Affinage

TRIAP1

TP53-regulated inhibitor of apoptosis 1 · UniProt O43715

Length
76 aa
Mass
8.8 kDa
Annotated
2026-06-10
33 papers in source corpus 16 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

TRIAP1 is a small cysteine-rich mitochondrial intermembrane-space (IMS) protein that, together with PRELI-family partners, functions as an intramitochondrial lipid transfer module governing phospholipid biosynthesis and apoptotic priming (PMID:23931759, PMID:27241913, PMID:27354379). It is imported into the IMS through the MIA40/CHCHD4 oxidative disulfide-relay, which accelerates folding of the reduced cytosolic protein toward its native two-disulfide structure and away from a non-native kinetic trap (PMID:39909379, PMID:38157298). In the IMS TRIAP1 forms a stable complex with PRELI/Ups1 that transfers phosphatidic acid to the inner membrane to support cardiolipin synthesis (PMID:23931759), while the SLMO2/Ups2-TRIAP1 complex transfers phosphatidylserine to enable its decarboxylation to phosphatidylethanolamine (PMID:27241913, PMID:27354379); the yeast ortholog Mdm35 additionally stabilizes its PRELI-family partners against proteolysis, and crystallography of the Ups1-Mdm35-PA complex defines a barrel-like PA-binding pocket clamped by the Mdm35 three-helix fold (PMID:20657548, PMID:26071601). By maintaining cardiolipin, TRIAP1 restrains cytochrome c release and suppresses the APAF1/caspase-9 apoptosome, so its loss fragments mitochondria, releases cytochrome c, and activates caspase-9/-3 (PMID:23931759, PMID:27428374, PMID:27032384). TRIAP1 is a p53 target gene that promotes survival under sub-lethal genotoxic stress, binds cytoplasmic HSP70 to block apoptosome assembly, and acts as a pathway-specific repressor of p21 within the p53 program (PMID:15735003, PMID:23684607). Through these activities TRIAP1 confers chemo- and radio-resistance and enables survival following mitotic slippage by retaining cytochrome c in mitochondria (PMID:25998939, PMID:36917609).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2005 Medium

    Establishing TRIAP1 as a p53-inducible survival factor answered how the gene is regulated and connected it to apoptosis suppression via the apoptosome.

    Evidence p53-binding-site identification, gain/loss-of-function apoptosis assays, and Hsp70 Co-IP in human cells

    PMID:15735003

    Open questions at the time
    • Mechanism downstream of HSP70 binding only inferred
    • No structural basis for HSP70 interaction
  2. 2010 High

    Yeast genetics defined Mdm35 (TRIAP1 ortholog) as a chaperone/stabilizer of PRELI-family proteins, linking the protein to mitochondrial phospholipid regulation for the first time.

    Evidence Reciprocal Co-IP, protease-sensitivity assays, and deletion mutants with cardiolipin/PE quantification in yeast

    PMID:20657548

    Open questions at the time
    • Direct lipid transfer activity not yet demonstrated
    • Human ortholog function not addressed
  3. 2013 High

    Demonstrating TRIAP1-PRELI lipid transfer activity and its requirement for cardiolipin accumulation explained mechanistically how TRIAP1 controls cytochrome c release and apoptotic vulnerability.

    Evidence Co-IP, in vitro PA lipid transfer assay, loss-of-function with cytochrome c release readouts, and phosphatidylglycerol rescue in human cells

    PMID:23931759

    Open questions at the time
    • Stoichiometry and dynamics of transfer in vivo unresolved
    • Structural basis not defined in this study
  4. 2013 Medium

    A genome-wide screen revealed TRIAP1 as a pathway-specific repressor of p21, refining its role within the p53 transcriptional program beyond apoptosis suppression.

    Evidence Genome-wide RNAi screen with targeted validation, p21/PUMA expression and cell-cycle readouts

    PMID:23684607

    Open questions at the time
    • Molecular mechanism of p21 repression unknown
    • Whether mitochondrial or cytoplasmic TRIAP1 mediates this is unclear
  5. 2015 High

    The Ups1-Mdm35-PA crystal structure provided the atomic architecture of the lipid-binding pocket, converting the functional model into a structural mechanism.

    Evidence X-ray crystallography with site-directed mutagenesis and in vitro PA-binding/transfer assays

    PMID:26071601

    Open questions at the time
    • Conformational changes during lipid loading/unloading not captured
    • Structure of human TRIAP1 complex not solved
  6. 2015 Medium

    Linking TRIAP1 to caspase-9 inhibition and doxorubicin resistance extended its survival function into a chemoresistance context.

    Evidence Stable overexpression/siRNA, caspase-9 activity assay, and colony formation under drug selection in breast cancer cells

    PMID:25998939

    Open questions at the time
    • Mechanistic detail limited
    • Direct caspase-9/apoptosome binding not shown
  7. 2016 High

    Identifying Ups2-Mdm35/SLMO2-TRIAP1 as a PS-specific transfer protein enabling PS-to-PE conversion broadened TRIAP1's substrate range and explained its role in PE biosynthesis.

    Evidence In vitro liposome transfer with recombinant fusion protein and radiolabeled PS-to-PE conversion in yeast null mutants

    PMID:27241913 PMID:27354379

    Open questions at the time
    • Substrate selectivity determinants between PA and PS partners not fully resolved
    • In vivo flux control quantification incomplete
  8. 2016 Medium

    Cellular and in vivo loss-of-function studies confirmed that TRIAP1 maintains mitochondrial integrity and represses the APAF1/caspase-9 apoptosome.

    Evidence siRNA/shRNA knockdown with rescue, mitochondrial morphology/membrane-potential imaging, cytochrome c fractionation, and qRT-PCR/caspase assays in NPC and myeloma cells plus xenografts

    PMID:27032384 PMID:27428374

    Open questions at the time
    • Whether effects are solely cardiolipin-dependent not dissected
    • Direct apoptosome-component binding not demonstrated
  9. 2022 Medium

    Showing that TRIAP1 depletion alters ER-dependent lipid homeostasis without changing cardiolipin in colorectal cells revealed context-dependent, possibly extramitochondrial, metabolic roles.

    Evidence Stable shRNA knockdown with electron microscopy, cardiolipin quantification, metabolomics, p53 reporters, and glutamine-deprivation survival assays

    PMID:36387192

    Open questions at the time
    • Mechanism of ER lipid homeostasis effect unknown
    • Reconciliation with cardiolipin-dependent models in other cell types unresolved
  10. 2023 Medium

    Two studies connected TRIAP1 mitochondrial import and abundance to physiological outcomes: cytochrome c retention during mitotic slippage and CHCHD4-dependent control of cardiolipin, VDAC oligomerization, and innate-immune signaling in muscle.

    Evidence Cell-fate tracking with cytochrome c localization in human cells, and CHCHD4-haploinsufficient mouse model with cardiolipin/VDAC/mtDNA-release and cGAS-STING readouts

    PMID:36917609 PMID:38157298

    Open questions at the time
    • TRIAP1 import dependency on CHCHD4 not reconstituted in vitro
    • Direct contribution of TRIAP1 versus pathway-wide CHCHD4 effects hard to separate
  11. 2025 High

    Mapping the MIA40-assisted oxidative folding pathway of TRIAP1 explained how the reduced cytosolic protein attains its native disulfide-bonded IMS structure, and a tumor study reaffirmed the SLMO2-TRIAP1 interaction in promoting survival.

    Evidence NMR, disulfide-bond mapping, in vitro MIA40 folding assays; plus Co-IP and functional/xenograft assays in ovarian cancer cells

    PMID:39909379 PMID:40654025

    Open questions at the time
    • In vivo kinetics of TRIAP1 import not measured
    • How folding state couples to lipid-transfer competence unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • How TRIAP1 partitions between its mitochondrial lipid-transfer role and its cytoplasmic apoptosome/HSP70-dependent and p53-coregulatory functions, and whether these are mechanistically coupled, remains unresolved.
  • No structure of the human TRIAP1-PRELI or TRIAP1-HSP70 complex
  • Quantitative determinants of substrate (PA vs PS) selectivity unknown
  • Cell-type-dependent cardiolipin requirement not reconciled

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0008289 lipid binding 3 GO:0098772 molecular function regulator activity 3 GO:0140104 molecular carrier activity 2
Localization
GO:0005739 mitochondrion 3 GO:0005829 cytosol 2
Pathway
R-HSA-1430728 Metabolism 3 R-HSA-5357801 Programmed Cell Death 3 R-HSA-392499 Metabolism of proteins 2
Complex memberships
TRIAP1-PRELI/SLMO2 lipid transfer complex

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2013 TRIAP1 (p53CSV) forms a complex with PRELI in the mitochondrial intermembrane space (IMS) that exerts lipid transfer activity in vitro, supplying phosphatidic acid (PA) for cardiolipin (CL) synthesis in the inner membrane. Loss of TRIAP1 or PRELI impairs CL accumulation, facilitates cytochrome c release, and renders cells vulnerable to apoptosis; survival is rescued by exogenous phosphatidylglycerol. Co-immunoprecipitation, in vitro lipid transfer assay, loss-of-function (siRNA/KO) with cytochrome c release and apoptosis readouts, lipid rescue experiment Cell metabolism High 23931759
2010 Mdm35 (the yeast ortholog of TRIAP1) binds Ups1 and Ups2 (PRELI-family proteins) in the mitochondrial IMS, protecting them from proteolytic degradation by Yme1 and Atp23 and ensuring their import, thereby regulating cardiolipin and phosphatidylethanolamine levels in mitochondrial membranes. Yeast genetics, co-immunoprecipitation, protease-sensitivity assays, deletion mutants with lipid quantification The EMBO journal High 20657548
2016 Ups2-Mdm35 complexes (SLMO2-TRIAP1 in humans) function as phosphatidylserine (PS)-specific lipid transfer proteins in the mitochondrial IMS, enabling PS decarboxylation to phosphatidylethanolamine (PE) by Psd1 at the inner membrane; a recombinant Ups2-Mdm35 fusion protein exhibits PS transfer activity between liposomes in vitro. In vitro liposome lipid transfer assay with recombinant fusion protein, yeast null mutants with radiolabeled PS-to-PE conversion, genetic analysis The Journal of cell biology High 27241913 27354379
2015 Crystal structure of the Ups1-Mdm35-PA complex (yeast ortholog of TRIAP1-PRELI) reveals that Ups1 forms a barrel-like structure with a tunnel-like PA-binding pocket covered by helix α2, while Mdm35 adopts a three-helical clamp-like structure wrapping around Ups1. Hydrophobic residues lining the pocket and helix α2, plus a hydrophilic surface patch near the PA phosphate-binding site, are critical for PA binding and transfer as shown by mutagenesis. X-ray crystallography, site-directed mutagenesis, in vitro PA-binding and transfer assays EMBO reports High 26071601
2005 TRIAP1 (p53CSV) is a p53 target gene containing a p53-binding site in its second exon. Overexpression protects cells from DNA-damage-induced apoptosis, while siRNA knockdown enhances apoptosis. TRIAP1 interacts with Hsp70 in the cytoplasm, likely inhibiting apoptosome formation via Apaf-1. siRNA knockdown, overexpression, apoptosis assays, co-immunoprecipitation with Hsp70, reporter/binding-site analysis Cancer research Medium 15735003
2013 A genome-wide genetic screen identified TRIAP1 as a specific repressor of p21 (CDKN1A) expression upon p53 activation; TRIAP1 depletion slows cell-cycle progression without broadly affecting PUMA-mediated apoptosis, placing TRIAP1 as a pathway-specific coregulator of the p53 transcriptional program. Genome-wide RNAi screen, targeted siRNA depletion, p21/PUMA expression readouts, cell-cycle analysis Cell reports Medium 23684607
2016 TRIAP1 knockdown in NPC cells induces mitochondrial fragmentation, membrane potential alteration, and cytochrome c release from mitochondria into the cytosol, enhancing apoptosis; these effects are phenocopied by miR-320b overexpression and reversed by TRIAP1 restoration. siRNA knockdown, overexpression rescue, mitochondrial morphology imaging, membrane potential assay, cytochrome c fractionation, in vivo xenograft PLoS genetics Medium 27428374
2015 TRIAP1 inhibits caspase-9 activation in the cytoplasm (apoptosome-blocking activity); stable overexpression of TRIAP1 in breast cancer cells increases doxorubicin-resistant clone formation, while siRNA knockdown of TRIAP1 in drug-resistant cells impairs growth in the presence of doxorubicin. Stable transfection/overexpression, siRNA, caspase-9 activity assay, colony formation under drug selection Oncology reports Medium 25998939
2016 Stable shRNA-mediated silencing of TRIAP1 in RPMI8226 multiple myeloma cells increases late apoptosis accompanied by upregulation of APAF1 and caspase-9 expression, and activation of caspase-9 and caspase-3/7, establishing that TRIAP1 suppresses the APAF1/caspase-9 apoptosome pathway. Lentiviral shRNA stable knockdown, flow cytometry (annexin V/PI), qRT-PCR for APAF1 and caspase-9, caspase activity assays Biochimica et biophysica acta Medium 27032384
2025 TRIAP1 is imported into the mitochondrial IMS via the MIA40 oxidative folding relay. In its reduced cytosolic state, TRIAP1 rapidly forms a hydrophobic, alpha-helical, marginally stable molten globule intermediate that biases oxidative folding toward a non-native Cys37-Cys47 kinetic trap. MIA40 accelerates TRIAP1 folding by 30-fold by driving oxidation of the inner disulfide bond (Cys18-Cys37) and then the outer disulfide bond (Cys8-Cys47), yielding the native two-disulfide-bridged structure and bypassing the kinetic trap. NMR, biochemical oxidative folding assays, disulfide-bond mapping, mutagenesis, in vitro MIA40 interaction assays The Journal of biological chemistry High 39909379
2023 TRIAP1 upregulation in human cells after nocodazole treatment retains cytochrome c in mitochondria, opposing partial caspase activation caused by prolonged mitotic arrest, thereby enabling escape from the G1 arrest that follows mitotic slippage. Decreasing TRIAP1 re-sensitizes cells to nocodazole. Long-term cell-fate tracking, cytochrome c localization (mitochondrial fractionation/imaging), caspase activation assays, siRNA knockdown and overexpression, proliferation assays Cell reports Medium 36917609
2023 Exercise training downregulates CHCHD4, a mitochondrial disulfide relay carrier, which decreases import of TRIAP1 into mitochondria. Reduced mitochondrial TRIAP1 lowers cardiolipin levels and promotes VDAC oligomerization in skeletal muscle, facilitating mtDNA release and activating cGAS-STING/NFKB innate immune signaling, ultimately downregulating MyoD and promoting oxidative slow-twitch fiber formation. Mouse genetic model (CHCHD4 haploinsufficiency), cardiolipin quantification, VDAC oligomerization assay, mtDNA release assay, cGAS-STING/NFKB pathway analysis, skeletal muscle fiber-type characterization Cell reports Medium 38157298
2025 SLMO2 (PRELI) interacts with TRIAP1 in ovarian cancer cells, enhancing mitochondrial membrane potential, reducing ROS, and inhibiting autophagy-dependent apoptosis. Co-expression of SLMO2 and TRIAP1 promotes tumor cell growth in vivo. Co-immunoprecipitation/interaction assay, flow cytometry, western blotting for autophagy markers, mitochondrial membrane potential assay, ROS measurement, xenograft mouse model Histology and histopathology Medium 40654025
2022 In colorectal cancer cells, TRIAP1 depletion perturbs mitochondrial ultrastructure and alters endoplasmic reticulum-dependent lipid homeostasis without a major impact on cardiolipin levels or mitochondrial respiratory activity. TRIAP1 depletion also induces a p53-mediated stress response and confers resistance to glutamine deprivation, indicating extramitochondrial roles for TRIAP1 in lipid homeostasis and metabolic stress adaptation. shRNA stable knockdown, electron microscopy (mitochondrial ultrastructure), cardiolipin quantification, metabolomics, p53 pathway reporter assays, glutamine deprivation survival assays Frontiers in oncology Medium 36387192
2020 TRIAP1 knockdown in NSCLC cells (A549, H460) decreases expression of multiple antioxidant proteins (TMX1, TMX2, TXN, GLRX2, GLRX3, PRDX3, PRDX4, PRDX6), impairs radiation-induced upregulation of these proteins, and increases intracellular reactive oxygen species, thereby reducing radioresistance. siRNA knockdown, western blotting for antioxidant proteins, ROS measurement, cell viability and apoptosis assays after irradiation Thoracic cancer Low 32096592

Source papers

Stage 0 corpus · 33 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2013 TRIAP1/PRELI complexes prevent apoptosis by mediating intramitochondrial transport of phosphatidic acid. Cell metabolism 167 23931759
2010 Regulation of mitochondrial phospholipids by Ups1/PRELI-like proteins depends on proteolysis and Mdm35. The EMBO journal 143 20657548
2016 MICOS and phospholipid transfer by Ups2-Mdm35 organize membrane lipid synthesis in mitochondria. The Journal of cell biology 130 27241913
2016 Phosphatidylserine transport by Ups2-Mdm35 in respiration-active mitochondria. The Journal of cell biology 64 27354379
2013 A genetic screen identifies TCF3/E2A and TRIAP1 as pathway-specific regulators of the cellular response to p53 activation. Cell reports 60 23684607
2005 p53CSV, a novel p53-inducible gene involved in the p53-dependent cell-survival pathway. Cancer research 60 15735003
2016 Overexpression of Mitochondria Mediator Gene TRIAP1 by miR-320b Loss Is Associated with Progression in Nasopharyngeal Carcinoma. PLoS genetics 50 27428374
2015 Structural basis of intramitochondrial phosphatidic acid transport mediated by Ups1-Mdm35 complex. EMBO reports 48 26071601
2009 SAGE analysis highlights the importance of p53csv, ddx5, mapkapk2 and ranbp2 to multiple myeloma tumorigenesis. Cancer letters 44 19171422
2015 Apoptosis inhibitor TRIAP1 is a novel effector of drug resistance. Oncology reports 37 25998939
2017 MicroRNA-18a inhibits ovarian cancer growth via directly targeting TRIAP1 and IPMK. Oncology letters 34 28588697
2021 Circular RNA circPVT1 Contributes to Doxorubicin (DXR) Resistance of Osteosarcoma Cells by Regulating TRIAP1 via miR-137. BioMed research international 28 33981772
2019 Progression-Related Loss of Stromal Caveolin 1 Levels Mediates Radiation Resistance in Prostate Carcinoma via the Apoptosis Inhibitor TRIAP1. Journal of clinical medicine 27 30871022
2016 TP53 Regulated Inhibitor of Apoptosis 1 (TRIAP1) stable silencing increases late apoptosis by upregulation of caspase 9 and APAF1 in RPMI8226 multiple myeloma cell line. Biochimica et biophysica acta 21 27032384
2020 Regulation of Apoptosis and Inflammatory Response in Interleukin-1β-Induced Nucleus Pulposus Cells by miR-125b-5p Via Targeting TRIAP1. Biochemical genetics 18 33123835
2022 PCGEM1 promotes proliferation, migration and invasion in prostate cancer by sponging miR-506 to upregulate TRIAP1. BMC urology 16 35109849
2019 miR-107 targets TRIAP1 to regulate oral squamous cell carcinoma proliferation and migration. International journal of clinical and experimental pathology 16 31934005
2021 The effect of miR-539 regulating TRIAP1 on the apoptosis, proliferation, migration and invasion of osteosarcoma cells. Cancer cell international 15 33879126
2020 TRIAP1 knockdown sensitizes non-small cell lung cancer to ionizing radiation by disrupting redox homeostasis. Thoracic cancer 14 32096592
2019 TRIAP1 Inhibition Activates the Cytochrome c/Apaf-1/Caspase-9 Signaling Pathway to Enhance Human Ovarian Cancer Sensitivity to Cisplatin. Chemotherapy 13 31661694
2023 CHCHD4-TRIAP1 regulation of innate immune signaling mediates skeletal muscle adaptation to exercise. Cell reports 12 38157298
2022 miR-107 Inhibits the Proliferation of Gastric Cancer Cells In vivo and In vitro by Targeting TRIAP1. Frontiers in genetics 12 35480301
2020 Upregulation of TRIAP1 by the lncRNA MFI2-AS1/miR-125a-5p Axis Promotes Thyroid Cancer Tumorigenesis. OncoTargets and therapy 11 32764987
2022 Relevance of the TRIAP1/p53 axis in colon cancer cell proliferation and adaptation to glutamine deprivation. Frontiers in oncology 10 36387192
2019 miR-1301/TRIAP1 Axis Participates in Epirubicin-Mediated Anti-Proliferation and Pro-Apoptosis in Osteosarcoma. Yonsei medical journal 10 31433581
2021 Abnormal expression of TRIAP1 and its role in gestational diabetes mellitus-related pancreatic β cells. Experimental and therapeutic medicine 7 33488796
2022 Transcriptomic Analysis Reveals That Granulocyte Colony-Stimulating Factor Trigger a Novel Signaling Pathway (TAF9-P53-TRIAP1-CASP3) to Protect Retinal Ganglion Cells after Ischemic Optic Neuropathy. International journal of molecular sciences 6 35955492
2024 Circular RNA NFIX Functions as an Oncogene in Non-Small Cell Lung Cancer by Modulating the miR-214-3p/TRIAP1 Axis. The clinical respiratory journal 4 39135128
2025 MIA40 circumvents the folding constraints imposed by TRIAP1 function. The Journal of biological chemistry 3 39909379
2024 Upregulated microRNA-125b-5p in patients with asthma-COPD overlap mediates oxidative stress and late apoptosis via targeting IL6R/TRIAP1 signaling. Respiratory research 3 38302925
2023 Triap1 upregulation promotes escape from mitotic-slippage-induced G1 arrest. Cell reports 2 36917609
1976 Biochemical characteristics of rat C-type virus WF-1. Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.) 2 57624
2025 SLMO2 inhibits apoptosis in ovarian cancer cells by modulating mitochondrial function via TRIAP1. Histology and histopathology 0 40654025

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