{"gene":"SLC27A2","run_date":"2026-06-10T07:46:32","timeline":{"discoveries":[{"year":2010,"finding":"FATP2 is a multifunctional protein with subcellular localization-dependent activity: in mouse liver, only a minor fraction localizes to peroxisomes where it contributes to ~50% of peroxisomal very long-chain acyl-CoA synthetase (VLACS) activity, while total hepatic VLACS activity is not significantly affected by FATP2 loss; in contrast, liver-specific FATP2 knockdown reduced long-chain fatty acid (LCFA) uptake by 40%, indicating that FATP2's primary hepatic role is as a plasma membrane-associated LCFA transporter rather than a peroxisomal enzyme.","method":"Liver-specific shRNA knockdown via AAV8, subcellular fractionation, VLACS activity assays, radiolabeled fatty acid uptake assays in mice","journal":"American journal of physiology. Endocrinology and metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (fractionation, enzyme activity, uptake assay, in vivo knockdown) in a single rigorous study with functional consequence clearly defined","pmids":["20530735"],"is_preprint":false},{"year":2011,"finding":"In human hepatoma cells (HuH7, HepG2), FATP2 localizes to the endoplasmic reticulum (not plasma membrane); overexpression of FATP2 highly increases acyl-CoA synthetase activity and uptake of both radiolabeled oleic acid and fluorescent fatty acid analogue (BODIPY-C12), with FATP2 showing the highest effect on fatty acid uptake among the transporters tested, suggesting it drives uptake indirectly through esterification (vectorial acylation).","method":"Double immunofluorescence co-localization with ER markers, overexpression, ACS activity assay, [3H]-oleic acid uptake, FACS-based BODIPY-C12 uptake quantification","journal":"International journal of medical sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods in a single lab; localization and functional uptake data consistent but independent replication not reported","pmids":["22022213"],"is_preprint":false},{"year":2013,"finding":"FATP2 has dual function in fatty acid transport and activation: it can partner with long-chain acyl-CoA synthetases (ACSLs) to generate LCFA-CoAs (e.g., C16:0-CoA, C18:3-CoA) through vectorial acylation, while its intrinsic very long-chain acyl-CoA synthetase activity directly generates C20:4-CoA and C22:6-CoA; FATP2 expression also alters intracellular trafficking of exogenous fatty acids into phosphatidic acid and specific phospholipid classes (PC, PE, PI, PS) in a fatty acid species-selective manner.","method":"Stable isotopically labeled fatty acids (tracer), mass spectrometry-based lipidomics, overexpression in cells","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — isotope tracer with MS, single lab, multiple fatty acid species tested with distinct profiles","pmids":["24113382"],"is_preprint":false},{"year":2009,"finding":"Human FATP2-mediated fatty acid transport can be selectively inhibited by small molecule compounds identified in a high-throughput screen using yeast expressing human FATP2; five representative compounds inhibited LCFA uptake with low-micromolar IC50 in FATP2-expressing Caco-2 and HepG2 cells but not in 3T3-L1 adipocytes (which lack FATP2), with no effect on long-chain acyl-CoA synthetase activity, glucose transport, or cell viability, demonstrating that fatty acid transport and activation can be pharmacologically dissociated.","method":"High-throughput screen in yeast expressing human FATP2, fluorescent fatty acid uptake assay (BODIPY-C12), IC50 determination in human cell lines, TEER, glucose transport assay, cell viability","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional screening with mechanistic follow-up in multiple cell lines, single lab, orthogonal assays to distinguish transport from synthetase activity","pmids":["19913517"],"is_preprint":false},{"year":2016,"finding":"A naturally occurring splice variant of FATP2, FATP2b (lacking exon 3), retains full fatty acid transport function but completely lacks acyl-CoA synthetase activity; use of this variant in inhibitor screens identified two compounds, Lipofermata and Grassofermata, as effective fatty acid transport inhibitors both in vitro and in vivo in mouse models, demonstrating that transport and synthetase activities are separable functions of FATP2.","method":"Splice variant characterization, enzymatic activity assays, fatty acid uptake assays, in vitro and in vivo inhibitor studies in mouse models","journal":"MedChemComm","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — use of endogenous separation-of-function variant with functional assays; in vitro and in vivo validation; single lab","pmids":["27446528"],"is_preprint":false},{"year":2017,"finding":"FATP2 (encoded by Slc27a2) is expressed exclusively in kidney proximal tubule epithelial cells along the apical but not basolateral membrane; Slc27a2 knockout mice are protected from proteinuria-induced tubular injury, and Slc27a2-null proximal tubules and FATP2 shRNA-treated proximal tubule cell lines show significantly reduced NEFA uptake and reduced palmitate-induced apoptosis, establishing FATP2 as a major apical proximal tubule NEFA transporter that mediates lipoapoptosis.","method":"Immunolocalization, mRNA/protein expression, Slc27a2 knockout mouse model, ex vivo microperfusion, in vitro shRNA knockdown, apoptosis assay, lipidated albumin-induced proteinuria model","journal":"Journal of the American Society of Nephrology : JASN","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (KO mouse, microperfusion, shRNA knockdown, localization) across in vivo and in vitro systems; clear mechanistic and phenotypic readouts","pmids":["28993506"],"is_preprint":false},{"year":2020,"finding":"In the aged tumor microenvironment, aged dermal fibroblasts secrete increased neutral lipids (especially ceramides); melanoma cells exposed to this lipid secretome upregulate FATP2, which mediates increased lipid uptake; FATP2-dependent lipid accumulation supports mitochondrial metabolism and drives resistance to BRAF/MEK inhibition, and FATP2 blockade overcomes this age-related resistance in animal models.","method":"Co-culture experiments, lipidomic analysis, FATP2 overexpression/knockdown, lipid uptake assays, mitochondrial metabolism assays, in vivo tumor models with targeted therapy","journal":"Cancer discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple functional assays (uptake, metabolic, in vivo) in single lab; mechanistic link between FATP2-mediated lipid uptake and therapy resistance established","pmids":["32499221"],"is_preprint":false},{"year":2020,"finding":"Deletion of FATP2 in mouse liver shifts the transcriptomic landscape, upregulating PPARα-regulated genes involved in fatty acid degradation, peroxisome biogenesis, and fatty acid synthesis; targeted metabolomics shows increases in C16:0, C16:1, C18:1 fatty acids and lipid mediators (lipoxin A4, prostaglandin J2) and decreased 20-HETE, indicating FATP2 provides PPARα with specific proximal ligands and broadly governs hepatic lipid metabolism.","method":"FATP2-null (Fatp2-/-) mouse model, RNA-Seq transcriptomics, targeted metabolomics, RT-qPCR validation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KO mouse with RNA-Seq and metabolomics, single lab, multiple orthogonal readouts; PPARα link inferred from transcriptomics rather than direct binding assay","pmids":["32188695"],"is_preprint":false},{"year":2023,"finding":"Arachidonic acid activates the NLRP3 inflammasome in myeloid-derived suppressor cells (MDSCs) specifically through FATP2; FATP2-mediated arachidonic acid uptake causes mitochondrial dysfunction and enhanced ROS production, which bridges lipid uptake to NLRP3 activation; activated MDSCs then stimulate CD4+ T cells to produce IL-17, promoting post-transplant tumor recurrence; blockade of FATP2 (Lipofermata) inhibits this entire axis.","method":"Lipid uptake receptor screening, mouse fatty liver ischemia-reperfusion injury model with tumor recurrence, FATP2 inhibitor (Lipofermata) treatment, NLRP3/ROS/IL-17 mechanistic assays in vitro and in vivo, clinical cohort validation","journal":"JHEP reports : innovation in hepatology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic pathway established by screening, in vivo model, and in vitro mechanistic follow-up; single lab but multiple orthogonal methods","pmids":["37916155"],"is_preprint":false},{"year":2023,"finding":"FATP2 physically interacts with ACSL1 (long-chain acyl-CoA synthetase 1) in NSCLC cells, as demonstrated by Co-IP; FATP2 knockdown combined with ACSL1 overexpression further inhibits cell proliferation, lipid deposition, and promotes fatty acid decomposition compared to either alone, indicating FATP2 regulates lipid metabolism and cancer cell proliferation through functional interaction with ACSL1.","method":"Co-immunoprecipitation (Co-IP), siRNA knockdown, pcDNA-ACSL1 overexpression, cell proliferation assay, lipid deposition assay, ER stress markers","journal":"Tissue & cell","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single Co-IP in one lab; mechanistic follow-up limited to cell-based assays without structural or biochemical reconstitution","pmids":["37172427"],"is_preprint":false},{"year":2023,"finding":"NRF2 directly transcriptionally activates FATP2 in the context of valproic acid (VPA)-induced hepatic steatosis: VPA binds to Cys288 and Arg415 of KEAP1, promoting autophagic KEAP1 degradation, releasing NRF2 to translocate to the nucleus where it activates FATP2 transcription, thereby enhancing fatty acid uptake and driving steatosis; this was confirmed by chromatin immunoprecipitation and dual-luciferase reporter assays, and FATP2 knockout abrogated NRF2-driven steatosis.","method":"ChIP assay, dual-luciferase reporter assay, NRF2 overexpression/knockout mice (AAV and CRISPR/Cas9), FATP2 knockout mice (homologous recombination), site-directed mutagenesis of KEAP1 binding sites, in vivo VPA treatment","journal":"Theranostics","confidence":"High","confidence_rationale":"Tier 1 / Strong — ChIP and luciferase reporter directly establish NRF2→FATP2 transcriptional axis; multiple genetic models (OE, KO) with in vivo validation; multiple orthogonal methods","pmids":["40303331"],"is_preprint":false},{"year":2024,"finding":"Loss of the epoxygenase Cyp2c44 (and reduced EET levels) leads to increased plasma membrane localization of FATP2 in hepatocytes, which is associated with increased total unsaturated fatty acids and diacylglycerol (DAG) accumulation, activation of PKCδ at the plasma membrane, IRS-1 serine phosphorylation, and impaired insulin signaling; treatment with the EET analog EET-A in Cyp2c44-/- HFD-fed mice decreased plasma membrane FATP2 and PKCδ levels with improved glucose tolerance, placing FATP2 membrane localization downstream of EET signaling and upstream of the DAG/PKCδ/IRS-1 axis.","method":"Cyp2c44-/- mouse model, subcellular fractionation, PKCδ inhibitor treatment, EET-A analog treatment, glucose tolerance test, lipidomics, immunoblotting","journal":"Diabetes","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic model with pharmacological rescue, subcellular fractionation, and lipidomics; single lab; pathway placement via epistasis-like approach","pmids":["38743615"],"is_preprint":false},{"year":2024,"finding":"FATP2 expression is upregulated during osteoclast (OC) differentiation and in bone marrow of HFD-fed mice; FATP2 siRNA or Lipofermata inhibition significantly suppresses OC differentiation with minimal effect on osteoblasts; RNA-seq shows Lipofermata reduces fatty acid β-oxidation, energy metabolism, and ROS production in OCs; in vivo Lipofermata treatment rescues bone loss in LPS-induced and ovariectomy models by inhibiting OC differentiation, establishing FATP2 as a regulator of osteoclastogenesis through fatty acid uptake and energy/ROS metabolism.","method":"siRNA knockdown, specific inhibitor (Lipofermata), RNA-seq, in vivo mouse models (LPS-induced and ovariectomy), bone mass measurement, ROS assays","journal":"Journal of bone and mineral research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vivo and in vitro models with RNA-seq mechanistic follow-up; single lab","pmids":["38477781"],"is_preprint":false},{"year":2024,"finding":"CEACAM6 promotes SLC27A2/FATP2 protein stability by interacting with both SLC27A2 and the deubiquitinase USP29; CEACAM6 facilitates USP29-mediated deubiquitination of SLC27A2, thereby upregulating fatty acid uptake and FAO in gastric cancer cells; pharmacological inhibition of SLC27A2 attenuates the tumor-initiating ability of CEACAM6-positive gastric cancer.","method":"Co-immunoprecipitation (protein-protein interaction), deubiquitination assay, SLC27A2 inhibitor (Lipofermata), in vitro and in vivo tumor models","journal":"Cancer gene therapy","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP demonstrates interaction; deubiquitination assay supports mechanism but single lab, limited replication","pmids":["39562695"],"is_preprint":false},{"year":2025,"finding":"In pancreatic islets, FATP2 expression is restricted to α-cells; FATP2 knockout or pharmacological inhibition (Lipofermata) in db/db mice and isolated human islets increases GLP-1-positive α-cell mass and stimulates GLP-1 secretion from α-cells; this α-cell-derived GLP-1 promotes paracrine insulin secretion from β-cells, reducing plasma glucose; the glucose-lowering effect is abrogated by GLP-1 receptor antagonism (exendin[9-39]), confirming that FATP2 inhibition acts through α-cell GLP-1 secretion rather than enteroendocrine pathways.","method":"FATP2 global KO mouse (db/db background), small molecule inhibitor (Lipofermata), GLP-1 receptor antagonist (exendin[9-39]), immunolocalization, αTC1-6 cell and human islet assays, oral vs. IP glucose challenge, mRNA co-expression analysis","journal":"bioRxiv : the preprint server for biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (KO, pharmacological, cell, human islet); preprint, not yet peer-reviewed; strong mechanistic specificity via receptor antagonism rescue","pmids":["39975070"],"is_preprint":true},{"year":2023,"finding":"FATP2 homology model (validated by AlphaFold2 prediction and site-directed mutagenesis) was used to identify key residues for inhibitor binding; virtual screening identified two nanomolar IC50 inhibitors of FATP2-dependent fatty acid uptake and apoptosis in proximal tubule cells, providing structural insights into the FATP2 binding site.","method":"Homology modeling, AlphaFold2 structural prediction, site-directed mutagenesis, virtual docking, in vitro fatty acid uptake assay, apoptosis assay, molecular dynamics simulations","journal":"International journal of biological macromolecules","confidence":"Low","confidence_rationale":"Tier 3 / Weak — homology model rather than experimental structure; mutagenesis validates model but limited mechanistic depth; single lab","pmids":["37307967"],"is_preprint":false},{"year":2025,"finding":"FATP2 inhibition (Lipofermata) in human monocytes reduces LPS-induced inflammatory responses and decreases biosynthesis of arachidonic acid-derived lipid mediators (PGE2, TxB2), indicating FATP2-dependent arachidonic acid uptake supports eicosanoid production; conversely, in mature monocyte-derived macrophages, Lipofermata enhances LPS-induced cytokine production and induces cell death likely through inflammasome activation, demonstrating cell type-specific roles of FATP2 in inflammatory lipid metabolism.","method":"Lipofermata inhibitor treatment, LPS stimulation, cytokine measurement, lipidomics (lipid mediator profiling), cell death assays in human monocytes and macrophages","journal":"Immunology letters","confidence":"Low","confidence_rationale":"Tier 3 / Weak — pharmacological inhibitor only (no genetic knockdown), single lab, mechanistic interpretation relies on inhibitor selectivity","pmids":["41015393"],"is_preprint":false}],"current_model":"SLC27A2/FATP2 is a multifunctional, localization-dependent protein that functions as a long-chain fatty acid transporter (primarily at the plasma membrane) and as a peroxisomal very long-chain acyl-CoA synthetase; its transport activity drives vectorial acylation in partnership with ACSLs, it is transcriptionally regulated by NRF2, its plasma membrane localization is controlled by EET/Cyp2c44 signaling upstream of a DAG/PKCδ/IRS-1 insulin-resistance axis, it mediates lipoapoptosis in renal proximal tubules via apical NEFA uptake, it supports NLRP3 inflammasome activation in MDSCs via arachidonic acid uptake, and in pancreatic α-cells its inhibition promotes GLP-1 secretion and paracrine insulin release."},"narrative":{"mechanistic_narrative":"SLC27A2/FATP2 is a localization-dependent, bifunctional protein that couples cellular long-chain fatty acid (LCFA) uptake to fatty acid activation, governing tissue lipid metabolism and lipid-driven pathology [PMID:20530735, PMID:24113382]. Its two enzymatic activities are mechanistically separable: a transport function that drives LCFA uptake and an intrinsic very long-chain acyl-CoA synthetase activity that directly generates C20:4-CoA and C22:6-CoA, while partnering with long-chain acyl-CoA synthetases (ACSLs) to esterify shorter chains through vectorial acylation [PMID:20530735, PMID:24113382, PMID:37172427]. This dissociability is established by a naturally occurring splice variant (FATP2b) that retains transport but lacks synthetase activity and by small molecules (Lipofermata, Grassofermata) that block transport without affecting synthetase activity [PMID:19913517, PMID:27446528]. FATP2 abundance and membrane positioning are tightly regulated: NRF2 directly transactivates FATP2 to enhance fatty acid uptake and drive hepatic steatosis [PMID:40303331], and loss of the epoxygenase Cyp2c44 increases plasma membrane FATP2, promoting DAG accumulation, PKCδ activation, IRS-1 serine phosphorylation, and insulin resistance [PMID:38743615]. Through apical NEFA uptake in kidney proximal tubule epithelium, FATP2 mediates palmitate-induced lipoapoptosis and proteinuria-induced tubular injury [PMID:28993506]. FATP2-dependent fatty acid uptake also fuels disease-relevant programs in other tissues: it supports melanoma resistance to BRAF/MEK inhibition via mitochondrial metabolism [PMID:32499221], drives arachidonic-acid-triggered NLRP3 inflammasome activation in myeloid-derived suppressor cells [PMID:37916155], and promotes osteoclastogenesis through β-oxidation and ROS [PMID:38477781]. In pancreatic α-cells FATP2 inhibition increases GLP-1 secretion that paracrine-stimulates β-cell insulin release [PMID:39975070].","teleology":[{"year":2009,"claim":"Established that FATP2-mediated fatty acid transport could be pharmacologically separated from acyl-CoA synthetase activity, proving the two are distinct druggable functions.","evidence":"High-throughput screen in yeast expressing human FATP2 with follow-up uptake and synthetase assays in human cell lines","pmids":["19913517"],"confidence":"Medium","gaps":["Did not define the structural basis of transport vs. synthetase activity","Selectivity of inhibitors across other FATP family members not resolved"]},{"year":2010,"claim":"Resolved the long-standing ambiguity over FATP2's primary in vivo role by showing it acts mainly as a plasma membrane LCFA transporter rather than a peroxisomal VLACS enzyme in liver.","evidence":"Liver-specific AAV8 shRNA knockdown with subcellular fractionation, VLACS activity, and radiolabeled uptake assays in mice","pmids":["20530735"],"confidence":"High","gaps":["Did not establish how transport is mechanistically coupled to esterification","Peroxisomal contribution in other tissues unaddressed"]},{"year":2011,"claim":"Showed FATP2 can localize to the ER in human hepatoma cells and drives uptake indirectly through esterification, framing the vectorial acylation model.","evidence":"Immunofluorescence co-localization, overexpression, ACS activity and oleic acid/BODIPY-C12 uptake assays in HuH7/HepG2","pmids":["22022213"],"confidence":"Medium","gaps":["Localization conflicts with plasma-membrane role seen in liver—context dependence not reconciled","No independent replication reported"]},{"year":2013,"claim":"Defined the dual biochemical logic: FATP2 partners with ACSLs for LCFA-CoA generation while intrinsically activating very long-chain species, and reshapes fatty acid trafficking into specific phospholipid classes.","evidence":"Stable-isotope fatty acid tracing with MS-based lipidomics in overexpressing cells","pmids":["24113382"],"confidence":"Medium","gaps":["Direct physical ACSL partnership not demonstrated in this study","Species-selective trafficking mechanism unknown"]},{"year":2016,"claim":"Used an endogenous separation-of-function splice variant (FATP2b) to confirm transport and synthetase activities are genetically separable and validated transport-selective inhibitors in vivo.","evidence":"Splice variant characterization with enzymatic/uptake assays and in vitro/in vivo inhibitor studies in mice","pmids":["27446528"],"confidence":"Medium","gaps":["Physiological regulation of FATP2b splicing not defined","Structural determinant of the lost synthetase activity unmapped"]},{"year":2017,"claim":"Identified FATP2 as the apical proximal tubule NEFA transporter whose uptake drives lipoapoptosis, linking it causally to tubular injury.","evidence":"Slc27a2 knockout mice, ex vivo microperfusion, shRNA knockdown, and proteinuria model with apoptosis readouts","pmids":["28993506"],"confidence":"High","gaps":["Downstream apoptotic signaling from NEFA accumulation not detailed","Restriction of expression to proximal tubule mechanism unexplained"]},{"year":2020,"claim":"Connected FATP2-mediated lipid uptake to PPARα ligand provision and broad hepatic metabolic control, and to tumor lipid programming.","evidence":"Fatp2-/- mouse RNA-Seq and targeted metabolomics; melanoma co-culture, uptake, mitochondrial and in vivo therapy-resistance models","pmids":["32188695","32499221"],"confidence":"Medium","gaps":["PPARα ligand link inferred from transcriptomics, not direct binding","Direct FATP2 substrate driving therapy resistance not isolated"]},{"year":2023,"claim":"Placed FATP2 upstream of innate immune and proliferative lipid programs—arachidonic-acid-driven NLRP3 activation in MDSCs and ACSL1-coupled lipid metabolism in cancer cells.","evidence":"Lipid uptake screening, in vivo ischemia-reperfusion/tumor recurrence model with Lipofermata; Co-IP and knockdown/overexpression in NSCLC cells","pmids":["37916155","37172427"],"confidence":"Medium","gaps":["ACSL1 interaction rests on a single Co-IP without reciprocal validation","How arachidonic acid uptake mechanistically triggers mitochondrial ROS not fully resolved"]},{"year":2023,"claim":"Provided a structural model of the FATP2 inhibitor binding site, enabling nanomolar inhibitor discovery.","evidence":"AlphaFold2-based homology model with site-directed mutagenesis, virtual screening, and uptake/apoptosis assays","pmids":["37307967"],"confidence":"Low","gaps":["Homology model, not an experimental structure","Limited mechanistic depth beyond mutagenesis validation"]},{"year":2023,"claim":"Identified the NRF2→FATP2 transcriptional axis as a driver of drug-induced hepatic steatosis, establishing direct transcriptional control of FATP2.","evidence":"ChIP and dual-luciferase reporter assays, NRF2 and FATP2 genetic mouse models, KEAP1 site-directed mutagenesis with VPA treatment","pmids":["40303331"],"confidence":"High","gaps":["Other transcriptional regulators of FATP2 not surveyed","Tissue scope of NRF2 control beyond liver unknown"]},{"year":2024,"claim":"Defined post-translational and localization control of FATP2—USP29/CEACAM6-mediated stabilization and EET/Cyp2c44 control of plasma membrane localization feeding the DAG/PKCδ/IRS-1 insulin-resistance axis.","evidence":"Co-IP and deubiquitination assays with tumor models; Cyp2c44-/- mice with fractionation, lipidomics, PKCδ inhibition and EET-A rescue","pmids":["39562695","38743615"],"confidence":"Medium","gaps":["CEACAM6/USP29 mechanism rests on Co-IP without reciprocal/structural validation","How EET signaling physically alters FATP2 trafficking is unknown"]},{"year":2024,"claim":"Extended FATP2's metabolic reach to osteoclastogenesis, where its fatty acid uptake fuels β-oxidation and ROS required for bone resorption.","evidence":"siRNA and Lipofermata inhibition, RNA-seq, and LPS-induced and ovariectomy bone-loss mouse models","pmids":["38477781"],"confidence":"Medium","gaps":["Direct lipid substrate driving osteoclast energy metabolism not identified","Specificity for osteoclasts over osteoblasts mechanism unexplained"]},{"year":2025,"claim":"Revealed an α-cell-specific FATP2 role whose inhibition increases GLP-1 secretion and paracrine β-cell insulin release, defining a glucose-lowering axis.","evidence":"FATP2 KO (db/db), Lipofermata, GLP-1 receptor antagonist rescue, αTC1-6 and human islet assays (preprint)","pmids":["39975070"],"confidence":"Medium","gaps":["Preprint, not yet peer-reviewed","How loss of α-cell FATP2 lipid uptake triggers GLP-1 secretion mechanistically unclear"]},{"year":null,"claim":"How FATP2 transport activity is mechanically coupled to acyl-CoA synthesis at the molecular level, and what determines its differential localization (plasma membrane vs. ER vs. peroxisome) across cell types, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No experimental high-resolution structure of FATP2","Determinants of cell-type-specific localization not defined","Direct biochemical reconstitution of FATP2-ACSL vectorial acylation lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005215","term_label":"transporter activity","supporting_discovery_ids":[0,1,3,4,5]},{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[0,2,4]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[1,2,6]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,5,11]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[1]},{"term_id":"GO:0005777","term_label":"peroxisome","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,2,7]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[0,5]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[8,16]}],"complexes":[],"partners":["ACSL1","CEACAM6","USP29"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O14975","full_name":"Long-chain fatty acid transport protein 2","aliases":["Arachidonate--CoA ligase","Fatty acid transport protein 2","FATP-2","Fatty-acid-coenzyme A ligase, very long-chain 1","Long-chain-fatty-acid--CoA ligase","Phytanate--CoA ligase","Solute carrier family 27 member 2","THCA-CoA ligase","Very long-chain acyl-CoA synthetase","VLACS","VLCS","Very long-chain-fatty-acid-CoA ligase"],"length_aa":620,"mass_kda":70.3,"function":"Mediates the import of long-chain fatty acids (LCFA) into the cell by facilitating their transport across cell membranes, playing an important role in hepatic fatty acid uptake (PubMed:10198260, PubMed:10749848, PubMed:11980911, PubMed:20530735, PubMed:22022213, PubMed:24269233). Also functions as an acyl-CoA ligase catalyzing the ATP-dependent formation of fatty acyl-CoA using LCFA and very-long-chain fatty acids (VLCFA) as substrates, which prevents fatty acid efflux from cells and might drive more fatty acid uptake (PubMed:10198260, PubMed:10749848, PubMed:11980911, PubMed:20530735, PubMed:22022213, PubMed:24269233). Plays a pivotal role in regulating available LCFA substrates from exogenous sources in tissues undergoing high levels of beta-oxidation or triglyceride synthesis (PubMed:20530735). Can also activate branched-chain fatty acids such as phytanic acid and pristanic acid (PubMed:10198260). May contribute to the synthesis of sphingosine-1-phosphate (PubMed:24269233). Does not activate C24 bile acids, cholate and chenodeoxycholate (PubMed:11980911). In vitro, activates 3-alpha,7-alpha,12-alpha-trihydroxy-5-beta-cholestanate (THCA), the C27 precursor of cholic acid deriving from the de novo synthesis from cholesterol (PubMed:11980911). However, it is not critical for THCA activation and bile synthesis in vivo (PubMed:20530735) Exhibits both long-chain fatty acids (LCFA) transport activity and acyl CoA synthetase towards very long-chain fatty acids (PubMed:10198260, PubMed:21768100). Shows a preference for generating CoA derivatives of n-3 fatty acids, which are preferentially trafficked into phosphatidylinositol (PubMed:21768100) Exhibits long-chain fatty acids (LCFA) transport activity but lacks acyl CoA synthetase towards very long-chain fatty acids","subcellular_location":"Endoplasmic reticulum membrane; Peroxisome membrane; Cell membrane; Microsome","url":"https://www.uniprot.org/uniprotkb/O14975/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/SLC27A2","classification":"Not Classified","n_dependent_lines":12,"n_total_lines":1208,"dependency_fraction":0.009933774834437087},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"HSP90B1","stoichiometry":0.2},{"gene":"SEC61B","stoichiometry":0.2},{"gene":"CCDC47","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/SLC27A2","total_profiled":1310},"omim":[{"mim_id":"614362","title":"ACYL-CoA SYNTHETASE, BUBBLEGUM FAMILY, MEMBER 1; ACSBG1","url":"https://www.omim.org/entry/614362"},{"mim_id":"604196","title":"SOLUTE CARRIER FAMILY 27 (FATTY ACID TRANSPORTER), MEMBER 6; SLC27A6","url":"https://www.omim.org/entry/604196"},{"mim_id":"604194","title":"SOLUTE CARRIER FAMILY 27 (FATTY ACID TRANSPORTER), MEMBER 4; SLC27A4","url":"https://www.omim.org/entry/604194"},{"mim_id":"604193","title":"SOLUTE CARRIER FAMILY 27 (FATTY ACID TRANSPORTER), MEMBER 3; SLC27A3","url":"https://www.omim.org/entry/604193"},{"mim_id":"603314","title":"SOLUTE CARRIER FAMILY 27 (FATTY ACID TRANSPORTER), MEMBER 5; SLC27A5","url":"https://www.omim.org/entry/603314"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"kidney","ntpm":147.1},{"tissue":"liver","ntpm":269.2}],"url":"https://www.proteinatlas.org/search/SLC27A2"},"hgnc":{"alias_symbol":["FATP2","hFACVL1","VLACS","VLCS","HsT17226","ACSVL1"],"prev_symbol":["FACVL1"]},"alphafold":{"accession":"O14975","domains":[{"cath_id":"3.40.50.980","chopping":"52-272","consensus_level":"high","plddt":95.1559,"start":52,"end":272},{"cath_id":"2.30.38.10","chopping":"367-481","consensus_level":"medium","plddt":94.0742,"start":367,"end":481},{"cath_id":"3.30.300.30","chopping":"485-616","consensus_level":"high","plddt":88.0905,"start":485,"end":616}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O14975","model_url":"https://alphafold.ebi.ac.uk/files/AF-O14975-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O14975-F1-predicted_aligned_error_v6.png","plddt_mean":92.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=SLC27A2","jax_strain_url":"https://www.jax.org/strain/search?query=SLC27A2"},"sequence":{"accession":"O14975","fasta_url":"https://rest.uniprot.org/uniprotkb/O14975.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O14975/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O14975"}},"corpus_meta":[{"pmid":"20530735","id":"PMC_20530735","title":"FATP2 is a hepatic fatty acid transporter and peroxisomal very long-chain acyl-CoA synthetase.","date":"2010","source":"American journal of physiology. 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reduced long-chain fatty acid (LCFA) uptake by 40%, indicating that FATP2's primary hepatic role is as a plasma membrane-associated LCFA transporter rather than a peroxisomal enzyme.\",\n      \"method\": \"Liver-specific shRNA knockdown via AAV8, subcellular fractionation, VLACS activity assays, radiolabeled fatty acid uptake assays in mice\",\n      \"journal\": \"American journal of physiology. Endocrinology and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (fractionation, enzyme activity, uptake assay, in vivo knockdown) in a single rigorous study with functional consequence clearly defined\",\n      \"pmids\": [\"20530735\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In human hepatoma cells (HuH7, HepG2), FATP2 localizes to the endoplasmic reticulum (not plasma membrane); overexpression of FATP2 highly increases acyl-CoA synthetase activity and uptake of both radiolabeled oleic acid and fluorescent fatty acid analogue (BODIPY-C12), with FATP2 showing the highest effect on fatty acid uptake among the transporters tested, suggesting it drives uptake indirectly through esterification (vectorial acylation).\",\n      \"method\": \"Double immunofluorescence co-localization with ER markers, overexpression, ACS activity assay, [3H]-oleic acid uptake, FACS-based BODIPY-C12 uptake quantification\",\n      \"journal\": \"International journal of medical sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods in a single lab; localization and functional uptake data consistent but independent replication not reported\",\n      \"pmids\": [\"22022213\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"FATP2 has dual function in fatty acid transport and activation: it can partner with long-chain acyl-CoA synthetases (ACSLs) to generate LCFA-CoAs (e.g., C16:0-CoA, C18:3-CoA) through vectorial acylation, while its intrinsic very long-chain acyl-CoA synthetase activity directly generates C20:4-CoA and C22:6-CoA; FATP2 expression also alters intracellular trafficking of exogenous fatty acids into phosphatidic acid and specific phospholipid classes (PC, PE, PI, PS) in a fatty acid species-selective manner.\",\n      \"method\": \"Stable isotopically labeled fatty acids (tracer), mass spectrometry-based lipidomics, overexpression in cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — isotope tracer with MS, single lab, multiple fatty acid species tested with distinct profiles\",\n      \"pmids\": [\"24113382\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Human FATP2-mediated fatty acid transport can be selectively inhibited by small molecule compounds identified in a high-throughput screen using yeast expressing human FATP2; five representative compounds inhibited LCFA uptake with low-micromolar IC50 in FATP2-expressing Caco-2 and HepG2 cells but not in 3T3-L1 adipocytes (which lack FATP2), with no effect on long-chain acyl-CoA synthetase activity, glucose transport, or cell viability, demonstrating that fatty acid transport and activation can be pharmacologically dissociated.\",\n      \"method\": \"High-throughput screen in yeast expressing human FATP2, fluorescent fatty acid uptake assay (BODIPY-C12), IC50 determination in human cell lines, TEER, glucose transport assay, cell viability\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional screening with mechanistic follow-up in multiple cell lines, single lab, orthogonal assays to distinguish transport from synthetase activity\",\n      \"pmids\": [\"19913517\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"A naturally occurring splice variant of FATP2, FATP2b (lacking exon 3), retains full fatty acid transport function but completely lacks acyl-CoA synthetase activity; use of this variant in inhibitor screens identified two compounds, Lipofermata and Grassofermata, as effective fatty acid transport inhibitors both in vitro and in vivo in mouse models, demonstrating that transport and synthetase activities are separable functions of FATP2.\",\n      \"method\": \"Splice variant characterization, enzymatic activity assays, fatty acid uptake assays, in vitro and in vivo inhibitor studies in mouse models\",\n      \"journal\": \"MedChemComm\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — use of endogenous separation-of-function variant with functional assays; in vitro and in vivo validation; single lab\",\n      \"pmids\": [\"27446528\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FATP2 (encoded by Slc27a2) is expressed exclusively in kidney proximal tubule epithelial cells along the apical but not basolateral membrane; Slc27a2 knockout mice are protected from proteinuria-induced tubular injury, and Slc27a2-null proximal tubules and FATP2 shRNA-treated proximal tubule cell lines show significantly reduced NEFA uptake and reduced palmitate-induced apoptosis, establishing FATP2 as a major apical proximal tubule NEFA transporter that mediates lipoapoptosis.\",\n      \"method\": \"Immunolocalization, mRNA/protein expression, Slc27a2 knockout mouse model, ex vivo microperfusion, in vitro shRNA knockdown, apoptosis assay, lipidated albumin-induced proteinuria model\",\n      \"journal\": \"Journal of the American Society of Nephrology : JASN\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (KO mouse, microperfusion, shRNA knockdown, localization) across in vivo and in vitro systems; clear mechanistic and phenotypic readouts\",\n      \"pmids\": [\"28993506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In the aged tumor microenvironment, aged dermal fibroblasts secrete increased neutral lipids (especially ceramides); melanoma cells exposed to this lipid secretome upregulate FATP2, which mediates increased lipid uptake; FATP2-dependent lipid accumulation supports mitochondrial metabolism and drives resistance to BRAF/MEK inhibition, and FATP2 blockade overcomes this age-related resistance in animal models.\",\n      \"method\": \"Co-culture experiments, lipidomic analysis, FATP2 overexpression/knockdown, lipid uptake assays, mitochondrial metabolism assays, in vivo tumor models with targeted therapy\",\n      \"journal\": \"Cancer discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple functional assays (uptake, metabolic, in vivo) in single lab; mechanistic link between FATP2-mediated lipid uptake and therapy resistance established\",\n      \"pmids\": [\"32499221\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Deletion of FATP2 in mouse liver shifts the transcriptomic landscape, upregulating PPARα-regulated genes involved in fatty acid degradation, peroxisome biogenesis, and fatty acid synthesis; targeted metabolomics shows increases in C16:0, C16:1, C18:1 fatty acids and lipid mediators (lipoxin A4, prostaglandin J2) and decreased 20-HETE, indicating FATP2 provides PPARα with specific proximal ligands and broadly governs hepatic lipid metabolism.\",\n      \"method\": \"FATP2-null (Fatp2-/-) mouse model, RNA-Seq transcriptomics, targeted metabolomics, RT-qPCR validation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KO mouse with RNA-Seq and metabolomics, single lab, multiple orthogonal readouts; PPARα link inferred from transcriptomics rather than direct binding assay\",\n      \"pmids\": [\"32188695\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Arachidonic acid activates the NLRP3 inflammasome in myeloid-derived suppressor cells (MDSCs) specifically through FATP2; FATP2-mediated arachidonic acid uptake causes mitochondrial dysfunction and enhanced ROS production, which bridges lipid uptake to NLRP3 activation; activated MDSCs then stimulate CD4+ T cells to produce IL-17, promoting post-transplant tumor recurrence; blockade of FATP2 (Lipofermata) inhibits this entire axis.\",\n      \"method\": \"Lipid uptake receptor screening, mouse fatty liver ischemia-reperfusion injury model with tumor recurrence, FATP2 inhibitor (Lipofermata) treatment, NLRP3/ROS/IL-17 mechanistic assays in vitro and in vivo, clinical cohort validation\",\n      \"journal\": \"JHEP reports : innovation in hepatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic pathway established by screening, in vivo model, and in vitro mechanistic follow-up; single lab but multiple orthogonal methods\",\n      \"pmids\": [\"37916155\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"FATP2 physically interacts with ACSL1 (long-chain acyl-CoA synthetase 1) in NSCLC cells, as demonstrated by Co-IP; FATP2 knockdown combined with ACSL1 overexpression further inhibits cell proliferation, lipid deposition, and promotes fatty acid decomposition compared to either alone, indicating FATP2 regulates lipid metabolism and cancer cell proliferation through functional interaction with ACSL1.\",\n      \"method\": \"Co-immunoprecipitation (Co-IP), siRNA knockdown, pcDNA-ACSL1 overexpression, cell proliferation assay, lipid deposition assay, ER stress markers\",\n      \"journal\": \"Tissue & cell\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single Co-IP in one lab; mechanistic follow-up limited to cell-based assays without structural or biochemical reconstitution\",\n      \"pmids\": [\"37172427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NRF2 directly transcriptionally activates FATP2 in the context of valproic acid (VPA)-induced hepatic steatosis: VPA binds to Cys288 and Arg415 of KEAP1, promoting autophagic KEAP1 degradation, releasing NRF2 to translocate to the nucleus where it activates FATP2 transcription, thereby enhancing fatty acid uptake and driving steatosis; this was confirmed by chromatin immunoprecipitation and dual-luciferase reporter assays, and FATP2 knockout abrogated NRF2-driven steatosis.\",\n      \"method\": \"ChIP assay, dual-luciferase reporter assay, NRF2 overexpression/knockout mice (AAV and CRISPR/Cas9), FATP2 knockout mice (homologous recombination), site-directed mutagenesis of KEAP1 binding sites, in vivo VPA treatment\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — ChIP and luciferase reporter directly establish NRF2→FATP2 transcriptional axis; multiple genetic models (OE, KO) with in vivo validation; multiple orthogonal methods\",\n      \"pmids\": [\"40303331\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Loss of the epoxygenase Cyp2c44 (and reduced EET levels) leads to increased plasma membrane localization of FATP2 in hepatocytes, which is associated with increased total unsaturated fatty acids and diacylglycerol (DAG) accumulation, activation of PKCδ at the plasma membrane, IRS-1 serine phosphorylation, and impaired insulin signaling; treatment with the EET analog EET-A in Cyp2c44-/- HFD-fed mice decreased plasma membrane FATP2 and PKCδ levels with improved glucose tolerance, placing FATP2 membrane localization downstream of EET signaling and upstream of the DAG/PKCδ/IRS-1 axis.\",\n      \"method\": \"Cyp2c44-/- mouse model, subcellular fractionation, PKCδ inhibitor treatment, EET-A analog treatment, glucose tolerance test, lipidomics, immunoblotting\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic model with pharmacological rescue, subcellular fractionation, and lipidomics; single lab; pathway placement via epistasis-like approach\",\n      \"pmids\": [\"38743615\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FATP2 expression is upregulated during osteoclast (OC) differentiation and in bone marrow of HFD-fed mice; FATP2 siRNA or Lipofermata inhibition significantly suppresses OC differentiation with minimal effect on osteoblasts; RNA-seq shows Lipofermata reduces fatty acid β-oxidation, energy metabolism, and ROS production in OCs; in vivo Lipofermata treatment rescues bone loss in LPS-induced and ovariectomy models by inhibiting OC differentiation, establishing FATP2 as a regulator of osteoclastogenesis through fatty acid uptake and energy/ROS metabolism.\",\n      \"method\": \"siRNA knockdown, specific inhibitor (Lipofermata), RNA-seq, in vivo mouse models (LPS-induced and ovariectomy), bone mass measurement, ROS assays\",\n      \"journal\": \"Journal of bone and mineral research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vivo and in vitro models with RNA-seq mechanistic follow-up; single lab\",\n      \"pmids\": [\"38477781\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CEACAM6 promotes SLC27A2/FATP2 protein stability by interacting with both SLC27A2 and the deubiquitinase USP29; CEACAM6 facilitates USP29-mediated deubiquitination of SLC27A2, thereby upregulating fatty acid uptake and FAO in gastric cancer cells; pharmacological inhibition of SLC27A2 attenuates the tumor-initiating ability of CEACAM6-positive gastric cancer.\",\n      \"method\": \"Co-immunoprecipitation (protein-protein interaction), deubiquitination assay, SLC27A2 inhibitor (Lipofermata), in vitro and in vivo tumor models\",\n      \"journal\": \"Cancer gene therapy\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP demonstrates interaction; deubiquitination assay supports mechanism but single lab, limited replication\",\n      \"pmids\": [\"39562695\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In pancreatic islets, FATP2 expression is restricted to α-cells; FATP2 knockout or pharmacological inhibition (Lipofermata) in db/db mice and isolated human islets increases GLP-1-positive α-cell mass and stimulates GLP-1 secretion from α-cells; this α-cell-derived GLP-1 promotes paracrine insulin secretion from β-cells, reducing plasma glucose; the glucose-lowering effect is abrogated by GLP-1 receptor antagonism (exendin[9-39]), confirming that FATP2 inhibition acts through α-cell GLP-1 secretion rather than enteroendocrine pathways.\",\n      \"method\": \"FATP2 global KO mouse (db/db background), small molecule inhibitor (Lipofermata), GLP-1 receptor antagonist (exendin[9-39]), immunolocalization, αTC1-6 cell and human islet assays, oral vs. IP glucose challenge, mRNA co-expression analysis\",\n      \"journal\": \"bioRxiv : the preprint server for biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (KO, pharmacological, cell, human islet); preprint, not yet peer-reviewed; strong mechanistic specificity via receptor antagonism rescue\",\n      \"pmids\": [\"39975070\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"FATP2 homology model (validated by AlphaFold2 prediction and site-directed mutagenesis) was used to identify key residues for inhibitor binding; virtual screening identified two nanomolar IC50 inhibitors of FATP2-dependent fatty acid uptake and apoptosis in proximal tubule cells, providing structural insights into the FATP2 binding site.\",\n      \"method\": \"Homology modeling, AlphaFold2 structural prediction, site-directed mutagenesis, virtual docking, in vitro fatty acid uptake assay, apoptosis assay, molecular dynamics simulations\",\n      \"journal\": \"International journal of biological macromolecules\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — homology model rather than experimental structure; mutagenesis validates model but limited mechanistic depth; single lab\",\n      \"pmids\": [\"37307967\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FATP2 inhibition (Lipofermata) in human monocytes reduces LPS-induced inflammatory responses and decreases biosynthesis of arachidonic acid-derived lipid mediators (PGE2, TxB2), indicating FATP2-dependent arachidonic acid uptake supports eicosanoid production; conversely, in mature monocyte-derived macrophages, Lipofermata enhances LPS-induced cytokine production and induces cell death likely through inflammasome activation, demonstrating cell type-specific roles of FATP2 in inflammatory lipid metabolism.\",\n      \"method\": \"Lipofermata inhibitor treatment, LPS stimulation, cytokine measurement, lipidomics (lipid mediator profiling), cell death assays in human monocytes and macrophages\",\n      \"journal\": \"Immunology letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — pharmacological inhibitor only (no genetic knockdown), single lab, mechanistic interpretation relies on inhibitor selectivity\",\n      \"pmids\": [\"41015393\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"SLC27A2/FATP2 is a multifunctional, localization-dependent protein that functions as a long-chain fatty acid transporter (primarily at the plasma membrane) and as a peroxisomal very long-chain acyl-CoA synthetase; its transport activity drives vectorial acylation in partnership with ACSLs, it is transcriptionally regulated by NRF2, its plasma membrane localization is controlled by EET/Cyp2c44 signaling upstream of a DAG/PKCδ/IRS-1 insulin-resistance axis, it mediates lipoapoptosis in renal proximal tubules via apical NEFA uptake, it supports NLRP3 inflammasome activation in MDSCs via arachidonic acid uptake, and in pancreatic α-cells its inhibition promotes GLP-1 secretion and paracrine insulin release.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"SLC27A2/FATP2 is a localization-dependent, bifunctional protein that couples cellular long-chain fatty acid (LCFA) uptake to fatty acid activation, governing tissue lipid metabolism and lipid-driven pathology [#0, #2]. Its two enzymatic activities are mechanistically separable: a transport function that drives LCFA uptake and an intrinsic very long-chain acyl-CoA synthetase activity that directly generates C20:4-CoA and C22:6-CoA, while partnering with long-chain acyl-CoA synthetases (ACSLs) to esterify shorter chains through vectorial acylation [#0, #2, #9]. This dissociability is established by a naturally occurring splice variant (FATP2b) that retains transport but lacks synthetase activity and by small molecules (Lipofermata, Grassofermata) that block transport without affecting synthetase activity [#3, #4]. FATP2 abundance and membrane positioning are tightly regulated: NRF2 directly transactivates FATP2 to enhance fatty acid uptake and drive hepatic steatosis [#10], and loss of the epoxygenase Cyp2c44 increases plasma membrane FATP2, promoting DAG accumulation, PKCδ activation, IRS-1 serine phosphorylation, and insulin resistance [#11]. Through apical NEFA uptake in kidney proximal tubule epithelium, FATP2 mediates palmitate-induced lipoapoptosis and proteinuria-induced tubular injury [#5]. FATP2-dependent fatty acid uptake also fuels disease-relevant programs in other tissues: it supports melanoma resistance to BRAF/MEK inhibition via mitochondrial metabolism [#6], drives arachidonic-acid-triggered NLRP3 inflammasome activation in myeloid-derived suppressor cells [#8], and promotes osteoclastogenesis through β-oxidation and ROS [#12]. In pancreatic α-cells FATP2 inhibition increases GLP-1 secretion that paracrine-stimulates β-cell insulin release [#14].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Established that FATP2-mediated fatty acid transport could be pharmacologically separated from acyl-CoA synthetase activity, proving the two are distinct druggable functions.\",\n      \"evidence\": \"High-throughput screen in yeast expressing human FATP2 with follow-up uptake and synthetase assays in human cell lines\",\n      \"pmids\": [\"19913517\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not define the structural basis of transport vs. synthetase activity\", \"Selectivity of inhibitors across other FATP family members not resolved\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Resolved the long-standing ambiguity over FATP2's primary in vivo role by showing it acts mainly as a plasma membrane LCFA transporter rather than a peroxisomal VLACS enzyme in liver.\",\n      \"evidence\": \"Liver-specific AAV8 shRNA knockdown with subcellular fractionation, VLACS activity, and radiolabeled uptake assays in mice\",\n      \"pmids\": [\"20530735\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not establish how transport is mechanistically coupled to esterification\", \"Peroxisomal contribution in other tissues unaddressed\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Showed FATP2 can localize to the ER in human hepatoma cells and drives uptake indirectly through esterification, framing the vectorial acylation model.\",\n      \"evidence\": \"Immunofluorescence co-localization, overexpression, ACS activity and oleic acid/BODIPY-C12 uptake assays in HuH7/HepG2\",\n      \"pmids\": [\"22022213\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Localization conflicts with plasma-membrane role seen in liver—context dependence not reconciled\", \"No independent replication reported\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Defined the dual biochemical logic: FATP2 partners with ACSLs for LCFA-CoA generation while intrinsically activating very long-chain species, and reshapes fatty acid trafficking into specific phospholipid classes.\",\n      \"evidence\": \"Stable-isotope fatty acid tracing with MS-based lipidomics in overexpressing cells\",\n      \"pmids\": [\"24113382\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct physical ACSL partnership not demonstrated in this study\", \"Species-selective trafficking mechanism unknown\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Used an endogenous separation-of-function splice variant (FATP2b) to confirm transport and synthetase activities are genetically separable and validated transport-selective inhibitors in vivo.\",\n      \"evidence\": \"Splice variant characterization with enzymatic/uptake assays and in vitro/in vivo inhibitor studies in mice\",\n      \"pmids\": [\"27446528\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological regulation of FATP2b splicing not defined\", \"Structural determinant of the lost synthetase activity unmapped\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Identified FATP2 as the apical proximal tubule NEFA transporter whose uptake drives lipoapoptosis, linking it causally to tubular injury.\",\n      \"evidence\": \"Slc27a2 knockout mice, ex vivo microperfusion, shRNA knockdown, and proteinuria model with apoptosis readouts\",\n      \"pmids\": [\"28993506\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream apoptotic signaling from NEFA accumulation not detailed\", \"Restriction of expression to proximal tubule mechanism unexplained\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Connected FATP2-mediated lipid uptake to PPARα ligand provision and broad hepatic metabolic control, and to tumor lipid programming.\",\n      \"evidence\": \"Fatp2-/- mouse RNA-Seq and targeted metabolomics; melanoma co-culture, uptake, mitochondrial and in vivo therapy-resistance models\",\n      \"pmids\": [\"32188695\", \"32499221\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"PPARα ligand link inferred from transcriptomics, not direct binding\", \"Direct FATP2 substrate driving therapy resistance not isolated\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placed FATP2 upstream of innate immune and proliferative lipid programs—arachidonic-acid-driven NLRP3 activation in MDSCs and ACSL1-coupled lipid metabolism in cancer cells.\",\n      \"evidence\": \"Lipid uptake screening, in vivo ischemia-reperfusion/tumor recurrence model with Lipofermata; Co-IP and knockdown/overexpression in NSCLC cells\",\n      \"pmids\": [\"37916155\", \"37172427\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ACSL1 interaction rests on a single Co-IP without reciprocal validation\", \"How arachidonic acid uptake mechanistically triggers mitochondrial ROS not fully resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Provided a structural model of the FATP2 inhibitor binding site, enabling nanomolar inhibitor discovery.\",\n      \"evidence\": \"AlphaFold2-based homology model with site-directed mutagenesis, virtual screening, and uptake/apoptosis assays\",\n      \"pmids\": [\"37307967\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Homology model, not an experimental structure\", \"Limited mechanistic depth beyond mutagenesis validation\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified the NRF2→FATP2 transcriptional axis as a driver of drug-induced hepatic steatosis, establishing direct transcriptional control of FATP2.\",\n      \"evidence\": \"ChIP and dual-luciferase reporter assays, NRF2 and FATP2 genetic mouse models, KEAP1 site-directed mutagenesis with VPA treatment\",\n      \"pmids\": [\"40303331\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Other transcriptional regulators of FATP2 not surveyed\", \"Tissue scope of NRF2 control beyond liver unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined post-translational and localization control of FATP2—USP29/CEACAM6-mediated stabilization and EET/Cyp2c44 control of plasma membrane localization feeding the DAG/PKCδ/IRS-1 insulin-resistance axis.\",\n      \"evidence\": \"Co-IP and deubiquitination assays with tumor models; Cyp2c44-/- mice with fractionation, lipidomics, PKCδ inhibition and EET-A rescue\",\n      \"pmids\": [\"39562695\", \"38743615\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"CEACAM6/USP29 mechanism rests on Co-IP without reciprocal/structural validation\", \"How EET signaling physically alters FATP2 trafficking is unknown\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Extended FATP2's metabolic reach to osteoclastogenesis, where its fatty acid uptake fuels β-oxidation and ROS required for bone resorption.\",\n      \"evidence\": \"siRNA and Lipofermata inhibition, RNA-seq, and LPS-induced and ovariectomy bone-loss mouse models\",\n      \"pmids\": [\"38477781\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct lipid substrate driving osteoclast energy metabolism not identified\", \"Specificity for osteoclasts over osteoblasts mechanism unexplained\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed an α-cell-specific FATP2 role whose inhibition increases GLP-1 secretion and paracrine β-cell insulin release, defining a glucose-lowering axis.\",\n      \"evidence\": \"FATP2 KO (db/db), Lipofermata, GLP-1 receptor antagonist rescue, αTC1-6 and human islet assays (preprint)\",\n      \"pmids\": [\"39975070\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, not yet peer-reviewed\", \"How loss of α-cell FATP2 lipid uptake triggers GLP-1 secretion mechanistically unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How FATP2 transport activity is mechanically coupled to acyl-CoA synthesis at the molecular level, and what determines its differential localization (plasma membrane vs. ER vs. peroxisome) across cell types, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No experimental high-resolution structure of FATP2\", \"Determinants of cell-type-specific localization not defined\", \"Direct biochemical reconstitution of FATP2-ACSL vectorial acylation lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": [0, 1, 3, 4, 5]},\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [0, 2, 4]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [1, 2, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 5, 11]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0005777\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 2, 7]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 5]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [8, 16]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"ACSL1\", \"CEACAM6\", \"USP29\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":7,"faith_pct":85.71428571428571}}