{"gene":"PTPMT1","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2011,"finding":"PTPMT1 specifically dephosphorylates phosphatidylglycerophosphate (PGP) in vitro, acting as the mammalian PGP phosphatase required for cardiolipin biosynthesis; loss of PTPMT1 leads to PGP accumulation and dramatic reduction of cardiolipin, rescued by catalytically active but not catalytically dead PTPMT1.","method":"In vitro phosphatase assay, lipid analysis of Ptpmt1-deficient mouse embryonic fibroblasts, catalytic-dead rescue experiment","journal":"Cell Metabolism","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro enzymatic reconstitution with substrate, genetic KO with lipid mass spectrometry, and catalytic-mutant rescue all in one study; independently supported by multiple subsequent papers","pmids":["21641550"],"is_preprint":false},{"year":2011,"finding":"Crystal structures of the PTPMT1 phosphatase domain reveal a canonical dual-specificity PTP fold; the substrate-bound structure (with phosphatidylinositol 5-phosphate) defines the active site architecture and shows significant conformational change during catalysis; a conserved EEYE loop was experimentally shown to be important for catalytic activity.","method":"X-ray crystallography (apo and substrate-bound), EEYE loop mutagenesis with activity assay","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures with functional mutagenesis validation in one rigorous study","pmids":["21730175"],"is_preprint":false},{"year":2011,"finding":"PTPMT1 localizes exclusively to mitochondria; its mitochondrial localization is required for function, as truncated PTPMT1 lacking the mitochondrial localization signal fails to rescue differentiation defects in Ptpmt1-knockout embryonic stem cells.","method":"Conditional knockout ES cells, rescue with wild-type vs. MLS-truncated PTPMT1 constructs, differentiation assays","journal":"Molecular and Cellular Biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with defined cellular phenotype, MLS-deletion rescue experiment, replicated in HSC study (PMID:23290137)","pmids":["21986498","23290137"],"is_preprint":false},{"year":2011,"finding":"Loss of Ptpmt1 in embryonic fibroblasts causes decreased mitochondrial respiration, abnormal mitochondrial morphology, PGP accumulation, and reduced cardiolipin; whole-body Ptpmt1 deletion leads to embryonic lethality.","method":"Whole-body and conditional Ptpmt1 knockout mice, oxygen consumption measurements, electron microscopy, lipidomics","journal":"Cell Metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with multiple orthogonal phenotypic readouts (respiration, morphology, lipid mass spec) in one study","pmids":["21641550"],"is_preprint":false},{"year":2011,"finding":"Ptpmt1 depletion in embryonic stem cells blocks differentiation, increases cyclin-dependent kinase inhibitors, delays cell cycle, decreases oxygen consumption, and enhances glycolysis; accumulated phosphatidylinositol phosphates (PIPs) compromise mitochondrial fusion/dynamics.","method":"Conditional Ptpmt1 KO ES cells, cell cycle analysis, oxygen consumption and glycolysis assays, mitochondrial morphology imaging","journal":"Molecular and Cellular Biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional KO with multiple orthogonal mechanistic readouts in one rigorous study","pmids":["21986498"],"is_preprint":false},{"year":2013,"finding":"PTPMT1 deficiency alters mitochondrial metabolism and its phosphatidylinositol phosphate substrates directly enhance fatty-acid-induced activation of mitochondrial uncoupling protein 2 (UCP2); catalytically deficient or MLS-lacking PTPMT1 fails to restore HSC differentiation, establishing catalytic activity and mitochondrial localization as essential.","method":"Inducible and hematopoietic-specific Ptpmt1 KO mice, rescue with WT vs. catalytic-dead vs. MLS-truncated PTPMT1, UCP2 activation assays","journal":"Cell Stem Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with rescue experiments and direct substrate-UCP2 activation assay; multiple orthogonal methods","pmids":["23290137"],"is_preprint":false},{"year":2015,"finding":"PTPMT1 acts upstream of succinate dehydrogenase (SDH): pharmacological or genetic inactivation of PTPMT1 causes hyperphosphorylation and activation of SDH, providing a mechanism by which PTPMT1 regulates glucose homeostasis in zebrafish; ptpmt1 mutation eliminates the glucose-lowering effect of alexidine, confirming SDH as the downstream effector.","method":"Chemical screen in zebrafish, ptpmt1 genetic mutants, SDH phosphorylation and activity assays, glucose measurements","journal":"Cell Reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic epistasis in zebrafish with biochemical SDH phosphorylation readout; single lab, in vivo model","pmids":["25660020"],"is_preprint":false},{"year":2010,"finding":"Alexidine dihydrochloride is a selective inhibitor of PTPMT1 (IC50 ~1.08 μM in vitro); treatment of pancreatic islets increases insulin secretion, and knockdown of PTPMT1 renders islets insensitive to alexidine, confirming mechanism-based activity; PTPMT1 inhibition affects phosphorylation of mitochondrial proteins in beta cells.","method":"In vitro phosphatase inhibition assay, rat pancreatic islet insulin secretion assay, PTPMT1 knockdown in islets","journal":"The Journal of Pharmacology and Experimental Therapeutics","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — in vitro IC50 determination combined with genetic knockdown rescue in primary tissue confirming on-target activity","pmids":["20167843"],"is_preprint":false},{"year":2014,"finding":"The pseudophosphatase MK-STYX physically interacts with PTPMT1 and suppresses its catalytic activity; knockdown of PTPMT1 resensitizes MK-STYX-knockdown cells to chemotherapeutics and restores cytochrome c release, placing MK-STYX as a negative regulator of PTPMT1 in apoptosis control.","method":"Unbiased proteomics (MS interactome), co-immunoprecipitation confirmation in cells, PTPMT1 activity assays, cytochrome c release assays, double-knockdown epistasis","journal":"PloS One","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-identified interaction confirmed by Co-IP, activity suppression assay, and epistasis; single lab","pmids":["24709986"],"is_preprint":false},{"year":2013,"finding":"Downregulation of PTPMT1 in cancer cells decreases cardiolipin levels, selectively increases ATP levels in glycolytic media, and induces apoptosis; sublethal PTPMT1 knockdown synergizes with paclitaxel, suggesting PTPMT1 loss causes a metabolic crisis.","method":"RNAi knockdown in cancer cell lines, cardiolipin quantification, ATP measurement, apoptosis assays, drug synergy assay","journal":"PloS One","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KD with defined metabolic and cell death phenotypes; single lab, multiple orthogonal methods","pmids":["23326511"],"is_preprint":false},{"year":2023,"finding":"PTPMT1 interacts with mitochondrial proteins SLC25A6 and NDUFS2 as identified by co-immunoprecipitation, suggesting PTPMT1 modulates mitochondrial function via the SLC25A6-NDUFS2 axis in pancreatic cancer cells.","method":"Co-immunoprecipitation, siRNA knockdown with viability and mitochondrial function assays","journal":"American Journal of Cancer Research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP identification without reciprocal validation or functional mutagenesis; single lab","pmids":["37034225"],"is_preprint":false},{"year":2023,"finding":"Cardiac-specific and skeletal-muscle-specific deletion of Ptpmt1 inhibits pyruvate (carbohydrate-derived substrate) utilization in mitochondria while enhancing fatty acid utilization, causing oxidative stress, mitochondrial destruction, lipid accumulation, muscle atrophy, heart failure, and sudden death; liver- or adipose-specific deletion has no such effect.","method":"Tissue-specific Ptpmt1 KO mice, substrate oxidation assays, metabolomics, histology, cardiac function measurements","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean tissue-specific KO with multiple orthogonal metabolic and functional readouts; tissue-specificity controls strengthen mechanistic interpretation","pmids":["37672386"],"is_preprint":false},{"year":2021,"finding":"Knockout of PTPMT1 in hepatocellular carcinoma cells stops cardiolipin maturation and impairs assembly of electron transport chain (ETC) complexes, leading to electron leakage and ROS accumulation under hypoxia; PTPMT1 was identified as the top hit after HIF-1α/β in a genome-wide CRISPR-Cas9 knockout screen for hypoxic survival.","method":"Genome-wide CRISPR-Cas9 KO screen, PTPMT1 KO in HCC cells, ETC complex assembly assays, ROS measurement, cardiolipin quantification","journal":"Cell Reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — unbiased genome-wide screen validated with targeted KO plus multiple biochemical assays (ETC assembly, ROS, cardiolipin); single lab but orthogonal methods","pmids":["33503428"],"is_preprint":false},{"year":2025,"finding":"Biallelic loss-of-function variants in PTPMT1 in humans cause an autosomal recessive primary mitochondrial disease with neurodevelopmental syndrome; patient-derived fibroblasts and muscle tissue show impaired cardiolipin biosynthesis, mitochondrial structural and functional defects; ptpmt1 knockout zebrafish show decreased total cardiolipin and OXPHOS deficiency, confirming the disease mechanism.","method":"Human genetics (biallelic variants in 6 patients), patient-derived fibroblast and muscle studies, cellular rescue experiments, ptpmt1 KO zebrafish with cardiolipin and OXPHOS measurements","journal":"Brain","confidence":"High","confidence_rationale":"Tier 2 / Strong — human disease genetics validated by patient cell biochemistry and animal KO model with multiple orthogonal functional assays","pmids":["39279645"],"is_preprint":false},{"year":2025,"finding":"Pharmacological inhibition of PTPMT1 by alexidine dihydrochloride increases susceptibility of hepatocellular carcinoma to ferroptosis by promoting conversion of ferritin-bound Fe3+ to free Fe2+, expanding the labile iron pool, inducing mitochondrial swelling and donut mitochondria formation, and enhancing succinate-to-fumarate metabolism in the TCA cycle.","method":"PTPMT1 KO and overexpression in HCC cell lines (CRISPR/Cas9 and lentiviral), alexidine treatment in vitro and in vivo, iron speciation assays, mitochondrial morphology imaging, TCA metabolomics","journal":"Cell Death & Disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO plus pharmacological inhibition with multiple biochemical readouts; single lab","pmids":["40189563"],"is_preprint":false},{"year":2018,"finding":"SRSF1 controls alternative splicing of PTPMT1; reduced SRSF1 favors production of short isoforms of PTPMT1 upon irradiation, which promotes AMPK phosphorylation and DNA double-strand breaks, sensitizing cancer cells to radiation.","method":"RNA-seq, RNA immunoprecipitation, minigene reporter assay, SRSF1 knockdown in lung cancer cell lines and xenografts","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CLIP confirmed SRSF1 binding, minigene validates splicing regulation, functional AMPK phosphorylation readout; single lab","pmids":["30429088"],"is_preprint":false},{"year":2021,"finding":"SRSF1 directly binds a motif in PTPMT1 exon 3 to regulate splice switching; the resulting PTPMT1 isoform change partially mediates SRSF1 oncogenic effects via the AKT/C-MYC axis in breast cancer cells.","method":"RIP-PCR, CLIP, minigene reporter assay, functional rescue in breast cancer cell lines and xenografts","journal":"Journal of Experimental & Clinical Cancer Research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding confirmed by CLIP, minigene validates splicing, downstream AKT/MYC pathway assays; single lab","pmids":["33992102"],"is_preprint":false},{"year":2025,"finding":"Depleting PTPMT1 (or CRLS1) rescues apoptosis caused by BLTP1 deficiency, placing PTPMT1-dependent cardiolipin synthesis upstream of apoptotic cell death triggered by mitochondrial phospholipid overload; this establishes PTPMT1 in the genetic epistasis pathway of mitochondrial phospholipid efflux.","method":"Genetic epistasis by siRNA co-depletion of BLTP1 and PTPMT1, apoptosis assays","journal":"bioRxiv (preprint)","confidence":"Low","confidence_rationale":"Tier 3 / Weak — epistasis by knockdown in single preprint, no reciprocal validation or in vitro reconstitution","pmids":["bio_10.1101_2025.09.30.679455"],"is_preprint":true},{"year":2025,"finding":"Cardiac-specific deletion of Ptpmt1 (αMHC-Cre) causes left ventricular non-compaction with reduced cardiomyocyte proliferation at E15.5 and increased phosphorylated eIF2α and ATF4, indicating a mitochondrial stress response links PTPMT1 to cardiac compaction and the integrated stress response pathway.","method":"Cardiac-specific KO mice, morphological/histological analysis, EdU proliferation assay, RNA-seq, western blot for p-eIF2α and ATF4","journal":"Journal of Developmental Biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean tissue-specific KO with multiple readouts including proliferation and stress response markers; single lab, new study","pmids":["40700143"],"is_preprint":false}],"current_model":"PTPMT1 is a dual-specificity phosphatase exclusively localized to the inner mitochondrial membrane that dephosphorylates phosphatidylglycerophosphate (PGP) to phosphatidylglycerol as the committed step in cardiolipin biosynthesis; loss of cardiolipin destabilizes electron transport chain complexes, impairs mitochondrial respiration and dynamics, causes metabolic inflexibility (blocked pyruvate/carbohydrate utilization with compensatory fatty acid oxidation), and triggers oxidative stress and cell death; PTPMT1 additionally dephosphorylates phosphatidylinositol phosphates that regulate UCP2 activity and mitochondrial fusion, acts upstream of succinate dehydrogenase phosphorylation to influence glucose homeostasis, and is negatively regulated by the pseudophosphatase MK-STYX; its catalytic activity and mitochondrial localization are both required for supporting stem cell differentiation, cardiac development, and organismal viability."},"narrative":{"mechanistic_narrative":"PTPMT1 is a mitochondria-resident dual-specificity phosphatase that catalyzes the committed step of cardiolipin biosynthesis by dephosphorylating phosphatidylglycerophosphate (PGP) to phosphatidylglycerol; loss of activity causes PGP accumulation and severe cardiolipin depletion, an effect rescued only by catalytically active enzyme [PMID:21641550]. Crystal structures define a canonical dual-specificity PTP fold with a conserved EEYE catalytic loop and a substrate-bound active site that undergoes conformational change during catalysis [PMID:21730175], and both enzymatic activity and an intact mitochondrial localization signal are strictly required for biological function [PMID:21986498, PMID:23290137]. Through cardiolipin production, PTPMT1 is essential for electron transport chain complex assembly, mitochondrial respiration, and normal mitochondrial morphology; its loss impairs oxygen consumption, drives compensatory glycolysis, and causes ROS accumulation and metabolic crisis [PMID:21641550, PMID:21986498, PMID:33503428]. Beyond cardiolipin, PTPMT1 turns over phosphatidylinositol phosphate substrates that potentiate fatty-acid activation of UCP2 and influence mitochondrial fusion [PMID:21986498, PMID:23290137], and acts upstream of succinate dehydrogenase phosphorylation to govern glucose homeostasis [PMID:25660020]. At the organismal level, PTPMT1 supports stem cell and hematopoietic differentiation, and tissue-specific deletion in heart and skeletal muscle blocks pyruvate utilization while forcing fatty acid oxidation, producing oxidative stress, muscle atrophy, heart failure, and sudden death [PMID:23290137, PMID:37672386]. Biallelic loss-of-function variants in PTPMT1 cause an autosomal recessive primary mitochondrial disease with neurodevelopmental syndrome, with patient tissue showing impaired cardiolipin synthesis and mitochondrial dysfunction [PMID:39279645]. The pseudophosphatase MK-STYX binds PTPMT1 and suppresses its activity, linking it to apoptotic control [PMID:24709986], and the selective inhibitor alexidine dihydrochloride engages PTPMT1 on-target [PMID:20167843].","teleology":[{"year":2010,"claim":"Establishing a chemical probe was the first step toward defining PTPMT1 function; identification of a selective small-molecule inhibitor enabled mechanism-based interrogation in primary tissue.","evidence":"In vitro phosphatase inhibition (IC50) plus PTPMT1 knockdown abolishing drug response in rat pancreatic islets","pmids":["20167843"],"confidence":"High","gaps":["Did not define the physiological substrate","Mechanism linking PTPMT1 to insulin secretion left at protein-phosphorylation correlation"]},{"year":2011,"claim":"The central question of what PTPMT1 actually dephosphorylates was answered by identifying PGP as its substrate, defining PTPMT1 as the mammalian PGP phosphatase that commits lipid flux to cardiolipin.","evidence":"In vitro phosphatase assay with PGP, lipidomics of KO MEFs, and catalytic-dead rescue","pmids":["21641550"],"confidence":"High","gaps":["Relative contribution of PIP versus PGP substrates not resolved","Whether PGP turnover alone accounts for all phenotypes unclear"]},{"year":2011,"claim":"Structural resolution of the phosphatase domain established the catalytic architecture, confirming a dual-specificity PTP fold and the functional EEYE loop.","evidence":"Apo and substrate-bound X-ray crystallography with EEYE loop mutagenesis and activity assays","pmids":["21730175"],"confidence":"High","gaps":["Structure solved with PI5P, not the native PGP substrate","No structure of full-length membrane-embedded enzyme"]},{"year":2011,"claim":"Genetic ablation established the physiological necessity of PTPMT1, showing that loss impairs respiration and mitochondrial morphology and is embryonic-lethal, and that mitochondrial localization is required for differentiation.","evidence":"Whole-body and conditional KO mice and ES cells with respirometry, EM, lipidomics, and MLS-truncation rescue","pmids":["21641550","21986498"],"confidence":"High","gaps":["Did not separate cardiolipin-dependent from PIP-dependent effects","Mechanism of differentiation block not fully resolved"]},{"year":2013,"claim":"PTPMT1 was connected to a second class of substrates and to apoptotic/metabolic control: its PIP products enhance UCP2 activation, and its loss triggers metabolic crisis and apoptosis in cancer cells.","evidence":"Hematopoietic-specific KO mice with catalytic and MLS rescue plus UCP2 assays; RNAi in cancer cells with cardiolipin, ATP, and apoptosis readouts","pmids":["23290137","23326511"],"confidence":"High","gaps":["Direct enzymatic link between specific PIP species and UCP2 not structurally defined","Cancer-cell apoptosis mechanism partly correlative"]},{"year":2014,"claim":"The first negative regulator of PTPMT1 was identified, showing that pseudophosphatase MK-STYX binds and suppresses its catalytic activity to modulate apoptosis.","evidence":"MS interactome, Co-IP, activity suppression assays, and double-knockdown epistasis on cytochrome c release","pmids":["24709986"],"confidence":"Medium","gaps":["Single lab without reciprocal in vivo validation","Structural basis of the inhibitory interaction unknown"]},{"year":2015,"claim":"A downstream effector branch was defined by genetic epistasis, placing PTPMT1 upstream of SDH phosphorylation in control of glucose homeostasis.","evidence":"Zebrafish chemical screen and ptpmt1 mutants with SDH phosphorylation/activity and glucose assays","pmids":["25660020"],"confidence":"Medium","gaps":["Direct enzymatic mechanism linking PTPMT1 to SDH phosphorylation not shown","Single in vivo model"]},{"year":2018,"claim":"PTPMT1 expression was shown to be controlled at the splicing level, with SRSF1 directing isoform switching that affects AMPK signaling and radiation sensitivity.","evidence":"RNA-seq, RIP/CLIP, minigene reporters, SRSF1 knockdown in lung cancer cells and xenografts","pmids":["30429088"],"confidence":"Medium","gaps":["Functional difference between short and full isoforms at the enzyme level not characterized","Single lab"]},{"year":2021,"claim":"The SRSF1–PTPMT1 splicing axis was mapped to a specific exon 3 binding motif and linked to AKT/C-MYC-driven oncogenesis, while a CRISPR screen established PTPMT1 as critical for hypoxic survival via cardiolipin-dependent ETC assembly.","evidence":"RIP-PCR/CLIP and minigene reporters in breast cancer; genome-wide CRISPR-Cas9 screen with KO, ETC assembly, ROS, and cardiolipin assays in HCC cells","pmids":["33992102","33503428"],"confidence":"High","gaps":["Causal contribution of isoform switch to tumor phenotype only partial","ETC complex assembly defects shown biochemically but not at single-complex structural resolution"]},{"year":2023,"claim":"Tissue-specific genetics revealed metabolic selectivity, showing PTPMT1 is required for pyruvate utilization in heart and skeletal muscle but dispensable in liver and adipose, with loss forcing fatty acid oxidation and causing lethal organ failure.","evidence":"Tissue-specific KO mice with substrate oxidation, metabolomics, histology, and cardiac function assays; Co-IP linking PTPMT1 to SLC25A6/NDUFS2","pmids":["37672386","37034225"],"confidence":"High","gaps":["Molecular basis of tissue selectivity unresolved","SLC25A6/NDUFS2 interactions are single Co-IP without reciprocal or mutagenesis validation"]},{"year":2025,"claim":"PTPMT1 was established as a human disease gene, with biallelic loss-of-function causing a recessive primary mitochondrial neurodevelopmental syndrome, and additional studies tied it to cardiac compaction, the integrated stress response, and ferroptosis susceptibility.","evidence":"Human genetics in 6 patients with patient-cell biochemistry and zebrafish KO; cardiac-specific KO with proliferation/ISR markers; HCC KO/overexpression with iron speciation and TCA metabolomics","pmids":["39279645","40700143","40189563"],"confidence":"High","gaps":["Genotype–phenotype correlation across patients incomplete","Mechanism connecting cardiolipin loss to ISR activation and ferroptosis not fully defined"]},{"year":null,"claim":"How PTPMT1 partitions between its PGP/cardiolipin and phosphatidylinositol-phosphate substrate activities, and how this balance dictates tissue-specific metabolic, developmental, and cell-death outcomes, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No quantitative substrate-flux model in vivo","Regulatory inputs controlling PTPMT1 activity beyond MK-STYX and splicing largely unknown","Structural basis of membrane substrate selection not established"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,7]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[6]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0,4,5]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[2,3]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,3,11]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[13]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[8,9]}],"complexes":[],"partners":["MK-STYX","SLC25A6","NDUFS2","UCP2","SRSF1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q8WUK0","full_name":"Phosphatidylglycerophosphatase and protein-tyrosine phosphatase 1","aliases":["PTEN-like phosphatase","Phosphoinositide lipid phosphatase","Protein-tyrosine phosphatase mitochondrial 1"],"length_aa":201,"mass_kda":22.8,"function":"Lipid phosphatase which dephosphorylates phosphatidylglycerophosphate (PGP) to phosphatidylglycerol (PG) (By similarity). PGP is an essential intermediate in the biosynthetic pathway of cardiolipin, a mitochondrial-specific phospholipid regulating the membrane integrity and activities of the organelle (PubMed:39279645). Has also been shown to display phosphatase activity toward phosphoprotein substrates, specifically mediates dephosphorylation of mitochondrial proteins, thereby playing an essential role in ATP production (By similarity). Has probably a preference for proteins phosphorylated on Ser and/or Thr residues compared to proteins phosphorylated on Tyr residues (By similarity). Probably involved in regulation of insulin secretion in pancreatic beta cells (By similarity). Prevents intrinsic apoptosis, by regulating mitochondrial membrane integrity (PubMed:24709986, PubMed:39279645)","subcellular_location":"Mitochondrion inner membrane","url":"https://www.uniprot.org/uniprotkb/Q8WUK0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/PTPMT1","classification":"Common Essential","n_dependent_lines":768,"n_total_lines":1208,"dependency_fraction":0.6357615894039735},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/PTPMT1","total_profiled":1310},"omim":[{"mim_id":"621199","title":"NEURODEVELOPMENTAL DISORDER WITH ATAXIA AND BRAIN ABNORMALITIES; NEDAXBA","url":"https://www.omim.org/entry/621199"},{"mim_id":"618574","title":"DUAL-SPECIFICITY PHOSPHATASE 29; DUSP29","url":"https://www.omim.org/entry/618574"},{"mim_id":"609538","title":"PROTEIN-TYROSINE PHOSPHATASE, MITOCHONDRIAL, 1; PTPMT1","url":"https://www.omim.org/entry/609538"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Mitochondria","reliability":"Enhanced"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PTPMT1"},"hgnc":{"alias_symbol":["PLIP","DUSP23","MOSP"],"prev_symbol":[]},"alphafold":{"accession":"Q8WUK0","domains":[{"cath_id":"3.90.190.10","chopping":"38-195","consensus_level":"high","plddt":96.2109,"start":38,"end":195}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WUK0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WUK0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8WUK0-F1-predicted_aligned_error_v6.png","plddt_mean":91.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PTPMT1","jax_strain_url":"https://www.jax.org/strain/search?query=PTPMT1"},"sequence":{"accession":"Q8WUK0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8WUK0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8WUK0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8WUK0"}},"corpus_meta":[{"pmid":"23290137","id":"PMC_23290137","title":"Metabolic regulation by the mitochondrial phosphatase PTPMT1 is required for hematopoietic stem cell differentiation.","date":"2013","source":"Cell stem cell","url":"https://pubmed.ncbi.nlm.nih.gov/23290137","citation_count":273,"is_preprint":false},{"pmid":"21641550","id":"PMC_21641550","title":"Mitochondrial phosphatase PTPMT1 is essential for cardiolipin biosynthesis.","date":"2011","source":"Cell metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/21641550","citation_count":176,"is_preprint":false},{"pmid":"30429088","id":"PMC_30429088","title":"SRSF1 modulates PTPMT1 alternative splicing to regulate lung cancer cell radioresistance.","date":"2018","source":"EBioMedicine","url":"https://pubmed.ncbi.nlm.nih.gov/30429088","citation_count":93,"is_preprint":false},{"pmid":"33992102","id":"PMC_33992102","title":"Splicing factor SRSF1 promotes breast cancer progression via oncogenic splice switching of PTPMT1.","date":"2021","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/33992102","citation_count":82,"is_preprint":false},{"pmid":"20167843","id":"PMC_20167843","title":"Pharmacological targeting of the mitochondrial phosphatase PTPMT1.","date":"2010","source":"The Journal of pharmacology and experimental therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/20167843","citation_count":57,"is_preprint":false},{"pmid":"25660020","id":"PMC_25660020","title":"PTPMT1 Inhibition Lowers Glucose through Succinate Dehydrogenase Phosphorylation.","date":"2015","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/25660020","citation_count":54,"is_preprint":false},{"pmid":"21730175","id":"PMC_21730175","title":"Structural and functional analysis of PTPMT1, a phosphatase required for cardiolipin synthesis.","date":"2011","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/21730175","citation_count":51,"is_preprint":false},{"pmid":"33503428","id":"PMC_33503428","title":"Genome-wide CRISPR-Cas9 knockout library screening identified PTPMT1 in cardiolipin synthesis is crucial to survival in hypoxia in liver cancer.","date":"2021","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/33503428","citation_count":46,"is_preprint":false},{"pmid":"21986498","id":"PMC_21986498","title":"A critical role of mitochondrial phosphatase Ptpmt1 in embryogenesis reveals a mitochondrial metabolic stress-induced differentiation checkpoint in embryonic stem cells.","date":"2011","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/21986498","citation_count":39,"is_preprint":false},{"pmid":"23326511","id":"PMC_23326511","title":"Downregulation of the mitochondrial phosphatase PTPMT1 is sufficient to promote cancer cell death.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23326511","citation_count":30,"is_preprint":false},{"pmid":"33335799","id":"PMC_33335799","title":"miR-150-PTPMT1-cardiolipin signaling in pulmonary arterial hypertension.","date":"2020","source":"Molecular therapy. Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/33335799","citation_count":25,"is_preprint":false},{"pmid":"24709986","id":"PMC_24709986","title":"The pseudophosphatase MK-STYX physically and genetically interacts with the mitochondrial phosphatase PTPMT1.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24709986","citation_count":24,"is_preprint":false},{"pmid":"22115589","id":"PMC_22115589","title":"Structure-based virtual screening approach to the discovery of novel PTPMT1 phosphatase inhibitors.","date":"2011","source":"Bioorganic & medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/22115589","citation_count":20,"is_preprint":false},{"pmid":"26898802","id":"PMC_26898802","title":"Ptpmt1 induced by HIF-2α regulates the proliferation and glucose metabolism in erythroleukemia cells.","date":"2016","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/26898802","citation_count":18,"is_preprint":false},{"pmid":"37154493","id":"PMC_37154493","title":"PTPMT1 protects cardiomyocytes from necroptosis induced by γ-ray irradiation through alleviating mitochondria injury.","date":"2023","source":"American journal of physiology. Cell physiology","url":"https://pubmed.ncbi.nlm.nih.gov/37154493","citation_count":17,"is_preprint":false},{"pmid":"40189563","id":"PMC_40189563","title":"Pharmacological targeting of the mitochondrial phosphatase PTPMT1 sensitizes hepatocellular carcinoma to ferroptosis.","date":"2025","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/40189563","citation_count":16,"is_preprint":false},{"pmid":"39279645","id":"PMC_39279645","title":"Biallelic PTPMT1 variants disrupt cardiolipin metabolism and lead to a neurodevelopmental syndrome.","date":"2025","source":"Brain : a journal of neurology","url":"https://pubmed.ncbi.nlm.nih.gov/39279645","citation_count":12,"is_preprint":false},{"pmid":"37672386","id":"PMC_37672386","title":"Loss of Ptpmt1 limits mitochondrial utilization of carbohydrates and leads to muscle atrophy and heart failure in tissue-specific knockout mice.","date":"2023","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/37672386","citation_count":11,"is_preprint":false},{"pmid":"21641541","id":"PMC_21641541","title":"PTPMT1: connecting cardiolipin biosynthesis to mitochondrial function.","date":"2011","source":"Cell metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/21641541","citation_count":10,"is_preprint":false},{"pmid":"32773109","id":"PMC_32773109","title":"A mitochondrial phosphatase PTPMT1 is essential for the early development of silkworm, Bombyx mori.","date":"2020","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/32773109","citation_count":8,"is_preprint":false},{"pmid":"37034225","id":"PMC_37034225","title":"PTPMT1 regulates mitochondrial death through the SLC25A6-NDUFS2 axis in pancreatic cancer cells.","date":"2023","source":"American journal of cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/37034225","citation_count":6,"is_preprint":false},{"pmid":"7800116","id":"PMC_7800116","title":"Developmental expression of MOSP in cultured oligodendrocytes.","date":"1994","source":"Neurochemical research","url":"https://pubmed.ncbi.nlm.nih.gov/7800116","citation_count":5,"is_preprint":false},{"pmid":"32629421","id":"PMC_32629421","title":"Drosophila PTPMT1 Has a Function in Tracheal Air Filling.","date":"2020","source":"iScience","url":"https://pubmed.ncbi.nlm.nih.gov/32629421","citation_count":4,"is_preprint":false},{"pmid":"16061174","id":"PMC_16061174","title":"Firing up mitochondrial activities with PTPMT1.","date":"2005","source":"Molecular cell","url":"https://pubmed.ncbi.nlm.nih.gov/16061174","citation_count":4,"is_preprint":false},{"pmid":"39816544","id":"PMC_39816544","title":"PTPMT1 inhibition induces apoptosis and growth arrest of human SCLC cells by disrupting mitochondrial metabolism.","date":"2024","source":"Translational cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/39816544","citation_count":3,"is_preprint":false},{"pmid":"38099467","id":"PMC_38099467","title":"Proteomic analysis by 4D label-free MS-PRM identified that Nptx1, Ptpmt1, Slc25a11, and Cpt1c are involved in diabetes-associated cognitive dysfunction.","date":"2023","source":"The International journal of neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/38099467","citation_count":2,"is_preprint":false},{"pmid":"40700143","id":"PMC_40700143","title":"Deletion of Ptpmt1 by αMHC-Cre in Mice Results in Left Ventricular Non-Compaction.","date":"2025","source":"Journal of developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/40700143","citation_count":0,"is_preprint":false},{"pmid":"35699926","id":"PMC_35699926","title":"The Mitochondrial Phosphatase PTPMT1 is Required for the Proper Growth Rate in the Red Flour Beetle, Tribolium castaneum.","date":"2022","source":"Zoological science","url":"https://pubmed.ncbi.nlm.nih.gov/35699926","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.09.30.679455","title":"BLTP1-dependent phospholipid efflux prevents mitochondrial lipid overload and apoptosis at FKBP8-tethered ER-mitochondrial contact","date":"2025-09-30","source":"bioRxiv","url":"https://doi.org/10.1101/2025.09.30.679455","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15517,"output_tokens":4669,"usd":0.058293,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13025,"output_tokens":4071,"usd":0.08345,"stage2_stop_reason":"end_turn"},"total_usd":0.141743,"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\": 2011,\n      \"finding\": \"PTPMT1 specifically dephosphorylates phosphatidylglycerophosphate (PGP) in vitro, acting as the mammalian PGP phosphatase required for cardiolipin biosynthesis; loss of PTPMT1 leads to PGP accumulation and dramatic reduction of cardiolipin, rescued by catalytically active but not catalytically dead PTPMT1.\",\n      \"method\": \"In vitro phosphatase assay, lipid analysis of Ptpmt1-deficient mouse embryonic fibroblasts, catalytic-dead rescue experiment\",\n      \"journal\": \"Cell Metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro enzymatic reconstitution with substrate, genetic KO with lipid mass spectrometry, and catalytic-mutant rescue all in one study; independently supported by multiple subsequent papers\",\n      \"pmids\": [\"21641550\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Crystal structures of the PTPMT1 phosphatase domain reveal a canonical dual-specificity PTP fold; the substrate-bound structure (with phosphatidylinositol 5-phosphate) defines the active site architecture and shows significant conformational change during catalysis; a conserved EEYE loop was experimentally shown to be important for catalytic activity.\",\n      \"method\": \"X-ray crystallography (apo and substrate-bound), EEYE loop mutagenesis with activity assay\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures with functional mutagenesis validation in one rigorous study\",\n      \"pmids\": [\"21730175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PTPMT1 localizes exclusively to mitochondria; its mitochondrial localization is required for function, as truncated PTPMT1 lacking the mitochondrial localization signal fails to rescue differentiation defects in Ptpmt1-knockout embryonic stem cells.\",\n      \"method\": \"Conditional knockout ES cells, rescue with wild-type vs. MLS-truncated PTPMT1 constructs, differentiation assays\",\n      \"journal\": \"Molecular and Cellular Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with defined cellular phenotype, MLS-deletion rescue experiment, replicated in HSC study (PMID:23290137)\",\n      \"pmids\": [\"21986498\", \"23290137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Loss of Ptpmt1 in embryonic fibroblasts causes decreased mitochondrial respiration, abnormal mitochondrial morphology, PGP accumulation, and reduced cardiolipin; whole-body Ptpmt1 deletion leads to embryonic lethality.\",\n      \"method\": \"Whole-body and conditional Ptpmt1 knockout mice, oxygen consumption measurements, electron microscopy, lipidomics\",\n      \"journal\": \"Cell Metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with multiple orthogonal phenotypic readouts (respiration, morphology, lipid mass spec) in one study\",\n      \"pmids\": [\"21641550\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Ptpmt1 depletion in embryonic stem cells blocks differentiation, increases cyclin-dependent kinase inhibitors, delays cell cycle, decreases oxygen consumption, and enhances glycolysis; accumulated phosphatidylinositol phosphates (PIPs) compromise mitochondrial fusion/dynamics.\",\n      \"method\": \"Conditional Ptpmt1 KO ES cells, cell cycle analysis, oxygen consumption and glycolysis assays, mitochondrial morphology imaging\",\n      \"journal\": \"Molecular and Cellular Biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional KO with multiple orthogonal mechanistic readouts in one rigorous study\",\n      \"pmids\": [\"21986498\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"PTPMT1 deficiency alters mitochondrial metabolism and its phosphatidylinositol phosphate substrates directly enhance fatty-acid-induced activation of mitochondrial uncoupling protein 2 (UCP2); catalytically deficient or MLS-lacking PTPMT1 fails to restore HSC differentiation, establishing catalytic activity and mitochondrial localization as essential.\",\n      \"method\": \"Inducible and hematopoietic-specific Ptpmt1 KO mice, rescue with WT vs. catalytic-dead vs. MLS-truncated PTPMT1, UCP2 activation assays\",\n      \"journal\": \"Cell Stem Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with rescue experiments and direct substrate-UCP2 activation assay; multiple orthogonal methods\",\n      \"pmids\": [\"23290137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PTPMT1 acts upstream of succinate dehydrogenase (SDH): pharmacological or genetic inactivation of PTPMT1 causes hyperphosphorylation and activation of SDH, providing a mechanism by which PTPMT1 regulates glucose homeostasis in zebrafish; ptpmt1 mutation eliminates the glucose-lowering effect of alexidine, confirming SDH as the downstream effector.\",\n      \"method\": \"Chemical screen in zebrafish, ptpmt1 genetic mutants, SDH phosphorylation and activity assays, glucose measurements\",\n      \"journal\": \"Cell Reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic epistasis in zebrafish with biochemical SDH phosphorylation readout; single lab, in vivo model\",\n      \"pmids\": [\"25660020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Alexidine dihydrochloride is a selective inhibitor of PTPMT1 (IC50 ~1.08 μM in vitro); treatment of pancreatic islets increases insulin secretion, and knockdown of PTPMT1 renders islets insensitive to alexidine, confirming mechanism-based activity; PTPMT1 inhibition affects phosphorylation of mitochondrial proteins in beta cells.\",\n      \"method\": \"In vitro phosphatase inhibition assay, rat pancreatic islet insulin secretion assay, PTPMT1 knockdown in islets\",\n      \"journal\": \"The Journal of Pharmacology and Experimental Therapeutics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — in vitro IC50 determination combined with genetic knockdown rescue in primary tissue confirming on-target activity\",\n      \"pmids\": [\"20167843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The pseudophosphatase MK-STYX physically interacts with PTPMT1 and suppresses its catalytic activity; knockdown of PTPMT1 resensitizes MK-STYX-knockdown cells to chemotherapeutics and restores cytochrome c release, placing MK-STYX as a negative regulator of PTPMT1 in apoptosis control.\",\n      \"method\": \"Unbiased proteomics (MS interactome), co-immunoprecipitation confirmation in cells, PTPMT1 activity assays, cytochrome c release assays, double-knockdown epistasis\",\n      \"journal\": \"PloS One\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-identified interaction confirmed by Co-IP, activity suppression assay, and epistasis; single lab\",\n      \"pmids\": [\"24709986\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Downregulation of PTPMT1 in cancer cells decreases cardiolipin levels, selectively increases ATP levels in glycolytic media, and induces apoptosis; sublethal PTPMT1 knockdown synergizes with paclitaxel, suggesting PTPMT1 loss causes a metabolic crisis.\",\n      \"method\": \"RNAi knockdown in cancer cell lines, cardiolipin quantification, ATP measurement, apoptosis assays, drug synergy assay\",\n      \"journal\": \"PloS One\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KD with defined metabolic and cell death phenotypes; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"23326511\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PTPMT1 interacts with mitochondrial proteins SLC25A6 and NDUFS2 as identified by co-immunoprecipitation, suggesting PTPMT1 modulates mitochondrial function via the SLC25A6-NDUFS2 axis in pancreatic cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, siRNA knockdown with viability and mitochondrial function assays\",\n      \"journal\": \"American Journal of Cancer Research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP identification without reciprocal validation or functional mutagenesis; single lab\",\n      \"pmids\": [\"37034225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Cardiac-specific and skeletal-muscle-specific deletion of Ptpmt1 inhibits pyruvate (carbohydrate-derived substrate) utilization in mitochondria while enhancing fatty acid utilization, causing oxidative stress, mitochondrial destruction, lipid accumulation, muscle atrophy, heart failure, and sudden death; liver- or adipose-specific deletion has no such effect.\",\n      \"method\": \"Tissue-specific Ptpmt1 KO mice, substrate oxidation assays, metabolomics, histology, cardiac function measurements\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean tissue-specific KO with multiple orthogonal metabolic and functional readouts; tissue-specificity controls strengthen mechanistic interpretation\",\n      \"pmids\": [\"37672386\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Knockout of PTPMT1 in hepatocellular carcinoma cells stops cardiolipin maturation and impairs assembly of electron transport chain (ETC) complexes, leading to electron leakage and ROS accumulation under hypoxia; PTPMT1 was identified as the top hit after HIF-1α/β in a genome-wide CRISPR-Cas9 knockout screen for hypoxic survival.\",\n      \"method\": \"Genome-wide CRISPR-Cas9 KO screen, PTPMT1 KO in HCC cells, ETC complex assembly assays, ROS measurement, cardiolipin quantification\",\n      \"journal\": \"Cell Reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — unbiased genome-wide screen validated with targeted KO plus multiple biochemical assays (ETC assembly, ROS, cardiolipin); single lab but orthogonal methods\",\n      \"pmids\": [\"33503428\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Biallelic loss-of-function variants in PTPMT1 in humans cause an autosomal recessive primary mitochondrial disease with neurodevelopmental syndrome; patient-derived fibroblasts and muscle tissue show impaired cardiolipin biosynthesis, mitochondrial structural and functional defects; ptpmt1 knockout zebrafish show decreased total cardiolipin and OXPHOS deficiency, confirming the disease mechanism.\",\n      \"method\": \"Human genetics (biallelic variants in 6 patients), patient-derived fibroblast and muscle studies, cellular rescue experiments, ptpmt1 KO zebrafish with cardiolipin and OXPHOS measurements\",\n      \"journal\": \"Brain\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human disease genetics validated by patient cell biochemistry and animal KO model with multiple orthogonal functional assays\",\n      \"pmids\": [\"39279645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Pharmacological inhibition of PTPMT1 by alexidine dihydrochloride increases susceptibility of hepatocellular carcinoma to ferroptosis by promoting conversion of ferritin-bound Fe3+ to free Fe2+, expanding the labile iron pool, inducing mitochondrial swelling and donut mitochondria formation, and enhancing succinate-to-fumarate metabolism in the TCA cycle.\",\n      \"method\": \"PTPMT1 KO and overexpression in HCC cell lines (CRISPR/Cas9 and lentiviral), alexidine treatment in vitro and in vivo, iron speciation assays, mitochondrial morphology imaging, TCA metabolomics\",\n      \"journal\": \"Cell Death & Disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO plus pharmacological inhibition with multiple biochemical readouts; single lab\",\n      \"pmids\": [\"40189563\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SRSF1 controls alternative splicing of PTPMT1; reduced SRSF1 favors production of short isoforms of PTPMT1 upon irradiation, which promotes AMPK phosphorylation and DNA double-strand breaks, sensitizing cancer cells to radiation.\",\n      \"method\": \"RNA-seq, RNA immunoprecipitation, minigene reporter assay, SRSF1 knockdown in lung cancer cell lines and xenografts\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CLIP confirmed SRSF1 binding, minigene validates splicing regulation, functional AMPK phosphorylation readout; single lab\",\n      \"pmids\": [\"30429088\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SRSF1 directly binds a motif in PTPMT1 exon 3 to regulate splice switching; the resulting PTPMT1 isoform change partially mediates SRSF1 oncogenic effects via the AKT/C-MYC axis in breast cancer cells.\",\n      \"method\": \"RIP-PCR, CLIP, minigene reporter assay, functional rescue in breast cancer cell lines and xenografts\",\n      \"journal\": \"Journal of Experimental & Clinical Cancer Research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding confirmed by CLIP, minigene validates splicing, downstream AKT/MYC pathway assays; single lab\",\n      \"pmids\": [\"33992102\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Depleting PTPMT1 (or CRLS1) rescues apoptosis caused by BLTP1 deficiency, placing PTPMT1-dependent cardiolipin synthesis upstream of apoptotic cell death triggered by mitochondrial phospholipid overload; this establishes PTPMT1 in the genetic epistasis pathway of mitochondrial phospholipid efflux.\",\n      \"method\": \"Genetic epistasis by siRNA co-depletion of BLTP1 and PTPMT1, apoptosis assays\",\n      \"journal\": \"bioRxiv (preprint)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — epistasis by knockdown in single preprint, no reciprocal validation or in vitro reconstitution\",\n      \"pmids\": [\"bio_10.1101_2025.09.30.679455\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Cardiac-specific deletion of Ptpmt1 (αMHC-Cre) causes left ventricular non-compaction with reduced cardiomyocyte proliferation at E15.5 and increased phosphorylated eIF2α and ATF4, indicating a mitochondrial stress response links PTPMT1 to cardiac compaction and the integrated stress response pathway.\",\n      \"method\": \"Cardiac-specific KO mice, morphological/histological analysis, EdU proliferation assay, RNA-seq, western blot for p-eIF2α and ATF4\",\n      \"journal\": \"Journal of Developmental Biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean tissue-specific KO with multiple readouts including proliferation and stress response markers; single lab, new study\",\n      \"pmids\": [\"40700143\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTPMT1 is a dual-specificity phosphatase exclusively localized to the inner mitochondrial membrane that dephosphorylates phosphatidylglycerophosphate (PGP) to phosphatidylglycerol as the committed step in cardiolipin biosynthesis; loss of cardiolipin destabilizes electron transport chain complexes, impairs mitochondrial respiration and dynamics, causes metabolic inflexibility (blocked pyruvate/carbohydrate utilization with compensatory fatty acid oxidation), and triggers oxidative stress and cell death; PTPMT1 additionally dephosphorylates phosphatidylinositol phosphates that regulate UCP2 activity and mitochondrial fusion, acts upstream of succinate dehydrogenase phosphorylation to influence glucose homeostasis, and is negatively regulated by the pseudophosphatase MK-STYX; its catalytic activity and mitochondrial localization are both required for supporting stem cell differentiation, cardiac development, and organismal viability.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PTPMT1 is a mitochondria-resident dual-specificity phosphatase that catalyzes the committed step of cardiolipin biosynthesis by dephosphorylating phosphatidylglycerophosphate (PGP) to phosphatidylglycerol; loss of activity causes PGP accumulation and severe cardiolipin depletion, an effect rescued only by catalytically active enzyme [#0]. Crystal structures define a canonical dual-specificity PTP fold with a conserved EEYE catalytic loop and a substrate-bound active site that undergoes conformational change during catalysis [#1], and both enzymatic activity and an intact mitochondrial localization signal are strictly required for biological function [#2, #5]. Through cardiolipin production, PTPMT1 is essential for electron transport chain complex assembly, mitochondrial respiration, and normal mitochondrial morphology; its loss impairs oxygen consumption, drives compensatory glycolysis, and causes ROS accumulation and metabolic crisis [#3, #4, #12]. Beyond cardiolipin, PTPMT1 turns over phosphatidylinositol phosphate substrates that potentiate fatty-acid activation of UCP2 and influence mitochondrial fusion [#4, #5], and acts upstream of succinate dehydrogenase phosphorylation to govern glucose homeostasis [#6]. At the organismal level, PTPMT1 supports stem cell and hematopoietic differentiation, and tissue-specific deletion in heart and skeletal muscle blocks pyruvate utilization while forcing fatty acid oxidation, producing oxidative stress, muscle atrophy, heart failure, and sudden death [#5, #11]. Biallelic loss-of-function variants in PTPMT1 cause an autosomal recessive primary mitochondrial disease with neurodevelopmental syndrome, with patient tissue showing impaired cardiolipin synthesis and mitochondrial dysfunction [#13]. The pseudophosphatase MK-STYX binds PTPMT1 and suppresses its activity, linking it to apoptotic control [#8], and the selective inhibitor alexidine dihydrochloride engages PTPMT1 on-target [#7].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"Establishing a chemical probe was the first step toward defining PTPMT1 function; identification of a selective small-molecule inhibitor enabled mechanism-based interrogation in primary tissue.\",\n      \"evidence\": \"In vitro phosphatase inhibition (IC50) plus PTPMT1 knockdown abolishing drug response in rat pancreatic islets\",\n      \"pmids\": [\"20167843\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the physiological substrate\", \"Mechanism linking PTPMT1 to insulin secretion left at protein-phosphorylation correlation\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"The central question of what PTPMT1 actually dephosphorylates was answered by identifying PGP as its substrate, defining PTPMT1 as the mammalian PGP phosphatase that commits lipid flux to cardiolipin.\",\n      \"evidence\": \"In vitro phosphatase assay with PGP, lipidomics of KO MEFs, and catalytic-dead rescue\",\n      \"pmids\": [\"21641550\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of PIP versus PGP substrates not resolved\", \"Whether PGP turnover alone accounts for all phenotypes unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Structural resolution of the phosphatase domain established the catalytic architecture, confirming a dual-specificity PTP fold and the functional EEYE loop.\",\n      \"evidence\": \"Apo and substrate-bound X-ray crystallography with EEYE loop mutagenesis and activity assays\",\n      \"pmids\": [\"21730175\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure solved with PI5P, not the native PGP substrate\", \"No structure of full-length membrane-embedded enzyme\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Genetic ablation established the physiological necessity of PTPMT1, showing that loss impairs respiration and mitochondrial morphology and is embryonic-lethal, and that mitochondrial localization is required for differentiation.\",\n      \"evidence\": \"Whole-body and conditional KO mice and ES cells with respirometry, EM, lipidomics, and MLS-truncation rescue\",\n      \"pmids\": [\"21641550\", \"21986498\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not separate cardiolipin-dependent from PIP-dependent effects\", \"Mechanism of differentiation block not fully resolved\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"PTPMT1 was connected to a second class of substrates and to apoptotic/metabolic control: its PIP products enhance UCP2 activation, and its loss triggers metabolic crisis and apoptosis in cancer cells.\",\n      \"evidence\": \"Hematopoietic-specific KO mice with catalytic and MLS rescue plus UCP2 assays; RNAi in cancer cells with cardiolipin, ATP, and apoptosis readouts\",\n      \"pmids\": [\"23290137\", \"23326511\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct enzymatic link between specific PIP species and UCP2 not structurally defined\", \"Cancer-cell apoptosis mechanism partly correlative\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"The first negative regulator of PTPMT1 was identified, showing that pseudophosphatase MK-STYX binds and suppresses its catalytic activity to modulate apoptosis.\",\n      \"evidence\": \"MS interactome, Co-IP, activity suppression assays, and double-knockdown epistasis on cytochrome c release\",\n      \"pmids\": [\"24709986\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab without reciprocal in vivo validation\", \"Structural basis of the inhibitory interaction unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"A downstream effector branch was defined by genetic epistasis, placing PTPMT1 upstream of SDH phosphorylation in control of glucose homeostasis.\",\n      \"evidence\": \"Zebrafish chemical screen and ptpmt1 mutants with SDH phosphorylation/activity and glucose assays\",\n      \"pmids\": [\"25660020\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct enzymatic mechanism linking PTPMT1 to SDH phosphorylation not shown\", \"Single in vivo model\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"PTPMT1 expression was shown to be controlled at the splicing level, with SRSF1 directing isoform switching that affects AMPK signaling and radiation sensitivity.\",\n      \"evidence\": \"RNA-seq, RIP/CLIP, minigene reporters, SRSF1 knockdown in lung cancer cells and xenografts\",\n      \"pmids\": [\"30429088\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional difference between short and full isoforms at the enzyme level not characterized\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"The SRSF1–PTPMT1 splicing axis was mapped to a specific exon 3 binding motif and linked to AKT/C-MYC-driven oncogenesis, while a CRISPR screen established PTPMT1 as critical for hypoxic survival via cardiolipin-dependent ETC assembly.\",\n      \"evidence\": \"RIP-PCR/CLIP and minigene reporters in breast cancer; genome-wide CRISPR-Cas9 screen with KO, ETC assembly, ROS, and cardiolipin assays in HCC cells\",\n      \"pmids\": [\"33992102\", \"33503428\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal contribution of isoform switch to tumor phenotype only partial\", \"ETC complex assembly defects shown biochemically but not at single-complex structural resolution\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Tissue-specific genetics revealed metabolic selectivity, showing PTPMT1 is required for pyruvate utilization in heart and skeletal muscle but dispensable in liver and adipose, with loss forcing fatty acid oxidation and causing lethal organ failure.\",\n      \"evidence\": \"Tissue-specific KO mice with substrate oxidation, metabolomics, histology, and cardiac function assays; Co-IP linking PTPMT1 to SLC25A6/NDUFS2\",\n      \"pmids\": [\"37672386\", \"37034225\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of tissue selectivity unresolved\", \"SLC25A6/NDUFS2 interactions are single Co-IP without reciprocal or mutagenesis validation\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"PTPMT1 was established as a human disease gene, with biallelic loss-of-function causing a recessive primary mitochondrial neurodevelopmental syndrome, and additional studies tied it to cardiac compaction, the integrated stress response, and ferroptosis susceptibility.\",\n      \"evidence\": \"Human genetics in 6 patients with patient-cell biochemistry and zebrafish KO; cardiac-specific KO with proliferation/ISR markers; HCC KO/overexpression with iron speciation and TCA metabolomics\",\n      \"pmids\": [\"39279645\", \"40700143\", \"40189563\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genotype–phenotype correlation across patients incomplete\", \"Mechanism connecting cardiolipin loss to ISR activation and ferroptosis not fully defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PTPMT1 partitions between its PGP/cardiolipin and phosphatidylinositol-phosphate substrate activities, and how this balance dictates tissue-specific metabolic, developmental, and cell-death outcomes, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No quantitative substrate-flux model in vivo\", \"Regulatory inputs controlling PTPMT1 activity beyond MK-STYX and splicing largely unknown\", \"Structural basis of membrane substrate selection not established\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 7]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0, 4, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0005743\", \"supporting_discovery_ids\": []}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 3, 11]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [13]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [8, 9]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"MK-STYX\", \"SLC25A6\", \"NDUFS2\", \"UCP2\", \"SRSF1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}