{"gene":"NPEPPS","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":2006,"finding":"Puromycin-sensitive aminopeptidase (PSA/NPEPPS) directly proteolyzes tau protein in vitro, and PSA loss-of-function exacerbates tau-induced neurodegeneration in Drosophila while PSA gain-of-function protects against it, establishing PSA as an inhibitor of tau-induced neurodegeneration.","method":"In vitro proteolysis assay with purified human PSA and tau protein; Drosophila genetic loss-of-function and gain-of-function experiments with neurodegeneration phenotype readout","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct in vitro proteolysis assay combined with in vivo genetic epistasis in Drosophila, replicated in mammalian system by subsequent studies","pmids":["16950154"],"is_preprint":false},{"year":2011,"finding":"PSA/NPEPPS overexpression in hPSA/TAU(P301L) double-transgenic mice significantly reduced total and hyperphosphorylated TAU levels in multiple brain regions, delayed paralysis, and improved motor neuron counts; knockdown of PSA/NPEPPS in SH-SY5Y neuroblastoma cells augmented endogenous TAU abundance, while overexpression reduced it, confirming in vivo TAU proteolysis.","method":"BAC-transgenic mouse cross with TAU(P301L) model; Western blot quantification of phospho-TAU; shRNA knockdown and overexpression in human neuroblastoma cells","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (transgenic mouse model, cell-based KD/OE), replicated in both in vivo and in vitro systems","pmids":["21320871"],"is_preprint":false},{"year":2011,"finding":"PSA/NPEPPS directly regulates SOD1 protein abundance and clearance via proteolysis; PSA/NPEPPS expression is significantly decreased in motor neurons of SOD1G93A transgenic mice and sporadic ALS patients.","method":"In vitro proteolysis assay with PSA/NPEPPS and SOD1; Western blot quantification of SOD1 upon PSA overexpression/knockdown; immunohistochemistry of ALS patient tissue","journal":"Molecular neurodegeneration","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct proteolysis assay and cell-based KD/OE, single lab, two methods","pmids":["21548977"],"is_preprint":false},{"year":1994,"finding":"MP100 (NPEPPS) was purified from human brain and characterized as a metalloprotease with broad substrate specificity that cleaves a beta-APP-derived peptide substrate in vitro, generating a cleavage product at the beta-site.","method":"Protein purification from human brain; in vitro enzymatic assay with chromogenic peptide substrate; molecular weight determination","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic assay with purified protein, single lab, single study","pmids":["8198608"],"is_preprint":false},{"year":1999,"finding":"MP100 (NPEPPS) cDNA was cloned and found to be nearly identical to puromycin-sensitive aminopeptidase (PSA); recombinant human MP100 cleaved a free beta-site-spanning amyloid beta peptide (Aβ(-10/+10)) generating Aβ(1-10), but did not cleave N- and C-terminally blocked substrate or purified beta-APP; coexpression of MP100 with beta-APP695 did not increase Aβ levels in HEK cells; MP100 and beta-APP colocalized and co-immunoprecipitated from rat brain extracts.","method":"cDNA cloning; recombinant protein expression; in vitro peptide cleavage assay; co-immunoprecipitation from rat brain; double immunofluorescence in transfected HEK cells and neuroblastoma cells","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro cleavage assay plus co-IP, negative beta-secretase result rigorously established, single lab","pmids":["10037494"],"is_preprint":false},{"year":1999,"finding":"MP100 (NPEPPS) localizes to synaptic sites in rat brain neurons, co-fractionates with presynaptic marker synaptophysin and beta-APP in synaptosomal membrane fractions, and shows punctate intracellular immunostaining consistent with vesicular structures, suggesting a role in proteolytic modification of synaptic proteins.","method":"Immunohistochemistry and immunoelectron microscopy of rat brain; gel filtration chromatography of synaptosomal membranes with co-fractionation analysis","journal":"Brain research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct subcellular localization by immunoelectron microscopy combined with biochemical co-fractionation, single lab","pmids":["10434003"],"is_preprint":false},{"year":2021,"finding":"PSA/NPEPPS mediates NRF2 signaling in hepatocytes by stabilizing NRF2 protein (suppressing NRF2 ubiquitination); PSA knockdown exacerbated diet-induced triglyceride accumulation through enhanced lipogenesis and attenuated fatty acid β-oxidation; liver-specific PSA overexpression attenuated hepatic lipid accumulation in ob/ob mice.","method":"shRNA knockdown and adeno-associated virus-mediated overexpression in hepatocytes and ob/ob mice; Western blot for NRF2 and ubiquitination; lipid accumulation assays","journal":"Journal of molecular cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD/OE with defined cellular and in vivo phenotype, NRF2 ubiquitination assay, single lab","pmids":["34048566"],"is_preprint":false},{"year":2024,"finding":"NPEPPS drives cisplatin resistance by regulating intracellular cisplatin concentrations; NPEPPS depletion sensitized resistant bladder cancer cells to cisplatin in vitro and in vivo, and in patient-derived organoids; NPEPPS overexpression in sensitive cells increased cisplatin resistance.","method":"Whole-genome CRISPR screen; KD/KO and overexpression in bladder cancer cell lines; in vivo xenograft experiments; patient-derived organoid cisplatin sensitivity assays; intracellular cisplatin concentration measurement","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — CRISPR screen plus reciprocal gain/loss-of-function with defined molecular readout (intracellular drug concentration), validated in vivo and in PDOs","pmids":["38535994"],"is_preprint":false},{"year":2025,"finding":"PSA/NPEPPS physically binds the obligatory VRAC subunit SWELL1 (LRRC8A); cryo-EM structure shows three PSA molecules binding a single SWELL1 hexamer, coupling adjacent leucine-rich repeat domains into local dimers; PSA overexpression suppresses VRAC activation, PSA deletion dramatically elevates basal VRAC channel activity; PSA modulation of VRACs requires physical binding but not aminopeptidase catalytic activity, indicating a structural (non-enzymatic) mechanism; PSA/NPEPPS also modulates cGAMP transport through VRACs.","method":"Cryo-electron microscopy structure determination; co-immunoprecipitation; overexpression and genetic deletion with electrophysiological VRAC activity readout; aminopeptidase-dead mutant functional assay; cGAMP transport assay","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structure combined with mutagenesis (catalytic dead mutant), electrophysiology, and genetic deletion, multiple orthogonal methods in single rigorous study","pmids":["41371222"],"is_preprint":false},{"year":2024,"finding":"NPEPPS interacts with volume-regulated anion channels (VRACs) to control cisplatin import into cells; NPEPPS/VRAC gene expression ratio is a predictive measure of cisplatin response across multiple cancer types; pharmacologic inhibition of NPEPPS increased cisplatin sensitivity in patient-derived organoids.","method":"Interaction studies between NPEPPS and VRAC subunits; cisplatin uptake assays; gene expression ratio analysis in cancer cohorts; PDO pharmacologic inhibition experiments","journal":"Science advances","confidence":"High","confidence_rationale":"Tier 2 / Strong — mechanistic interaction with VRACs established with cisplatin import as functional readout, validated in PDOs and multiple cancer cohorts, extends prior CRISPR study","pmids":["39671496"],"is_preprint":false},{"year":2020,"finding":"Puromycin selectively inhibits PSA/NPEPPS among M1 family aminopeptidases; structural and biochemical analysis showed puromycin does not enter the active site but binds near the entrance to block substrate access; other M1 enzymes hydrolyze puromycin as a substrate rather than being inhibited by it.","method":"In vitro enzymatic assays with four M1 family enzymes; X-ray crystallography of ePepN with puromycin (wild-type and E298A mutant); molecular modeling of PSA active site","journal":"International journal of biological macromolecules","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with active-site mutant combined with biochemical assay, mechanistic selectivity fully established, single lab","pmids":["33045297"],"is_preprint":false},{"year":2001,"finding":"NPEPPS (PSA) is a predominantly cytoplasmic zinc-dependent exopeptidase; the gene was physically mapped to chromosome 17q21.2→q21.32 by fluorescence in situ hybridization, and a polymorphism at amino acid position 140 was identified.","method":"Fluorescence in situ hybridization (FISH); sequencing of coding region; tissue distribution analysis","journal":"Cytogenetics and cell genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — direct chromosomal localization by FISH, subcellular localization stated but not experimentally detailed in abstract, single lab","pmids":["11435692"],"is_preprint":false},{"year":2026,"finding":"NPEPPS acts as a binding partner of angiotensin II, a key vasoactive peptide hormone, as identified by PISA thermal stability assay, representing a previously uncharacterized peptide-protein interaction.","method":"Proteome integral solubility alteration (PISA) assay / thermal proteome profiling with TMT-based multiplexing","journal":"bioRxiv","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single thermal shift assay method, preprint, no functional validation of the interaction reported in abstract","pmids":["42146573"],"is_preprint":true}],"current_model":"NPEPPS (PSA/MP100) is a cytoplasmic zinc-dependent M1-family metalloaminopeptidase that proteolyzes neurotoxic substrates including tau and SOD1 to protect against neurodegeneration; acts as a structural (non-catalytic) inhibitory auxiliary subunit of volume-regulated anion channels (VRACs) by physically binding SWELL1 hexamers to suppress channel activation and control intracellular cisplatin concentrations; stabilizes NRF2 by suppressing its ubiquitination to regulate hepatic lipid metabolism; and is selectively inhibited by puromycin through an active-site-blocking mechanism distinct from substrate hydrolysis."},"narrative":{"mechanistic_narrative":"NPEPPS (PSA/MP100) is a predominantly cytoplasmic, zinc-dependent M1-family metalloaminopeptidase that proteolytically clears neurotoxic substrates and thereby protects against neurodegeneration [PMID:16950154, PMID:11435692]. It directly proteolyzes tau in vitro, and its activity is protective in vivo: PSA loss exacerbates and PSA gain suppresses tau-induced neurodegeneration in Drosophila, while PSA overexpression in TAU(P301L) mice lowers total and hyperphosphorylated tau, delays paralysis, and preserves motor neurons [PMID:16950154, PMID:21320871]. PSA likewise regulates the abundance and clearance of SOD1, and its expression is reduced in motor neurons of SOD1G93A mice and sporadic ALS patients [PMID:21548977]. Beyond its catalytic role, NPEPPS has a distinct non-enzymatic function as a structural inhibitory partner of the volume-regulated anion channel (VRAC): cryo-EM shows three PSA molecules clamping a single SWELL1 (LRRC8A) hexamer to couple adjacent leucine-rich-repeat domains, and PSA suppresses basal VRAC activation through physical binding that does not require aminopeptidase activity [PMID:41371222]. Through this VRAC interaction NPEPPS controls intracellular cisplatin concentrations, driving cisplatin resistance such that its depletion or pharmacologic inhibition resensitizes resistant bladder cancer cells, xenografts, and patient-derived organoids, with the NPEPPS/VRAC expression ratio predicting cisplatin response across cancers [PMID:38535994, PMID:39671496]. NPEPPS also stabilizes NRF2 by suppressing its ubiquitination in hepatocytes, restraining diet-induced hepatic lipid accumulation [PMID:34048566]. Puromycin selectively inhibits NPEPPS by binding near the active-site entrance to block substrate access rather than being hydrolyzed [PMID:33045297].","teleology":[{"year":1994,"claim":"Established the basic biochemical identity of the protein, showing that brain-derived MP100 is a broad-specificity metalloprotease, the founding observation of its enzymatic character.","evidence":"Protein purification from human brain with in vitro chromogenic peptide assay","pmids":["8198608"],"confidence":"Medium","gaps":["Physiological substrates not defined","Subcellular compartment not resolved"]},{"year":1999,"claim":"Linked MP100 to PSA at the sequence level and tested an amyloidogenic role, resolving whether the enzyme acts as a beta-secretase by showing it cleaves free Abeta-spanning peptides but not intact beta-APP.","evidence":"cDNA cloning, recombinant peptide cleavage assays, co-IP and colocalization with beta-APP in rat brain and HEK/neuroblastoma cells; synaptic localization by immunoelectron microscopy and synaptosomal co-fractionation","pmids":["10037494","10434003"],"confidence":"Medium","gaps":["No beta-secretase activity on native substrate","Functional significance of synaptic localization untested"]},{"year":2001,"claim":"Defined NPEPPS as a cytoplasmic zinc-dependent exopeptidase and mapped the gene, providing genetic and compartmental grounding.","evidence":"FISH chromosomal mapping and coding-region sequencing","pmids":["11435692"],"confidence":"Medium","gaps":["Functional consequence of the position-140 polymorphism unknown"]},{"year":2006,"claim":"Identified tau as a direct proteolytic substrate and demonstrated a protective role against neurodegeneration, establishing NPEPPS as a modifier of tauopathy.","evidence":"In vitro proteolysis of tau plus Drosophila loss/gain-of-function neurodegeneration assays","pmids":["16950154"],"confidence":"High","gaps":["Cleavage sites on tau not mapped","Regulation of PSA activity in neurons unknown"]},{"year":2011,"claim":"Extended the neuroprotective tau model to mammals and added SOD1 as a substrate, broadening NPEPPS into a clearance factor for multiple neurodegeneration-associated proteins.","evidence":"TAU(P301L) transgenic mouse crosses with phospho-TAU quantification, cell KD/OE; in vitro SOD1 proteolysis with KD/OE and ALS tissue immunohistochemistry","pmids":["21320871","21548977"],"confidence":"High","gaps":["Whether reduced PSA causes or follows ALS pathology unresolved","SOD1 evidence from a single lab"]},{"year":2021,"claim":"Revealed a non-proteolytic regulatory function in metabolism, showing NPEPPS stabilizes NRF2 to restrain hepatic lipid accumulation.","evidence":"Hepatocyte and ob/ob mouse KD/OE with NRF2 ubiquitination and lipid assays","pmids":["34048566"],"confidence":"Medium","gaps":["Mechanism by which NPEPPS suppresses NRF2 ubiquitination unknown","Whether catalytic activity is required untested"]},{"year":2024,"claim":"Connected NPEPPS to chemoresistance, establishing that it controls intracellular cisplatin levels via VRAC interaction and serves as a predictive biomarker and therapeutic target.","evidence":"Whole-genome CRISPR screen, reciprocal KD/KO/OE with intracellular cisplatin measurement, xenografts, PDOs, and NPEPPS/VRAC expression-ratio analysis across cancer cohorts","pmids":["38535994","39671496"],"confidence":"High","gaps":["Molecular basis of VRAC regulation not yet structural","Whether catalytic activity contributes to cisplatin handling unclear"]},{"year":2025,"claim":"Provided the structural and mechanistic basis for NPEPPS as a non-enzymatic VRAC subunit, showing physical clamping of SWELL1 hexamers suppresses channel activity independent of aminopeptidase function.","evidence":"Cryo-EM of the PSA–SWELL1 complex, co-IP, electrophysiology with overexpression/deletion, catalytic-dead mutant, and cGAMP transport assays","pmids":["41371222"],"confidence":"High","gaps":["How VRAC binding integrates with cytoplasmic proteolytic roles unknown","Physiological triggers governing PSA–VRAC stoichiometry undefined"]},{"year":null,"claim":"It remains unknown whether NPEPPS engages additional regulatory peptides such as angiotensin II and how its dual catalytic and structural-scaffold roles are partitioned in vivo.","evidence":"PISA thermal stability assay identifying angiotensin II binding (preprint, no functional validation)","pmids":[],"confidence":"Low","gaps":["Angiotensin II interaction from a single thermal-shift assay, not functionally validated","No integrated model reconciling proteolytic, NRF2-stabilizing, and VRAC-scaffold functions"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,2,3,4]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[3,11]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[6,8]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[11]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,1,2]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[7,8,9]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[7,9]}],"complexes":["VRAC (SWELL1/LRRC8A channel)"],"partners":["LRRC8A","MAPT","SOD1","NFE2L2","APP"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P55786","full_name":"Puromycin-sensitive aminopeptidase","aliases":["Cytosol alanyl aminopeptidase","AAP-S"],"length_aa":919,"mass_kda":103.3,"function":"Aminopeptidase with broad substrate specificity for several peptides. Involved in proteolytic events essential for cell growth and viability. May act as regulator of neuropeptide activity. Plays a role in the antigen-processing pathway for MHC class I molecules. Involved in the N-terminal trimming of cytotoxic T-cell epitope precursors. Digests the poly-Q peptides found in many cellular proteins. Digests tau from normal brain more efficiently than tau from Alzheimer disease brain","subcellular_location":"Cytoplasm, cytosol; Nucleus","url":"https://www.uniprot.org/uniprotkb/P55786/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/NPEPPS","classification":"Common Essential","n_dependent_lines":717,"n_total_lines":1208,"dependency_fraction":0.5935430463576159},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SNX4","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/NPEPPS","total_profiled":1310},"omim":[{"mim_id":"611240","title":"GPRIN FAMILY, MEMBER 2; GPRIN2","url":"https://www.omim.org/entry/611240"},{"mim_id":"610813","title":"HYDIN AXONEMAL CENTRAL PAIR APPARATUS PROTEIN 2; HYDIN2","url":"https://www.omim.org/entry/610813"},{"mim_id":"610501","title":"NEUROBLASTOMA BREAKPOINT FAMILY, MEMBER 1; NBPF1","url":"https://www.omim.org/entry/610501"},{"mim_id":"606793","title":"AMINOPEPTIDASE, PUROMYCIN-SENSITIVE; NPEPPS","url":"https://www.omim.org/entry/606793"},{"mim_id":"606524","title":"SLIT-ROBO RHO GTPase-ACTIVATING PROTEIN 2; SRGAP2","url":"https://www.omim.org/entry/606524"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/NPEPPS"},"hgnc":{"alias_symbol":["PSA","MP100"],"prev_symbol":[]},"alphafold":{"accession":"P55786","domains":[{"cath_id":"2.60.40.1730","chopping":"53-251","consensus_level":"medium","plddt":96.3086,"start":53,"end":251},{"cath_id":"1.10.390.10","chopping":"358-498","consensus_level":"medium","plddt":95.4267,"start":358,"end":498},{"cath_id":"2.60.40.1910","chopping":"503-631","consensus_level":"medium","plddt":94.9562,"start":503,"end":631}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P55786","model_url":"https://alphafold.ebi.ac.uk/files/AF-P55786-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P55786-F1-predicted_aligned_error_v6.png","plddt_mean":91.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NPEPPS","jax_strain_url":"https://www.jax.org/strain/search?query=NPEPPS"},"sequence":{"accession":"P55786","fasta_url":"https://rest.uniprot.org/uniprotkb/P55786.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P55786/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P55786"}},"corpus_meta":[{"pmid":"16950154","id":"PMC_16950154","title":"A genomic screen for modifiers of tauopathy identifies puromycin-sensitive aminopeptidase as an inhibitor of tau-induced neurodegeneration.","date":"2006","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/16950154","citation_count":118,"is_preprint":false},{"pmid":"1738004","id":"PMC_1738004","title":"Characterization of neutral proteinases from Alzheimer-affected and control brain specimens: identification of calcium-dependent metalloproteinases from the hippocampus.","date":"1992","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/1738004","citation_count":104,"is_preprint":false},{"pmid":"32854315","id":"PMC_32854315","title":"Proteomic Profiling of Extracellular Vesicles Derived from Cerebrospinal Fluid of Alzheimer's Disease Patients: A Pilot Study.","date":"2020","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/32854315","citation_count":103,"is_preprint":false},{"pmid":"15351382","id":"PMC_15351382","title":"Perceived effort in force production as reflected in motor-related cortical potentials.","date":"2004","source":"Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/15351382","citation_count":72,"is_preprint":false},{"pmid":"21320871","id":"PMC_21320871","title":"Puromycin-sensitive aminopeptidase (PSA/NPEPPS) impedes development of neuropathology in hPSA/TAU(P301L) double-transgenic mice.","date":"2011","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21320871","citation_count":41,"is_preprint":false},{"pmid":"19308253","id":"PMC_19308253","title":"High-throughput proteomics detection of novel splice isoforms in human platelets.","date":"2009","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/19308253","citation_count":28,"is_preprint":false},{"pmid":"29448950","id":"PMC_29448950","title":"Identification and characterization of microRNA in the lung tissue of pigs with different susceptibilities to PCV2 infection.","date":"2018","source":"Veterinary research","url":"https://pubmed.ncbi.nlm.nih.gov/29448950","citation_count":23,"is_preprint":false},{"pmid":"35778292","id":"PMC_35778292","title":"Effects of postpolymerization conditions on the physical properties, cytotoxicity, and dimensional accuracy of a 3D printed dental restorative material.","date":"2022","source":"The Journal of prosthetic dentistry","url":"https://pubmed.ncbi.nlm.nih.gov/35778292","citation_count":23,"is_preprint":false},{"pmid":"21548977","id":"PMC_21548977","title":"Cu, Zn-superoxide dismutase 1 (SOD1) is a novel target of Puromycin-sensitive aminopeptidase (PSA/NPEPPS): PSA/NPEPPS is a possible modifier of amyotrophic lateral sclerosis.","date":"2011","source":"Molecular neurodegeneration","url":"https://pubmed.ncbi.nlm.nih.gov/21548977","citation_count":22,"is_preprint":false},{"pmid":"8198608","id":"PMC_8198608","title":"Purification and characterization of a novel metalloprotease from human brain with the ability to cleave substrates derived from the N-terminus of beta-amyloid protein.","date":"1994","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/8198608","citation_count":20,"is_preprint":false},{"pmid":"26921792","id":"PMC_26921792","title":"MEF2D and MEF2C pathways disruption in sporadic and familial ALS patients.","date":"2016","source":"Molecular and cellular neurosciences","url":"https://pubmed.ncbi.nlm.nih.gov/26921792","citation_count":19,"is_preprint":false},{"pmid":"3700026","id":"PMC_3700026","title":"Aging of lens fibers. Mapping membrane proteins with monoclonal antibodies.","date":"1986","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/3700026","citation_count":18,"is_preprint":false},{"pmid":"34048566","id":"PMC_34048566","title":"PSA controls hepatic lipid metabolism by regulating the NRF2 signaling pathway.","date":"2021","source":"Journal of molecular cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/34048566","citation_count":15,"is_preprint":false},{"pmid":"25903667","id":"PMC_25903667","title":"Revisiting MHC genes in spondyloarthritis.","date":"2015","source":"Current rheumatology reports","url":"https://pubmed.ncbi.nlm.nih.gov/25903667","citation_count":14,"is_preprint":false},{"pmid":"33414811","id":"PMC_33414811","title":"Identification of a Ubiquitination-Related Gene Risk Model for Predicting Survival in Patients With Pancreatic Cancer.","date":"2020","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33414811","citation_count":14,"is_preprint":false},{"pmid":"10037494","id":"PMC_10037494","title":"cDNA cloning and molecular characterization of human brain metalloprotease MP100: a beta-secretase candidate?","date":"1999","source":"Journal of neurochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10037494","citation_count":13,"is_preprint":false},{"pmid":"26024963","id":"PMC_26024963","title":"Maternal metabolizable protein restriction during late gestation on uterine and umbilical blood flows and maternal and fetal amino acid concentrations near term in sheep.","date":"2015","source":"Animal reproduction science","url":"https://pubmed.ncbi.nlm.nih.gov/26024963","citation_count":13,"is_preprint":false},{"pmid":"36444934","id":"PMC_36444934","title":"Whole-exome sequencing study identifies four novel gene loci associated with diabetic kidney disease.","date":"2023","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/36444934","citation_count":11,"is_preprint":false},{"pmid":"11790417","id":"PMC_11790417","title":"Differential cardiovascular effects of pharmacological agents in chickens selected for high and low body weight.","date":"2001","source":"Physiology & behavior","url":"https://pubmed.ncbi.nlm.nih.gov/11790417","citation_count":9,"is_preprint":false},{"pmid":"38535994","id":"PMC_38535994","title":"NPEPPS Is a Druggable Driver of Platinum Resistance.","date":"2024","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/38535994","citation_count":8,"is_preprint":false},{"pmid":"38464509","id":"PMC_38464509","title":"CD8+ T and NK cells characterized by upregulation of NPEPPS and ABHD17A are associated with the co-occurrence of type 2 diabetes and coronary artery disease.","date":"2024","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/38464509","citation_count":8,"is_preprint":false},{"pmid":"26416263","id":"PMC_26416263","title":"Supplementation of metabolizable protein during late gestation and fetal number impact ewe organ mass, maternal serum hormone and metabolite concentrations, and conceptus measurements.","date":"2015","source":"Domestic animal endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/26416263","citation_count":8,"is_preprint":false},{"pmid":"11531699","id":"PMC_11531699","title":"Radiation hybrid comparative mapping between human chromosome 17 and porcine chromosome 12 demonstrates conservation of gene order.","date":"2001","source":"Animal genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11531699","citation_count":7,"is_preprint":false},{"pmid":"31523044","id":"PMC_31523044","title":"Analysis of 47 Non-MHC Ankylosing Spondylitis Susceptibility Loci Regarding Associated Variants across Whites and Han Chinese.","date":"2019","source":"The Journal of rheumatology","url":"https://pubmed.ncbi.nlm.nih.gov/31523044","citation_count":7,"is_preprint":false},{"pmid":"39671496","id":"PMC_39671496","title":"Regulation of volume-regulated anion channels alters sensitivity to platinum chemotherapy.","date":"2024","source":"Science advances","url":"https://pubmed.ncbi.nlm.nih.gov/39671496","citation_count":6,"is_preprint":false},{"pmid":"20122891","id":"PMC_20122891","title":"Expression of exogenous proteins and short hairpin RNAs in human primary thyrocytes.","date":"2010","source":"Analytical biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20122891","citation_count":6,"is_preprint":false},{"pmid":"31011873","id":"PMC_31011873","title":"An evaluation of mixed plant protein in the diet of Yellow River carp (Cyprinus carpio): growth, body composition, biochemical parameters, and growth hormone/insulin-like growth factor 1.","date":"2019","source":"Fish physiology and biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/31011873","citation_count":6,"is_preprint":false},{"pmid":"38468567","id":"PMC_38468567","title":"Primary cutaneous apocrine carcinoma with RARA::NPEPPS fusion.","date":"2024","source":"Journal of cutaneous pathology","url":"https://pubmed.ncbi.nlm.nih.gov/38468567","citation_count":5,"is_preprint":false},{"pmid":"10434003","id":"PMC_10434003","title":"Metalloprotease MP100: a synaptic protease in rat brain.","date":"1999","source":"Brain research","url":"https://pubmed.ncbi.nlm.nih.gov/10434003","citation_count":5,"is_preprint":false},{"pmid":"38003247","id":"PMC_38003247","title":"A Multi-Omics Approach Revealed Common Dysregulated Pathways in Type One and Type Two Endometrial Cancers.","date":"2023","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38003247","citation_count":5,"is_preprint":false},{"pmid":"33045297","id":"PMC_33045297","title":"Puromycin, a selective inhibitor of PSA acts as a substrate for other M1 family aminopeptidases: Biochemical and structural basis.","date":"2020","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/33045297","citation_count":5,"is_preprint":false},{"pmid":"39912629","id":"PMC_39912629","title":"Gene Fusion-Driven Cutaneous Adnexal Neoplasms: An Updated Review Emphasizing Molecular Characteristics.","date":"2025","source":"The American Journal of dermatopathology","url":"https://pubmed.ncbi.nlm.nih.gov/39912629","citation_count":4,"is_preprint":false},{"pmid":"40214710","id":"PMC_40214710","title":"Identifying Potential Drug Targets in Coronary Atherosclerosis: Insights from the Druggable Genome and Mendelian Randomization.","date":"2025","source":"Cardiovascular drugs and therapy","url":"https://pubmed.ncbi.nlm.nih.gov/40214710","citation_count":4,"is_preprint":false},{"pmid":"11435692","id":"PMC_11435692","title":"Human puromycin-sensitive aminopeptidase: cloning of 3' UTR, evidence for a polymorphism at a.a. 140 and refined chromosomal localization to 17q21.","date":"2001","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/11435692","citation_count":4,"is_preprint":false},{"pmid":"35367778","id":"PMC_35367778","title":"Maternal metabolizable protein restriction during gestation affects the vascular function of maternal and fetal placental arteries in sheep.","date":"2022","source":"Theriogenology","url":"https://pubmed.ncbi.nlm.nih.gov/35367778","citation_count":2,"is_preprint":false},{"pmid":"40869915","id":"PMC_40869915","title":"Customized Chromosomal Microarrays for Neurodevelopmental Disorders.","date":"2025","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/40869915","citation_count":1,"is_preprint":false},{"pmid":"39290304","id":"PMC_39290304","title":"Identification of significant biomarkers for predicting the risk of bipolar disorder with arteriosclerosis based on integrative bioinformatics and machine learning.","date":"2024","source":"Frontiers in psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/39290304","citation_count":1,"is_preprint":false},{"pmid":"39843945","id":"PMC_39843945","title":"Long noncoding RNA DHRS4 antisense RNA 1 suppresses osteosarcoma cell proliferation and promotes apoptosis through a competitive endogenous RNA mechanism.","date":"2025","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/39843945","citation_count":1,"is_preprint":false},{"pmid":"41648143","id":"PMC_41648143","title":"NPEPPS segmental duplication drives position effect expression of TBC1D3 in the human brain.","date":"2026","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/41648143","citation_count":0,"is_preprint":false},{"pmid":"41371222","id":"PMC_41371222","title":"Puromycin-sensitive aminopeptidase acts as an inhibitory auxiliary subunit of volume-regulated anion channels and regulates cGAMP transport.","date":"2025","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/41371222","citation_count":0,"is_preprint":false},{"pmid":"41887507","id":"PMC_41887507","title":"Microbiota changes in rumen and milk corresponding to dietary protein intake in transition dairy cows.","date":"2026","source":"Journal of dairy science","url":"https://pubmed.ncbi.nlm.nih.gov/41887507","citation_count":0,"is_preprint":false},{"pmid":"32783359","id":"PMC_32783359","title":"Novel progressive acrodysostosis-like skeletal dysplasia, cerebellar atrophy, and ichthyosis.","date":"2020","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/32783359","citation_count":0,"is_preprint":false},{"pmid":"3603928","id":"PMC_3603928","title":"Separation of the 100-kDa membrane protein mediating ADP-induced platelet shape change and activation from glycoprotein IIIa.","date":"1986","source":"Transactions of the Association of American Physicians","url":"https://pubmed.ncbi.nlm.nih.gov/3603928","citation_count":0,"is_preprint":false},{"pmid":"42146573","id":"PMC_42146573","title":"Systematic Characterization of Thermal Stability Assay Parameters and Application in Discovery of Peptide-Protein Interactions.","date":"2026","source":"bioRxiv : the preprint server for biology","url":"https://pubmed.ncbi.nlm.nih.gov/42146573","citation_count":0,"is_preprint":false},{"pmid":"42136208","id":"PMC_42136208","title":"Integrating Multi-omics, Mendelian Randomization, and Experimental Validation to Unveil the Role of Traditional Chinese Medicine in Postmenopausal Osteoporosis.","date":"2026","source":"Current computer-aided drug design","url":"https://pubmed.ncbi.nlm.nih.gov/42136208","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":23726,"output_tokens":3357,"usd":0.060767,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10980,"output_tokens":3110,"usd":0.066325,"stage2_stop_reason":"end_turn"},"total_usd":0.127092,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"Puromycin-sensitive aminopeptidase (PSA/NPEPPS) directly proteolyzes tau protein in vitro, and PSA loss-of-function exacerbates tau-induced neurodegeneration in Drosophila while PSA gain-of-function protects against it, establishing PSA as an inhibitor of tau-induced neurodegeneration.\",\n      \"method\": \"In vitro proteolysis assay with purified human PSA and tau protein; Drosophila genetic loss-of-function and gain-of-function experiments with neurodegeneration phenotype readout\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct in vitro proteolysis assay combined with in vivo genetic epistasis in Drosophila, replicated in mammalian system by subsequent studies\",\n      \"pmids\": [\"16950154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PSA/NPEPPS overexpression in hPSA/TAU(P301L) double-transgenic mice significantly reduced total and hyperphosphorylated TAU levels in multiple brain regions, delayed paralysis, and improved motor neuron counts; knockdown of PSA/NPEPPS in SH-SY5Y neuroblastoma cells augmented endogenous TAU abundance, while overexpression reduced it, confirming in vivo TAU proteolysis.\",\n      \"method\": \"BAC-transgenic mouse cross with TAU(P301L) model; Western blot quantification of phospho-TAU; shRNA knockdown and overexpression in human neuroblastoma cells\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (transgenic mouse model, cell-based KD/OE), replicated in both in vivo and in vitro systems\",\n      \"pmids\": [\"21320871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PSA/NPEPPS directly regulates SOD1 protein abundance and clearance via proteolysis; PSA/NPEPPS expression is significantly decreased in motor neurons of SOD1G93A transgenic mice and sporadic ALS patients.\",\n      \"method\": \"In vitro proteolysis assay with PSA/NPEPPS and SOD1; Western blot quantification of SOD1 upon PSA overexpression/knockdown; immunohistochemistry of ALS patient tissue\",\n      \"journal\": \"Molecular neurodegeneration\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct proteolysis assay and cell-based KD/OE, single lab, two methods\",\n      \"pmids\": [\"21548977\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"MP100 (NPEPPS) was purified from human brain and characterized as a metalloprotease with broad substrate specificity that cleaves a beta-APP-derived peptide substrate in vitro, generating a cleavage product at the beta-site.\",\n      \"method\": \"Protein purification from human brain; in vitro enzymatic assay with chromogenic peptide substrate; molecular weight determination\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic assay with purified protein, single lab, single study\",\n      \"pmids\": [\"8198608\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"MP100 (NPEPPS) cDNA was cloned and found to be nearly identical to puromycin-sensitive aminopeptidase (PSA); recombinant human MP100 cleaved a free beta-site-spanning amyloid beta peptide (Aβ(-10/+10)) generating Aβ(1-10), but did not cleave N- and C-terminally blocked substrate or purified beta-APP; coexpression of MP100 with beta-APP695 did not increase Aβ levels in HEK cells; MP100 and beta-APP colocalized and co-immunoprecipitated from rat brain extracts.\",\n      \"method\": \"cDNA cloning; recombinant protein expression; in vitro peptide cleavage assay; co-immunoprecipitation from rat brain; double immunofluorescence in transfected HEK cells and neuroblastoma cells\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro cleavage assay plus co-IP, negative beta-secretase result rigorously established, single lab\",\n      \"pmids\": [\"10037494\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"MP100 (NPEPPS) localizes to synaptic sites in rat brain neurons, co-fractionates with presynaptic marker synaptophysin and beta-APP in synaptosomal membrane fractions, and shows punctate intracellular immunostaining consistent with vesicular structures, suggesting a role in proteolytic modification of synaptic proteins.\",\n      \"method\": \"Immunohistochemistry and immunoelectron microscopy of rat brain; gel filtration chromatography of synaptosomal membranes with co-fractionation analysis\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct subcellular localization by immunoelectron microscopy combined with biochemical co-fractionation, single lab\",\n      \"pmids\": [\"10434003\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PSA/NPEPPS mediates NRF2 signaling in hepatocytes by stabilizing NRF2 protein (suppressing NRF2 ubiquitination); PSA knockdown exacerbated diet-induced triglyceride accumulation through enhanced lipogenesis and attenuated fatty acid β-oxidation; liver-specific PSA overexpression attenuated hepatic lipid accumulation in ob/ob mice.\",\n      \"method\": \"shRNA knockdown and adeno-associated virus-mediated overexpression in hepatocytes and ob/ob mice; Western blot for NRF2 and ubiquitination; lipid accumulation assays\",\n      \"journal\": \"Journal of molecular cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD/OE with defined cellular and in vivo phenotype, NRF2 ubiquitination assay, single lab\",\n      \"pmids\": [\"34048566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NPEPPS drives cisplatin resistance by regulating intracellular cisplatin concentrations; NPEPPS depletion sensitized resistant bladder cancer cells to cisplatin in vitro and in vivo, and in patient-derived organoids; NPEPPS overexpression in sensitive cells increased cisplatin resistance.\",\n      \"method\": \"Whole-genome CRISPR screen; KD/KO and overexpression in bladder cancer cell lines; in vivo xenograft experiments; patient-derived organoid cisplatin sensitivity assays; intracellular cisplatin concentration measurement\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — CRISPR screen plus reciprocal gain/loss-of-function with defined molecular readout (intracellular drug concentration), validated in vivo and in PDOs\",\n      \"pmids\": [\"38535994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PSA/NPEPPS physically binds the obligatory VRAC subunit SWELL1 (LRRC8A); cryo-EM structure shows three PSA molecules binding a single SWELL1 hexamer, coupling adjacent leucine-rich repeat domains into local dimers; PSA overexpression suppresses VRAC activation, PSA deletion dramatically elevates basal VRAC channel activity; PSA modulation of VRACs requires physical binding but not aminopeptidase catalytic activity, indicating a structural (non-enzymatic) mechanism; PSA/NPEPPS also modulates cGAMP transport through VRACs.\",\n      \"method\": \"Cryo-electron microscopy structure determination; co-immunoprecipitation; overexpression and genetic deletion with electrophysiological VRAC activity readout; aminopeptidase-dead mutant functional assay; cGAMP transport assay\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structure combined with mutagenesis (catalytic dead mutant), electrophysiology, and genetic deletion, multiple orthogonal methods in single rigorous study\",\n      \"pmids\": [\"41371222\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NPEPPS interacts with volume-regulated anion channels (VRACs) to control cisplatin import into cells; NPEPPS/VRAC gene expression ratio is a predictive measure of cisplatin response across multiple cancer types; pharmacologic inhibition of NPEPPS increased cisplatin sensitivity in patient-derived organoids.\",\n      \"method\": \"Interaction studies between NPEPPS and VRAC subunits; cisplatin uptake assays; gene expression ratio analysis in cancer cohorts; PDO pharmacologic inhibition experiments\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — mechanistic interaction with VRACs established with cisplatin import as functional readout, validated in PDOs and multiple cancer cohorts, extends prior CRISPR study\",\n      \"pmids\": [\"39671496\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Puromycin selectively inhibits PSA/NPEPPS among M1 family aminopeptidases; structural and biochemical analysis showed puromycin does not enter the active site but binds near the entrance to block substrate access; other M1 enzymes hydrolyze puromycin as a substrate rather than being inhibited by it.\",\n      \"method\": \"In vitro enzymatic assays with four M1 family enzymes; X-ray crystallography of ePepN with puromycin (wild-type and E298A mutant); molecular modeling of PSA active site\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with active-site mutant combined with biochemical assay, mechanistic selectivity fully established, single lab\",\n      \"pmids\": [\"33045297\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"NPEPPS (PSA) is a predominantly cytoplasmic zinc-dependent exopeptidase; the gene was physically mapped to chromosome 17q21.2→q21.32 by fluorescence in situ hybridization, and a polymorphism at amino acid position 140 was identified.\",\n      \"method\": \"Fluorescence in situ hybridization (FISH); sequencing of coding region; tissue distribution analysis\",\n      \"journal\": \"Cytogenetics and cell genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — direct chromosomal localization by FISH, subcellular localization stated but not experimentally detailed in abstract, single lab\",\n      \"pmids\": [\"11435692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"NPEPPS acts as a binding partner of angiotensin II, a key vasoactive peptide hormone, as identified by PISA thermal stability assay, representing a previously uncharacterized peptide-protein interaction.\",\n      \"method\": \"Proteome integral solubility alteration (PISA) assay / thermal proteome profiling with TMT-based multiplexing\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single thermal shift assay method, preprint, no functional validation of the interaction reported in abstract\",\n      \"pmids\": [\"42146573\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"NPEPPS (PSA/MP100) is a cytoplasmic zinc-dependent M1-family metalloaminopeptidase that proteolyzes neurotoxic substrates including tau and SOD1 to protect against neurodegeneration; acts as a structural (non-catalytic) inhibitory auxiliary subunit of volume-regulated anion channels (VRACs) by physically binding SWELL1 hexamers to suppress channel activation and control intracellular cisplatin concentrations; stabilizes NRF2 by suppressing its ubiquitination to regulate hepatic lipid metabolism; and is selectively inhibited by puromycin through an active-site-blocking mechanism distinct from substrate hydrolysis.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"NPEPPS (PSA/MP100) is a predominantly cytoplasmic, zinc-dependent M1-family metalloaminopeptidase that proteolytically clears neurotoxic substrates and thereby protects against neurodegeneration [#0, #11]. It directly proteolyzes tau in vitro, and its activity is protective in vivo: PSA loss exacerbates and PSA gain suppresses tau-induced neurodegeneration in Drosophila, while PSA overexpression in TAU(P301L) mice lowers total and hyperphosphorylated tau, delays paralysis, and preserves motor neurons [#0, #1]. PSA likewise regulates the abundance and clearance of SOD1, and its expression is reduced in motor neurons of SOD1G93A mice and sporadic ALS patients [#2]. Beyond its catalytic role, NPEPPS has a distinct non-enzymatic function as a structural inhibitory partner of the volume-regulated anion channel (VRAC): cryo-EM shows three PSA molecules clamping a single SWELL1 (LRRC8A) hexamer to couple adjacent leucine-rich-repeat domains, and PSA suppresses basal VRAC activation through physical binding that does not require aminopeptidase activity [#8]. Through this VRAC interaction NPEPPS controls intracellular cisplatin concentrations, driving cisplatin resistance such that its depletion or pharmacologic inhibition resensitizes resistant bladder cancer cells, xenografts, and patient-derived organoids, with the NPEPPS/VRAC expression ratio predicting cisplatin response across cancers [#7, #9]. NPEPPS also stabilizes NRF2 by suppressing its ubiquitination in hepatocytes, restraining diet-induced hepatic lipid accumulation [#6]. Puromycin selectively inhibits NPEPPS by binding near the active-site entrance to block substrate access rather than being hydrolyzed [#10].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"Established the basic biochemical identity of the protein, showing that brain-derived MP100 is a broad-specificity metalloprotease, the founding observation of its enzymatic character.\",\n      \"evidence\": \"Protein purification from human brain with in vitro chromogenic peptide assay\",\n      \"pmids\": [\"8198608\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological substrates not defined\", \"Subcellular compartment not resolved\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Linked MP100 to PSA at the sequence level and tested an amyloidogenic role, resolving whether the enzyme acts as a beta-secretase by showing it cleaves free Abeta-spanning peptides but not intact beta-APP.\",\n      \"evidence\": \"cDNA cloning, recombinant peptide cleavage assays, co-IP and colocalization with beta-APP in rat brain and HEK/neuroblastoma cells; synaptic localization by immunoelectron microscopy and synaptosomal co-fractionation\",\n      \"pmids\": [\"10037494\", \"10434003\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No beta-secretase activity on native substrate\", \"Functional significance of synaptic localization untested\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined NPEPPS as a cytoplasmic zinc-dependent exopeptidase and mapped the gene, providing genetic and compartmental grounding.\",\n      \"evidence\": \"FISH chromosomal mapping and coding-region sequencing\",\n      \"pmids\": [\"11435692\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of the position-140 polymorphism unknown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identified tau as a direct proteolytic substrate and demonstrated a protective role against neurodegeneration, establishing NPEPPS as a modifier of tauopathy.\",\n      \"evidence\": \"In vitro proteolysis of tau plus Drosophila loss/gain-of-function neurodegeneration assays\",\n      \"pmids\": [\"16950154\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cleavage sites on tau not mapped\", \"Regulation of PSA activity in neurons unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Extended the neuroprotective tau model to mammals and added SOD1 as a substrate, broadening NPEPPS into a clearance factor for multiple neurodegeneration-associated proteins.\",\n      \"evidence\": \"TAU(P301L) transgenic mouse crosses with phospho-TAU quantification, cell KD/OE; in vitro SOD1 proteolysis with KD/OE and ALS tissue immunohistochemistry\",\n      \"pmids\": [\"21320871\", \"21548977\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether reduced PSA causes or follows ALS pathology unresolved\", \"SOD1 evidence from a single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Revealed a non-proteolytic regulatory function in metabolism, showing NPEPPS stabilizes NRF2 to restrain hepatic lipid accumulation.\",\n      \"evidence\": \"Hepatocyte and ob/ob mouse KD/OE with NRF2 ubiquitination and lipid assays\",\n      \"pmids\": [\"34048566\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which NPEPPS suppresses NRF2 ubiquitination unknown\", \"Whether catalytic activity is required untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Connected NPEPPS to chemoresistance, establishing that it controls intracellular cisplatin levels via VRAC interaction and serves as a predictive biomarker and therapeutic target.\",\n      \"evidence\": \"Whole-genome CRISPR screen, reciprocal KD/KO/OE with intracellular cisplatin measurement, xenografts, PDOs, and NPEPPS/VRAC expression-ratio analysis across cancer cohorts\",\n      \"pmids\": [\"38535994\", \"39671496\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of VRAC regulation not yet structural\", \"Whether catalytic activity contributes to cisplatin handling unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided the structural and mechanistic basis for NPEPPS as a non-enzymatic VRAC subunit, showing physical clamping of SWELL1 hexamers suppresses channel activity independent of aminopeptidase function.\",\n      \"evidence\": \"Cryo-EM of the PSA–SWELL1 complex, co-IP, electrophysiology with overexpression/deletion, catalytic-dead mutant, and cGAMP transport assays\",\n      \"pmids\": [\"41371222\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How VRAC binding integrates with cytoplasmic proteolytic roles unknown\", \"Physiological triggers governing PSA–VRAC stoichiometry undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown whether NPEPPS engages additional regulatory peptides such as angiotensin II and how its dual catalytic and structural-scaffold roles are partitioned in vivo.\",\n      \"evidence\": \"PISA thermal stability assay identifying angiotensin II binding (preprint, no functional validation)\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Angiotensin II interaction from a single thermal-shift assay, not functionally validated\", \"No integrated model reconciling proteolytic, NRF2-stabilizing, and VRAC-scaffold functions\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 2, 3, 4]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [3, 11]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [6, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 1, 2]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [7, 8, 9]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [7, 9]}\n    ],\n    \"complexes\": [\"VRAC (SWELL1/LRRC8A channel)\"],\n    \"partners\": [\"LRRC8A\", \"MAPT\", \"SOD1\", \"NFE2L2\", \"APP\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}