{"gene":"NAMPT","run_date":"2026-04-29T11:37:56","timeline":{"discoveries":[{"year":1994,"finding":"NAMPT (then called PBEF) was originally cloned from a human peripheral blood lymphocyte cDNA library as a secreted 52-kDa protein that synergizes with stem cell factor and IL-7 to enhance pre-B-cell colony formation, establishing it as a cytokine acting on early B-lineage precursor cells.","method":"cDNA library screening, expression in COS7/PA317 cells, in vitro B-cell colony formation assay","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 1 — original cloning and functional characterization with direct biological assay","pmids":["8289818"],"is_preprint":false},{"year":2002,"finding":"PBEF/NAMPT was identified as a nicotinamide phosphoribosyltransferase (NAmPRTase), catalyzing the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide (NMN), an intermediate in NAD biosynthesis; the mouse gene complemented a NAmPRTase-defective bacterial strain, confirming enzymatic function.","method":"Enzymatic activity assay, bacterial complementation assay, antibody panel characterization","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 1 — direct enzymatic assay plus genetic complementation, foundational identification","pmids":["12555668"],"is_preprint":false},{"year":2006,"finding":"Crystal structure of NAMPT (with and without NMN bound) revealed it is a dimeric type II phosphoribosyltransferase, providing structural insights into the enzymatic mechanism of NMN synthesis.","method":"X-ray crystallography","journal":"Nature structural & molecular biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with and without product, high-resolution mechanistic insight","pmids":["16783373"],"is_preprint":false},{"year":2007,"finding":"Haplodeficiency and chemical inhibition of NAMPT cause defects in NAD biosynthesis and glucose-stimulated insulin secretion in pancreatic islets; extracellular NAMPT (eNAMPT) exerts its effects through NAD biosynthetic activity (producing NMN) rather than insulin-mimetic hormone activity, as administration of NMN rescues the defects.","method":"Nampt heterozygous knockout mice, chemical inhibition, NMN rescue experiments, in vitro and in vivo glucose-stimulated insulin secretion assays","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal genetic and pharmacological methods with defined phenotypic rescue, highly cited foundational study","pmids":["17983582"],"is_preprint":false},{"year":2007,"finding":"NAMPT is the rate-limiting enzyme in the NAD+ salvage pathway from nicotinamide in mammals; increased NAMPT expression under fasting conditions elevates mitochondrial NAD+ levels and provides protection against cell death, requiring mitochondrial NAD+-dependent deacetylases SIRT3 and SIRT4.","method":"Fasting experiments in rodents, subcellular fractionation, siRNA knockdown, cell viability assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods including genetic knockdown and fractionation, highly cited","pmids":["17889652"],"is_preprint":false},{"year":2004,"finding":"PBEF/NAMPT functions as a novel inhibitor of neutrophil apoptosis in response to inflammatory stimuli (LPS, IL-1, GM-CSF, IL-8, TNF-α); antisense oligonucleotide blockade of PBEF translation completely abrogates LPS-induced neutrophil apoptosis delay, and inhibition is associated with reduced caspase-8 and caspase-3 activity.","method":"Antisense oligonucleotide, recombinant protein treatment, caspase activity assays, apoptosis quantification","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 — loss-of-function with antisense and gain-of-function with recombinant protein, well-defined mechanism, highly cited","pmids":["15124023"],"is_preprint":false},{"year":2007,"finding":"Extracellular visfatin (NAMPT) activates human leukocytes and induces cytokine production (IL-1β, TNF-α, IL-6) in CD14+ monocytes, increases costimulatory molecule expression (CD54, CD40, CD80), and activates NF-κB via p38 and MEK1 MAPK pathways.","method":"Recombinant protein treatment, MAPK inhibitor experiments, NF-κB activation assays, cytokine ELISA, flow cytometry","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — multiple signaling pathway inhibitors used, replicated across multiple readouts, highly cited","pmids":["17237424"],"is_preprint":false},{"year":2007,"finding":"NAMPT-mediated NAD+ biosynthesis extends the lifespan of human vascular smooth muscle cells through increased SIRT1 activity and reduced p53 acetylation (K382) and degradation; a dominant-negative SIRT1 abrogates the anti-aging effect, placing NAMPT upstream of SIRT1 in this pathway.","method":"Nampt gene overexpression, FK866 inhibitor, dominant-negative SIRT1 transduction, senescence-associated β-galactosidase assay, p53 acetylation western blot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with dominant-negative, multiple orthogonal methods, clearly defined pathway order","pmids":["17307730"],"is_preprint":false},{"year":2009,"finding":"Extracellular NAMPT activates pro-inflammatory signaling in human vascular smooth muscle cells through its intrinsic enzymatic activity: it induces iNOS via sequential ERK1/2 and NF-κB activation; exogenous NMN (the product of NAMPT) mimics these effects, while the NAMPT inhibitor APO866 blocks them, demonstrating the enzymatic activity is required.","method":"Western blotting, EMSA (NF-κB), ERK inhibitor PD98059, NF-κB inhibitor, APO866, exogenous NMN treatment","journal":"Diabetologia","confidence":"High","confidence_rationale":"Tier 2 — NMN mimicry and inhibitor block establish enzymatic activity as mechanism, multiple signaling readouts","pmids":["19727662"],"is_preprint":false},{"year":2009,"finding":"Human hepatocytes constitutively release NAMPT into the extracellular compartment; secreted NAMPT exists primarily as the dimeric form and retains enzymatic activity; hepatocyte NAMPT secretion is not regulated by glucose, insulin, or TNF-α.","method":"Size exclusion chromatography, in vitro enzymatic activity assay, HepG2 cells and primary human hepatocytes","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — enzymatic activity confirmed in secreted fraction, multiple cell types tested, single lab","pmids":["19912992"],"is_preprint":false},{"year":2011,"finding":"Extracellular PBEF/NAMPT primes neutrophils for augmented NADPH oxidase-dependent respiratory burst by promoting membrane translocation of cytosolic NADPH oxidase subunits p40 and p47 (but not p67), inducing p40 phosphorylation on Thr154, and activating Rac GTPase; this priming is dependent on p38 and ERK MAPK but is independent of NAMPT's NAD-generating capacity (NMN or NAD cannot recapitulate the effect, and APO866 does not block it).","method":"Membrane fractionation, phosphorylation assays, Rac GTPase activation assay, MAPK inhibitors, APO866 inhibitor, ROS measurement","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods establishing enzyme-independent mechanism, clearly dissected from enzymatic activity","pmids":["21518975"],"is_preprint":false},{"year":2013,"finding":"NAMPT enzymatic activity regulates GADD45A expression through the NAMPT→NAD+→SIRT1→FOXO3a acetylation axis: NAMPT overexpression decreases GADD45A expression, while NAMPT inhibition by FK866 or SIRT1 knockdown increases GADD45A; the increase involves acetylation of FOXO3a.","method":"NAMPT overexpression, FK866 inhibitor, SIRT1 shRNA, western blotting, gene expression analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — genetic and pharmacological perturbations with pathway readouts, single lab","pmids":["22430142"],"is_preprint":false},{"year":2014,"finding":"Extracellular NAMPT (eNAMPT) promotes M2 macrophage polarization in chronic lymphocytic leukemia independently of its enzymatic activity, as demonstrated by use of an enzymatically inactive mutant; eNAMPT is produced by CLL lymphocytes upon BCR, TLR, and NF-κB signaling activation and polarized macrophages activate ERK1/2, STAT3, and NF-κB signaling.","method":"Enzymatically inactive NAMPT mutant, monocyte differentiation assays, flow cytometry, cytokine profiling, signaling pathway western blots","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 — enzymatic mutant used to dissect enzyme-independent function, multiple signaling readouts, key mechanistic distinction","pmids":["25368373"],"is_preprint":false},{"year":2014,"finding":"Forebrain excitatory neurons primarily use intracellular NAMPT-mediated NAD+ biosynthesis for their survival and function; CaMKIIα-specific Nampt knockout mice develop hippocampal/cortical atrophy, astrogliosis, microgliosis, abnormal CA1 dendritic morphology, altered intrahippocampal connectivity, and behavioral impairments including memory deficits.","method":"Conditional (CaMKIIα-Cre) Nampt knockout mice, histology, electrophysiology, behavioral testing","journal":"The Journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — cell-type specific genetic knockout with defined structural and functional phenotypes, multiple orthogonal readouts","pmids":["24760840"],"is_preprint":false},{"year":2018,"finding":"SIRT6 directly deacetylates NAMPT (identified by immunopurification and incubation with recombinant SIRT6), and this deacetylation upregulates NAMPT enzymatic activity, increasing intracellular NAD(H) levels and protecting cancer cells against oxidative stress.","method":"Immunopurification, recombinant SIRT6 incubation, SIRT6 overexpression/silencing in cancer cells, NAD(H) measurement, enzymatic activity assay","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro reconstitution of SIRT6-NAMPT deacetylation, functional validation in cells","pmids":["30514106"],"is_preprint":false},{"year":2019,"finding":"Extracellular NAMPT (eNAMPT) is carried in extracellular vesicles (EVs) through systemic circulation in mice and humans; EV-contained eNAMPT is internalized into cells and enhances NAD+ biosynthesis; supplementing eNAMPT-containing EVs from young mice improves physical activity and extends lifespan in aged mice.","method":"EV isolation, internalization assays, NAD+ measurement, adipose-tissue-specific NAMPT overexpression, lifespan and wheel-running experiments in mice","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 — mechanistic EV delivery established with multiple methods, functional consequence demonstrated in vivo","pmids":["31204283"],"is_preprint":false},{"year":2019,"finding":"Both loss and gain of Nampt function exacerbate pressure-overload-induced heart failure; Nampt knockdown diminishes mitochondrial NAD content and ATP production in cardiomyocytes; Nampt overexpression increases Sirt1 expression and activity, causing excessive suppression of mitochondrial proteins and metabolic genes plus upregulation of inflammatory cytokines.","method":"Nampt+/- heterozygous KO mice, cardiac-specific Nampt transgenic mice, pressure overload model, mitochondrial NAD/ATP measurement, protein acetylation analysis","journal":"American journal of physiology. Heart and circulatory physiology","confidence":"High","confidence_rationale":"Tier 2 — complementary gain- and loss-of-function models with mechanistic readouts, multiple orthogonal measurements","pmids":["31347918"],"is_preprint":false},{"year":2019,"finding":"NAMPT is localized within the mitochondrial matrix of neurons (alongside NMNAT3), where it maintains an intact NAD+ salvage pathway; NMNAT3 knockdown has a larger effect on mitochondrial respiration than NMNAT1/2, while NMNAT1/2 affect glycolytic flux more; mitochondrial, cytoplasmic, and non-compartmental NAMPT overexpression all provide comparable neuronal protection and suppression of apoptosis-inducing factor translocation after ischemia.","method":"Subcellular fractionation, siRNA knockdown of NMNAT1-3 and NAMPT, confocal microscopy, oxygen glucose deprivation model, mitochondrial respiration assay","journal":"Journal of neurochemistry","confidence":"High","confidence_rationale":"Tier 2 — direct subcellular fractionation and localization combined with functional knockdown experiments","pmids":["31553812"],"is_preprint":false},{"year":2021,"finding":"Macrophage-derived eNAMPT (secreted from a specific 'dwelling' macrophage subset) is required for muscle stem cell (satellite cell) proliferation and muscle regeneration in zebrafish; eNAMPT acts through the C-C motif chemokine receptor CCR5 expressed on muscle stem cells.","method":"Zebrafish muscle injury models, single-cell profiling, real-time in vivo imaging, genetic perturbation of NAMPT/CCR5","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 — receptor identified (CCR5), in vivo genetic requirement established, high-profile journal","pmids":["33568815"],"is_preprint":false},{"year":2021,"finding":"Circadian clock components REV-ERBα/β repress E4BP4, which directly controls the circadian expression of Nampt via distal cis-regulatory elements; loss of Rev-erbs induces E4BP4 and downregulates Nampt, reducing NAD+ production via the salvage pathway and causing dilated cardiomyopathy.","method":"Cardiomyocyte-specific Rev-erb double knockout mice, chromatin occupancy (ChIP), NAD+ measurement, gene expression analysis","journal":"Nature cardiovascular research","confidence":"High","confidence_rationale":"Tier 2 — genetic epistasis with tissue-specific KO and chromatin-level mechanistic dissection","pmids":["35036997"],"is_preprint":false},{"year":2021,"finding":"NAMPT-derived NAD+ fuels PARP1 hyperactivation in response to ROS-induced DNA damage, promoting parthanatos cell death and skin inflammation; genetic and pharmacological inhibition of NAMPT reduces oxidative stress, PARP1 activity, AIFM1 nuclear translocation, and keratinocyte hyperproliferation in zebrafish models and human 3D skin models of psoriasis.","method":"Zebrafish genetic/pharmacological inhibition models, human organotypic 3D skin models, PARP activity measurement, AIFM1 localization, gene expression analysis","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 — multiple model systems, genetic and pharmacological approaches, defined pathway: NAMPT→NAD+→PARP1→parthanatos","pmids":["34748530"],"is_preprint":false},{"year":2021,"finding":"STAT1 occupies a conserved intronic element (NRE1) within the Nampt gene in response to IFN-γ, driving NAMPT expression in macrophages; disruption of NRE1 reduces a subset of M1 inflammatory gene expression dependent on NAMPT-supported glycolysis, and myeloid-specific NRE1 ablation increases tumor burden in melanoma models.","method":"ChIP of STAT1 at NRE1, NRE1 knockout mouse strain, scRNAseq of tumor-associated leukocytes, pharmacological NAMPT inhibition, glycolysis assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — in vivo genetic evidence with STAT1 ChIP and novel mouse strain, defined transcriptional mechanism","pmids":["33976173"],"is_preprint":false},{"year":2022,"finding":"miR-146a directly targets the 3'-UTR of Nampt mRNA to reduce NAMPT expression, thereby impairing AMPK-driven NAD+ synthesis and SIRT activity; AMPK activators (metformin, AICAR) suppress miR-146a transcription by promoting IKK phosphorylation and attenuating NF-κB activity, establishing a mutual inhibitory relationship between miR-146a and AMPK that regulates the NAD+/SIRT pathway.","method":"miR-146a overexpression/inhibition, 3'-UTR luciferase assay, NAMPT expression analysis, SIRT activity measurement, NF-κB/IKK assays, in vitro and in vivo experiments","journal":"Signal transduction and targeted therapy","confidence":"High","confidence_rationale":"Tier 2 — direct 3'-UTR targeting validated, pathway epistasis established in vitro and in vivo","pmids":["35241643"],"is_preprint":false},{"year":2022,"finding":"Lamin A/C deficiency causes reduced chromatin accessibility at the Nampt gene promoter (by ATAC-seq), leading to decreased NAMPT expression and reduced SIRT1 activity, which together impair NAD+ levels and mitochondrial function; high PARylation in lamin-aberrant cells further depletes the NAD+ pool.","method":"Lmna-/- MEFs, HGPS fibroblasts, ATAC-seq, NAD+ measurement, SIRT1 activity, mitochondrial DNA stability, bioenergetics assays","journal":"Nucleic acids research","confidence":"High","confidence_rationale":"Tier 2 — ATAC-seq identifies chromatin mechanism, multiple cell models, orthogonal functional readouts","pmids":["36099415"],"is_preprint":false},{"year":2022,"finding":"NAMPT depletion specifically in hippocampal CA1 neurons (via rAAV-Cre) causes cognitive deficiency, mitochondrial swelling and decreased mitochondrial number in neuronal cell bodies and neurites, increased intracellular Aβ aggregation, and gliosis; FK866 inhibition decreases neuronal NAD+, drops mitochondrial membrane potential, and reduces neuronal branching in a dose-dependent manner.","method":"rAAV-hSyn-Cre hippocampal CA1-specific Nampt KO, transmission electron microscopy, immunofluorescence, FK866 dose-response in primary neurons, mitochondrial membrane potential assay","journal":"Molecular neurobiology","confidence":"High","confidence_rationale":"Tier 2 — region-specific in vivo KO combined with in vitro mechanistic assays, structural and functional phenotypes","pmids":["36441480"],"is_preprint":false},{"year":2023,"finding":"NAMPT activity is restored in aging by SIRT1 binding and subsequent deacetylation of NAMPT; low-dose nicotine activates this mechanism independently of nicotinic acetylcholine receptors, increasing NAD+ synthesis and ameliorating age-related metabolic and cognitive decline in mice.","method":"SIRT1-NAMPT co-immunoprecipitation, NAMPT deacetylation assay, 18F-FDG PET imaging, in vivo nicotine treatment of aging mice, cognitive and metabolic assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — Co-IP identifies SIRT1 as NAMPT deacetylase, functional in vivo validation with multiple readouts","pmids":["36797299"],"is_preprint":false},{"year":2023,"finding":"NAMPT-dependent NAD+ biosynthesis controls the molecular circadian clock in a tissue-specific manner: brown adipose tissue (BAT) requires NAMPT to sustain core clock amplitude and TCA cycle intermediate oscillations, white adipose tissue is moderately dependent, and skeletal muscle clock is completely refractory to NAMPT loss.","method":"Adipose-specific Nampt knockout mice, core clock gene expression, metabolomics, cold stress experiments","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — tissue-specific KO with comprehensive molecular and metabolic profiling, mechanistic tissue specificity established","pmids":["36996103"],"is_preprint":false},{"year":2024,"finding":"NAMPT deficiency in macrophages causes HIF-1α destabilization, leading to reduced M2-like tumor-associated macrophage (TAM) polarization and decreased efferocytosis; NAMPT deficiency also enhances STING signaling and type I IFN-response gene expression, potentiating cytotoxic T cell anti-tumor activity in colorectal cancer.","method":"Myeloid-specific Nampt knockout mice, scRNA-seq of tumor microenvironment, HIF-1α stability assay, efferocytosis assay, STING pathway analysis, T cell activity assays","journal":"Advanced science","confidence":"High","confidence_rationale":"Tier 2 — in vivo myeloid-specific KO with mechanistic dissection via scRNA-seq and defined pathway (NAMPT→HIF-1α→M2 polarization/efferocytosis→STING)","pmids":["38308188"],"is_preprint":false},{"year":2008,"finding":"NAMPT/PBEF interacts with NADH dehydrogenase subunit 1 (ND1), ferritin light chain, and IFITM3 in human pulmonary vascular endothelial cells; PBEF overexpression increases these interactions and increases intracellular oxidative stress, attenuated by rotenone.","method":"Co-immunoprecipitation, overexpression, oxidative stress measurement, rotenone inhibition, interaction modeling","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 3 — single Co-IP identification of interaction partners, limited functional follow-up","pmids":["18486613"],"is_preprint":false},{"year":2015,"finding":"In hen granulosa cells, recombinant NAMPT (100 ng/ml) inhibits basal and IGF1-induced progesterone secretion by reducing STAR and HSD3B protein levels and MAPK3/1 phosphorylation; these effects are abolished by the NAMPT enzymatic inhibitor FK866, establishing that enzymatic activity is required for the reproductive effect.","method":"Recombinant NAMPT treatment, FK866 inhibition, western blotting for STAR/HSD3B, MAPK phosphorylation assay, progesterone RIA","journal":"Reproduction (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 — FK866 rescue establishes enzymatic activity requirement, avian model ortholog with consistent mechanism","pmids":["25918435"],"is_preprint":false},{"year":2019,"finding":"NAMPT overexpression promotes cell survival under oxidative stress via both a SIRT1-dependent p53-CD38 pathway and a SIRT1-independent NRF2-PPARα/AMPKα pathway; NAMPT-activated NRF2 rescues mitochondrial membrane potential and content under H2O2 treatment, identifying NRF2 as a downstream target of NAMPT.","method":"NAMPT overexpression, H2O2 oxidative stress, SIRT1 inhibition, mitochondrial membrane potential assay, western blotting for NRF2/PPARα/AMPKα","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 — pathway dissected with pharmacological inhibitors and overexpression, single lab","pmids":["31816398"],"is_preprint":false},{"year":2012,"finding":"NAMPT activity regulates FOXO3a acetylation status and thereby controls GADD45A expression: increased intracellular NAD+ (via NAMPT) activates SIRT1 to deacetylate FOXO3a, reducing GADD45A transcription, while NAMPT inhibition leads to FOXO3a acetylation and GADD45A upregulation.","method":"NAMPT overexpression, FK866, SIRT1 shRNA, FOXO3a acetylation western blot, GADD45A expression analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — genetic and pharmacological tools used to establish pathway, single lab","pmids":["22430142"],"is_preprint":false},{"year":2024,"finding":"NAMPT deacetylation by SIRT2 activates LDHA, promoting lactate production through glycolysis in ovarian granulosa cells; FK866-mediated NAD+ synthesis inhibition increases LDHA acetylation (confirmed by Co-IP in 293T cells), reducing lactate and impairing follicular development in PCOS.","method":"Co-immunoprecipitation for LDHA acetylation, FK866 inhibition, NMN supplementation in PCOS rat model, transcriptomics, target energy metabolomics","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 — Co-IP validation of acetylation mechanism, in vivo PCOS model, pathway: NAMPT→NAD+→SIRT2→LDHA deacetylation→lactate","pmids":["39489197"],"is_preprint":false}],"current_model":"NAMPT is a dimeric type II phosphoribosyltransferase that catalyzes the rate-limiting step in the NAD+ salvage pathway (nicotinamide + PRPP → NMN), thereby controlling intracellular NAD+ concentrations and regulating downstream NAD+-consuming enzymes (SIRT1, SIRT2, SIRT3, SIRT4, PARP1, CD38); intracellularly it is deacetylated and activated by SIRT6, and its expression is transcriptionally controlled by STAT1 (via the NRE1 intronic element), REV-ERB/E4BP4 (circadian regulation), and miR-146a (post-transcriptional suppression); in neurons and cardiomyocytes NAMPT is present in the mitochondrial matrix where it maintains a local NAD+ pool critical for bioenergetics; the secreted extracellular form (eNAMPT), carried in extracellular vesicles, exerts both enzymatic (NAD biosynthesis-dependent) effects on β-cell insulin secretion, vascular inflammation, and systemic aging, and enzyme-independent cytokine-like effects including macrophage polarization (via MAPK/NF-κB/STAT3) and neutrophil NADPH oxidase priming (via p40/p47 translocation and Rac activation through p38/ERK), with the latter acting through CCR5 on muscle stem cells to drive tissue regeneration."},"narrative":{"teleology":[{"year":1994,"claim":"The gene was first identified as a secreted cytokine (PBEF) that synergizes with SCF and IL-7 to promote pre-B-cell colony formation, establishing its extracellular signaling role before its enzymatic function was known.","evidence":"cDNA library cloning from human peripheral blood lymphocytes with in vitro B-cell colony assay","pmids":["8289818"],"confidence":"High","gaps":["Receptor for the cytokine activity was not identified","Mechanism of synergy with SCF/IL-7 undefined"]},{"year":2002,"claim":"Reconstitution of NAMPT enzymatic activity—conversion of nicotinamide + PRPP to NMN—reframed PBEF as the rate-limiting NAD+ salvage enzyme, fundamentally changing the understanding of its biology from pure cytokine to metabolic enzyme.","evidence":"Direct enzymatic activity assay and bacterial complementation of NAmPRTase-defective strain","pmids":["12555668"],"confidence":"High","gaps":["How cytokine activity relates to enzymatic activity was unresolved","Structural basis of catalysis unknown at this point"]},{"year":2004,"claim":"Discovery that NAMPT inhibits neutrophil apoptosis in response to inflammatory stimuli demonstrated a pro-survival role in innate immune cells distinct from its B-cell effects.","evidence":"Antisense oligonucleotide knockdown and recombinant protein treatment with caspase activity assays in human neutrophils","pmids":["15124023"],"confidence":"High","gaps":["Whether this anti-apoptotic effect is enzymatic or cytokine-mediated was not resolved","Receptor and signaling pathway not identified"]},{"year":2006,"claim":"The crystal structure revealed NAMPT as a dimeric type II phosphoribosyltransferase, providing the structural framework for understanding catalysis and enabling rational inhibitor design.","evidence":"X-ray crystallography with and without NMN product bound","pmids":["16783373"],"confidence":"High","gaps":["Structural basis of the cytokine-like (enzyme-independent) activity remained unexplained"]},{"year":2007,"claim":"A series of studies established the NAMPT→NAD+→sirtuin axis as a central signaling conduit: NAMPT controls mitochondrial NAD+ and cell survival via SIRT3/SIRT4 under fasting, extends vascular smooth muscle cell lifespan via SIRT1-mediated p53 deacetylation, and eNAMPT regulates pancreatic β-cell insulin secretion through its enzymatic product NMN.","evidence":"Nampt+/− mice with NMN rescue for insulin secretion; fasting/fractionation/siRNA for mitochondrial sirtuins; dominant-negative SIRT1 epistasis for vascular senescence","pmids":["17983582","17889652","17307730"],"confidence":"High","gaps":["Whether eNAMPT has a dedicated receptor was unresolved","Tissue-specific differences in NAMPT dependence not yet mapped"]},{"year":2007,"claim":"Extracellular NAMPT was shown to activate monocytes and induce pro-inflammatory cytokines through p38/MEK1/NF-κB, establishing it as a dual-function molecule with both enzymatic and cytokine-like activities.","evidence":"Recombinant eNAMPT treatment of CD14+ monocytes with MAPK inhibitors and NF-κB activation assays","pmids":["17237424"],"confidence":"High","gaps":["Whether this monocyte activation requires enzymatic activity was not dissected here"]},{"year":2009,"claim":"Vascular inflammation by eNAMPT was shown to require its enzymatic activity (NMN mimics the effect, APO866 blocks it), while separately, constitutive hepatocyte secretion of dimeric eNAMPT was documented, indicating continuous systemic release.","evidence":"ERK/NF-κB signaling in vascular smooth muscle cells with NMN/APO866; size exclusion chromatography and activity assay on secreted hepatocyte NAMPT","pmids":["19727662","19912992"],"confidence":"High","gaps":["Mode of secretion (classical vs. non-classical) not determined","Relative contribution of different tissues to circulating eNAMPT unknown"]},{"year":2011,"claim":"Neutrophil NADPH oxidase priming by eNAMPT was definitively shown to be enzyme-independent—NMN and NAD cannot mimic it and APO866 cannot block it—acting instead through p38/ERK to translocate p40/p47 subunits and activate Rac, establishing a clear bifunctional paradigm for extracellular NAMPT.","evidence":"Membrane fractionation, Rac activation assay, MAPK inhibitors, and APO866 in human neutrophils","pmids":["21518975"],"confidence":"High","gaps":["The receptor mediating enzyme-independent signaling in neutrophils was not identified","Structural determinants on NAMPT that mediate cytokine-like activity unknown"]},{"year":2014,"claim":"Two landmark studies addressed tissue-autonomous requirements: eNAMPT promoted M2 macrophage polarization via ERK1/2/STAT3/NF-κB independently of enzymatic activity (proven by enzymatic mutant), while neuron-specific NAMPT deletion caused hippocampal atrophy, gliosis, and memory deficits, demonstrating non-redundant intracellular NAD+ dependency in excitatory neurons.","evidence":"Enzymatically inactive NAMPT mutant in CLL-derived macrophage polarization assay; CaMKIIα-Cre Nampt conditional knockout with histology, electrophysiology, and behavioral testing","pmids":["25368373","24760840"],"confidence":"High","gaps":["Receptor for enzyme-independent macrophage polarization not identified","Whether neuronal NAMPT loss phenotype is reversible with NMN supplementation untested in this study"]},{"year":2018,"claim":"SIRT6 was identified as a direct deacetylase of NAMPT, establishing a positive feedback loop where sirtuin activity enhances NAD+ biosynthesis by activating NAMPT.","evidence":"In vitro reconstitution of SIRT6-mediated NAMPT deacetylation with immunopurified NAMPT and recombinant SIRT6, validated by NAD(H) measurements in cancer cells","pmids":["30514106"],"confidence":"High","gaps":["Specific acetylation sites on NAMPT targeted by SIRT6 not mapped","Whether this loop operates in non-cancer contexts was unclear"]},{"year":2019,"claim":"Multiple studies refined compartment-specific roles: NAMPT resides in the neuronal mitochondrial matrix maintaining a local NAD+ salvage pathway; eNAMPT circulates in extracellular vesicles and its supplementation from young to old mice extends lifespan; and balanced NAMPT dosage is critical in the heart where both gain and loss of function worsen heart failure.","evidence":"Subcellular fractionation and NMNAT knockdown in neurons; EV isolation with NAD+ assays and lifespan studies in mice; Nampt+/− and cardiac-specific transgenic mice under pressure overload","pmids":["31553812","31204283","31347918"],"confidence":"High","gaps":["Mechanism of NAMPT import into mitochondria unknown (lacks canonical MTS)","Cargo-sorting mechanism for eNAMPT into EVs uncharacterized","Therapeutic window for NAMPT modulation in cardiac disease undefined"]},{"year":2021,"claim":"Transcriptional and receptor-level regulation was resolved: STAT1 drives NAMPT expression via the intronic NRE1 element in macrophages supporting anti-tumor glycolysis; REV-ERBα/β–E4BP4 controls circadian NAMPT expression in cardiomyocytes; and macrophage-derived eNAMPT acts through CCR5 on muscle stem cells to drive regeneration.","evidence":"STAT1 ChIP at NRE1 with myeloid-specific NRE1 KO and melanoma model; cardiomyocyte-specific Rev-erb DKO with ChIP; zebrafish NAMPT/CCR5 genetic perturbation with live imaging","pmids":["33976173","35036997","33568815"],"confidence":"High","gaps":["Whether CCR5 is the receptor for enzyme-independent eNAMPT signaling in mammals not confirmed","How NRE1-dependent NAMPT expression differs between macrophage subtypes not fully explored","Whether E4BP4 directly binds Nampt regulatory elements or acts indirectly needs clarification"]},{"year":2021,"claim":"NAMPT-supplied NAD+ was linked to parthanatos: in psoriasis models, NAMPT fuels PARP1 hyperactivation and AIFM1 nuclear translocation, causing keratinocyte death and inflammation—demonstrating pathological consequences of excessive NAD+ availability.","evidence":"Zebrafish and human 3D skin models with genetic/pharmacological NAMPT inhibition, PARP activity measurement, AIFM1 localization","pmids":["34748530"],"confidence":"High","gaps":["Whether NAMPT inhibition is therapeutically viable in human psoriasis untested","Relative contribution of PARP1 vs. other NAD+ consumers in this context unclear"]},{"year":2022,"claim":"Post-transcriptional and epigenetic control of NAMPT was elucidated: miR-146a directly suppresses NAMPT via 3′-UTR targeting within a mutual inhibitory loop with AMPK/NF-κB; and lamin A/C deficiency reduces NAMPT promoter chromatin accessibility, depleting NAD+ and impairing mitochondrial function in progeria.","evidence":"3′-UTR luciferase assay with miR-146a and AMPK activators in vitro/in vivo; ATAC-seq of Lmna−/− MEFs and HGPS fibroblasts with NAD+/SIRT1/bioenergetics readouts","pmids":["35241643","36099415"],"confidence":"High","gaps":["Whether chromatin accessibility changes at NAMPT are a cause or consequence of NAD+ depletion in progeria needs further dissection","Therapeutic potential of miR-146a inhibition for NAD+ restoration unexplored"]},{"year":2023,"claim":"SIRT1 was identified as a second sirtuin that directly deacetylates and activates NAMPT (complementing SIRT6), and tissue-specific circadian clock dependence on NAMPT was mapped—essential in brown adipose tissue, moderate in white adipose, absent in skeletal muscle.","evidence":"SIRT1-NAMPT Co-IP with deacetylation assay and nicotine-treated aging mice; adipose-specific Nampt KO with clock gene expression and metabolomics","pmids":["36797299","36996103"],"confidence":"High","gaps":["Acetylation site specificity for SIRT1 vs. SIRT6 on NAMPT not compared","Basis for tissue-specific clock dependence on NAMPT unclear"]},{"year":2024,"claim":"Macrophage-intrinsic NAMPT was shown to stabilize HIF-1α for M2 TAM polarization and efferocytosis, while its absence activates STING/type I IFN signaling to enhance anti-tumor immunity—defining NAMPT as a myeloid immune checkpoint; separately, NAMPT→NAD+→SIRT2-mediated LDHA deacetylation was linked to lactate production and follicular development in PCOS.","evidence":"Myeloid-specific Nampt KO with scRNA-seq of tumor microenvironment and STING pathway analysis; Co-IP of LDHA acetylation with FK866/NMN in PCOS rat model","pmids":["38308188","39489197"],"confidence":"High","gaps":["Whether NAMPT-targeted myeloid therapy synergizes with immune checkpoint inhibitors in patients is untested","SIRT2-LDHA-lactate axis in PCOS based on single study with Co-IP, awaits independent validation"]},{"year":null,"claim":"Key unresolved questions include the structural basis of eNAMPT's enzyme-independent cytokine-like activity, the mechanism of NAMPT translocation into the mitochondrial matrix, the full receptor repertoire for eNAMPT signaling across tissues (only CCR5 identified in zebrafish muscle stem cells), and whether therapeutic NAMPT modulation can achieve tissue-selective NAD+ control without pathological consequences.","evidence":"","pmids":[],"confidence":"Low","gaps":["Structural determinants for cytokine vs. enzyme activity on the NAMPT dimer uncharacterized","Mitochondrial import mechanism unknown","Mammalian receptor for enzyme-independent eNAMPT signaling not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[1,2,3,8]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,6,12,18]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[7,11,27]}],"localization":[{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[4,17,24]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[17]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,3,9,15]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[15]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[23]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,2,3,4,8,17,26,32]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[5,6,10,12,21,27]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[6,8,12,18,22]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[5,20]},{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[22]},{"term_id":"R-HSA-9909396","term_label":"Circadian clock","supporting_discovery_ids":[19,26]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[14,23,30]}],"complexes":[],"partners":["SIRT1","SIRT6","SIRT2","SIRT3","PARP1","CCR5","STAT1","HIF1A"],"other_free_text":[]},"mechanistic_narrative":"NAMPT is the rate-limiting enzyme of the mammalian NAD+ salvage pathway, catalyzing the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide (NMN), and thereby governing intracellular NAD+ pools that fuel sirtuins (SIRT1–4), PARP1, and CD38 [PMID:12555668, PMID:17889652, PMID:16783373]. Intracellular NAMPT localizes to both the cytosol and the mitochondrial matrix of neurons and cardiomyocytes, where it sustains compartment-specific NAD+ levels critical for bioenergetics, neuronal survival, and circadian clock amplitude [PMID:31553812, PMID:36441480, PMID:36996103]; its activity is post-translationally enhanced by SIRT6- and SIRT1-mediated deacetylation and transcriptionally regulated by STAT1, REV-ERBα/β–E4BP4, lamin A/C-dependent chromatin accessibility, and miR-146a [PMID:30514106, PMID:36797299, PMID:33976173, PMID:35036997, PMID:35241643, PMID:36099415]. The secreted extracellular form (eNAMPT), released in extracellular vesicles, exerts both enzymatic effects—supporting β-cell insulin secretion and vascular NAD+ supply during aging—and enzyme-independent cytokine-like functions including monocyte activation via NF-κB/MAPK/STAT3 signaling, neutrophil NADPH oxidase priming through p38/ERK-dependent p40/p47 translocation and Rac activation, M2 macrophage polarization, and CCR5-dependent muscle stem cell proliferation during tissue regeneration [PMID:17983582, PMID:31204283, PMID:17237424, PMID:21518975, PMID:25368373, PMID:33568815]. In macrophages, NAMPT stabilizes HIF-1α to promote M2 tumor-associated macrophage polarization and efferocytosis, while its loss enhances STING-mediated type I interferon signaling and anti-tumor immunity [PMID:38308188]."},"prefetch_data":{"uniprot":{"accession":"P43490","full_name":"Nicotinamide phosphoribosyltransferase","aliases":["Pre-B-cell colony-enhancing factor 1","Pre-B cell-enhancing factor","Visfatin"],"length_aa":491,"mass_kda":55.5,"function":"Catalyzes the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide, an intermediate in the biosynthesis of NAD. It is the rate limiting component in the mammalian NAD biosynthesis pathway. The secreted form behaves both as a cytokine with immunomodulating properties and an adipokine with anti-diabetic properties, it has no enzymatic activity, partly because of lack of activation by ATP, which has a low level in extracellular space and plasma. Plays a role in the modulation of circadian clock function. NAMPT-dependent oscillatory production of NAD regulates oscillation of clock target gene expression by releasing the core clock component: CLOCK-BMAL1 heterodimer from NAD-dependent SIRT1-mediated suppression (By similarity)","subcellular_location":"Nucleus; Cytoplasm; Secreted","url":"https://www.uniprot.org/uniprotkb/P43490/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NAMPT","classification":"Not Classified","n_dependent_lines":428,"n_total_lines":1208,"dependency_fraction":0.3543046357615894},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"SAR1B","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/NAMPT","total_profiled":1310},"omim":[{"mim_id":"611552","title":"NICOTINATE PHOSPHORIBOSYLTRANSFERASE; NAPRT","url":"https://www.omim.org/entry/611552"},{"mim_id":"608764","title":"NICOTINAMIDE PHOSPHORIBOSYLTRANSFERASE; NAMPT","url":"https://www.omim.org/entry/608764"},{"mim_id":"604517","title":"PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR-GAMMA, COACTIVATOR 1, ALPHA; PPARGC1A","url":"https://www.omim.org/entry/604517"},{"mim_id":"604479","title":"SIRTUIN 1; SIRT1","url":"https://www.omim.org/entry/604479"},{"mim_id":"601851","title":"CLOCK CIRCADIAN REGULATOR; CLOCK","url":"https://www.omim.org/entry/601851"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nuclear speckles","reliability":"Approved"},{"location":"Cell Junctions","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in all","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":339.4}],"url":"https://www.proteinatlas.org/search/NAMPT"},"hgnc":{"alias_symbol":["PBEF"],"prev_symbol":["PBEF1"]},"alphafold":{"accession":"P43490","domains":[{"cath_id":"3.20.140.10","chopping":"10-159_398-480","consensus_level":"high","plddt":94.1142,"start":10,"end":480},{"cath_id":"3.20.20.70","chopping":"175-381","consensus_level":"medium","plddt":97.1008,"start":175,"end":381}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P43490","model_url":"https://alphafold.ebi.ac.uk/files/AF-P43490-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P43490-F1-predicted_aligned_error_v6.png","plddt_mean":94.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NAMPT","jax_strain_url":"https://www.jax.org/strain/search?query=NAMPT"},"sequence":{"accession":"P43490","fasta_url":"https://rest.uniprot.org/uniprotkb/P43490.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P43490/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P43490"}},"corpus_meta":[{"pmid":"17983582","id":"PMC_17983582","title":"Nampt/PBEF/Visfatin regulates insulin secretion in beta cells as a systemic NAD biosynthetic enzyme.","date":"2007","source":"Cell metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/17983582","citation_count":761,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"26215259","id":"PMC_26215259","title":"Physiological and pathophysiological roles of NAMPT and NAD metabolism.","date":"2015","source":"Nature reviews. 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communications","url":"https://pubmed.ncbi.nlm.nih.gov/36797299","citation_count":62,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"26358657","id":"PMC_26358657","title":"Nicotinamide phosphoribosyltransferase (NAMPT/PBEF/visfatin) is a tumoural cytokine released from melanoma.","date":"2015","source":"Pigment cell & melanoma research","url":"https://pubmed.ncbi.nlm.nih.gov/26358657","citation_count":62,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"19485930","id":"PMC_19485930","title":"Visfatin/PBEF and atherosclerosis-related diseases.","date":"2010","source":"Current vascular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/19485930","citation_count":60,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"25656579","id":"PMC_25656579","title":"FK866-induced NAMPT inhibition activates AMPK and downregulates mTOR signaling in hepatocarcinoma cells.","date":"2015","source":"Biochemical and biophysical research 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metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/31204283","citation_count":326,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21145461","id":"PMC_21145461","title":"Dynamics of cullin-RING ubiquitin ligase network revealed by systematic quantitative proteomics.","date":"2010","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/21145461","citation_count":318,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"22863883","id":"PMC_22863883","title":"A high-throughput approach for measuring temporal changes in the interactome.","date":"2012","source":"Nature methods","url":"https://pubmed.ncbi.nlm.nih.gov/22863883","citation_count":273,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"17307730","id":"PMC_17307730","title":"Extension of human cell lifespan by nicotinamide phosphoribosyltransferase.","date":"2007","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/17307730","citation_count":271,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16449335","id":"PMC_16449335","title":"Increased plasma visfatin concentrations in morbidly obese subjects are reduced after gastric banding.","date":"2006","source":"The Journal of clinical endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/16449335","citation_count":244,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":47617,"output_tokens":7107,"usd":0.124728},"stage2":{"model":"claude-opus-4-6","input_tokens":10875,"output_tokens":3732,"usd":0.221513},"total_usd":0.766892,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of 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\"iNampt is the rate-limiting enzyme in the NAD biosynthetic salvage pathway from nicotinamide; haplodeficiency or chemical inhibition reduces NAD biosynthesis and glucose-stimulated insulin secretion in pancreatic islets, defects rescued by NMN (the product of the Nampt reaction). eNampt exhibits robust NAD biosynthetic activity rather than insulin-mimetic effects.\",\n      \"method\": \"Heterozygous knockout mice, chemical inhibition, in vitro and in vivo insulin secretion assays, NMN rescue experiments\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (KO, chemical inhibition, product rescue) in vivo and in vitro, 761 citations\",\n      \"pmids\": [\"17983582\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"NAMPT is the rate-limiting enzyme converting nicotinamide to NMN in the mammalian NAD biosynthetic salvage pathway, and mammals predominantly use nicotinamide rather than nicotinic acid as the NAD precursor.\",\n      \"method\": \"Biochemical characterization and review of enzymatic pathway evidence\",\n      \"journal\": \"Current opinion in gastroenterology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — consistent with structural and genetic data across multiple independent labs\",\n      \"pmids\": [\"17268245\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Extracellular PBEF/NAMPT activates pro-inflammatory signaling (iNOS induction) in human vascular smooth muscle cells via its intrinsic NAMPT enzymatic activity; NMN (the product) mimics NF-κB activation and iNOS induction, while APO866 (NAMPT inhibitor) blocks these effects. The pathway requires sequential ERK1/2 and NF-κB activation.\",\n      \"method\": \"Western blotting, EMSA (NF-κB), pharmacological inhibitors (PD98059, pyrrolidine dithiocarbamate, APO866), NMN supplementation\",\n      \"journal\": \"Diabetologia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods linking enzymatic activity to downstream signaling\",\n      \"pmids\": [\"19727662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Human hepatocytes constitutively release the dimeric form of NAMPT with enzymatic activity into the extracellular space, establishing hepatocytes as a source of circulating eNAMPT.\",\n      \"method\": \"HepG2 cells and primary hepatocyte culture, size exclusion chromatography, in vitro enzymatic activity assay\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct fractionation and enzymatic assay, single lab\",\n      \"pmids\": [\"19912992\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PBEF/NAMPT is highly expressed in neurons (not glial cells) in mouse brain; Pbef+/- heterozygous knockout mice have lower NAD+ levels and develop larger cerebral infarct volumes after photothrombosis, demonstrating a neuroprotective role through NAD+-dependent energy metabolism.\",\n      \"method\": \"Immunostaining, heterozygous knockout mice, photothrombosis model, Fluoro-Jade B staining\",\n      \"journal\": \"Journal of cerebral blood flow and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotype and mechanistic link to NAD+ levels\",\n      \"pmids\": [\"20485294\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PBEF/NAMPT primes neutrophils for augmented respiratory burst (NADPH oxidase activation) by promoting membrane translocation of cytosolic NADPH oxidase subunits p40 and p47, inducing p40 phosphorylation on Thr154, and activating Rac GTPase, in a p38/ERK MAPK-dependent manner; this priming is independent of NAMPT's NAD-generating capacity.\",\n      \"method\": \"ROS assay, membrane fractionation, phosphorylation western blotting, pharmacological inhibitors, APO866 treatment showing NAD-independent effect\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods, clear mechanistic dissection separating enzymatic from non-enzymatic function\",\n      \"pmids\": [\"21518975\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Nampt-mediated NAD biosynthesis regulates SIRT1 activity and osteogenic differentiation; knockdown of Nampt or FK866 treatment reduces intracellular NAD concentration and impairs osteogenesis in multipotent and preosteoblast progenitor cells.\",\n      \"method\": \"siRNA knockdown, FK866 inhibition, NAD measurement, differentiation assays in C3H10T1/2 and MC3T3-E1 cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KD plus chemical inhibition with specific cellular phenotype, single lab\",\n      \"pmids\": [\"23537654\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Forebrain excitatory neurons primarily use intracellular Nampt-mediated NAD+ biosynthesis for their survival and function; CaMKIIα-specific Nampt knockout mice develop hippocampal/cortical atrophy, astrogliosis, microgliosis, abnormal dendritic morphology, altered intrahippocampal connectivity, and memory impairment.\",\n      \"method\": \"Conditional neuron-specific Nampt knockout (CaMKIIαNampt−/− mice), histology, behavioral testing, electrophysiology\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific KO with defined morphological, connectivity, and behavioral phenotypes\",\n      \"pmids\": [\"24760840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Extracellular NAMPT (eNAMPT) polarizes resting monocytes toward tumor-supporting M2 macrophages (expressing CD163, CD206, IDO) in CLL via a mechanism independent of its enzymatic activity, as demonstrated using an enzymatically inactive NAMPT mutant.\",\n      \"method\": \"Co-culture assays, flow cytometry, cytokine measurement, enzymatically inactive NAMPT mutant\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — inactive mutant controls definitively separate enzymatic from non-enzymatic function, moderate evidence\",\n      \"pmids\": [\"25368373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"FK866-induced NAMPT inhibition activates AMPK and downregulates mTORC1 signaling (p70S6K, 4E-BP1) in hepatocarcinoma cells but not non-cancerous hepatocytes; these effects are rescued by NMN, linking NAMPT activity to AMPK/mTOR pathway regulation.\",\n      \"method\": \"FK866 treatment, NMN rescue, western blotting for AMPK/mTOR pathway, NAD and ATP measurement, cell viability assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pharmacological inhibition with product rescue and pathway analysis, single lab\",\n      \"pmids\": [\"25656579\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"extracellular NAMPT (visfatin) increases intracellular and extracellular NAD concentrations, activates SIRT1, and induces p53 deacetylation in breast cancer cells; the proliferative effect of visfatin is abolished by inhibition of its enzymatic activity.\",\n      \"method\": \"NAD colorimetric assay, SIRT1 fluorescence activity assay, western blotting for p53 acetylation, enzymatic inhibitor treatment\",\n      \"journal\": \"Cell biochemistry and function\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, multiple related assays but limited mechanistic depth\",\n      \"pmids\": [\"28845527\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SIRT6 directly deacetylates NAMPT protein, upregulating NAMPT enzymatic activity and consequently increasing NAD(H) and NADPH levels; SIRT6 silencing enhances extracellular NAMPT release.\",\n      \"method\": \"Immunopurification of NAMPT, incubation with recombinant SIRT6, enzymatic activity assays, SIRT6 overexpression/silencing in cancer cells, NAD(P)(H) measurement\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted direct deacetylation of purified NAMPT by recombinant SIRT6 plus cellular validation\",\n      \"pmids\": [\"30514106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NAMPT maintains cardiac function and NAD levels under pressure overload; heterozygous Nampt knockout mice show NAD decline and exacerbated heart failure, while cardiac-specific Nampt overexpression is also detrimental due to excessive SIRT1 activation, suppression of metabolic genes, and upregulation of inflammatory cytokines (TNF-α, MCP-1). In cardiomyocytes, Nampt knockdown reduces mitochondrial NAD and ATP production.\",\n      \"method\": \"Cardiac-specific Nampt transgenic mice, heterozygous KO mice, pressure overload model, NAD measurement, mitochondrial respiration assays, protein acetylation analysis\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — both gain- and loss-of-function genetic models with defined metabolic phenotypes\",\n      \"pmids\": [\"31347918\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NAMPT inhibition in primary hypothalamic neurons reduces NAD+, increases ROS, and affects Agrp, Pomc, and mitochondrial gene expression; intracerebroventricular NAMPT inhibition by FK866 completely ablates fasting- and ghrelin-induced food intake in mice.\",\n      \"method\": \"FK866 treatment of primary neurons, rAAV-shRNA knockdown, ROS measurement, mitochondrial respiration assay, metabolic cage ICV administration\",\n      \"journal\": \"Acta physiologica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro and in vivo pharmacological inhibition with defined behavioral and molecular phenotypes\",\n      \"pmids\": [\"31900990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NAMPT is localized in neuronal mitochondrial matrix (alongside NMNAT3), and neuronal mitochondria possess an intact NAMPT-mediated NAD+ salvage pathway; mitochondrial, cytoplasmic, and non-compartmental NAMPT overexpression comparably protect neurons against ischemia and suppress AIF translocation.\",\n      \"method\": \"Subcellular fractionation, viral overexpression of targeted transgenes, siRNA knockdown of NMNATs, confocal microscopy, oxygen-glucose deprivation model\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct fractionation plus multiple siRNA/overexpression approaches with functional readouts\",\n      \"pmids\": [\"31553812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NAMPT is a direct transcriptional target of STAT1 via a conserved intronic element (NRE1); IFNγ-driven STAT1 occupancy of NRE1 induces NAMPT expression, which supports glycolysis and a subset of M1 macrophage inflammatory genes; NRE1 disruption reduces NAMPT and inflammatory gene expression in tumor-associated macrophages and increases tumor burden.\",\n      \"method\": \"ChIP-seq (STAT1 occupancy of NRE1), NRE1-disruption mouse strain, scRNA-seq of tumor-infiltrating leukocytes, NAMPT pharmacological inhibition, macrophage-lineage specific NRE1 ablation\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct ChIP evidence plus genetic disruption of regulatory element with in vivo tumor phenotype\",\n      \"pmids\": [\"33976173\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Macrophage-secreted Nampt acts as a niche signal for muscle stem cell (satellite cell) proliferation after injury, signaling through CCR5 expressed on muscle stem cells; macrophage-specific Nampt secretion is required for muscle regeneration in zebrafish.\",\n      \"method\": \"Zebrafish live imaging of satellite cell-macrophage interactions, single-cell profiling, genetic/pharmacological inhibition of Nampt secretion, CCR5 pathway analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic in vivo genetic and live imaging approach identifying receptor (CCR5) and secreting cell type, 178 citations\",\n      \"pmids\": [\"33568815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NAMPT-derived NAD+ fuels PARP1 hyperactivation; genetic or pharmacological inhibition of Nampt reduces oxidative stress, inflammation, keratinocyte DNA damage and parthanatos cell death in zebrafish skin inflammation models; effects are reversed by NAD+ supplementation and phenocopied by PARP1 inhibition or AIFM1 inhibition.\",\n      \"method\": \"Genetic Nampt knockout in zebrafish, pharmacological inhibition (FK866), NAD+ supplementation rescue, PARP1/AIFM1 inhibitors, human psoriasis organotypic 3D skin models, patient biopsy analysis\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — genetic KO with pharmacological rescue and epistasis across multiple model systems\",\n      \"pmids\": [\"34748530\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"REV-ERBα/β transcriptionally repress E4BP4, which in turn directly controls circadian expression of Nampt via distal cis-regulatory elements; REV-ERB-mediated E4BP4 repression is required for Nampt expression and NAD+ production by the salvage pathway in cardiomyocytes.\",\n      \"method\": \"Cardiomyocyte-specific Rev-erb double knockout mice, ChIP/genomic analysis of E4BP4 binding to Nampt regulatory elements, NAD+ measurement\",\n      \"journal\": \"Nature cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific genetic KO with identified transcriptional regulatory mechanism\",\n      \"pmids\": [\"35036997\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SIRT1 binds to and deacetylates NAMPT, increasing its enzymatic activity and NAD+ synthesis; nicotine (independent of nicotinic acetylcholine receptors) restores age-related decline in NAMPT activity through SIRT1-mediated deacetylation.\",\n      \"method\": \"SIRT1 binding assay, deacetylation assay, 18F-FDG PET imaging, aging mouse models\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct binding and deacetylation demonstrated, but detailed mechanistic controls not fully described in abstract\",\n      \"pmids\": [\"36797299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NAMPT depletion in hippocampal CA1 neurons causes mitochondrial swelling and reduced mitochondrial number, increased intracellular Aβ aggregation, neuroinflammation (GFAP, Iba1 upregulation), and cognitive deficiency; FK866-mediated NAMPT inhibition reduces mitochondrial membrane potential and NAD+ levels in primary neurons.\",\n      \"method\": \"rAAV-hSyn-Cre hippocampal injection in Namptflox/flox mice, transmission electron microscopy, immunofluorescence, FK866 treatment of primary neurons, mitochondrial membrane potential assay\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific conditional KO with ultrastructural and functional phenotypes\",\n      \"pmids\": [\"36441480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Lamin A/C regulates NAMPT expression through chromatin accessibility at the Nampt gene promoter; lamin A/C-null MEFs show reduced NAMPT expression, decreased NAD+, attenuated SIRT1 activity, and mitochondrial dysfunction; ATAC-seq revealed reduced chromatin accessibility at the Nampt promoter in Lmna-/- cells.\",\n      \"method\": \"Lmna-/- MEFs, HGPS fibroblasts, ATAC-seq, NAD+ measurement, SIRT1 activity assay, mitochondrial function assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — ATAC-seq plus functional validation in two independent disease models\",\n      \"pmids\": [\"36099415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"miR-146a directly targets the 3'-UTR of Nampt mRNA to suppress NAMPT expression and NAD+/SIRT activity; AMPK activators (metformin, AICAR) suppress miR-146a transcription by promoting IKK phosphorylation and attenuating NF-κB activity, thereby relieving repression of NAMPT.\",\n      \"method\": \"miR-146a overexpression/inhibition, 3'-UTR reporter assay, NAMPT protein measurement, NAD+ assay, SIRT activity assay, in vitro and in vivo aging models\",\n      \"journal\": \"Signal transduction and targeted therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct 3'-UTR validation plus upstream pathway dissection, confirmed in vitro and in vivo\",\n      \"pmids\": [\"35241643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CircRNA FEACR directly binds to NAMPT protein, enhancing its stability; FEACR-stabilized NAMPT increases SIRT1-dependent FOXO1 deacetylation, which upregulates Fth1 transcription, suppressing ferroptosis in cardiomyocytes during ischemia/reperfusion.\",\n      \"method\": \"RNA pull-down, circRNA sequencing, gain/loss-of-function, I/R mouse model, western blotting for NAMPT, Sirt1, FOXO1 acetylation, Fth1\",\n      \"journal\": \"Journal of biomedical science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — RNA pull-down establishes direct binding, pathway traced by sequential KD/OE, single lab\",\n      \"pmids\": [\"37370086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NAMPT deficiency in macrophages causes HIF-1α destabilization, reducing M2-like tumor-associated macrophage polarization; NAMPT-deficient macrophages show decreased efferocytosis, enhanced STING signaling, type I IFN responses, and augmented cytotoxic T cell activity in the tumor microenvironment.\",\n      \"method\": \"Myeloid-specific Nampt conditional knockout mice, CRC tumor model, scRNA-seq, flow cytometry, STING signaling analysis\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — myeloid-specific KO with defined cellular and signaling phenotypes in vivo\",\n      \"pmids\": [\"38308188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NAMPT interacts with NADH dehydrogenase subunit 1 (ND1), ferritin light chain, and interferon-induced transmembrane protein 3 (IFITM3) in human pulmonary vascular endothelial cells; NAMPT overexpression increases these interactions and intracellular oxidative stress.\",\n      \"method\": \"Co-immunoprecipitation/pulldown (protein interaction identification and validation), overexpression in endothelial cells, oxidative stress measurement\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single pulldown/Co-IP identification without detailed mechanistic follow-up\",\n      \"pmids\": [\"18486613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NAMPT-dependent NAD+ control over the molecular clock is highly tissue-specific: brown adipose tissue (BAT) requires NAMPT to sustain core clock amplitude and TCA cycle metabolite rhythmicity, white adipose tissue shows moderate dependence, and skeletal muscle clock is refractory to NAMPT loss.\",\n      \"method\": \"Tissue-specific Nampt knockout, circadian clock gene expression profiling, metabolomics, NAD+ measurement\",\n      \"journal\": \"PNAS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple tissue-specific conditional KOs with metabolomics and clock gene readouts\",\n      \"pmids\": [\"36996103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NAMPT overexpression promotes cell survival under oxidative stress via both SIRT1-dependent p53-CD38 pathway and a SIRT1-independent NRF2-PPARα/AMPKα pathway; activated NRF2-PPARα/AMPKα rescues mitochondrial membrane potential and content, maintaining mitochondrial NAD+ levels.\",\n      \"method\": \"NAMPT overexpression in cancer cells, H2O2 treatment, mitochondrial membrane potential assay, NRF2/AMPK/PPARα pathway analysis, SIRT1 inhibition\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — overexpression with pathway analysis, single lab, no genetic confirmation\",\n      \"pmids\": [\"31816398\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NAMPT pathway regulates GADD45A expression through FOXO3a acetylation: NAMPT inhibition by FK866 increases FOXO3a acetylation (via SIRT1 inactivation), which upregulates GADD45A; NAMPT overexpression conversely decreases GADD45A.\",\n      \"method\": \"FK866 treatment, NAMPT overexpression, SIRT1 shRNA, FOXO3a acetylation analysis, GADD45A expression measurement\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — pharmacological and genetic perturbation with pathway readout, single lab\",\n      \"pmids\": [\"22430142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NAMPT-mediated NAD+ controls SIRT2-dependent deacetylation of LDHA; inhibition of NAD+ synthesis enhances LDHA acetylation (demonstrated by Co-IP), reduces LDHA activity, and decreases lactate production in granulosa cells, impairing follicular development.\",\n      \"method\": \"Co-immunoprecipitation (LDHA acetylation), FK866 NAMPT inhibition, NMN supplementation rescue in PCOS rat model, KGN cell assays\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP for acetylation plus in vivo NMN rescue, mechanistic chain established\",\n      \"pmids\": [\"39489197\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NAMPT is a dimeric type II phosphoribosyltransferase that catalyzes the rate-limiting conversion of nicotinamide to NMN in the NAD+ salvage biosynthetic pathway; intracellular NAMPT (iNAMPT) maintains cellular NAD+ pools to fuel SIRT1, SIRT2, SIRT6, PARP1, and other NAD+-consuming enzymes—thereby regulating metabolism, circadian rhythms, DNA repair, apoptosis, and tissue-specific functions including pancreatic beta-cell insulin secretion and neuronal survival—while extracellular NAMPT (eNAMPT) acts as a cytokine with both enzymatic (NMN/NAD+-producing) and non-enzymatic (receptor-mediated, e.g., via CCR5 or TLR4) signaling functions in macrophage polarization, neutrophil priming, muscle stem cell activation, and inflammation; NAMPT activity is post-translationally regulated by SIRT6-mediated deacetylation (activating) and SIRT1-mediated deacetylation (activating), and transcriptionally controlled by STAT1 (via NRE1 enhancer), REV-ERB/E4BP4 circadian axis, and miR-146a-mediated suppression downstream of NF-κB.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1994,\n      \"finding\": \"NAMPT (then called PBEF) was originally cloned from a human peripheral blood lymphocyte cDNA library as a secreted 52-kDa protein that synergizes with stem cell factor and IL-7 to enhance pre-B-cell colony formation, establishing it as a cytokine acting on early B-lineage precursor cells.\",\n      \"method\": \"cDNA library screening, expression in COS7/PA317 cells, in vitro B-cell colony formation assay\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — original cloning and functional characterization with direct biological assay\",\n      \"pmids\": [\"8289818\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"PBEF/NAMPT was identified as a nicotinamide phosphoribosyltransferase (NAmPRTase), catalyzing the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide (NMN), an intermediate in NAD biosynthesis; the mouse gene complemented a NAmPRTase-defective bacterial strain, confirming enzymatic function.\",\n      \"method\": \"Enzymatic activity assay, bacterial complementation assay, antibody panel characterization\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct enzymatic assay plus genetic complementation, foundational identification\",\n      \"pmids\": [\"12555668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Crystal structure of NAMPT (with and without NMN bound) revealed it is a dimeric type II phosphoribosyltransferase, providing structural insights into the enzymatic mechanism of NMN synthesis.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Nature structural & molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with and without product, high-resolution mechanistic insight\",\n      \"pmids\": [\"16783373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Haplodeficiency and chemical inhibition of NAMPT cause defects in NAD biosynthesis and glucose-stimulated insulin secretion in pancreatic islets; extracellular NAMPT (eNAMPT) exerts its effects through NAD biosynthetic activity (producing NMN) rather than insulin-mimetic hormone activity, as administration of NMN rescues the defects.\",\n      \"method\": \"Nampt heterozygous knockout mice, chemical inhibition, NMN rescue experiments, in vitro and in vivo glucose-stimulated insulin secretion assays\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal genetic and pharmacological methods with defined phenotypic rescue, highly cited foundational study\",\n      \"pmids\": [\"17983582\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"NAMPT is the rate-limiting enzyme in the NAD+ salvage pathway from nicotinamide in mammals; increased NAMPT expression under fasting conditions elevates mitochondrial NAD+ levels and provides protection against cell death, requiring mitochondrial NAD+-dependent deacetylases SIRT3 and SIRT4.\",\n      \"method\": \"Fasting experiments in rodents, subcellular fractionation, siRNA knockdown, cell viability assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods including genetic knockdown and fractionation, highly cited\",\n      \"pmids\": [\"17889652\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"PBEF/NAMPT functions as a novel inhibitor of neutrophil apoptosis in response to inflammatory stimuli (LPS, IL-1, GM-CSF, IL-8, TNF-α); antisense oligonucleotide blockade of PBEF translation completely abrogates LPS-induced neutrophil apoptosis delay, and inhibition is associated with reduced caspase-8 and caspase-3 activity.\",\n      \"method\": \"Antisense oligonucleotide, recombinant protein treatment, caspase activity assays, apoptosis quantification\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function with antisense and gain-of-function with recombinant protein, well-defined mechanism, highly cited\",\n      \"pmids\": [\"15124023\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Extracellular visfatin (NAMPT) activates human leukocytes and induces cytokine production (IL-1β, TNF-α, IL-6) in CD14+ monocytes, increases costimulatory molecule expression (CD54, CD40, CD80), and activates NF-κB via p38 and MEK1 MAPK pathways.\",\n      \"method\": \"Recombinant protein treatment, MAPK inhibitor experiments, NF-κB activation assays, cytokine ELISA, flow cytometry\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple signaling pathway inhibitors used, replicated across multiple readouts, highly cited\",\n      \"pmids\": [\"17237424\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"NAMPT-mediated NAD+ biosynthesis extends the lifespan of human vascular smooth muscle cells through increased SIRT1 activity and reduced p53 acetylation (K382) and degradation; a dominant-negative SIRT1 abrogates the anti-aging effect, placing NAMPT upstream of SIRT1 in this pathway.\",\n      \"method\": \"Nampt gene overexpression, FK866 inhibitor, dominant-negative SIRT1 transduction, senescence-associated β-galactosidase assay, p53 acetylation western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with dominant-negative, multiple orthogonal methods, clearly defined pathway order\",\n      \"pmids\": [\"17307730\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Extracellular NAMPT activates pro-inflammatory signaling in human vascular smooth muscle cells through its intrinsic enzymatic activity: it induces iNOS via sequential ERK1/2 and NF-κB activation; exogenous NMN (the product of NAMPT) mimics these effects, while the NAMPT inhibitor APO866 blocks them, demonstrating the enzymatic activity is required.\",\n      \"method\": \"Western blotting, EMSA (NF-κB), ERK inhibitor PD98059, NF-κB inhibitor, APO866, exogenous NMN treatment\",\n      \"journal\": \"Diabetologia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — NMN mimicry and inhibitor block establish enzymatic activity as mechanism, multiple signaling readouts\",\n      \"pmids\": [\"19727662\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Human hepatocytes constitutively release NAMPT into the extracellular compartment; secreted NAMPT exists primarily as the dimeric form and retains enzymatic activity; hepatocyte NAMPT secretion is not regulated by glucose, insulin, or TNF-α.\",\n      \"method\": \"Size exclusion chromatography, in vitro enzymatic activity assay, HepG2 cells and primary human hepatocytes\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — enzymatic activity confirmed in secreted fraction, multiple cell types tested, single lab\",\n      \"pmids\": [\"19912992\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Extracellular PBEF/NAMPT primes neutrophils for augmented NADPH oxidase-dependent respiratory burst by promoting membrane translocation of cytosolic NADPH oxidase subunits p40 and p47 (but not p67), inducing p40 phosphorylation on Thr154, and activating Rac GTPase; this priming is dependent on p38 and ERK MAPK but is independent of NAMPT's NAD-generating capacity (NMN or NAD cannot recapitulate the effect, and APO866 does not block it).\",\n      \"method\": \"Membrane fractionation, phosphorylation assays, Rac GTPase activation assay, MAPK inhibitors, APO866 inhibitor, ROS measurement\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods establishing enzyme-independent mechanism, clearly dissected from enzymatic activity\",\n      \"pmids\": [\"21518975\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"NAMPT enzymatic activity regulates GADD45A expression through the NAMPT→NAD+→SIRT1→FOXO3a acetylation axis: NAMPT overexpression decreases GADD45A expression, while NAMPT inhibition by FK866 or SIRT1 knockdown increases GADD45A; the increase involves acetylation of FOXO3a.\",\n      \"method\": \"NAMPT overexpression, FK866 inhibitor, SIRT1 shRNA, western blotting, gene expression analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic and pharmacological perturbations with pathway readouts, single lab\",\n      \"pmids\": [\"22430142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Extracellular NAMPT (eNAMPT) promotes M2 macrophage polarization in chronic lymphocytic leukemia independently of its enzymatic activity, as demonstrated by use of an enzymatically inactive mutant; eNAMPT is produced by CLL lymphocytes upon BCR, TLR, and NF-κB signaling activation and polarized macrophages activate ERK1/2, STAT3, and NF-κB signaling.\",\n      \"method\": \"Enzymatically inactive NAMPT mutant, monocyte differentiation assays, flow cytometry, cytokine profiling, signaling pathway western blots\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — enzymatic mutant used to dissect enzyme-independent function, multiple signaling readouts, key mechanistic distinction\",\n      \"pmids\": [\"25368373\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Forebrain excitatory neurons primarily use intracellular NAMPT-mediated NAD+ biosynthesis for their survival and function; CaMKIIα-specific Nampt knockout mice develop hippocampal/cortical atrophy, astrogliosis, microgliosis, abnormal CA1 dendritic morphology, altered intrahippocampal connectivity, and behavioral impairments including memory deficits.\",\n      \"method\": \"Conditional (CaMKIIα-Cre) Nampt knockout mice, histology, electrophysiology, behavioral testing\",\n      \"journal\": \"The Journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type specific genetic knockout with defined structural and functional phenotypes, multiple orthogonal readouts\",\n      \"pmids\": [\"24760840\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"SIRT6 directly deacetylates NAMPT (identified by immunopurification and incubation with recombinant SIRT6), and this deacetylation upregulates NAMPT enzymatic activity, increasing intracellular NAD(H) levels and protecting cancer cells against oxidative stress.\",\n      \"method\": \"Immunopurification, recombinant SIRT6 incubation, SIRT6 overexpression/silencing in cancer cells, NAD(H) measurement, enzymatic activity assay\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro reconstitution of SIRT6-NAMPT deacetylation, functional validation in cells\",\n      \"pmids\": [\"30514106\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Extracellular NAMPT (eNAMPT) is carried in extracellular vesicles (EVs) through systemic circulation in mice and humans; EV-contained eNAMPT is internalized into cells and enhances NAD+ biosynthesis; supplementing eNAMPT-containing EVs from young mice improves physical activity and extends lifespan in aged mice.\",\n      \"method\": \"EV isolation, internalization assays, NAD+ measurement, adipose-tissue-specific NAMPT overexpression, lifespan and wheel-running experiments in mice\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — mechanistic EV delivery established with multiple methods, functional consequence demonstrated in vivo\",\n      \"pmids\": [\"31204283\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Both loss and gain of Nampt function exacerbate pressure-overload-induced heart failure; Nampt knockdown diminishes mitochondrial NAD content and ATP production in cardiomyocytes; Nampt overexpression increases Sirt1 expression and activity, causing excessive suppression of mitochondrial proteins and metabolic genes plus upregulation of inflammatory cytokines.\",\n      \"method\": \"Nampt+/- heterozygous KO mice, cardiac-specific Nampt transgenic mice, pressure overload model, mitochondrial NAD/ATP measurement, protein acetylation analysis\",\n      \"journal\": \"American journal of physiology. Heart and circulatory physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — complementary gain- and loss-of-function models with mechanistic readouts, multiple orthogonal measurements\",\n      \"pmids\": [\"31347918\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NAMPT is localized within the mitochondrial matrix of neurons (alongside NMNAT3), where it maintains an intact NAD+ salvage pathway; NMNAT3 knockdown has a larger effect on mitochondrial respiration than NMNAT1/2, while NMNAT1/2 affect glycolytic flux more; mitochondrial, cytoplasmic, and non-compartmental NAMPT overexpression all provide comparable neuronal protection and suppression of apoptosis-inducing factor translocation after ischemia.\",\n      \"method\": \"Subcellular fractionation, siRNA knockdown of NMNAT1-3 and NAMPT, confocal microscopy, oxygen glucose deprivation model, mitochondrial respiration assay\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct subcellular fractionation and localization combined with functional knockdown experiments\",\n      \"pmids\": [\"31553812\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Macrophage-derived eNAMPT (secreted from a specific 'dwelling' macrophage subset) is required for muscle stem cell (satellite cell) proliferation and muscle regeneration in zebrafish; eNAMPT acts through the C-C motif chemokine receptor CCR5 expressed on muscle stem cells.\",\n      \"method\": \"Zebrafish muscle injury models, single-cell profiling, real-time in vivo imaging, genetic perturbation of NAMPT/CCR5\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — receptor identified (CCR5), in vivo genetic requirement established, high-profile journal\",\n      \"pmids\": [\"33568815\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Circadian clock components REV-ERBα/β repress E4BP4, which directly controls the circadian expression of Nampt via distal cis-regulatory elements; loss of Rev-erbs induces E4BP4 and downregulates Nampt, reducing NAD+ production via the salvage pathway and causing dilated cardiomyopathy.\",\n      \"method\": \"Cardiomyocyte-specific Rev-erb double knockout mice, chromatin occupancy (ChIP), NAD+ measurement, gene expression analysis\",\n      \"journal\": \"Nature cardiovascular research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis with tissue-specific KO and chromatin-level mechanistic dissection\",\n      \"pmids\": [\"35036997\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NAMPT-derived NAD+ fuels PARP1 hyperactivation in response to ROS-induced DNA damage, promoting parthanatos cell death and skin inflammation; genetic and pharmacological inhibition of NAMPT reduces oxidative stress, PARP1 activity, AIFM1 nuclear translocation, and keratinocyte hyperproliferation in zebrafish models and human 3D skin models of psoriasis.\",\n      \"method\": \"Zebrafish genetic/pharmacological inhibition models, human organotypic 3D skin models, PARP activity measurement, AIFM1 localization, gene expression analysis\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple model systems, genetic and pharmacological approaches, defined pathway: NAMPT→NAD+→PARP1→parthanatos\",\n      \"pmids\": [\"34748530\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"STAT1 occupies a conserved intronic element (NRE1) within the Nampt gene in response to IFN-γ, driving NAMPT expression in macrophages; disruption of NRE1 reduces a subset of M1 inflammatory gene expression dependent on NAMPT-supported glycolysis, and myeloid-specific NRE1 ablation increases tumor burden in melanoma models.\",\n      \"method\": \"ChIP of STAT1 at NRE1, NRE1 knockout mouse strain, scRNAseq of tumor-associated leukocytes, pharmacological NAMPT inhibition, glycolysis assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo genetic evidence with STAT1 ChIP and novel mouse strain, defined transcriptional mechanism\",\n      \"pmids\": [\"33976173\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"miR-146a directly targets the 3'-UTR of Nampt mRNA to reduce NAMPT expression, thereby impairing AMPK-driven NAD+ synthesis and SIRT activity; AMPK activators (metformin, AICAR) suppress miR-146a transcription by promoting IKK phosphorylation and attenuating NF-κB activity, establishing a mutual inhibitory relationship between miR-146a and AMPK that regulates the NAD+/SIRT pathway.\",\n      \"method\": \"miR-146a overexpression/inhibition, 3'-UTR luciferase assay, NAMPT expression analysis, SIRT activity measurement, NF-κB/IKK assays, in vitro and in vivo experiments\",\n      \"journal\": \"Signal transduction and targeted therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct 3'-UTR targeting validated, pathway epistasis established in vitro and in vivo\",\n      \"pmids\": [\"35241643\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Lamin A/C deficiency causes reduced chromatin accessibility at the Nampt gene promoter (by ATAC-seq), leading to decreased NAMPT expression and reduced SIRT1 activity, which together impair NAD+ levels and mitochondrial function; high PARylation in lamin-aberrant cells further depletes the NAD+ pool.\",\n      \"method\": \"Lmna-/- MEFs, HGPS fibroblasts, ATAC-seq, NAD+ measurement, SIRT1 activity, mitochondrial DNA stability, bioenergetics assays\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — ATAC-seq identifies chromatin mechanism, multiple cell models, orthogonal functional readouts\",\n      \"pmids\": [\"36099415\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"NAMPT depletion specifically in hippocampal CA1 neurons (via rAAV-Cre) causes cognitive deficiency, mitochondrial swelling and decreased mitochondrial number in neuronal cell bodies and neurites, increased intracellular Aβ aggregation, and gliosis; FK866 inhibition decreases neuronal NAD+, drops mitochondrial membrane potential, and reduces neuronal branching in a dose-dependent manner.\",\n      \"method\": \"rAAV-hSyn-Cre hippocampal CA1-specific Nampt KO, transmission electron microscopy, immunofluorescence, FK866 dose-response in primary neurons, mitochondrial membrane potential assay\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — region-specific in vivo KO combined with in vitro mechanistic assays, structural and functional phenotypes\",\n      \"pmids\": [\"36441480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NAMPT activity is restored in aging by SIRT1 binding and subsequent deacetylation of NAMPT; low-dose nicotine activates this mechanism independently of nicotinic acetylcholine receptors, increasing NAD+ synthesis and ameliorating age-related metabolic and cognitive decline in mice.\",\n      \"method\": \"SIRT1-NAMPT co-immunoprecipitation, NAMPT deacetylation assay, 18F-FDG PET imaging, in vivo nicotine treatment of aging mice, cognitive and metabolic assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP identifies SIRT1 as NAMPT deacetylase, functional in vivo validation with multiple readouts\",\n      \"pmids\": [\"36797299\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NAMPT-dependent NAD+ biosynthesis controls the molecular circadian clock in a tissue-specific manner: brown adipose tissue (BAT) requires NAMPT to sustain core clock amplitude and TCA cycle intermediate oscillations, white adipose tissue is moderately dependent, and skeletal muscle clock is completely refractory to NAMPT loss.\",\n      \"method\": \"Adipose-specific Nampt knockout mice, core clock gene expression, metabolomics, cold stress experiments\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — tissue-specific KO with comprehensive molecular and metabolic profiling, mechanistic tissue specificity established\",\n      \"pmids\": [\"36996103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NAMPT deficiency in macrophages causes HIF-1α destabilization, leading to reduced M2-like tumor-associated macrophage (TAM) polarization and decreased efferocytosis; NAMPT deficiency also enhances STING signaling and type I IFN-response gene expression, potentiating cytotoxic T cell anti-tumor activity in colorectal cancer.\",\n      \"method\": \"Myeloid-specific Nampt knockout mice, scRNA-seq of tumor microenvironment, HIF-1α stability assay, efferocytosis assay, STING pathway analysis, T cell activity assays\",\n      \"journal\": \"Advanced science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo myeloid-specific KO with mechanistic dissection via scRNA-seq and defined pathway (NAMPT→HIF-1α→M2 polarization/efferocytosis→STING)\",\n      \"pmids\": [\"38308188\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"NAMPT/PBEF interacts with NADH dehydrogenase subunit 1 (ND1), ferritin light chain, and IFITM3 in human pulmonary vascular endothelial cells; PBEF overexpression increases these interactions and increases intracellular oxidative stress, attenuated by rotenone.\",\n      \"method\": \"Co-immunoprecipitation, overexpression, oxidative stress measurement, rotenone inhibition, interaction modeling\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP identification of interaction partners, limited functional follow-up\",\n      \"pmids\": [\"18486613\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In hen granulosa cells, recombinant NAMPT (100 ng/ml) inhibits basal and IGF1-induced progesterone secretion by reducing STAR and HSD3B protein levels and MAPK3/1 phosphorylation; these effects are abolished by the NAMPT enzymatic inhibitor FK866, establishing that enzymatic activity is required for the reproductive effect.\",\n      \"method\": \"Recombinant NAMPT treatment, FK866 inhibition, western blotting for STAR/HSD3B, MAPK phosphorylation assay, progesterone RIA\",\n      \"journal\": \"Reproduction (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — FK866 rescue establishes enzymatic activity requirement, avian model ortholog with consistent mechanism\",\n      \"pmids\": [\"25918435\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"NAMPT overexpression promotes cell survival under oxidative stress via both a SIRT1-dependent p53-CD38 pathway and a SIRT1-independent NRF2-PPARα/AMPKα pathway; NAMPT-activated NRF2 rescues mitochondrial membrane potential and content under H2O2 treatment, identifying NRF2 as a downstream target of NAMPT.\",\n      \"method\": \"NAMPT overexpression, H2O2 oxidative stress, SIRT1 inhibition, mitochondrial membrane potential assay, western blotting for NRF2/PPARα/AMPKα\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — pathway dissected with pharmacological inhibitors and overexpression, single lab\",\n      \"pmids\": [\"31816398\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"NAMPT activity regulates FOXO3a acetylation status and thereby controls GADD45A expression: increased intracellular NAD+ (via NAMPT) activates SIRT1 to deacetylate FOXO3a, reducing GADD45A transcription, while NAMPT inhibition leads to FOXO3a acetylation and GADD45A upregulation.\",\n      \"method\": \"NAMPT overexpression, FK866, SIRT1 shRNA, FOXO3a acetylation western blot, GADD45A expression analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic and pharmacological tools used to establish pathway, single lab\",\n      \"pmids\": [\"22430142\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"NAMPT deacetylation by SIRT2 activates LDHA, promoting lactate production through glycolysis in ovarian granulosa cells; FK866-mediated NAD+ synthesis inhibition increases LDHA acetylation (confirmed by Co-IP in 293T cells), reducing lactate and impairing follicular development in PCOS.\",\n      \"method\": \"Co-immunoprecipitation for LDHA acetylation, FK866 inhibition, NMN supplementation in PCOS rat model, transcriptomics, target energy metabolomics\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP validation of acetylation mechanism, in vivo PCOS model, pathway: NAMPT→NAD+→SIRT2→LDHA deacetylation→lactate\",\n      \"pmids\": [\"39489197\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NAMPT is a dimeric type II phosphoribosyltransferase that catalyzes the rate-limiting step in the NAD+ salvage pathway (nicotinamide + PRPP → NMN), thereby controlling intracellular NAD+ concentrations and regulating downstream NAD+-consuming enzymes (SIRT1, SIRT2, SIRT3, SIRT4, PARP1, CD38); intracellularly it is deacetylated and activated by SIRT6, and its expression is transcriptionally controlled by STAT1 (via the NRE1 intronic element), REV-ERB/E4BP4 (circadian regulation), and miR-146a (post-transcriptional suppression); in neurons and cardiomyocytes NAMPT is present in the mitochondrial matrix where it maintains a local NAD+ pool critical for bioenergetics; the secreted extracellular form (eNAMPT), carried in extracellular vesicles, exerts both enzymatic (NAD biosynthesis-dependent) effects on β-cell insulin secretion, vascular inflammation, and systemic aging, and enzyme-independent cytokine-like effects including macrophage polarization (via MAPK/NF-κB/STAT3) and neutrophil NADPH oxidase priming (via p40/p47 translocation and Rac activation through p38/ERK), with the latter acting through CCR5 on muscle stem cells to drive tissue regeneration.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"NAMPT is the rate-limiting enzyme in the mammalian NAD+ salvage pathway, catalyzing the conversion of nicotinamide to nicotinamide mononucleotide (NMN) as a dimeric type II phosphoribosyltransferase, thereby controlling intracellular NAD+ pools that fuel SIRT1, SIRT2, PARP1, and other NAD+-consuming enzymes critical for metabolism, DNA repair, circadian clock maintenance, and cell survival [PMID:16783373, PMID:17983582, PMID:36996103]. Intracellular NAMPT activity is essential in a tissue-specific manner: conditional deletion in forebrain neurons causes hippocampal atrophy, mitochondrial dysfunction, and cognitive deficits; haplodeficiency in pancreatic islets impairs glucose-stimulated insulin secretion; and loss in cardiomyocytes reduces mitochondrial NAD+ and ATP, exacerbating heart failure under stress [PMID:24760840, PMID:17983582, PMID:31347918]. Extracellular NAMPT (eNAMPT) functions as both an NAD+-generating enzyme and a cytokine with receptor-mediated signaling: it activates NF-κB/ERK in vascular cells through its enzymatic product NMN, polarizes monocytes toward M2 macrophages independently of enzymatic activity, primes neutrophil NADPH oxidase via p38/ERK without requiring NAD+ generation, and signals through CCR5 on muscle stem cells to drive regeneration [PMID:19727662, PMID:25368373, PMID:21518975, PMID:33568815]. NAMPT expression and activity are regulated at multiple levels—transcriptionally by STAT1 via the NRE1 enhancer and by the REV-ERB/E4BP4 circadian axis, post-transcriptionally by miR-146a targeting its 3′-UTR, and post-translationally by SIRT6- and SIRT1-mediated deacetylation that enhances its catalytic function [PMID:33976173, PMID:35036997, PMID:35241643, PMID:30514106, PMID:36797299].\",\n  \"teleology\": [\n    {\n      \"year\": 2006,\n      \"claim\": \"Determining NAMPT's catalytic mechanism was foundational: X-ray crystallography revealed a dimeric type II phosphoribosyltransferase architecture that synthesizes NMN from nicotinamide, establishing the structural basis for all subsequent enzymatic and inhibitor studies.\",\n      \"evidence\": \"Crystal structures solved with and without NMN product\",\n      \"pmids\": [\"16783373\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No co-crystal with nicotinamide substrate bound\", \"Structural basis of dimer-dependent activation not resolved\", \"No structure of eNAMPT in complex with any receptor\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Genetic evidence established NAMPT as the rate-limiting step in NAD+ salvage: Nampt haplodeficiency reduced NAD+ biosynthesis and impaired glucose-stimulated insulin secretion in islets, with rescue by the enzymatic product NMN, proving that intracellular NAMPT activity directly controls physiologically relevant NAD+ pools.\",\n      \"evidence\": \"Heterozygous knockout mice, chemical inhibition (FK866), NMN rescue, insulin secretion assays\",\n      \"pmids\": [\"17983582\", \"17268245\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Complete knockout lethality precluded full loss-of-function analysis\", \"Relative contributions of NAMPT vs. other NAD+ biosynthetic routes in different tissues not yet defined\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"The question of whether extracellular NAMPT signals through its enzymatic product or as a cytokine was first addressed: eNAMPT activated NF-κB and iNOS in vascular smooth muscle cells via NMN production, while hepatocytes were identified as a source of circulating enzymatically active dimeric eNAMPT.\",\n      \"evidence\": \"NMN supplementation phenocopied eNAMPT; APO866 blocked effects; hepatocyte conditioned media fractionation\",\n      \"pmids\": [\"19727662\", \"19912992\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor for eNAMPT on vascular cells not identified\", \"Relative contribution of hepatocyte-derived eNAMPT to circulating pool in vivo unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"NAMPT's role was extended to the CNS: neuronal-selective expression and Nampt haplodeficiency causing larger infarcts after ischemia demonstrated that neurons depend on NAMPT-mediated NAD+ for survival under stress.\",\n      \"evidence\": \"Immunostaining of mouse brain, heterozygous KO, photothrombosis stroke model\",\n      \"pmids\": [\"20485294\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cell-autonomous versus non-cell-autonomous neuroprotection not separated\", \"Downstream NAD+-consuming enzymes mediating protection not identified\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"A key mechanistic distinction was drawn: eNAMPT primed neutrophil NADPH oxidase by inducing p40phox/p47phox membrane translocation and Rac activation via p38/ERK, and this was independent of NAD+ generation—demonstrating a bona fide non-enzymatic cytokine function of eNAMPT.\",\n      \"evidence\": \"ROS assay, membrane fractionation, APO866 showing NAD-independent priming\",\n      \"pmids\": [\"21518975\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor mediating neutrophil priming not identified\", \"Whether enzymatic-independent signaling uses same receptor as enzymatic-dependent signaling unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Conditional genetics revealed tissue-specific essentiality: forebrain neuron-specific Nampt knockout caused hippocampal atrophy, abnormal dendrites, and memory impairment, while eNAMPT was shown to polarize monocytes to M2 macrophages in CLL independently of enzymatic activity using an inactive mutant.\",\n      \"evidence\": \"CaMKIIα-Cre conditional KO mice with behavioral/histological phenotyping; enzymatically inactive NAMPT mutant in co-culture\",\n      \"pmids\": [\"24760840\", \"25368373\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor for non-enzymatic macrophage polarization not identified at this point\", \"Whether neuronal phenotype is purely NAD+-dependent or involves eNAMPT signaling unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Post-translational regulation of NAMPT was established: SIRT6 directly deacetylates NAMPT protein to enhance its enzymatic activity and increase NAD(P)H levels, creating a feedforward loop between NAD+-dependent sirtuins and NAD+ synthesis.\",\n      \"evidence\": \"In vitro deacetylation of immunopurified NAMPT by recombinant SIRT6, cellular overexpression/silencing\",\n      \"pmids\": [\"30514106\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific acetylation sites on NAMPT mediating activation not mapped\", \"Whether SIRT6 regulation of NAMPT occurs in all tissues unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Multiple studies expanded NAMPT's physiological roles: NAMPT was localized to the neuronal mitochondrial matrix with an intact salvage pathway; cardiac-specific gain- and loss-of-function showed that both too little and too much NAMPT are detrimental to the heart; and hypothalamic NAMPT was shown to be required for fasting-induced food intake.\",\n      \"evidence\": \"Subcellular fractionation of neuronal mitochondria; cardiac Nampt transgenic/heterozygous KO mice under pressure overload; ICV FK866 administration abolishing feeding behavior\",\n      \"pmids\": [\"31553812\", \"31347918\", \"31900990\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How mitochondrial NAMPT is imported (no signal peptide identified) remains unclear\", \"Dose-response relationship for optimal cardiac NAMPT levels not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Transcriptional control and extracellular signaling mechanisms were resolved: STAT1 directly activates NAMPT via intronic NRE1 in macrophages to support inflammatory gene expression; the REV-ERB/E4BP4 axis controls circadian Nampt expression in cardiomyocytes; and macrophage-secreted eNAMPT was identified as signaling through CCR5 on muscle stem cells to drive regeneration.\",\n      \"evidence\": \"ChIP-seq for STAT1 at NRE1 plus NRE1-disruption mice with tumor phenotype; cardiomyocyte Rev-erb DKO with ChIP for E4BP4; zebrafish live imaging with CCR5 pathway analysis\",\n      \"pmids\": [\"33976173\", \"35036997\", \"33568815\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CCR5 is the sole receptor for eNAMPT or one of multiple receptors not settled\", \"How NAMPT is secreted (no signal peptide; unconventional secretion mechanism unknown)\", \"Integration between circadian and inflammatory transcriptional control of NAMPT unexplored\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Additional regulatory layers were identified: SIRT1 directly deacetylates NAMPT to enhance its activity (paralleling SIRT6 regulation); miR-146a was shown to directly target the Nampt 3′-UTR downstream of NF-κB; lamin A/C controls chromatin accessibility at the Nampt promoter; and hippocampal Nampt deletion caused mitochondrial swelling, Aβ aggregation, and cognitive deficits.\",\n      \"evidence\": \"SIRT1 binding/deacetylation assays; 3′-UTR reporter for miR-146a; ATAC-seq in Lmna-/- MEFs; CA1-specific Nampt conditional KO with EM\",\n      \"pmids\": [\"36797299\", \"35241643\", \"36099415\", \"36441480\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether SIRT1 and SIRT6 deacetylate the same or different NAMPT lysines unknown\", \"Chromatin-level regulation by lamin A/C not tested beyond MEFs and HGPS fibroblasts\", \"Causal relationship between NAMPT loss and Aβ aggregation versus parallel consequences of NAD+ depletion not resolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Tissue-specificity of NAMPT-clock coupling was defined: brown adipose tissue requires NAMPT to sustain circadian clock amplitude and TCA cycle rhythmicity, while skeletal muscle clock is refractory to NAMPT loss, revealing that NAD+ control of the clock is not universal.\",\n      \"evidence\": \"Multiple tissue-specific Nampt conditional knockouts with circadian gene expression and metabolomics\",\n      \"pmids\": [\"36996103\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis for tissue-specific clock sensitivity to NAD+ unknown\", \"Whether eNAMPT compensates for iNAMPT loss in refractory tissues not tested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Myeloid-specific Nampt deletion revealed that NAMPT stabilizes HIF-1α to promote M2 tumor-associated macrophage polarization and efferocytosis; its loss activates STING/type I IFN signaling and enhances anti-tumor T cell responses, identifying NAMPT as a macrophage-intrinsic immunosuppressive factor.\",\n      \"evidence\": \"Myeloid-specific conditional KO in CRC tumor model, scRNA-seq, flow cytometry, STING pathway analysis\",\n      \"pmids\": [\"38308188\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether HIF-1α stabilization is directly NAD+-dependent or involves intermediate metabolites not defined\", \"Therapeutic window for macrophage NAMPT inhibition in cancer not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The mechanism by which NAMPT is secreted extracellularly (lacking a signal peptide) and the identity/hierarchy of eNAMPT receptors across different cell types remain unresolved; it is also unknown how NAMPT's enzymatic and non-enzymatic cytokine functions are coordinately regulated in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Secretion mechanism for eNAMPT completely undefined\", \"Full receptor repertoire (beyond CCR5) not mapped\", \"In vivo contribution of enzymatic vs. non-enzymatic eNAMPT signaling not separable with current tools\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0, 1, 2, 3]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [6, 9, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 15]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [15]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [3, 4, 6, 9, 17]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 1, 2, 13, 27]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [6, 16, 25]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 9, 17]},\n      {\"term_id\": \"R-HSA-9909396\", \"supporting_discovery_ids\": [19, 27]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [18, 24]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"SIRT1\",\n      \"SIRT6\",\n      \"SIRT2\",\n      \"CCR5\",\n      \"PARP1\",\n      \"STAT1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"NAMPT is the rate-limiting enzyme of the mammalian NAD+ salvage pathway, catalyzing the condensation of nicotinamide with 5-phosphoribosyl-1-pyrophosphate to yield nicotinamide mononucleotide (NMN), and thereby governing intracellular NAD+ pools that fuel sirtuins (SIRT1–4), PARP1, and CD38 [PMID:12555668, PMID:17889652, PMID:16783373]. Intracellular NAMPT localizes to both the cytosol and the mitochondrial matrix of neurons and cardiomyocytes, where it sustains compartment-specific NAD+ levels critical for bioenergetics, neuronal survival, and circadian clock amplitude [PMID:31553812, PMID:36441480, PMID:36996103]; its activity is post-translationally enhanced by SIRT6- and SIRT1-mediated deacetylation and transcriptionally regulated by STAT1, REV-ERBα/β–E4BP4, lamin A/C-dependent chromatin accessibility, and miR-146a [PMID:30514106, PMID:36797299, PMID:33976173, PMID:35036997, PMID:35241643, PMID:36099415]. The secreted extracellular form (eNAMPT), released in extracellular vesicles, exerts both enzymatic effects—supporting β-cell insulin secretion and vascular NAD+ supply during aging—and enzyme-independent cytokine-like functions including monocyte activation via NF-κB/MAPK/STAT3 signaling, neutrophil NADPH oxidase priming through p38/ERK-dependent p40/p47 translocation and Rac activation, M2 macrophage polarization, and CCR5-dependent muscle stem cell proliferation during tissue regeneration [PMID:17983582, PMID:31204283, PMID:17237424, PMID:21518975, PMID:25368373, PMID:33568815]. In macrophages, NAMPT stabilizes HIF-1α to promote M2 tumor-associated macrophage polarization and efferocytosis, while its loss enhances STING-mediated type I interferon signaling and anti-tumor immunity [PMID:38308188].\",\n  \"teleology\": [\n    {\n      \"year\": 1994,\n      \"claim\": \"The gene was first identified as a secreted cytokine (PBEF) that synergizes with SCF and IL-7 to promote pre-B-cell colony formation, establishing its extracellular signaling role before its enzymatic function was known.\",\n      \"evidence\": \"cDNA library cloning from human peripheral blood lymphocytes with in vitro B-cell colony assay\",\n      \"pmids\": [\"8289818\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor for the cytokine activity was not identified\", \"Mechanism of synergy with SCF/IL-7 undefined\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Reconstitution of NAMPT enzymatic activity—conversion of nicotinamide + PRPP to NMN—reframed PBEF as the rate-limiting NAD+ salvage enzyme, fundamentally changing the understanding of its biology from pure cytokine to metabolic enzyme.\",\n      \"evidence\": \"Direct enzymatic activity assay and bacterial complementation of NAmPRTase-defective strain\",\n      \"pmids\": [\"12555668\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How cytokine activity relates to enzymatic activity was unresolved\", \"Structural basis of catalysis unknown at this point\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Discovery that NAMPT inhibits neutrophil apoptosis in response to inflammatory stimuli demonstrated a pro-survival role in innate immune cells distinct from its B-cell effects.\",\n      \"evidence\": \"Antisense oligonucleotide knockdown and recombinant protein treatment with caspase activity assays in human neutrophils\",\n      \"pmids\": [\"15124023\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether this anti-apoptotic effect is enzymatic or cytokine-mediated was not resolved\", \"Receptor and signaling pathway not identified\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"The crystal structure revealed NAMPT as a dimeric type II phosphoribosyltransferase, providing the structural framework for understanding catalysis and enabling rational inhibitor design.\",\n      \"evidence\": \"X-ray crystallography with and without NMN product bound\",\n      \"pmids\": [\"16783373\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of the cytokine-like (enzyme-independent) activity remained unexplained\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"A series of studies established the NAMPT→NAD+→sirtuin axis as a central signaling conduit: NAMPT controls mitochondrial NAD+ and cell survival via SIRT3/SIRT4 under fasting, extends vascular smooth muscle cell lifespan via SIRT1-mediated p53 deacetylation, and eNAMPT regulates pancreatic β-cell insulin secretion through its enzymatic product NMN.\",\n      \"evidence\": \"Nampt+/− mice with NMN rescue for insulin secretion; fasting/fractionation/siRNA for mitochondrial sirtuins; dominant-negative SIRT1 epistasis for vascular senescence\",\n      \"pmids\": [\"17983582\", \"17889652\", \"17307730\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether eNAMPT has a dedicated receptor was unresolved\", \"Tissue-specific differences in NAMPT dependence not yet mapped\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Extracellular NAMPT was shown to activate monocytes and induce pro-inflammatory cytokines through p38/MEK1/NF-κB, establishing it as a dual-function molecule with both enzymatic and cytokine-like activities.\",\n      \"evidence\": \"Recombinant eNAMPT treatment of CD14+ monocytes with MAPK inhibitors and NF-κB activation assays\",\n      \"pmids\": [\"17237424\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether this monocyte activation requires enzymatic activity was not dissected here\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Vascular inflammation by eNAMPT was shown to require its enzymatic activity (NMN mimics the effect, APO866 blocks it), while separately, constitutive hepatocyte secretion of dimeric eNAMPT was documented, indicating continuous systemic release.\",\n      \"evidence\": \"ERK/NF-κB signaling in vascular smooth muscle cells with NMN/APO866; size exclusion chromatography and activity assay on secreted hepatocyte NAMPT\",\n      \"pmids\": [\"19727662\", \"19912992\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mode of secretion (classical vs. non-classical) not determined\", \"Relative contribution of different tissues to circulating eNAMPT unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Neutrophil NADPH oxidase priming by eNAMPT was definitively shown to be enzyme-independent—NMN and NAD cannot mimic it and APO866 cannot block it—acting instead through p38/ERK to translocate p40/p47 subunits and activate Rac, establishing a clear bifunctional paradigm for extracellular NAMPT.\",\n      \"evidence\": \"Membrane fractionation, Rac activation assay, MAPK inhibitors, and APO866 in human neutrophils\",\n      \"pmids\": [\"21518975\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The receptor mediating enzyme-independent signaling in neutrophils was not identified\", \"Structural determinants on NAMPT that mediate cytokine-like activity unknown\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Two landmark studies addressed tissue-autonomous requirements: eNAMPT promoted M2 macrophage polarization via ERK1/2/STAT3/NF-κB independently of enzymatic activity (proven by enzymatic mutant), while neuron-specific NAMPT deletion caused hippocampal atrophy, gliosis, and memory deficits, demonstrating non-redundant intracellular NAD+ dependency in excitatory neurons.\",\n      \"evidence\": \"Enzymatically inactive NAMPT mutant in CLL-derived macrophage polarization assay; CaMKIIα-Cre Nampt conditional knockout with histology, electrophysiology, and behavioral testing\",\n      \"pmids\": [\"25368373\", \"24760840\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor for enzyme-independent macrophage polarization not identified\", \"Whether neuronal NAMPT loss phenotype is reversible with NMN supplementation untested in this study\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"SIRT6 was identified as a direct deacetylase of NAMPT, establishing a positive feedback loop where sirtuin activity enhances NAD+ biosynthesis by activating NAMPT.\",\n      \"evidence\": \"In vitro reconstitution of SIRT6-mediated NAMPT deacetylation with immunopurified NAMPT and recombinant SIRT6, validated by NAD(H) measurements in cancer cells\",\n      \"pmids\": [\"30514106\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific acetylation sites on NAMPT targeted by SIRT6 not mapped\", \"Whether this loop operates in non-cancer contexts was unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Multiple studies refined compartment-specific roles: NAMPT resides in the neuronal mitochondrial matrix maintaining a local NAD+ salvage pathway; eNAMPT circulates in extracellular vesicles and its supplementation from young to old mice extends lifespan; and balanced NAMPT dosage is critical in the heart where both gain and loss of function worsen heart failure.\",\n      \"evidence\": \"Subcellular fractionation and NMNAT knockdown in neurons; EV isolation with NAD+ assays and lifespan studies in mice; Nampt+/− and cardiac-specific transgenic mice under pressure overload\",\n      \"pmids\": [\"31553812\", \"31204283\", \"31347918\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of NAMPT import into mitochondria unknown (lacks canonical MTS)\", \"Cargo-sorting mechanism for eNAMPT into EVs uncharacterized\", \"Therapeutic window for NAMPT modulation in cardiac disease undefined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Transcriptional and receptor-level regulation was resolved: STAT1 drives NAMPT expression via the intronic NRE1 element in macrophages supporting anti-tumor glycolysis; REV-ERBα/β–E4BP4 controls circadian NAMPT expression in cardiomyocytes; and macrophage-derived eNAMPT acts through CCR5 on muscle stem cells to drive regeneration.\",\n      \"evidence\": \"STAT1 ChIP at NRE1 with myeloid-specific NRE1 KO and melanoma model; cardiomyocyte-specific Rev-erb DKO with ChIP; zebrafish NAMPT/CCR5 genetic perturbation with live imaging\",\n      \"pmids\": [\"33976173\", \"35036997\", \"33568815\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CCR5 is the receptor for enzyme-independent eNAMPT signaling in mammals not confirmed\", \"How NRE1-dependent NAMPT expression differs between macrophage subtypes not fully explored\", \"Whether E4BP4 directly binds Nampt regulatory elements or acts indirectly needs clarification\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"NAMPT-supplied NAD+ was linked to parthanatos: in psoriasis models, NAMPT fuels PARP1 hyperactivation and AIFM1 nuclear translocation, causing keratinocyte death and inflammation—demonstrating pathological consequences of excessive NAD+ availability.\",\n      \"evidence\": \"Zebrafish and human 3D skin models with genetic/pharmacological NAMPT inhibition, PARP activity measurement, AIFM1 localization\",\n      \"pmids\": [\"34748530\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether NAMPT inhibition is therapeutically viable in human psoriasis untested\", \"Relative contribution of PARP1 vs. other NAD+ consumers in this context unclear\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Post-transcriptional and epigenetic control of NAMPT was elucidated: miR-146a directly suppresses NAMPT via 3′-UTR targeting within a mutual inhibitory loop with AMPK/NF-κB; and lamin A/C deficiency reduces NAMPT promoter chromatin accessibility, depleting NAD+ and impairing mitochondrial function in progeria.\",\n      \"evidence\": \"3′-UTR luciferase assay with miR-146a and AMPK activators in vitro/in vivo; ATAC-seq of Lmna−/− MEFs and HGPS fibroblasts with NAD+/SIRT1/bioenergetics readouts\",\n      \"pmids\": [\"35241643\", \"36099415\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether chromatin accessibility changes at NAMPT are a cause or consequence of NAD+ depletion in progeria needs further dissection\", \"Therapeutic potential of miR-146a inhibition for NAD+ restoration unexplored\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"SIRT1 was identified as a second sirtuin that directly deacetylates and activates NAMPT (complementing SIRT6), and tissue-specific circadian clock dependence on NAMPT was mapped—essential in brown adipose tissue, moderate in white adipose, absent in skeletal muscle.\",\n      \"evidence\": \"SIRT1-NAMPT Co-IP with deacetylation assay and nicotine-treated aging mice; adipose-specific Nampt KO with clock gene expression and metabolomics\",\n      \"pmids\": [\"36797299\", \"36996103\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Acetylation site specificity for SIRT1 vs. SIRT6 on NAMPT not compared\", \"Basis for tissue-specific clock dependence on NAMPT unclear\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Macrophage-intrinsic NAMPT was shown to stabilize HIF-1α for M2 TAM polarization and efferocytosis, while its absence activates STING/type I IFN signaling to enhance anti-tumor immunity—defining NAMPT as a myeloid immune checkpoint; separately, NAMPT→NAD+→SIRT2-mediated LDHA deacetylation was linked to lactate production and follicular development in PCOS.\",\n      \"evidence\": \"Myeloid-specific Nampt KO with scRNA-seq of tumor microenvironment and STING pathway analysis; Co-IP of LDHA acetylation with FK866/NMN in PCOS rat model\",\n      \"pmids\": [\"38308188\", \"39489197\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether NAMPT-targeted myeloid therapy synergizes with immune checkpoint inhibitors in patients is untested\", \"SIRT2-LDHA-lactate axis in PCOS based on single study with Co-IP, awaits independent validation\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of eNAMPT's enzyme-independent cytokine-like activity, the mechanism of NAMPT translocation into the mitochondrial matrix, the full receptor repertoire for eNAMPT signaling across tissues (only CCR5 identified in zebrafish muscle stem cells), and whether therapeutic NAMPT modulation can achieve tissue-selective NAD+ control without pathological consequences.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Structural determinants for cytokine vs. enzyme activity on the NAMPT dimer uncharacterized\", \"Mitochondrial import mechanism unknown\", \"Mammalian receptor for enzyme-independent eNAMPT signaling not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [1, 2, 3, 8]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 6, 12, 18]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [7, 11, 27]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [4, 17, 24]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [17]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 3, 9, 15]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [15]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [23]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 2, 3, 4, 8, 17, 26, 32]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [5, 6, 10, 12, 21, 27]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [6, 8, 12, 18, 22]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [5, 20]},\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [22]},\n      {\"term_id\": \"R-HSA-9909396\", \"supporting_discovery_ids\": [19, 26]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [14, 23, 30]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"SIRT1\",\n      \"SIRT6\",\n      \"SIRT2\",\n      \"SIRT3\",\n      \"PARP1\",\n      \"CCR5\",\n      \"STAT1\",\n      \"HIF1A\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}