{"gene":"STARD7","run_date":"2026-06-10T07:46:42","timeline":{"discoveries":[{"year":2009,"finding":"StarD7 specifically catalyzes the transfer of phosphatidylcholine (PC) between lipid vesicles in vitro, and overexpression of StarD7-I (the isoform containing a mitochondrial-targeting sequence) increases intracellular transport of fluorescent PC to mitochondria. StarD7-I localizes to mitochondria (associated with the outer mitochondrial membrane by protease K protection assay) while StarD7-II is constitutively cytoplasmic.","method":"In vitro PC transfer assay with purified recombinant protein, fluorescent PC trafficking assay in HEPA-1 cells, protease K protection assay, overexpression and subcellular fractionation","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of PC transfer activity with purified protein, combined with cell-based fluorescent lipid trafficking and organelle fractionation; foundational mechanistic paper replicated by subsequent studies","pmids":["20042613"],"is_preprint":false},{"year":2018,"finding":"The mitochondrial inner membrane rhomboid protease PARL cleaves STARD7 during mitochondrial import, partitioning it between the cytosol and the mitochondrial intermembrane space (IMS). Negatively charged amino acids in STARD7 serve as a sorting signal for cytosolic release after PARL cleavage, while TIM23-mediated membrane insertion promotes mitochondrial IMS retention. Mitochondrial STARD7 is necessary and sufficient for PC accumulation in the inner membrane and for maintenance of respiration and cristae morphogenesis.","method":"PARL knockout cells, co-immunoprecipitation, subcellular fractionation, mitochondrial import assays, site-directed mutagenesis of sorting signal, rescue experiments with STARD7 variants","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal genetic and biochemical dissection of PARL cleavage and sorting signal using multiple orthogonal methods; replicated and extended in 2023 Nature Cell Biology paper","pmids":["29301859"],"is_preprint":false},{"year":2018,"finding":"StarD7's START domain harbors a shared binding site for both phosphatidylcholine (PC) and ceramide, as demonstrated by photoaffinity labeling with a clickable ceramide analog (pacCer) and site-directed mutagenesis. StarD7 lacks robust ceramide transfer activity in vitro, but ceramide specifically inhibits StarD7's ability to shuttle PC between model membranes.","method":"Photoaffinity labeling with bifunctional ceramide analog (pacCer), site-directed mutagenesis of START domain, in vitro PC transfer assay with ceramide competition","journal":"Journal of lipid research","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with mutagenesis and photoaffinity labeling in a single study; identifies shared binding site for PC and ceramide","pmids":["29343537"],"is_preprint":false},{"year":2016,"finding":"StarD7 knockout (via CRISPR/Cas9n) and knockdown in HEPA-1 cells reduces mitochondrial PC content, impairs oxygen consumption rate and mitochondrial complex activities, lowers ATP levels, reduces MTCO1 (complex IV subunit) protein without affecting its mRNA, disrupts mitochondrial supercomplex formation, and causes disorganized cristae structure. Re-expression of StarD7-I rescues MTCO1 levels and mitochondrial abnormalities.","method":"siRNA knockdown, CRISPR/Cas9n knockout, real-time respirometry (Seahorse), mitochondrial complex activity assay, phospholipid analysis, rescue by overexpression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with rescue, multiple orthogonal readouts of mitochondrial function; independently replicated by multiple labs","pmids":["27694445"],"is_preprint":false},{"year":2017,"finding":"StarD7-I contains a transmembrane (TM) domain C-terminal to its mitochondrial-targeting signal that anchors the mature protein to the outer leaflet of the outer mitochondrial membrane (OMM). The precursor is cleaved between Met76–Ala77 and Ala77–Ala78 in the TM domain. A truncated StarD7 lacking the TM domain localizes to the mitochondrial matrix and cannot rescue mitochondrial complex formation or PC content defects in StarD7-KO cells, unlike full-length StarD7-I.","method":"Truncation mutants, immunofluorescence and subcellular fractionation in HEPA-1 and HepG2 cells, N-terminal sequencing of cleavage site, rescue of StarD7-KO cells with wild-type vs. truncated forms","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Moderate — domain mutagenesis with precise cleavage site mapping and functional rescue experiments; single lab but multiple orthogonal methods","pmids":["28821867"],"is_preprint":false},{"year":2017,"finding":"Stard7 deficiency in lung bronchiolar epithelial cells (BEAS-2B knockdown and Stard7epi∆/∆ mice) causes altered mitochondrial size and membrane organization, decreased aerobic respiration, increased oxidant stress, and mitochondrial DNA damage, which in turn disrupts epithelial barrier integrity and function. These defects are rescued by targeting Stard7 to mitochondria or treating cells with a mitochondrial-targeted antioxidant.","method":"siRNA knockdown in BEAS-2B, conditional epithelial-specific KO mice, respirometry, ROS assays, mtDNA damage assay, barrier permeability assay, rescue with mitochondria-targeted Stard7 and MitoTEMPO","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro and in vivo KO with mechanistic rescue linking PC transfer to mitochondrial function to barrier integrity","pmids":["28401922"],"is_preprint":false},{"year":2023,"finding":"STARD7 is a critical factor for intracellular coenzyme Q (CoQ) transport from mitochondria to the plasma membrane and suppressor of ferroptosis. PARL-mediated cleavage of STARD7 partitions it between the mitochondrial IMS (where it supports CoQ synthesis and cristae morphogenesis) and the cytosol (where it transports CoQ to the plasma membrane to limit lipid peroxidation). A CoQ variant competes with PC for binding to purified STARD7 in vitro. Overexpression of cytosolic STARD7 increases ferroptosis resistance but reduces mitochondrial CoQ and respiratory growth.","method":"PARL and STARD7 KO/rescue cells, in vitro competitive binding assay with purified STARD7 and CoQ/PC, ferroptosis assays (lipid peroxidation, cell viability), lipidomics, respirometry, STARD7 isoform overexpression","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of competitive binding, genetic dissection with isoform-specific rescue, multiple orthogonal functional readouts; high-impact peer-reviewed journal","pmids":["36658222"],"is_preprint":false},{"year":2011,"finding":"Recombinant StarD7 functions as a fusogenic protein: it accelerates lipid dilution between donor and acceptor liposomes via bilayer fusion (not monomeric lipid transport), as demonstrated by fluorescence de-quenching, FRET between labeled lipids, dynamic light scattering, and induction of multinuclear giant cell formation. Fusogenic activity depends on electrostatic interactions with the lipid-water interface and is favored by phosphatidylethanolamine.","method":"Fluorescence de-quenching assay, FRET-based lipid mixing assay, dynamic light scattering, multinuclear giant cell formation with recombinant protein, pH and salt modulation experiments","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro reconstitution with multiple biophysical methods in a single lab; fusogenic mechanism not extensively replicated","pmids":["22063720"],"is_preprint":false},{"year":2021,"finding":"StarD7.I overexpression in HTR-8/SVneo cells increases PC transport to mitochondria, alters mitochondrial morphology (increased fragmentation), and modulates fission/fusion proteins: Drp1 and Mfn2 are increased while Mfn1 is decreased. Mitochondrial fragmentation in StarD7.I-overexpressing cells occurs in a fission-dependent manner via Drp1 (established by dominant-negative Drp1-K38A, and phosphomimetic/non-phosphorylatable Drp1 mutants). StarD7 silencing decreases Mfn1 and Mfn2 without changing Drp1 and induces donut-shaped mitochondria.","method":"Stable overexpression of StarD7.I and StarD7.II isoforms, siRNA knockdown, transfection with Drp1 mutants (K38A, S637D, S637A), fluorescent PC analog transport assay, live-cell imaging, ROS measurement, mitochondrial membrane potential assay","journal":"Biochimica et biophysica acta. Molecular and cell biology of lipids","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isoform-specific overexpression with Drp1 mutant epistasis; single lab with multiple orthogonal methods","pmids":["34416390"],"is_preprint":false},{"year":2022,"finding":"StarD7 silencing in HTR-8/SVneo cells decreases connexin 43 (Cx43), integrin β1, and p-ERK1/2 expression, causes Golgi disruption and reduced ability to reorient the microtubule-organizing center, and impairs cell migration. Re-expression specifically of the cytosolic StarD7.II isoform (not the mitochondria-targeted StarD7.I) restores cell migration, ERK1/2, Cx43, and integrin β1 expression, defining a mitochondria-independent, ERK1/2/Cx43-dependent mechanism for StarD7 in cell motility.","method":"siRNA knockdown, stable isoform-specific re-expression (StarD7.I vs StarD7.II), wound healing and transwell migration assays, immunofluorescence for Golgi and MTOC, Western blot for signaling proteins","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isoform-specific rescue defines pathway; single lab with multiple cellular readouts","pmids":["36584213"],"is_preprint":false},{"year":2020,"finding":"In C2C12 myoblasts, PARL is not involved in StarD7 processing or maturation (unlike in HEK293 cells). StarD7 localizes to the cytosol, inner mitochondrial space, and outer leaflet of the OMM. siRNA knockdown of StarD7 impairs myogenic differentiation and reduces expression of myomaker, myomerger, and PGC-1α; these defects (including reduced mitochondrial PC and oxygen consumption) are fully rescued by re-expression of StarD7 in knockout C2C12 cells.","method":"siRNA knockdown, CRISPR KO, rescue by re-expression, immunofluorescence, immuno-electron microscopy, oxygen consumption assay, differentiation markers by Western blot/qPCR","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO with rescue in two cell types; identifies cell-type-specific difference in PARL processing and required role in myogenesis; single lab","pmids":["32071354"],"is_preprint":false},{"year":2023,"finding":"StarD7 deficiency in C2C12 myoblasts increases mitophagy flux: knockdown cells accumulate LC3B-II and BNIP3 in mitochondria-enriched fractions, accumulate autophagolysosomal vesicles, and show enhanced mitochondria delivery to lysosomes (by live-cell imaging with mitochondria-targeted mKeima). StarD7 reconstitution restores LC3B-II levels in mitochondrial fractions.","method":"siRNA knockdown, live-cell imaging with mitochondria-targeted mKeima, mitochondrial fractionation, LC3B-II and BNIP3 Western blot, lysosomal vesicle quantification, StarD7 rescue","journal":"The FEBS journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — live-cell imaging combined with biochemical fractionation and rescue; single lab","pmids":["37846201"],"is_preprint":false},{"year":2016,"finding":"StarD7 knockdown in HepG2 cells induces ER stress (increased IRE1α, calnexin, GRP78/BiP, PERK, p-eIF2α), alters mitochondria and ER morphology, increases ROS generation, and reduces cell viability after H2O2 exposure. Knockdown also causes p53 protein degradation and increases heme oxygenase-1 and catalase expression and catalase enzymatic activity.","method":"siRNA knockdown in HepG2 cells, Western blot for ER stress markers, ROS assay, cell viability assay, electron microscopy of organelle morphology, catalase activity assay","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — KD with multiple pathway readouts linking StarD7 to ER stress and redox homeostasis; single lab, single method per readout","pmids":["27554972"],"is_preprint":false},{"year":2023,"finding":"SUMO1 degrader HB007 reduces StarD7 mRNA and protein in colon cancer cells through deSUMOylation and degradation of the transcription factor TCF4, which transcriptionally activates StarD7. StarD7 knockout identified as critical for HB007 anticancer activity by genome-wide CRISPR screen.","method":"Genome-wide CRISPR-Cas9 KO screen, SUMO1 degrader treatment, TCF4 deSUMOylation assay, mRNA and protein quantification in 3D organoids and PDX models","journal":"Molecular carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — CRISPR screen plus mechanistic follow-up with TCF4 deSUMOylation linking TCF4 to StarD7 transcription; single lab","pmids":["37191369"],"is_preprint":false},{"year":2004,"finding":"Recombinant StarD7 protein forms stable Gibbs and Langmuir monolayers at the air-buffer interface and penetrates phospholipid monolayers, showing preference for phosphatidylserine, cholesterol, and phosphatidylglycerol, demonstrating direct protein-lipid interaction at membrane interfaces.","method":"Langmuir monolayer technique, surface pressure measurements, Gibbs film analysis with recombinant StarD7","journal":"Biochemical and biophysical research communications","confidence":"Low","confidence_rationale":"Tier 3 / Weak — biophysical characterization with recombinant protein; single method, single lab, no in-cell functional consequence demonstrated","pmids":["14715263"],"is_preprint":false},{"year":2025,"finding":"Loss of STARD7 in breast cancer cells leads to accumulation of carnitine derivatives and S-Adenosyl-L-methionine (SAM), which increases H3K27 trimethylation on promoters of cell cycle genes, causing cell cycle arrest. STARD7 deficiency also impairs EGFR trafficking to lysosomes, disrupting EGFR signaling in triple-negative breast cancer cells.","method":"STARD7 KO in breast cancer cell lines, metabolomics, ChIP-seq for H3K27me3, cell cycle analysis, EGFR trafficking assay, ERα-dependent proliferation assay","journal":"Advanced science","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO with metabolomics and ChIP-seq linking mitochondrial PC transfer to epigenomic regulation of cell cycle; single lab, multiple orthogonal methods","pmids":["40443279"],"is_preprint":false},{"year":2026,"finding":"Muscle-specific STARD7 knockout mice show reduced endurance exercise capacity and decreased mitochondrial PC, cardiolipin, and coenzyme Q in soleus muscle, with disorganized cristae but intact respiratory chain complexes. An in vitro binding assay indicates STARD7 preferentially transfers linoleic acid-containing PC species required for cardiolipin remodeling.","method":"Muscle-specific knockout mice, targeted lipidomics, in vitro lipid binding/transfer assay, electron microscopy, respirometry, RNA-seq, fiber-type analysis","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo KO combined with in vitro binding assay and lipidomics; single lab, multiple orthogonal methods","pmids":["41989333"],"is_preprint":false}],"current_model":"STARD7 is a cytosolic START-domain lipid transfer protein that exists as two isoforms (StarD7-I with a mitochondrial-targeting sequence and StarD7-II lacking it); the rhomboid protease PARL cleaves StarD7-I during mitochondrial import, partitioning it between the mitochondrial intermembrane space—where it maintains phosphatidylcholine (PC) content in the inner membrane, supports respiratory complex assembly, coenzyme Q synthesis, and cristae morphogenesis—and the cytosol, where it transports coenzyme Q to the plasma membrane to suppress ferroptosis and also regulates cell migration via an ERK1/2/Cx43 mechanism; the START domain binds both PC and ceramide at a shared site, with ceramide competing with and inhibiting PC transfer activity."},"narrative":{"mechanistic_narrative":"STARD7 is a START-domain lipid transfer protein that controls mitochondrial phospholipid supply and intracellular lipid distribution, thereby governing respiratory function, cristae architecture, and redox homeostasis [PMID:20042613, PMID:27694445]. Its START domain catalyzes phosphatidylcholine (PC) transfer between membranes in vitro, and this same site binds ceramide and a coenzyme Q (CoQ) variant, both of which compete with PC, establishing a single ligand pocket whose occupancy tunes transfer activity [PMID:20042613, PMID:29343537, PMID:36658222]. The protein is expressed as two isoforms: StarD7-I carries an N-terminal mitochondrial-targeting sequence and a transmembrane anchor in the outer mitochondrial membrane, while StarD7-II is constitutively cytosolic [PMID:20042613, PMID:28821867]. During mitochondrial import the inner-membrane rhomboid protease PARL cleaves STARD7, and an acidic sorting signal partitions the cleaved protein between the intermembrane space and the cytosol [PMID:29301859]. Intramitochondrial STARD7 is necessary and sufficient to maintain inner-membrane PC, respiratory complex and supercomplex assembly, and cristae morphogenesis [PMID:29301859, PMID:27694445], whereas the cytosolic pool transports CoQ to the plasma membrane to limit lipid peroxidation and suppress ferroptosis [PMID:36658222]. Loss of STARD7 impairs oxidative phosphorylation and disrupts epithelial barrier integrity through mitochondrial oxidant stress and mtDNA damage, is required for myogenic differentiation, and restrains mitophagy flux [PMID:28401922, PMID:32071354, PMID:37846201]. Beyond mitochondria, the cytosolic isoform drives cell migration through an ERK1/2/connexin-43/integrin-β1 mechanism, and STARD7 supports cancer cell proliferation by linking mitochondrial lipid metabolism to metabolite-driven H3K27me3 deposition on cell-cycle gene promoters and to EGFR trafficking [PMID:36584213, PMID:40443279].","teleology":[{"year":2004,"claim":"Before any cellular function was known, it was unclear whether STARD7 interacts directly with lipid membranes; biophysical analysis established direct protein-lipid interaction at interfaces.","evidence":"Langmuir/Gibbs monolayer surface-pressure measurements with recombinant protein","pmids":["14715263"],"confidence":"Low","gaps":["Single biophysical method with no in-cell functional consequence demonstrated","Lipid preferences (PS, cholesterol, PG) at monolayers do not establish a physiological transfer substrate","No isoform or domain resolution"]},{"year":2009,"claim":"The molecular activity was defined by showing STARD7 is a PC-specific transfer protein, and that the StarD7-I isoform directs PC to mitochondria while StarD7-II is cytosolic.","evidence":"In vitro PC transfer assay with purified protein, fluorescent PC trafficking, protease K protection and fractionation in HEPA-1 cells","pmids":["20042613"],"confidence":"High","gaps":["Did not resolve how the precursor is processed during import","Mechanistic link between PC transfer and downstream mitochondrial function not yet established"]},{"year":2011,"claim":"An alternative mechanism was tested: whether STARD7 acts by membrane fusion rather than monomeric lipid carriage, addressing how it moves lipid between bilayers.","evidence":"Fluorescence de-quenching, FRET lipid mixing, dynamic light scattering, multinuclear giant cell formation with recombinant protein","pmids":["22063720"],"confidence":"Medium","gaps":["Fusogenic mechanism not extensively replicated and not reconciled with monomeric transfer model","Physiological relevance of fusion activity in cells not demonstrated"]},{"year":2016,"claim":"Causal linkage between STARD7 PC transfer and mitochondrial bioenergetics was established by genetic loss-of-function with rescue, and a parallel role in ER stress/redox homeostasis was reported.","evidence":"CRISPR/Cas9n KO and siRNA in HEPA-1 with respirometry, complex activity and rescue (idx 3); siRNA in HepG2 with ER-stress and ROS readouts (idx 12)","pmids":["27694445","27554972"],"confidence":"High","gaps":["How reduced PC selectively destabilizes MTCO1/supercomplexes not mechanistically resolved","ER-stress and p53/catalase changes (idx 12) rest on single-method readouts per endpoint"]},{"year":2017,"claim":"The targeting determinants and physiological output were refined: a transmembrane anchor positions mature STARD7 on the OMM and is required for function, and epithelial loss links mitochondrial dysfunction to barrier integrity.","evidence":"Truncation mutants, N-terminal cleavage-site sequencing and rescue (idx 4); BEAS-2B knockdown and epithelial-specific KO mice with antioxidant rescue (idx 5)","pmids":["28821867","28401922"],"confidence":"High","gaps":["Protease responsible for the TM-domain cleavage not identified in idx 4","Whether barrier defects are fully attributable to PC transfer versus secondary oxidant stress not separated"]},{"year":2018,"claim":"The import/sorting logic and the ligand-binding basis of regulation were resolved: PARL cleavage plus an acidic sorting signal partitions STARD7 between IMS and cytosol, and the START domain uses a shared PC/ceramide site where ceramide inhibits PC transfer.","evidence":"PARL KO cells, import assays, sorting-signal mutagenesis and rescue (idx 1); pacCer photoaffinity labeling, START-domain mutagenesis and ceramide-competition transfer assay (idx 2)","pmids":["29301859","29343537"],"confidence":"High","gaps":["Whether ceramide regulation of PC transfer operates in cells, not only in vitro","Structural model of the shared binding pocket not determined"]},{"year":2020,"claim":"Tissue-context dependence and a developmental requirement were established: PARL is dispensable for STARD7 processing in myoblasts, and STARD7 is required for myogenic differentiation via mitochondrial PC/respiration and PGC-1α.","evidence":"siRNA, CRISPR KO and rescue in C2C12, immuno-EM, respirometry, differentiation-marker analysis","pmids":["32071354"],"confidence":"Medium","gaps":["Alternative processing protease in C2C12 not identified","Single lab; cell-type specificity of PARL independence not generalized"]},{"year":2021,"claim":"A regulatory connection to mitochondrial dynamics was tested, showing isoform-specific STARD7-I overexpression drives Drp1-dependent fragmentation and alters fusion proteins.","evidence":"Isoform-specific stable overexpression and siRNA in HTR-8/SVneo, Drp1 mutant epistasis, fluorescent PC transport and live-cell imaging","pmids":["34416390"],"confidence":"Medium","gaps":["Whether fission changes are a direct lipid effect or secondary to bioenergetic stress not resolved","Single cell type, overexpression-based"]},{"year":2022,"claim":"A mitochondria-independent function was defined: cytosolic StarD7.II drives cell migration through ERK1/2/Cx43/integrin-β1 signaling and MTOC/Golgi reorientation.","evidence":"siRNA with isoform-specific re-expression (StarD7.I vs II), migration assays, immunofluorescence and signaling Western blots in HTR-8/SVneo","pmids":["36584213"],"confidence":"Medium","gaps":["How cytosolic STARD7 lipid handling connects mechanistically to ERK1/2 activation not established","Single lab, single cell type"]},{"year":2023,"claim":"The cytosolic pool was assigned a distinct cargo and physiological output—CoQ transport to the plasma membrane to suppress ferroptosis—while additional studies linked STARD7 to mitophagy control and to transcriptional regulation by TCF4.","evidence":"PARL/STARD7 KO-rescue, in vitro CoQ/PC competitive binding, ferroptosis and lipidomics assays (idx 6); mKeima mitophagy imaging in C2C12 (idx 11); CRISPR screen and TCF4 deSUMOylation in colon cancer (idx 13)","pmids":["36658222","37846201","37191369"],"confidence":"High","gaps":["How a single START pocket coordinates PC, ceramide and CoQ binding in vivo not structurally resolved","Mitophagy and TCF4-transcription findings (Medium) are single-lab"]},{"year":2025,"claim":"STARD7 was linked to cancer cell proliferation through metabolic-epigenetic coupling and receptor trafficking, broadening its role beyond bioenergetics.","evidence":"STARD7 KO in breast cancer cells with metabolomics, H3K27me3 ChIP-seq, cell-cycle analysis and EGFR trafficking assays","pmids":["40443279"],"confidence":"Medium","gaps":["Causal chain from carnitine/SAM accumulation to H3K27me3 not fully dissected","Single lab; relationship between EGFR trafficking defect and lipid transfer unclear"]},{"year":2026,"claim":"An in vivo muscle requirement and a substrate-specificity refinement were established: STARD7 preferentially transfers linoleic-acid-containing PC supporting cardiolipin remodeling and endurance capacity.","evidence":"Muscle-specific KO mice with targeted lipidomics, in vitro binding/transfer assay, EM and respirometry","pmids":["41989333"],"confidence":"Medium","gaps":["Mechanism connecting PC species selectivity to cardiolipin remodeling enzymes not defined","Respiratory complexes intact despite cristae defects—uncoupling of phenotypes not explained"]},{"year":null,"claim":"A unified structural and regulatory model for how one START pocket selects among PC species, ceramide, and CoQ in different subcellular pools—and how isoform partitioning is controlled in a tissue-specific manner—remains open.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No high-resolution structure of the START domain with bound ligands","In vivo regulation of cytosol-versus-IMS partitioning beyond PARL not defined","No human Mendelian disease link established in the corpus"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[0,2,6,16]},{"term_id":"GO:0140104","term_label":"molecular carrier activity","supporting_discovery_ids":[0,6]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,1,3,4]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,1,9]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,3,6,16]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[6]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[11]}],"complexes":[],"partners":["PARL"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9NQZ5","full_name":"StAR-related lipid transfer protein 7, mitochondrial","aliases":["Gestational trophoblastic tumor protein 1","START domain-containing protein 7","StARD7"],"length_aa":370,"mass_kda":43.1,"function":"May play a protective role in mucosal tissues by preventing exaggerated allergic responses","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/Q9NQZ5/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/STARD7","classification":"Not Classified","n_dependent_lines":505,"n_total_lines":1208,"dependency_fraction":0.41804635761589404},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/STARD7","total_profiled":1310},"omim":[{"mim_id":"616712","title":"START DOMAIN-CONTAINING PROTEIN 7; STARD7","url":"https://www.omim.org/entry/616712"},{"mim_id":"607876","title":"EPILEPSY, FAMILIAL ADULT MYOCLONIC, 2; FAME2","url":"https://www.omim.org/entry/607876"},{"mim_id":"601068","title":"EPILEPSY, FAMILIAL ADULT MYOCLONIC, 1; FAME1","url":"https://www.omim.org/entry/601068"},{"mim_id":"104260","title":"ALPHA-2B-ADRENERGIC RECEPTOR; ADRA2B","url":"https://www.omim.org/entry/104260"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Mitochondria","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/STARD7"},"hgnc":{"alias_symbol":["GTT1"],"prev_symbol":[]},"alphafold":{"accession":"Q9NQZ5","domains":[{"cath_id":"3.30.530.20","chopping":"93-111_141-325","consensus_level":"high","plddt":90.4172,"start":93,"end":325},{"cath_id":"1.10.287","chopping":"26-81","consensus_level":"high","plddt":69.8821,"start":26,"end":81}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQZ5","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQZ5-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NQZ5-F1-predicted_aligned_error_v6.png","plddt_mean":74.56},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=STARD7","jax_strain_url":"https://www.jax.org/strain/search?query=STARD7"},"sequence":{"accession":"Q9NQZ5","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NQZ5.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NQZ5/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NQZ5"}},"corpus_meta":[{"pmid":"36658222","id":"PMC_36658222","title":"Mitochondria regulate intracellular coenzyme Q transport and ferroptotic resistance via STARD7.","date":"2023","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/36658222","citation_count":131,"is_preprint":false},{"pmid":"31664034","id":"PMC_31664034","title":"Intronic ATTTC repeat expansions in STARD7 in familial adult myoclonic epilepsy linked to chromosome 2.","date":"2019","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/31664034","citation_count":110,"is_preprint":false},{"pmid":"20042613","id":"PMC_20042613","title":"StarD7 mediates the intracellular trafficking of phosphatidylcholine to mitochondria.","date":"2009","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/20042613","citation_count":90,"is_preprint":false},{"pmid":"29301859","id":"PMC_29301859","title":"PARL partitions the lipid transfer protein STARD7 between the cytosol and mitochondria.","date":"2018","source":"The EMBO 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chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/27694445","citation_count":42,"is_preprint":false},{"pmid":"15013637","id":"PMC_15013637","title":"GTT1/StarD7, a novel phosphatidylcholine transfer protein-like highly expressed in gestational trophoblastic tumour: cloning and characterization.","date":"2004","source":"Placenta","url":"https://pubmed.ncbi.nlm.nih.gov/15013637","citation_count":31,"is_preprint":false},{"pmid":"23507753","id":"PMC_23507753","title":"The Lipid Transfer Protein StarD7: Structure, Function, and Regulation.","date":"2013","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/23507753","citation_count":31,"is_preprint":false},{"pmid":"12912890","id":"PMC_12912890","title":"Glucose uptake in Trichoderma harzianum: role of gtt1.","date":"2003","source":"Eukaryotic cell","url":"https://pubmed.ncbi.nlm.nih.gov/12912890","citation_count":30,"is_preprint":false},{"pmid":"18378304","id":"PMC_18378304","title":"Expression and localization of StarD7 in trophoblast cells.","date":"2008","source":"Placenta","url":"https://pubmed.ncbi.nlm.nih.gov/18378304","citation_count":27,"is_preprint":false},{"pmid":"27554972","id":"PMC_27554972","title":"Suppression of StarD7 promotes endoplasmic reticulum stress and induces ROS production.","date":"2016","source":"Free radical biology & medicine","url":"https://pubmed.ncbi.nlm.nih.gov/27554972","citation_count":26,"is_preprint":false},{"pmid":"28821867","id":"PMC_28821867","title":"Identification of the N-terminal transmembrane domain of StarD7 and its importance for mitochondrial outer membrane localization and phosphatidylcholine transfer.","date":"2017","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/28821867","citation_count":26,"is_preprint":false},{"pmid":"25980009","id":"PMC_25980009","title":"Haploinsufficiency for Stard7 is associated with enhanced allergic responses in lung and skin.","date":"2015","source":"Journal of immunology 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Molecular and cell biology of lipids","url":"https://pubmed.ncbi.nlm.nih.gov/34416390","citation_count":16,"is_preprint":false},{"pmid":"32071354","id":"PMC_32071354","title":"The phosphatidylcholine transfer protein StarD7 is important for myogenic differentiation in mouse myoblast C2C12 cells and human primary skeletal myoblasts.","date":"2020","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/32071354","citation_count":16,"is_preprint":false},{"pmid":"37191369","id":"PMC_37191369","title":"SUMO1 degrader induces ER stress and ROS accumulation through deSUMOylation of TCF4 and inhibition of its transcription of StarD7 in colon cancer.","date":"2023","source":"Molecular carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/37191369","citation_count":13,"is_preprint":false},{"pmid":"39576011","id":"PMC_39576011","title":"STARD7 maintains intestinal epithelial mitochondria architecture, barrier integrity, and protection from colitis.","date":"2024","source":"JCI insight","url":"https://pubmed.ncbi.nlm.nih.gov/39576011","citation_count":11,"is_preprint":false},{"pmid":"38670562","id":"PMC_38670562","title":"LncRNA STARD7-AS1 suppresses cervical cancer cell proliferation while promoting autophagy by regulating miR-31-5p/TXNIP axis to inactivate the mTOR signaling.","date":"2024","source":"Journal of gynecologic oncology","url":"https://pubmed.ncbi.nlm.nih.gov/38670562","citation_count":10,"is_preprint":false},{"pmid":"22063720","id":"PMC_22063720","title":"StarD7 behaves as a fusogenic protein in model and cell membrane bilayers.","date":"2011","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/22063720","citation_count":6,"is_preprint":false},{"pmid":"37846201","id":"PMC_37846201","title":"StarD7 deficiency switches on glycolysis and promotes mitophagy flux in C2C12 myoblasts.","date":"2023","source":"The FEBS journal","url":"https://pubmed.ncbi.nlm.nih.gov/37846201","citation_count":5,"is_preprint":false},{"pmid":"40443279","id":"PMC_40443279","title":"Loss of STARD7 Triggers Metabolic Reprogramming and Cell Cycle Arrest in Breast Cancer.","date":"2025","source":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","url":"https://pubmed.ncbi.nlm.nih.gov/40443279","citation_count":4,"is_preprint":false},{"pmid":"30315445","id":"PMC_30315445","title":"Hexosamine pathway regulates StarD7 expression in JEG-3 cells.","date":"2018","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/30315445","citation_count":2,"is_preprint":false},{"pmid":"36584213","id":"PMC_36584213","title":"StarD7 deficiency hinders cell motility through p-ERK1/2/Cx43 reduction.","date":"2022","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/36584213","citation_count":2,"is_preprint":false},{"pmid":"22898837","id":"PMC_22898837","title":"[Effect of StarD7 and Wnt/β-catenin signal pathway on the testosterone secretion stimulated by Annexin 5 in rat Leydig cells].","date":"2012","source":"Beijing da xue xue bao. Yi xue ban = Journal of Peking University. Health sciences","url":"https://pubmed.ncbi.nlm.nih.gov/22898837","citation_count":2,"is_preprint":false},{"pmid":"40685053","id":"PMC_40685053","title":"CircEGLN1 alleviates calcium oxalate-induced renal injury via miR-212-5p/STARD7 axis, offering a potential strategy for kidney stone prevention.","date":"2025","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/40685053","citation_count":0,"is_preprint":false},{"pmid":"41989333","id":"PMC_41989333","title":"Loss of STARD7 Impairs Mitochondrial Phospholipid Homeostasis and Contributes to Mitochondrial Myopathy.","date":"2026","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/41989333","citation_count":0,"is_preprint":false},{"pmid":"42157244","id":"PMC_42157244","title":"The Wnt/StarD7 axis protects retinal ganglion cells from glutamate excitotoxicity by inhibiting ferroptosis.","date":"2026","source":"Biology direct","url":"https://pubmed.ncbi.nlm.nih.gov/42157244","citation_count":0,"is_preprint":false},{"pmid":"41398485","id":"PMC_41398485","title":"A novel function of STARD7: its tumor-promoting role involves the activation of NF-κB signaling pathway in ovarian cancer.","date":"2025","source":"Human cell","url":"https://pubmed.ncbi.nlm.nih.gov/41398485","citation_count":0,"is_preprint":false},{"pmid":"41912870","id":"PMC_41912870","title":"The lipid transfer protein STARD7 controls intestinal tumor development in a context-dependent manner.","date":"2026","source":"EMBO molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41912870","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.06.11.25329386","title":"Diverse Genomes, Shared Health: Insights from a Health System Biobank","date":"2025-06-12","source":"bioRxiv","url":"https://doi.org/10.1101/2025.06.11.25329386","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.16.643571","title":"Rewiring of 3D chromatin topology orchestrates transcriptional reprogramming in muscle fiber-type specification and transformation","date":"2025-03-17","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.16.643571","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18503,"output_tokens":5049,"usd":0.065622,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13437,"output_tokens":4478,"usd":0.089567,"stage2_stop_reason":"end_turn"},"total_usd":0.155189,"stage1_batch_id":"msgbatch_013LWZZT6MWaqB9qyTSeQBmU","stage2_batch_id":"msgbatch_0194ZzQaTGNpruoNJBbEMbt3","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2009,\n      \"finding\": \"StarD7 specifically catalyzes the transfer of phosphatidylcholine (PC) between lipid vesicles in vitro, and overexpression of StarD7-I (the isoform containing a mitochondrial-targeting sequence) increases intracellular transport of fluorescent PC to mitochondria. StarD7-I localizes to mitochondria (associated with the outer mitochondrial membrane by protease K protection assay) while StarD7-II is constitutively cytoplasmic.\",\n      \"method\": \"In vitro PC transfer assay with purified recombinant protein, fluorescent PC trafficking assay in HEPA-1 cells, protease K protection assay, overexpression and subcellular fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of PC transfer activity with purified protein, combined with cell-based fluorescent lipid trafficking and organelle fractionation; foundational mechanistic paper replicated by subsequent studies\",\n      \"pmids\": [\"20042613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The mitochondrial inner membrane rhomboid protease PARL cleaves STARD7 during mitochondrial import, partitioning it between the cytosol and the mitochondrial intermembrane space (IMS). Negatively charged amino acids in STARD7 serve as a sorting signal for cytosolic release after PARL cleavage, while TIM23-mediated membrane insertion promotes mitochondrial IMS retention. Mitochondrial STARD7 is necessary and sufficient for PC accumulation in the inner membrane and for maintenance of respiration and cristae morphogenesis.\",\n      \"method\": \"PARL knockout cells, co-immunoprecipitation, subcellular fractionation, mitochondrial import assays, site-directed mutagenesis of sorting signal, rescue experiments with STARD7 variants\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal genetic and biochemical dissection of PARL cleavage and sorting signal using multiple orthogonal methods; replicated and extended in 2023 Nature Cell Biology paper\",\n      \"pmids\": [\"29301859\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"StarD7's START domain harbors a shared binding site for both phosphatidylcholine (PC) and ceramide, as demonstrated by photoaffinity labeling with a clickable ceramide analog (pacCer) and site-directed mutagenesis. StarD7 lacks robust ceramide transfer activity in vitro, but ceramide specifically inhibits StarD7's ability to shuttle PC between model membranes.\",\n      \"method\": \"Photoaffinity labeling with bifunctional ceramide analog (pacCer), site-directed mutagenesis of START domain, in vitro PC transfer assay with ceramide competition\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with mutagenesis and photoaffinity labeling in a single study; identifies shared binding site for PC and ceramide\",\n      \"pmids\": [\"29343537\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"StarD7 knockout (via CRISPR/Cas9n) and knockdown in HEPA-1 cells reduces mitochondrial PC content, impairs oxygen consumption rate and mitochondrial complex activities, lowers ATP levels, reduces MTCO1 (complex IV subunit) protein without affecting its mRNA, disrupts mitochondrial supercomplex formation, and causes disorganized cristae structure. Re-expression of StarD7-I rescues MTCO1 levels and mitochondrial abnormalities.\",\n      \"method\": \"siRNA knockdown, CRISPR/Cas9n knockout, real-time respirometry (Seahorse), mitochondrial complex activity assay, phospholipid analysis, rescue by overexpression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with rescue, multiple orthogonal readouts of mitochondrial function; independently replicated by multiple labs\",\n      \"pmids\": [\"27694445\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"StarD7-I contains a transmembrane (TM) domain C-terminal to its mitochondrial-targeting signal that anchors the mature protein to the outer leaflet of the outer mitochondrial membrane (OMM). The precursor is cleaved between Met76–Ala77 and Ala77–Ala78 in the TM domain. A truncated StarD7 lacking the TM domain localizes to the mitochondrial matrix and cannot rescue mitochondrial complex formation or PC content defects in StarD7-KO cells, unlike full-length StarD7-I.\",\n      \"method\": \"Truncation mutants, immunofluorescence and subcellular fractionation in HEPA-1 and HepG2 cells, N-terminal sequencing of cleavage site, rescue of StarD7-KO cells with wild-type vs. truncated forms\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mutagenesis with precise cleavage site mapping and functional rescue experiments; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"28821867\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Stard7 deficiency in lung bronchiolar epithelial cells (BEAS-2B knockdown and Stard7epi∆/∆ mice) causes altered mitochondrial size and membrane organization, decreased aerobic respiration, increased oxidant stress, and mitochondrial DNA damage, which in turn disrupts epithelial barrier integrity and function. These defects are rescued by targeting Stard7 to mitochondria or treating cells with a mitochondrial-targeted antioxidant.\",\n      \"method\": \"siRNA knockdown in BEAS-2B, conditional epithelial-specific KO mice, respirometry, ROS assays, mtDNA damage assay, barrier permeability assay, rescue with mitochondria-targeted Stard7 and MitoTEMPO\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro and in vivo KO with mechanistic rescue linking PC transfer to mitochondrial function to barrier integrity\",\n      \"pmids\": [\"28401922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"STARD7 is a critical factor for intracellular coenzyme Q (CoQ) transport from mitochondria to the plasma membrane and suppressor of ferroptosis. PARL-mediated cleavage of STARD7 partitions it between the mitochondrial IMS (where it supports CoQ synthesis and cristae morphogenesis) and the cytosol (where it transports CoQ to the plasma membrane to limit lipid peroxidation). A CoQ variant competes with PC for binding to purified STARD7 in vitro. Overexpression of cytosolic STARD7 increases ferroptosis resistance but reduces mitochondrial CoQ and respiratory growth.\",\n      \"method\": \"PARL and STARD7 KO/rescue cells, in vitro competitive binding assay with purified STARD7 and CoQ/PC, ferroptosis assays (lipid peroxidation, cell viability), lipidomics, respirometry, STARD7 isoform overexpression\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of competitive binding, genetic dissection with isoform-specific rescue, multiple orthogonal functional readouts; high-impact peer-reviewed journal\",\n      \"pmids\": [\"36658222\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Recombinant StarD7 functions as a fusogenic protein: it accelerates lipid dilution between donor and acceptor liposomes via bilayer fusion (not monomeric lipid transport), as demonstrated by fluorescence de-quenching, FRET between labeled lipids, dynamic light scattering, and induction of multinuclear giant cell formation. Fusogenic activity depends on electrostatic interactions with the lipid-water interface and is favored by phosphatidylethanolamine.\",\n      \"method\": \"Fluorescence de-quenching assay, FRET-based lipid mixing assay, dynamic light scattering, multinuclear giant cell formation with recombinant protein, pH and salt modulation experiments\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro reconstitution with multiple biophysical methods in a single lab; fusogenic mechanism not extensively replicated\",\n      \"pmids\": [\"22063720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"StarD7.I overexpression in HTR-8/SVneo cells increases PC transport to mitochondria, alters mitochondrial morphology (increased fragmentation), and modulates fission/fusion proteins: Drp1 and Mfn2 are increased while Mfn1 is decreased. Mitochondrial fragmentation in StarD7.I-overexpressing cells occurs in a fission-dependent manner via Drp1 (established by dominant-negative Drp1-K38A, and phosphomimetic/non-phosphorylatable Drp1 mutants). StarD7 silencing decreases Mfn1 and Mfn2 without changing Drp1 and induces donut-shaped mitochondria.\",\n      \"method\": \"Stable overexpression of StarD7.I and StarD7.II isoforms, siRNA knockdown, transfection with Drp1 mutants (K38A, S637D, S637A), fluorescent PC analog transport assay, live-cell imaging, ROS measurement, mitochondrial membrane potential assay\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular and cell biology of lipids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-specific overexpression with Drp1 mutant epistasis; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"34416390\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"StarD7 silencing in HTR-8/SVneo cells decreases connexin 43 (Cx43), integrin β1, and p-ERK1/2 expression, causes Golgi disruption and reduced ability to reorient the microtubule-organizing center, and impairs cell migration. Re-expression specifically of the cytosolic StarD7.II isoform (not the mitochondria-targeted StarD7.I) restores cell migration, ERK1/2, Cx43, and integrin β1 expression, defining a mitochondria-independent, ERK1/2/Cx43-dependent mechanism for StarD7 in cell motility.\",\n      \"method\": \"siRNA knockdown, stable isoform-specific re-expression (StarD7.I vs StarD7.II), wound healing and transwell migration assays, immunofluorescence for Golgi and MTOC, Western blot for signaling proteins\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isoform-specific rescue defines pathway; single lab with multiple cellular readouts\",\n      \"pmids\": [\"36584213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In C2C12 myoblasts, PARL is not involved in StarD7 processing or maturation (unlike in HEK293 cells). StarD7 localizes to the cytosol, inner mitochondrial space, and outer leaflet of the OMM. siRNA knockdown of StarD7 impairs myogenic differentiation and reduces expression of myomaker, myomerger, and PGC-1α; these defects (including reduced mitochondrial PC and oxygen consumption) are fully rescued by re-expression of StarD7 in knockout C2C12 cells.\",\n      \"method\": \"siRNA knockdown, CRISPR KO, rescue by re-expression, immunofluorescence, immuno-electron microscopy, oxygen consumption assay, differentiation markers by Western blot/qPCR\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO with rescue in two cell types; identifies cell-type-specific difference in PARL processing and required role in myogenesis; single lab\",\n      \"pmids\": [\"32071354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"StarD7 deficiency in C2C12 myoblasts increases mitophagy flux: knockdown cells accumulate LC3B-II and BNIP3 in mitochondria-enriched fractions, accumulate autophagolysosomal vesicles, and show enhanced mitochondria delivery to lysosomes (by live-cell imaging with mitochondria-targeted mKeima). StarD7 reconstitution restores LC3B-II levels in mitochondrial fractions.\",\n      \"method\": \"siRNA knockdown, live-cell imaging with mitochondria-targeted mKeima, mitochondrial fractionation, LC3B-II and BNIP3 Western blot, lysosomal vesicle quantification, StarD7 rescue\",\n      \"journal\": \"The FEBS journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live-cell imaging combined with biochemical fractionation and rescue; single lab\",\n      \"pmids\": [\"37846201\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"StarD7 knockdown in HepG2 cells induces ER stress (increased IRE1α, calnexin, GRP78/BiP, PERK, p-eIF2α), alters mitochondria and ER morphology, increases ROS generation, and reduces cell viability after H2O2 exposure. Knockdown also causes p53 protein degradation and increases heme oxygenase-1 and catalase expression and catalase enzymatic activity.\",\n      \"method\": \"siRNA knockdown in HepG2 cells, Western blot for ER stress markers, ROS assay, cell viability assay, electron microscopy of organelle morphology, catalase activity assay\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — KD with multiple pathway readouts linking StarD7 to ER stress and redox homeostasis; single lab, single method per readout\",\n      \"pmids\": [\"27554972\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"SUMO1 degrader HB007 reduces StarD7 mRNA and protein in colon cancer cells through deSUMOylation and degradation of the transcription factor TCF4, which transcriptionally activates StarD7. StarD7 knockout identified as critical for HB007 anticancer activity by genome-wide CRISPR screen.\",\n      \"method\": \"Genome-wide CRISPR-Cas9 KO screen, SUMO1 degrader treatment, TCF4 deSUMOylation assay, mRNA and protein quantification in 3D organoids and PDX models\",\n      \"journal\": \"Molecular carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — CRISPR screen plus mechanistic follow-up with TCF4 deSUMOylation linking TCF4 to StarD7 transcription; single lab\",\n      \"pmids\": [\"37191369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Recombinant StarD7 protein forms stable Gibbs and Langmuir monolayers at the air-buffer interface and penetrates phospholipid monolayers, showing preference for phosphatidylserine, cholesterol, and phosphatidylglycerol, demonstrating direct protein-lipid interaction at membrane interfaces.\",\n      \"method\": \"Langmuir monolayer technique, surface pressure measurements, Gibbs film analysis with recombinant StarD7\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — biophysical characterization with recombinant protein; single method, single lab, no in-cell functional consequence demonstrated\",\n      \"pmids\": [\"14715263\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Loss of STARD7 in breast cancer cells leads to accumulation of carnitine derivatives and S-Adenosyl-L-methionine (SAM), which increases H3K27 trimethylation on promoters of cell cycle genes, causing cell cycle arrest. STARD7 deficiency also impairs EGFR trafficking to lysosomes, disrupting EGFR signaling in triple-negative breast cancer cells.\",\n      \"method\": \"STARD7 KO in breast cancer cell lines, metabolomics, ChIP-seq for H3K27me3, cell cycle analysis, EGFR trafficking assay, ERα-dependent proliferation assay\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO with metabolomics and ChIP-seq linking mitochondrial PC transfer to epigenomic regulation of cell cycle; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"40443279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Muscle-specific STARD7 knockout mice show reduced endurance exercise capacity and decreased mitochondrial PC, cardiolipin, and coenzyme Q in soleus muscle, with disorganized cristae but intact respiratory chain complexes. An in vitro binding assay indicates STARD7 preferentially transfers linoleic acid-containing PC species required for cardiolipin remodeling.\",\n      \"method\": \"Muscle-specific knockout mice, targeted lipidomics, in vitro lipid binding/transfer assay, electron microscopy, respirometry, RNA-seq, fiber-type analysis\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo KO combined with in vitro binding assay and lipidomics; single lab, multiple orthogonal methods\",\n      \"pmids\": [\"41989333\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"STARD7 is a cytosolic START-domain lipid transfer protein that exists as two isoforms (StarD7-I with a mitochondrial-targeting sequence and StarD7-II lacking it); the rhomboid protease PARL cleaves StarD7-I during mitochondrial import, partitioning it between the mitochondrial intermembrane space—where it maintains phosphatidylcholine (PC) content in the inner membrane, supports respiratory complex assembly, coenzyme Q synthesis, and cristae morphogenesis—and the cytosol, where it transports coenzyme Q to the plasma membrane to suppress ferroptosis and also regulates cell migration via an ERK1/2/Cx43 mechanism; the START domain binds both PC and ceramide at a shared site, with ceramide competing with and inhibiting PC transfer activity.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"STARD7 is a START-domain lipid transfer protein that controls mitochondrial phospholipid supply and intracellular lipid distribution, thereby governing respiratory function, cristae architecture, and redox homeostasis [#0, #3]. Its START domain catalyzes phosphatidylcholine (PC) transfer between membranes in vitro, and this same site binds ceramide and a coenzyme Q (CoQ) variant, both of which compete with PC, establishing a single ligand pocket whose occupancy tunes transfer activity [#0, #2, #6]. The protein is expressed as two isoforms: StarD7-I carries an N-terminal mitochondrial-targeting sequence and a transmembrane anchor in the outer mitochondrial membrane, while StarD7-II is constitutively cytosolic [#0, #4]. During mitochondrial import the inner-membrane rhomboid protease PARL cleaves STARD7, and an acidic sorting signal partitions the cleaved protein between the intermembrane space and the cytosol [#1]. Intramitochondrial STARD7 is necessary and sufficient to maintain inner-membrane PC, respiratory complex and supercomplex assembly, and cristae morphogenesis [#1, #3], whereas the cytosolic pool transports CoQ to the plasma membrane to limit lipid peroxidation and suppress ferroptosis [#6]. Loss of STARD7 impairs oxidative phosphorylation and disrupts epithelial barrier integrity through mitochondrial oxidant stress and mtDNA damage, is required for myogenic differentiation, and restrains mitophagy flux [#5, #10, #11]. Beyond mitochondria, the cytosolic isoform drives cell migration through an ERK1/2/connexin-43/integrin-β1 mechanism, and STARD7 supports cancer cell proliferation by linking mitochondrial lipid metabolism to metabolite-driven H3K27me3 deposition on cell-cycle gene promoters and to EGFR trafficking [#9, #15].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Before any cellular function was known, it was unclear whether STARD7 interacts directly with lipid membranes; biophysical analysis established direct protein-lipid interaction at interfaces.\",\n      \"evidence\": \"Langmuir/Gibbs monolayer surface-pressure measurements with recombinant protein\",\n      \"pmids\": [\"14715263\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Single biophysical method with no in-cell functional consequence demonstrated\",\n        \"Lipid preferences (PS, cholesterol, PG) at monolayers do not establish a physiological transfer substrate\",\n        \"No isoform or domain resolution\"\n      ]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"The molecular activity was defined by showing STARD7 is a PC-specific transfer protein, and that the StarD7-I isoform directs PC to mitochondria while StarD7-II is cytosolic.\",\n      \"evidence\": \"In vitro PC transfer assay with purified protein, fluorescent PC trafficking, protease K protection and fractionation in HEPA-1 cells\",\n      \"pmids\": [\"20042613\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Did not resolve how the precursor is processed during import\",\n        \"Mechanistic link between PC transfer and downstream mitochondrial function not yet established\"\n      ]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"An alternative mechanism was tested: whether STARD7 acts by membrane fusion rather than monomeric lipid carriage, addressing how it moves lipid between bilayers.\",\n      \"evidence\": \"Fluorescence de-quenching, FRET lipid mixing, dynamic light scattering, multinuclear giant cell formation with recombinant protein\",\n      \"pmids\": [\"22063720\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Fusogenic mechanism not extensively replicated and not reconciled with monomeric transfer model\",\n        \"Physiological relevance of fusion activity in cells not demonstrated\"\n      ]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Causal linkage between STARD7 PC transfer and mitochondrial bioenergetics was established by genetic loss-of-function with rescue, and a parallel role in ER stress/redox homeostasis was reported.\",\n      \"evidence\": \"CRISPR/Cas9n KO and siRNA in HEPA-1 with respirometry, complex activity and rescue (idx 3); siRNA in HepG2 with ER-stress and ROS readouts (idx 12)\",\n      \"pmids\": [\"27694445\", \"27554972\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How reduced PC selectively destabilizes MTCO1/supercomplexes not mechanistically resolved\",\n        \"ER-stress and p53/catalase changes (idx 12) rest on single-method readouts per endpoint\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The targeting determinants and physiological output were refined: a transmembrane anchor positions mature STARD7 on the OMM and is required for function, and epithelial loss links mitochondrial dysfunction to barrier integrity.\",\n      \"evidence\": \"Truncation mutants, N-terminal cleavage-site sequencing and rescue (idx 4); BEAS-2B knockdown and epithelial-specific KO mice with antioxidant rescue (idx 5)\",\n      \"pmids\": [\"28821867\", \"28401922\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Protease responsible for the TM-domain cleavage not identified in idx 4\",\n        \"Whether barrier defects are fully attributable to PC transfer versus secondary oxidant stress not separated\"\n      ]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The import/sorting logic and the ligand-binding basis of regulation were resolved: PARL cleavage plus an acidic sorting signal partitions STARD7 between IMS and cytosol, and the START domain uses a shared PC/ceramide site where ceramide inhibits PC transfer.\",\n      \"evidence\": \"PARL KO cells, import assays, sorting-signal mutagenesis and rescue (idx 1); pacCer photoaffinity labeling, START-domain mutagenesis and ceramide-competition transfer assay (idx 2)\",\n      \"pmids\": [\"29301859\", \"29343537\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether ceramide regulation of PC transfer operates in cells, not only in vitro\",\n        \"Structural model of the shared binding pocket not determined\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Tissue-context dependence and a developmental requirement were established: PARL is dispensable for STARD7 processing in myoblasts, and STARD7 is required for myogenic differentiation via mitochondrial PC/respiration and PGC-1α.\",\n      \"evidence\": \"siRNA, CRISPR KO and rescue in C2C12, immuno-EM, respirometry, differentiation-marker analysis\",\n      \"pmids\": [\"32071354\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Alternative processing protease in C2C12 not identified\",\n        \"Single lab; cell-type specificity of PARL independence not generalized\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"A regulatory connection to mitochondrial dynamics was tested, showing isoform-specific STARD7-I overexpression drives Drp1-dependent fragmentation and alters fusion proteins.\",\n      \"evidence\": \"Isoform-specific stable overexpression and siRNA in HTR-8/SVneo, Drp1 mutant epistasis, fluorescent PC transport and live-cell imaging\",\n      \"pmids\": [\"34416390\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether fission changes are a direct lipid effect or secondary to bioenergetic stress not resolved\",\n        \"Single cell type, overexpression-based\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A mitochondria-independent function was defined: cytosolic StarD7.II drives cell migration through ERK1/2/Cx43/integrin-β1 signaling and MTOC/Golgi reorientation.\",\n      \"evidence\": \"siRNA with isoform-specific re-expression (StarD7.I vs II), migration assays, immunofluorescence and signaling Western blots in HTR-8/SVneo\",\n      \"pmids\": [\"36584213\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"How cytosolic STARD7 lipid handling connects mechanistically to ERK1/2 activation not established\",\n        \"Single lab, single cell type\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"The cytosolic pool was assigned a distinct cargo and physiological output—CoQ transport to the plasma membrane to suppress ferroptosis—while additional studies linked STARD7 to mitophagy control and to transcriptional regulation by TCF4.\",\n      \"evidence\": \"PARL/STARD7 KO-rescue, in vitro CoQ/PC competitive binding, ferroptosis and lipidomics assays (idx 6); mKeima mitophagy imaging in C2C12 (idx 11); CRISPR screen and TCF4 deSUMOylation in colon cancer (idx 13)\",\n      \"pmids\": [\"36658222\", \"37846201\", \"37191369\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How a single START pocket coordinates PC, ceramide and CoQ binding in vivo not structurally resolved\",\n        \"Mitophagy and TCF4-transcription findings (Medium) are single-lab\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"STARD7 was linked to cancer cell proliferation through metabolic-epigenetic coupling and receptor trafficking, broadening its role beyond bioenergetics.\",\n      \"evidence\": \"STARD7 KO in breast cancer cells with metabolomics, H3K27me3 ChIP-seq, cell-cycle analysis and EGFR trafficking assays\",\n      \"pmids\": [\"40443279\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Causal chain from carnitine/SAM accumulation to H3K27me3 not fully dissected\",\n        \"Single lab; relationship between EGFR trafficking defect and lipid transfer unclear\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"An in vivo muscle requirement and a substrate-specificity refinement were established: STARD7 preferentially transfers linoleic-acid-containing PC supporting cardiolipin remodeling and endurance capacity.\",\n      \"evidence\": \"Muscle-specific KO mice with targeted lipidomics, in vitro binding/transfer assay, EM and respirometry\",\n      \"pmids\": [\"41989333\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism connecting PC species selectivity to cardiolipin remodeling enzymes not defined\",\n        \"Respiratory complexes intact despite cristae defects—uncoupling of phenotypes not explained\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A unified structural and regulatory model for how one START pocket selects among PC species, ceramide, and CoQ in different subcellular pools—and how isoform partitioning is controlled in a tissue-specific manner—remains open.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No high-resolution structure of the START domain with bound ligands\",\n        \"In vivo regulation of cytosol-versus-IMS partitioning beyond PARL not defined\",\n        \"No human Mendelian disease link established in the corpus\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [0, 2, 6, 16]},\n      {\"term_id\": \"GO:0140104\", \"supporting_discovery_ids\": [0, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 1, 3, 4]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 1, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 3, 6, 16]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"PARL\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}