{"gene":"TPP2","run_date":"2026-04-28T21:42:59","timeline":{"discoveries":[{"year":2004,"finding":"TPPII acts downstream of the proteasome in antigen processing, utilizing both endoproteolytic and exoproteolytic activities to process proteasome-released peptides, contributing to MHC class I epitope generation or destruction.","method":"Biochemical analysis, functional review integrating multiple studies","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 — replicated across multiple labs with functional assays, established paradigm","pmids":["15224091"],"is_preprint":false},{"year":2007,"finding":"TPPII plays a predominantly destructive role in MHC class I antigen processing; TPPII-deficient mice show increased surface MHC class I-peptide complexes and delayed degradation of OVA epitope peptides in cytosolic extracts, and TPPII is not induced by IFN-γ.","method":"TPPII knockout mouse analysis, cell surface MHC I quantification, cytosolic extract peptide degradation assay, dendritic cell cross-presentation assay","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with multiple orthogonal functional readouts","pmids":["18056356"],"is_preprint":false},{"year":2008,"finding":"TPPII deficiency activates cell type-specific death programs including proliferative apoptosis in T cell subsets and premature cellular senescence in fibroblasts and CD8+ T cells, coinciding with upregulation of p53 and dysregulation of NF-κB.","method":"TPPII knockout mouse, flow cytometry, apoptosis and senescence assays, p53 and NF-κB expression analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with multiple cellular phenotype readouts and molecular markers","pmids":["18362329"],"is_preprint":false},{"year":2017,"finding":"In situ cryo-electron tomography of rat hippocampal neurons revealed that TPPII forms two assembly states (36-mers and 32-mers) as well as extended forms in vivo, and spatially associates with 26S proteasomes consistent with its postproteasomal degradation role.","method":"Cryo-electron tomography with Volta phase plate, template matching, distance analysis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 — in situ structural determination with quantitative spatial analysis","pmids":["28396430"],"is_preprint":false},{"year":2006,"finding":"TPPII overexpression shortens mitosis duration, allows cells to evade mitotic arrest induced by spindle poisons, promotes polyploidy despite functional spindle checkpoint components, and correlates with upregulation of IAPs and resistance to mitochondria-dependent apoptosis triggered by p53 stabilization; TPPII knockdown by shRNA slows cell growth and causes mitotic delay.","method":"TPPII overexpression in HEK293 cells, shRNA knockdown, cell cycle analysis, spindle poison treatment, apoptosis assays, IAP expression analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — KD and OE with multiple functional readouts in single lab","pmids":["16762321"],"is_preprint":false},{"year":2014,"finding":"TPPII physically interacts with tumor suppressor MYBBP1A and cell cycle regulator CDK2; the TPPII-MYBBP1A interaction is enzymatic-activity dependent (suppressed by butabindide inhibitor) and increases with TPPII expression and serum-free conditions; TPPII overexpression decreases MYBBP1A mRNA during anoikis.","method":"Co-immunoprecipitation, in situ proximity ligation assay (PLA) in HEK293 cells, TPPII inhibitor (butabindide), gene expression analysis","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP and PLA in single lab with inhibitor validation","pmids":["25303791"],"is_preprint":false},{"year":2015,"finding":"TPPII physically interacts with p53 and SIRT7 in cytoplasm and nucleus, as detected in HeLa cell lysates and mouse liver cytoplasmic fractions; these interactions occur in both high-activity (murine) and low-activity (human) TPPII-expressing cells.","method":"Co-immunoprecipitation from HeLa lysates and mouse liver fractions, in situ proximity ligation assay (PLA) in HEK293 cells, immunofluorescence","journal":"Molecular and cellular biochemistry","confidence":"Low","confidence_rationale":"Tier 3 — single lab, Co-IP and PLA without functional mechanistic follow-up","pmids":["26169984"],"is_preprint":false},{"year":2018,"finding":"A homozygous missense mutation (p.Cys28Gly) in TPP2 reduces TPP2 protein expression and enzymatic activity in patient blood cells, causing sterile brain inflammation; enzymatic activity assays confirmed loss-of-function.","method":"Next-generation sequencing, enzymatic activity assay, protein expression studies in patient samples","journal":"Neurology. Genetics","confidence":"Medium","confidence_rationale":"Tier 2 — patient mutation with enzymatic activity validation","pmids":["30533531"],"is_preprint":false},{"year":2018,"finding":"TPPII is diffusely distributed in the cytoplasm under normal conditions, but upon proteasome inhibition is dynamically recruited to the perinuclear region and into aggresomal structures, where it forms a spherical mantle surrounding the core of proteasomes and polyubiquitinated proteins.","method":"Fluorescent proteasome inhibitor (BSc2118), laser scanning confocal microscopy, co-immunostaining in C26 murine colon adenocarcinoma cells","journal":"Histology and histopathology","confidence":"Medium","confidence_rationale":"Tier 2 — direct localization imaging with functional context (proteasome inhibition)","pmids":["30226264"],"is_preprint":false}],"current_model":"TPP2 is a giant cytosolic serine exo/endopeptidase that assembles into ~6 MDa spindle-shaped oligomeric complexes (36-mers and 32-mers in vivo), acts downstream of the 26S proteasome by removing tripeptides from proteasomal degradation products, spatially associates with proteasomes, plays a predominantly destructive role in MHC class I antigen processing, supports cellular viability by preventing apoptosis and senescence (partly via p53 and NF-κB regulation), enables mitotic exit, and interacts with proteins including p53, SIRT7, MYBBP1A, and CDK2."},"narrative":{"teleology":[{"year":2004,"claim":"Establishing that TPP2 operates downstream of the proteasome using both endo- and exopeptidase activities to process proteasomal products resolved where TPP2 sits in the intracellular proteolytic cascade and linked it to MHC class I epitope generation and destruction.","evidence":"Biochemical analysis and integration of multiple functional studies across labs","pmids":["15224091"],"confidence":"High","gaps":["Relative contribution of endopeptidase versus exopeptidase activity to epitope generation not delineated","No structural basis for dual catalytic modes"]},{"year":2006,"claim":"Demonstrating that TPP2 overexpression shortens mitosis, enables evasion of spindle checkpoint arrest, and promotes polyploidy while knockdown causes mitotic delay established a non-proteolytic-pathway role for TPP2 in cell cycle progression and apoptosis resistance.","evidence":"Overexpression and shRNA knockdown in HEK293 cells with cell cycle analysis, spindle poison treatment, and IAP expression analysis","pmids":["16762321"],"confidence":"Medium","gaps":["Mechanism by which TPP2 promotes mitotic exit is unknown","Relevance of IAP upregulation to TPP2 catalytic activity not tested","Single cell line studied"]},{"year":2007,"claim":"Genetic knockout in mice showed TPP2 predominantly destroys rather than generates MHC class I epitopes, reversing earlier models that emphasized a generative role and clarifying TPP2's net contribution to antigen processing.","evidence":"TPP2 knockout mouse with surface MHC I quantification, cytosolic peptide degradation assays, and dendritic cell cross-presentation assays","pmids":["18056356"],"confidence":"High","gaps":["Epitope-specific effects not fully catalogued","Whether TPP2 contributes to generation of specific epitopes in some contexts remains unresolved"]},{"year":2008,"claim":"TPP2 deficiency was shown to trigger cell type–specific apoptosis and senescence programs linked to p53 and NF-κB dysregulation, establishing TPP2 as a pro-survival factor beyond its peptide-trimming role.","evidence":"TPP2 knockout mouse with flow cytometry, apoptosis/senescence assays, and p53/NF-κB expression analysis","pmids":["18362329"],"confidence":"High","gaps":["Direct substrate(s) whose accumulation triggers p53 upregulation not identified","Whether the viability defect is catalytic-activity-dependent was not dissected"]},{"year":2014,"claim":"Identification of MYBBP1A and CDK2 as physical interactors of TPP2—with the MYBBP1A interaction being activity-dependent—provided the first molecular links connecting TPP2's enzymatic function to tumor suppression and cell cycle regulation pathways.","evidence":"Co-immunoprecipitation and in situ proximity ligation assay in HEK293 cells with butabindide inhibitor","pmids":["25303791"],"confidence":"Medium","gaps":["Functional consequences of MYBBP1A and CDK2 interactions on cell cycle not established","Whether MYBBP1A is a substrate or regulatory partner is unknown","Single lab without reciprocal genetic validation"]},{"year":2015,"claim":"Detection of physical complexes between TPP2, p53, and SIRT7 in both cytoplasm and nucleus suggested a direct mechanism by which TPP2 could regulate p53 stability or activity.","evidence":"Co-immunoprecipitation from HeLa lysates and mouse liver fractions, PLA in HEK293 cells","pmids":["26169984"],"confidence":"Low","gaps":["No functional follow-up demonstrating that the interaction modulates p53 activity or stability","Single lab without reciprocal IP or genetic perturbation","Stoichiometry and directness of the ternary complex unclear"]},{"year":2017,"claim":"In situ cryo-ET visualization of TPP2 oligomeric states (36-mers and 32-mers) and their spatial proximity to 26S proteasomes in intact neurons provided the first native structural evidence for a postproteasomal processing relay.","evidence":"Cryo-electron tomography with Volta phase plate and template matching in rat hippocampal neurons","pmids":["28396430"],"confidence":"High","gaps":["Whether spatial proximity reflects direct physical contact or functional coupling is unresolved","Regulation of interconversion between 36-mer and 32-mer states unknown"]},{"year":2018,"claim":"A homozygous TPP2 missense mutation (p.Cys28Gly) confirmed as loss-of-function in patient cells established TPP2 deficiency as a cause of sterile brain inflammation, linking the enzyme to neuroinflammatory disease in humans.","evidence":"Next-generation sequencing with enzymatic activity assay and protein expression studies in patient blood cells","pmids":["30533531"],"confidence":"Medium","gaps":["Mechanism by which TPP2 loss triggers neuroinflammation not determined","Single family—genetic confirmation in additional kindreds needed"]},{"year":2018,"claim":"Demonstrating that TPP2 redistributes from diffuse cytoplasmic localization to a perinuclear aggresomal mantle upon proteasome inhibition revealed a dynamic spatial relationship between TPP2 and the proteasome under proteotoxic stress.","evidence":"Confocal microscopy with fluorescent proteasome inhibitor and co-immunostaining in C26 murine colon adenocarcinoma cells","pmids":["30226264"],"confidence":"Medium","gaps":["Whether aggresomal recruitment is functionally protective or a consequence of substrate accumulation is unknown","Signals mediating TPP2 relocalization not identified"]},{"year":null,"claim":"The direct substrates whose accumulation upon TPP2 loss triggers p53 upregulation, apoptosis, senescence, and neuroinflammation remain unidentified, and the catalytic versus non-catalytic contributions of TPP2 to its pro-survival and cell cycle functions have not been dissected.","evidence":"","pmids":[],"confidence":"High","gaps":["No substrate identification linking TPP2 loss to p53/NF-κB dysregulation","Catalytic versus scaffolding functions not separated genetically","Structural basis for oligomeric state regulation and its functional consequences unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,3,7]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,6,8]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1]},{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,3]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[2,4]}],"complexes":[],"partners":["MYBBP1A","CDK2","TP53","SIRT7"],"other_free_text":[]},"mechanistic_narrative":"TPP2 encodes a giant cytosolic serine peptidase that assembles into ~6 MDa oligomeric complexes (36-mers and 32-mers) and functions downstream of the 26S proteasome by removing tripeptides from proteasomal degradation products, spatially associating with proteasomes in situ and being recruited to aggresomes upon proteasome inhibition [PMID:28396430, PMID:30226264]. In MHC class I antigen processing, TPP2 plays a predominantly destructive role: TPP2-deficient mice display increased surface MHC I–peptide complexes and delayed cytosolic epitope degradation [PMID:18056356]. TPP2 deficiency activates cell type–specific death programs—proliferative apoptosis in T cells and premature senescence in fibroblasts—coinciding with p53 upregulation and NF-κB dysregulation, while TPP2 overexpression promotes mitotic exit and resistance to apoptosis [PMID:18362329, PMID:16762321]. A homozygous loss-of-function missense mutation (p.Cys28Gly) in TPP2 causes sterile brain inflammation in humans [PMID:30533531]."},"prefetch_data":{"uniprot":{"accession":"P29144","full_name":"Tripeptidyl-peptidase 2","aliases":["Tripeptidyl aminopeptidase","Tripeptidyl-peptidase II","TPP-II"],"length_aa":1249,"mass_kda":138.3,"function":"Cytosolic tripeptidyl-peptidase that releases N-terminal tripeptides from polypeptides and is a component of the proteolytic cascade acting downstream of the 26S proteasome in the ubiquitin-proteasome pathway (PubMed:25525876, PubMed:30533531). It plays an important role in intracellular amino acid homeostasis (PubMed:25525876). Stimulates adipogenesis (By similarity)","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/P29144/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TPP2","classification":"Not Classified","n_dependent_lines":3,"n_total_lines":1208,"dependency_fraction":0.0024834437086092716},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SNX2","stoichiometry":4.0},{"gene":"CAPZB","stoichiometry":0.2},{"gene":"EIF3B","stoichiometry":0.2},{"gene":"HDAC2","stoichiometry":0.2},{"gene":"PSPC1","stoichiometry":0.2},{"gene":"SCYL2","stoichiometry":0.2},{"gene":"TERF2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/TPP2","total_profiled":1310},"omim":[{"mim_id":"619220","title":"IMMUNODEFICIENCY 78 WITH AUTOIMMUNITY AND DEVELOPMENTAL DELAY; IMD78","url":"https://www.omim.org/entry/619220"},{"mim_id":"609497","title":"ENDOPLASMIC RETICULUM AMINOPEPTIDASE 2; ERAP2","url":"https://www.omim.org/entry/609497"},{"mim_id":"190470","title":"TRIPEPTIDYL PEPTIDASE II; TPP2","url":"https://www.omim.org/entry/190470"},{"mim_id":"126200","title":"MULTIPLE SCLEROSIS, SUSCEPTIBILITY TO; MS","url":"https://www.omim.org/entry/126200"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nuclear bodies","reliability":"Supported"},{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/TPP2"},"hgnc":{"alias_symbol":["TPPII"],"prev_symbol":[]},"alphafold":{"accession":"P29144","domains":[{"cath_id":"3.40.50.200","chopping":"19-66_259-515","consensus_level":"high","plddt":96.2952,"start":19,"end":515},{"cath_id":"-","chopping":"76-122_192-258","consensus_level":"medium","plddt":95.0796,"start":76,"end":258},{"cath_id":"2.60.120.380","chopping":"636-753","consensus_level":"medium","plddt":94.643,"start":636,"end":753},{"cath_id":"2.60.40","chopping":"761-791_915-992","consensus_level":"medium","plddt":93.124,"start":761,"end":992},{"cath_id":"-","chopping":"799-906","consensus_level":"medium","plddt":95.9971,"start":799,"end":906},{"cath_id":"1.25.40.710","chopping":"1018-1139_1159-1192","consensus_level":"high","plddt":87.1873,"start":1018,"end":1192},{"cath_id":"1.10.287","chopping":"124-186","consensus_level":"medium","plddt":92.3341,"start":124,"end":186}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P29144","model_url":"https://alphafold.ebi.ac.uk/files/AF-P29144-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P29144-F1-predicted_aligned_error_v6.png","plddt_mean":91.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TPP2","jax_strain_url":"https://www.jax.org/strain/search?query=TPP2"},"sequence":{"accession":"P29144","fasta_url":"https://rest.uniprot.org/uniprotkb/P29144.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P29144/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P29144"}},"corpus_meta":[{"pmid":"15224091","id":"PMC_15224091","title":"Generation of major histocompatibility complex class I antigens: functional interplay between proteasomes and TPPII.","date":"2004","source":"Nature immunology","url":"https://pubmed.ncbi.nlm.nih.gov/15224091","citation_count":178,"is_preprint":false},{"pmid":"18056356","id":"PMC_18056356","title":"Analysis of direct and cross-presentation of antigens in TPPII knockout mice.","date":"2007","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/18056356","citation_count":33,"is_preprint":false},{"pmid":"18362329","id":"PMC_18362329","title":"Activation of cellular death programs associated with immunosenescence-like phenotype in TPPII knockout mice.","date":"2008","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/18362329","citation_count":33,"is_preprint":false},{"pmid":"28396430","id":"PMC_28396430","title":"In situ structural studies of tripeptidyl peptidase II (TPPII) reveal spatial association with proteasomes.","date":"2017","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/28396430","citation_count":24,"is_preprint":false},{"pmid":"26169984","id":"PMC_26169984","title":"Novel protein-protein interactions of TPPII, p53, and SIRT7.","date":"2015","source":"Molecular and cellular biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26169984","citation_count":22,"is_preprint":false},{"pmid":"16762321","id":"PMC_16762321","title":"TPPII promotes genetic instability by allowing the escape from apoptosis of cells with activated mitotic checkpoints.","date":"2006","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/16762321","citation_count":21,"is_preprint":false},{"pmid":"7908839","id":"PMC_7908839","title":"Assignment of the linkage group EAM-TYRP2-TPP2 to chromosome 11 in pigs by in situ hybridization mapping of the TPP2 gene.","date":"1993","source":"Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology","url":"https://pubmed.ncbi.nlm.nih.gov/7908839","citation_count":13,"is_preprint":false},{"pmid":"25303791","id":"PMC_25303791","title":"TPPII, MYBBP1A and CDK2 form a protein-protein interaction network.","date":"2014","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/25303791","citation_count":7,"is_preprint":false},{"pmid":"19539606","id":"PMC_19539606","title":"Viability and DNA damage responses of TPPII-deficient Myc- and Ras-transformed fibroblasts.","date":"2009","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/19539606","citation_count":7,"is_preprint":false},{"pmid":"30533531","id":"PMC_30533531","title":"TPP2 mutation associated with sterile brain inflammation mimicking MS.","date":"2018","source":"Neurology. Genetics","url":"https://pubmed.ncbi.nlm.nih.gov/30533531","citation_count":7,"is_preprint":false},{"pmid":"33586135","id":"PMC_33586135","title":"Immune deficiency, autoimmune disease and intellectual disability: A pleiotropic disorder caused by biallelic variants in the TPP2 gene.","date":"2021","source":"Clinical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/33586135","citation_count":6,"is_preprint":false},{"pmid":"8406500","id":"PMC_8406500","title":"Localization of the human tripeptidyl peptidase II gene (TPP2) to 13q32-q33 by nonradioactive in situ hybridization and somatic cell hybrids.","date":"1993","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/8406500","citation_count":5,"is_preprint":false},{"pmid":"34902200","id":"PMC_34902200","title":"Adenovirus vector encoding TPPII ignites HBV-specific CTL response by activating autophagy in CD8+ T cell.","date":"2022","source":"Journal of viral hepatitis","url":"https://pubmed.ncbi.nlm.nih.gov/34902200","citation_count":3,"is_preprint":false},{"pmid":"32702546","id":"PMC_32702546","title":"Linking TPPII to the protein interaction and signalling networks.","date":"2020","source":"Computational biology and chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/32702546","citation_count":2,"is_preprint":false},{"pmid":"30294774","id":"PMC_30294774","title":"Semispecific TPPII inhibitor Ala-Ala-Phe-chloromethylketone (AAF-cmk) displays cytotoxic activity by induction of apoptosis, autophagy and protein aggregation in U937 cells.","date":"2018","source":"Folia histochemica et cytobiologica","url":"https://pubmed.ncbi.nlm.nih.gov/30294774","citation_count":2,"is_preprint":false},{"pmid":"16822484","id":"PMC_16822484","title":"Overlapping regional distribution of CCK and TPPII mRNAs in Cynomolgus monkey brain and correlated levels in human cerebral cortex (BA 10).","date":"2006","source":"Brain research","url":"https://pubmed.ncbi.nlm.nih.gov/16822484","citation_count":2,"is_preprint":false},{"pmid":"30226264","id":"PMC_30226264","title":"Changes in spatio-temporal localization of tripeptidyl peptidase II (TPPII) in murine colon adenocarcinoma cells during aggresome formation: a microscopy study based on a novel fluorescent proteasome inhibitor.","date":"2018","source":"Histology and histopathology","url":"https://pubmed.ncbi.nlm.nih.gov/30226264","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":9090,"output_tokens":2000,"usd":0.028635},"stage2":{"model":"claude-opus-4-6","input_tokens":5300,"output_tokens":2420,"usd":0.1305},"total_usd":0.159135,"stage1_batch_id":"msgbatch_01RPbVc9PDH9zQmYK5Hs6srm","stage2_batch_id":"msgbatch_01JVbVLzeKN2yVrsGp3zC8aM","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"TPPII acts downstream of the proteasome in antigen processing, utilizing both endoproteolytic and exoproteolytic activities to process proteasome-released peptides, contributing to MHC class I epitope generation or destruction.\",\n      \"method\": \"Biochemical analysis, functional review integrating multiple studies\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — replicated across multiple labs with functional assays, established paradigm\",\n      \"pmids\": [\"15224091\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"TPPII plays a predominantly destructive role in MHC class I antigen processing; TPPII-deficient mice show increased surface MHC class I-peptide complexes and delayed degradation of OVA epitope peptides in cytosolic extracts, and TPPII is not induced by IFN-γ.\",\n      \"method\": \"TPPII knockout mouse analysis, cell surface MHC I quantification, cytosolic extract peptide degradation assay, dendritic cell cross-presentation assay\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with multiple orthogonal functional readouts\",\n      \"pmids\": [\"18056356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"TPPII deficiency activates cell type-specific death programs including proliferative apoptosis in T cell subsets and premature cellular senescence in fibroblasts and CD8+ T cells, coinciding with upregulation of p53 and dysregulation of NF-κB.\",\n      \"method\": \"TPPII knockout mouse, flow cytometry, apoptosis and senescence assays, p53 and NF-κB expression analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with multiple cellular phenotype readouts and molecular markers\",\n      \"pmids\": [\"18362329\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In situ cryo-electron tomography of rat hippocampal neurons revealed that TPPII forms two assembly states (36-mers and 32-mers) as well as extended forms in vivo, and spatially associates with 26S proteasomes consistent with its postproteasomal degradation role.\",\n      \"method\": \"Cryo-electron tomography with Volta phase plate, template matching, distance analysis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in situ structural determination with quantitative spatial analysis\",\n      \"pmids\": [\"28396430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"TPPII overexpression shortens mitosis duration, allows cells to evade mitotic arrest induced by spindle poisons, promotes polyploidy despite functional spindle checkpoint components, and correlates with upregulation of IAPs and resistance to mitochondria-dependent apoptosis triggered by p53 stabilization; TPPII knockdown by shRNA slows cell growth and causes mitotic delay.\",\n      \"method\": \"TPPII overexpression in HEK293 cells, shRNA knockdown, cell cycle analysis, spindle poison treatment, apoptosis assays, IAP expression analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD and OE with multiple functional readouts in single lab\",\n      \"pmids\": [\"16762321\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TPPII physically interacts with tumor suppressor MYBBP1A and cell cycle regulator CDK2; the TPPII-MYBBP1A interaction is enzymatic-activity dependent (suppressed by butabindide inhibitor) and increases with TPPII expression and serum-free conditions; TPPII overexpression decreases MYBBP1A mRNA during anoikis.\",\n      \"method\": \"Co-immunoprecipitation, in situ proximity ligation assay (PLA) in HEK293 cells, TPPII inhibitor (butabindide), gene expression analysis\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP and PLA in single lab with inhibitor validation\",\n      \"pmids\": [\"25303791\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"TPPII physically interacts with p53 and SIRT7 in cytoplasm and nucleus, as detected in HeLa cell lysates and mouse liver cytoplasmic fractions; these interactions occur in both high-activity (murine) and low-activity (human) TPPII-expressing cells.\",\n      \"method\": \"Co-immunoprecipitation from HeLa lysates and mouse liver fractions, in situ proximity ligation assay (PLA) in HEK293 cells, immunofluorescence\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, Co-IP and PLA without functional mechanistic follow-up\",\n      \"pmids\": [\"26169984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A homozygous missense mutation (p.Cys28Gly) in TPP2 reduces TPP2 protein expression and enzymatic activity in patient blood cells, causing sterile brain inflammation; enzymatic activity assays confirmed loss-of-function.\",\n      \"method\": \"Next-generation sequencing, enzymatic activity assay, protein expression studies in patient samples\",\n      \"journal\": \"Neurology. Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — patient mutation with enzymatic activity validation\",\n      \"pmids\": [\"30533531\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"TPPII is diffusely distributed in the cytoplasm under normal conditions, but upon proteasome inhibition is dynamically recruited to the perinuclear region and into aggresomal structures, where it forms a spherical mantle surrounding the core of proteasomes and polyubiquitinated proteins.\",\n      \"method\": \"Fluorescent proteasome inhibitor (BSc2118), laser scanning confocal microscopy, co-immunostaining in C26 murine colon adenocarcinoma cells\",\n      \"journal\": \"Histology and histopathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct localization imaging with functional context (proteasome inhibition)\",\n      \"pmids\": [\"30226264\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TPP2 is a giant cytosolic serine exo/endopeptidase that assembles into ~6 MDa spindle-shaped oligomeric complexes (36-mers and 32-mers in vivo), acts downstream of the 26S proteasome by removing tripeptides from proteasomal degradation products, spatially associates with proteasomes, plays a predominantly destructive role in MHC class I antigen processing, supports cellular viability by preventing apoptosis and senescence (partly via p53 and NF-κB regulation), enables mitotic exit, and interacts with proteins including p53, SIRT7, MYBBP1A, and CDK2.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TPP2 encodes a giant cytosolic serine peptidase that assembles into ~6 MDa oligomeric complexes (36-mers and 32-mers) and functions downstream of the 26S proteasome by removing tripeptides from proteasomal degradation products, spatially associating with proteasomes in situ and being recruited to aggresomes upon proteasome inhibition [PMID:28396430, PMID:30226264]. In MHC class I antigen processing, TPP2 plays a predominantly destructive role: TPP2-deficient mice display increased surface MHC I–peptide complexes and delayed cytosolic epitope degradation [PMID:18056356]. TPP2 deficiency activates cell type–specific death programs—proliferative apoptosis in T cells and premature senescence in fibroblasts—coinciding with p53 upregulation and NF-κB dysregulation, while TPP2 overexpression promotes mitotic exit and resistance to apoptosis [PMID:18362329, PMID:16762321]. A homozygous loss-of-function missense mutation (p.Cys28Gly) in TPP2 causes sterile brain inflammation in humans [PMID:30533531].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Establishing that TPP2 operates downstream of the proteasome using both endo- and exopeptidase activities to process proteasomal products resolved where TPP2 sits in the intracellular proteolytic cascade and linked it to MHC class I epitope generation and destruction.\",\n      \"evidence\": \"Biochemical analysis and integration of multiple functional studies across labs\",\n      \"pmids\": [\"15224091\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Relative contribution of endopeptidase versus exopeptidase activity to epitope generation not delineated\",\n        \"No structural basis for dual catalytic modes\"\n      ]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Demonstrating that TPP2 overexpression shortens mitosis, enables evasion of spindle checkpoint arrest, and promotes polyploidy while knockdown causes mitotic delay established a non-proteolytic-pathway role for TPP2 in cell cycle progression and apoptosis resistance.\",\n      \"evidence\": \"Overexpression and shRNA knockdown in HEK293 cells with cell cycle analysis, spindle poison treatment, and IAP expression analysis\",\n      \"pmids\": [\"16762321\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which TPP2 promotes mitotic exit is unknown\",\n        \"Relevance of IAP upregulation to TPP2 catalytic activity not tested\",\n        \"Single cell line studied\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Genetic knockout in mice showed TPP2 predominantly destroys rather than generates MHC class I epitopes, reversing earlier models that emphasized a generative role and clarifying TPP2's net contribution to antigen processing.\",\n      \"evidence\": \"TPP2 knockout mouse with surface MHC I quantification, cytosolic peptide degradation assays, and dendritic cell cross-presentation assays\",\n      \"pmids\": [\"18056356\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Epitope-specific effects not fully catalogued\",\n        \"Whether TPP2 contributes to generation of specific epitopes in some contexts remains unresolved\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"TPP2 deficiency was shown to trigger cell type–specific apoptosis and senescence programs linked to p53 and NF-κB dysregulation, establishing TPP2 as a pro-survival factor beyond its peptide-trimming role.\",\n      \"evidence\": \"TPP2 knockout mouse with flow cytometry, apoptosis/senescence assays, and p53/NF-κB expression analysis\",\n      \"pmids\": [\"18362329\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Direct substrate(s) whose accumulation triggers p53 upregulation not identified\",\n        \"Whether the viability defect is catalytic-activity-dependent was not dissected\"\n      ]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Identification of MYBBP1A and CDK2 as physical interactors of TPP2—with the MYBBP1A interaction being activity-dependent—provided the first molecular links connecting TPP2's enzymatic function to tumor suppression and cell cycle regulation pathways.\",\n      \"evidence\": \"Co-immunoprecipitation and in situ proximity ligation assay in HEK293 cells with butabindide inhibitor\",\n      \"pmids\": [\"25303791\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Functional consequences of MYBBP1A and CDK2 interactions on cell cycle not established\",\n        \"Whether MYBBP1A is a substrate or regulatory partner is unknown\",\n        \"Single lab without reciprocal genetic validation\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Detection of physical complexes between TPP2, p53, and SIRT7 in both cytoplasm and nucleus suggested a direct mechanism by which TPP2 could regulate p53 stability or activity.\",\n      \"evidence\": \"Co-immunoprecipitation from HeLa lysates and mouse liver fractions, PLA in HEK293 cells\",\n      \"pmids\": [\"26169984\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No functional follow-up demonstrating that the interaction modulates p53 activity or stability\",\n        \"Single lab without reciprocal IP or genetic perturbation\",\n        \"Stoichiometry and directness of the ternary complex unclear\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"In situ cryo-ET visualization of TPP2 oligomeric states (36-mers and 32-mers) and their spatial proximity to 26S proteasomes in intact neurons provided the first native structural evidence for a postproteasomal processing relay.\",\n      \"evidence\": \"Cryo-electron tomography with Volta phase plate and template matching in rat hippocampal neurons\",\n      \"pmids\": [\"28396430\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether spatial proximity reflects direct physical contact or functional coupling is unresolved\",\n        \"Regulation of interconversion between 36-mer and 32-mer states unknown\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"A homozygous TPP2 missense mutation (p.Cys28Gly) confirmed as loss-of-function in patient cells established TPP2 deficiency as a cause of sterile brain inflammation, linking the enzyme to neuroinflammatory disease in humans.\",\n      \"evidence\": \"Next-generation sequencing with enzymatic activity assay and protein expression studies in patient blood cells\",\n      \"pmids\": [\"30533531\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which TPP2 loss triggers neuroinflammation not determined\",\n        \"Single family—genetic confirmation in additional kindreds needed\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrating that TPP2 redistributes from diffuse cytoplasmic localization to a perinuclear aggresomal mantle upon proteasome inhibition revealed a dynamic spatial relationship between TPP2 and the proteasome under proteotoxic stress.\",\n      \"evidence\": \"Confocal microscopy with fluorescent proteasome inhibitor and co-immunostaining in C26 murine colon adenocarcinoma cells\",\n      \"pmids\": [\"30226264\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether aggresomal recruitment is functionally protective or a consequence of substrate accumulation is unknown\",\n        \"Signals mediating TPP2 relocalization not identified\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The direct substrates whose accumulation upon TPP2 loss triggers p53 upregulation, apoptosis, senescence, and neuroinflammation remain unidentified, and the catalytic versus non-catalytic contributions of TPP2 to its pro-survival and cell cycle functions have not been dissected.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No substrate identification linking TPP2 loss to p53/NF-κB dysregulation\",\n        \"Catalytic versus scaffolding functions not separated genetically\",\n        \"Structural basis for oligomeric state regulation and its functional consequences unknown\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 3, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 6, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 3]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"MYBBP1A\",\n      \"CDK2\",\n      \"TP53\",\n      \"SIRT7\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}