{"gene":"PDSS2","run_date":"2026-06-10T05:19:53","timeline":{"discoveries":[{"year":2006,"finding":"PDSS2 encodes a subunit of decaprenyl diphosphate synthase, the first enzyme of the CoQ10 biosynthetic pathway; compound heterozygous mutations in PDSS2 cause a severe defect in decaprenyl diphosphate synthase activity as demonstrated by biochemical assays with radiolabeled substrates in patient fibroblasts.","method":"Biochemical assays with radiolabeled substrates in patient-derived fibroblasts; genetic identification of compound heterozygous mutations","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct enzymatic activity assay with radiolabeled substrates in patient cells, replicated in disease context; foundational mechanistic paper","pmids":["17186472"],"is_preprint":false},{"year":2012,"finding":"In Pdss2 mutant mice, widespread CoQ9 deficiency causes mitochondrial respiratory chain abnormalities; only affected organs (kidney) show increased ROS production, oxidative stress, mitochondrial DNA depletion, and reduced mitochondrial mass (citrate synthase activity), indicating that kidney-specific oxidative stress triggers mitochondrial loss and renal failure.","method":"In vivo mouse model (CBA/Pdss2 kd/kd) at multiple disease stages; ROS measurement, oxidative damage markers, mitochondrial DNA quantification, citrate synthase activity assay","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vivo methods (ROS, oxidative damage, mtDNA, citrate synthase) at multiple disease stages in a defined genetic model","pmids":["23150520"],"is_preprint":false},{"year":2011,"finding":"Pdss2 deficiency in glomerular podocytes (conditional knockout) causes focal segmental glomerulosclerosis-like kidney disease; probucol treatment restores CoQ9 content in mutant kidney and ameliorates nephropathy, while also normalizing PPAR pathway signaling, indicating that decreased CoQ9 and altered PPAR signaling respectively orchestrate glomerular and metabolic consequences.","method":"Pdss2 conditional knockout mouse model; oral probucol treatment; CoQ9 measurement; transcriptional profiling; albuminuria assay","journal":"EMBO molecular medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional genetic model with pharmacological rescue, multiple endpoints (CoQ9 restoration, transcriptomics, albuminuria), multiple orthogonal methods","pmids":["21567994"],"is_preprint":false},{"year":2011,"finding":"Pdss2 knockout during cerebellar development (via Pax2-cre) delays radial glial cell growth and neuronal progenitor migration, increases ectopic apoptosis of neuroblasts, impairs cell proliferation, and causes mitochondrial defects with autophagic vacuolization, leading to cerebellar hypoplasia; Pdss2 knockout in Purkinje cells (Pcp2-cre) causes progressive Purkinje cell loss and ataxia in adulthood.","method":"Conditional knockout mouse lines (Pax2-cre and Pcp2-cre); histology, immunohistochemistry, electron microscopy, behavioral assays","journal":"Neurobiology of disease","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent conditional knockout mouse models with complementary developmental and adult phenotypes, multiple orthogonal methods including electron microscopy","pmids":["21871565"],"is_preprint":false},{"year":2011,"finding":"Conditional Pdss2 knockout targeted to dopaminergic neurons causes deficiencies in tyrosine hydroxylase-positive neurons in the substantia nigra and neuromuscular deficits, implicating CoQ deficiency in dopaminergic neuron loss similar to Parkinson's disease pathology.","method":"Conditional Pdss2 knockout (dopaminergic neuron-specific); behavioral/coordination assays; tyrosine hydroxylase immunostaining","journal":"Mitochondrion","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — conditional genetic model with neurochemical and behavioral readouts, single lab, two orthogonal methods","pmids":["21983691"],"is_preprint":false},{"year":2018,"finding":"Reintroduction of full-length PDSS2 into HCC cells increases CoQ10 levels and mitochondrial electron transport complex I activity, inducing a metabolic shift from aerobic glycolysis to mitochondrial respiration; PDSS2 knockdown induces chromosomal instability and malignant transformation in immortalized liver cells.","method":"Overexpression and knockdown in HCC cell lines; CoQ10 measurement; complex I activity assay; soft agar colony formation; nude mouse xenograft; chromosomal instability assay","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (CoQ10, complex I activity, metabolic flux, in vivo xenograft, chromosomal instability), gain- and loss-of-function in same study","pmids":["29967258"],"is_preprint":false},{"year":2018,"finding":"Five of six alternative splicing isoforms of PDSS2 (lacking exon 2 or other domains) show loss of function in HCC, while only full-length PDSS2 restores CoQ10 biosynthesis and tumor suppressive activity.","method":"Isoform-specific overexpression in HCC cells; CoQ10 measurement; functional assays (colony formation, tumor formation)","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct functional comparison of isoforms, single lab, multiple functional readouts","pmids":["29967258"],"is_preprint":false},{"year":2019,"finding":"Sp1 transcription factor binds to the PDSS2 promoter in vivo and represses PDSS2 transcription; site-directed mutagenesis of Sp1 binding sites abolishes proximal promoter activity; the core PDSS2 promoter is located within 202 bp of the transcription initiation site.","method":"Luciferase reporter assay; site-directed mutagenesis; ChIP assay; Sp1 overexpression; mithramycin A (Sp1 inhibitor) treatment","journal":"Genes","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — ChIP, reporter assay, mutagenesis, pharmacological inhibitor, multiple orthogonal methods in single lab","pmids":["31783675"],"is_preprint":false},{"year":2020,"finding":"PDSS2-Del2 (exon 2 deletion splice variant), devoid of CoQ10 biosynthetic function, promotes HCC metastasis and angiogenesis by decreasing fumarate levels and activating the canonical NF-κB pathway, as well as EMT and WNT/β-catenin signaling; dimethyl fumarate supplementation rescues PDSS2-Del2-induced metastasis.","method":"In vitro migration assays; in vivo xenograft and spleen-liver metastasis models; fumarate metabolite measurement; NF-κB pathway reporter; dimethyl fumarate rescue experiment","journal":"Molecular oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo functional assays with metabolic and pathway readouts, pharmacological rescue, single lab","pmids":["33064899"],"is_preprint":false},{"year":2021,"finding":"PDSS2 interacts with Nrf2 and activates the Nrf2 antioxidant pathway to suppress ROS, iron accumulation, and ferroptosis in vascular endothelial cells; knockdown of Nrf2 abrogates the anti-ferroptotic effect of PDSS2 overexpression.","method":"Chromatin immunoprecipitation assay; luciferase assay; overexpression and knockdown in HCAECs; ROS measurement; iron content assay; in vivo atherosclerosis model","journal":"Journal of cardiovascular pharmacology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — ChIP and luciferase assays for interaction, epistasis via Nrf2 knockdown rescue, single lab","pmids":["33929387"],"is_preprint":false},{"year":2023,"finding":"SKA2 represses PDSS2 promoter activity through Sp1-binding sites; SKA2 physically associates with Sp1 (Co-IP); PDSS2 mutants lacking catalytic activity retain tumor-suppressive function in lung cancer cells, indicating a non-enzymatic mechanism of PDSS2 tumor suppression independent of CoQ10 synthesis.","method":"Co-immunoprecipitation; luciferase reporter assay; PDSS2 catalytic mutant overexpression; cell growth and motility assays; SKA2 knockdown with gene expression profiling","journal":"Journal of Cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for SKA2-Sp1 interaction, reporter assay for mechanism, catalytic mutant for non-enzymatic function, multiple methods single lab","pmids":["36860919"],"is_preprint":false},{"year":2024,"finding":"PDSS2-Del2 overexpression in HCC cells promotes ubiquitination and degradation of SKOR1, increasing SMAD3 phosphorylation and upregulating MST1 secretion, which recruits macrophages and polarizes them to M2 type; co-culture activates PI3K/AKT in macrophages, increasing MMP2 and MMP9 secretion to facilitate HCC cell dissemination.","method":"Co-culture assay; overexpression in HCC cells; ubiquitination assay; SMAD3 phosphorylation western blot; MST1 ELISA; macrophage polarization assay; PI3K/AKT pathway analysis; in vivo xenograft","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal biochemical and in vivo methods, single lab, mechanistic pathway dissected","pmids":["39695147"],"is_preprint":false},{"year":2014,"finding":"A C-to-G transversion upstream of PDSS2 in chickens significantly decreases PDSS2 promoter activity in vitro and reduces PDSS2 expression during feather development in vivo, causing the silky-feather (hookless) phenotype, demonstrating that PDSS2 cis-regulatory variation can alter its transcriptional output.","method":"Linkage and IBD fine-mapping; promoter activity assay (luciferase); in vivo expression analysis during feather development","journal":"PLoS genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reporter assay plus in vivo expression, genetic mapping, single study; ortholog (chicken) with consistent gene function","pmids":["25166907"],"is_preprint":false}],"current_model":"PDSS2 encodes a catalytic subunit of decaprenyl diphosphate synthase, the first enzyme of the CoQ10 biosynthetic pathway; loss of PDSS2 function reduces CoQ9/CoQ10 levels, impairing mitochondrial respiratory chain complex I activity and causing organ-specific oxidative stress and mitochondrial loss, while its transcription is repressed by an SKA2–Sp1 complex binding the PDSS2 promoter; beyond its enzymatic role, PDSS2 has a non-enzymatic tumor-suppressive function in cancer cells, and a splice variant (PDSS2-Del2) lacking CoQ10 biosynthetic activity instead promotes metastasis via fumarate depletion, NF-κB activation, and macrophage polarization."},"narrative":{"mechanistic_narrative":"PDSS2 encodes a catalytic subunit of decaprenyl diphosphate synthase, the first committed enzyme of the CoQ10 biosynthetic pathway, and its loss-of-function reduces cellular coenzyme Q and impairs mitochondrial respiratory chain function [PMID:17186472, PMID:29967258]. Compound heterozygous PDSS2 mutations abolish decaprenyl diphosphate synthase activity in patient fibroblasts, establishing PDSS2 as a cause of human CoQ deficiency [PMID:17186472]. In mouse models, CoQ9 deficiency produces respiratory chain abnormalities with organ-selective consequences: kidney-specific oxidative stress drives mitochondrial DNA depletion, loss of mitochondrial mass, and renal failure, whereas neuronal Pdss2 loss impairs cerebellar development, causes progressive Purkinje and dopaminergic neuron loss, and produces ataxia and neuromuscular deficits [PMID:23150520, PMID:21871565, PMID:21983691]. Restoring full-length PDSS2 raises CoQ10 and complex I activity and shifts cells from aerobic glycolysis to mitochondrial respiration, and PDSS2 loss induces chromosomal instability and malignant transformation, defining a tumor-suppressive role in hepatocellular carcinoma [PMID:29967258]. PDSS2 tumor suppression is partly non-enzymatic: catalytic-dead PDSS2 mutants retain growth- and motility-suppressing activity in lung cancer cells [PMID:36860919]. PDSS2 transcription is repressed by Sp1 binding the proximal promoter and by an SKA2–Sp1 complex, and cis-regulatory variation alters its output [PMID:31783675, PMID:36860919, PMID:25166907]. PDSS2 also engages the Nrf2 antioxidant pathway to limit ROS, iron accumulation, and ferroptosis in vascular endothelial cells [PMID:33929387]. In contrast, the exon-2-deleted splice variant PDSS2-Del2, which lacks CoQ10 biosynthetic activity, promotes metastasis by depleting fumarate and activating NF-κB, and by driving SKOR1 degradation, SMAD3 phosphorylation, and MST1-dependent M2 macrophage polarization [PMID:33064899, PMID:39695147].","teleology":[{"year":2006,"claim":"Established that PDSS2 is a catalytic subunit of decaprenyl diphosphate synthase and that its mutation causes human CoQ10 deficiency, defining the gene's enzymatic identity and disease relevance.","evidence":"Radiolabeled-substrate enzymatic assays in patient fibroblasts plus genetic identification of compound heterozygous mutations","pmids":["17186472"],"confidence":"High","gaps":["Does not resolve the structure or stoichiometry of the synthase complex","Subunit partner(s) of PDSS2 in the synthase not defined in this finding"]},{"year":2011,"claim":"Connected PDSS2/CoQ deficiency to organ-specific pathology, showing tissue-restricted consequences in kidney podocytes and across distinct neuronal populations rather than a uniform respiratory collapse.","evidence":"Conditional knockout mouse models (podocyte, Pax2-cre cerebellar, Pcp2-cre Purkinje, dopaminergic) with histology, CoQ9 measurement, pharmacological probucol rescue, and behavioral assays","pmids":["21567994","21871565","21983691"],"confidence":"High","gaps":["Mechanism of organ selectivity of oxidative stress not fully defined","Dopaminergic phenotype from single lab with Medium confidence","Link between PPAR signaling normalization and CoQ restoration not mechanistically dissected"]},{"year":2012,"claim":"Showed that CoQ9 deficiency triggers a defined oxidative-stress cascade — ROS, mtDNA depletion, and loss of mitochondrial mass — specifically in affected kidney, explaining how respiratory chain defects translate into organ failure.","evidence":"CBA/Pdss2 kd/kd mice profiled at multiple disease stages with ROS, oxidative damage markers, mtDNA quantification, and citrate synthase assays","pmids":["23150520"],"confidence":"High","gaps":["Why kidney is selectively vulnerable to ROS unexplained","Causal ordering of mtDNA depletion versus mitochondrial loss not fully resolved"]},{"year":2018,"claim":"Demonstrated that PDSS2 acts as a tumor suppressor in HCC by restoring CoQ10, complex I activity, and mitochondrial respiration, and that only full-length PDSS2 (not loss-of-function isoforms) retains this activity.","evidence":"Gain- and loss-of-function in HCC cell lines with CoQ10 and complex I assays, metabolic flux, soft-agar and xenograft tumor assays, chromosomal instability assays, and isoform-specific rescue","pmids":["29967258"],"confidence":"High","gaps":["Whether tumor suppression is purely metabolic versus structural unresolved at this stage","Isoform comparison is Medium confidence from a single lab"]},{"year":2019,"claim":"Defined the transcriptional control of PDSS2, identifying Sp1 as a direct promoter-bound repressor and mapping the core promoter, providing a mechanism for PDSS2 silencing.","evidence":"Luciferase reporter assays, site-directed mutagenesis of Sp1 sites, ChIP, Sp1 overexpression, and mithramycin A inhibition","pmids":["31783675"],"confidence":"High","gaps":["Upstream signals controlling Sp1 occupancy at PDSS2 not identified","Co-repressors recruited with Sp1 not yet defined"]},{"year":2020,"claim":"Revealed a gain-of-function for the CoQ-incompetent splice variant PDSS2-Del2, showing it actively promotes metastasis through fumarate depletion and NF-κB activation rather than simply lacking enzymatic activity.","evidence":"In vitro migration assays, xenograft and spleen-liver metastasis models, fumarate metabolite measurement, NF-κB reporter, and dimethyl fumarate rescue","pmids":["33064899"],"confidence":"Medium","gaps":["Mechanism linking PDSS2-Del2 to fumarate metabolism not biochemically defined","Single-lab functional study"]},{"year":2021,"claim":"Extended PDSS2 function to vascular biology, showing it engages the Nrf2 antioxidant pathway to suppress ROS, iron accumulation, and ferroptosis.","evidence":"ChIP and luciferase assays for Nrf2 interaction, overexpression/knockdown in HCAECs, ROS and iron assays, Nrf2-knockdown epistasis, and in vivo atherosclerosis model","pmids":["33929387"],"confidence":"Medium","gaps":["Direct physical nature of the PDSS2–Nrf2 interaction not structurally confirmed","Single-lab study","Relationship to PDSS2 enzymatic activity in this context unclear"]},{"year":2023,"claim":"Separated PDSS2 tumor suppression from its enzymatic activity by showing catalytic-dead mutants retain growth/motility suppression, and identified SKA2 as a Sp1-associated repressor of PDSS2.","evidence":"Co-IP of SKA2 with Sp1, luciferase reporter assays, PDSS2 catalytic-mutant rescue, growth/motility assays, and SKA2-knockdown expression profiling in lung cancer cells","pmids":["36860919"],"confidence":"Medium","gaps":["Molecular basis of the non-enzymatic tumor-suppressive activity not identified","SKA2–Sp1 interaction rests on a single Co-IP","Effector proteins of catalytic-dead PDSS2 unknown"]},{"year":2024,"claim":"Dissected a tumor-microenvironment mechanism for PDSS2-Del2, showing it drives SKOR1 ubiquitination/degradation, SMAD3 phosphorylation, and MST1-mediated M2 macrophage polarization that promotes HCC dissemination.","evidence":"Co-culture, ubiquitination assays, SMAD3 phospho-western, MST1 ELISA, macrophage polarization and PI3K/AKT analysis, and xenografts","pmids":["39695147"],"confidence":"Medium","gaps":["Direct substrate-E3 relationship for SKOR1 degradation not defined","Single-lab study","How Del2 selectively activates this axis versus full-length PDSS2 unclear"]},{"year":null,"claim":"How a single locus reconciles an essential CoQ-biosynthetic enzyme, a non-enzymatic tumor suppressor, and an oncogenic metastasis-promoting splice variant — and what governs the splicing switch between these activities — remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of PDSS2 or its catalytic-independent activity","Regulation of PDSS2 vs PDSS2-Del2 splicing not defined","Physical partners mediating non-enzymatic functions not mapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0,5]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[7,10]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[1,5]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,5]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[1,9]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[5,8]}],"complexes":["decaprenyl diphosphate synthase"],"partners":["NRF2","SP1","SKA2"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q86YH6","full_name":"All trans-polyprenyl-diphosphate synthase PDSS2","aliases":["All-trans-decaprenyl-diphosphate synthase subunit 2","Candidate tumor suppressor protein","Decaprenyl pyrophosphate synthase subunit 2","Decaprenyl-diphosphate synthase subunit 2","Solanesyl-diphosphate synthase subunit 2"],"length_aa":399,"mass_kda":44.1,"function":"Heterotetrameric enzyme that catalyzes the condensation of farnesyl diphosphate (FPP), which acts as a primer, and isopentenyl diphosphate (IPP) to produce prenyl diphosphates of varying chain lengths and participates in the determination of the side chain of ubiquinone (PubMed:16262699). Supplies nona and decaprenyl diphosphate, the precursors for the side chain of the isoprenoid quinones ubiquinone-9 (Q9) and ubiquinone-10 (Q10) respectively (PubMed:16262699). The enzyme adds isopentenyl diphosphate molecules sequentially to farnesyl diphosphate with trans stereochemistry (PubMed:16262699). May play a role during cerebellar development (By similarity). May regulate mitochondrial respiratory chain function (By similarity)","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/Q86YH6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PDSS2","classification":"Not Classified","n_dependent_lines":125,"n_total_lines":1208,"dependency_fraction":0.10347682119205298},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PDSS2","total_profiled":1310},"omim":[{"mim_id":"614652","title":"COENZYME Q10 DEFICIENCY, PRIMARY, 3; COQ10D3","url":"https://www.omim.org/entry/614652"},{"mim_id":"610564","title":"PRENYL DIPHOSPHATE SYNTHASE, SUBUNIT 2; PDSS2","url":"https://www.omim.org/entry/610564"},{"mim_id":"607429","title":"PRENYL DIPHOSPHATE SYNTHASE, SUBUNIT 1; PDSS1","url":"https://www.omim.org/entry/607429"},{"mim_id":"607426","title":"COENZYME Q10 DEFICIENCY, PRIMARY, 1; COQ10D1","url":"https://www.omim.org/entry/607426"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PDSS2"},"hgnc":{"alias_symbol":["bA59I9.3","COQ1B"],"prev_symbol":["C6orf210"]},"alphafold":{"accession":"Q86YH6","domains":[{"cath_id":"1.10.600.10","chopping":"47-301_311-397","consensus_level":"medium","plddt":88.1473,"start":47,"end":397}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86YH6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q86YH6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q86YH6-F1-predicted_aligned_error_v6.png","plddt_mean":80.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PDSS2","jax_strain_url":"https://www.jax.org/strain/search?query=PDSS2"},"sequence":{"accession":"Q86YH6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q86YH6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q86YH6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q86YH6"}},"corpus_meta":[{"pmid":"17186472","id":"PMC_17186472","title":"Leigh syndrome with nephropathy and CoQ10 deficiency due to decaprenyl diphosphate synthase subunit 2 (PDSS2) mutations.","date":"2006","source":"American journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/17186472","citation_count":311,"is_preprint":false},{"pmid":"33929387","id":"PMC_33929387","title":"PDSS2 Inhibits the Ferroptosis of Vascular Endothelial Cells in Atherosclerosis by Activating Nrf2.","date":"2021","source":"Journal of cardiovascular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/33929387","citation_count":68,"is_preprint":false},{"pmid":"23150520","id":"PMC_23150520","title":"Tissue-specific oxidative stress and loss of mitochondria in CoQ-deficient Pdss2 mutant mice.","date":"2012","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/23150520","citation_count":55,"is_preprint":false},{"pmid":"21567994","id":"PMC_21567994","title":"Probucol ameliorates renal and metabolic sequelae of primary CoQ deficiency in Pdss2 mutant mice.","date":"2011","source":"EMBO molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/21567994","citation_count":44,"is_preprint":false},{"pmid":"23926186","id":"PMC_23926186","title":"Focal segmental glomerulosclerosis is associated with a PDSS2 haplotype and, independently, with a decreased content of coenzyme Q10.","date":"2013","source":"American journal of physiology. Renal physiology","url":"https://pubmed.ncbi.nlm.nih.gov/23926186","citation_count":39,"is_preprint":false},{"pmid":"29967258","id":"PMC_29967258","title":"PDSS2 Deficiency Induces Hepatocarcinogenesis by Decreasing Mitochondrial Respiration and Reprogramming Glucose Metabolism.","date":"2018","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/29967258","citation_count":36,"is_preprint":false},{"pmid":"21871565","id":"PMC_21871565","title":"Cerebellar defects in Pdss2 conditional knockout mice during embryonic development and in adulthood.","date":"2011","source":"Neurobiology of disease","url":"https://pubmed.ncbi.nlm.nih.gov/21871565","citation_count":31,"is_preprint":false},{"pmid":"25166907","id":"PMC_25166907","title":"A cis-regulatory mutation of PDSS2 causes silky-feather in chickens.","date":"2014","source":"PLoS genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25166907","citation_count":27,"is_preprint":false},{"pmid":"31783675","id":"PMC_31783675","title":"Sp1 Mediates the Constitutive Expression and Repression of the PDSS2 Gene in Lung Cancer Cells.","date":"2019","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/31783675","citation_count":24,"is_preprint":false},{"pmid":"33064899","id":"PMC_33064899","title":"PDSS2-Del2, a new variant of PDSS2, promotes tumor cell metastasis and angiogenesis in hepatocellular carcinoma via activating NF-κB.","date":"2020","source":"Molecular oncology","url":"https://pubmed.ncbi.nlm.nih.gov/33064899","citation_count":19,"is_preprint":false},{"pmid":"29032433","id":"PMC_29032433","title":"Diffuse mesangial sclerosis in a PDSS2 mutation-induced coenzyme Q10 deficiency.","date":"2017","source":"Pediatric nephrology (Berlin, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/29032433","citation_count":19,"is_preprint":false},{"pmid":"25189544","id":"PMC_25189544","title":"Clinical utility of PDSS2 expression to stratify patients at risk for recurrence of hepatocellular carcinoma.","date":"2014","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/25189544","citation_count":17,"is_preprint":false},{"pmid":"21983691","id":"PMC_21983691","title":"Parkinson's disease-like neuromuscular defects occur in prenyl diphosphate synthase subunit 2 (Pdss2) mutant mice.","date":"2011","source":"Mitochondrion","url":"https://pubmed.ncbi.nlm.nih.gov/21983691","citation_count":14,"is_preprint":false},{"pmid":"19209031","id":"PMC_19209031","title":"Anticancer activity of PDSS2, prenyl diphosphate synthase, subunit 2, in gastric cancer tissue and the SGC7901 cell line.","date":"2009","source":"Anti-cancer drugs","url":"https://pubmed.ncbi.nlm.nih.gov/19209031","citation_count":8,"is_preprint":false},{"pmid":"23312889","id":"PMC_23312889","title":"Decrease of PDSS2 expression, a novel tumor suppressor, in non-small cell lung cancer.","date":"2013","source":"Cancer epidemiology","url":"https://pubmed.ncbi.nlm.nih.gov/23312889","citation_count":7,"is_preprint":false},{"pmid":"39695147","id":"PMC_39695147","title":"Overexpression of PDSS2-Del2 in HCC promotes tumor metastasis by interacting with macrophages.","date":"2024","source":"Cell death discovery","url":"https://pubmed.ncbi.nlm.nih.gov/39695147","citation_count":2,"is_preprint":false},{"pmid":"36860919","id":"PMC_36860919","title":"SKA2-mediated transcriptional downregulation of the key enzyme of CoQ10 biosynthesis PDSS2 in lung cancer cells.","date":"2023","source":"Journal of Cancer","url":"https://pubmed.ncbi.nlm.nih.gov/36860919","citation_count":2,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":10844,"output_tokens":3323,"usd":0.041189,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":10980,"output_tokens":3802,"usd":0.074975,"stage2_stop_reason":"end_turn"},"total_usd":0.116164,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2006,\n      \"finding\": \"PDSS2 encodes a subunit of decaprenyl diphosphate synthase, the first enzyme of the CoQ10 biosynthetic pathway; compound heterozygous mutations in PDSS2 cause a severe defect in decaprenyl diphosphate synthase activity as demonstrated by biochemical assays with radiolabeled substrates in patient fibroblasts.\",\n      \"method\": \"Biochemical assays with radiolabeled substrates in patient-derived fibroblasts; genetic identification of compound heterozygous mutations\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct enzymatic activity assay with radiolabeled substrates in patient cells, replicated in disease context; foundational mechanistic paper\",\n      \"pmids\": [\"17186472\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In Pdss2 mutant mice, widespread CoQ9 deficiency causes mitochondrial respiratory chain abnormalities; only affected organs (kidney) show increased ROS production, oxidative stress, mitochondrial DNA depletion, and reduced mitochondrial mass (citrate synthase activity), indicating that kidney-specific oxidative stress triggers mitochondrial loss and renal failure.\",\n      \"method\": \"In vivo mouse model (CBA/Pdss2 kd/kd) at multiple disease stages; ROS measurement, oxidative damage markers, mitochondrial DNA quantification, citrate synthase activity assay\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vivo methods (ROS, oxidative damage, mtDNA, citrate synthase) at multiple disease stages in a defined genetic model\",\n      \"pmids\": [\"23150520\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Pdss2 deficiency in glomerular podocytes (conditional knockout) causes focal segmental glomerulosclerosis-like kidney disease; probucol treatment restores CoQ9 content in mutant kidney and ameliorates nephropathy, while also normalizing PPAR pathway signaling, indicating that decreased CoQ9 and altered PPAR signaling respectively orchestrate glomerular and metabolic consequences.\",\n      \"method\": \"Pdss2 conditional knockout mouse model; oral probucol treatment; CoQ9 measurement; transcriptional profiling; albuminuria assay\",\n      \"journal\": \"EMBO molecular medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional genetic model with pharmacological rescue, multiple endpoints (CoQ9 restoration, transcriptomics, albuminuria), multiple orthogonal methods\",\n      \"pmids\": [\"21567994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Pdss2 knockout during cerebellar development (via Pax2-cre) delays radial glial cell growth and neuronal progenitor migration, increases ectopic apoptosis of neuroblasts, impairs cell proliferation, and causes mitochondrial defects with autophagic vacuolization, leading to cerebellar hypoplasia; Pdss2 knockout in Purkinje cells (Pcp2-cre) causes progressive Purkinje cell loss and ataxia in adulthood.\",\n      \"method\": \"Conditional knockout mouse lines (Pax2-cre and Pcp2-cre); histology, immunohistochemistry, electron microscopy, behavioral assays\",\n      \"journal\": \"Neurobiology of disease\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent conditional knockout mouse models with complementary developmental and adult phenotypes, multiple orthogonal methods including electron microscopy\",\n      \"pmids\": [\"21871565\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Conditional Pdss2 knockout targeted to dopaminergic neurons causes deficiencies in tyrosine hydroxylase-positive neurons in the substantia nigra and neuromuscular deficits, implicating CoQ deficiency in dopaminergic neuron loss similar to Parkinson's disease pathology.\",\n      \"method\": \"Conditional Pdss2 knockout (dopaminergic neuron-specific); behavioral/coordination assays; tyrosine hydroxylase immunostaining\",\n      \"journal\": \"Mitochondrion\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — conditional genetic model with neurochemical and behavioral readouts, single lab, two orthogonal methods\",\n      \"pmids\": [\"21983691\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Reintroduction of full-length PDSS2 into HCC cells increases CoQ10 levels and mitochondrial electron transport complex I activity, inducing a metabolic shift from aerobic glycolysis to mitochondrial respiration; PDSS2 knockdown induces chromosomal instability and malignant transformation in immortalized liver cells.\",\n      \"method\": \"Overexpression and knockdown in HCC cell lines; CoQ10 measurement; complex I activity assay; soft agar colony formation; nude mouse xenograft; chromosomal instability assay\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (CoQ10, complex I activity, metabolic flux, in vivo xenograft, chromosomal instability), gain- and loss-of-function in same study\",\n      \"pmids\": [\"29967258\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Five of six alternative splicing isoforms of PDSS2 (lacking exon 2 or other domains) show loss of function in HCC, while only full-length PDSS2 restores CoQ10 biosynthesis and tumor suppressive activity.\",\n      \"method\": \"Isoform-specific overexpression in HCC cells; CoQ10 measurement; functional assays (colony formation, tumor formation)\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct functional comparison of isoforms, single lab, multiple functional readouts\",\n      \"pmids\": [\"29967258\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Sp1 transcription factor binds to the PDSS2 promoter in vivo and represses PDSS2 transcription; site-directed mutagenesis of Sp1 binding sites abolishes proximal promoter activity; the core PDSS2 promoter is located within 202 bp of the transcription initiation site.\",\n      \"method\": \"Luciferase reporter assay; site-directed mutagenesis; ChIP assay; Sp1 overexpression; mithramycin A (Sp1 inhibitor) treatment\",\n      \"journal\": \"Genes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — ChIP, reporter assay, mutagenesis, pharmacological inhibitor, multiple orthogonal methods in single lab\",\n      \"pmids\": [\"31783675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PDSS2-Del2 (exon 2 deletion splice variant), devoid of CoQ10 biosynthetic function, promotes HCC metastasis and angiogenesis by decreasing fumarate levels and activating the canonical NF-κB pathway, as well as EMT and WNT/β-catenin signaling; dimethyl fumarate supplementation rescues PDSS2-Del2-induced metastasis.\",\n      \"method\": \"In vitro migration assays; in vivo xenograft and spleen-liver metastasis models; fumarate metabolite measurement; NF-κB pathway reporter; dimethyl fumarate rescue experiment\",\n      \"journal\": \"Molecular oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo functional assays with metabolic and pathway readouts, pharmacological rescue, single lab\",\n      \"pmids\": [\"33064899\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PDSS2 interacts with Nrf2 and activates the Nrf2 antioxidant pathway to suppress ROS, iron accumulation, and ferroptosis in vascular endothelial cells; knockdown of Nrf2 abrogates the anti-ferroptotic effect of PDSS2 overexpression.\",\n      \"method\": \"Chromatin immunoprecipitation assay; luciferase assay; overexpression and knockdown in HCAECs; ROS measurement; iron content assay; in vivo atherosclerosis model\",\n      \"journal\": \"Journal of cardiovascular pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — ChIP and luciferase assays for interaction, epistasis via Nrf2 knockdown rescue, single lab\",\n      \"pmids\": [\"33929387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SKA2 represses PDSS2 promoter activity through Sp1-binding sites; SKA2 physically associates with Sp1 (Co-IP); PDSS2 mutants lacking catalytic activity retain tumor-suppressive function in lung cancer cells, indicating a non-enzymatic mechanism of PDSS2 tumor suppression independent of CoQ10 synthesis.\",\n      \"method\": \"Co-immunoprecipitation; luciferase reporter assay; PDSS2 catalytic mutant overexpression; cell growth and motility assays; SKA2 knockdown with gene expression profiling\",\n      \"journal\": \"Journal of Cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for SKA2-Sp1 interaction, reporter assay for mechanism, catalytic mutant for non-enzymatic function, multiple methods single lab\",\n      \"pmids\": [\"36860919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PDSS2-Del2 overexpression in HCC cells promotes ubiquitination and degradation of SKOR1, increasing SMAD3 phosphorylation and upregulating MST1 secretion, which recruits macrophages and polarizes them to M2 type; co-culture activates PI3K/AKT in macrophages, increasing MMP2 and MMP9 secretion to facilitate HCC cell dissemination.\",\n      \"method\": \"Co-culture assay; overexpression in HCC cells; ubiquitination assay; SMAD3 phosphorylation western blot; MST1 ELISA; macrophage polarization assay; PI3K/AKT pathway analysis; in vivo xenograft\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal biochemical and in vivo methods, single lab, mechanistic pathway dissected\",\n      \"pmids\": [\"39695147\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"A C-to-G transversion upstream of PDSS2 in chickens significantly decreases PDSS2 promoter activity in vitro and reduces PDSS2 expression during feather development in vivo, causing the silky-feather (hookless) phenotype, demonstrating that PDSS2 cis-regulatory variation can alter its transcriptional output.\",\n      \"method\": \"Linkage and IBD fine-mapping; promoter activity assay (luciferase); in vivo expression analysis during feather development\",\n      \"journal\": \"PLoS genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reporter assay plus in vivo expression, genetic mapping, single study; ortholog (chicken) with consistent gene function\",\n      \"pmids\": [\"25166907\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PDSS2 encodes a catalytic subunit of decaprenyl diphosphate synthase, the first enzyme of the CoQ10 biosynthetic pathway; loss of PDSS2 function reduces CoQ9/CoQ10 levels, impairing mitochondrial respiratory chain complex I activity and causing organ-specific oxidative stress and mitochondrial loss, while its transcription is repressed by an SKA2–Sp1 complex binding the PDSS2 promoter; beyond its enzymatic role, PDSS2 has a non-enzymatic tumor-suppressive function in cancer cells, and a splice variant (PDSS2-Del2) lacking CoQ10 biosynthetic activity instead promotes metastasis via fumarate depletion, NF-κB activation, and macrophage polarization.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PDSS2 encodes a catalytic subunit of decaprenyl diphosphate synthase, the first committed enzyme of the CoQ10 biosynthetic pathway, and its loss-of-function reduces cellular coenzyme Q and impairs mitochondrial respiratory chain function [#0, #5]. Compound heterozygous PDSS2 mutations abolish decaprenyl diphosphate synthase activity in patient fibroblasts, establishing PDSS2 as a cause of human CoQ deficiency [#0]. In mouse models, CoQ9 deficiency produces respiratory chain abnormalities with organ-selective consequences: kidney-specific oxidative stress drives mitochondrial DNA depletion, loss of mitochondrial mass, and renal failure, whereas neuronal Pdss2 loss impairs cerebellar development, causes progressive Purkinje and dopaminergic neuron loss, and produces ataxia and neuromuscular deficits [#1, #3, #4]. Restoring full-length PDSS2 raises CoQ10 and complex I activity and shifts cells from aerobic glycolysis to mitochondrial respiration, and PDSS2 loss induces chromosomal instability and malignant transformation, defining a tumor-suppressive role in hepatocellular carcinoma [#5]. PDSS2 tumor suppression is partly non-enzymatic: catalytic-dead PDSS2 mutants retain growth- and motility-suppressing activity in lung cancer cells [#10]. PDSS2 transcription is repressed by Sp1 binding the proximal promoter and by an SKA2–Sp1 complex, and cis-regulatory variation alters its output [#7, #10, #12]. PDSS2 also engages the Nrf2 antioxidant pathway to limit ROS, iron accumulation, and ferroptosis in vascular endothelial cells [#9]. In contrast, the exon-2-deleted splice variant PDSS2-Del2, which lacks CoQ10 biosynthetic activity, promotes metastasis by depleting fumarate and activating NF-κB, and by driving SKOR1 degradation, SMAD3 phosphorylation, and MST1-dependent M2 macrophage polarization [#8, #11].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Established that PDSS2 is a catalytic subunit of decaprenyl diphosphate synthase and that its mutation causes human CoQ10 deficiency, defining the gene's enzymatic identity and disease relevance.\",\n      \"evidence\": \"Radiolabeled-substrate enzymatic assays in patient fibroblasts plus genetic identification of compound heterozygous mutations\",\n      \"pmids\": [\"17186472\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not resolve the structure or stoichiometry of the synthase complex\", \"Subunit partner(s) of PDSS2 in the synthase not defined in this finding\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Connected PDSS2/CoQ deficiency to organ-specific pathology, showing tissue-restricted consequences in kidney podocytes and across distinct neuronal populations rather than a uniform respiratory collapse.\",\n      \"evidence\": \"Conditional knockout mouse models (podocyte, Pax2-cre cerebellar, Pcp2-cre Purkinje, dopaminergic) with histology, CoQ9 measurement, pharmacological probucol rescue, and behavioral assays\",\n      \"pmids\": [\"21567994\", \"21871565\", \"21983691\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of organ selectivity of oxidative stress not fully defined\", \"Dopaminergic phenotype from single lab with Medium confidence\", \"Link between PPAR signaling normalization and CoQ restoration not mechanistically dissected\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showed that CoQ9 deficiency triggers a defined oxidative-stress cascade — ROS, mtDNA depletion, and loss of mitochondrial mass — specifically in affected kidney, explaining how respiratory chain defects translate into organ failure.\",\n      \"evidence\": \"CBA/Pdss2 kd/kd mice profiled at multiple disease stages with ROS, oxidative damage markers, mtDNA quantification, and citrate synthase assays\",\n      \"pmids\": [\"23150520\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why kidney is selectively vulnerable to ROS unexplained\", \"Causal ordering of mtDNA depletion versus mitochondrial loss not fully resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated that PDSS2 acts as a tumor suppressor in HCC by restoring CoQ10, complex I activity, and mitochondrial respiration, and that only full-length PDSS2 (not loss-of-function isoforms) retains this activity.\",\n      \"evidence\": \"Gain- and loss-of-function in HCC cell lines with CoQ10 and complex I assays, metabolic flux, soft-agar and xenograft tumor assays, chromosomal instability assays, and isoform-specific rescue\",\n      \"pmids\": [\"29967258\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether tumor suppression is purely metabolic versus structural unresolved at this stage\", \"Isoform comparison is Medium confidence from a single lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined the transcriptional control of PDSS2, identifying Sp1 as a direct promoter-bound repressor and mapping the core promoter, providing a mechanism for PDSS2 silencing.\",\n      \"evidence\": \"Luciferase reporter assays, site-directed mutagenesis of Sp1 sites, ChIP, Sp1 overexpression, and mithramycin A inhibition\",\n      \"pmids\": [\"31783675\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Upstream signals controlling Sp1 occupancy at PDSS2 not identified\", \"Co-repressors recruited with Sp1 not yet defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Revealed a gain-of-function for the CoQ-incompetent splice variant PDSS2-Del2, showing it actively promotes metastasis through fumarate depletion and NF-κB activation rather than simply lacking enzymatic activity.\",\n      \"evidence\": \"In vitro migration assays, xenograft and spleen-liver metastasis models, fumarate metabolite measurement, NF-κB reporter, and dimethyl fumarate rescue\",\n      \"pmids\": [\"33064899\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism linking PDSS2-Del2 to fumarate metabolism not biochemically defined\", \"Single-lab functional study\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Extended PDSS2 function to vascular biology, showing it engages the Nrf2 antioxidant pathway to suppress ROS, iron accumulation, and ferroptosis.\",\n      \"evidence\": \"ChIP and luciferase assays for Nrf2 interaction, overexpression/knockdown in HCAECs, ROS and iron assays, Nrf2-knockdown epistasis, and in vivo atherosclerosis model\",\n      \"pmids\": [\"33929387\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical nature of the PDSS2–Nrf2 interaction not structurally confirmed\", \"Single-lab study\", \"Relationship to PDSS2 enzymatic activity in this context unclear\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Separated PDSS2 tumor suppression from its enzymatic activity by showing catalytic-dead mutants retain growth/motility suppression, and identified SKA2 as a Sp1-associated repressor of PDSS2.\",\n      \"evidence\": \"Co-IP of SKA2 with Sp1, luciferase reporter assays, PDSS2 catalytic-mutant rescue, growth/motility assays, and SKA2-knockdown expression profiling in lung cancer cells\",\n      \"pmids\": [\"36860919\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of the non-enzymatic tumor-suppressive activity not identified\", \"SKA2–Sp1 interaction rests on a single Co-IP\", \"Effector proteins of catalytic-dead PDSS2 unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Dissected a tumor-microenvironment mechanism for PDSS2-Del2, showing it drives SKOR1 ubiquitination/degradation, SMAD3 phosphorylation, and MST1-mediated M2 macrophage polarization that promotes HCC dissemination.\",\n      \"evidence\": \"Co-culture, ubiquitination assays, SMAD3 phospho-western, MST1 ELISA, macrophage polarization and PI3K/AKT analysis, and xenografts\",\n      \"pmids\": [\"39695147\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct substrate-E3 relationship for SKOR1 degradation not defined\", \"Single-lab study\", \"How Del2 selectively activates this axis versus full-length PDSS2 unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single locus reconciles an essential CoQ-biosynthetic enzyme, a non-enzymatic tumor suppressor, and an oncogenic metastasis-promoting splice variant — and what governs the splicing switch between these activities — remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of PDSS2 or its catalytic-independent activity\", \"Regulation of PDSS2 vs PDSS2-Del2 splicing not defined\", \"Physical partners mediating non-enzymatic functions not mapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [7, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [1, 5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [1, 9]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [5, 8]}\n    ],\n    \"complexes\": [\"decaprenyl diphosphate synthase\"],\n    \"partners\": [\"Nrf2\", \"Sp1\", \"SKA2\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}