{"gene":"PYCR1","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2009,"finding":"PYCR1 protein localizes to mitochondria; loss-of-function mutations cause altered mitochondrial morphology, reduced membrane potential, and increased apoptosis under oxidative stress in patient fibroblasts; knockdown of orthologs in Xenopus and zebrafish causes epidermal hypoplasia with massive apoptosis.","method":"Subcellular fractionation/localization, patient fibroblast functional assays, morpholino knockdown in Xenopus and zebrafish","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (localization, membrane potential, apoptosis assays, two vertebrate knockdown models), replicated across multiple patient kindreds","pmids":["19648921"],"is_preprint":false},{"year":2013,"finding":"DJ-1 (PARK7 gene product) directly binds PYCR1 both in vivo and in vitro; DJ-1 enhances PYCR1 enzymatic activity in vitro; both proteins co-localize in mitochondria; epistasis experiments (double knockdown showing no additivity) place them on the same anti-oxidative stress pathway.","method":"Co-immunoprecipitation, in vitro binding assay, in vitro enzymatic activity assay, fluorescence co-localization, genetic epistasis (double knockdown)","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — reciprocal in vivo/in vitro binding, enzymatic activity measurement, co-localization, and epistasis in single study with multiple orthogonal methods","pmids":["23743200"],"is_preprint":false},{"year":2016,"finding":"PYCR1 physically interacts with RRM2B (ribonucleotide reductase small subunit B) and PYCR2 as components of the same protein complex; dual silencing of PYCR1 and PYCR2 causes mitochondrial network fragmentation and hypersensitivity to oxidative stress, and abolishes the anti-oxidation activity of RRM2B overexpression.","method":"Large-scale Flag-RRM2B complex purification followed by mass spectrometry identification; shRNA silencing with oxidative stress phenotypic readout","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-identified complex plus functional rescue assay in single lab","pmids":["26733354"],"is_preprint":false},{"year":2018,"finding":"In IDH1-R132H mutant cells, enhanced PYCR1 activity oxidizes NADH to NAD+ during proline synthesis from glutamine, thereby partially uncoupling the electron transport chain from TCA cycle activity and maintaining a lower NADH/NAD+ ratio.","method":"Stable isotope tracing (glutamine-derived proline), NADH/NAD+ ratio measurement, oxygen consumption assays, PYCR1 activity assays in IDH1-mutant vs. wild-type cells","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — metabolic flux tracing with multiple metabolic readouts, mechanistic link to redox homeostasis established in single rigorous study","pmids":["29562167"],"is_preprint":false},{"year":2019,"finding":"SIRT3 deacetylates PYCR1 at lysine K228; CBP is the acetyltransferase that acetylates PYCR1 at K228; acetylation at K228 reduces PYCR1 enzymatic activity by impairing formation of the PYCR1 decamer; SIRT3-mediated deacetylation increases PYCR1 activity and promotes cell proliferation.","method":"Immunoprecipitation and mass spectrometry to identify SIRT3-PYCR1 interaction; in vitro binding; site-directed mutagenesis (K228); enzymatic activity assays; native PAGE to assess oligomeric state","journal":"Neoplasia","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro and in vivo binding, mutagenesis of acetylation site, enzymatic activity measurement, oligomer state analysis, all in one study","pmids":["31108370"],"is_preprint":false},{"year":2019,"finding":"PYCR1 directly interacts with STAT3 (demonstrated by co-immunoprecipitation); STAT3 overexpression partially reverses the effects of PYCR1 knockdown on proliferation, drug resistance, and EMT in colorectal cancer cells, placing PYCR1 upstream of STAT3-mediated p38 MAPK and NF-κB signaling.","method":"Co-immunoprecipitation (CoIP) assay; siRNA knockdown with STAT3 overexpression rescue; Western blot for pathway proteins","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — single CoIP plus rescue experiment, single lab","pmids":["31606203"],"is_preprint":false},{"year":2020,"finding":"Mitochondrial Lon chaperone protein binds PYCR1 as a client; Lon-dependent PYCR1 activity induces mitochondrial ROS production, which drives EMT via p38 and NF-κB signaling in cancer cells.","method":"Protein-protein interaction identification (Lon-PYCR1 client relationship), ROS measurement, EMT marker assays, signaling pathway Western blots","journal":"Cancer letters","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — client-chaperone interaction identified with functional downstream readouts, single lab","pmids":["31987921"],"is_preprint":false},{"year":2020,"finding":"In hypoxic conditions, mitochondrial PYCR1 activity is increased; PYCR1 oxidizes NADH coupled to proline synthesis, permitting continued TCA cycle activity; loss of PYCR1 leads to increased hypoxia in vivo and in 3D culture, resulting in widespread cell death.","method":"PYCR1 knockdown/knockout under hypoxic conditions; metabolic flux assays; 3D spheroid culture; in vivo tumor models with hypoxia imaging","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — loss-of-function with multiple orthogonal readouts (metabolic flux, 3D culture, in vivo), mechanistic link to TCA cycle redox balance established","pmids":["35108535"],"is_preprint":false},{"year":2020,"finding":"PYCR1 knockdown in lung adenocarcinoma (LUAD) significantly increases phosphorylation of JAK2 and STAT3 and elevates Bcl-2 and c-Myc expression, indicating that PYCR1 activity suppresses JAK/STAT signaling in LUAD cells.","method":"siRNA knockdown, Western blot for JAK2 and STAT3 phosphorylation, functional proliferation/migration assays","journal":"Molecular carcinogenesis","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, single method (Western blot for signaling), no direct mechanistic link established","pmids":["32133692"],"is_preprint":false},{"year":2021,"finding":"USP18 deubiquitinates FTO post-translationally, increasing FTO protein levels; elevated FTO then demethylates N6-methyladenosine (m6A) on PYCR1 mRNA, stabilizing the transcript and increasing PYCR1 protein in bladder cancer.","method":"Western blot for protein levels, m6A modification assays, mRNA stability assays, FTO enzymatic activity","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — post-translational regulation of upstream enzyme plus mRNA m6A modification of PYCR1 demonstrated with multiple assays, single lab","pmids":["33461172"],"is_preprint":false},{"year":2021,"finding":"Both PYCR1 and PYCR2 localize to mitochondria in fibroblasts; both can complement loss of yeast Pro3 (the yeast P5C-to-proline enzyme), confirming their enzymatic activity as P5C reductases; Pycr1 and Pycr2 double-mutant mice are sub-viable, indicating the genes are largely functionally redundant in proline biosynthesis.","method":"Fluorescence localization in fibroblasts; yeast complementation assay; mouse genetics (single and double null alleles)","journal":"Genetics","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — enzymatic complementation in yeast, mitochondrial localization confirmed, genetic redundancy established by double-mutant lethality","pmids":["33734376"],"is_preprint":false},{"year":2022,"finding":"PYCR1 is the key enzyme for de novo proline synthesis from glutamine in cancer-associated fibroblasts (CAFs); reducing PYCR1 levels in CAFs decreases tumor collagen production, tumor growth, and metastatic spread; proline synthesis in CAFs is epigenetically upregulated by increased pyruvate dehydrogenase-derived acetyl-CoA levels.","method":"Stable isotope tracing (glutamine-to-proline in CAFs), PYCR1 knockdown in CAFs, in vivo xenograft models, collagen quantification","journal":"Nature metabolism","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — metabolic flux tracing plus in vivo functional validation with multiple endpoints in single rigorous study","pmids":["35760868"],"is_preprint":false},{"year":2022,"finding":"PYCR1 overexpression inhibits lipid reactive oxygen species (ROS) production and promotes SLC25A10 expression in colorectal cancer cells; SLC25A10 overexpression reverses the anti-tumor effects of PYCR1 silencing, placing SLC25A10 downstream of PYCR1 in ferroptosis resistance.","method":"PYCR1 overexpression/silencing, lipid ROS measurement, ferroptosis inhibitor/inducer pharmacological experiments, SLC25A10 overexpression rescue","journal":"Human cell","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional epistasis by rescue experiment, multiple phenotypic readouts, single lab","pmids":["36104652"],"is_preprint":false},{"year":2022,"finding":"SENP3 promotes STAT3 deSUMOylation, increasing nuclear STAT3; nuclear STAT3 then directly binds the PYCR1 gene promoter to transcriptionally upregulate PYCR1 expression in bladder cancer.","method":"SENP3/STAT3 Western blot and nuclear fractionation; STAT3 promoter binding to PYCR1 (inferred from context of transcription factor function on PYCR1 promoter)","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional regulatory axis shown with multiple knockdown/overexpression experiments and rescue; direct promoter binding assay referenced but details limited in abstract","pmids":["36227136"],"is_preprint":false},{"year":2022,"finding":"CRIF1 promotes PYCR1 deacetylation and increased enzymatic activity via SIRT3; PYCR1 deacetylation reverses the anti-tumor effect of CRIF1 knockdown in NSCLC cells, placing CRIF1-SIRT3-PYCR1 in the same pathway.","method":"SIRT3-mediated deacetylation assay, PYCR1 enzymatic activity assays, CRIF1 knockdown with PYCR1 deacetylation rescue, flow cytometry for apoptosis","journal":"Journal of molecular histology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — enzymatic activity assay plus epistatic rescue experiment; replicates SIRT3-PYCR1 deacetylation axis from prior work","pmids":["35716330"],"is_preprint":false},{"year":2023,"finding":"Under hypoxia, nuclear IGF1R phosphorylates PYCR1 at Tyrosine 135; this phosphorylation promotes PYCR1 binding to ELK4 transcription factor and recruitment to ELK4-target gene promoters; PYCR1-catalyzed NAD+ production stimulates Sirt7 deacetylase activity on H3K18ac, mediating transcriptional repression and supporting tumor cell growth under hypoxia.","method":"Phosphorylation site identification (Y135), co-immunoprecipitation (PYCR1-ELK4), ChIP assay (PYCR1 at gene promoters), enzymatic NAD+ production assay, Sirt7 deacetylase activity assay, PYCR1 Y135 phosphomutant functional assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods: phosphosite identification, protein-protein interaction, ChIP, enzymatic activity, mutagenesis functional assays","pmids":["37777542"],"is_preprint":false},{"year":2023,"finding":"PYCR1 promotes NSCLC progression through JAK-STAT3 signaling, which is mediated via PRODH-dependent glutamine synthesis; PYCR1 activates STAT3 phosphorylation and promotes PD-L1 transcription by elevating STAT3 binding to the PD-L1 gene promoter.","method":"PYCR1 overexpression with siPRODH and STAT3 inhibitor (stattic) rescue; ChIP assay for STAT3 binding to PD-L1 promoter; luciferase assay for PD-L1 transcription","journal":"Translational oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and luciferase confirm transcriptional mechanism; rescue with inhibitors places pathway; single lab","pmids":["37018868"],"is_preprint":false},{"year":2024,"finding":"PYCR1 interacts with EGFR by co-immunoprecipitation; PYCR1 knockout inhibits proliferation, migration, and colony formation; in NSCLC, PYCR1 stabilizes EGFR by forming a complex with EGFR and USP11, enhancing EGFR deubiquitination and stability; PYCR1 also promotes TLR signaling by interacting with TRAF6, TAK1, ECSIT, and TAB2, facilitating their ubiquitination and NF-κB activation.","method":"CRISPR-Cas9 PYCR1-KO, co-immunoprecipitation, mass spectrometry, EGFR ubiquitination assay, NF-κB activation assay, pharmacological inhibition with PYCR1-IN-1","journal":"Experimental & molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR KO with multiple molecular interaction methods (CoIP, MS, ubiquitination assay), single lab","pmids":["41254241"],"is_preprint":false},{"year":2024,"finding":"PYCR1 interacts with EGFR (co-immunoprecipitation); aerobic glycolysis and the EGFR/PI3K/AKT pathway are required downstream of PYCR1 in bladder cancer; EGFR inhibitor CL-387785 inhibits the EGFR/PI3K/AKT pathway and attenuates effects of PYCR1 overexpression but has no effect on PYCR1 expression itself.","method":"Co-immunoprecipitation, PYCR1 knockdown/overexpression, EGFR inhibitor treatment, glycolysis assays","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — CoIP plus pharmacological rescue; replicated PYCR1-EGFR interaction across two papers","pmids":["37293856"],"is_preprint":false},{"year":2024,"finding":"BHLHE41 directly interacts with PYCR1 (co-immunoprecipitation); BHLHE41 decreases PYCR1 protein stability by promoting its ubiquitination and proteasomal degradation, thereby inactivating the PI3K/AKT signaling pathway in bladder cancer.","method":"Co-immunoprecipitation, ubiquitination assay, protein stability assays, rescue experiments with PYCR1 overexpression","journal":"European journal of medical research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — CoIP, ubiquitination, and rescue assays in single lab study","pmids":["38811952"],"is_preprint":false},{"year":2024,"finding":"ITPKA kinase interacts with PYCR1 and phosphorylates PYCR1 at serine 29; this phosphorylation inhibits E3 ligase Stub1-mediated ubiquitination of PYCR1, thereby stabilizing PYCR1 protein and contributing to glioma progression.","method":"Protein-protein interaction (co-immunoprecipitation), phosphorylation site identification (S29), ubiquitination assay, protein stability assay","journal":"Heliyon","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — phosphosite identified with ubiquitination and stability assays, single lab","pmids":["39170313"],"is_preprint":false},{"year":2024,"finding":"PYCR1 knockout in liver cancer cells inhibits glycolysis and reduces H3K18 lactylation of the IRS1 histone, thereby inhibiting IRS1 expression; this pathway links PYCR1 activity to metabolic gene regulation via histone lactylation.","method":"PYCR1 knockout, metabolomics, transcriptome sequencing, ChIP assay for H3K18 lactylation at IRS1 promoter","journal":"Clinical and translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP for histone modification plus metabolomics and transcriptomics; single lab with multiple orthogonal methods","pmids":["39422696"],"is_preprint":false},{"year":2024,"finding":"PYCR1 interacts with EGFR and promotes esophageal squamous cell carcinoma progression and metastasis by activating the PI3K/AKT/mTOR signaling pathway; EGFR overexpression reverses the inhibitory effects of PYCR1 knockdown.","method":"Co-immunoprecipitation, mass spectrometry, immunofluorescence, proteomic analysis, EGFR overexpression rescue, in vivo xenograft","journal":"The journal of gene medicine","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — CoIP/MS identification plus rescue experiment; independent replication of PYCR1-EGFR interaction across cancer types","pmids":["40102683"],"is_preprint":false},{"year":2024,"finding":"The micropeptide TREMP (encoded by lincR-PPP2R5C) localizes to mitochondria and interacts with PYCR1; this interaction enhances glycolysis and promotes Th2 cell differentiation; PYCR1 knockout mice show attenuated allergic airway inflammation similar to TREMP knockout mice.","method":"Co-immunoprecipitation (TREMP-PYCR1), CRISPR PYCR1-KO mice, glycolysis measurement, Th2 differentiation assays, in vivo HDM allergy model","journal":"Allergology international","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CoIP, KO mouse model, metabolic and immunological readouts in single study","pmids":["39025723"],"is_preprint":false},{"year":2024,"finding":"Homozygous missense mutation p.Ala187Thr in PYCR1 decreases enzymatic activity in vitro; 3D structural modeling shows the mutation alters hydrogen bonds causing protein misfolding.","method":"In vitro enzymatic activity assay of mutant vs. wild-type PYCR1, 3D structural modeling","journal":"Molecular genetics and genomics","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic assay is Tier 1 but single lab, single patient mutation study","pmids":["39172257"],"is_preprint":false},{"year":2014,"finding":"PYCR1 can reduce Δ1-piperideine-6-carboxylate (P6C) to L-pipecolic acid with a Km of similar magnitude to its Km for P5C-to-proline conversion; this was confirmed using urine from antiquitin-deficient patients accumulating P6C, demonstrating PYCR1 has an alternative substrate in lysine degradation.","method":"In vitro enzymatic assay with commercial PYCR1 and P6C substrate; LC-MS/MS quantification of substrate/product; confirmation with patient urine samples","journal":"Journal of inherited metabolic disease","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic reconstitution with kinetic parameters plus biological validation using patient material","pmids":["24431009"],"is_preprint":false},{"year":2020,"finding":"X-ray crystal structure of human PYCR1 complexed with N-formyl-L-proline (NFLP) reveals that inhibitor binding induces conformational changes in the active site including translation of an α-helix by 1 Å; NFLP competitively inhibits PYCR1 with respect to P5C substrate (Ki = 100 μM) and phenocopies PYCR1 knockdown in breast cancer cells by inhibiting de novo proline biosynthesis.","method":"X-ray crystallography (co-crystal structure), competitive inhibition kinetics, cell-based proline biosynthesis assay, spheroid growth assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus kinetic mechanism determination plus cell-based functional validation in single rigorous study","pmids":["33109600"],"is_preprint":false},{"year":2024,"finding":"Fragment-based crystallographic screening identified eight fragment hits binding to human PYCR1; novel fragments block both the P5C substrate pocket and the NAD(P)H binding site (dual-site binders); four hits show enzymatic inhibition, demonstrating the active site architecture accommodates dual-site inhibitors.","method":"X-ray crystallography fragment screening (22% hit rate), kinetic inhibition assays","journal":"Journal of chemical information and modeling","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structures plus kinetic assays defining active site and binding pockets in single rigorous study","pmids":["38411104"],"is_preprint":false},{"year":2025,"finding":"Crystallographic fragment screening against PYCR1 revealed ligands occupying P5C and NADH binding pockets including dual-site ligands; sulfonamide and sulfamate groups are isosteric replacements for the carboxylate in the active site; a cryptic subpocket near the nicotinamide-binding site was identified; ligand-induced conformational changes were confirmed by molecular dynamics to be intrinsically accessible.","method":"X-ray crystallography (12 co-crystal structures), molecular dynamics simulations","journal":"Bioorganic chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple crystal structures defining active site plasticity in single rigorous study","pmids":["41016381"],"is_preprint":false},{"year":2025,"finding":"SMYD2 methyltransferase upregulates PYCR1 expression through H3K4me3 histone modification at the PYCR1 locus; elevated PYCR1 subsequently activates the PINK1/Parkin mitophagy pathway, supporting bladder cancer stem cell stemness maintenance.","method":"H3K4me3 ChIP assay at PYCR1 promoter, siRNA knockdown of SMYD2/PYCR1, mitophagy markers (LC3B, PINK1, Parkin), cancer stem cell assays","journal":"International journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP confirms epigenetic regulation, functional pathway established by rescue, single lab","pmids":["40341538"],"is_preprint":false},{"year":2025,"finding":"FOXA1 transcription factor directly activates PYCR1 transcription (ChIP assay); elevated PYCR1 activates autophagy in LUAD cells, which suppresses CD8+ T cell-mediated anti-tumor killing; PYCR1 overexpression reverses the effect of FOXA1 knockdown.","method":"ChIP assay (FOXA1 binding to PYCR1 promoter), dual-luciferase assay, PYCR1 knockdown/overexpression, CD8+ T cell cytotoxicity assay, in vivo mouse experiments","journal":"Cancer immunology, immunotherapy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and luciferase confirm transcriptional regulation, rescue experiments establish pathway, single lab","pmids":["40848149"],"is_preprint":false},{"year":2022,"finding":"Hypomethylation at a CpG island in the PYCR1 promoter and p300-induced H3K27ac modification at the PYCR1 promoter both contribute to PYCR1 transcriptional upregulation in gastric cancer.","method":"DNA methylation analysis (bisulfite sequencing/bioinformatics), ChIP for H3K27ac, p300 acetyltransferase functional experiments","journal":"Biochimica et biophysica acta. Gene regulatory mechanisms","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP and methylation analysis with functional validation, single lab","pmids":["35654390"],"is_preprint":false},{"year":2019,"finding":"Pycr1 knockout zebrafish show markedly reduced proline and extracellular matrix contents, lowered energy, diminished superoxide dismutase and telomerase activity, increased apoptosis and senescence from embryo stage, and a progeria-like phenotype; adult pycr1 KO fish display reduced locomotion, aggression, social interaction, and dysregulated circadian rhythm.","method":"CRISPR/Cas9 pycr1 knockout zebrafish, biochemical assays (proline, ECM, ATP, SOD, telomerase), apoptosis/senescence staining, behavioral testing","journal":"Cells","confidence":"High","confidence_rationale":"Tier 2 / Strong — complete KO in vertebrate model with multiple biochemical and behavioral readouts establishing roles in proline synthesis, redox defense, and aging","pmids":["31091804"],"is_preprint":false},{"year":2024,"finding":"PYCR1 regulates TRAIL resistance in NSCLC by preventing redistribution of death receptors (DRs) to the plasma membrane; PYCR1 knockdown increases DR surface localization, activates Caspase-3/8, and sensitizes cells to TRAIL-induced apoptosis; PYCR1 overexpression reduces DR surface distribution and suppresses Caspase-3/8 activation.","method":"PYCR1 knockdown/overexpression, flow cytometry for surface DR localization, Caspase-3/8 activity assays, TRAIL sensitivity assays","journal":"Oncology letters","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — functional mechanism (DR redistribution) established with flow cytometry and caspase assays, single lab","pmids":["38549801"],"is_preprint":false}],"current_model":"PYCR1 is a mitochondrial enzyme that catalyzes the final NAD(P)H-dependent reduction of Δ1-pyrroline-5-carboxylate (P5C) to L-proline (and can also reduce Δ1-piperideine-6-carboxylate to L-pipecolic acid), thereby linking proline biosynthesis to cellular redox homeostasis by oxidizing NADH/NADPH; its enzymatic activity is regulated post-translationally by SIRT3-mediated deacetylation at K228 (which promotes active decamer formation), CBP-mediated acetylation (which inhibits it), ITPKA-mediated phosphorylation at S29 (which stabilizes it against ubiquitin-mediated degradation by Stub1), and IGF1R-mediated phosphorylation at Y135 (which drives nuclear localization and recruitment to ELK4 target gene promoters to regulate transcription via Sirt7-dependent H3K18ac deacetylation); in the mitochondria it physically interacts with DJ-1 (which enhances its activity), RRM2B, the Lon chaperone, and a TREMP micropeptide, collectively supporting oxidative stress resistance; its transcription is controlled by STAT3 (downstream of SENP3-deSUMOylation), FOXA1, SMYD2-mediated H3K4me3, and promoter hypomethylation; in cancer-associated fibroblasts PYCR1-driven proline synthesis fuels collagen production and tumor-promoting extracellular matrix remodeling, while in cancer cells it supports TCA cycle activity under hypoxia, inhibits ferroptosis via SLC25A10, regulates EGFR stability via a PYCR1-USP11 deubiquitination complex, and modulates TLR/NF-κB and PI3K/AKT/mTOR signaling."},"narrative":{"mechanistic_narrative":"PYCR1 is a mitochondrial enzyme that catalyzes the final NAD(P)H-dependent reduction of Δ1-pyrroline-5-carboxylate (P5C) to L-proline, coupling de novo proline biosynthesis to cellular redox balance and oxidative-stress resistance [PMID:33734376, PMID:33109600]. Crystallographic and kinetic work defines an active site with adjacent P5C-substrate and NAD(P)H-binding pockets that accommodate competitive and dual-site inhibitors and undergoes conformational change on ligand binding [PMID:33109600, PMID:38411104, PMID:41016381], and the enzyme also reduces Δ1-piperideine-6-carboxylate to L-pipecolic acid, giving it a role in lysine degradation [PMID:24431009]. Its catalytic output is redox-directed: by oxidizing NADH to NAD+ during proline synthesis, PYCR1 lowers the NADH/NAD+ ratio and sustains TCA-cycle flux under IDH1-mutant and hypoxic conditions, with loss of PYCR1 driving hypoxia and cell death in tumors [PMID:29562167, PMID:35108535]. Enzyme activity is tuned post-translationally through SIRT3-mediated deacetylation at K228, which favors active-decamer formation and opposes CBP acetylation [PMID:31108370, PMID:35716330], while protein stability is controlled by phosphorylation-coupled ubiquitination involving ITPKA/Stub1 [PMID:39170313] and BHLHE41 [PMID:38811952]. Beyond catalysis, hypoxic IGF1R-driven phosphorylation at Y135 recruits nuclear PYCR1 to ELK4 target promoters where its NAD+ production fuels Sirt7-dependent H3K18ac removal, linking the enzyme to transcriptional control [PMID:37777542]. PYCR1 supports oxidative-stress defense via direct interaction with DJ-1 (PARK7) and assembly with RRM2B/PYCR2 [PMID:23743200, PMID:26733354], and in cancer-associated fibroblasts its proline output drives collagen production and extracellular-matrix remodeling that promote tumor growth and metastasis [PMID:35760868]. Loss-of-function PYCR1 mutations cause a connective-tissue/progeroid phenotype with mitochondrial dysfunction, increased apoptosis under oxidative stress, and reduced enzymatic activity from misfolding-prone alleles [PMID:19648921, PMID:39172257].","teleology":[{"year":2009,"claim":"Established that PYCR1 is a mitochondrial protein whose loss compromises mitochondrial integrity and survival, framing it as a redox/stress-resistance factor rather than a purely metabolic enzyme.","evidence":"Subcellular fractionation, patient fibroblast membrane-potential and apoptosis assays, and morpholino knockdown in Xenopus and zebrafish","pmids":["19648921"],"confidence":"High","gaps":["Did not define the catalytic mechanism linking PYCR1 to membrane potential","Did not identify protein partners mediating stress resistance"]},{"year":2013,"claim":"Identified a direct partner (DJ-1/PARK7) that enhances PYCR1 activity, placing PYCR1 on a defined anti-oxidative-stress pathway.","evidence":"Reciprocal Co-IP, in vitro binding, in vitro activity assay, co-localization, and double-knockdown epistasis","pmids":["23743200"],"confidence":"High","gaps":["Structural basis of DJ-1 binding not resolved","Whether DJ-1 alters oligomeric state untested"]},{"year":2014,"claim":"Demonstrated PYCR1 has a second substrate, reducing P6C to pipecolic acid, extending its role to lysine degradation.","evidence":"In vitro kinetic assay with commercial PYCR1 plus LC-MS/MS, validated with antiquitin-deficient patient urine","pmids":["24431009"],"confidence":"High","gaps":["Physiological significance of pipecolic acid synthesis in vivo unquantified"]},{"year":2016,"claim":"Placed PYCR1 in a higher-order complex with RRM2B and PYCR2 required for RRM2B-mediated oxidative protection.","evidence":"Flag-RRM2B complex purification with MS plus shRNA silencing under oxidative stress","pmids":["26733354"],"confidence":"Medium","gaps":["Stoichiometry and direct vs. indirect contacts within the complex unknown","Single-lab finding without reciprocal pulldown"]},{"year":2018,"claim":"Connected PYCR1 catalysis to redox homeostasis by showing it oxidizes NADH to NAD+ to lower the NADH/NAD+ ratio in IDH1-mutant cells, partially uncoupling the ETC from the TCA cycle.","evidence":"Glutamine-to-proline isotope tracing, NADH/NAD+ measurement, oxygen consumption, and activity assays","pmids":["29562167"],"confidence":"High","gaps":["Generality beyond IDH1-mutant context not addressed here"]},{"year":2019,"claim":"Defined post-translational control of PYCR1 activity through SIRT3 deacetylation and CBP acetylation at K228 governing decamer assembly.","evidence":"IP-MS, in vitro binding, K228 mutagenesis, activity assays, and native PAGE oligomer analysis","pmids":["31108370"],"confidence":"High","gaps":["Stimuli that trigger SIRT3/CBP switching on PYCR1 not defined","Whether other lysines are modified untested"]},{"year":2019,"claim":"Linked PYCR1 to signaling control by showing it interacts with STAT3 and acts upstream of STAT3-mediated proliferation and EMT programs.","evidence":"Co-IP and siRNA knockdown with STAT3 overexpression rescue in colorectal cancer cells","pmids":["31606203"],"confidence":"Medium","gaps":["Direct vs. indirect PYCR1-STAT3 binding not resolved by reciprocal validation","Mechanism connecting enzyme activity to STAT3 unclear"]},{"year":2020,"claim":"Showed PYCR1 activity rises under hypoxia and sustains TCA-cycle flux, making it required for tumor cell survival in low-oxygen microenvironments.","evidence":"Loss-of-function with metabolic flux, 3D spheroid, and in vivo hypoxia imaging","pmids":["35108535"],"confidence":"High","gaps":["How hypoxia increases PYCR1 activity mechanistically not fully defined"]},{"year":2020,"claim":"Implicated a Lon chaperone-PYCR1 client relationship and downstream ROS/EMT signaling in cancer cells.","evidence":"Lon-PYCR1 interaction, ROS measurement, EMT markers, and signaling Western blots","pmids":["31987921"],"confidence":"Medium","gaps":["Whether Lon regulates PYCR1 folding or stability directly untested","Single-lab functional readouts"]},{"year":2021,"claim":"Confirmed PYCR1 and PYCR2 are functionally redundant P5C reductases by yeast complementation and double-mutant mouse lethality.","evidence":"Fibroblast localization, yeast Pro3 complementation, and single/double-null mouse genetics","pmids":["33734376"],"confidence":"High","gaps":["Tissue-specific division of labor between PYCR1 and PYCR2 not delineated"]},{"year":2021,"claim":"Identified m6A-dependent transcript regulation of PYCR1 via a USP18-FTO axis controlling its protein levels in bladder cancer.","evidence":"m6A modification, mRNA stability, FTO activity, and protein-level Western blots","pmids":["33461172"],"confidence":"Medium","gaps":["Direct FTO occupancy on PYCR1 mRNA sites not mapped","Single-lab finding"]},{"year":2022,"claim":"Established PYCR1 as the key proline-synthesizing enzyme in cancer-associated fibroblasts driving collagen and ECM-dependent tumor growth and metastasis.","evidence":"Glutamine-to-proline isotope tracing in CAFs, PYCR1 knockdown, xenografts, and collagen quantification","pmids":["35760868"],"confidence":"High","gaps":["Mechanism by which acetyl-CoA epigenetically upregulates proline synthesis not fully detailed"]},{"year":2022,"claim":"Consolidated transcriptional and epigenetic control of PYCR1 through STAT3/SENP3, promoter hypomethylation, and p300-H3K27ac, plus a SIRT3-dependent CRIF1 input on activity.","evidence":"Promoter binding/ChIP, methylation analysis, and SIRT3 deacetylation rescue across bladder, gastric, and NSCLC models","pmids":["36227136","35654390","35716330"],"confidence":"Medium","gaps":["Relative contribution of each regulatory layer in a given tissue unresolved","Mostly single-lab per-axis findings"]},{"year":2022,"claim":"Linked PYCR1 to ferroptosis resistance via SLC25A10, suppressing lipid ROS in colorectal cancer.","evidence":"Overexpression/silencing, lipid ROS measurement, ferroptosis pharmacology, and SLC25A10 rescue","pmids":["36104652"],"confidence":"Medium","gaps":["Direct mechanism connecting PYCR1 to SLC25A10 expression unknown","Single-lab epistasis"]},{"year":2023,"claim":"Revealed a moonlighting transcriptional role: hypoxic IGF1R phosphorylation at Y135 drives nuclear PYCR1 to ELK4 promoters where NAD+ production fuels Sirt7-dependent H3K18ac deacetylation.","evidence":"Phosphosite identification, Co-IP, ChIP, NAD+ and Sirt7 activity assays, and Y135 phosphomutant functional assays","pmids":["37777542"],"confidence":"High","gaps":["Breadth of ELK4 target genes regulated this way not mapped","Balance between nuclear and mitochondrial PYCR1 pools undefined"]},{"year":2024,"claim":"Defined protein-stability control of PYCR1 by opposing ubiquitin pathways: ITPKA-S29 phosphorylation blocks Stub1 ubiquitination while BHLHE41 promotes its degradation.","evidence":"Co-IP, phosphosite identification, ubiquitination and protein-stability assays in glioma and bladder cancer","pmids":["39170313","38811952"],"confidence":"Medium","gaps":["Whether these inputs converge on the same lysines unknown","Single-lab per-axis evidence"]},{"year":2024,"claim":"Positioned PYCR1 as a scaffold/regulator of EGFR stability and TLR/NF-κB signaling through a USP11-EGFR deubiquitination complex and interactions with TRAF6/TAK1/ECSIT/TAB2.","evidence":"CRISPR KO, Co-IP, MS, EGFR ubiquitination, and NF-κB activation assays; replicated EGFR interaction across cancers","pmids":["41254241","37293856","40102683"],"confidence":"Medium","gaps":["Whether EGFR/signaling roles depend on catalytic activity untested","Direct vs. complex-mediated contacts not all reciprocally validated"]},{"year":2024,"claim":"Showed PYCR1 supports immune and apoptotic phenotypes — promoting Th2 differentiation via a mitochondrial TREMP micropeptide and conferring TRAIL resistance by sequestering death receptors from the surface.","evidence":"Co-IP, PYCR1-KO mice with airway allergy model; flow cytometry of surface death receptors and caspase assays","pmids":["39025723","38549801"],"confidence":"Medium","gaps":["Molecular basis of death-receptor redistribution unknown","Whether TREMP alters PYCR1 catalysis untested"]},{"year":2024,"claim":"Provided structural and chemical-biology tools defining the PYCR1 active site, including a co-crystal with a competitive inhibitor and dual-site fragment binders.","evidence":"X-ray crystallography (inhibitor co-crystals and fragment screens), kinetic inhibition, MD simulations, and cell-based proline assays","pmids":["33109600","38411104","41016381"],"confidence":"High","gaps":["No structure of the active decamer with cofactor in catalytic cycle reported here","Cryptic subpocket druggability in cells unconfirmed"]},{"year":2024,"claim":"Tied PYCR1 disease alleles to enzymatic loss-of-function, showing a missense mutation reduces activity via misfolding.","evidence":"In vitro activity assay of mutant vs. wild-type plus 3D structural modeling","pmids":["39172257"],"confidence":"Medium","gaps":["Single mutation, single patient","Cellular consequences of misfolding not assessed"]},{"year":2025,"claim":"Connected PYCR1 to organelle-quality-control and metabolic-gene programs, activating PINK1/Parkin mitophagy for stemness and influencing H3K18-lactylation/autophagy-linked immune evasion.","evidence":"ChIP (H3K4me3, H3K18la), metabolomics/transcriptomics, mitophagy markers, CD8+ T-cell cytotoxicity, and in vivo models","pmids":["40341538","39422696","40848149"],"confidence":"Medium","gaps":["Causal chain from proline/NAD+ output to lactylation and mitophagy not fully resolved","Single-lab per-pathway findings"]},{"year":null,"claim":"How a single mitochondrial reductase is partitioned between its catalytic, redox-buffering, nuclear-transcriptional, and signaling-scaffold roles — and which roles depend on enzymatic activity versus protein scaffolding — remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model integrating mitochondrial, nuclear, and scaffold functions","Activity-dependence of EGFR/TLR/STAT3 roles untested","Structure of catalytically active decamer with bound cofactor not determined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[10,25,26,3]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[10,25]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,1,10,23]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[15]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[3,7,11,25]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[0,1,7]}],"complexes":["PYCR1-PYCR2-RRM2B complex","PYCR1-EGFR-USP11 deubiquitination complex"],"partners":["PARK7","RRM2B","PYCR2","EGFR","USP11","STAT3","ITPKA","BHLHE41"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P32322","full_name":"Pyrroline-5-carboxylate reductase 1, mitochondrial","aliases":[],"length_aa":319,"mass_kda":33.4,"function":"Oxidoreductase that catalyzes the last step in proline biosynthesis, which corresponds to the reduction of pyrroline-5-carboxylate to L-proline using NAD(P)H (PubMed:16730026, PubMed:19648921, PubMed:23024808, PubMed:28258219). At physiologic concentrations, has higher specific activity in the presence of NADH (PubMed:16730026, PubMed:23024808). Involved in the cellular response to oxidative stress (PubMed:16730026, PubMed:19648921)","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/P32322/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PYCR1","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"ANAPC16","stoichiometry":0.2},{"gene":"ANAPC2","stoichiometry":0.2},{"gene":"ANAPC4","stoichiometry":0.2},{"gene":"CDC23","stoichiometry":0.2},{"gene":"EIF4A1","stoichiometry":0.2},{"gene":"HNRNPH1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PYCR1","total_profiled":1310},"omim":[{"mim_id":"616603","title":"CUTIS LAXA, AUTOSOMAL DOMINANT 3; ADCL3","url":"https://www.omim.org/entry/616603"},{"mim_id":"616408","title":"PYRROLINE-5-CARBOXYLATE REDUCTASE-LIKE; PYCRL","url":"https://www.omim.org/entry/616408"},{"mim_id":"616406","title":"PYRROLINE-5-CARBOXYLATE REDUCTASE 2; PYCR2","url":"https://www.omim.org/entry/616406"},{"mim_id":"614438","title":"CUTIS LAXA, AUTOSOMAL RECESSIVE, TYPE IIIB; ARCL3B","url":"https://www.omim.org/entry/614438"},{"mim_id":"614258","title":"POLYMERASE III, RNA, SUBUNIT A; POLR3A","url":"https://www.omim.org/entry/614258"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"pancreas","ntpm":105.4},{"tissue":"salivary gland","ntpm":114.0}],"url":"https://www.proteinatlas.org/search/PYCR1"},"hgnc":{"alias_symbol":["P5C"],"prev_symbol":[]},"alphafold":{"accession":"P32322","domains":[{"cath_id":"3.40.50.720","chopping":"2-167","consensus_level":"high","plddt":97.4408,"start":2,"end":167},{"cath_id":"1.10.3730.10","chopping":"175-231","consensus_level":"medium","plddt":98.5389,"start":175,"end":231}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P32322","model_url":"https://alphafold.ebi.ac.uk/files/AF-P32322-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P32322-F1-predicted_aligned_error_v6.png","plddt_mean":89.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PYCR1","jax_strain_url":"https://www.jax.org/strain/search?query=PYCR1"},"sequence":{"accession":"P32322","fasta_url":"https://rest.uniprot.org/uniprotkb/P32322.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P32322/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P32322"}},"corpus_meta":[{"pmid":"19648921","id":"PMC_19648921","title":"Mutations 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chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/40891362","citation_count":3,"is_preprint":false},{"pmid":"41016381","id":"PMC_41016381","title":"Crystallographic fragment screening reveals new starting points for PYCR1 inhibitor design.","date":"2025","source":"Bioorganic chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/41016381","citation_count":3,"is_preprint":false},{"pmid":"40542176","id":"PMC_40542176","title":"Effect and mechanism of PYCR1 on biological function of hepatocellular carcinoma cells under hypoxia.","date":"2025","source":"Discover oncology","url":"https://pubmed.ncbi.nlm.nih.gov/40542176","citation_count":3,"is_preprint":false},{"pmid":"35731336","id":"PMC_35731336","title":"Circ_0000705 facilitates proline metabolism of esophageal squamous cell carcinoma cells by targeting miR-621/PYCR1 axis.","date":"2022","source":"Discover 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CII","url":"https://pubmed.ncbi.nlm.nih.gov/40848149","citation_count":2,"is_preprint":false},{"pmid":"39170313","id":"PMC_39170313","title":"ITPKA phosphorylates PYCR1 and promotes the progression of glioma.","date":"2024","source":"Heliyon","url":"https://pubmed.ncbi.nlm.nih.gov/39170313","citation_count":2,"is_preprint":false},{"pmid":"36495058","id":"PMC_36495058","title":"Metabolomic and transcriptomic studies of improvements in myocardial infarction due to Pycr1 deletion.","date":"2022","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/36495058","citation_count":2,"is_preprint":false},{"pmid":"40102683","id":"PMC_40102683","title":"PYCR1 Promotes Esophageal Squamous Cell Carcinoma by Interacting With EGFR to Affecting the PI3K/Akt/mTOR Signaling Pathway.","date":"2025","source":"The journal of gene medicine","url":"https://pubmed.ncbi.nlm.nih.gov/40102683","citation_count":2,"is_preprint":false},{"pmid":"41254241","id":"PMC_41254241","title":"PYCR1 drives lung cancer progression through functional interactions with EGFR and TLR signaling pathways.","date":"2025","source":"Experimental & molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41254241","citation_count":1,"is_preprint":false},{"pmid":"41233804","id":"PMC_41233804","title":"Glutamine metabolism reprogramming promotes bladder cancer progression via PYCR1: a multi-omics and functional validation study.","date":"2025","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41233804","citation_count":1,"is_preprint":false},{"pmid":"36296354","id":"PMC_36296354","title":"Functional Characterization of Saccharomyces cerevisiae P5C Reductase, the Enzyme at the Converging Point of Proline and Arginine Metabolism.","date":"2022","source":"Microorganisms","url":"https://pubmed.ncbi.nlm.nih.gov/36296354","citation_count":1,"is_preprint":false},{"pmid":"40932053","id":"PMC_40932053","title":"PYCR1 inhibition in bone marrow stromal cells enhances bortezomib sensitivity in multiple myeloma cells by altering their metabolism.","date":"2025","source":"Molecular oncology","url":"https://pubmed.ncbi.nlm.nih.gov/40932053","citation_count":1,"is_preprint":false},{"pmid":"40243904","id":"PMC_40243904","title":"The Proline Dehydrogenase Gene CsProDH1 Regulates Homeostasis of the Pro-P5C Cycle Under Drought Stress in Tea Plants.","date":"2025","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/40243904","citation_count":1,"is_preprint":false},{"pmid":"41665114","id":"PMC_41665114","title":"Integrating virtual screening and molecular dynamics simulations to identify emodin as a PYCR1 inhibitor modulating docetaxel sensitivity in prostate cancer.","date":"2026","source":"Journal of enzyme inhibition and medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/41665114","citation_count":1,"is_preprint":false},{"pmid":"1898390","id":"PMC_1898390","title":"Possible involvement of a L-delta 1-pyrroline-5-carboxylate (P5C) reductase in the synthesis of proline in Desulfovibrio desulfuricans Norway.","date":"1991","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/1898390","citation_count":1,"is_preprint":false},{"pmid":"40706441","id":"PMC_40706441","title":"9-Deazaadenosine directly binds PYCR1 and inhibits cancer cell proliferation through disruption of NAD+ metabolism.","date":"2025","source":"Translational oncology","url":"https://pubmed.ncbi.nlm.nih.gov/40706441","citation_count":0,"is_preprint":false},{"pmid":"41975648","id":"PMC_41975648","title":"[Research Progress on the Role and Mechanisms of PYCR1 
in Tumorigenesis and Progression].","date":"2026","source":"Zhongguo fei ai za zhi = Chinese journal of lung cancer","url":"https://pubmed.ncbi.nlm.nih.gov/41975648","citation_count":0,"is_preprint":false},{"pmid":"39172257","id":"PMC_39172257","title":"Confirming the enzymatic activity and neurodevelopmental trajectory of PYCR1 mutation in one child with autosomal-recessive cutis laxa type 2.","date":"2024","source":"Molecular genetics and genomics : MGG","url":"https://pubmed.ncbi.nlm.nih.gov/39172257","citation_count":0,"is_preprint":false},{"pmid":"40294939","id":"PMC_40294939","title":"[A pan-cancer analysis of PYCR1 and its predictive value for chemotherapy and immunotherapy responses in bladder cancer].","date":"2025","source":"Nan fang yi ke da xue xue bao = Journal of Southern Medical University","url":"https://pubmed.ncbi.nlm.nih.gov/40294939","citation_count":0,"is_preprint":false},{"pmid":"41810929","id":"PMC_41810929","title":"PYCR1 Downregulation Induces Autophagy Dependent Apoptosis Through Inhibiting PI3K/AKT/mTOR Axis in Human Hepatocellular Carcinoma Cells.","date":"2026","source":"Analytical cellular pathology (Amsterdam)","url":"https://pubmed.ncbi.nlm.nih.gov/41810929","citation_count":0,"is_preprint":false},{"pmid":"41839921","id":"PMC_41839921","title":"Study on the effects and mechanisms of M2 macrophages on PYCR1-promoted biological behavior of hepatocellular carcinoma cells.","date":"2026","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/41839921","citation_count":0,"is_preprint":false},{"pmid":"41749247","id":"PMC_41749247","title":"Multi-omics analyses related to mitochondria and ageing in triple-negative breast cancer implicate PYCR1 potentiates tumor progression.","date":"2026","source":"Cancer cell international","url":"https://pubmed.ncbi.nlm.nih.gov/41749247","citation_count":0,"is_preprint":false},{"pmid":"39739984","id":"PMC_39739984","title":"Successful Reduction of a Dislocated Hip Joint in a Patient With Cutis Laxa From a PYCR1 Mutation: Case Report.","date":"2024","source":"JBJS case connector","url":"https://pubmed.ncbi.nlm.nih.gov/39739984","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":44935,"output_tokens":8500,"usd":0.131153,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":18156,"output_tokens":5996,"usd":0.12034,"stage2_stop_reason":"end_turn"},"total_usd":0.251493,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"PYCR1 protein localizes to mitochondria; loss-of-function mutations cause altered mitochondrial morphology, reduced membrane potential, and increased apoptosis under oxidative stress in patient fibroblasts; knockdown of orthologs in Xenopus and zebrafish causes epidermal hypoplasia with massive apoptosis.\",\n      \"method\": \"Subcellular fractionation/localization, patient fibroblast functional assays, morpholino knockdown in Xenopus and zebrafish\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (localization, membrane potential, apoptosis assays, two vertebrate knockdown models), replicated across multiple patient kindreds\",\n      \"pmids\": [\"19648921\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"DJ-1 (PARK7 gene product) directly binds PYCR1 both in vivo and in vitro; DJ-1 enhances PYCR1 enzymatic activity in vitro; both proteins co-localize in mitochondria; epistasis experiments (double knockdown showing no additivity) place them on the same anti-oxidative stress pathway.\",\n      \"method\": \"Co-immunoprecipitation, in vitro binding assay, in vitro enzymatic activity assay, fluorescence co-localization, genetic epistasis (double knockdown)\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — reciprocal in vivo/in vitro binding, enzymatic activity measurement, co-localization, and epistasis in single study with multiple orthogonal methods\",\n      \"pmids\": [\"23743200\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PYCR1 physically interacts with RRM2B (ribonucleotide reductase small subunit B) and PYCR2 as components of the same protein complex; dual silencing of PYCR1 and PYCR2 causes mitochondrial network fragmentation and hypersensitivity to oxidative stress, and abolishes the anti-oxidation activity of RRM2B overexpression.\",\n      \"method\": \"Large-scale Flag-RRM2B complex purification followed by mass spectrometry identification; shRNA silencing with oxidative stress phenotypic readout\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-identified complex plus functional rescue assay in single lab\",\n      \"pmids\": [\"26733354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In IDH1-R132H mutant cells, enhanced PYCR1 activity oxidizes NADH to NAD+ during proline synthesis from glutamine, thereby partially uncoupling the electron transport chain from TCA cycle activity and maintaining a lower NADH/NAD+ ratio.\",\n      \"method\": \"Stable isotope tracing (glutamine-derived proline), NADH/NAD+ ratio measurement, oxygen consumption assays, PYCR1 activity assays in IDH1-mutant vs. wild-type cells\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — metabolic flux tracing with multiple metabolic readouts, mechanistic link to redox homeostasis established in single rigorous study\",\n      \"pmids\": [\"29562167\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SIRT3 deacetylates PYCR1 at lysine K228; CBP is the acetyltransferase that acetylates PYCR1 at K228; acetylation at K228 reduces PYCR1 enzymatic activity by impairing formation of the PYCR1 decamer; SIRT3-mediated deacetylation increases PYCR1 activity and promotes cell proliferation.\",\n      \"method\": \"Immunoprecipitation and mass spectrometry to identify SIRT3-PYCR1 interaction; in vitro binding; site-directed mutagenesis (K228); enzymatic activity assays; native PAGE to assess oligomeric state\",\n      \"journal\": \"Neoplasia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro and in vivo binding, mutagenesis of acetylation site, enzymatic activity measurement, oligomer state analysis, all in one study\",\n      \"pmids\": [\"31108370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"PYCR1 directly interacts with STAT3 (demonstrated by co-immunoprecipitation); STAT3 overexpression partially reverses the effects of PYCR1 knockdown on proliferation, drug resistance, and EMT in colorectal cancer cells, placing PYCR1 upstream of STAT3-mediated p38 MAPK and NF-κB signaling.\",\n      \"method\": \"Co-immunoprecipitation (CoIP) assay; siRNA knockdown with STAT3 overexpression rescue; Western blot for pathway proteins\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — single CoIP plus rescue experiment, single lab\",\n      \"pmids\": [\"31606203\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Mitochondrial Lon chaperone protein binds PYCR1 as a client; Lon-dependent PYCR1 activity induces mitochondrial ROS production, which drives EMT via p38 and NF-κB signaling in cancer cells.\",\n      \"method\": \"Protein-protein interaction identification (Lon-PYCR1 client relationship), ROS measurement, EMT marker assays, signaling pathway Western blots\",\n      \"journal\": \"Cancer letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — client-chaperone interaction identified with functional downstream readouts, single lab\",\n      \"pmids\": [\"31987921\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In hypoxic conditions, mitochondrial PYCR1 activity is increased; PYCR1 oxidizes NADH coupled to proline synthesis, permitting continued TCA cycle activity; loss of PYCR1 leads to increased hypoxia in vivo and in 3D culture, resulting in widespread cell death.\",\n      \"method\": \"PYCR1 knockdown/knockout under hypoxic conditions; metabolic flux assays; 3D spheroid culture; in vivo tumor models with hypoxia imaging\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — loss-of-function with multiple orthogonal readouts (metabolic flux, 3D culture, in vivo), mechanistic link to TCA cycle redox balance established\",\n      \"pmids\": [\"35108535\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PYCR1 knockdown in lung adenocarcinoma (LUAD) significantly increases phosphorylation of JAK2 and STAT3 and elevates Bcl-2 and c-Myc expression, indicating that PYCR1 activity suppresses JAK/STAT signaling in LUAD cells.\",\n      \"method\": \"siRNA knockdown, Western blot for JAK2 and STAT3 phosphorylation, functional proliferation/migration assays\",\n      \"journal\": \"Molecular carcinogenesis\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, single method (Western blot for signaling), no direct mechanistic link established\",\n      \"pmids\": [\"32133692\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"USP18 deubiquitinates FTO post-translationally, increasing FTO protein levels; elevated FTO then demethylates N6-methyladenosine (m6A) on PYCR1 mRNA, stabilizing the transcript and increasing PYCR1 protein in bladder cancer.\",\n      \"method\": \"Western blot for protein levels, m6A modification assays, mRNA stability assays, FTO enzymatic activity\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — post-translational regulation of upstream enzyme plus mRNA m6A modification of PYCR1 demonstrated with multiple assays, single lab\",\n      \"pmids\": [\"33461172\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Both PYCR1 and PYCR2 localize to mitochondria in fibroblasts; both can complement loss of yeast Pro3 (the yeast P5C-to-proline enzyme), confirming their enzymatic activity as P5C reductases; Pycr1 and Pycr2 double-mutant mice are sub-viable, indicating the genes are largely functionally redundant in proline biosynthesis.\",\n      \"method\": \"Fluorescence localization in fibroblasts; yeast complementation assay; mouse genetics (single and double null alleles)\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — enzymatic complementation in yeast, mitochondrial localization confirmed, genetic redundancy established by double-mutant lethality\",\n      \"pmids\": [\"33734376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PYCR1 is the key enzyme for de novo proline synthesis from glutamine in cancer-associated fibroblasts (CAFs); reducing PYCR1 levels in CAFs decreases tumor collagen production, tumor growth, and metastatic spread; proline synthesis in CAFs is epigenetically upregulated by increased pyruvate dehydrogenase-derived acetyl-CoA levels.\",\n      \"method\": \"Stable isotope tracing (glutamine-to-proline in CAFs), PYCR1 knockdown in CAFs, in vivo xenograft models, collagen quantification\",\n      \"journal\": \"Nature metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — metabolic flux tracing plus in vivo functional validation with multiple endpoints in single rigorous study\",\n      \"pmids\": [\"35760868\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PYCR1 overexpression inhibits lipid reactive oxygen species (ROS) production and promotes SLC25A10 expression in colorectal cancer cells; SLC25A10 overexpression reverses the anti-tumor effects of PYCR1 silencing, placing SLC25A10 downstream of PYCR1 in ferroptosis resistance.\",\n      \"method\": \"PYCR1 overexpression/silencing, lipid ROS measurement, ferroptosis inhibitor/inducer pharmacological experiments, SLC25A10 overexpression rescue\",\n      \"journal\": \"Human cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional epistasis by rescue experiment, multiple phenotypic readouts, single lab\",\n      \"pmids\": [\"36104652\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SENP3 promotes STAT3 deSUMOylation, increasing nuclear STAT3; nuclear STAT3 then directly binds the PYCR1 gene promoter to transcriptionally upregulate PYCR1 expression in bladder cancer.\",\n      \"method\": \"SENP3/STAT3 Western blot and nuclear fractionation; STAT3 promoter binding to PYCR1 (inferred from context of transcription factor function on PYCR1 promoter)\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional regulatory axis shown with multiple knockdown/overexpression experiments and rescue; direct promoter binding assay referenced but details limited in abstract\",\n      \"pmids\": [\"36227136\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"CRIF1 promotes PYCR1 deacetylation and increased enzymatic activity via SIRT3; PYCR1 deacetylation reverses the anti-tumor effect of CRIF1 knockdown in NSCLC cells, placing CRIF1-SIRT3-PYCR1 in the same pathway.\",\n      \"method\": \"SIRT3-mediated deacetylation assay, PYCR1 enzymatic activity assays, CRIF1 knockdown with PYCR1 deacetylation rescue, flow cytometry for apoptosis\",\n      \"journal\": \"Journal of molecular histology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — enzymatic activity assay plus epistatic rescue experiment; replicates SIRT3-PYCR1 deacetylation axis from prior work\",\n      \"pmids\": [\"35716330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Under hypoxia, nuclear IGF1R phosphorylates PYCR1 at Tyrosine 135; this phosphorylation promotes PYCR1 binding to ELK4 transcription factor and recruitment to ELK4-target gene promoters; PYCR1-catalyzed NAD+ production stimulates Sirt7 deacetylase activity on H3K18ac, mediating transcriptional repression and supporting tumor cell growth under hypoxia.\",\n      \"method\": \"Phosphorylation site identification (Y135), co-immunoprecipitation (PYCR1-ELK4), ChIP assay (PYCR1 at gene promoters), enzymatic NAD+ production assay, Sirt7 deacetylase activity assay, PYCR1 Y135 phosphomutant functional assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods: phosphosite identification, protein-protein interaction, ChIP, enzymatic activity, mutagenesis functional assays\",\n      \"pmids\": [\"37777542\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PYCR1 promotes NSCLC progression through JAK-STAT3 signaling, which is mediated via PRODH-dependent glutamine synthesis; PYCR1 activates STAT3 phosphorylation and promotes PD-L1 transcription by elevating STAT3 binding to the PD-L1 gene promoter.\",\n      \"method\": \"PYCR1 overexpression with siPRODH and STAT3 inhibitor (stattic) rescue; ChIP assay for STAT3 binding to PD-L1 promoter; luciferase assay for PD-L1 transcription\",\n      \"journal\": \"Translational oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and luciferase confirm transcriptional mechanism; rescue with inhibitors places pathway; single lab\",\n      \"pmids\": [\"37018868\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PYCR1 interacts with EGFR by co-immunoprecipitation; PYCR1 knockout inhibits proliferation, migration, and colony formation; in NSCLC, PYCR1 stabilizes EGFR by forming a complex with EGFR and USP11, enhancing EGFR deubiquitination and stability; PYCR1 also promotes TLR signaling by interacting with TRAF6, TAK1, ECSIT, and TAB2, facilitating their ubiquitination and NF-κB activation.\",\n      \"method\": \"CRISPR-Cas9 PYCR1-KO, co-immunoprecipitation, mass spectrometry, EGFR ubiquitination assay, NF-κB activation assay, pharmacological inhibition with PYCR1-IN-1\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR KO with multiple molecular interaction methods (CoIP, MS, ubiquitination assay), single lab\",\n      \"pmids\": [\"41254241\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PYCR1 interacts with EGFR (co-immunoprecipitation); aerobic glycolysis and the EGFR/PI3K/AKT pathway are required downstream of PYCR1 in bladder cancer; EGFR inhibitor CL-387785 inhibits the EGFR/PI3K/AKT pathway and attenuates effects of PYCR1 overexpression but has no effect on PYCR1 expression itself.\",\n      \"method\": \"Co-immunoprecipitation, PYCR1 knockdown/overexpression, EGFR inhibitor treatment, glycolysis assays\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — CoIP plus pharmacological rescue; replicated PYCR1-EGFR interaction across two papers\",\n      \"pmids\": [\"37293856\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"BHLHE41 directly interacts with PYCR1 (co-immunoprecipitation); BHLHE41 decreases PYCR1 protein stability by promoting its ubiquitination and proteasomal degradation, thereby inactivating the PI3K/AKT signaling pathway in bladder cancer.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, protein stability assays, rescue experiments with PYCR1 overexpression\",\n      \"journal\": \"European journal of medical research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — CoIP, ubiquitination, and rescue assays in single lab study\",\n      \"pmids\": [\"38811952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"ITPKA kinase interacts with PYCR1 and phosphorylates PYCR1 at serine 29; this phosphorylation inhibits E3 ligase Stub1-mediated ubiquitination of PYCR1, thereby stabilizing PYCR1 protein and contributing to glioma progression.\",\n      \"method\": \"Protein-protein interaction (co-immunoprecipitation), phosphorylation site identification (S29), ubiquitination assay, protein stability assay\",\n      \"journal\": \"Heliyon\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — phosphosite identified with ubiquitination and stability assays, single lab\",\n      \"pmids\": [\"39170313\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PYCR1 knockout in liver cancer cells inhibits glycolysis and reduces H3K18 lactylation of the IRS1 histone, thereby inhibiting IRS1 expression; this pathway links PYCR1 activity to metabolic gene regulation via histone lactylation.\",\n      \"method\": \"PYCR1 knockout, metabolomics, transcriptome sequencing, ChIP assay for H3K18 lactylation at IRS1 promoter\",\n      \"journal\": \"Clinical and translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP for histone modification plus metabolomics and transcriptomics; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"39422696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PYCR1 interacts with EGFR and promotes esophageal squamous cell carcinoma progression and metastasis by activating the PI3K/AKT/mTOR signaling pathway; EGFR overexpression reverses the inhibitory effects of PYCR1 knockdown.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, immunofluorescence, proteomic analysis, EGFR overexpression rescue, in vivo xenograft\",\n      \"journal\": \"The journal of gene medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — CoIP/MS identification plus rescue experiment; independent replication of PYCR1-EGFR interaction across cancer types\",\n      \"pmids\": [\"40102683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The micropeptide TREMP (encoded by lincR-PPP2R5C) localizes to mitochondria and interacts with PYCR1; this interaction enhances glycolysis and promotes Th2 cell differentiation; PYCR1 knockout mice show attenuated allergic airway inflammation similar to TREMP knockout mice.\",\n      \"method\": \"Co-immunoprecipitation (TREMP-PYCR1), CRISPR PYCR1-KO mice, glycolysis measurement, Th2 differentiation assays, in vivo HDM allergy model\",\n      \"journal\": \"Allergology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CoIP, KO mouse model, metabolic and immunological readouts in single study\",\n      \"pmids\": [\"39025723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Homozygous missense mutation p.Ala187Thr in PYCR1 decreases enzymatic activity in vitro; 3D structural modeling shows the mutation alters hydrogen bonds causing protein misfolding.\",\n      \"method\": \"In vitro enzymatic activity assay of mutant vs. wild-type PYCR1, 3D structural modeling\",\n      \"journal\": \"Molecular genetics and genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic assay is Tier 1 but single lab, single patient mutation study\",\n      \"pmids\": [\"39172257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PYCR1 can reduce Δ1-piperideine-6-carboxylate (P6C) to L-pipecolic acid with a Km of similar magnitude to its Km for P5C-to-proline conversion; this was confirmed using urine from antiquitin-deficient patients accumulating P6C, demonstrating PYCR1 has an alternative substrate in lysine degradation.\",\n      \"method\": \"In vitro enzymatic assay with commercial PYCR1 and P6C substrate; LC-MS/MS quantification of substrate/product; confirmation with patient urine samples\",\n      \"journal\": \"Journal of inherited metabolic disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic reconstitution with kinetic parameters plus biological validation using patient material\",\n      \"pmids\": [\"24431009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"X-ray crystal structure of human PYCR1 complexed with N-formyl-L-proline (NFLP) reveals that inhibitor binding induces conformational changes in the active site including translation of an α-helix by 1 Å; NFLP competitively inhibits PYCR1 with respect to P5C substrate (Ki = 100 μM) and phenocopies PYCR1 knockdown in breast cancer cells by inhibiting de novo proline biosynthesis.\",\n      \"method\": \"X-ray crystallography (co-crystal structure), competitive inhibition kinetics, cell-based proline biosynthesis assay, spheroid growth assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus kinetic mechanism determination plus cell-based functional validation in single rigorous study\",\n      \"pmids\": [\"33109600\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Fragment-based crystallographic screening identified eight fragment hits binding to human PYCR1; novel fragments block both the P5C substrate pocket and the NAD(P)H binding site (dual-site binders); four hits show enzymatic inhibition, demonstrating the active site architecture accommodates dual-site inhibitors.\",\n      \"method\": \"X-ray crystallography fragment screening (22% hit rate), kinetic inhibition assays\",\n      \"journal\": \"Journal of chemical information and modeling\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structures plus kinetic assays defining active site and binding pockets in single rigorous study\",\n      \"pmids\": [\"38411104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Crystallographic fragment screening against PYCR1 revealed ligands occupying P5C and NADH binding pockets including dual-site ligands; sulfonamide and sulfamate groups are isosteric replacements for the carboxylate in the active site; a cryptic subpocket near the nicotinamide-binding site was identified; ligand-induced conformational changes were confirmed by molecular dynamics to be intrinsically accessible.\",\n      \"method\": \"X-ray crystallography (12 co-crystal structures), molecular dynamics simulations\",\n      \"journal\": \"Bioorganic chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple crystal structures defining active site plasticity in single rigorous study\",\n      \"pmids\": [\"41016381\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SMYD2 methyltransferase upregulates PYCR1 expression through H3K4me3 histone modification at the PYCR1 locus; elevated PYCR1 subsequently activates the PINK1/Parkin mitophagy pathway, supporting bladder cancer stem cell stemness maintenance.\",\n      \"method\": \"H3K4me3 ChIP assay at PYCR1 promoter, siRNA knockdown of SMYD2/PYCR1, mitophagy markers (LC3B, PINK1, Parkin), cancer stem cell assays\",\n      \"journal\": \"International journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP confirms epigenetic regulation, functional pathway established by rescue, single lab\",\n      \"pmids\": [\"40341538\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FOXA1 transcription factor directly activates PYCR1 transcription (ChIP assay); elevated PYCR1 activates autophagy in LUAD cells, which suppresses CD8+ T cell-mediated anti-tumor killing; PYCR1 overexpression reverses the effect of FOXA1 knockdown.\",\n      \"method\": \"ChIP assay (FOXA1 binding to PYCR1 promoter), dual-luciferase assay, PYCR1 knockdown/overexpression, CD8+ T cell cytotoxicity assay, in vivo mouse experiments\",\n      \"journal\": \"Cancer immunology, immunotherapy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and luciferase confirm transcriptional regulation, rescue experiments establish pathway, single lab\",\n      \"pmids\": [\"40848149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Hypomethylation at a CpG island in the PYCR1 promoter and p300-induced H3K27ac modification at the PYCR1 promoter both contribute to PYCR1 transcriptional upregulation in gastric cancer.\",\n      \"method\": \"DNA methylation analysis (bisulfite sequencing/bioinformatics), ChIP for H3K27ac, p300 acetyltransferase functional experiments\",\n      \"journal\": \"Biochimica et biophysica acta. Gene regulatory mechanisms\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP and methylation analysis with functional validation, single lab\",\n      \"pmids\": [\"35654390\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Pycr1 knockout zebrafish show markedly reduced proline and extracellular matrix contents, lowered energy, diminished superoxide dismutase and telomerase activity, increased apoptosis and senescence from embryo stage, and a progeria-like phenotype; adult pycr1 KO fish display reduced locomotion, aggression, social interaction, and dysregulated circadian rhythm.\",\n      \"method\": \"CRISPR/Cas9 pycr1 knockout zebrafish, biochemical assays (proline, ECM, ATP, SOD, telomerase), apoptosis/senescence staining, behavioral testing\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — complete KO in vertebrate model with multiple biochemical and behavioral readouts establishing roles in proline synthesis, redox defense, and aging\",\n      \"pmids\": [\"31091804\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PYCR1 regulates TRAIL resistance in NSCLC by preventing redistribution of death receptors (DRs) to the plasma membrane; PYCR1 knockdown increases DR surface localization, activates Caspase-3/8, and sensitizes cells to TRAIL-induced apoptosis; PYCR1 overexpression reduces DR surface distribution and suppresses Caspase-3/8 activation.\",\n      \"method\": \"PYCR1 knockdown/overexpression, flow cytometry for surface DR localization, Caspase-3/8 activity assays, TRAIL sensitivity assays\",\n      \"journal\": \"Oncology letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — functional mechanism (DR redistribution) established with flow cytometry and caspase assays, single lab\",\n      \"pmids\": [\"38549801\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PYCR1 is a mitochondrial enzyme that catalyzes the final NAD(P)H-dependent reduction of Δ1-pyrroline-5-carboxylate (P5C) to L-proline (and can also reduce Δ1-piperideine-6-carboxylate to L-pipecolic acid), thereby linking proline biosynthesis to cellular redox homeostasis by oxidizing NADH/NADPH; its enzymatic activity is regulated post-translationally by SIRT3-mediated deacetylation at K228 (which promotes active decamer formation), CBP-mediated acetylation (which inhibits it), ITPKA-mediated phosphorylation at S29 (which stabilizes it against ubiquitin-mediated degradation by Stub1), and IGF1R-mediated phosphorylation at Y135 (which drives nuclear localization and recruitment to ELK4 target gene promoters to regulate transcription via Sirt7-dependent H3K18ac deacetylation); in the mitochondria it physically interacts with DJ-1 (which enhances its activity), RRM2B, the Lon chaperone, and a TREMP micropeptide, collectively supporting oxidative stress resistance; its transcription is controlled by STAT3 (downstream of SENP3-deSUMOylation), FOXA1, SMYD2-mediated H3K4me3, and promoter hypomethylation; in cancer-associated fibroblasts PYCR1-driven proline synthesis fuels collagen production and tumor-promoting extracellular matrix remodeling, while in cancer cells it supports TCA cycle activity under hypoxia, inhibits ferroptosis via SLC25A10, regulates EGFR stability via a PYCR1-USP11 deubiquitination complex, and modulates TLR/NF-κB and PI3K/AKT/mTOR signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PYCR1 is a mitochondrial enzyme that catalyzes the final NAD(P)H-dependent reduction of Δ1-pyrroline-5-carboxylate (P5C) to L-proline, coupling de novo proline biosynthesis to cellular redox balance and oxidative-stress resistance [#10, #26]. Crystallographic and kinetic work defines an active site with adjacent P5C-substrate and NAD(P)H-binding pockets that accommodate competitive and dual-site inhibitors and undergoes conformational change on ligand binding [#26, #27, #28], and the enzyme also reduces Δ1-piperideine-6-carboxylate to L-pipecolic acid, giving it a role in lysine degradation [#25]. Its catalytic output is redox-directed: by oxidizing NADH to NAD+ during proline synthesis, PYCR1 lowers the NADH/NAD+ ratio and sustains TCA-cycle flux under IDH1-mutant and hypoxic conditions, with loss of PYCR1 driving hypoxia and cell death in tumors [#3, #7]. Enzyme activity is tuned post-translationally through SIRT3-mediated deacetylation at K228, which favors active-decamer formation and opposes CBP acetylation [#4, #14], while protein stability is controlled by phosphorylation-coupled ubiquitination involving ITPKA/Stub1 [#20] and BHLHE41 [#19]. Beyond catalysis, hypoxic IGF1R-driven phosphorylation at Y135 recruits nuclear PYCR1 to ELK4 target promoters where its NAD+ production fuels Sirt7-dependent H3K18ac removal, linking the enzyme to transcriptional control [#15]. PYCR1 supports oxidative-stress defense via direct interaction with DJ-1 (PARK7) and assembly with RRM2B/PYCR2 [#1, #2], and in cancer-associated fibroblasts its proline output drives collagen production and extracellular-matrix remodeling that promote tumor growth and metastasis [#11]. Loss-of-function PYCR1 mutations cause a connective-tissue/progeroid phenotype with mitochondrial dysfunction, increased apoptosis under oxidative stress, and reduced enzymatic activity from misfolding-prone alleles [#0, #24].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Established that PYCR1 is a mitochondrial protein whose loss compromises mitochondrial integrity and survival, framing it as a redox/stress-resistance factor rather than a purely metabolic enzyme.\",\n      \"evidence\": \"Subcellular fractionation, patient fibroblast membrane-potential and apoptosis assays, and morpholino knockdown in Xenopus and zebrafish\",\n      \"pmids\": [\"19648921\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the catalytic mechanism linking PYCR1 to membrane potential\", \"Did not identify protein partners mediating stress resistance\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified a direct partner (DJ-1/PARK7) that enhances PYCR1 activity, placing PYCR1 on a defined anti-oxidative-stress pathway.\",\n      \"evidence\": \"Reciprocal Co-IP, in vitro binding, in vitro activity assay, co-localization, and double-knockdown epistasis\",\n      \"pmids\": [\"23743200\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of DJ-1 binding not resolved\", \"Whether DJ-1 alters oligomeric state untested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated PYCR1 has a second substrate, reducing P6C to pipecolic acid, extending its role to lysine degradation.\",\n      \"evidence\": \"In vitro kinetic assay with commercial PYCR1 plus LC-MS/MS, validated with antiquitin-deficient patient urine\",\n      \"pmids\": [\"24431009\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological significance of pipecolic acid synthesis in vivo unquantified\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Placed PYCR1 in a higher-order complex with RRM2B and PYCR2 required for RRM2B-mediated oxidative protection.\",\n      \"evidence\": \"Flag-RRM2B complex purification with MS plus shRNA silencing under oxidative stress\",\n      \"pmids\": [\"26733354\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and direct vs. indirect contacts within the complex unknown\", \"Single-lab finding without reciprocal pulldown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected PYCR1 catalysis to redox homeostasis by showing it oxidizes NADH to NAD+ to lower the NADH/NAD+ ratio in IDH1-mutant cells, partially uncoupling the ETC from the TCA cycle.\",\n      \"evidence\": \"Glutamine-to-proline isotope tracing, NADH/NAD+ measurement, oxygen consumption, and activity assays\",\n      \"pmids\": [\"29562167\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generality beyond IDH1-mutant context not addressed here\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined post-translational control of PYCR1 activity through SIRT3 deacetylation and CBP acetylation at K228 governing decamer assembly.\",\n      \"evidence\": \"IP-MS, in vitro binding, K228 mutagenesis, activity assays, and native PAGE oligomer analysis\",\n      \"pmids\": [\"31108370\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stimuli that trigger SIRT3/CBP switching on PYCR1 not defined\", \"Whether other lysines are modified untested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Linked PYCR1 to signaling control by showing it interacts with STAT3 and acts upstream of STAT3-mediated proliferation and EMT programs.\",\n      \"evidence\": \"Co-IP and siRNA knockdown with STAT3 overexpression rescue in colorectal cancer cells\",\n      \"pmids\": [\"31606203\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs. indirect PYCR1-STAT3 binding not resolved by reciprocal validation\", \"Mechanism connecting enzyme activity to STAT3 unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showed PYCR1 activity rises under hypoxia and sustains TCA-cycle flux, making it required for tumor cell survival in low-oxygen microenvironments.\",\n      \"evidence\": \"Loss-of-function with metabolic flux, 3D spheroid, and in vivo hypoxia imaging\",\n      \"pmids\": [\"35108535\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How hypoxia increases PYCR1 activity mechanistically not fully defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Implicated a Lon chaperone-PYCR1 client relationship and downstream ROS/EMT signaling in cancer cells.\",\n      \"evidence\": \"Lon-PYCR1 interaction, ROS measurement, EMT markers, and signaling Western blots\",\n      \"pmids\": [\"31987921\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether Lon regulates PYCR1 folding or stability directly untested\", \"Single-lab functional readouts\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Confirmed PYCR1 and PYCR2 are functionally redundant P5C reductases by yeast complementation and double-mutant mouse lethality.\",\n      \"evidence\": \"Fibroblast localization, yeast Pro3 complementation, and single/double-null mouse genetics\",\n      \"pmids\": [\"33734376\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specific division of labor between PYCR1 and PYCR2 not delineated\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified m6A-dependent transcript regulation of PYCR1 via a USP18-FTO axis controlling its protein levels in bladder cancer.\",\n      \"evidence\": \"m6A modification, mRNA stability, FTO activity, and protein-level Western blots\",\n      \"pmids\": [\"33461172\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct FTO occupancy on PYCR1 mRNA sites not mapped\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established PYCR1 as the key proline-synthesizing enzyme in cancer-associated fibroblasts driving collagen and ECM-dependent tumor growth and metastasis.\",\n      \"evidence\": \"Glutamine-to-proline isotope tracing in CAFs, PYCR1 knockdown, xenografts, and collagen quantification\",\n      \"pmids\": [\"35760868\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which acetyl-CoA epigenetically upregulates proline synthesis not fully detailed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Consolidated transcriptional and epigenetic control of PYCR1 through STAT3/SENP3, promoter hypomethylation, and p300-H3K27ac, plus a SIRT3-dependent CRIF1 input on activity.\",\n      \"evidence\": \"Promoter binding/ChIP, methylation analysis, and SIRT3 deacetylation rescue across bladder, gastric, and NSCLC models\",\n      \"pmids\": [\"36227136\", \"35654390\", \"35716330\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative contribution of each regulatory layer in a given tissue unresolved\", \"Mostly single-lab per-axis findings\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Linked PYCR1 to ferroptosis resistance via SLC25A10, suppressing lipid ROS in colorectal cancer.\",\n      \"evidence\": \"Overexpression/silencing, lipid ROS measurement, ferroptosis pharmacology, and SLC25A10 rescue\",\n      \"pmids\": [\"36104652\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mechanism connecting PYCR1 to SLC25A10 expression unknown\", \"Single-lab epistasis\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Revealed a moonlighting transcriptional role: hypoxic IGF1R phosphorylation at Y135 drives nuclear PYCR1 to ELK4 promoters where NAD+ production fuels Sirt7-dependent H3K18ac deacetylation.\",\n      \"evidence\": \"Phosphosite identification, Co-IP, ChIP, NAD+ and Sirt7 activity assays, and Y135 phosphomutant functional assays\",\n      \"pmids\": [\"37777542\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Breadth of ELK4 target genes regulated this way not mapped\", \"Balance between nuclear and mitochondrial PYCR1 pools undefined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined protein-stability control of PYCR1 by opposing ubiquitin pathways: ITPKA-S29 phosphorylation blocks Stub1 ubiquitination while BHLHE41 promotes its degradation.\",\n      \"evidence\": \"Co-IP, phosphosite identification, ubiquitination and protein-stability assays in glioma and bladder cancer\",\n      \"pmids\": [\"39170313\", \"38811952\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether these inputs converge on the same lysines unknown\", \"Single-lab per-axis evidence\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Positioned PYCR1 as a scaffold/regulator of EGFR stability and TLR/NF-κB signaling through a USP11-EGFR deubiquitination complex and interactions with TRAF6/TAK1/ECSIT/TAB2.\",\n      \"evidence\": \"CRISPR KO, Co-IP, MS, EGFR ubiquitination, and NF-κB activation assays; replicated EGFR interaction across cancers\",\n      \"pmids\": [\"41254241\", \"37293856\", \"40102683\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether EGFR/signaling roles depend on catalytic activity untested\", \"Direct vs. complex-mediated contacts not all reciprocally validated\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed PYCR1 supports immune and apoptotic phenotypes — promoting Th2 differentiation via a mitochondrial TREMP micropeptide and conferring TRAIL resistance by sequestering death receptors from the surface.\",\n      \"evidence\": \"Co-IP, PYCR1-KO mice with airway allergy model; flow cytometry of surface death receptors and caspase assays\",\n      \"pmids\": [\"39025723\", \"38549801\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of death-receptor redistribution unknown\", \"Whether TREMP alters PYCR1 catalysis untested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Provided structural and chemical-biology tools defining the PYCR1 active site, including a co-crystal with a competitive inhibitor and dual-site fragment binders.\",\n      \"evidence\": \"X-ray crystallography (inhibitor co-crystals and fragment screens), kinetic inhibition, MD simulations, and cell-based proline assays\",\n      \"pmids\": [\"33109600\", \"38411104\", \"41016381\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of the active decamer with cofactor in catalytic cycle reported here\", \"Cryptic subpocket druggability in cells unconfirmed\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Tied PYCR1 disease alleles to enzymatic loss-of-function, showing a missense mutation reduces activity via misfolding.\",\n      \"evidence\": \"In vitro activity assay of mutant vs. wild-type plus 3D structural modeling\",\n      \"pmids\": [\"39172257\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single mutation, single patient\", \"Cellular consequences of misfolding not assessed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected PYCR1 to organelle-quality-control and metabolic-gene programs, activating PINK1/Parkin mitophagy for stemness and influencing H3K18-lactylation/autophagy-linked immune evasion.\",\n      \"evidence\": \"ChIP (H3K4me3, H3K18la), metabolomics/transcriptomics, mitophagy markers, CD8+ T-cell cytotoxicity, and in vivo models\",\n      \"pmids\": [\"40341538\", \"39422696\", \"40848149\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal chain from proline/NAD+ output to lactylation and mitophagy not fully resolved\", \"Single-lab per-pathway findings\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single mitochondrial reductase is partitioned between its catalytic, redox-buffering, nuclear-transcriptional, and signaling-scaffold roles — and which roles depend on enzymatic activity versus protein scaffolding — remains unresolved.\",\n      \"evidence\": null,\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model integrating mitochondrial, nuclear, and scaffold functions\", \"Activity-dependence of EGFR/TLR/STAT3 roles untested\", \"Structure of catalytically active decamer with bound cofactor not determined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [10, 25, 26, 3]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [10, 25]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 1, 10, 23]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [3, 7, 11, 25]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [0, 1, 7]}\n    ],\n    \"complexes\": [\n      \"PYCR1-PYCR2-RRM2B complex\",\n      \"PYCR1-EGFR-USP11 deubiquitination complex\"\n    ],\n    \"partners\": [\n      \"PARK7\",\n      \"RRM2B\",\n      \"PYCR2\",\n      \"EGFR\",\n      \"USP11\",\n      \"STAT3\",\n      \"ITPKA\",\n      \"BHLHE41\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"tie","faith_supported":7,"faith_total":7,"faith_pct":100.0}}