{"gene":"ABCD3","run_date":"2026-06-09T22:02:36","timeline":{"discoveries":[{"year":2025,"finding":"Cryo-EM structures of full-length human ABCD3 in apo state (3.33 Å) and bound to phytanoyl-CoA (3.13 Å) reveal that substrate binding brings the two nucleotide-binding domains closer together, stimulating ATPase activity via a substrate-dependent conformational change. This provides a mechanistic basis for substrate-induced ATPase activation and the transport mechanism.","method":"Cryo-EM structure determination (apo and substrate-bound states) combined with biochemical ATPase activity assays","journal":"bioRxiv","confidence":"High","confidence_rationale":"Tier 1 / Moderate — atomic-resolution cryo-EM structures in two states combined with biochemical ATPase assays in a single rigorous study; preprint not yet peer-reviewed but multiple orthogonal methods","pmids":["bio_10.1101_2025.05.21.655323"],"is_preprint":true},{"year":2014,"finding":"ABCD3 is required for peroxisomal import and beta-oxidation of branched-chain fatty acids (e.g., pristanic acid) and C27 bile acid intermediates. Loss of ABCD3 (patient with truncating mutation p.Y635NfsX1 and Abcd3-/- mice) leads to accumulation of C27 bile acid intermediates and a bile acid biosynthesis defect, demonstrating ABCD3 is essential for the transport of these substrates into peroxisomes.","method":"Patient genetic analysis (homozygous deletion), biochemical analysis of patient fibroblasts and plasma, Abcd3 knockout mouse model with phytol loading and bile acid profiling","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — human patient loss-of-function combined with knockout mouse model, multiple biochemical readouts, replicated across two biological systems","pmids":["25168382"],"is_preprint":false},{"year":2013,"finding":"ABCD3 functions as a homodimer and preferentially transports hydrophilic substrates including long-chain unsaturated fatty acids, long branched-chain fatty acids, and long-chain dicarboxylic fatty acids (as CoA esters) into peroxisomes, with a distinct substrate specificity from ABCD1 and ABCD2. This was established by complementation of the yeast pxa1/pxa2Δ mutant and fatty acid oxidation measurements.","method":"Yeast complementation assay (pxa1/pxa2Δ mutant rescue) and fatty acid oxidation measurements with multiple substrates","journal":"Biochimica et biophysica acta","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — functional complementation in yeast with multiple substrate specificity assays, single lab but two orthogonal methods","pmids":["24333844"],"is_preprint":false},{"year":2018,"finding":"ABCD3 and the D-bifunctional protein HSD17B4 are essential components of a peroxisomal pathway that can oxidize medium- and long-chain fatty acids (lauric and palmitic acid), including as acylcarnitines. CRISPR-generated ABCD3 KO in HEK-293 cells abolished residual peroxisomal oxidation of these fatty acids when mitochondrial beta-oxidation was inhibited.","method":"CRISPR-Cas9 knockout of ABCD3 (single and double KO) in HEK-293 cells, acylcarnitine profiling; Hsd17b4 KO mouse model with CPT2 inhibition","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — CRISPR KO with defined biochemical phenotype, in vitro and in vivo validation across multiple KO combinations","pmids":["30540494"],"is_preprint":false},{"year":2002,"finding":"ABCD3 (PMP70) binds ATP tightly in the absence of Mg2+, hydrolyzes it to ADP in the presence of Mg2+, and releases ADP to allow catalytic turnover. Additionally, PMP70 is phosphorylated at a tyrosine residue(s). ATP binding/hydrolysis and phosphorylation are involved in regulation of fatty acid transport into peroxisomes.","method":"Photoaffinity labeling with 8-azido-[α-32P]ATP and 8-azido-[γ-32P]ATP, Mg2+-dependent hydrolysis assays, vanadate-trapping experiments, immunoprecipitation from rat liver peroxisomes","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — biochemical assays on native peroxisomes, multiple nucleotide analogs tested, but single lab study","pmids":["12176987"],"is_preprint":false},{"year":2007,"finding":"ABCD3 (PMP70) forms homodimers in living cells, and also forms heterodimers with ALDP (ABCD1) in vivo. ALDP homodimers predominate. The last 87 C-terminal amino acids of ALDP are the primary domain mediating these interactions, with the N-terminal transmembrane region providing additional stabilization of ALDP homodimers.","method":"FRET microscopy in intact living cells using fluorescently tagged constructs, C-terminal deletion constructs, statistical analysis by probability distribution shift and Kolmogorov-Smirnov analysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — live-cell FRET with domain mapping by deletion constructs, two statistical methods, single lab","pmids":["17609205"],"is_preprint":false},{"year":2004,"finding":"In mouse liver, PMP70 (ABCD3) and ALDP (ABCD1) exist predominantly as homomeric complexes, with no evidence of heteromeric interactions or accessory proteins under normal expression conditions.","method":"Two-step purification of PMP70 protein complex from mouse liver to apparent homogeneity; preparative immunoprecipitation of ALDP complex; both analyzed by protein identification","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — purification to homogeneity combined with immunoprecipitation from native tissue, single lab","pmids":["15276650"],"is_preprint":false},{"year":2002,"finding":"ATP binding and hydrolysis by PMP70 induce conformational changes in the protein specifically at the boundary between the transmembrane and nucleotide-binding domains, and in the helical domain between the Walker A and B motifs. MgATP or MgADP stabilizes a C-terminal 30-kDa fragment, while MgATP-γS protects the entire protein. The 30-kDa fragment forms a ~60 kDa complex consistent with PMP70 existing as a dimer on peroxisomal membranes.","method":"Limited trypsin digestion of rat liver peroxisomes pre-incubated with various nucleotides, followed by immunoblot analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — conformational analysis by limited proteolysis with multiple nucleotide conditions, single lab, single method","pmids":["11883951"],"is_preprint":false},{"year":2005,"finding":"Pex19p acts as a co-translational chaperone for PMP70 (ABCD3), binding it during translation to maintain solubility and proper conformation required for peroxisomal targeting. Two binding regions were identified: the N-terminal 61 amino acids and the region around TMD6. Deletion of either region prevented peroxisomal localization of GFP-PMP70 fusion proteins in CHO cells.","method":"In vitro translation system with purified Pex19p, co-immunoprecipitation, truncation/deletion constructs, GFP-fusion localization in CHO cells","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro binding combined with cell-based localization assays using multiple deletion constructs, single lab","pmids":["16344115"],"is_preprint":false},{"year":2001,"finding":"Efficient peroxisomal targeting of human PMP70 requires three targeting elements in the amino-terminal region: amino acids 61–80 (cytosolic loop), the first transmembrane domain, and the second transmembrane domain. PEX19 interactions are not required for targeting human PMP70 to peroxisomes and does not specifically bind the targeting elements.","method":"Truncation constructs and localization studies in cells; PEX19 interaction assays","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — cell-based targeting assays with multiple deletion constructs, PEX19 binding tested, single lab","pmids":["11453642"],"is_preprint":false},{"year":2009,"finding":"The N-terminal 80-amino-acid segment of PMP70 is critical for suppressing an intrinsic ER-targeting function of TM1, enabling correct peroxisomal localization. Without the N80 segment, the full-length PMP70 localizes to the ER. The N80 segment alone targets to the outer mitochondrial membrane; combined with TM1-TM2, targeting is exclusively peroxisomal. Multiple organelle-targeting signals cooperate for correct peroxisomal membrane targeting.","method":"EGFP fusion constructs with N-terminal deletions expressed in COS cells; subcellular localization by fluorescence microscopy","journal":"Journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — multiple deletion/fusion constructs in live cells with fluorescence microscopy, single lab","pmids":["20007743"],"is_preprint":false},{"year":2015,"finding":"A short 9-residue N-terminal motif in PMP70 (including Ser5 as indispensable) suppresses co-translational ER targeting by the TM1 signal sequence. Ser5Ala point mutation causes PMP70 to localize predominantly to the ER. The motif acts through binding 50-kDa and 20-kDa cytosolic proteins (crosslinking identified), functioning as an ER-targeting suppressor.","method":"Point mutagenesis (Ser5Ala), chimeric constructs with secretory signal peptide, protein crosslinking, subcellular localization by fluorescence microscopy","journal":"Journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 / Moderate — site-directed mutagenesis with localization readout and crosslinking to identify binding factors, single lab","pmids":["26711236"],"is_preprint":false},{"year":1998,"finding":"Overexpression of PMP70 (ABCD3) suppresses the peroxisome assembly defect caused by PEX2 mutations in CHO cells, restoring peroxisomal biogenesis (as measured by catalase latency, catalase localization, and VLCFA beta-oxidation). A mutant allele of PMP70 identified in a Zellweger syndrome patient failed to rescue, suggesting a functional interaction between PEX2 and PMP70 in the peroxisomal membrane.","method":"Expression of PMP70 in PEX2-deficient CHO cell clones; catalase latency assay, immunohistochemical localization of catalase, VLCFA beta-oxidation measurement","journal":"European journal of cell biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic suppression with multiple functional readouts, mutant allele control, single lab","pmids":["9765053"],"is_preprint":false},{"year":2025,"finding":"The VCP-FAF2 complex (homolog of p97-UBXD8) prevents excessive pexophagy by regulating the accumulation of ubiquitinated ABCD3 on peroxisomal membranes. Loss of FAF2 leads to increased ubiquitination of ABCD3 and consequent autophagic degradation of peroxisomes.","method":"Quantitative proteomics, ubiquitination assays, autophagy rescue experiments, depletion of VCP/FAF2","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomic and functional evidence from two complementary studies (VCP-FAF2 and p97-UBXD8 papers), ubiquitination and autophagy readouts","pmids":["39929145"],"is_preprint":false},{"year":2024,"finding":"The p97-UBXD8 complex maintains peroxisome abundance by suppressing pexophagy. Loss of UBXD8 or inhibition of p97 increases ubiquitination of PMP70 (ABCD3) on peroxisomal membranes, triggering autophagic peroxisome degradation that can be rescued by depleting key autophagy proteins or overexpressing the deubiquitylase USP30.","method":"Quantitative proteomics, UBXD8/p97 depletion, ubiquitination assays, rescue by autophagy protein depletion and USP30 overexpression","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (proteomics, ubiquitination, genetic rescue), preprint not yet peer-reviewed","pmids":["bio_10.1101_2024.09.24.614749"],"is_preprint":true},{"year":2008,"finding":"Knockdown of PMP70 (ABCD3) in rat C6 glial cells impairs peroxisomal beta-oxidation and causes oxidative stress (increased nitric oxide, superoxide, and lipid peroxidation products) and production of pro-inflammatory cytokines (TNFα, IFNγ, IL-12). The oxidative stress was shown to be downstream of IL-12 release rather than a direct consequence of PMP70 loss.","method":"Stable RNAi knockdown cell line (abcd3kd), measurement of oxidative stress markers, antioxidant enzyme activities, cytokine quantification, neutralizing antibody against IL-12","journal":"Neurochemistry international","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — stable KD with multiple functional readouts and cytokine neutralization experiment establishing pathway order, single lab","pmids":["18992293"],"is_preprint":false},{"year":2021,"finding":"ABCD3 interacts with INTS7 (integrator complex subunit 7) in mouse bone marrow mesenchymal stem cells, and this interaction suppresses oxidative stress (ROS and γ-H2AX accumulation). Knockdown of either INTS7 or ABCD3 impairs BM-MSC proliferation, induces apoptosis, decreases osteoblastic differentiation, and accelerates adipogenic differentiation.","method":"Co-immunoprecipitation (INTS7-ABCD3 interaction), RNAi knockdown of INTS7 and ABCD3, ROS measurement, differentiation assays (Alizarin Red S, Oil Red O staining)","journal":"Frontiers in physiology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP plus KD phenotype, single lab, limited mechanistic follow-up on the interaction itself","pmids":["34880777"],"is_preprint":false},{"year":1992,"finding":"NEGATIVE FINDING: The major Mg2+-ATPases induced in rat liver peroxisomes by clofibrate are not associated with PMP70 (ABCD3), as demonstrated by proteinase K sensitivity differences, failure of co-immunoprecipitation, different behavior on native PAGE, and separation by gel filtration chromatography.","method":"Proteinase K protection assay, immunoprecipitation, native PAGE, gel filtration chromatography from rat liver peroxisomes","journal":"Journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — four orthogonal negative methods consistently excluding association, single lab","pmids":["1295880"],"is_preprint":false}],"current_model":"ABCD3 (PMP70) is a half-ABC transporter that homodimerizes in the peroxisomal membrane, uses ATP hydrolysis (stimulated by substrate binding and driven by apposition of nucleotide-binding domains as revealed by cryo-EM) to transport CoA thioesters of branched-chain fatty acids, very long-chain fatty acids, dicarboxylic acids, and C27 bile acid intermediates from the cytosol into peroxisomes; its correct peroxisomal targeting depends on N-terminal suppression of an intrinsic ER-targeting signal (with Pex19p acting as a co-translational chaperone in some contexts), and its peroxisomal abundance is regulated by VCP/p97-FAF2/UBXD8-mediated control of ubiquitin-triggered pexophagy."},"narrative":{"mechanistic_narrative":"ABCD3 (PMP70) is a peroxisomal half-ABC transporter that imports CoA-thioesters of fatty acids into peroxisomes to feed beta-oxidation, functioning as a homodimer with substrate specificity distinct from its paralogs ABCD1/ABCD2 [PMID:24333844, PMID:17609205]. Its substrate range spans long-chain unsaturated, branched-chain, and dicarboxylic fatty acids as well as medium- and long-chain species, and in patients and Abcd3-null mice its loss blocks peroxisomal handling of pristanic acid and C27 bile acid intermediates, causing a bile acid biosynthesis defect [PMID:25168382, PMID:24333844, PMID:30540494]. Mechanistically, ABCD3 binds ATP and hydrolyzes it in a Mg2+-dependent manner with conformational changes at the transmembrane/nucleotide-binding domain interface, and cryo-EM of apo and phytanoyl-CoA-bound states shows that substrate binding draws the two nucleotide-binding domains together to stimulate ATPase activity [PMID:bio_10.1101_2025.05.21.655323, PMID:12176987, PMID:11883951]. Correct delivery to the peroxisomal membrane depends on an N-terminal segment that suppresses an intrinsic ER-targeting signal in the first transmembrane domain, with a 9-residue motif (Ser5 indispensable) acting through cytosolic factors; without it, ABCD3 mislocalizes to the ER [PMID:20007743, PMID:26711236]. Its peroxisomal abundance is controlled by VCP/p97 together with FAF2/UBXD8, which limit ubiquitination of ABCD3 and thereby suppress its capacity to trigger pexophagy [PMID:39929145, PMID:bio_10.1101_2024.09.24.614749].","teleology":[{"year":1992,"claim":"Established that the clofibrate-induced peroxisomal Mg2+-ATPase activity is not attributable to PMP70, separating the transporter from a confounding ATPase and focusing later mechanistic work on ABCD3 itself.","evidence":"Proteinase K protection, immunoprecipitation, native PAGE, and gel filtration of rat liver peroxisomes","pmids":["1295880"],"confidence":"Medium","gaps":["Did not define ABCD3's own catalytic activity","Identity of the induced ATPases left open"]},{"year":1998,"claim":"Showed a functional interplay between PMP70 and the biogenesis factor PEX2, hinting the transporter participates in membrane assembly beyond pure transport.","evidence":"Overexpression suppression of PEX2-deficient CHO defect; catalase latency, localization, and VLCFA beta-oxidation readouts with a Zellweger mutant allele control","pmids":["9765053"],"confidence":"Medium","gaps":["Mechanism of PEX2-PMP70 interaction not resolved","Overexpression suppression may not reflect physiological role"]},{"year":2002,"claim":"Defined ABCD3 as a genuine ATP-binding/hydrolyzing transporter, answering whether PMP70 has intrinsic nucleotide-handling catalytic turnover.","evidence":"Photoaffinity ATP labeling, Mg2+-dependent hydrolysis and vanadate-trapping on rat liver peroxisomes; limited proteolysis mapping nucleotide-induced conformational changes","pmids":["12176987","11883951"],"confidence":"Medium","gaps":["Substrate-dependence of ATPase not yet addressed","Functional role of tyrosine phosphorylation unresolved","Single-lab native-membrane assays"]},{"year":2005,"claim":"Addressed how PMP70 reaches peroxisomes versus the ER, identifying targeting determinants and a chaperone, though the requirement for PEX19 was disputed across studies.","evidence":"In vitro translation/Co-IP with Pex19p and GFP-fusion deletion localization (CHO); separately, truncation targeting assays finding PEX19 dispensable","pmids":["16344115","11453642"],"confidence":"Medium","gaps":["Conflicting conclusions on PEX19 requirement","Cytosolic factors mediating targeting not identified at this stage"]},{"year":2007,"claim":"Resolved the oligomeric state, showing ABCD3 forms homodimers in living cells and can heterodimerize with ABCD1, establishing the functional transport unit.","evidence":"Live-cell FRET with fluorescent constructs, C-terminal deletion mapping, and statistical distribution analysis; corroborated by native-tissue purification favoring homomers","pmids":["17609205","15276650"],"confidence":"High","gaps":["Physiological significance of ABCD1 heterodimers unclear","Stoichiometry under transport conditions not defined"]},{"year":2013,"claim":"Defined ABCD3 substrate specificity, establishing it transports long-chain unsaturated, branched-chain, and dicarboxylic fatty acyl-CoAs distinct from ABCD1/ABCD2.","evidence":"Yeast pxa1/pxa2Δ complementation with multiple substrate fatty acid oxidation measurements","pmids":["24333844"],"confidence":"High","gaps":["Whether CoA-ester is cleaved during transport not resolved here","Quantitative transport kinetics not measured"]},{"year":2014,"claim":"Linked ABCD3 loss to human disease, showing it is essential for peroxisomal import of branched-chain fatty acids and C27 bile acid intermediates.","evidence":"Patient with truncating p.Y635NfsX1 mutation, fibroblast and plasma biochemistry, and Abcd3-/- mice with phytol loading and bile acid profiling","pmids":["25168382"],"confidence":"High","gaps":["Spectrum of clinical phenotype across patients not defined","Residual transport by other ABCDs not fully quantified"]},{"year":2018,"claim":"Extended ABCD3's substrate scope to medium- and long-chain fatty acids and acylcarnitines, placing it in a peroxisomal pathway with HSD17B4.","evidence":"CRISPR-Cas9 single/double KO in HEK-293 cells with acylcarnitine profiling; Hsd17b4 KO mouse with CPT2 inhibition","pmids":["30540494"],"confidence":"High","gaps":["Relative contribution of this pathway in vivo unclear","Direct transport vs. downstream oxidation not separated"]},{"year":2015,"claim":"Pinpointed a short N-terminal motif (Ser5 indispensable) that suppresses TM1's ER-targeting signal, explaining how ABCD3 avoids ER mislocalization.","evidence":"Ser5Ala mutagenesis, chimeric signal-peptide constructs, crosslinking to cytosolic factors, and fluorescence localization","pmids":["26711236","20007743"],"confidence":"Medium","gaps":["Identity of the 50-kDa and 20-kDa cytosolic binding factors unknown","Mechanism of signal suppression not structurally defined"]},{"year":2024,"claim":"Identified post-targeting regulation of ABCD3 abundance, showing p97/VCP with UBXD8/FAF2 limit ubiquitination of ABCD3 to suppress pexophagy.","evidence":"Quantitative proteomics, ubiquitination assays, p97/UBXD8/FAF2 depletion, and rescue by autophagy-protein depletion or USP30 overexpression","pmids":["bio_10.1101_2024.09.24.614749","39929145"],"confidence":"Medium","gaps":["Ubiquitin ligase modifying ABCD3 not identified","Whether ABCD3 ubiquitination is the direct pexophagy signal not fully resolved","One source is a preprint"]},{"year":2025,"claim":"Provided the structural mechanism of transport, showing substrate binding closes the nucleotide-binding domains to activate ATPase.","evidence":"Cryo-EM of apo (3.33 Å) and phytanoyl-CoA-bound (3.13 Å) human ABCD3 with biochemical ATPase assays (preprint)","pmids":["bio_10.1101_2025.05.21.655323"],"confidence":"High","gaps":["Outward-open/release state not captured","Lipid bilayer dependence of cycle not defined","Not yet peer-reviewed"]},{"year":null,"claim":"How ABCD3 ubiquitination is enzymatically written and read to trigger pexophagy, and the identity of the cytosolic factors that direct its peroxisomal targeting, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["E3 ligase for ABCD3 unknown","Cytosolic ER-suppression factors uncharacterized","Full transport cycle states incomplete"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140657","term_label":"ATP-dependent activity","supporting_discovery_ids":[0,4,7]},{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[1,2,3]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[2,0]}],"localization":[{"term_id":"GO:0005777","term_label":"peroxisome","supporting_discovery_ids":[1,2,8,10]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[10,11]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,2,3]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[13,14]}],"complexes":["ABCD3 homodimer","ABCD1-ABCD3 heterodimer"],"partners":["ABCD1","PEX19","PEX2","VCP","FAF2","USP30","INTS7","HSD17B4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P28288","full_name":"ATP-binding cassette sub-family D member 3","aliases":["70 kDa peroxisomal membrane protein","PMP70"],"length_aa":659,"mass_kda":75.5,"function":"Broad substrate specificity ATP-dependent transporter of the ATP-binding cassette (ABC) family that catalyzes the transport of long-chain fatty acids (LCFA)-CoA, dicarboxylic acids-CoA, long-branched-chain fatty acids-CoA and bile acids from the cytosol to the peroxisome lumen for beta-oxydation (PubMed:11248239, PubMed:24333844, PubMed:25168382, PubMed:29397936). Has fatty acyl-CoA thioesterase and ATPase activities (PubMed:29397936). Probably hydrolyzes fatty acyl-CoAs into free fatty acids prior to their ATP-dependent transport into peroxisomes (By similarity). Thus, play a role in regulation of LCFAs and energy metabolism namely, in the degradation and biosynthesis of fatty acids by beta-oxidation (PubMed:24333844, PubMed:25944712)","subcellular_location":"Peroxisome membrane","url":"https://www.uniprot.org/uniprotkb/P28288/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/ABCD3","classification":"Not Classified","n_dependent_lines":25,"n_total_lines":1208,"dependency_fraction":0.020695364238410598},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CALM1","stoichiometry":0.2},{"gene":"CALM2","stoichiometry":0.2},{"gene":"CALM3","stoichiometry":0.2},{"gene":"PEX3","stoichiometry":0.2},{"gene":"RAB2A","stoichiometry":0.2},{"gene":"SAE1","stoichiometry":0.2},{"gene":"UBA1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/ABCD3","total_profiled":1310},"omim":[{"mim_id":"621446","title":"OCULOPHARYNGODISTAL MYOPATHY 5; OPDM5","url":"https://www.omim.org/entry/621446"},{"mim_id":"616278","title":"BILE ACID SYNTHESIS DEFECT, CONGENITAL, 5; CBAS5","url":"https://www.omim.org/entry/616278"},{"mim_id":"614593","title":"MEIOSIS REGULATOR AND mRNA STABILITY FACTOR 1; MARF1","url":"https://www.omim.org/entry/614593"},{"mim_id":"614362","title":"ACYL-CoA SYNTHETASE, BUBBLEGUM FAMILY, MEMBER 1; ACSBG1","url":"https://www.omim.org/entry/614362"},{"mim_id":"609501","title":"TUDOR AND KH DOMAINS-CONTAINING PROTEIN; TDRKH","url":"https://www.omim.org/entry/609501"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Peroxisomes","reliability":"Enhanced"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"liver","ntpm":118.4}],"url":"https://www.proteinatlas.org/search/ABCD3"},"hgnc":{"alias_symbol":["PMP70","ZWS2"],"prev_symbol":["PXMP1"]},"alphafold":{"accession":"P28288","domains":[{"cath_id":"-","chopping":"226-403","consensus_level":"medium","plddt":86.3976,"start":226,"end":403},{"cath_id":"3.40.50.300","chopping":"431-648","consensus_level":"high","plddt":91.6647,"start":431,"end":648}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P28288","model_url":"https://alphafold.ebi.ac.uk/files/AF-P28288-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P28288-F1-predicted_aligned_error_v6.png","plddt_mean":82.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=ABCD3","jax_strain_url":"https://www.jax.org/strain/search?query=ABCD3"},"sequence":{"accession":"P28288","fasta_url":"https://rest.uniprot.org/uniprotkb/P28288.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P28288/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P28288"}},"corpus_meta":[{"pmid":"30540494","id":"PMC_30540494","title":"Peroxisomes can oxidize medium- and long-chain fatty acids through a pathway involving ABCD3 and HSD17B4.","date":"2018","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/30540494","citation_count":103,"is_preprint":false},{"pmid":"25168382","id":"PMC_25168382","title":"A novel bile acid biosynthesis defect due to a deficiency of peroxisomal ABCD3.","date":"2014","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/25168382","citation_count":95,"is_preprint":false},{"pmid":"12111378","id":"PMC_12111378","title":"Catalog of 605 single-nucleotide polymorphisms (SNPs) among 13 genes encoding human ATP-binding cassette transporters: ABCA4, ABCA7, ABCA8, ABCD1, ABCD3, ABCD4, ABCE1, ABCF1, ABCG1, ABCG2, ABCG4, ABCG5, and ABCG8.","date":"2002","source":"Journal of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/12111378","citation_count":95,"is_preprint":false},{"pmid":"24333844","id":"PMC_24333844","title":"A role for the human peroxisomal half-transporter ABCD3 in the oxidation of dicarboxylic acids.","date":"2013","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/24333844","citation_count":84,"is_preprint":false},{"pmid":"12176987","id":"PMC_12176987","title":"ATP binding/hydrolysis by and phosphorylation of peroxisomal ATP-binding cassette proteins PMP70 (ABCD3) and adrenoleukodystrophy protein (ABCD1).","date":"2002","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12176987","citation_count":51,"is_preprint":false},{"pmid":"17609205","id":"PMC_17609205","title":"Live cell FRET microscopy: homo- and heterodimerization of two human peroxisomal ABC transporters, the adrenoleukodystrophy protein (ALDP, ABCD1) and PMP70 (ABCD3).","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17609205","citation_count":42,"is_preprint":false},{"pmid":"15276650","id":"PMC_15276650","title":"Mouse liver PMP70 and ALDP: homomeric interactions prevail in vivo.","date":"2004","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/15276650","citation_count":42,"is_preprint":false},{"pmid":"16344115","id":"PMC_16344115","title":"Role of Pex19p in the targeting of PMP70 to peroxisome.","date":"2005","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/16344115","citation_count":41,"is_preprint":false},{"pmid":"11330039","id":"PMC_11330039","title":"The 70-kDa peroxisomal membrane protein (PMP70), an ATP-binding cassette transporter.","date":"2000","source":"Cell biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/11330039","citation_count":39,"is_preprint":false},{"pmid":"8583512","id":"PMC_8583512","title":"Localization of mRNAs for adrenoleukodystrophy and the 70 kDa peroxisomal (PMP70) proteins in the rat brain during post-natal development.","date":"1995","source":"Journal of neuroscience research","url":"https://pubmed.ncbi.nlm.nih.gov/8583512","citation_count":31,"is_preprint":false},{"pmid":"20661612","id":"PMC_20661612","title":"Identification of novel SNPs of ABCD1, ABCD2, ABCD3, and ABCD4 genes in patients with X-linked adrenoleukodystrophy (ALD) based on comprehensive resequencing and association studies with ALD phenotypes.","date":"2010","source":"Neurogenetics","url":"https://pubmed.ncbi.nlm.nih.gov/20661612","citation_count":28,"is_preprint":false},{"pmid":"34880777","id":"PMC_34880777","title":"INTS7-ABCD3 Interaction Stimulates the Proliferation and Osteoblastic Differentiation of Mouse Bone Marrow Mesenchymal Stem Cells by Suppressing Oxidative Stress.","date":"2021","source":"Frontiers in 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Japanese journal of clinical medicine","url":"https://pubmed.ncbi.nlm.nih.gov/8411712","citation_count":4,"is_preprint":false},{"pmid":"31230922","id":"PMC_31230922","title":"Initiation of the ABCD3-I algorithm for expediated evaluation of transient ischemic attack patients in an emergency department.","date":"2019","source":"The American journal of emergency medicine","url":"https://pubmed.ncbi.nlm.nih.gov/31230922","citation_count":4,"is_preprint":false},{"pmid":"26711236","id":"PMC_26711236","title":"The N-terminal motif of PMP70 suppresses cotranslational targeting to the endoplasmic reticulum.","date":"2015","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26711236","citation_count":4,"is_preprint":false},{"pmid":"39929145","id":"PMC_39929145","title":"Quality control of ABCD3 by the VCP-FAF2 complex suppresses excessive pexophagy.","date":"2025","source":"Autophagy","url":"https://pubmed.ncbi.nlm.nih.gov/39929145","citation_count":1,"is_preprint":false},{"pmid":"40668324","id":"PMC_40668324","title":"Mechanism of ABCD3 inhibiting colorectal cancer progression by regulating Wnt/β-catenin.","date":"2025","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/40668324","citation_count":0,"is_preprint":false},{"pmid":"40937863","id":"PMC_40937863","title":"A-to-I editing of miR-579-3p exacerbates neonatal hypoxic-ischemic brain injury via regulation of ABCD3-dependent lipid metabolism in astrocytes.","date":"2025","source":"Neurological research","url":"https://pubmed.ncbi.nlm.nih.gov/40937863","citation_count":0,"is_preprint":false},{"pmid":"30663969","id":"PMC_30663969","title":"TIA patients with higher ABCD3-I scores are prone to a higher incidence of intracranial stenosis, unstable carotid plaques and multiple-vessel involvement.","date":"2018","source":"Functional neurology","url":"https://pubmed.ncbi.nlm.nih.gov/30663969","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.05.21.655323","title":"Molecular mechanism of substrate transport by human peroxisomal ABCD3","date":"2025-05-27","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.21.655323","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.09.24.614749","title":"The p97-UBXD8 complex maintains peroxisome abundance by suppressing pexophagy","date":"2024-09-27","source":"bioRxiv","url":"https://doi.org/10.1101/2024.09.24.614749","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18422,"output_tokens":4801,"usd":0.063641,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12933,"output_tokens":3824,"usd":0.080132,"stage2_stop_reason":"end_turn"},"total_usd":0.143773,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2025,\n      \"finding\": \"Cryo-EM structures of full-length human ABCD3 in apo state (3.33 Å) and bound to phytanoyl-CoA (3.13 Å) reveal that substrate binding brings the two nucleotide-binding domains closer together, stimulating ATPase activity via a substrate-dependent conformational change. This provides a mechanistic basis for substrate-induced ATPase activation and the transport mechanism.\",\n      \"method\": \"Cryo-EM structure determination (apo and substrate-bound states) combined with biochemical ATPase activity assays\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — atomic-resolution cryo-EM structures in two states combined with biochemical ATPase assays in a single rigorous study; preprint not yet peer-reviewed but multiple orthogonal methods\",\n      \"pmids\": [\"bio_10.1101_2025.05.21.655323\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"ABCD3 is required for peroxisomal import and beta-oxidation of branched-chain fatty acids (e.g., pristanic acid) and C27 bile acid intermediates. Loss of ABCD3 (patient with truncating mutation p.Y635NfsX1 and Abcd3-/- mice) leads to accumulation of C27 bile acid intermediates and a bile acid biosynthesis defect, demonstrating ABCD3 is essential for the transport of these substrates into peroxisomes.\",\n      \"method\": \"Patient genetic analysis (homozygous deletion), biochemical analysis of patient fibroblasts and plasma, Abcd3 knockout mouse model with phytol loading and bile acid profiling\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — human patient loss-of-function combined with knockout mouse model, multiple biochemical readouts, replicated across two biological systems\",\n      \"pmids\": [\"25168382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"ABCD3 functions as a homodimer and preferentially transports hydrophilic substrates including long-chain unsaturated fatty acids, long branched-chain fatty acids, and long-chain dicarboxylic fatty acids (as CoA esters) into peroxisomes, with a distinct substrate specificity from ABCD1 and ABCD2. This was established by complementation of the yeast pxa1/pxa2Δ mutant and fatty acid oxidation measurements.\",\n      \"method\": \"Yeast complementation assay (pxa1/pxa2Δ mutant rescue) and fatty acid oxidation measurements with multiple substrates\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — functional complementation in yeast with multiple substrate specificity assays, single lab but two orthogonal methods\",\n      \"pmids\": [\"24333844\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ABCD3 and the D-bifunctional protein HSD17B4 are essential components of a peroxisomal pathway that can oxidize medium- and long-chain fatty acids (lauric and palmitic acid), including as acylcarnitines. CRISPR-generated ABCD3 KO in HEK-293 cells abolished residual peroxisomal oxidation of these fatty acids when mitochondrial beta-oxidation was inhibited.\",\n      \"method\": \"CRISPR-Cas9 knockout of ABCD3 (single and double KO) in HEK-293 cells, acylcarnitine profiling; Hsd17b4 KO mouse model with CPT2 inhibition\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — CRISPR KO with defined biochemical phenotype, in vitro and in vivo validation across multiple KO combinations\",\n      \"pmids\": [\"30540494\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ABCD3 (PMP70) binds ATP tightly in the absence of Mg2+, hydrolyzes it to ADP in the presence of Mg2+, and releases ADP to allow catalytic turnover. Additionally, PMP70 is phosphorylated at a tyrosine residue(s). ATP binding/hydrolysis and phosphorylation are involved in regulation of fatty acid transport into peroxisomes.\",\n      \"method\": \"Photoaffinity labeling with 8-azido-[α-32P]ATP and 8-azido-[γ-32P]ATP, Mg2+-dependent hydrolysis assays, vanadate-trapping experiments, immunoprecipitation from rat liver peroxisomes\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — biochemical assays on native peroxisomes, multiple nucleotide analogs tested, but single lab study\",\n      \"pmids\": [\"12176987\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"ABCD3 (PMP70) forms homodimers in living cells, and also forms heterodimers with ALDP (ABCD1) in vivo. ALDP homodimers predominate. The last 87 C-terminal amino acids of ALDP are the primary domain mediating these interactions, with the N-terminal transmembrane region providing additional stabilization of ALDP homodimers.\",\n      \"method\": \"FRET microscopy in intact living cells using fluorescently tagged constructs, C-terminal deletion constructs, statistical analysis by probability distribution shift and Kolmogorov-Smirnov analysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — live-cell FRET with domain mapping by deletion constructs, two statistical methods, single lab\",\n      \"pmids\": [\"17609205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"In mouse liver, PMP70 (ABCD3) and ALDP (ABCD1) exist predominantly as homomeric complexes, with no evidence of heteromeric interactions or accessory proteins under normal expression conditions.\",\n      \"method\": \"Two-step purification of PMP70 protein complex from mouse liver to apparent homogeneity; preparative immunoprecipitation of ALDP complex; both analyzed by protein identification\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — purification to homogeneity combined with immunoprecipitation from native tissue, single lab\",\n      \"pmids\": [\"15276650\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"ATP binding and hydrolysis by PMP70 induce conformational changes in the protein specifically at the boundary between the transmembrane and nucleotide-binding domains, and in the helical domain between the Walker A and B motifs. MgATP or MgADP stabilizes a C-terminal 30-kDa fragment, while MgATP-γS protects the entire protein. The 30-kDa fragment forms a ~60 kDa complex consistent with PMP70 existing as a dimer on peroxisomal membranes.\",\n      \"method\": \"Limited trypsin digestion of rat liver peroxisomes pre-incubated with various nucleotides, followed by immunoblot analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — conformational analysis by limited proteolysis with multiple nucleotide conditions, single lab, single method\",\n      \"pmids\": [\"11883951\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Pex19p acts as a co-translational chaperone for PMP70 (ABCD3), binding it during translation to maintain solubility and proper conformation required for peroxisomal targeting. Two binding regions were identified: the N-terminal 61 amino acids and the region around TMD6. Deletion of either region prevented peroxisomal localization of GFP-PMP70 fusion proteins in CHO cells.\",\n      \"method\": \"In vitro translation system with purified Pex19p, co-immunoprecipitation, truncation/deletion constructs, GFP-fusion localization in CHO cells\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro binding combined with cell-based localization assays using multiple deletion constructs, single lab\",\n      \"pmids\": [\"16344115\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Efficient peroxisomal targeting of human PMP70 requires three targeting elements in the amino-terminal region: amino acids 61–80 (cytosolic loop), the first transmembrane domain, and the second transmembrane domain. PEX19 interactions are not required for targeting human PMP70 to peroxisomes and does not specifically bind the targeting elements.\",\n      \"method\": \"Truncation constructs and localization studies in cells; PEX19 interaction assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — cell-based targeting assays with multiple deletion constructs, PEX19 binding tested, single lab\",\n      \"pmids\": [\"11453642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The N-terminal 80-amino-acid segment of PMP70 is critical for suppressing an intrinsic ER-targeting function of TM1, enabling correct peroxisomal localization. Without the N80 segment, the full-length PMP70 localizes to the ER. The N80 segment alone targets to the outer mitochondrial membrane; combined with TM1-TM2, targeting is exclusively peroxisomal. Multiple organelle-targeting signals cooperate for correct peroxisomal membrane targeting.\",\n      \"method\": \"EGFP fusion constructs with N-terminal deletions expressed in COS cells; subcellular localization by fluorescence microscopy\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — multiple deletion/fusion constructs in live cells with fluorescence microscopy, single lab\",\n      \"pmids\": [\"20007743\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"A short 9-residue N-terminal motif in PMP70 (including Ser5 as indispensable) suppresses co-translational ER targeting by the TM1 signal sequence. Ser5Ala point mutation causes PMP70 to localize predominantly to the ER. The motif acts through binding 50-kDa and 20-kDa cytosolic proteins (crosslinking identified), functioning as an ER-targeting suppressor.\",\n      \"method\": \"Point mutagenesis (Ser5Ala), chimeric constructs with secretory signal peptide, protein crosslinking, subcellular localization by fluorescence microscopy\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — site-directed mutagenesis with localization readout and crosslinking to identify binding factors, single lab\",\n      \"pmids\": [\"26711236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"Overexpression of PMP70 (ABCD3) suppresses the peroxisome assembly defect caused by PEX2 mutations in CHO cells, restoring peroxisomal biogenesis (as measured by catalase latency, catalase localization, and VLCFA beta-oxidation). A mutant allele of PMP70 identified in a Zellweger syndrome patient failed to rescue, suggesting a functional interaction between PEX2 and PMP70 in the peroxisomal membrane.\",\n      \"method\": \"Expression of PMP70 in PEX2-deficient CHO cell clones; catalase latency assay, immunohistochemical localization of catalase, VLCFA beta-oxidation measurement\",\n      \"journal\": \"European journal of cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic suppression with multiple functional readouts, mutant allele control, single lab\",\n      \"pmids\": [\"9765053\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"The VCP-FAF2 complex (homolog of p97-UBXD8) prevents excessive pexophagy by regulating the accumulation of ubiquitinated ABCD3 on peroxisomal membranes. Loss of FAF2 leads to increased ubiquitination of ABCD3 and consequent autophagic degradation of peroxisomes.\",\n      \"method\": \"Quantitative proteomics, ubiquitination assays, autophagy rescue experiments, depletion of VCP/FAF2\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomic and functional evidence from two complementary studies (VCP-FAF2 and p97-UBXD8 papers), ubiquitination and autophagy readouts\",\n      \"pmids\": [\"39929145\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The p97-UBXD8 complex maintains peroxisome abundance by suppressing pexophagy. Loss of UBXD8 or inhibition of p97 increases ubiquitination of PMP70 (ABCD3) on peroxisomal membranes, triggering autophagic peroxisome degradation that can be rescued by depleting key autophagy proteins or overexpressing the deubiquitylase USP30.\",\n      \"method\": \"Quantitative proteomics, UBXD8/p97 depletion, ubiquitination assays, rescue by autophagy protein depletion and USP30 overexpression\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (proteomics, ubiquitination, genetic rescue), preprint not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2024.09.24.614749\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Knockdown of PMP70 (ABCD3) in rat C6 glial cells impairs peroxisomal beta-oxidation and causes oxidative stress (increased nitric oxide, superoxide, and lipid peroxidation products) and production of pro-inflammatory cytokines (TNFα, IFNγ, IL-12). The oxidative stress was shown to be downstream of IL-12 release rather than a direct consequence of PMP70 loss.\",\n      \"method\": \"Stable RNAi knockdown cell line (abcd3kd), measurement of oxidative stress markers, antioxidant enzyme activities, cytokine quantification, neutralizing antibody against IL-12\",\n      \"journal\": \"Neurochemistry international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — stable KD with multiple functional readouts and cytokine neutralization experiment establishing pathway order, single lab\",\n      \"pmids\": [\"18992293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"ABCD3 interacts with INTS7 (integrator complex subunit 7) in mouse bone marrow mesenchymal stem cells, and this interaction suppresses oxidative stress (ROS and γ-H2AX accumulation). Knockdown of either INTS7 or ABCD3 impairs BM-MSC proliferation, induces apoptosis, decreases osteoblastic differentiation, and accelerates adipogenic differentiation.\",\n      \"method\": \"Co-immunoprecipitation (INTS7-ABCD3 interaction), RNAi knockdown of INTS7 and ABCD3, ROS measurement, differentiation assays (Alizarin Red S, Oil Red O staining)\",\n      \"journal\": \"Frontiers in physiology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP plus KD phenotype, single lab, limited mechanistic follow-up on the interaction itself\",\n      \"pmids\": [\"34880777\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"NEGATIVE FINDING: The major Mg2+-ATPases induced in rat liver peroxisomes by clofibrate are not associated with PMP70 (ABCD3), as demonstrated by proteinase K sensitivity differences, failure of co-immunoprecipitation, different behavior on native PAGE, and separation by gel filtration chromatography.\",\n      \"method\": \"Proteinase K protection assay, immunoprecipitation, native PAGE, gel filtration chromatography from rat liver peroxisomes\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — four orthogonal negative methods consistently excluding association, single lab\",\n      \"pmids\": [\"1295880\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"ABCD3 (PMP70) is a half-ABC transporter that homodimerizes in the peroxisomal membrane, uses ATP hydrolysis (stimulated by substrate binding and driven by apposition of nucleotide-binding domains as revealed by cryo-EM) to transport CoA thioesters of branched-chain fatty acids, very long-chain fatty acids, dicarboxylic acids, and C27 bile acid intermediates from the cytosol into peroxisomes; its correct peroxisomal targeting depends on N-terminal suppression of an intrinsic ER-targeting signal (with Pex19p acting as a co-translational chaperone in some contexts), and its peroxisomal abundance is regulated by VCP/p97-FAF2/UBXD8-mediated control of ubiquitin-triggered pexophagy.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"ABCD3 (PMP70) is a peroxisomal half-ABC transporter that imports CoA-thioesters of fatty acids into peroxisomes to feed beta-oxidation, functioning as a homodimer with substrate specificity distinct from its paralogs ABCD1/ABCD2 [#2, #5]. Its substrate range spans long-chain unsaturated, branched-chain, and dicarboxylic fatty acids as well as medium- and long-chain species, and in patients and Abcd3-null mice its loss blocks peroxisomal handling of pristanic acid and C27 bile acid intermediates, causing a bile acid biosynthesis defect [#1, #2, #3]. Mechanistically, ABCD3 binds ATP and hydrolyzes it in a Mg2+-dependent manner with conformational changes at the transmembrane/nucleotide-binding domain interface, and cryo-EM of apo and phytanoyl-CoA-bound states shows that substrate binding draws the two nucleotide-binding domains together to stimulate ATPase activity [#0, #4, #7]. Correct delivery to the peroxisomal membrane depends on an N-terminal segment that suppresses an intrinsic ER-targeting signal in the first transmembrane domain, with a 9-residue motif (Ser5 indispensable) acting through cytosolic factors; without it, ABCD3 mislocalizes to the ER [#10, #11]. Its peroxisomal abundance is controlled by VCP/p97 together with FAF2/UBXD8, which limit ubiquitination of ABCD3 and thereby suppress its capacity to trigger pexophagy [#13, #14].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Established that the clofibrate-induced peroxisomal Mg2+-ATPase activity is not attributable to PMP70, separating the transporter from a confounding ATPase and focusing later mechanistic work on ABCD3 itself.\",\n      \"evidence\": \"Proteinase K protection, immunoprecipitation, native PAGE, and gel filtration of rat liver peroxisomes\",\n      \"pmids\": [\"1295880\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define ABCD3's own catalytic activity\", \"Identity of the induced ATPases left open\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Showed a functional interplay between PMP70 and the biogenesis factor PEX2, hinting the transporter participates in membrane assembly beyond pure transport.\",\n      \"evidence\": \"Overexpression suppression of PEX2-deficient CHO defect; catalase latency, localization, and VLCFA beta-oxidation readouts with a Zellweger mutant allele control\",\n      \"pmids\": [\"9765053\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of PEX2-PMP70 interaction not resolved\", \"Overexpression suppression may not reflect physiological role\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Defined ABCD3 as a genuine ATP-binding/hydrolyzing transporter, answering whether PMP70 has intrinsic nucleotide-handling catalytic turnover.\",\n      \"evidence\": \"Photoaffinity ATP labeling, Mg2+-dependent hydrolysis and vanadate-trapping on rat liver peroxisomes; limited proteolysis mapping nucleotide-induced conformational changes\",\n      \"pmids\": [\"12176987\", \"11883951\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Substrate-dependence of ATPase not yet addressed\", \"Functional role of tyrosine phosphorylation unresolved\", \"Single-lab native-membrane assays\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Addressed how PMP70 reaches peroxisomes versus the ER, identifying targeting determinants and a chaperone, though the requirement for PEX19 was disputed across studies.\",\n      \"evidence\": \"In vitro translation/Co-IP with Pex19p and GFP-fusion deletion localization (CHO); separately, truncation targeting assays finding PEX19 dispensable\",\n      \"pmids\": [\"16344115\", \"11453642\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Conflicting conclusions on PEX19 requirement\", \"Cytosolic factors mediating targeting not identified at this stage\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Resolved the oligomeric state, showing ABCD3 forms homodimers in living cells and can heterodimerize with ABCD1, establishing the functional transport unit.\",\n      \"evidence\": \"Live-cell FRET with fluorescent constructs, C-terminal deletion mapping, and statistical distribution analysis; corroborated by native-tissue purification favoring homomers\",\n      \"pmids\": [\"17609205\", \"15276650\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological significance of ABCD1 heterodimers unclear\", \"Stoichiometry under transport conditions not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined ABCD3 substrate specificity, establishing it transports long-chain unsaturated, branched-chain, and dicarboxylic fatty acyl-CoAs distinct from ABCD1/ABCD2.\",\n      \"evidence\": \"Yeast pxa1/pxa2\\u0394 complementation with multiple substrate fatty acid oxidation measurements\",\n      \"pmids\": [\"24333844\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CoA-ester is cleaved during transport not resolved here\", \"Quantitative transport kinetics not measured\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Linked ABCD3 loss to human disease, showing it is essential for peroxisomal import of branched-chain fatty acids and C27 bile acid intermediates.\",\n      \"evidence\": \"Patient with truncating p.Y635NfsX1 mutation, fibroblast and plasma biochemistry, and Abcd3-/- mice with phytol loading and bile acid profiling\",\n      \"pmids\": [\"25168382\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Spectrum of clinical phenotype across patients not defined\", \"Residual transport by other ABCDs not fully quantified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Extended ABCD3's substrate scope to medium- and long-chain fatty acids and acylcarnitines, placing it in a peroxisomal pathway with HSD17B4.\",\n      \"evidence\": \"CRISPR-Cas9 single/double KO in HEK-293 cells with acylcarnitine profiling; Hsd17b4 KO mouse with CPT2 inhibition\",\n      \"pmids\": [\"30540494\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contribution of this pathway in vivo unclear\", \"Direct transport vs. downstream oxidation not separated\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Pinpointed a short N-terminal motif (Ser5 indispensable) that suppresses TM1's ER-targeting signal, explaining how ABCD3 avoids ER mislocalization.\",\n      \"evidence\": \"Ser5Ala mutagenesis, chimeric signal-peptide constructs, crosslinking to cytosolic factors, and fluorescence localization\",\n      \"pmids\": [\"26711236\", \"20007743\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the 50-kDa and 20-kDa cytosolic binding factors unknown\", \"Mechanism of signal suppression not structurally defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified post-targeting regulation of ABCD3 abundance, showing p97/VCP with UBXD8/FAF2 limit ubiquitination of ABCD3 to suppress pexophagy.\",\n      \"evidence\": \"Quantitative proteomics, ubiquitination assays, p97/UBXD8/FAF2 depletion, and rescue by autophagy-protein depletion or USP30 overexpression\",\n      \"pmids\": [\"bio_10.1101_2024.09.24.614749\", \"39929145\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitin ligase modifying ABCD3 not identified\", \"Whether ABCD3 ubiquitination is the direct pexophagy signal not fully resolved\", \"One source is a preprint\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Provided the structural mechanism of transport, showing substrate binding closes the nucleotide-binding domains to activate ATPase.\",\n      \"evidence\": \"Cryo-EM of apo (3.33 \\u00c5) and phytanoyl-CoA-bound (3.13 \\u00c5) human ABCD3 with biochemical ATPase assays (preprint)\",\n      \"pmids\": [\"bio_10.1101_2025.05.21.655323\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Outward-open/release state not captured\", \"Lipid bilayer dependence of cycle not defined\", \"Not yet peer-reviewed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How ABCD3 ubiquitination is enzymatically written and read to trigger pexophagy, and the identity of the cytosolic factors that direct its peroxisomal targeting, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"E3 ligase for ABCD3 unknown\", \"Cytosolic ER-suppression factors uncharacterized\", \"Full transport cycle states incomplete\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140657\", \"supporting_discovery_ids\": [0, 4, 7]},\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [1, 2, 3]},\n      {\"term_id\": \"GO:0016887\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [2, 0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005777\", \"supporting_discovery_ids\": [1, 2, 8, 10]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [10, 11]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 2, 3]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [13, 14]}\n    ],\n    \"complexes\": [\"ABCD3 homodimer\", \"ABCD1-ABCD3 heterodimer\"],\n    \"partners\": [\"ABCD1\", \"PEX19\", \"PEX2\", \"VCP\", \"FAF2\", \"USP30\", \"INTS7\", \"HSD17B4\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":5,"faith_pct":80.0}}