by the E3 ubiquitin ligase β-TrCP, leading to ubiquitin-proteasome-mediated degradation of LZTS3. Two conserved degrons (DSGRNS and DSGRAS) in LZTS3 are essential for this ubiquitinated degradation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assays, degron mutagenesis, proteasome inhibitor experiments, in vitro and in vivo proliferation/radioresistance assays\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, mutagenesis of degrons, functional validation in vitro and in vivo, single lab\",\n      \"pmids\": [\"39956246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"LZTS3 overexpression inhibits tumor cell proliferation and migration in colorectal adenocarcinoma cells, regulates actin cytoskeleton organization, and TAGLN was identified as a downstream target of LZTS3. LZTS3 may exert biological effects by targeting the NOTCH signaling pathway.\",\n      \"method\": \"Gene overexpression and silencing, RTCA proliferation assay, Transwell migration assay, actin staining, in vivo nude mouse xenograft model\",\n      \"journal\": \"Archives of medical research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — loss-of-function and gain-of-function with defined cellular phenotypes and in vivo validation, pathway placement partly inferential\",\n      \"pmids\": [\"37806182\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"miR-1275 directly binds to the 3'UTR of LZTS3 mRNA, as validated by dual luciferase reporter assay, and knockdown of miR-1275 increases LZTS3 protein levels and inhibits NSCLC cell proliferation, invasion and metastasis. NOTE: This paper (PMID 29771419) was subsequently retracted (PMID 35442501) due to ethical concerns.\",\n      \"method\": \"Dual luciferase reporter assay, qRT-PCR, Western blotting, functional cell assays\",\n      \"journal\": \"European review for medical and pharmacological sciences\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single method for binding validation; paper was retracted due to ethical concerns\",\n      \"pmids\": [\"29771419\", \"35442501\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"LZTS3/ProSAPiP1 is a brain-enriched postsynaptic density scaffolding protein (a 'Fezzin') that binds ProSAP2/Shank3 via its PDZ domain and recruits SPAR-family RapGAPs (SPAR, SPAR3) via a coiled-coil/leucine zipper region; it controls the synaptic localization of SPAR, PSD-95, and GluN2B-containing NMDA receptors in the dorsal hippocampus, thereby supporting LTP and memory, and in the nucleus accumbens it drives mTORC1-dependent actin remodeling and AMPA receptor insertion that mediates alcohol reward; its protein stability is regulated by CK1δ-phosphorylation-dependent recognition by the E3 ligase β-TrCP at two degrons (DSGRNS/DSGRAS) leading to proteasomal degradation, and in non-neuronal contexts LZTS3 suppresses cell proliferation and migration with TAGLN as a downstream effector.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"LZTS3 (ProSAPiP1) is a postsynaptic density scaffolding protein of the Fezzin family that organizes excitatory synapse signaling by physically linking ProSAP2/Shank3 to SPAR-family RapGAPs [#0]. It binds the PDZ domain of ProSAP2/Shank3 and, through a central coiled-coil/leucine zipper region, recruits SPAR to synapses while also self-associating and heteromultimerizing with PSD-Zip70 [#0]; the same family extends to SPAR3/Sipa1l3, which is targeted to the postsynapse via interaction with LZTS3 [#1]. Functionally, LZTS3 sets SPAR protein levels at the PSD and drives dendritic spine maturation without being required for synapse formation per se [#2]. In the dorsal hippocampus, neuronal loss of LZTS3 depletes synaptic SPAR, PSD-95, and GluN2B-containing NMDA receptors, impairing NMDAR-mediated transmission, CA1 long-term potentiation, and recognition, social, and spatial memory [#4]. In the nucleus accumbens, mTORC1-dependent upregulation of LZTS3 promotes actin filament formation, spine remodeling, and synaptic insertion of GluA2-lacking AMPA receptors that mediate alcohol reward [#3]. LZTS3 protein stability is controlled by CK1\\u03b4-dependent phosphorylation that licenses recognition by the E3 ligase \\u03b2-TrCP at two degrons (DSGRNS/DSGRAS), driving ubiquitin-proteasomal degradation [#5]. In non-neuronal cancer contexts, LZTS3 suppresses proliferation and migration and reorganizes the actin cytoskeleton with TAGLN as a downstream effector [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Established LZTS3/ProSAPiP1 as a molecular bridge at the postsynaptic density, answering how SPAR RapGAP activity is coupled to the Shank scaffold.\",\n      \"evidence\": \"Co-immunoprecipitation, yeast two-hybrid, domain mapping and co-localization identifying ProSAP2/Shank3 (PDZ) and SPAR (coiled-coil/leucine zipper) binding plus self-/PSD-Zip70 multimerization\",\n      \"pmids\": [\"16522626\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and structure of the Shank3\\u2013LZTS3\\u2013SPAR assembly not resolved\", \"Functional consequence of multimerization not defined\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Extended the scaffolding logic by showing a second SPAR-family RapGAP, SPAR3/Sipa1l3, uses LZTS3 as a postsynaptic targeting module.\",\n      \"evidence\": \"Co-IP, pulldown, neuronal co-localization, and domain truncation mapping the C-terminal Fezzin-interaction module\",\n      \"pmids\": [\"26364583\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; reciprocal in vivo validation absent\", \"Relative contributions of SPAR vs SPAR3 to LZTS3 function unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Defined the cellular role of LZTS3 in synapse biology, distinguishing spine maturation from synapse assembly.\",\n      \"evidence\": \"Lentiviral overexpression and knockdown in primary hippocampal neurons with quantitative immunofluorescence of SPAR and spine morphology\",\n      \"pmids\": [\"27252646\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vitro neuronal system only\", \"Mechanism linking SPAR level to spine maturation not dissected\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed LZTS3 downstream of mTORC1 in a circuit-specific pathway, revealing its role in alcohol-driven synaptic plasticity.\",\n      \"evidence\": \"RNA-seq, lentiviral knockdown, phalloidin actin imaging, synaptic AMPA receptor immunofluorescence and alcohol self-administration in NAc\",\n      \"pmids\": [\"28890345\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct mechanism connecting LZTS3 to GluA2-lacking AMPAR trafficking not established\", \"How mTORC1 selectively engages Prosapip1 translation unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided in vivo genetic proof that LZTS3 is required for hippocampal NMDAR signaling, LTP, and memory, anchoring its scaffolding role to behavior.\",\n      \"evidence\": \"Cre-loxP neuronal knockout mouse with biochemical fractionation, CA1 electrophysiology, and behavioral memory tasks (replicated across preprint and peer-reviewed report)\",\n      \"pmids\": [\"41295083\", \"38915579\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether GluN2B/PSD-95 loss is a direct consequence of SPAR mislocalization not separated\", \"Cell-type specificity within hippocampal circuits not resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified the post-translational control of LZTS3 abundance, defining a CK1\\u03b4\\u2013\\u03b2-TrCP degron axis governing its stability.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, degron mutagenesis (DSGRNS/DSGRAS), proteasome inhibition, and proliferation/radioresistance assays in vitro and in vivo\",\n      \"pmids\": [\"39956246\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; degron phosphosites not directly mapped by mass spectrometry\", \"Whether this degradation operates in neurons not tested\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated a non-neuronal tumor-suppressive function of LZTS3 acting through cytoskeletal regulation.\",\n      \"evidence\": \"Overexpression/silencing, RTCA proliferation, Transwell migration, actin staining, and nude mouse xenografts in colorectal adenocarcinoma cells identifying TAGLN as a downstream target\",\n      \"pmids\": [\"37806182\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"NOTCH pathway placement partly inferential\", \"Direct vs indirect regulation of TAGLN not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How LZTS3 mechanistically couples its scaffolding role to AMPA/NMDA receptor trafficking and whether the CK1\\u03b4\\u2013\\u03b2-TrCP degradation axis tunes synaptic LZTS3 levels in neurons remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of the Shank3\\u2013LZTS3\\u2013SPAR complex\", \"Link between protein stability control and neuronal function untested\", \"Mechanism of receptor insertion downstream of LZTS3 unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [3, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 2, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"complexes\": [\"postsynaptic density\"],\n    \"partners\": [\"SHANK3\", \"SPAR\", \"SIPA1L3\", \"PSD-ZIP70\", \"CSNK1D\", \"BTRC\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}