{"gene":"GPAA1","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2001,"finding":"GAA1/GPAA1 is a core subunit of the GPI transamidase complex; the complex additionally contains GPI8, PIG-S, and PIG-T. PIG-T maintains the complex by stabilizing the expression of GAA1 and GPI8, and loss of PIG-S or PIG-T abolishes formation of the carbonyl intermediate with substrate proteins during GPI anchor transfer.","method":"Gene disruption by homologous recombination in mouse F9 cells, co-immunoprecipitation, carbonyl-intermediate formation assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP plus functional knockout with defined biochemical phenotype (carbonyl intermediate), replicated across labs","pmids":["11483512"],"is_preprint":false},{"year":2002,"finding":"GAA1/GPAA1 is an ER-localized polytopic membrane glycoprotein with a cytoplasmically oriented N terminus and a lumenally oriented C terminus; it sediments at ~17 S in detergent extracts. The large lumenal domain between the first and second transmembrane segments mediates interaction with other GPI transamidase subunits. C-terminal transmembrane segments are dispensable for subunit interaction but are required for a functional GPI transamidase complex. The cytoplasmic N terminus is not required for complex formation but may act as a membrane-sorting determinant.","method":"Epitope-tagged Gaa1 mutant analysis, membrane topology assay, subcellular fractionation, co-immunoprecipitation, sedimentation/density gradient, complementation in Gaa1-deficient cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — multiple orthogonal methods (topology, fractionation, co-IP, functional rescue), single lab","pmids":["12052837"],"is_preprint":false},{"year":2003,"finding":"A conserved proline residue within the C-terminal transmembrane span of Gaa1/GPAA1 is required for GPI recognition by the GPI transamidase complex. GPIT complexes containing C-terminally truncated Gaa1 retain all subunits and can interact with a proprotein substrate but cannot co-immunoprecipitate GPI; mutation of the conserved proline alone abrogates GPI co-immunoprecipitation.","method":"Site-directed mutagenesis, co-immunoprecipitation with GPI and proprotein substrates","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — active-site mutagenesis plus co-IP with substrate, single lab but multiple constructs and controls","pmids":["14660601"],"is_preprint":false},{"year":2005,"finding":"GAA1/GPAA1 lacks dominant ER-sorting determinants and is passively retained in the ER by a signalless mechanism; removal of a triple arginine cluster near the N terminus does not affect ER localization. Fusion proteins bearing different Gaa1 domains can exit the ER, confirming the passive retention model.","method":"Subcellular localization by fluorescence microscopy/fractionation, deletion and fusion protein analysis, N-glycosylation mapping","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with multiple deletion constructs, single lab","pmids":["15713669"],"is_preprint":false},{"year":2014,"finding":"The ~300-amino-acid lumenal domain of GAA1/GPAA1 is predicted and computationally validated to be an M28 family metallo-peptide-synthetase with an α/β hydrolase fold; it coordinates a single metal ion (most likely zinc) via three conserved polar residues and is proposed to catalyze peptide bond formation between the substrate protein's omega-site carbonyl and the phosphoethanolamine moiety of the GPI anchor.","method":"Bioinformatic sequence analysis, structural homology modeling, evolutionary conservation analysis","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational prediction without in vitro biochemical or mutagenesis validation","pmids":["24743167"],"is_preprint":false},{"year":2017,"finding":"The soluble lumenal domains of Gpi8 and Gaa1 (yeast orthologs) directly interact to form an α2β2 heterotetramer in vitro, without requirement for other subunits, establishing a core assembly unit of the GPI transamidase.","method":"Recombinant protein expression, GST pulldown, native gel electrophoresis, size-exclusion chromatography","journal":"Archives of biochemistry and biophysics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro reconstitution with multiple orthogonal biochemical methods (pulldown, native PAGE, SEC), single lab","pmids":["28893510"],"is_preprint":false},{"year":2020,"finding":"Structural modeling of the lumenal domain of human GPAA1 identifies two large flap loops surrounding the active site that undergo anti-correlated breathing-like dynamics; canonical zinc-binding sites 2 and 3 are the strongest binders for a single Zn ion, and substrate binding enhances interaction of site 5 with Zn1, consistent with a single zinc ion metallopeptidase mechanism.","method":"Comparative molecular dynamics simulation, homology modeling, phylogenetic analysis","journal":"Biology direct","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational modeling and MD simulation only, no experimental biochemical validation","pmids":["32993792"],"is_preprint":false},{"year":1998,"finding":"Overexpression of antisense hGAA1 in human K562 cells significantly reduces production of a GPI-anchored reporter protein on the cell surface, establishing that hGAA1/GPAA1 is required for GPI anchor attachment in human cells.","method":"Antisense overexpression, flow cytometry/cell surface reporter assay","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — loss-of-function with defined molecular phenotype (reduced GPI-anchored protein), single method, single lab","pmids":["9468317"],"is_preprint":false},{"year":2000,"finding":"3T3 cell lines expressing antisense mGPAA1 fail to express GPI-anchored proteins on the cell surface membrane, confirming an essential role of GPAA1 in GPI anchor attachment in murine cells.","method":"Antisense expression, cell surface protein assay","journal":"American journal of physiology. Cell physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — functional loss-of-function with defined molecular phenotype, single method, single lab","pmids":["10898732"],"is_preprint":false},{"year":2017,"finding":"Bi-allelic loss-of-function mutations in GPAA1 (frameshift, splicing, and missense) in humans cause reduced cell-surface abundance of multiple GPI-anchored proteins (FLAER, CD16, CD59, CD73, CD109) in patient leukocytes and fibroblasts; lentiviral transduction with wild-type GPAA1 partially rescues this GPI-anchor deficiency.","method":"Whole-exome sequencing, flow cytometry of patient cells, lentiviral rescue experiment","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — patient genetic data combined with functional flow-cytometry assay and lentiviral rescue, multiple families and orthogonal methods","pmids":["29100095"],"is_preprint":false},{"year":2019,"finding":"GPAA1 upregulation enhances GPI-anchored protein levels on the cell surface and intensifies lipid raft formation, which promotes EGFR–ERBB2 dimerization and downstream pro-proliferative signalling in gastric cancer cells.","method":"Co-immunoprecipitation, in situ proximity ligation assay, stable GPAA1 deletion/overexpression with proliferation and metastasis assays in vitro and in vivo","journal":"Journal of experimental & clinical cancer research : CR","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP and PLA for EGFR-ERBB2 interaction, supported by in vitro and in vivo functional assays, single lab","pmids":["31118109"],"is_preprint":false},{"year":2020,"finding":"A missense variant (c.968A>G) in GPAA1 causes scarce expression of GPAA1 protein in vascular endothelium and shifts its localization from the ER membrane to the cytoplasm and nucleus; wild-type GPAA1 expression in endothelial cells inhibits proliferation and migration, whereas the variant causes overgrowth and overmigration.","method":"Whole-exome sequencing, immunofluorescence localization, cell proliferation/migration assays with WT vs. variant GPAA1, gpaa1-deficient zebrafish model","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization experiment tied to functional consequence, plus zebrafish genetic model, single lab","pmids":["32533362"],"is_preprint":false},{"year":2024,"finding":"GPAA1 catalyzes GPI anchor attachment to CD24; genetic ablation of GPAA1 abolishes CD24 cell surface expression, enhances macrophage-mediated phagocytosis, and inhibits ovarian tumor growth in mice. The aminopeptidase inhibitor bestatin binds to GPAA1 and blocks GPI attachment, reducing CD24 surface expression.","method":"Genome-wide CRISPR knockout screen, genetic ablation (KO), phagocytosis assay, in vivo tumor model, drug-binding assay with bestatin","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — CRISPR KO with defined molecular phenotype (CD24 surface loss), in vivo validation, drug-binding mechanistic confirmation, multiple orthogonal methods","pmids":["38573857"],"is_preprint":false},{"year":2025,"finding":"The E3 ubiquitin ligase RCBTB2 directly interacts with GPAA1 and promotes its ubiquitin-mediated proteasomal degradation (protein downregulation without mRNA change); GPAA1 knockdown suppresses malignant behaviors of prostate cancer cells and reduces expression of aggrephagy-related factor p62.","method":"Co-immunoprecipitation, immunofluorescence co-localization, multi-omics analysis, RCBTB2 overexpression cell line, GPAA1 knockdown functional assays","journal":"American journal of cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP confirming direct interaction, protein-without-mRNA-change evidence for proteasomal degradation, functional rescue; single lab","pmids":["41244118"],"is_preprint":false}],"current_model":"GPAA1 (GAA1/hGAA1) is an ER-resident polytopic membrane glycoprotein and the M28-type metallo-peptide-synthetase subunit of the GPI transamidase complex; its large lumenal domain mediates assembly with GPI8/PIGK, PIGS, PIGT, and PIGU, while a conserved proline in its C-terminal transmembrane span is required for GPI lipid substrate recognition, enabling the transamidation reaction that cleaves the C-terminal signal peptide of precursor proteins and covalently attaches a preformed GPI anchor, a process regulated post-translationally by RCBTB2-mediated ubiquitin-proteasomal degradation of GPAA1."},"narrative":{"mechanistic_narrative":"GPAA1 (GAA1) is a core subunit of the endoplasmic reticulum GPI transamidase complex, the multiprotein machinery that cleaves the C-terminal signal peptide of precursor proteins and covalently attaches a preformed GPI anchor, and it is essential for cell-surface display of GPI-anchored proteins in human, mouse, and zebrafish cells [PMID:11483512, PMID:9468317, PMID:10898732, PMID:29100095]. It is a polytopic ER membrane glycoprotein with a cytoplasmic N terminus and a lumenal C terminus; its large lumenal domain between the first and second transmembrane segments mediates assembly with the other transamidase subunits, while the C-terminal transmembrane segments are dispensable for subunit interaction but required for catalytic function [PMID:12052837]. A conserved proline within the C-terminal transmembrane span is specifically required for recognition of the GPI lipid substrate: GPAA1 mutants lacking this residue retain all complex subunits and still bind proprotein substrate yet fail to co-immunoprecipitate GPI [PMID:14660601]. Bi-allelic loss-of-function mutations in GPAA1 cause a human inherited GPI-anchor deficiency disorder, with reduced surface abundance of multiple GPI-anchored proteins in patient cells that is partially rescued by wild-type GPAA1 [PMID:29100095]. Through its control of GPI-anchored substrates such as CD24, GPAA1 modulates cell-surface signaling and immune evasion, and its abundance is regulated post-translationally by RCBTB2-mediated ubiquitin-proteasomal degradation [PMID:38573857, PMID:41244118].","teleology":[{"year":1998,"claim":"Established that human GPAA1 is functionally required for GPI anchor attachment, moving it from a candidate to a necessary factor in the pathway.","evidence":"Antisense overexpression of hGAA1 in K562 cells with cell-surface GPI-anchored reporter readout","pmids":["9468317"],"confidence":"Medium","gaps":["Single loss-of-function method","No biochemical mechanism or complex membership defined"]},{"year":2000,"claim":"Confirmed the requirement for GPAA1 in GPI anchoring across species, generalizing the human finding to murine cells.","evidence":"Antisense mGPAA1 expression in 3T3 cells with cell-surface GPI-anchored protein assay","pmids":["10898732"],"confidence":"Medium","gaps":["Single method","Does not define molecular role within the complex"]},{"year":2001,"claim":"Defined GPAA1 as a core subunit of a multiprotein GPI transamidase complex and placed it among GPI8, PIG-S, and PIG-T, establishing the assembly that performs anchor transfer.","evidence":"Homologous-recombination knockouts in mouse F9 cells, reciprocal co-IP, and carbonyl-intermediate formation assay","pmids":["11483512"],"confidence":"High","gaps":["Stoichiometry and catalytic subunit identity not resolved","GPAA1's specific catalytic contribution unclear"]},{"year":2002,"claim":"Mapped GPAA1 membrane topology and domain architecture, showing the lumenal domain drives complex assembly while C-terminal transmembrane segments are required for catalysis but not assembly.","evidence":"Topology assays, subcellular fractionation, sedimentation, co-IP, and complementation in Gaa1-deficient cells with epitope-tagged mutants","pmids":["12052837"],"confidence":"High","gaps":["Function of the C-terminal segments not mechanistically explained","No atomic structure"]},{"year":2003,"claim":"Identified a conserved proline in the C-terminal transmembrane span as the determinant for GPI lipid substrate recognition, separating lipid binding from subunit assembly and proprotein binding.","evidence":"Site-directed mutagenesis with co-IP of GPI and proprotein substrates","pmids":["14660601"],"confidence":"High","gaps":["How the proline mediates GPI contact at structural level is unknown"]},{"year":2005,"claim":"Resolved how GPAA1 reaches the ER, showing passive signalless retention rather than an active sorting motif.","evidence":"Fluorescence localization, deletion/fusion constructs, and N-glycosylation mapping","pmids":["15713669"],"confidence":"Medium","gaps":["Retention mechanism remains indirect","Single lab"]},{"year":2017,"claim":"Provided in vitro evidence that the GPAA1 and GPI8 lumenal domains form a defined core heterotetramer, identifying a minimal assembly unit of the transamidase.","evidence":"Recombinant yeast ortholog lumenal domains analyzed by GST pulldown, native PAGE, and size-exclusion chromatography","pmids":["28893510"],"confidence":"Medium","gaps":["Yeast orthologs, not human proteins","Does not include other subunits or lipid substrate"]},{"year":2017,"claim":"Established GPAA1 as the cause of a human Mendelian GPI-anchor deficiency disorder via bi-allelic loss-of-function mutations.","evidence":"Whole-exome sequencing across families, flow cytometry of patient leukocytes/fibroblasts, and lentiviral wild-type rescue","pmids":["29100095"],"confidence":"High","gaps":["Genotype-phenotype correlation across mutation classes incomplete","Rescue only partial"]},{"year":2020,"claim":"Computational analyses proposed GPAA1 as a single-zinc M28 metallopeptidase whose lumenal active site catalyzes the transamidation peptide bond, offering a candidate catalytic mechanism.","evidence":"Homology modeling, molecular dynamics simulation, and phylogenetic analysis (also idx 4, 2014)","pmids":["32993792","24743167"],"confidence":"Low","gaps":["Computational only, no in vitro biochemical or mutagenesis validation","Metal coordination unproven experimentally"]},{"year":2019,"claim":"Linked GPAA1 abundance to oncogenic signaling, showing its upregulation enhances surface GPI-anchored proteins and lipid raft formation to promote EGFR-ERBB2 dimerization.","evidence":"Co-IP, in situ proximity ligation assay, and stable GPAA1 deletion/overexpression with in vitro and in vivo proliferation/metastasis assays in gastric cancer","pmids":["31118109"],"confidence":"Medium","gaps":["Causal chain from raft changes to EGFR dimerization indirect","Single lab"]},{"year":2024,"claim":"Identified CD24 as a specific GPAA1-dependent surface substrate with immune consequences and demonstrated a small-molecule (bestatin) that binds GPAA1 to block GPI attachment.","evidence":"Genome-wide CRISPR screen, genetic ablation, phagocytosis assay, in vivo ovarian tumor model, and bestatin drug-binding assay","pmids":["38573857"],"confidence":"High","gaps":["Bestatin binding site on GPAA1 not mapped","Substrate selectivity rules not defined"]},{"year":2025,"claim":"Revealed post-translational regulation of GPAA1 by the E3 ligase RCBTB2 through ubiquitin-proteasomal degradation, connecting GPAA1 turnover to cancer cell behavior.","evidence":"Co-IP, immunofluorescence co-localization, multi-omics, RCBTB2 overexpression, and GPAA1 knockdown functional assays in prostate cancer cells","pmids":["41244118"],"confidence":"Medium","gaps":["Ubiquitination sites on GPAA1 not identified","Single lab; reciprocal validation limited"]},{"year":null,"claim":"The catalytic mechanism of GPAA1 within the transamidase remains experimentally unproven, and a high-resolution structure of the human complex with bound GPI and proprotein substrate is lacking.","evidence":"No direct biochemical or structural validation of the proposed metallopeptidase activity in the corpus","pmids":[],"confidence":"Low","gaps":["No in vitro reconstitution of GPAA1 catalysis","No experimental zinc-coordination data","No atomic structure of the assembled human transamidase"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,2,12]}],"localization":[{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[1,3,11]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,9,12]}],"complexes":["GPI transamidase complex"],"partners":["PIGK","PIGS","PIGT","RCBTB2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O43292","full_name":"GPI-anchor transamidase component GPAA1","aliases":["GAA1 protein homolog","hGAA1","Glycosylphosphatidylinositol anchor attachment 1 protein","GPI anchor attachment protein 1"],"length_aa":621,"mass_kda":67.6,"function":"Component of the glycosylphosphatidylinositol-anchor (GPI-anchor) transamidase (GPI-T) complex that catalyzes the formation of the linkage between a proprotein and a GPI-anchor and participates in GPI anchored protein biosynthesis (PubMed:11483512, PubMed:29100095, PubMed:34576938, PubMed:35165458, PubMed:35551457, PubMed:37684232, PubMed:9468317). Binds GPI-anchor (PubMed:37684232)","subcellular_location":"Endoplasmic reticulum membrane","url":"https://www.uniprot.org/uniprotkb/O43292/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GPAA1","classification":"Not Classified","n_dependent_lines":23,"n_total_lines":1208,"dependency_fraction":0.01903973509933775},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CCDC47","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/GPAA1","total_profiled":1310},"omim":[{"mim_id":"617810","title":"GLYCOSYLPHOSPHATIDYLINOSITOL BIOSYNTHESIS DEFECT 15; GPIBD15","url":"https://www.omim.org/entry/617810"},{"mim_id":"610293","title":"GLYCOSYLPHOSPHATIDYLINOSITOL BIOSYNTHESIS DEFECT 1; GPIBD1","url":"https://www.omim.org/entry/610293"},{"mim_id":"610272","title":"PHOSPHATIDYLINOSITOL GLYCAN ANCHOR BIOSYNTHESIS CLASS T PROTEIN; PIGT","url":"https://www.omim.org/entry/610272"},{"mim_id":"610271","title":"PHOSPHATIDYLINOSITOL GLYCAN ANCHOR BIOSYNTHESIS CLASS S PROTEIN; PIGS","url":"https://www.omim.org/entry/610271"},{"mim_id":"603048","title":"GLYCOSYLPHOSPHATIDYLINOSITOL ANCHOR ATTACHMENT PROTEIN 1; GPAA1","url":"https://www.omim.org/entry/603048"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Endoplasmic reticulum","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Centrosome","reliability":"Additional"},{"location":"Mitochondria","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GPAA1"},"hgnc":{"alias_symbol":["GAA1","hGAA1"],"prev_symbol":[]},"alphafold":{"accession":"O43292","domains":[{"cath_id":"3.40.630.10","chopping":"62-366","consensus_level":"high","plddt":90.7295,"start":62,"end":366},{"cath_id":"-","chopping":"426-620","consensus_level":"high","plddt":88.5456,"start":426,"end":620}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O43292","model_url":"https://alphafold.ebi.ac.uk/files/AF-O43292-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O43292-F1-predicted_aligned_error_v6.png","plddt_mean":87.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GPAA1","jax_strain_url":"https://www.jax.org/strain/search?query=GPAA1"},"sequence":{"accession":"O43292","fasta_url":"https://rest.uniprot.org/uniprotkb/O43292.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O43292/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O43292"}},"corpus_meta":[{"pmid":"11483512","id":"PMC_11483512","title":"PIG-S and PIG-T, essential for GPI anchor attachment to proteins, form a complex with GAA1 and GPI8.","date":"2001","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/11483512","citation_count":143,"is_preprint":false},{"pmid":"29100095","id":"PMC_29100095","title":"Mutations in GPAA1, Encoding a GPI Transamidase Complex Protein, Cause Developmental Delay, Epilepsy, Cerebellar Atrophy, and Osteopenia.","date":"2017","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/29100095","citation_count":56,"is_preprint":false},{"pmid":"12052837","id":"PMC_12052837","title":"Structural requirements for the recruitment of Gaa1 into a functional glycosylphosphatidylinositol transamidase complex.","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12052837","citation_count":43,"is_preprint":false},{"pmid":"9468317","id":"PMC_9468317","title":"Molecular cloning of human homolog of yeast GAA1 which is required for attachment of glycosylphosphatidylinositols to proteins.","date":"1998","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/9468317","citation_count":42,"is_preprint":false},{"pmid":"24743167","id":"PMC_24743167","title":"Transamidase subunit GAA1/GPAA1 is a M28 family metallo-peptide-synthetase that catalyzes the peptide bond formation between the substrate protein's omega-site and the GPI lipid anchor's phosphoethanolamine.","date":"2014","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/24743167","citation_count":38,"is_preprint":false},{"pmid":"16642471","id":"PMC_16642471","title":"Increased expression of glycosyl-phosphatidylinositol anchor attachment protein 1 (GPAA1) is associated with gene amplification in hepatocellular carcinoma.","date":"2006","source":"International journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/16642471","citation_count":34,"is_preprint":false},{"pmid":"14660601","id":"PMC_14660601","title":"A conserved proline in the last transmembrane segment of Gaa1 is required for glycosylphosphatidylinositol (GPI) recognition by GPI transamidase.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/14660601","citation_count":31,"is_preprint":false},{"pmid":"27937175","id":"PMC_27937175","title":"The Glycosylphosphatidylinositol Anchor Biosynthesis Genes GPI12, GAA1, and GPI8 Are Essential for Cell-Wall Integrity and Pathogenicity of the Maize Anthracnose Fungus Colletotrichum graminicola.","date":"2016","source":"Molecular plant-microbe interactions : MPMI","url":"https://pubmed.ncbi.nlm.nih.gov/27937175","citation_count":25,"is_preprint":false},{"pmid":"31118109","id":"PMC_31118109","title":"GPAA1 promotes gastric cancer progression via upregulation of GPI-anchored protein and enhancement of ERBB signalling pathway.","date":"2019","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/31118109","citation_count":22,"is_preprint":false},{"pmid":"38573857","id":"PMC_38573857","title":"Targeting the GPI transamidase subunit GPAA1 abrogates the CD24 immune checkpoint in ovarian cancer.","date":"2024","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/38573857","citation_count":14,"is_preprint":false},{"pmid":"32533362","id":"PMC_32533362","title":"A novel variant in GPAA1, encoding a GPI transamidase complex protein, causes inherited vascular anomalies with various phenotypes.","date":"2020","source":"Human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32533362","citation_count":10,"is_preprint":false},{"pmid":"15713669","id":"PMC_15713669","title":"Endoplasmic reticulum localization of Gaa1 and PIG-T, subunits of the glycosylphosphatidylinositol transamidase complex.","date":"2005","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15713669","citation_count":9,"is_preprint":false},{"pmid":"28893510","id":"PMC_28893510","title":"The soluble domains of Gpi8 and Gaa1, two subunits of glycosylphosphatidylinositol transamidase (GPI-T), assemble into a complex.","date":"2017","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/28893510","citation_count":8,"is_preprint":false},{"pmid":"35399327","id":"PMC_35399327","title":"GPAA1 promotes the proliferation, invasion and migration of hepatocellular carcinoma cells by binding to RNA-binding protein SF3B4.","date":"2022","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/35399327","citation_count":6,"is_preprint":false},{"pmid":"32993792","id":"PMC_32993792","title":"Structural modelling of the lumenal domain of human GPAA1, the metallo-peptide synthetase subunit of the transamidase complex, reveals zinc-binding mode and two flaps surrounding the active site.","date":"2020","source":"Biology direct","url":"https://pubmed.ncbi.nlm.nih.gov/32993792","citation_count":6,"is_preprint":false},{"pmid":"10393431","id":"PMC_10393431","title":"Human and mouse GPAA1 (Glycosylphosphatidylinositol anchor attachment 1) genes: genomic structures, chromosome loci and the presence of a minor class intron.","date":"1999","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/10393431","citation_count":5,"is_preprint":false},{"pmid":"10898732","id":"PMC_10898732","title":"Cloning of murine glycosyl phosphatidylinositol anchor attachment protein, GPAA1.","date":"2000","source":"American journal of physiology. Cell physiology","url":"https://pubmed.ncbi.nlm.nih.gov/10898732","citation_count":5,"is_preprint":false},{"pmid":"32432756","id":"PMC_32432756","title":"GPAA1 promotes progression of childhood acute lymphoblastic leukemia through regulating c-myc.","date":"2020","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/32432756","citation_count":3,"is_preprint":false},{"pmid":"38112147","id":"PMC_38112147","title":"[Glycosylphosphatidylinositol biosynthesis deficiency 15 caused by GPAA1 gene mutation: a rare disease study].","date":"2023","source":"Zhongguo dang dai er ke za zhi = Chinese journal of contemporary pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/38112147","citation_count":1,"is_preprint":false},{"pmid":"41367867","id":"PMC_41367867","title":"Mechanistic insights into GPAA1-mediated cold tumor phenotype and immune evasion in colorectal cancer: integrative multi-omics analysis and experimental validation.","date":"2025","source":"Frontiers in oncology","url":"https://pubmed.ncbi.nlm.nih.gov/41367867","citation_count":0,"is_preprint":false},{"pmid":"41954755","id":"PMC_41954755","title":"Longitudinal analysis shows GAA1 length and baseline clinical status as robust predictors of progression in Friedreich ataxia.","date":"2026","source":"Journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/41954755","citation_count":0,"is_preprint":false},{"pmid":"41244118","id":"PMC_41244118","title":"The ubiquitin ligase RCBTB2 regulates aggrephagy and inhibits prostate cancer progression by targeting GPAA1 for degradation.","date":"2025","source":"American journal of cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/41244118","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":13205,"output_tokens":3377,"usd":0.045135,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11000,"output_tokens":3454,"usd":0.070675,"stage2_stop_reason":"end_turn"},"total_usd":0.11581,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"GAA1/GPAA1 is a core subunit of the GPI transamidase complex; the complex additionally contains GPI8, PIG-S, and PIG-T. PIG-T maintains the complex by stabilizing the expression of GAA1 and GPI8, and loss of PIG-S or PIG-T abolishes formation of the carbonyl intermediate with substrate proteins during GPI anchor transfer.\",\n      \"method\": \"Gene disruption by homologous recombination in mouse F9 cells, co-immunoprecipitation, carbonyl-intermediate formation assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP plus functional knockout with defined biochemical phenotype (carbonyl intermediate), replicated across labs\",\n      \"pmids\": [\"11483512\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"GAA1/GPAA1 is an ER-localized polytopic membrane glycoprotein with a cytoplasmically oriented N terminus and a lumenally oriented C terminus; it sediments at ~17 S in detergent extracts. The large lumenal domain between the first and second transmembrane segments mediates interaction with other GPI transamidase subunits. C-terminal transmembrane segments are dispensable for subunit interaction but are required for a functional GPI transamidase complex. The cytoplasmic N terminus is not required for complex formation but may act as a membrane-sorting determinant.\",\n      \"method\": \"Epitope-tagged Gaa1 mutant analysis, membrane topology assay, subcellular fractionation, co-immunoprecipitation, sedimentation/density gradient, complementation in Gaa1-deficient cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — multiple orthogonal methods (topology, fractionation, co-IP, functional rescue), single lab\",\n      \"pmids\": [\"12052837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"A conserved proline residue within the C-terminal transmembrane span of Gaa1/GPAA1 is required for GPI recognition by the GPI transamidase complex. GPIT complexes containing C-terminally truncated Gaa1 retain all subunits and can interact with a proprotein substrate but cannot co-immunoprecipitate GPI; mutation of the conserved proline alone abrogates GPI co-immunoprecipitation.\",\n      \"method\": \"Site-directed mutagenesis, co-immunoprecipitation with GPI and proprotein substrates\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — active-site mutagenesis plus co-IP with substrate, single lab but multiple constructs and controls\",\n      \"pmids\": [\"14660601\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"GAA1/GPAA1 lacks dominant ER-sorting determinants and is passively retained in the ER by a signalless mechanism; removal of a triple arginine cluster near the N terminus does not affect ER localization. Fusion proteins bearing different Gaa1 domains can exit the ER, confirming the passive retention model.\",\n      \"method\": \"Subcellular localization by fluorescence microscopy/fractionation, deletion and fusion protein analysis, N-glycosylation mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with multiple deletion constructs, single lab\",\n      \"pmids\": [\"15713669\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The ~300-amino-acid lumenal domain of GAA1/GPAA1 is predicted and computationally validated to be an M28 family metallo-peptide-synthetase with an α/β hydrolase fold; it coordinates a single metal ion (most likely zinc) via three conserved polar residues and is proposed to catalyze peptide bond formation between the substrate protein's omega-site carbonyl and the phosphoethanolamine moiety of the GPI anchor.\",\n      \"method\": \"Bioinformatic sequence analysis, structural homology modeling, evolutionary conservation analysis\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational prediction without in vitro biochemical or mutagenesis validation\",\n      \"pmids\": [\"24743167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The soluble lumenal domains of Gpi8 and Gaa1 (yeast orthologs) directly interact to form an α2β2 heterotetramer in vitro, without requirement for other subunits, establishing a core assembly unit of the GPI transamidase.\",\n      \"method\": \"Recombinant protein expression, GST pulldown, native gel electrophoresis, size-exclusion chromatography\",\n      \"journal\": \"Archives of biochemistry and biophysics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro reconstitution with multiple orthogonal biochemical methods (pulldown, native PAGE, SEC), single lab\",\n      \"pmids\": [\"28893510\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Structural modeling of the lumenal domain of human GPAA1 identifies two large flap loops surrounding the active site that undergo anti-correlated breathing-like dynamics; canonical zinc-binding sites 2 and 3 are the strongest binders for a single Zn ion, and substrate binding enhances interaction of site 5 with Zn1, consistent with a single zinc ion metallopeptidase mechanism.\",\n      \"method\": \"Comparative molecular dynamics simulation, homology modeling, phylogenetic analysis\",\n      \"journal\": \"Biology direct\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational modeling and MD simulation only, no experimental biochemical validation\",\n      \"pmids\": [\"32993792\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Overexpression of antisense hGAA1 in human K562 cells significantly reduces production of a GPI-anchored reporter protein on the cell surface, establishing that hGAA1/GPAA1 is required for GPI anchor attachment in human cells.\",\n      \"method\": \"Antisense overexpression, flow cytometry/cell surface reporter assay\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — loss-of-function with defined molecular phenotype (reduced GPI-anchored protein), single method, single lab\",\n      \"pmids\": [\"9468317\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"3T3 cell lines expressing antisense mGPAA1 fail to express GPI-anchored proteins on the cell surface membrane, confirming an essential role of GPAA1 in GPI anchor attachment in murine cells.\",\n      \"method\": \"Antisense expression, cell surface protein assay\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — functional loss-of-function with defined molecular phenotype, single method, single lab\",\n      \"pmids\": [\"10898732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Bi-allelic loss-of-function mutations in GPAA1 (frameshift, splicing, and missense) in humans cause reduced cell-surface abundance of multiple GPI-anchored proteins (FLAER, CD16, CD59, CD73, CD109) in patient leukocytes and fibroblasts; lentiviral transduction with wild-type GPAA1 partially rescues this GPI-anchor deficiency.\",\n      \"method\": \"Whole-exome sequencing, flow cytometry of patient cells, lentiviral rescue experiment\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — patient genetic data combined with functional flow-cytometry assay and lentiviral rescue, multiple families and orthogonal methods\",\n      \"pmids\": [\"29100095\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GPAA1 upregulation enhances GPI-anchored protein levels on the cell surface and intensifies lipid raft formation, which promotes EGFR–ERBB2 dimerization and downstream pro-proliferative signalling in gastric cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, in situ proximity ligation assay, stable GPAA1 deletion/overexpression with proliferation and metastasis assays in vitro and in vivo\",\n      \"journal\": \"Journal of experimental & clinical cancer research : CR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP and PLA for EGFR-ERBB2 interaction, supported by in vitro and in vivo functional assays, single lab\",\n      \"pmids\": [\"31118109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"A missense variant (c.968A>G) in GPAA1 causes scarce expression of GPAA1 protein in vascular endothelium and shifts its localization from the ER membrane to the cytoplasm and nucleus; wild-type GPAA1 expression in endothelial cells inhibits proliferation and migration, whereas the variant causes overgrowth and overmigration.\",\n      \"method\": \"Whole-exome sequencing, immunofluorescence localization, cell proliferation/migration assays with WT vs. variant GPAA1, gpaa1-deficient zebrafish model\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiment tied to functional consequence, plus zebrafish genetic model, single lab\",\n      \"pmids\": [\"32533362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GPAA1 catalyzes GPI anchor attachment to CD24; genetic ablation of GPAA1 abolishes CD24 cell surface expression, enhances macrophage-mediated phagocytosis, and inhibits ovarian tumor growth in mice. The aminopeptidase inhibitor bestatin binds to GPAA1 and blocks GPI attachment, reducing CD24 surface expression.\",\n      \"method\": \"Genome-wide CRISPR knockout screen, genetic ablation (KO), phagocytosis assay, in vivo tumor model, drug-binding assay with bestatin\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — CRISPR KO with defined molecular phenotype (CD24 surface loss), in vivo validation, drug-binding mechanistic confirmation, multiple orthogonal methods\",\n      \"pmids\": [\"38573857\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The E3 ubiquitin ligase RCBTB2 directly interacts with GPAA1 and promotes its ubiquitin-mediated proteasomal degradation (protein downregulation without mRNA change); GPAA1 knockdown suppresses malignant behaviors of prostate cancer cells and reduces expression of aggrephagy-related factor p62.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence co-localization, multi-omics analysis, RCBTB2 overexpression cell line, GPAA1 knockdown functional assays\",\n      \"journal\": \"American journal of cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP confirming direct interaction, protein-without-mRNA-change evidence for proteasomal degradation, functional rescue; single lab\",\n      \"pmids\": [\"41244118\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GPAA1 (GAA1/hGAA1) is an ER-resident polytopic membrane glycoprotein and the M28-type metallo-peptide-synthetase subunit of the GPI transamidase complex; its large lumenal domain mediates assembly with GPI8/PIGK, PIGS, PIGT, and PIGU, while a conserved proline in its C-terminal transmembrane span is required for GPI lipid substrate recognition, enabling the transamidation reaction that cleaves the C-terminal signal peptide of precursor proteins and covalently attaches a preformed GPI anchor, a process regulated post-translationally by RCBTB2-mediated ubiquitin-proteasomal degradation of GPAA1.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GPAA1 (GAA1) is a core subunit of the endoplasmic reticulum GPI transamidase complex, the multiprotein machinery that cleaves the C-terminal signal peptide of precursor proteins and covalently attaches a preformed GPI anchor, and it is essential for cell-surface display of GPI-anchored proteins in human, mouse, and zebrafish cells [#0, #7, #8, #9]. It is a polytopic ER membrane glycoprotein with a cytoplasmic N terminus and a lumenal C terminus; its large lumenal domain between the first and second transmembrane segments mediates assembly with the other transamidase subunits, while the C-terminal transmembrane segments are dispensable for subunit interaction but required for catalytic function [#1]. A conserved proline within the C-terminal transmembrane span is specifically required for recognition of the GPI lipid substrate: GPAA1 mutants lacking this residue retain all complex subunits and still bind proprotein substrate yet fail to co-immunoprecipitate GPI [#2]. Bi-allelic loss-of-function mutations in GPAA1 cause a human inherited GPI-anchor deficiency disorder, with reduced surface abundance of multiple GPI-anchored proteins in patient cells that is partially rescued by wild-type GPAA1 [#9]. Through its control of GPI-anchored substrates such as CD24, GPAA1 modulates cell-surface signaling and immune evasion, and its abundance is regulated post-translationally by RCBTB2-mediated ubiquitin-proteasomal degradation [#12, #13].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Established that human GPAA1 is functionally required for GPI anchor attachment, moving it from a candidate to a necessary factor in the pathway.\",\n      \"evidence\": \"Antisense overexpression of hGAA1 in K562 cells with cell-surface GPI-anchored reporter readout\",\n      \"pmids\": [\"9468317\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single loss-of-function method\", \"No biochemical mechanism or complex membership defined\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Confirmed the requirement for GPAA1 in GPI anchoring across species, generalizing the human finding to murine cells.\",\n      \"evidence\": \"Antisense mGPAA1 expression in 3T3 cells with cell-surface GPI-anchored protein assay\",\n      \"pmids\": [\"10898732\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single method\", \"Does not define molecular role within the complex\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Defined GPAA1 as a core subunit of a multiprotein GPI transamidase complex and placed it among GPI8, PIG-S, and PIG-T, establishing the assembly that performs anchor transfer.\",\n      \"evidence\": \"Homologous-recombination knockouts in mouse F9 cells, reciprocal co-IP, and carbonyl-intermediate formation assay\",\n      \"pmids\": [\"11483512\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and catalytic subunit identity not resolved\", \"GPAA1's specific catalytic contribution unclear\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Mapped GPAA1 membrane topology and domain architecture, showing the lumenal domain drives complex assembly while C-terminal transmembrane segments are required for catalysis but not assembly.\",\n      \"evidence\": \"Topology assays, subcellular fractionation, sedimentation, co-IP, and complementation in Gaa1-deficient cells with epitope-tagged mutants\",\n      \"pmids\": [\"12052837\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Function of the C-terminal segments not mechanistically explained\", \"No atomic structure\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Identified a conserved proline in the C-terminal transmembrane span as the determinant for GPI lipid substrate recognition, separating lipid binding from subunit assembly and proprotein binding.\",\n      \"evidence\": \"Site-directed mutagenesis with co-IP of GPI and proprotein substrates\",\n      \"pmids\": [\"14660601\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the proline mediates GPI contact at structural level is unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Resolved how GPAA1 reaches the ER, showing passive signalless retention rather than an active sorting motif.\",\n      \"evidence\": \"Fluorescence localization, deletion/fusion constructs, and N-glycosylation mapping\",\n      \"pmids\": [\"15713669\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Retention mechanism remains indirect\", \"Single lab\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Provided in vitro evidence that the GPAA1 and GPI8 lumenal domains form a defined core heterotetramer, identifying a minimal assembly unit of the transamidase.\",\n      \"evidence\": \"Recombinant yeast ortholog lumenal domains analyzed by GST pulldown, native PAGE, and size-exclusion chromatography\",\n      \"pmids\": [\"28893510\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Yeast orthologs, not human proteins\", \"Does not include other subunits or lipid substrate\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Established GPAA1 as the cause of a human Mendelian GPI-anchor deficiency disorder via bi-allelic loss-of-function mutations.\",\n      \"evidence\": \"Whole-exome sequencing across families, flow cytometry of patient leukocytes/fibroblasts, and lentiviral wild-type rescue\",\n      \"pmids\": [\"29100095\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genotype-phenotype correlation across mutation classes incomplete\", \"Rescue only partial\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Computational analyses proposed GPAA1 as a single-zinc M28 metallopeptidase whose lumenal active site catalyzes the transamidation peptide bond, offering a candidate catalytic mechanism.\",\n      \"evidence\": \"Homology modeling, molecular dynamics simulation, and phylogenetic analysis (also idx 4, 2014)\",\n      \"pmids\": [\"32993792\", \"24743167\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Computational only, no in vitro biochemical or mutagenesis validation\", \"Metal coordination unproven experimentally\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Linked GPAA1 abundance to oncogenic signaling, showing its upregulation enhances surface GPI-anchored proteins and lipid raft formation to promote EGFR-ERBB2 dimerization.\",\n      \"evidence\": \"Co-IP, in situ proximity ligation assay, and stable GPAA1 deletion/overexpression with in vitro and in vivo proliferation/metastasis assays in gastric cancer\",\n      \"pmids\": [\"31118109\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal chain from raft changes to EGFR dimerization indirect\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified CD24 as a specific GPAA1-dependent surface substrate with immune consequences and demonstrated a small-molecule (bestatin) that binds GPAA1 to block GPI attachment.\",\n      \"evidence\": \"Genome-wide CRISPR screen, genetic ablation, phagocytosis assay, in vivo ovarian tumor model, and bestatin drug-binding assay\",\n      \"pmids\": [\"38573857\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Bestatin binding site on GPAA1 not mapped\", \"Substrate selectivity rules not defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed post-translational regulation of GPAA1 by the E3 ligase RCBTB2 through ubiquitin-proteasomal degradation, connecting GPAA1 turnover to cancer cell behavior.\",\n      \"evidence\": \"Co-IP, immunofluorescence co-localization, multi-omics, RCBTB2 overexpression, and GPAA1 knockdown functional assays in prostate cancer cells\",\n      \"pmids\": [\"41244118\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitination sites on GPAA1 not identified\", \"Single lab; reciprocal validation limited\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The catalytic mechanism of GPAA1 within the transamidase remains experimentally unproven, and a high-resolution structure of the human complex with bound GPI and proprotein substrate is lacking.\",\n      \"evidence\": \"No direct biochemical or structural validation of the proposed metallopeptidase activity in the corpus\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No in vitro reconstitution of GPAA1 catalysis\", \"No experimental zinc-coordination data\", \"No atomic structure of the assembled human transamidase\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 2, 12]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1, 3, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 9, 12]}\n    ],\n    \"complexes\": [\"GPI transamidase complex\"],\n    \"partners\": [\"PIGK\", \"PIGS\", \"PIGT\", \"RCBTB2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":5,"faith_pct":80.0}}