{"gene":"PTRH2","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2004,"finding":"PTRH2/Bit1 is a mitochondrial protein that is released into the cytoplasm during apoptosis, where it forms a complex with AES (a small Groucho/TLE protein) to induce caspase-independent apoptosis; integrin-mediated cell attachment to fibronectin counteracts this apoptotic effect.","method":"Subcellular fractionation, Co-immunoprecipitation, overexpression and knockdown in cell lines, apoptosis assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, fractionation, loss- and gain-of-function with defined apoptotic phenotype, replicated across multiple subsequent studies","pmids":["15006356"],"is_preprint":false},{"year":2008,"finding":"Protein kinase D (PKD) phosphorylates two serine residues (Ser5 and Ser87) in cytoplasmic PTRH2/Bit1, increasing its apoptotic activity; phosphorylation of Ser5 in the mitochondrial localization sequence promotes Bit1 release from mitochondria to cytoplasm. Integrin-mediated cell attachment inhibits PKD activity, thereby suppressing Bit1-mediated anoikis.","method":"In vitro phosphorylation assays, site-directed mutagenesis, pharmacological PKD inhibitors, siRNA knockdown, overexpression of constitutively active PKD","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — site-directed mutagenesis of specific phosphorylation sites, in vitro assays, multiple orthogonal approaches (pharmacological + genetic), single lab","pmids":["18703509"],"is_preprint":false},{"year":2008,"finding":"PTRH2/Bit1 knockout mice show increased ERK phosphorylation and decreased ERK phosphatase activity; Bit1 negatively regulates ERK signaling, and partial knockdown of ERK reversed the anoikis resistance of Bit1-null cells, placing Bit1 upstream of ERK in anoikis signaling.","method":"Conditional knockout mouse (Cre-LoxP), MEF culture, ERK phosphorylation assays, Erk knockdown epistasis","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO mouse model with epistasis rescue experiment and biochemical phosphatase activity assay, in vivo confirmation","pmids":["18218778"],"is_preprint":false},{"year":2011,"finding":"In adherent cells, PTRH2/Bit1 promotes cell survival through activation of the NF-κB pathway, increasing phospho-IκB levels and subsequent Bcl-2 gene transcription; this pro-survival function is dependent on focal adhesion kinase (FAK), PI3K, and AKT.","method":"shRNA knockdown, re-expression rescue, caspase-3 activation assays, TUNEL staining, Bcl-2 reporter/Western blot, pharmacological inhibition of FAK/PI3K/AKT","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (genetic knockdown, rescue, pathway inhibitors) in single lab","pmids":["21383007"],"is_preprint":false},{"year":2011,"finding":"βA3/A1-crystallin is required for trafficking of PTRH2/Bit1 to the Golgi; loss of βA3/A1-crystallin in astrocytes prevents Bit1 from reaching the Golgi, suppressing anoikis.","method":"In vitro anoikis induction, immunofluorescence/subcellular localization, Cryba1 mutant rat (Nuc1) model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — localization experiment with functional consequence in genetic model, single lab","pmids":["21993393"],"is_preprint":false},{"year":2010,"finding":"PTRH2/Bit1 localizes to the Golgi complex (in addition to mitochondria) and acts as a negative regulator of ERK-MAPK signaling from the Golgi; perturbation of BIT1 oligomerization/Golgi localization via a chimeric construct or BIT1 silencing led to enhanced ERK signaling and improved stress resistance.","method":"Proteomic analysis of ER membrane microdomains, chimeric protein approach, siRNA silencing, ERK signaling assays, stress resistance assays","journal":"Journal of cell science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — subcellular localization with functional consequence, two orthogonal perturbation approaches, single lab","pmids":["20197408"],"is_preprint":false},{"year":2012,"finding":"TLE1 inhibits the PTRH2/Bit1 anoikis pathway by sequestering the pro-apoptotic Bit1 partner AES in the nucleus, reducing Bit1-AES complex formation; conversely, cytoplasmic Bit1 induces cytoplasmic translocation and degradation of nuclear TLE1.","method":"Overexpression and knockdown of TLE1, Co-immunoprecipitation for Bit1-AES complex, subcellular fractionation, apoptosis assays","journal":"Molecular cancer research : MCR","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for complex formation, fractionation with functional readout, multiple genetic manipulations, single lab","pmids":["22952044"],"is_preprint":false},{"year":2014,"finding":"PTRH2/Bit1 controls skeletal myogenesis through a caspase-mediated signaling pathway; Bit1-null mice exhibit hypotrophic myofibers and premature muscle differentiation; Bit1-null myoblasts show increased caspase 9 and caspase 3 levels without apoptosis, and reduced Bcl-2; re-expression of Bcl-2 rescued premature differentiation in Bit1-null cells, placing Bit1 upstream of Bcl-2/caspase regulation during myogenesis.","method":"Ptrh2 knockout mouse, C2C12 knockdown/overexpression, caspase activity assays, Bcl-2 rescue experiments, muscle histology","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO mouse plus in vitro rescue epistasis with Bcl-2, multiple orthogonal methods, functional differentiation phenotype","pmids":["25770104"],"is_preprint":false},{"year":2014,"finding":"Homozygous frameshift mutations in PTRH2 cause infantile-onset multisystem disease (IMNEPD); PTRH2 is highly expressed in developing brain, is a key determinant of cell survival during tissue development, and is linked to the mTOR pathway controlling cell size, demonstrated in mutant mice and patient fibroblasts.","method":"Whole-exome sequencing, Sanger sequencing, mutant mouse analysis, patient fibroblast functional studies, mTOR pathway assays","journal":"Annals of clinical and translational neurology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — human genetics plus functional validation in mouse and patient cells, mTOR link from cell-based assays, single study","pmids":["25574476"],"is_preprint":false},{"year":2016,"finding":"PTRH2/Bit1 physically interacts with FAK protein; Bit1 knockdown in esophageal squamous cell carcinoma cells decreased FAK and paxillin expression at both mRNA and protein levels, identifying the FAK-paxillin pathway as a downstream effector of Bit1 in regulating cell migration and invasion.","method":"Co-immunoprecipitation (Bit1-FAK interaction), shRNA knockdown, gene microarray, Western blot, qRT-PCR, xenograft model","journal":"Molecular cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus downstream pathway validation by multiple methods, single lab","pmids":["26956728"],"is_preprint":false},{"year":2016,"finding":"PTRH2/Bit1 inhibits EMT in lung cancer by upregulating E-cadherin transcription through the AES co-activator, which blocks TLE1-mediated repression of the E-cadherin promoter; Bit1 decreases TLE1 occupancy at the E-cadherin promoter as shown by chromatin immunoprecipitation.","method":"siRNA/shRNA knockdown, ectopic overexpression, qRT-PCR, luciferase reporter assay, chromatin immunoprecipitation (ChIP), in vivo experimental metastasis model","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — ChIP assay directly demonstrating promoter occupancy, reporter assay, rescue experiments, in vivo validation; multiple orthogonal methods in single lab","pmids":["27655370"],"is_preprint":false},{"year":2017,"finding":"PTRH2 associates in a complex with α7β1 integrin at the sarcolemma in normal skeletal muscle; PTRH2 expression is decreased in α7 integrin null muscle, and Ptrh2 knockout mouse muscle recapitulates progressive muscular dystrophy-like pathology.","method":"Co-immunoprecipitation (Ptrh2-α7β1 integrin complex), immunofluorescence, muscle histology (H&E, creatine kinase assay, fibrosis staining), Ptrh2 KO and α7 integrin KO mouse comparison","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP for complex, KO mouse with defined muscle phenotype, cross-validation with α7 integrin KO; single lab","pmids":["28175314"],"is_preprint":false},{"year":2022,"finding":"Loss of PTRH2 specifically in Purkinje cells leads to reduced ribosomal protein S6 levels (a readout of mTOR pathway activity), PC atrophy with stunted dendrites, and progressive PC loss, establishing a cell-autonomous requirement for PTRH2 in PC maturation and survival via the mTOR pathway.","method":"PC-specific Ptrh2 conditional knockout mouse (Ptrh2ΔPC), cerebellar histology, gait/ataxia behavioral assays, immunostaining for S6 and PC markers","journal":"Cerebellum (London, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific genetic KO with defined cellular and molecular phenotype, single lab","pmids":["36219306"],"is_preprint":false},{"year":2025,"finding":"Mitochondrial PTRH2 interacts with the deubiquitinase TRABID and the respiratory complex I subunit mt-ND5; PTRH2 regulates TRABID's ability to deubiquitylate mt-ND5 — in the absence of PTRH2, TRABID aberrantly deubiquitylates mt-ND5, increasing its stability, which promotes complex I activity, elevated ATP production, and mitochondrial Ca2+ overload under stress conditions. Re-expression of mitochondrial PTRH2 blocks TRABID DUB activity toward mt-ND5, leading to mt-ND5 polyubiquitylation and proteasomal degradation.","method":"Co-immunoprecipitation/mass spectrometry proteomics, CRISPR/Cas9 knockout, re-expression rescue, ubiquitylation assays, complex I activity assay, ATP production measurement, mitochondrial Ca2+ imaging, PTRH2 KO mouse immunostaining","journal":"PNAS nexus","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — IP/MS interactome, ubiquitylation assays, enzymatic activity measurements, genetic KO with rescue, in vivo mouse confirmation; multiple orthogonal methods in single study","pmids":["40496187"],"is_preprint":false},{"year":2025,"finding":"PTRH2 interacts with MFN1/2 (mitofusins) and interferes with MFN dimerization, thereby suppressing mitochondrial fusion; disease-associated PTRH2 truncation mutants (A90fs, W108*) show enhanced binding to MFN1/2, causing mitochondrial fragmentation, perinuclear aggregation via FKBP8 recruitment, and impaired mitophagy.","method":"Gain-of-function screening, co-immunoprecipitation, TurboID proximity labeling, site-directed mutagenesis of PTRH2 disease mutants, CRISPR/Cas9 KO, confocal microscopy of mitochondrial morphology, mito-Keima mitophagy assay, ATP/membrane potential/ROS assays","journal":"Molecular medicine (Cambridge, Mass.)","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — multiple orthogonal methods (Co-IP, proximity labeling, mutagenesis, live imaging, functional assays), single lab but comprehensive mechanistic dissection","pmids":["41807994"],"is_preprint":false},{"year":2025,"finding":"In EGFR-TKI-sensitive lung cancer cells, TKI treatment triggers cytosolic release of mitochondrial outer membrane-associated PTRH2/Bit1 prior to cytochrome C release and independently of full MOMP; released Bit1 forms a complex with AES in the cytosol, causing nuclear exclusion and sequestration of TLE1, thereby activating apoptosis.","method":"Subcellular fractionation, viability and apoptosis assays, siRNA/shRNA knockdown, ectopic overexpression, RNA-sequencing of TLE1-regulated genes, drug-tolerant persister cell models","journal":"Anticancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — fractionation with functional readout, epistasis via genetic manipulation, transcriptomic characterization; single lab","pmids":["41895783"],"is_preprint":false},{"year":2025,"finding":"Newcastle disease virus (NDV) infection promotes translocation of PTRH2/Bit1 from mitochondria to cytoplasm in tumor cells, mirroring suspension-induced anoikis; overexpression of Bit1 in tumor cells accelerated NDV-mediated inhibition of melanoma metastasis and growth in vivo.","method":"Subcellular fractionation, immunofluorescence localization, Bit1 overexpression in vivo mouse melanoma model, viral infection assays","journal":"Virologica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — fractionation demonstrating translocation, in vivo overexpression with functional metastasis readout; single lab","pmids":["41130364"],"is_preprint":false}],"current_model":"PTRH2/Bit1 is a mitochondrial protein with peptidyl-tRNA hydrolase activity that serves as a multifunctional integrin effector: in adherent cells it promotes survival via NF-κB/Bcl-2 and suppresses ERK signaling from the Golgi; upon loss of cell attachment or apoptotic stimuli it is released from mitochondria (facilitated by PKD-mediated phosphorylation of Ser5/Ser87) into the cytoplasm where it complexes with AES to drive caspase-independent apoptosis and counteracts TLE1-mediated survival; within mitochondria it regulates metabolic homeostasis by controlling the deubiquitinase TRABID's activity toward the complex I subunit mt-ND5 and suppresses mitochondrial fusion by interfering with MFN1/2 dimerization, with disease-causing truncation mutants causing mitochondrial fragmentation and Ca2+ overload."},"narrative":{"mechanistic_narrative":"PTRH2 (Bit1) is a mitochondrial protein that functions as an integrin-coupled switch governing the balance between cell survival and anoikis during tissue development and homeostasis [PMID:15006356, PMID:18218778]. Upon loss of cell attachment or apoptotic stress, it is released from mitochondria into the cytoplasm—a step driven by PKD phosphorylation of Ser5/Ser87 and antagonized by integrin signaling—where it complexes with the Groucho/TLE protein AES to drive caspase-independent apoptosis [PMID:15006356, PMID:18703509]. The Bit1–AES module reciprocally controls TLE1: cytoplasmic Bit1 sequesters TLE1 away from the nucleus to relieve TLE1-mediated transcriptional repression, including derepression of the E-cadherin promoter to suppress epithelial–mesenchymal transition [PMID:22952044, PMID:27655370]. In adherent cells, PTRH2 instead promotes survival through a FAK/PI3K/AKT–dependent NF-κB axis that drives Bcl-2 transcription, and it acts as a Golgi-localized negative regulator of ERK-MAPK signaling [PMID:21383007, PMID:20197408, PMID:18218778]. Within mitochondria, PTRH2 regulates metabolic and morphological homeostasis: it restrains the deubiquitinase TRABID to promote ubiquitin-dependent turnover of the complex I subunit mt-ND5, limiting complex I activity, ATP output, and Ca2+ overload, and it binds mitofusins MFN1/2 to block their dimerization and suppress mitochondrial fusion [PMID:40496187, PMID:41807994]. These activities underlie its developmental roles in skeletal myogenesis and muscle integrity, where it associates with α7β1 integrin at the sarcolemma, and in cerebellar Purkinje cell maturation via the mTOR pathway [PMID:25770104, PMID:28175314, PMID:36219306]. Homozygous frameshift mutations in PTRH2 cause infantile-onset multisystem neurologic, endocrine, and pancreatic disease (IMNEPD), and disease-associated truncation mutants show enhanced MFN binding, mitochondrial fragmentation, and impaired mitophagy [PMID:25574476, PMID:41807994].","teleology":[{"year":2004,"claim":"Established PTRH2/Bit1 as a mitochondrially-sequestered apoptotic effector, answering how cells couple loss of integrin-mediated attachment to a death signal.","evidence":"Subcellular fractionation, reciprocal Co-IP with AES, gain/loss-of-function apoptosis assays in cell lines","pmids":["15006356"],"confidence":"High","gaps":["Did not define the molecular trigger for mitochondrial release","Mechanism by which the Bit1-AES complex executes caspase-independent death unresolved"]},{"year":2008,"claim":"Identified the regulatory mechanism for Bit1 mitochondrial release, linking integrin status to PKD-mediated phosphorylation of the localization sequence.","evidence":"In vitro phosphorylation, site-directed mutagenesis of Ser5/Ser87, PKD inhibitors and siRNA in cell lines","pmids":["18703509"],"confidence":"High","gaps":["Did not resolve how Ser5 phosphorylation physically destabilizes mitochondrial retention","Other potential regulatory kinases not excluded"]},{"year":2008,"claim":"Placed Bit1 genetically upstream of ERK in anoikis signaling, defining it as a negative regulator of ERK with phosphatase-modulating activity.","evidence":"Conditional Ptrh2 KO mouse, MEF ERK phosphorylation and phosphatase assays, ERK knockdown epistasis","pmids":["18218778"],"confidence":"High","gaps":["Direct ERK phosphatase substrate/target not identified","Connection between mitochondrial pool and ERK regulation unclear"]},{"year":2010,"claim":"Demonstrated a second subcellular pool of Bit1 at the Golgi acting as a brake on ERK-MAPK and stress resistance, broadening its role beyond mitochondria.","evidence":"Proteomic analysis of ER/membrane microdomains, chimeric construct and siRNA perturbation, ERK and stress assays","pmids":["20197408"],"confidence":"Medium","gaps":["Single lab; mechanism of Golgi ERK suppression not biochemically defined","Relationship between Golgi and mitochondrial functions unresolved"]},{"year":2011,"claim":"Revealed the pro-survival face of Bit1 in adherent cells, showing it drives Bcl-2 via FAK/PI3K/AKT-dependent NF-κB activation.","evidence":"shRNA knockdown with rescue, caspase/TUNEL assays, Bcl-2 readouts, FAK/PI3K/AKT inhibitors","pmids":["21383007"],"confidence":"Medium","gaps":["Direct molecular link from Bit1 to the NF-κB module not defined","Single-lab pathway dissection"]},{"year":2011,"claim":"Identified βA3/A1-crystallin as a trafficking factor required to deliver Bit1 to the Golgi, controlling its anoikis competence in astrocytes.","evidence":"Anoikis assays, immunofluorescence localization, Cryba1 mutant (Nuc1) rat model","pmids":["21993393"],"confidence":"Medium","gaps":["Trafficking mechanism and direct interaction not characterized","Generality beyond astrocytes untested"]},{"year":2012,"claim":"Defined a reciprocal antagonism between Bit1 and TLE1, explaining how survival signals restrain the apoptotic Bit1-AES complex.","evidence":"TLE1 overexpression/knockdown, Co-IP for Bit1-AES, fractionation, apoptosis assays","pmids":["22952044"],"confidence":"Medium","gaps":["Stoichiometry and direct vs indirect AES competition not resolved","Single lab"]},{"year":2014,"claim":"Linked PTRH2 to developmental control of skeletal myogenesis via a Bcl-2/caspase axis, showing non-apoptotic caspase signaling regulates differentiation timing.","evidence":"Ptrh2 KO mouse, C2C12 manipulation, caspase assays, Bcl-2 rescue, muscle histology","pmids":["25770104"],"confidence":"High","gaps":["Direct molecular target by which Bit1 controls Bcl-2 in myoblasts not defined","Mitochondrial vs cytoplasmic pool contribution unclear"]},{"year":2014,"claim":"Connected PTRH2 loss-of-function to a human Mendelian multisystem disease (IMNEPD) and to mTOR-dependent control of cell size.","evidence":"Whole-exome sequencing, mutant mouse and patient fibroblast functional studies, mTOR assays","pmids":["25574476"],"confidence":"Medium","gaps":["Mechanistic link between peptidyl-tRNA hydrolase activity and mTOR not established","Single study"]},{"year":2016,"claim":"Identified Bit1 as a transcriptional suppressor of EMT through AES-mediated derepression of the E-cadherin promoter, integrating the AES/TLE1 axis with cancer cell behavior.","evidence":"ChIP for TLE1 promoter occupancy, luciferase reporter, knockdown/overexpression, in vivo metastasis model","pmids":["27655370"],"confidence":"High","gaps":["Whether nuclear Bit1 or cytoplasmic sequestration drives derepression not fully separated","Range of TLE1 target genes not surveyed"]},{"year":2016,"claim":"Showed a physical Bit1-FAK interaction feeding into the FAK-paxillin migration/invasion pathway, complementing the FAK-dependent survival role.","evidence":"Co-IP, shRNA knockdown, microarray, qRT-PCR/Western, xenograft in ESCC cells","pmids":["26956728"],"confidence":"Medium","gaps":["Direct vs scaffold-mediated FAK binding not resolved","Single lab"]},{"year":2017,"claim":"Placed PTRH2 in a sarcolemmal complex with α7β1 integrin, tying its muscle phenotype to integrin biology in vivo.","evidence":"Co-IP, immunofluorescence, muscle histology, Ptrh2 KO vs α7 integrin KO mouse comparison","pmids":["28175314"],"confidence":"Medium","gaps":["Direct binding partner within the integrin complex not mapped","Functional consequence of the complex mechanistically undefined"]},{"year":2022,"claim":"Established a cell-autonomous requirement for PTRH2 in cerebellar Purkinje cell maturation and survival via mTOR/S6 signaling, refining the neurological basis of IMNEPD.","evidence":"PC-specific conditional KO mouse, cerebellar histology, ataxia behavior, S6 immunostaining","pmids":["36219306"],"confidence":"Medium","gaps":["Molecular link from PTRH2 to mTOR/S6 in neurons not defined","Single lab"]},{"year":2025,"claim":"Defined a mitochondrial metabolic role for PTRH2 as a regulator of the TRABID deubiquitinase, controlling mt-ND5 stability, complex I activity, and Ca2+ homeostasis.","evidence":"IP/MS interactome, CRISPR KO and rescue, ubiquitylation assays, complex I and ATP assays, Ca2+ imaging, KO mouse","pmids":["40496187"],"confidence":"High","gaps":["How PTRH2 mechanistically inhibits TRABID DUB activity unresolved","Role of catalytic peptidyl-tRNA hydrolase activity in this function untested"]},{"year":2025,"claim":"Identified PTRH2 as a suppressor of mitochondrial fusion via MFN1/2 binding, and showed disease truncation mutants gain enhanced MFN binding causing fragmentation and impaired mitophagy.","evidence":"GoF screening, Co-IP, TurboID, disease-mutant mutagenesis, CRISPR KO, confocal morphology, mito-Keima mitophagy and functional assays","pmids":["41807994"],"confidence":"High","gaps":["Structural basis of MFN dimerization interference not solved","How truncation enhances MFN binding mechanistically unclear"]},{"year":2025,"claim":"Extended the anoikis/apoptosis mechanism to therapeutic contexts, showing EGFR-TKI and oncolytic virus trigger Bit1 cytosolic release and AES/TLE1-dependent apoptosis.","evidence":"Fractionation, viability/apoptosis assays, knockdown/overexpression, RNA-seq of TLE1 targets, drug-tolerant persister and in vivo melanoma models","pmids":["41895783","41130364"],"confidence":"Medium","gaps":["How TKI/viral stress signals to Bit1 release mechanistically unknown","Relationship to canonical MOMP/cytochrome C release only partially defined"]},{"year":null,"claim":"How PTRH2's enzymatic peptidyl-tRNA hydrolase activity relates to its diverse signaling, mitochondrial metabolic, and morphological functions remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No discovery links catalytic activity to the integrin/anoikis, TRABID, or MFN functions","Integration across mitochondrial, Golgi, and cytoplasmic pools lacks a unifying mechanism","No structural model of substrate or partner complexes"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[13]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[13,14]},{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[10,6]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,13,14]},{"term_id":"GO:0005794","term_label":"Golgi apparatus","supporting_discovery_ids":[5,4]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,15]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[11]}],"pathway":[{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,1,15]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,3,5]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[13]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[14]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[7,12]}],"complexes":["Bit1-AES complex","α7β1 integrin complex"],"partners":["AES","TLE1","FAK","TRABID","MT-ND5","MFN1","MFN2","ITGA7"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9Y3E5","full_name":"Peptidyl-tRNA hydrolase 2, mitochondrial","aliases":["Bcl-2 inhibitor of transcription 1"],"length_aa":179,"mass_kda":19.2,"function":"Peptidyl-tRNA hydrolase which releases tRNAs from the ribosome during protein synthesis (PubMed:14660562). Promotes caspase-independent apoptosis by regulating the function of two transcriptional regulators, AES and TLE1","subcellular_location":"Mitochondrion outer membrane","url":"https://www.uniprot.org/uniprotkb/Q9Y3E5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PTRH2","classification":"Not Classified","n_dependent_lines":18,"n_total_lines":1208,"dependency_fraction":0.014900662251655629},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CANX","stoichiometry":0.2},{"gene":"SEC61B","stoichiometry":0.2},{"gene":"CCDC47","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/PTRH2","total_profiled":1310},"omim":[{"mim_id":"616263","title":"NEUROLOGIC, ENDOCRINE, AND PANCREATIC DISEASE, MULTISYSTEM, INFANTILE-ONSET 1; IMNEPD1","url":"https://www.omim.org/entry/616263"},{"mim_id":"608625","title":"PEPTIDYL-tRNA HYDROLASE 2; PTRH2","url":"https://www.omim.org/entry/608625"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PTRH2"},"hgnc":{"alias_symbol":["BIT1","CGI-147","PTH2","CFAP37"],"prev_symbol":[]},"alphafold":{"accession":"Q9Y3E5","domains":[{"cath_id":"3.40.1490.10","chopping":"64-173","consensus_level":"high","plddt":95.7225,"start":64,"end":173},{"cath_id":"1.20.5","chopping":"1-36","consensus_level":"high","plddt":72.6653,"start":1,"end":36}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y3E5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y3E5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9Y3E5-F1-predicted_aligned_error_v6.png","plddt_mean":83.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PTRH2","jax_strain_url":"https://www.jax.org/strain/search?query=PTRH2"},"sequence":{"accession":"Q9Y3E5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9Y3E5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9Y3E5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9Y3E5"}},"corpus_meta":[{"pmid":"15006356","id":"PMC_15006356","title":"A mitochondrial protein, Bit1, mediates apoptosis regulated by integrins and Groucho/TLE corepressors.","date":"2004","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/15006356","citation_count":144,"is_preprint":false},{"pmid":"21383007","id":"PMC_21383007","title":"Bit-1 mediates integrin-dependent cell survival through activation of the NFkappaB pathway.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21383007","citation_count":41,"is_preprint":false},{"pmid":"22952044","id":"PMC_22952044","title":"TLE1 is an anoikis regulator and is downregulated by Bit1 in breast cancer cells.","date":"2012","source":"Molecular cancer research : MCR","url":"https://pubmed.ncbi.nlm.nih.gov/22952044","citation_count":40,"is_preprint":false},{"pmid":"21993393","id":"PMC_21993393","title":"βA3/A1-Crystallin controls anoikis-mediated cell death in astrocytes by modulating PI3K/AKT/mTOR and ERK survival pathways through the PKD/Bit1-signaling axis.","date":"2011","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/21993393","citation_count":40,"is_preprint":false},{"pmid":"18218778","id":"PMC_18218778","title":"Anoikis effector Bit1 negatively regulates Erk activity.","date":"2008","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/18218778","citation_count":38,"is_preprint":false},{"pmid":"17511679","id":"PMC_17511679","title":"Induction of Anoikis following myoblast transplantation into SCID mouse muscles requires the Bit1 and FADD pathways.","date":"2007","source":"American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons","url":"https://pubmed.ncbi.nlm.nih.gov/17511679","citation_count":37,"is_preprint":false},{"pmid":"26956728","id":"PMC_26956728","title":"Bit1 knockdown contributes to growth suppression as well as the decreases of migration and invasion abilities in esophageal squamous cell carcinoma via suppressing FAK-paxillin pathway.","date":"2016","source":"Molecular cancer","url":"https://pubmed.ncbi.nlm.nih.gov/26956728","citation_count":36,"is_preprint":false},{"pmid":"25574476","id":"PMC_25574476","title":"Mutations in PTRH2 cause novel infantile-onset multisystem disease with intellectual disability, microcephaly, progressive ataxia, and muscle weakness.","date":"2014","source":"Annals of clinical and translational neurology","url":"https://pubmed.ncbi.nlm.nih.gov/25574476","citation_count":35,"is_preprint":false},{"pmid":"18703509","id":"PMC_18703509","title":"Protein kinase D is a positive regulator of Bit1 apoptotic function.","date":"2008","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18703509","citation_count":30,"is_preprint":false},{"pmid":"25003198","id":"PMC_25003198","title":"The anoikis effector Bit1 displays tumor suppressive function in lung cancer cells.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25003198","citation_count":30,"is_preprint":false},{"pmid":"23376255","id":"PMC_23376255","title":"Bit1 in anoikis resistance and tumor metastasis.","date":"2013","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/23376255","citation_count":29,"is_preprint":false},{"pmid":"21886829","id":"PMC_21886829","title":"Metastasis of tumor cells is enhanced by downregulation of Bit1.","date":"2011","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/21886829","citation_count":27,"is_preprint":false},{"pmid":"33298880","id":"PMC_33298880","title":"PTRH2: an adhesion regulated molecular switch at the nexus of life, death, and differentiation.","date":"2020","source":"Cell death discovery","url":"https://pubmed.ncbi.nlm.nih.gov/33298880","citation_count":24,"is_preprint":false},{"pmid":"25770104","id":"PMC_25770104","title":"Bit-1 is an essential regulator of myogenic differentiation.","date":"2015","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/25770104","citation_count":18,"is_preprint":false},{"pmid":"28328138","id":"PMC_28328138","title":"Homozygous mutation in PTRH2 gene causes progressive sensorineural deafness and peripheral neuropathy.","date":"2017","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/28328138","citation_count":16,"is_preprint":false},{"pmid":"23955799","id":"PMC_23955799","title":"Implications of Bit1 and AIF overexpressions in esophageal squamous cell carcinoma.","date":"2013","source":"Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/23955799","citation_count":15,"is_preprint":false},{"pmid":"27655370","id":"PMC_27655370","title":"The Anoikis Effector Bit1 Inhibits EMT through Attenuation of TLE1-Mediated Repression of E-Cadherin in Lung Cancer Cells.","date":"2016","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/27655370","citation_count":15,"is_preprint":false},{"pmid":"28175314","id":"PMC_28175314","title":"PTRH2 gene mutation causes progressive congenital skeletal muscle pathology.","date":"2017","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28175314","citation_count":13,"is_preprint":false},{"pmid":"29170133","id":"PMC_29170133","title":"Downregulation of Bit1 expression promotes growth, anoikis resistance, and transformation of immortalized human bronchial epithelial cells via Erk activation-dependent suppression of E-cadherin.","date":"2017","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/29170133","citation_count":12,"is_preprint":false},{"pmid":"20197408","id":"PMC_20197408","title":"MAPK scaffolding by BIT1 in the Golgi complex modulates stress resistance.","date":"2010","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/20197408","citation_count":11,"is_preprint":false},{"pmid":"33092935","id":"PMC_33092935","title":"Diabetes mellitus in an adolescent girl with intellectual disability caused by novel single base pair duplication in the PTRH2 gene: Expanding the clinical spectrum of IMNEPD.","date":"2020","source":"Brain & development","url":"https://pubmed.ncbi.nlm.nih.gov/33092935","citation_count":11,"is_preprint":false},{"pmid":"34112751","id":"PMC_34112751","title":"A novel PTRH2 missense mutation causing IMNEPD: a case report.","date":"2021","source":"Human genome variation","url":"https://pubmed.ncbi.nlm.nih.gov/34112751","citation_count":10,"is_preprint":false},{"pmid":"33717719","id":"PMC_33717719","title":"A Novel Synergistic Association of Variants in PTRH2 and KIF1A Relates to a Syndrome of Hereditary Axonopathy, Outer Hair Cell Dysfunction, Intellectual Disability, Pancreatic Lipomatosis, Diabetes, Cerebellar Atrophy, and Vertebral Artery Hypoplasia.","date":"2021","source":"Cureus","url":"https://pubmed.ncbi.nlm.nih.gov/33717719","citation_count":8,"is_preprint":false},{"pmid":"25211327","id":"PMC_25211327","title":"Estrogen decreases anoikis of ovarian cancer cell line Caov-3 through reducing release of Bit1.","date":"2014","source":"DNA and cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/25211327","citation_count":8,"is_preprint":false},{"pmid":"27122244","id":"PMC_27122244","title":"Bit1-a potential positive regulator of epithelial-mesenchymal transition in lens epithelial cells.","date":"2016","source":"Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie","url":"https://pubmed.ncbi.nlm.nih.gov/27122244","citation_count":6,"is_preprint":false},{"pmid":"32273719","id":"PMC_32273719","title":"Bit1 Silencing Enhances the Proliferation, Migration, and Invasion of Glioma Cells Through Activation of the IL-6/STAT3 Pathway.","date":"2020","source":"OncoTargets and therapy","url":"https://pubmed.ncbi.nlm.nih.gov/32273719","citation_count":5,"is_preprint":false},{"pmid":"19519243","id":"PMC_19519243","title":"Monoclonal antibodies against human bit1, an apoptosis-associated mitochondrial protein.","date":"2009","source":"Hybridoma (2005)","url":"https://pubmed.ncbi.nlm.nih.gov/19519243","citation_count":5,"is_preprint":false},{"pmid":"28419846","id":"PMC_28419846","title":"Bit1 Regulates Cell Migration and Survival in Oral Squamous Cell Carcinoma.","date":"2017","source":"Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons","url":"https://pubmed.ncbi.nlm.nih.gov/28419846","citation_count":4,"is_preprint":false},{"pmid":"36219306","id":"PMC_36219306","title":"PTRH2 is Necessary for Purkinje Cell Differentiation and Survival and its Loss Recapitulates Progressive Cerebellar Atrophy and Ataxia Seen in IMNEPD Patients.","date":"2022","source":"Cerebellum (London, England)","url":"https://pubmed.ncbi.nlm.nih.gov/36219306","citation_count":3,"is_preprint":false},{"pmid":"31368047","id":"PMC_31368047","title":"Bit1-a novel regulator of astrocyte function during retinal development: proliferation, migration, and paracrine effects on vascular endothelial cell.","date":"2019","source":"Human cell","url":"https://pubmed.ncbi.nlm.nih.gov/31368047","citation_count":2,"is_preprint":false},{"pmid":"38510576","id":"PMC_38510576","title":"A Novel PTRH2 Gene Mutation Causing Infantile-onset Multisystem Neurologic, Endocrine, and Pancreatic Disease in a Bahraini Patient.","date":"2024","source":"Oman medical journal","url":"https://pubmed.ncbi.nlm.nih.gov/38510576","citation_count":2,"is_preprint":false},{"pmid":"35737738","id":"PMC_35737738","title":"Bit1 is involved in regulation between integrin and TGFβ signaling in lens epithelial cells.","date":"2022","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/35737738","citation_count":1,"is_preprint":false},{"pmid":"28488526","id":"PMC_28488526","title":"Preliminary evaluation for Bit1 as a potential biomarker for squamous cell carcinoma and adenocarcinoma of esophagus.","date":"2017","source":"Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/28488526","citation_count":1,"is_preprint":false},{"pmid":"41130364","id":"PMC_41130364","title":"Oncolytic Newcastle disease virus promotes tumor cell death via the anoikis effector Bit1 translocation.","date":"2025","source":"Virologica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/41130364","citation_count":1,"is_preprint":false},{"pmid":"40455389","id":"PMC_40455389","title":"Bit1 promotes the progression of gastric cancer by facilitating epithelial-mesenchymal transition and alleviating apoptosis.","date":"2025","source":"Medical oncology (Northwood, London, England)","url":"https://pubmed.ncbi.nlm.nih.gov/40455389","citation_count":0,"is_preprint":false},{"pmid":"40496187","id":"PMC_40496187","title":"Mitochondrial PTRH2 controls the deubiquitinase TRABID to regulate mt-ND5 stability and metabolism.","date":"2025","source":"PNAS nexus","url":"https://pubmed.ncbi.nlm.nih.gov/40496187","citation_count":0,"is_preprint":false},{"pmid":"29136735","id":"PMC_29136735","title":"[Bit1 mediates the malignant behaviors in pancreatic cancer and its potential clinical significance].","date":"2017","source":"Zhonghua wai ke za zhi [Chinese journal of surgery]","url":"https://pubmed.ncbi.nlm.nih.gov/29136735","citation_count":0,"is_preprint":false},{"pmid":"41895783","id":"PMC_41895783","title":"BIT1 as an Effector of EGFR-TKI-induced Apoptosis via TLE1 Inhibition in Lung Adenocarcinoma Cells.","date":"2026","source":"Anticancer research","url":"https://pubmed.ncbi.nlm.nih.gov/41895783","citation_count":0,"is_preprint":false},{"pmid":"41807994","id":"PMC_41807994","title":"Pathogenic roles of the IMNEPD-associated PTRH2 mutants in aggravating mitochondrial dynamics and its rescue.","date":"2026","source":"Molecular medicine (Cambridge, Mass.)","url":"https://pubmed.ncbi.nlm.nih.gov/41807994","citation_count":0,"is_preprint":false},{"pmid":"42136678","id":"PMC_42136678","title":"Case Report: ALK-positive histiocytosis with a novel PTRH2::ALK fusion masquerading as a liver abscess in an infant.","date":"2026","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/42136678","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":23160,"output_tokens":4530,"usd":0.068715,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12627,"output_tokens":5115,"usd":0.095505,"stage2_stop_reason":"end_turn"},"total_usd":0.16422,"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\": 2004,\n      \"finding\": \"PTRH2/Bit1 is a mitochondrial protein that is released into the cytoplasm during apoptosis, where it forms a complex with AES (a small Groucho/TLE protein) to induce caspase-independent apoptosis; integrin-mediated cell attachment to fibronectin counteracts this apoptotic effect.\",\n      \"method\": \"Subcellular fractionation, Co-immunoprecipitation, overexpression and knockdown in cell lines, apoptosis assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, fractionation, loss- and gain-of-function with defined apoptotic phenotype, replicated across multiple subsequent studies\",\n      \"pmids\": [\"15006356\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Protein kinase D (PKD) phosphorylates two serine residues (Ser5 and Ser87) in cytoplasmic PTRH2/Bit1, increasing its apoptotic activity; phosphorylation of Ser5 in the mitochondrial localization sequence promotes Bit1 release from mitochondria to cytoplasm. Integrin-mediated cell attachment inhibits PKD activity, thereby suppressing Bit1-mediated anoikis.\",\n      \"method\": \"In vitro phosphorylation assays, site-directed mutagenesis, pharmacological PKD inhibitors, siRNA knockdown, overexpression of constitutively active PKD\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — site-directed mutagenesis of specific phosphorylation sites, in vitro assays, multiple orthogonal approaches (pharmacological + genetic), single lab\",\n      \"pmids\": [\"18703509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"PTRH2/Bit1 knockout mice show increased ERK phosphorylation and decreased ERK phosphatase activity; Bit1 negatively regulates ERK signaling, and partial knockdown of ERK reversed the anoikis resistance of Bit1-null cells, placing Bit1 upstream of ERK in anoikis signaling.\",\n      \"method\": \"Conditional knockout mouse (Cre-LoxP), MEF culture, ERK phosphorylation assays, Erk knockdown epistasis\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO mouse model with epistasis rescue experiment and biochemical phosphatase activity assay, in vivo confirmation\",\n      \"pmids\": [\"18218778\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In adherent cells, PTRH2/Bit1 promotes cell survival through activation of the NF-κB pathway, increasing phospho-IκB levels and subsequent Bcl-2 gene transcription; this pro-survival function is dependent on focal adhesion kinase (FAK), PI3K, and AKT.\",\n      \"method\": \"shRNA knockdown, re-expression rescue, caspase-3 activation assays, TUNEL staining, Bcl-2 reporter/Western blot, pharmacological inhibition of FAK/PI3K/AKT\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (genetic knockdown, rescue, pathway inhibitors) in single lab\",\n      \"pmids\": [\"21383007\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"βA3/A1-crystallin is required for trafficking of PTRH2/Bit1 to the Golgi; loss of βA3/A1-crystallin in astrocytes prevents Bit1 from reaching the Golgi, suppressing anoikis.\",\n      \"method\": \"In vitro anoikis induction, immunofluorescence/subcellular localization, Cryba1 mutant rat (Nuc1) model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — localization experiment with functional consequence in genetic model, single lab\",\n      \"pmids\": [\"21993393\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PTRH2/Bit1 localizes to the Golgi complex (in addition to mitochondria) and acts as a negative regulator of ERK-MAPK signaling from the Golgi; perturbation of BIT1 oligomerization/Golgi localization via a chimeric construct or BIT1 silencing led to enhanced ERK signaling and improved stress resistance.\",\n      \"method\": \"Proteomic analysis of ER membrane microdomains, chimeric protein approach, siRNA silencing, ERK signaling assays, stress resistance assays\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — subcellular localization with functional consequence, two orthogonal perturbation approaches, single lab\",\n      \"pmids\": [\"20197408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"TLE1 inhibits the PTRH2/Bit1 anoikis pathway by sequestering the pro-apoptotic Bit1 partner AES in the nucleus, reducing Bit1-AES complex formation; conversely, cytoplasmic Bit1 induces cytoplasmic translocation and degradation of nuclear TLE1.\",\n      \"method\": \"Overexpression and knockdown of TLE1, Co-immunoprecipitation for Bit1-AES complex, subcellular fractionation, apoptosis assays\",\n      \"journal\": \"Molecular cancer research : MCR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for complex formation, fractionation with functional readout, multiple genetic manipulations, single lab\",\n      \"pmids\": [\"22952044\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PTRH2/Bit1 controls skeletal myogenesis through a caspase-mediated signaling pathway; Bit1-null mice exhibit hypotrophic myofibers and premature muscle differentiation; Bit1-null myoblasts show increased caspase 9 and caspase 3 levels without apoptosis, and reduced Bcl-2; re-expression of Bcl-2 rescued premature differentiation in Bit1-null cells, placing Bit1 upstream of Bcl-2/caspase regulation during myogenesis.\",\n      \"method\": \"Ptrh2 knockout mouse, C2C12 knockdown/overexpression, caspase activity assays, Bcl-2 rescue experiments, muscle histology\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO mouse plus in vitro rescue epistasis with Bcl-2, multiple orthogonal methods, functional differentiation phenotype\",\n      \"pmids\": [\"25770104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Homozygous frameshift mutations in PTRH2 cause infantile-onset multisystem disease (IMNEPD); PTRH2 is highly expressed in developing brain, is a key determinant of cell survival during tissue development, and is linked to the mTOR pathway controlling cell size, demonstrated in mutant mice and patient fibroblasts.\",\n      \"method\": \"Whole-exome sequencing, Sanger sequencing, mutant mouse analysis, patient fibroblast functional studies, mTOR pathway assays\",\n      \"journal\": \"Annals of clinical and translational neurology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — human genetics plus functional validation in mouse and patient cells, mTOR link from cell-based assays, single study\",\n      \"pmids\": [\"25574476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PTRH2/Bit1 physically interacts with FAK protein; Bit1 knockdown in esophageal squamous cell carcinoma cells decreased FAK and paxillin expression at both mRNA and protein levels, identifying the FAK-paxillin pathway as a downstream effector of Bit1 in regulating cell migration and invasion.\",\n      \"method\": \"Co-immunoprecipitation (Bit1-FAK interaction), shRNA knockdown, gene microarray, Western blot, qRT-PCR, xenograft model\",\n      \"journal\": \"Molecular cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus downstream pathway validation by multiple methods, single lab\",\n      \"pmids\": [\"26956728\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PTRH2/Bit1 inhibits EMT in lung cancer by upregulating E-cadherin transcription through the AES co-activator, which blocks TLE1-mediated repression of the E-cadherin promoter; Bit1 decreases TLE1 occupancy at the E-cadherin promoter as shown by chromatin immunoprecipitation.\",\n      \"method\": \"siRNA/shRNA knockdown, ectopic overexpression, qRT-PCR, luciferase reporter assay, chromatin immunoprecipitation (ChIP), in vivo experimental metastasis model\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — ChIP assay directly demonstrating promoter occupancy, reporter assay, rescue experiments, in vivo validation; multiple orthogonal methods in single lab\",\n      \"pmids\": [\"27655370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PTRH2 associates in a complex with α7β1 integrin at the sarcolemma in normal skeletal muscle; PTRH2 expression is decreased in α7 integrin null muscle, and Ptrh2 knockout mouse muscle recapitulates progressive muscular dystrophy-like pathology.\",\n      \"method\": \"Co-immunoprecipitation (Ptrh2-α7β1 integrin complex), immunofluorescence, muscle histology (H&E, creatine kinase assay, fibrosis staining), Ptrh2 KO and α7 integrin KO mouse comparison\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP for complex, KO mouse with defined muscle phenotype, cross-validation with α7 integrin KO; single lab\",\n      \"pmids\": [\"28175314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Loss of PTRH2 specifically in Purkinje cells leads to reduced ribosomal protein S6 levels (a readout of mTOR pathway activity), PC atrophy with stunted dendrites, and progressive PC loss, establishing a cell-autonomous requirement for PTRH2 in PC maturation and survival via the mTOR pathway.\",\n      \"method\": \"PC-specific Ptrh2 conditional knockout mouse (Ptrh2ΔPC), cerebellar histology, gait/ataxia behavioral assays, immunostaining for S6 and PC markers\",\n      \"journal\": \"Cerebellum (London, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific genetic KO with defined cellular and molecular phenotype, single lab\",\n      \"pmids\": [\"36219306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Mitochondrial PTRH2 interacts with the deubiquitinase TRABID and the respiratory complex I subunit mt-ND5; PTRH2 regulates TRABID's ability to deubiquitylate mt-ND5 — in the absence of PTRH2, TRABID aberrantly deubiquitylates mt-ND5, increasing its stability, which promotes complex I activity, elevated ATP production, and mitochondrial Ca2+ overload under stress conditions. Re-expression of mitochondrial PTRH2 blocks TRABID DUB activity toward mt-ND5, leading to mt-ND5 polyubiquitylation and proteasomal degradation.\",\n      \"method\": \"Co-immunoprecipitation/mass spectrometry proteomics, CRISPR/Cas9 knockout, re-expression rescue, ubiquitylation assays, complex I activity assay, ATP production measurement, mitochondrial Ca2+ imaging, PTRH2 KO mouse immunostaining\",\n      \"journal\": \"PNAS nexus\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — IP/MS interactome, ubiquitylation assays, enzymatic activity measurements, genetic KO with rescue, in vivo mouse confirmation; multiple orthogonal methods in single study\",\n      \"pmids\": [\"40496187\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PTRH2 interacts with MFN1/2 (mitofusins) and interferes with MFN dimerization, thereby suppressing mitochondrial fusion; disease-associated PTRH2 truncation mutants (A90fs, W108*) show enhanced binding to MFN1/2, causing mitochondrial fragmentation, perinuclear aggregation via FKBP8 recruitment, and impaired mitophagy.\",\n      \"method\": \"Gain-of-function screening, co-immunoprecipitation, TurboID proximity labeling, site-directed mutagenesis of PTRH2 disease mutants, CRISPR/Cas9 KO, confocal microscopy of mitochondrial morphology, mito-Keima mitophagy assay, ATP/membrane potential/ROS assays\",\n      \"journal\": \"Molecular medicine (Cambridge, Mass.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — multiple orthogonal methods (Co-IP, proximity labeling, mutagenesis, live imaging, functional assays), single lab but comprehensive mechanistic dissection\",\n      \"pmids\": [\"41807994\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In EGFR-TKI-sensitive lung cancer cells, TKI treatment triggers cytosolic release of mitochondrial outer membrane-associated PTRH2/Bit1 prior to cytochrome C release and independently of full MOMP; released Bit1 forms a complex with AES in the cytosol, causing nuclear exclusion and sequestration of TLE1, thereby activating apoptosis.\",\n      \"method\": \"Subcellular fractionation, viability and apoptosis assays, siRNA/shRNA knockdown, ectopic overexpression, RNA-sequencing of TLE1-regulated genes, drug-tolerant persister cell models\",\n      \"journal\": \"Anticancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — fractionation with functional readout, epistasis via genetic manipulation, transcriptomic characterization; single lab\",\n      \"pmids\": [\"41895783\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Newcastle disease virus (NDV) infection promotes translocation of PTRH2/Bit1 from mitochondria to cytoplasm in tumor cells, mirroring suspension-induced anoikis; overexpression of Bit1 in tumor cells accelerated NDV-mediated inhibition of melanoma metastasis and growth in vivo.\",\n      \"method\": \"Subcellular fractionation, immunofluorescence localization, Bit1 overexpression in vivo mouse melanoma model, viral infection assays\",\n      \"journal\": \"Virologica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — fractionation demonstrating translocation, in vivo overexpression with functional metastasis readout; single lab\",\n      \"pmids\": [\"41130364\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PTRH2/Bit1 is a mitochondrial protein with peptidyl-tRNA hydrolase activity that serves as a multifunctional integrin effector: in adherent cells it promotes survival via NF-κB/Bcl-2 and suppresses ERK signaling from the Golgi; upon loss of cell attachment or apoptotic stimuli it is released from mitochondria (facilitated by PKD-mediated phosphorylation of Ser5/Ser87) into the cytoplasm where it complexes with AES to drive caspase-independent apoptosis and counteracts TLE1-mediated survival; within mitochondria it regulates metabolic homeostasis by controlling the deubiquitinase TRABID's activity toward the complex I subunit mt-ND5 and suppresses mitochondrial fusion by interfering with MFN1/2 dimerization, with disease-causing truncation mutants causing mitochondrial fragmentation and Ca2+ overload.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PTRH2 (Bit1) is a mitochondrial protein that functions as an integrin-coupled switch governing the balance between cell survival and anoikis during tissue development and homeostasis [#0, #2]. Upon loss of cell attachment or apoptotic stress, it is released from mitochondria into the cytoplasm—a step driven by PKD phosphorylation of Ser5/Ser87 and antagonized by integrin signaling—where it complexes with the Groucho/TLE protein AES to drive caspase-independent apoptosis [#0, #1]. The Bit1–AES module reciprocally controls TLE1: cytoplasmic Bit1 sequesters TLE1 away from the nucleus to relieve TLE1-mediated transcriptional repression, including derepression of the E-cadherin promoter to suppress epithelial–mesenchymal transition [#6, #10]. In adherent cells, PTRH2 instead promotes survival through a FAK/PI3K/AKT–dependent NF-κB axis that drives Bcl-2 transcription, and it acts as a Golgi-localized negative regulator of ERK-MAPK signaling [#3, #5, #2]. Within mitochondria, PTRH2 regulates metabolic and morphological homeostasis: it restrains the deubiquitinase TRABID to promote ubiquitin-dependent turnover of the complex I subunit mt-ND5, limiting complex I activity, ATP output, and Ca2+ overload, and it binds mitofusins MFN1/2 to block their dimerization and suppress mitochondrial fusion [#13, #14]. These activities underlie its developmental roles in skeletal myogenesis and muscle integrity, where it associates with α7β1 integrin at the sarcolemma, and in cerebellar Purkinje cell maturation via the mTOR pathway [#7, #11, #12]. Homozygous frameshift mutations in PTRH2 cause infantile-onset multisystem neurologic, endocrine, and pancreatic disease (IMNEPD), and disease-associated truncation mutants show enhanced MFN binding, mitochondrial fragmentation, and impaired mitophagy [#8, #14].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established PTRH2/Bit1 as a mitochondrially-sequestered apoptotic effector, answering how cells couple loss of integrin-mediated attachment to a death signal.\",\n      \"evidence\": \"Subcellular fractionation, reciprocal Co-IP with AES, gain/loss-of-function apoptosis assays in cell lines\",\n      \"pmids\": [\"15006356\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the molecular trigger for mitochondrial release\", \"Mechanism by which the Bit1-AES complex executes caspase-independent death unresolved\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identified the regulatory mechanism for Bit1 mitochondrial release, linking integrin status to PKD-mediated phosphorylation of the localization sequence.\",\n      \"evidence\": \"In vitro phosphorylation, site-directed mutagenesis of Ser5/Ser87, PKD inhibitors and siRNA in cell lines\",\n      \"pmids\": [\"18703509\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how Ser5 phosphorylation physically destabilizes mitochondrial retention\", \"Other potential regulatory kinases not excluded\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Placed Bit1 genetically upstream of ERK in anoikis signaling, defining it as a negative regulator of ERK with phosphatase-modulating activity.\",\n      \"evidence\": \"Conditional Ptrh2 KO mouse, MEF ERK phosphorylation and phosphatase assays, ERK knockdown epistasis\",\n      \"pmids\": [\"18218778\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct ERK phosphatase substrate/target not identified\", \"Connection between mitochondrial pool and ERK regulation unclear\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstrated a second subcellular pool of Bit1 at the Golgi acting as a brake on ERK-MAPK and stress resistance, broadening its role beyond mitochondria.\",\n      \"evidence\": \"Proteomic analysis of ER/membrane microdomains, chimeric construct and siRNA perturbation, ERK and stress assays\",\n      \"pmids\": [\"20197408\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; mechanism of Golgi ERK suppression not biochemically defined\", \"Relationship between Golgi and mitochondrial functions unresolved\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Revealed the pro-survival face of Bit1 in adherent cells, showing it drives Bcl-2 via FAK/PI3K/AKT-dependent NF-κB activation.\",\n      \"evidence\": \"shRNA knockdown with rescue, caspase/TUNEL assays, Bcl-2 readouts, FAK/PI3K/AKT inhibitors\",\n      \"pmids\": [\"21383007\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct molecular link from Bit1 to the NF-κB module not defined\", \"Single-lab pathway dissection\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identified βA3/A1-crystallin as a trafficking factor required to deliver Bit1 to the Golgi, controlling its anoikis competence in astrocytes.\",\n      \"evidence\": \"Anoikis assays, immunofluorescence localization, Cryba1 mutant (Nuc1) rat model\",\n      \"pmids\": [\"21993393\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Trafficking mechanism and direct interaction not characterized\", \"Generality beyond astrocytes untested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Defined a reciprocal antagonism between Bit1 and TLE1, explaining how survival signals restrain the apoptotic Bit1-AES complex.\",\n      \"evidence\": \"TLE1 overexpression/knockdown, Co-IP for Bit1-AES, fractionation, apoptosis assays\",\n      \"pmids\": [\"22952044\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and direct vs indirect AES competition not resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Linked PTRH2 to developmental control of skeletal myogenesis via a Bcl-2/caspase axis, showing non-apoptotic caspase signaling regulates differentiation timing.\",\n      \"evidence\": \"Ptrh2 KO mouse, C2C12 manipulation, caspase assays, Bcl-2 rescue, muscle histology\",\n      \"pmids\": [\"25770104\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular target by which Bit1 controls Bcl-2 in myoblasts not defined\", \"Mitochondrial vs cytoplasmic pool contribution unclear\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Connected PTRH2 loss-of-function to a human Mendelian multisystem disease (IMNEPD) and to mTOR-dependent control of cell size.\",\n      \"evidence\": \"Whole-exome sequencing, mutant mouse and patient fibroblast functional studies, mTOR assays\",\n      \"pmids\": [\"25574476\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanistic link between peptidyl-tRNA hydrolase activity and mTOR not established\", \"Single study\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified Bit1 as a transcriptional suppressor of EMT through AES-mediated derepression of the E-cadherin promoter, integrating the AES/TLE1 axis with cancer cell behavior.\",\n      \"evidence\": \"ChIP for TLE1 promoter occupancy, luciferase reporter, knockdown/overexpression, in vivo metastasis model\",\n      \"pmids\": [\"27655370\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether nuclear Bit1 or cytoplasmic sequestration drives derepression not fully separated\", \"Range of TLE1 target genes not surveyed\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Showed a physical Bit1-FAK interaction feeding into the FAK-paxillin migration/invasion pathway, complementing the FAK-dependent survival role.\",\n      \"evidence\": \"Co-IP, shRNA knockdown, microarray, qRT-PCR/Western, xenograft in ESCC cells\",\n      \"pmids\": [\"26956728\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct vs scaffold-mediated FAK binding not resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed PTRH2 in a sarcolemmal complex with α7β1 integrin, tying its muscle phenotype to integrin biology in vivo.\",\n      \"evidence\": \"Co-IP, immunofluorescence, muscle histology, Ptrh2 KO vs α7 integrin KO mouse comparison\",\n      \"pmids\": [\"28175314\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct binding partner within the integrin complex not mapped\", \"Functional consequence of the complex mechanistically undefined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established a cell-autonomous requirement for PTRH2 in cerebellar Purkinje cell maturation and survival via mTOR/S6 signaling, refining the neurological basis of IMNEPD.\",\n      \"evidence\": \"PC-specific conditional KO mouse, cerebellar histology, ataxia behavior, S6 immunostaining\",\n      \"pmids\": [\"36219306\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link from PTRH2 to mTOR/S6 in neurons not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined a mitochondrial metabolic role for PTRH2 as a regulator of the TRABID deubiquitinase, controlling mt-ND5 stability, complex I activity, and Ca2+ homeostasis.\",\n      \"evidence\": \"IP/MS interactome, CRISPR KO and rescue, ubiquitylation assays, complex I and ATP assays, Ca2+ imaging, KO mouse\",\n      \"pmids\": [\"40496187\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How PTRH2 mechanistically inhibits TRABID DUB activity unresolved\", \"Role of catalytic peptidyl-tRNA hydrolase activity in this function untested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Identified PTRH2 as a suppressor of mitochondrial fusion via MFN1/2 binding, and showed disease truncation mutants gain enhanced MFN binding causing fragmentation and impaired mitophagy.\",\n      \"evidence\": \"GoF screening, Co-IP, TurboID, disease-mutant mutagenesis, CRISPR KO, confocal morphology, mito-Keima mitophagy and functional assays\",\n      \"pmids\": [\"41807994\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of MFN dimerization interference not solved\", \"How truncation enhances MFN binding mechanistically unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended the anoikis/apoptosis mechanism to therapeutic contexts, showing EGFR-TKI and oncolytic virus trigger Bit1 cytosolic release and AES/TLE1-dependent apoptosis.\",\n      \"evidence\": \"Fractionation, viability/apoptosis assays, knockdown/overexpression, RNA-seq of TLE1 targets, drug-tolerant persister and in vivo melanoma models\",\n      \"pmids\": [\"41895783\", \"41130364\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How TKI/viral stress signals to Bit1 release mechanistically unknown\", \"Relationship to canonical MOMP/cytochrome C release only partially defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PTRH2's enzymatic peptidyl-tRNA hydrolase activity relates to its diverse signaling, mitochondrial metabolic, and morphological functions remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No discovery links catalytic activity to the integrin/anoikis, TRABID, or MFN functions\", \"Integration across mitochondrial, Golgi, and cytoplasmic pools lacks a unifying mechanism\", \"No structural model of substrate or partner complexes\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [13]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [13, 14]},\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [10, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 13, 14]},\n      {\"term_id\": \"GO:0005794\", \"supporting_discovery_ids\": [5, 4]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 15]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 1, 15]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 5]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [13]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [14]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [7, 12]}\n    ],\n    \"complexes\": [\n      \"Bit1-AES complex\",\n      \"α7β1 integrin complex\"\n    ],\n    \"partners\": [\n      \"AES\",\n      \"TLE1\",\n      \"FAK\",\n      \"TRABID\",\n      \"mt-ND5\",\n      \"MFN1\",\n      \"MFN2\",\n      \"ITGA7\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}