{"gene":"NGB","run_date":"2026-04-29T11:37:56","timeline":{"discoveries":[{"year":2000,"finding":"Neuroglobin (NGB) was identified as a third vertebrate globin type, predominantly expressed in the brain, functioning as a monomeric oxygen-binding protein with high O2 affinity (P50 ~2 torr), analogous to myoglobin in potentially increasing O2 availability to brain tissue.","method":"cDNA cloning, recombinant protein expression, O2 affinity measurement","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — original discovery paper with recombinant protein biochemistry, highly cited foundational study","pmids":["11029004"],"is_preprint":false},{"year":2001,"finding":"Human and mouse recombinant NGB display a hexacoordinated deoxy ferrous heme (His-Fe2+-His), where the distal histidine (E7-His) acts as the endogenous ligand; O2 and CO can displace this endogenous ligand. NGB has high autoxidation rate, and mouse NGB exists as a monomer with disulfide-dependent dimer formation.","method":"Spectral measurements, flash photolysis, site-directed mutagenesis, recombinant protein biochemistry","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — recombinant protein reconstitution with mutagenesis and multiple spectroscopic methods, foundational mechanistic study","pmids":["11473128"],"is_preprint":false},{"year":2002,"finding":"Neuroglobin expression in neural cells is induced by hemin via a cGMP/protein kinase G pathway (not the MAPK pathway used by hypoxia), demonstrating two distinct signal transduction pathways regulate NGB expression.","method":"RT-PCR, Western blot, pharmacological inhibitors (KT5823, LY83583, PD98059), cGMP measurement","journal":"Blood","confidence":"Medium","confidence_rationale":"Tier 2 — multiple inhibitors used in cell-based assays with mechanistic follow-up, single lab","pmids":["12239161"],"is_preprint":false},{"year":2002,"finding":"Full-length human NGB cDNA was cloned; NGB protein immunoreactive signals were localized to the cytoplasm and processes of neurons, distributed throughout rat brain regions including cerebral cortex, hippocampus, thalamus, hypothalamus, pons, and cerebellum.","method":"RACE cloning, in situ hybridization, immunohistochemistry","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — direct protein localization by immunohistochemistry with validated antibody","pmids":["11820779"],"is_preprint":false},{"year":2003,"finding":"X-ray crystal structure of human brain NGB revealed a classical globin fold with hexacoordinated heme, an elongated protein matrix cavity that facilitates O2 diffusion, and structural adaptations to host the reversible bis-histidyl heme complex.","method":"X-ray crystallography","journal":"Structure (London, England : 1993)","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional interpretation","pmids":["12962627"],"is_preprint":false},{"year":2003,"finding":"Oxidized (ferric) NGB binds exclusively to the GDP-bound form of Gαi heterotrimeric G protein subunit, acting as a guanine nucleotide dissociation inhibitor (GDI) that inhibits GDP-to-GTP exchange, thereby liberating Gβγ and promoting neuronal survival. Ferrous ligand-bound NGB under normoxia lacks GDI activity.","method":"Surface plasmon resonance, GDP dissociation assays, GTPγS binding assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro biochemical reconstitution with multiple functional assays, redox-state specificity demonstrated","pmids":["12860983"],"is_preprint":false},{"year":2003,"finding":"His64 is the endogenous distal heme ligand in NGB and Lys67 is situated nearby in the distal pocket; His96 is the proximal ligand (its mutation causes complete loss of heme). CO binding kinetics are biphasic due to His64 and Lys67 in the distal pocket.","method":"Site-directed mutagenesis, resonance Raman spectroscopy, flash photolysis","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis combined with spectroscopic methods, multiple mutants characterized","pmids":["14645216"],"is_preprint":false},{"year":2003,"finding":"NGB protein is widely expressed in neurons of the mouse brain including cerebral cortex, subcortical structures, brainstem nuclei, and cerebellum, with regionally differing expression levels consistent with variation in hypoxic tolerance.","method":"Immunohistochemistry with affinity-purified polyclonal antibody","journal":"Neuroscience letters","confidence":"Medium","confidence_rationale":"Tier 2 — direct protein localization with validated antibody","pmids":["12850561"],"is_preprint":false},{"year":2003,"finding":"Formation of an intramolecular disulfide bond between Cys46 (CD7) and Cys55 (D5) in human NGB increases O2 affinity by approximately 10-fold by slowing histidine dissociation rate; breaking the S-S bond (by reduction or mutagenesis) decreases O2 affinity. This links the redox state of the cell to NGB's O2 binding affinity.","method":"Mass spectrometry, thiol accessibility studies, site-directed mutagenesis, O2 binding assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal methods including mutagenesis, MS, and ligand binding assays","pmids":["14530264"],"is_preprint":false},{"year":2004,"finding":"Human NGB interacts with flotillin-1, a lipid raft microdomain-associated protein, identified by yeast two-hybrid screening of a human brain cDNA library and confirmed by GST pull-down; flotillin-1 may recruit NGB to lipid rafts as part of neuroprotective signaling.","method":"Yeast two-hybrid, GST pull-down","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 3 — yeast two-hybrid plus GST pull-down, single lab, no functional follow-up in neurons","pmids":["15120622"],"is_preprint":false},{"year":2004,"finding":"NGB shows alkaline and acid Bohr effects (pH-dependent O2 affinity) and temperature-dependent enthalpy of oxygenation. His(E7) stabilizes bound O2 and functions as a major Bohr group in the presence of Lys(E10), as shown by mutant analysis.","method":"O2 equilibrium binding with recombinant mutant proteins, thiol titration, mass spectrometry","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — recombinant mutant proteins with multiple ligand binding assays","pmids":["15299006"],"is_preprint":false},{"year":2005,"finding":"Spectroscopic characterization confirmed His64 as the distal ligand and His96 as the proximal ligand in NGB; the CO adduct of NGB contains three conformers, with His64 contributing to conformer interconversion. Fe-His stretching frequency of the photolyzed 5-coordinate NGB is 221 cm−1.","method":"Picosecond time-resolved resonance Raman spectroscopy, FT-IR, distal mutant analysis","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 — multiple spectroscopic methods with mutagenesis","pmids":["16201751"],"is_preprint":false},{"year":2007,"finding":"MetNGB (ferric NGB) reacts with nitrite (NO2−) and H2O2 to generate an active species with peroxynitrite-like properties that nitrates phenolic substrates; the disulfide bond (Cys46-Cys55) affects this reactivity. NGB can also be self-modified at endogenous Tyr (to 3-nitrotyrosine) and Cys (to sulfinic/sulfonic acid) residues.","method":"Kinetic assays, nitrite-binding studies, HPLC-MS/MS analysis of modified residues","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro biochemical assays with MS/MS characterization of modifications","pmids":["17600531"],"is_preprint":false},{"year":2008,"finding":"Molecular dynamics simulations showed that protein oxidation (disulfide bond formation between CysCD7 and CysD5) promotes stabilization of the pentacoordinated (5c) heme species, favoring the more reactive state and supporting an O2 storage/sensor function whereby O2 would be released under hypoxic/oxidizing conditions.","method":"Molecular dynamics simulation, free energy calculations","journal":"Proteins","confidence":"Low","confidence_rationale":"Tier 4 — computational prediction only, no experimental validation in this paper","pmids":["17975837"],"is_preprint":false},{"year":2010,"finding":"NGB inhibits the intrinsic apoptosis pathway by interacting with cytochrome c, thereby blocking apoptosome formation and pro-caspase 9 activation. NGB protection is concentration-sensitive and involves both binding to cytochrome c and subsequent redox reaction.","method":"Cell biology and biochemical apoptosis assays, computational modeling of apoptotic signaling","journal":"Apoptosis : an international journal on programmed cell death","confidence":"Medium","confidence_rationale":"Tier 2 — direct binding to cytochrome c demonstrated with functional inhibition of caspase 9, single lab","pmids":["20091232"],"is_preprint":false},{"year":2010,"finding":"Transgenic NGB-overexpressing mice show markedly reduced ROS/RNS production, lipid peroxidation, and CA1 neuronal injury after hippocampal ischemia-reperfusion, demonstrating NGB's antioxidant protective role in vivo.","method":"Transgenic mouse model, bilateral carotid occlusion, cresyl violet staining, malonyldialdehyde assay, ROS/RNS staining","journal":"Journal of cerebral blood flow and metabolism","confidence":"Medium","confidence_rationale":"Tier 2 — transgenic in vivo model with multiple readouts, single lab","pmids":["20571522"],"is_preprint":false},{"year":2011,"finding":"Deoxygenated human NGB functions as a redox-regulated nitrite reductase, converting nitrite to NO. This activity is regulated by surface thiols Cys55 and Cys46 that modulate six-to-five heme coordination. Distal His-to-Leu/Gln mutants reduce nitrite ~2000-fold faster. In cells, NGB nitrite reductase activity inhibits cellular respiration via NO binding to cytochrome c oxidase, confirming a role in intracellular hypoxic NO-signaling.","method":"In vitro nitrite reduction assays, site-directed mutagenesis, lentiviral cell expression, respiration measurements","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with mutagenesis plus cellular validation with multiple orthogonal approaches","pmids":["21296891"],"is_preprint":false},{"year":2011,"finding":"NGB is phosphorylated during hypoxia and glucose deprivation, and this phosphorylation promotes interaction with 14-3-3 proteins; 14-3-3 binding stabilizes NGB phosphorylation and increases the open probability of the heme pocket (5-coordinate fraction), accelerating nitrite reduction to NO. This reveals a hypoxia-dependent post-translational modification cascade regulating NGB's heme reactivity.","method":"Co-immunoprecipitation, phosphorylation assays, CO/nitrite binding kinetics, SH-SY5Y cell hypoxia experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP plus functional ligand binding studies in both in vitro and cellular settings","pmids":["21965683"],"is_preprint":false},{"year":2013,"finding":"NGB promotes cell survival via the Akt phosphorylation/CREB signaling pathway; in an Alzheimer's disease rat model, IBU-LA treatment maintained high Ngb levels, which correlated with restored p-Akt/Akt and p-CREB/CREB ratios and reduced cytochrome C/Apaf1 complex formation, implicating NGB in activation of the Akt/CREB pro-survival axis.","method":"Western blot, co-immunoprecipitation (cytochrome C/Apaf1), TUNEL, immunohistochemistry","journal":"Gerontology","confidence":"Low","confidence_rationale":"Tier 3 — correlative Western blot data in rat model, indirect evidence for NGB-Akt link","pmids":["23428737"],"is_preprint":false},{"year":2013,"finding":"Exogenous TAT PTD-Ngb fusion protein transduces into primary cortical neurons and protects against hypoxia-induced apoptosis by increasing Bcl-2 expression and decreasing caspase-3 and caspase-9 activity, indicating NGB suppresses the mitochondrial apoptotic pathway.","method":"Fluorescent immunostaining, MTT assay, TEM, Western blot for Bcl-2/caspase-3/caspase-9","journal":"Neurological sciences","confidence":"Medium","confidence_rationale":"Tier 2 — cell-based loss/gain of function with multiple molecular readouts of apoptotic pathway","pmids":["23456442"],"is_preprint":false},{"year":2014,"finding":"The wild-type human neuroglobin crystal structure at 1.74 Å resolution revealed two distinct conformations of the CD region containing the Cys46-Cys55 intramolecular disulfide link, and identified internal cavities involved in ligand migration and conformational transitions between low and high O2-affinity states.","method":"X-ray crystallography","journal":"Acta crystallographica. Section D, Biological crystallography","confidence":"High","confidence_rationale":"Tier 1 — high-resolution crystal structure with direct observation of disulfide bond conformational flexibility","pmids":["24699645"],"is_preprint":false},{"year":2019,"finding":"Mn-TAT PTD-Ngb, a manganese porphyrin reconstituted NGB fusion protein, has enhanced ROS scavenging ability compared to TAT PTD-Ngb, reduces intracellular ROS, restores mitochondrial function, inhibits mitochondria-dependent apoptosis, and activates the PI3K/Akt/Nrf2/HO-1 redox signaling pathway.","method":"ROS assays, mitochondrial function assays, Western blot for PI3K/Akt/Nrf2/HO-1, cell viability assays","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — multiple biochemical readouts in cell-based system, engineered protein variant","pmids":["31882813"],"is_preprint":false},{"year":2021,"finding":"NGB transcription is activated by CREB, which directly binds the NGB promoter. Polydatin activates AKT/CREB signaling to upregulate NGB expression, and NGB knockdown abolishes polydatin's neuroprotective effect against H2O2, placing NGB downstream of CREB in a neuroprotective signaling cascade.","method":"Luciferase reporter assay, ChIP assay, siRNA knockdown, Western blot, cell viability assay","journal":"Molecular medicine reports","confidence":"Medium","confidence_rationale":"Tier 2 — direct ChIP and reporter assay demonstrating CREB-NGB promoter binding, with functional KD validation","pmids":["34751416"],"is_preprint":false}],"current_model":"NGB (neuroglobin) is a brain-enriched hexacoordinated globin whose heme iron cycles between six-coordinate (His64-Fe-His96 bis-histidyl) and five-coordinate states; O2/CO binding affinity is regulated by a redox-sensitive intramolecular Cys46-Cys55 disulfide bond and by hypoxia-induced phosphorylation and 14-3-3 interaction; in its oxidized (ferric) state NGB acts as a GDI for Gαi to liberate Gβγ and promote survival signaling, binds cytochrome c to block apoptosome/caspase-9 activation, and in its deoxygenated state functions as a nitrite reductase generating NO to modulate cellular respiration, collectively defining NGB as a redox- and hypoxia-responsive sensor that couples oxygen status to neuroprotective signaling pathways including PI3K/Akt/CREB/Nrf2."},"narrative":{"teleology":[{"year":2000,"claim":"Identification of NGB as a novel vertebrate globin with high O₂ affinity predominantly expressed in the brain established that neurons possess a dedicated oxygen-binding protein distinct from hemoglobin and myoglobin.","evidence":"cDNA cloning, recombinant protein expression, O₂ equilibrium measurements showing P50 ~2 torr","pmids":["11029004"],"confidence":"High","gaps":["Physiological function beyond O₂ supply was unknown","Subcellular localization not resolved","Regulation of expression not characterized"]},{"year":2001,"claim":"The demonstration that deoxy-NGB adopts a hexacoordinated bis-histidyl heme (His-Fe²⁺-His) explained why exogenous ligands must compete with an internal ligand, fundamentally distinguishing NGB's ligand-binding mechanism from classical pentacoordinate globins.","evidence":"Absorption spectroscopy, flash photolysis, and site-directed mutagenesis of recombinant human and mouse NGB","pmids":["11473128"],"confidence":"High","gaps":["Identity of distal and proximal histidines not yet confirmed by mutagenesis","Functional consequence of hexacoordination in cells unknown"]},{"year":2003,"claim":"Crystal structures and systematic mutagenesis identified His64 as the distal ligand and His96 as the proximal ligand, revealed the globin fold with an elongated internal cavity system for ligand migration, and showed that the Cys46–Cys55 disulfide bond increases O₂ affinity ~10-fold by modulating histidine dissociation rate — directly linking cellular redox state to NGB's gas-binding properties.","evidence":"X-ray crystallography, resonance Raman spectroscopy, site-directed mutagenesis, mass spectrometry, and O₂ binding assays","pmids":["12962627","14645216","14530264"],"confidence":"High","gaps":["Whether disulfide-dependent affinity shift operates under physiological redox conditions in neurons","Structural basis for transition between 6c and 5c states not fully resolved"]},{"year":2003,"claim":"The discovery that ferric NGB acts as a GDI for Gαi — binding exclusively to GDP-Gαi, blocking nucleotide exchange, and liberating Gβγ — established a non-canonical signaling function for a globin and linked NGB's oxidation state to G-protein-coupled neuroprotective signaling.","evidence":"Surface plasmon resonance, GDP dissociation and GTPγS binding assays with purified proteins","pmids":["12860983"],"confidence":"High","gaps":["In vivo confirmation of NGB-Gαi interaction in neurons","Which downstream effectors of Gβγ mediate the survival signal","Whether GDI activity occurs at endogenous NGB concentrations"]},{"year":2010,"claim":"Demonstration that NGB binds cytochrome c to block apoptosome assembly and caspase-9 activation, and that NGB overexpression reduces ROS/RNS and neuronal death after ischemia in vivo, established NGB as an anti-apoptotic factor operating at the mitochondrial pathway.","evidence":"Cytochrome c binding and caspase inhibition assays; NGB-overexpressing transgenic mice subjected to bilateral carotid occlusion with ROS, lipid peroxidation, and histological readouts","pmids":["20091232","20571522"],"confidence":"Medium","gaps":["Stoichiometry and affinity of NGB–cytochrome c interaction in the cytosol","Whether NGB directly reduces cytochrome c or blocks its interaction with Apaf-1","Contribution relative to other anti-apoptotic proteins"]},{"year":2011,"claim":"Establishing that deoxygenated NGB is a nitrite reductase generating NO — regulated by the Cys46/Cys55 disulfide and by hypoxia-induced phosphorylation and 14-3-3 binding that stabilize the 5-coordinate state — revealed a post-translational modification cascade that tunes NGB's enzymatic activity to inhibit mitochondrial respiration under hypoxia.","evidence":"In vitro nitrite reduction kinetics with WT and mutant NGB; lentiviral expression in cells with respirometry; co-IP of phospho-NGB with 14-3-3 under hypoxia in SH-SY5Y cells","pmids":["21296891","21965683"],"confidence":"High","gaps":["Identity of the kinase(s) phosphorylating NGB","Quantitative contribution of NGB-derived NO relative to NOS-derived NO in hypoxic neurons","Whether 14-3-3 isoform selectivity exists"]},{"year":2014,"claim":"A high-resolution (1.74 Å) crystal structure of wild-type NGB captured two conformations of the CD loop harboring the Cys46–Cys55 disulfide, providing a structural basis for the redox-sensitive transition between high- and low-affinity O₂ binding states.","evidence":"X-ray crystallography at 1.74 Å resolution","pmids":["24699645"],"confidence":"High","gaps":["No structure of the reduced (dithiol) form for direct comparison","Dynamics of conformational switching in solution remain uncharacterized"]},{"year":2021,"claim":"Showing that CREB directly binds the NGB promoter and that NGB knockdown abolishes Akt/CREB-mediated neuroprotection closed a positive feedback loop: NGB activates Akt/CREB signaling, and CREB in turn drives NGB transcription, placing NGB as both effector and target of a self-reinforcing pro-survival circuit.","evidence":"ChIP assay, luciferase reporter, siRNA knockdown in cell culture under oxidative stress","pmids":["34751416"],"confidence":"Medium","gaps":["Whether the CREB–NGB feedback loop operates in vivo during ischemia","Relative contribution of other transcription factors to NGB expression","Epigenetic regulation of NGB promoter not explored"]},{"year":null,"claim":"Key unresolved questions include the identity of the kinase(s) that phosphorylate NGB under hypoxia, the precise stoichiometry and structural basis of the NGB–cytochrome c anti-apoptotic interaction, whether NGB's GDI activity for Gαi operates at endogenous protein concentrations in neurons, and the in vivo significance of NGB-derived NO relative to canonical NO sources during ischemia.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Kinase identity for NGB phosphorylation","NGB–cytochrome c structural interface","Endogenous-level GDI activity validation","In vivo NO quantitation from NGB nitrite reductase"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[5]},{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[12,16]},{"term_id":"GO:0016209","term_label":"antioxidant activity","supporting_discovery_ids":[15,21]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[8,17]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3,7]}],"pathway":[{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[14,19]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[5,17,22]}],"complexes":[],"partners":["GNAI1","FLOT1","CYCS","YWHAB"],"other_free_text":[]},"mechanistic_narrative":"Neuroglobin (NGB) is a monomeric, brain-enriched hexacoordinated globin that couples cellular oxygen and redox status to neuroprotective signaling. Its heme iron shuttles between a six-coordinate bis-histidyl state (His64-Fe-His96) and a five-coordinate state competent for O₂, CO, and nitrite binding, with O₂ affinity modulated ~10-fold by an intramolecular Cys46–Cys55 disulfide bond and by hypoxia-induced phosphorylation that promotes 14-3-3 binding and heme pocket opening [PMID:14530264, PMID:21965683]. In its ferric (oxidized) form NGB acts as a guanine nucleotide dissociation inhibitor for Gαi, liberating Gβγ to initiate survival signaling, and binds cytochrome c to block apoptosome/caspase-9 activation; in its deoxyferrous form it functions as a nitrite reductase generating NO that inhibits mitochondrial respiration via cytochrome c oxidase [PMID:12860983, PMID:20091232, PMID:21296891]. NGB transcription is directly driven by CREB binding to its promoter, and its downstream protective effects converge on the PI3K/Akt/CREB/Nrf2 axis to suppress oxidative stress and mitochondrial apoptosis [PMID:34751416, PMID:31882813]."},"prefetch_data":{"uniprot":{"accession":"Q9NPG2","full_name":"Neuroglobin","aliases":["Nitrite reductase"],"length_aa":151,"mass_kda":16.9,"function":"Monomeric globin with a bis-histidyl six-coordinate heme-iron atom through which it can bind dioxygen, carbon monoxide and nitric oxide (PubMed:11473128, PubMed:12962627, PubMed:24699645). Could help transport oxygen and increase its availability to the metabolically active neuronal tissues, though its low quantity in tissues as well as its high affinity for dioxygen, which may limit its oxygen-releasing ability, argue against it (PubMed:11473128, PubMed:12860983, PubMed:12962627, PubMed:24699645). The ferrous/deoxygenated form exhibits a nitrite reductase activity and it could produce nitric oxide which in turn inhibits cellular respiration in response to hypoxia (PubMed:21296891). In its ferrous/deoxygenated state, it may also exhibit GDI (Guanine nucleotide Dissociation Inhibitor) activity toward heterotrimeric G-alpha proteins, thereby regulating signal transduction to facilitate neuroprotective responses in the wake of hypoxia and associated oxidative stress (PubMed:12860983, PubMed:18302932)","subcellular_location":"Cytoplasm, cytosol; Mitochondrion matrix","url":"https://www.uniprot.org/uniprotkb/Q9NPG2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NGB","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NGB","total_profiled":1310},"omim":[{"mim_id":"605304","title":"NEUROGLOBIN; NGB","url":"https://www.omim.org/entry/605304"},{"mim_id":"104760","title":"AMYLOID BETA A4 PRECURSOR PROTEIN; APP","url":"https://www.omim.org/entry/104760"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"brain","ntpm":75.1}],"url":"https://www.proteinatlas.org/search/NGB"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"Q9NPG2","domains":[{"cath_id":"1.10.490.10","chopping":"4-145","consensus_level":"high","plddt":96.1999,"start":4,"end":145}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NPG2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NPG2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9NPG2-F1-predicted_aligned_error_v6.png","plddt_mean":95.19},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NGB","jax_strain_url":"https://www.jax.org/strain/search?query=NGB"},"sequence":{"accession":"Q9NPG2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9NPG2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9NPG2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9NPG2"}},"corpus_meta":[{"pmid":"16205781","id":"PMC_16205781","title":"The novel dopamine 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Society","url":"https://pubmed.ncbi.nlm.nih.gov/21339183","citation_count":23,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"17210637","id":"PMC_17210637","title":"Identification and characterization of putative tumor suppressor NGB, a GTP-binding protein that interacts with the neurofibromatosis 2 protein.","date":"2007","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/17210637","citation_count":21,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"23080171","id":"PMC_23080171","title":"Human carotid body HIF and NGB expression during human development and aging.","date":"2012","source":"Advances in experimental medicine and biology","url":"https://pubmed.ncbi.nlm.nih.gov/23080171","citation_count":15,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"31827177","id":"PMC_31827177","title":"Effects of Exogenous Neuroglobin (Ngb) on retinal inflammatory chemokines and microglia in a rat model of transient hypoxia.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/31827177","citation_count":13,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"28829495","id":"PMC_28829495","title":"The expression and mechanism of BDNF and NGB in perihematomal tissue in rats with intracerebral hemorrhage.","date":"2017","source":"European review for medical and pharmacological sciences","url":"https://pubmed.ncbi.nlm.nih.gov/28829495","citation_count":13,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"22410316","id":"PMC_22410316","title":"Reduced expression of haloperidol conditioned catalepsy in rats by the dopamine D3 receptor antagonists nafadotride and NGB 2904.","date":"2012","source":"European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/22410316","citation_count":13,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"23456442","id":"PMC_23456442","title":"Neuroprotective effect of TAT PTD-Ngb fusion protein on primary cortical neurons against hypoxia-induced apoptosis.","date":"2013","source":"Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology","url":"https://pubmed.ncbi.nlm.nih.gov/23456442","citation_count":12,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"31882813","id":"PMC_31882813","title":"Mn-TAT PTD-Ngb attenuates oxidative injury by an enhanced ROS scavenging ability and the regulation of redox signaling pathway.","date":"2019","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/31882813","citation_count":11,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"34751416","id":"PMC_34751416","title":"Polydatin protects neuronal cells from hydrogen peroxide damage by activating CREB/Ngb signaling.","date":"2021","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/34751416","citation_count":9,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"36056962","id":"PMC_36056962","title":"A new source of bacterial myrosinase isolated from endophytic Bacillus sp. NGB-B10, and its relevance in biological control activity.","date":"2022","source":"World journal of microbiology & biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/36056962","citation_count":8,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"32470548","id":"PMC_32470548","title":"Mn-TAT PTD-Ngb ameliorates inflammation through the elimination of damaged mitochondria and the activation of Nrf2-antioxidant signaling pathway.","date":"2020","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/32470548","citation_count":7,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"26646387","id":"PMC_26646387","title":"Pichia pastoris Production of Tat-NGB and Its Neuroprotection on Rat Pheochromocytoma Cells.","date":"2016","source":"Molecular biotechnology","url":"https://pubmed.ncbi.nlm.nih.gov/26646387","citation_count":5,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"25131407","id":"PMC_25131407","title":"Suppression of NGB and NAB/ERabp1 in tomato modifies root responses to potato cyst nematode infestation.","date":"2014","source":"Molecular plant pathology","url":"https://pubmed.ncbi.nlm.nih.gov/25131407","citation_count":4,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"35818200","id":"PMC_35818200","title":"Expression Pattern of Ngb in Astrocytes after Spinal Cord Injury and the Clinical Significance.","date":"2022","source":"Cellular and molecular biology (Noisy-le-Grand, France)","url":"https://pubmed.ncbi.nlm.nih.gov/35818200","citation_count":3,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"24325104","id":"PMC_24325104","title":"[Effects of hypoxia preconditioning on serum NGB and S-100B in patients with intracranial aneurysm surgery].","date":"2013","source":"Sichuan da xue xue bao. Yi xue ban = Journal of Sichuan University. Medical science edition","url":"https://pubmed.ncbi.nlm.nih.gov/24325104","citation_count":1,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"41641147","id":"PMC_41641147","title":"Electroacupuncture improves hypoxic stress and energy metabolism to alleviate vascular cognitive impairment through activation of the HIF-1α/p53/NGB signaling pathway in rats.","date":"2026","source":"Iranian journal of basic medical sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41641147","citation_count":0,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":null,"id":"bio_10.1101_2025.08.05.25333018","title":"Lack of policy support for chronic conditions in UK sport: a scoping review of National Governing Bodies","date":"2025-08-07","source":"bioRxiv","url":"https://doi.org/10.1101/2025.08.05.25333018","citation_count":0,"is_preprint":true,"source_track":"pubmed_title"},{"pmid":null,"id":"bio_10.1101_2024.08.20.608782","title":"Genomic loci for sclerotinia stem rot resistance and chlorophyll stability in<i>Brassica napus</i>: integrating GWAS with microbiome insights","date":"2024-08-20","source":"bioRxiv","url":"https://doi.org/10.1101/2024.08.20.608782","citation_count":0,"is_preprint":true,"source_track":"pubmed_title"},{"pmid":"12477932","id":"PMC_12477932","title":"Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences.","date":"2002","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/12477932","citation_count":1479,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28514442","id":"PMC_28514442","title":"Architecture of the human interactome defines protein communities and disease networks.","date":"2017","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/28514442","citation_count":1085,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"25416956","id":"PMC_25416956","title":"A proteome-scale map of the human interactome network.","date":"2014","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/25416956","citation_count":977,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"32296183","id":"PMC_32296183","title":"A reference map of the human binary protein interactome.","date":"2020","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/32296183","citation_count":849,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"11029004","id":"PMC_11029004","title":"A vertebrate globin expressed in the brain.","date":"2000","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/11029004","citation_count":805,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"33961781","id":"PMC_33961781","title":"Dual proteome-scale networks reveal cell-specific remodeling of the human interactome.","date":"2021","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/33961781","citation_count":705,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21873635","id":"PMC_21873635","title":"Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium.","date":"2011","source":"Briefings in bioinformatics","url":"https://pubmed.ncbi.nlm.nih.gov/21873635","citation_count":656,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15489334","id":"PMC_15489334","title":"The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC).","date":"2004","source":"Genome research","url":"https://pubmed.ncbi.nlm.nih.gov/15489334","citation_count":438,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"11473128","id":"PMC_11473128","title":"Biochemical characterization and ligand binding properties of neuroglobin, a novel member of the globin family.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11473128","citation_count":392,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12962627","id":"PMC_12962627","title":"Human brain neuroglobin structure reveals a distinct mode of controlling oxygen affinity.","date":"2003","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/12962627","citation_count":267,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15598495","id":"PMC_15598495","title":"Neuroglobin and cytoglobin in search of their role in the vertebrate globin family.","date":"2005","source":"Journal of inorganic biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15598495","citation_count":237,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"14530264","id":"PMC_14530264","title":"The redox state of the cell regulates the ligand binding affinity of human neuroglobin and cytoglobin.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/14530264","citation_count":233,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21296891","id":"PMC_21296891","title":"Human neuroglobin functions as a redox-regulated nitrite reductase.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21296891","citation_count":228,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12860983","id":"PMC_12860983","title":"Oxidized human neuroglobin acts as a heterotrimeric Galpha protein guanine nucleotide dissociation inhibitor.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12860983","citation_count":161,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15299006","id":"PMC_15299006","title":"Allosteric regulation and temperature dependence of oxygen binding in human neuroglobin and cytoglobin. Molecular mechanisms and physiological significance.","date":"2004","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/15299006","citation_count":156,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"20091232","id":"PMC_20091232","title":"Neuroglobin protects nerve cells from apoptosis by inhibiting the intrinsic pathway of cell death.","date":"2010","source":"Apoptosis : an international journal on programmed cell death","url":"https://pubmed.ncbi.nlm.nih.gov/20091232","citation_count":131,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12850561","id":"PMC_12850561","title":"Localization of neuroglobin protein in the mouse brain.","date":"2003","source":"Neuroscience letters","url":"https://pubmed.ncbi.nlm.nih.gov/12850561","citation_count":97,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12508121","id":"PMC_12508121","title":"The DNA sequence and analysis of human chromosome 14.","date":"2003","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/12508121","citation_count":80,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"12239161","id":"PMC_12239161","title":"Hemin induces neuroglobin expression in neural cells.","date":"2002","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/12239161","citation_count":77,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"20075359","id":"PMC_20075359","title":"Neuroglobin expression in ischemic stroke.","date":"2010","source":"Stroke","url":"https://pubmed.ncbi.nlm.nih.gov/20075359","citation_count":74,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"20571522","id":"PMC_20571522","title":"Neuroglobin protects neurons against oxidative stress in global ischemia.","date":"2010","source":"Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/20571522","citation_count":73,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"11820779","id":"PMC_11820779","title":"Full-length cDNA cloning of human neuroglobin and tissue expression of rat neuroglobin.","date":"2002","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/11820779","citation_count":69,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"21965683","id":"PMC_21965683","title":"14-3-3 binding and phosphorylation of neuroglobin during hypoxia modulate six-to-five heme pocket coordination and rate of nitrite reduction to nitric oxide.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21965683","citation_count":66,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"28700943","id":"PMC_28700943","title":"A Role for Mitochondrial Translation in Promotion of Viability in K-Ras Mutant Cells.","date":"2017","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/28700943","citation_count":64,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"15120622","id":"PMC_15120622","title":"Human neuroglobin interacts with flotillin-1, a lipid raft microdomain-associated protein.","date":"2004","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/15120622","citation_count":60,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"17975837","id":"PMC_17975837","title":"Exploring the molecular basis of heme coordination in human neuroglobin.","date":"2008","source":"Proteins","url":"https://pubmed.ncbi.nlm.nih.gov/17975837","citation_count":58,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"14645216","id":"PMC_14645216","title":"Residues in the distal heme pocket of neuroglobin. Implications for the multiple ligand binding steps.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/14645216","citation_count":57,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"16201751","id":"PMC_16201751","title":"Structural characterization of the proximal and distal histidine environment of cytoglobin and neuroglobin.","date":"2005","source":"Biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/16201751","citation_count":54,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"24699645","id":"PMC_24699645","title":"The crystal structure of wild-type human brain neuroglobin reveals flexibility of the disulfide bond that regulates oxygen affinity.","date":"2014","source":"Acta crystallographica. Section D, Biological crystallography","url":"https://pubmed.ncbi.nlm.nih.gov/24699645","citation_count":54,"is_preprint":false,"source_track":"gene2pubmed"},{"pmid":"17600531","id":"PMC_17600531","title":"Reactivity and endogenous modification by nitrite and hydrogen peroxide: does human neuroglobin act only as a scavenger?","date":"2007","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/17600531","citation_count":53,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16231,"output_tokens":1920,"usd":0.038747},"stage2":{"model":"claude-opus-4-6","input_tokens":4863,"output_tokens":1977,"usd":0.11061},"total_usd":0.393374,"stage1_batch_id":"msgbatch_012ZiiCUBfB62NCTQd4Bk1Jo","stage2_batch_id":"msgbatch_01Xuqq9aUHoQouS7UVGZNStZ","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":29153,"output_tokens":5001,"usd":0.081237},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":8804,"output_tokens":2580,"usd":0.16278}},"stage1_raw":"Looking at the corpus, I need to identify which papers are about the human/mammalian gene NGB (Neuroglobin). Let me sort through:\n\n- Papers 1-8, 15: About NGB 2904, a dopamine D3 receptor antagonist drug compound — NOT the gene NGB\n- Papers 9-10, 12-14, 16-18, 20-21, 23-25: About Neuroglobin (Ngb/NGB) protein — these are relevant\n- Paper 11: About NGB as a GTP-binding protein that interacts with NF2/merlin — this is a different protein called NGB\n- Paper 19: Bacillus sp. NGB-B10 myrosinase — SKIP (microbial symbol collision)\n- Paper 22: Plant NGB (small GTP-binding protein in tomato) — SKIP (plant symbol collision)\n- Paper 26: NGB = National Governing Bodies — SKIP\n- Paper 27: NGB = accession codes — SKIP\n\nThe mammalian NGB gene encodes Neuroglobin, a neuroprotective globin protein. Paper 11 describes a different protein (GTP-binding protein interacting with NF2/merlin) — this appears to be a symbol collision with a different human gene, not neuroglobin.\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"Neuroglobin (Ngb) promotes Akt phosphorylation and activates CREB-mediated cell survival signaling; in an Alzheimer's disease rat model, IBU-LA treatment maintained high Ngb levels, which correlated with restored p-Akt/Akt and p-CREB/CREB ratios and reduced cytochrome C/Apaf-1 complex formation (anti-apoptotic), as assessed by Western blot and co-immunoprecipitation.\",\n      \"method\": \"Western blot, co-immunoprecipitation, immunohistochemistry in AD rat model\",\n      \"journal\": \"Gerontology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, multiple methods but indirect (correlative manipulation of Ngb levels via drug treatment rather than direct Ngb gain/loss-of-function)\",\n      \"pmids\": [\"23428737\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"TAT PTD-Ngb fusion protein, delivering exogenous Ngb intracellularly into primary cortical neurons, protected against hypoxia-induced apoptosis by increasing Bcl-2 expression and decreasing caspase-3 and caspase-9 activities, implicating the mitochondrial apoptosis pathway as a target of Ngb neuroprotection.\",\n      \"method\": \"TAT PTD-mediated protein transduction into primary neurons, MTT assay, transmission electron microscopy, Western blot for Bcl-2, caspase-3, caspase-9 activity assay under hypoxia\",\n      \"journal\": \"Neurological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct loss/gain-of-function with defined cellular phenotype and pathway readout in single lab\",\n      \"pmids\": [\"23456442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Mn-TAT PTD-Ngb, a manganese porphyrin reconstituted Ngb fusion protein, scavenges ROS and activates the PI3K/Akt signaling pathway, upregulating Nrf2, HO-1, SOD, and catalase, thereby suppressing mitochondria-dependent apoptosis and oxidative injury in neuronal cells.\",\n      \"method\": \"Recombinant protein engineering, ROS scavenging assay, mitochondrial function assay, Western blot for PI3K/Akt/Nrf2/HO-1 pathway, apoptosis assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro reconstitution with defined pathway readouts, single lab\",\n      \"pmids\": [\"31882813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CREB directly binds the promoter region of the Ngb gene and activates its transcription; the AKT/CREB/Ngb signaling axis mediates neuroprotection against H2O2-induced oxidative injury, as demonstrated by Ngb knockdown abolishing the protective effect of polydatin.\",\n      \"method\": \"Luciferase reporter assay, ChIP (CREB binding to Ngb promoter), AKT/CREB phosphorylation by Western blot, siRNA knockdown of Ngb with phenotypic rescue assessment\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — luciferase + ChIP + siRNA knockdown with phenotypic readout in single lab\",\n      \"pmids\": [\"34751416\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Mn-TAT PTD-Ngb suppresses the NF-κB nuclear translocation, MAPK phosphorylation, ROS production, and NLRP3 inflammasome assembly (blocking IL-1β and IL-18 release) during LPS-induced inflammation, and activates Nrf2 to reduce oxidative stress and pyroptosis in neuronal cells.\",\n      \"method\": \"Recombinant protein treatment of LPS-stimulated cells, Western blot for NF-κB, MAPK, Nrf2, ELISA for cytokines, ROS assay, mitochondrial function assay\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — multiple pathway readouts with recombinant protein, single lab\",\n      \"pmids\": [\"32470548\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Intravitreal delivery of exogenous Neuroglobin protein to hypoxic rat retina restores Ngb concentration to normoxic levels and significantly reduces IL-6, TNFα, IL-1β, RANTES, MCP-1, and VEGF, and decreases microglial activation, establishing a direct anti-inflammatory and neuroprotective role for Ngb in the retina.\",\n      \"method\": \"Intravitreal protein injection in rat hypoxia model, immunohistochemistry, ELISA for chemokines/cytokines, retinal Ngb concentration measurement\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct protein delivery with defined inflammatory and cellular phenotype readouts, single lab\",\n      \"pmids\": [\"31827177\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"Neuroglobin (NGB) is a neuroprotective globin protein that, in response to hypoxic/ischemic or oxidative stress, activates the PI3K/Akt/CREB signaling axis to transcriptionally upregulate its own expression and pro-survival genes, suppresses the mitochondrial apoptosis pathway (via Bcl-2 upregulation and caspase-3/9 inhibition), scavenges ROS, activates the Nrf2/HO-1 antioxidant response, and inhibits NF-κB-driven neuroinflammation and inflammasome assembly.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"Neuroglobin (NGB) was identified as a third vertebrate globin type, predominantly expressed in the brain, functioning as a monomeric oxygen-binding protein with high O2 affinity (P50 ~2 torr), analogous to myoglobin in potentially increasing O2 availability to brain tissue.\",\n      \"method\": \"cDNA cloning, recombinant protein expression, O2 affinity measurement\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — original discovery paper with recombinant protein biochemistry, highly cited foundational study\",\n      \"pmids\": [\"11029004\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Human and mouse recombinant NGB display a hexacoordinated deoxy ferrous heme (His-Fe2+-His), where the distal histidine (E7-His) acts as the endogenous ligand; O2 and CO can displace this endogenous ligand. NGB has high autoxidation rate, and mouse NGB exists as a monomer with disulfide-dependent dimer formation.\",\n      \"method\": \"Spectral measurements, flash photolysis, site-directed mutagenesis, recombinant protein biochemistry\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — recombinant protein reconstitution with mutagenesis and multiple spectroscopic methods, foundational mechanistic study\",\n      \"pmids\": [\"11473128\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Neuroglobin expression in neural cells is induced by hemin via a cGMP/protein kinase G pathway (not the MAPK pathway used by hypoxia), demonstrating two distinct signal transduction pathways regulate NGB expression.\",\n      \"method\": \"RT-PCR, Western blot, pharmacological inhibitors (KT5823, LY83583, PD98059), cGMP measurement\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple inhibitors used in cell-based assays with mechanistic follow-up, single lab\",\n      \"pmids\": [\"12239161\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"Full-length human NGB cDNA was cloned; NGB protein immunoreactive signals were localized to the cytoplasm and processes of neurons, distributed throughout rat brain regions including cerebral cortex, hippocampus, thalamus, hypothalamus, pons, and cerebellum.\",\n      \"method\": \"RACE cloning, in situ hybridization, immunohistochemistry\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct protein localization by immunohistochemistry with validated antibody\",\n      \"pmids\": [\"11820779\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"X-ray crystal structure of human brain NGB revealed a classical globin fold with hexacoordinated heme, an elongated protein matrix cavity that facilitates O2 diffusion, and structural adaptations to host the reversible bis-histidyl heme complex.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional interpretation\",\n      \"pmids\": [\"12962627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Oxidized (ferric) NGB binds exclusively to the GDP-bound form of Gαi heterotrimeric G protein subunit, acting as a guanine nucleotide dissociation inhibitor (GDI) that inhibits GDP-to-GTP exchange, thereby liberating Gβγ and promoting neuronal survival. Ferrous ligand-bound NGB under normoxia lacks GDI activity.\",\n      \"method\": \"Surface plasmon resonance, GDP dissociation assays, GTPγS binding assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical reconstitution with multiple functional assays, redox-state specificity demonstrated\",\n      \"pmids\": [\"12860983\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"His64 is the endogenous distal heme ligand in NGB and Lys67 is situated nearby in the distal pocket; His96 is the proximal ligand (its mutation causes complete loss of heme). CO binding kinetics are biphasic due to His64 and Lys67 in the distal pocket.\",\n      \"method\": \"Site-directed mutagenesis, resonance Raman spectroscopy, flash photolysis\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis combined with spectroscopic methods, multiple mutants characterized\",\n      \"pmids\": [\"14645216\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"NGB protein is widely expressed in neurons of the mouse brain including cerebral cortex, subcortical structures, brainstem nuclei, and cerebellum, with regionally differing expression levels consistent with variation in hypoxic tolerance.\",\n      \"method\": \"Immunohistochemistry with affinity-purified polyclonal antibody\",\n      \"journal\": \"Neuroscience letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct protein localization with validated antibody\",\n      \"pmids\": [\"12850561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Formation of an intramolecular disulfide bond between Cys46 (CD7) and Cys55 (D5) in human NGB increases O2 affinity by approximately 10-fold by slowing histidine dissociation rate; breaking the S-S bond (by reduction or mutagenesis) decreases O2 affinity. This links the redox state of the cell to NGB's O2 binding affinity.\",\n      \"method\": \"Mass spectrometry, thiol accessibility studies, site-directed mutagenesis, O2 binding assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal methods including mutagenesis, MS, and ligand binding assays\",\n      \"pmids\": [\"14530264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Human NGB interacts with flotillin-1, a lipid raft microdomain-associated protein, identified by yeast two-hybrid screening of a human brain cDNA library and confirmed by GST pull-down; flotillin-1 may recruit NGB to lipid rafts as part of neuroprotective signaling.\",\n      \"method\": \"Yeast two-hybrid, GST pull-down\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — yeast two-hybrid plus GST pull-down, single lab, no functional follow-up in neurons\",\n      \"pmids\": [\"15120622\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"NGB shows alkaline and acid Bohr effects (pH-dependent O2 affinity) and temperature-dependent enthalpy of oxygenation. His(E7) stabilizes bound O2 and functions as a major Bohr group in the presence of Lys(E10), as shown by mutant analysis.\",\n      \"method\": \"O2 equilibrium binding with recombinant mutant proteins, thiol titration, mass spectrometry\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — recombinant mutant proteins with multiple ligand binding assays\",\n      \"pmids\": [\"15299006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Spectroscopic characterization confirmed His64 as the distal ligand and His96 as the proximal ligand in NGB; the CO adduct of NGB contains three conformers, with His64 contributing to conformer interconversion. Fe-His stretching frequency of the photolyzed 5-coordinate NGB is 221 cm−1.\",\n      \"method\": \"Picosecond time-resolved resonance Raman spectroscopy, FT-IR, distal mutant analysis\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple spectroscopic methods with mutagenesis\",\n      \"pmids\": [\"16201751\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"MetNGB (ferric NGB) reacts with nitrite (NO2−) and H2O2 to generate an active species with peroxynitrite-like properties that nitrates phenolic substrates; the disulfide bond (Cys46-Cys55) affects this reactivity. NGB can also be self-modified at endogenous Tyr (to 3-nitrotyrosine) and Cys (to sulfinic/sulfonic acid) residues.\",\n      \"method\": \"Kinetic assays, nitrite-binding studies, HPLC-MS/MS analysis of modified residues\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical assays with MS/MS characterization of modifications\",\n      \"pmids\": [\"17600531\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Molecular dynamics simulations showed that protein oxidation (disulfide bond formation between CysCD7 and CysD5) promotes stabilization of the pentacoordinated (5c) heme species, favoring the more reactive state and supporting an O2 storage/sensor function whereby O2 would be released under hypoxic/oxidizing conditions.\",\n      \"method\": \"Molecular dynamics simulation, free energy calculations\",\n      \"journal\": \"Proteins\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — computational prediction only, no experimental validation in this paper\",\n      \"pmids\": [\"17975837\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"NGB inhibits the intrinsic apoptosis pathway by interacting with cytochrome c, thereby blocking apoptosome formation and pro-caspase 9 activation. NGB protection is concentration-sensitive and involves both binding to cytochrome c and subsequent redox reaction.\",\n      \"method\": \"Cell biology and biochemical apoptosis assays, computational modeling of apoptotic signaling\",\n      \"journal\": \"Apoptosis : an international journal on programmed cell death\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct binding to cytochrome c demonstrated with functional inhibition of caspase 9, single lab\",\n      \"pmids\": [\"20091232\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Transgenic NGB-overexpressing mice show markedly reduced ROS/RNS production, lipid peroxidation, and CA1 neuronal injury after hippocampal ischemia-reperfusion, demonstrating NGB's antioxidant protective role in vivo.\",\n      \"method\": \"Transgenic mouse model, bilateral carotid occlusion, cresyl violet staining, malonyldialdehyde assay, ROS/RNS staining\",\n      \"journal\": \"Journal of cerebral blood flow and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — transgenic in vivo model with multiple readouts, single lab\",\n      \"pmids\": [\"20571522\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Deoxygenated human NGB functions as a redox-regulated nitrite reductase, converting nitrite to NO. This activity is regulated by surface thiols Cys55 and Cys46 that modulate six-to-five heme coordination. Distal His-to-Leu/Gln mutants reduce nitrite ~2000-fold faster. In cells, NGB nitrite reductase activity inhibits cellular respiration via NO binding to cytochrome c oxidase, confirming a role in intracellular hypoxic NO-signaling.\",\n      \"method\": \"In vitro nitrite reduction assays, site-directed mutagenesis, lentiviral cell expression, respiration measurements\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with mutagenesis plus cellular validation with multiple orthogonal approaches\",\n      \"pmids\": [\"21296891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"NGB is phosphorylated during hypoxia and glucose deprivation, and this phosphorylation promotes interaction with 14-3-3 proteins; 14-3-3 binding stabilizes NGB phosphorylation and increases the open probability of the heme pocket (5-coordinate fraction), accelerating nitrite reduction to NO. This reveals a hypoxia-dependent post-translational modification cascade regulating NGB's heme reactivity.\",\n      \"method\": \"Co-immunoprecipitation, phosphorylation assays, CO/nitrite binding kinetics, SH-SY5Y cell hypoxia experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP plus functional ligand binding studies in both in vitro and cellular settings\",\n      \"pmids\": [\"21965683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"NGB promotes cell survival via the Akt phosphorylation/CREB signaling pathway; in an Alzheimer's disease rat model, IBU-LA treatment maintained high Ngb levels, which correlated with restored p-Akt/Akt and p-CREB/CREB ratios and reduced cytochrome C/Apaf1 complex formation, implicating NGB in activation of the Akt/CREB pro-survival axis.\",\n      \"method\": \"Western blot, co-immunoprecipitation (cytochrome C/Apaf1), TUNEL, immunohistochemistry\",\n      \"journal\": \"Gerontology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — correlative Western blot data in rat model, indirect evidence for NGB-Akt link\",\n      \"pmids\": [\"23428737\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Exogenous TAT PTD-Ngb fusion protein transduces into primary cortical neurons and protects against hypoxia-induced apoptosis by increasing Bcl-2 expression and decreasing caspase-3 and caspase-9 activity, indicating NGB suppresses the mitochondrial apoptotic pathway.\",\n      \"method\": \"Fluorescent immunostaining, MTT assay, TEM, Western blot for Bcl-2/caspase-3/caspase-9\",\n      \"journal\": \"Neurological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — cell-based loss/gain of function with multiple molecular readouts of apoptotic pathway\",\n      \"pmids\": [\"23456442\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The wild-type human neuroglobin crystal structure at 1.74 Å resolution revealed two distinct conformations of the CD region containing the Cys46-Cys55 intramolecular disulfide link, and identified internal cavities involved in ligand migration and conformational transitions between low and high O2-affinity states.\",\n      \"method\": \"X-ray crystallography\",\n      \"journal\": \"Acta crystallographica. Section D, Biological crystallography\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — high-resolution crystal structure with direct observation of disulfide bond conformational flexibility\",\n      \"pmids\": [\"24699645\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Mn-TAT PTD-Ngb, a manganese porphyrin reconstituted NGB fusion protein, has enhanced ROS scavenging ability compared to TAT PTD-Ngb, reduces intracellular ROS, restores mitochondrial function, inhibits mitochondria-dependent apoptosis, and activates the PI3K/Akt/Nrf2/HO-1 redox signaling pathway.\",\n      \"method\": \"ROS assays, mitochondrial function assays, Western blot for PI3K/Akt/Nrf2/HO-1, cell viability assays\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple biochemical readouts in cell-based system, engineered protein variant\",\n      \"pmids\": [\"31882813\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NGB transcription is activated by CREB, which directly binds the NGB promoter. Polydatin activates AKT/CREB signaling to upregulate NGB expression, and NGB knockdown abolishes polydatin's neuroprotective effect against H2O2, placing NGB downstream of CREB in a neuroprotective signaling cascade.\",\n      \"method\": \"Luciferase reporter assay, ChIP assay, siRNA knockdown, Western blot, cell viability assay\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct ChIP and reporter assay demonstrating CREB-NGB promoter binding, with functional KD validation\",\n      \"pmids\": [\"34751416\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NGB (neuroglobin) is a brain-enriched hexacoordinated globin whose heme iron cycles between six-coordinate (His64-Fe-His96 bis-histidyl) and five-coordinate states; O2/CO binding affinity is regulated by a redox-sensitive intramolecular Cys46-Cys55 disulfide bond and by hypoxia-induced phosphorylation and 14-3-3 interaction; in its oxidized (ferric) state NGB acts as a GDI for Gαi to liberate Gβγ and promote survival signaling, binds cytochrome c to block apoptosome/caspase-9 activation, and in its deoxygenated state functions as a nitrite reductase generating NO to modulate cellular respiration, collectively defining NGB as a redox- and hypoxia-responsive sensor that couples oxygen status to neuroprotective signaling pathways including PI3K/Akt/CREB/Nrf2.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"Neuroglobin (NGB) is a neuroprotective heme-containing globin that counteracts hypoxic, ischemic, and oxidative injury in neurons by engaging the PI3K/Akt signaling cascade, which leads to CREB-mediated transcriptional activation of pro-survival targets including the NGB gene itself [PMID:23428737, PMID:34751416]. Exogenous NGB delivery suppresses the mitochondrial apoptosis pathway by upregulating Bcl-2 and inhibiting caspase-3 and caspase-9 activities, while also scavenging reactive oxygen species and activating the Nrf2/HO-1 antioxidant response [PMID:23456442, PMID:31882813]. NGB additionally inhibits NF-κB nuclear translocation and NLRP3 inflammasome assembly, reducing pro-inflammatory cytokine release and pyroptosis in neuroinflammatory contexts [PMID:32470548, PMID:31827177].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Establishing that NGB correlates with pro-survival Akt/CREB signaling and anti-apoptotic mitochondrial regulation answered whether NGB engages defined intracellular survival pathways during neurodegeneration.\",\n      \"evidence\": \"Western blot, co-immunoprecipitation, and immunohistochemistry in an Alzheimer's disease rat model treated with IBU-LA to maintain NGB levels\",\n      \"pmids\": [\"23428737\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"NGB levels were modulated indirectly via drug treatment rather than direct genetic manipulation\",\n        \"Causal direction between NGB and Akt/CREB activation not established\",\n        \"No assessment of NGB enzymatic activity (ligand binding, redox cycling) in this context\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Direct intracellular delivery of NGB protein demonstrated that it is sufficient to protect neurons from hypoxia-induced apoptosis by modulating Bcl-2 and caspase activities, pinpointing the mitochondrial apoptosis pathway as a downstream effector.\",\n      \"evidence\": \"TAT PTD-Ngb transduction into primary cortical neurons with MTT viability assay, electron microscopy, and Western blot/caspase activity assays under hypoxia\",\n      \"pmids\": [\"23456442\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism by which NGB upregulates Bcl-2 is undefined\",\n        \"No loss-of-function (knockdown/knockout) complement to the gain-of-function experiment\",\n        \"Findings limited to a single primary neuron culture system\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Engineered Mn-reconstituted NGB was shown to directly scavenge ROS and activate the PI3K/Akt/Nrf2/HO-1 axis, linking NGB's redox chemistry to an antioxidant transcriptional program and clarifying how NGB suppresses oxidative injury beyond simple oxygen binding.\",\n      \"evidence\": \"Recombinant Mn-TAT PTD-Ngb protein with ROS scavenging, mitochondrial function, and Western blot pathway readouts in neuronal cells\",\n      \"pmids\": [\"31882813\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Manganese porphyrin substitution may not fully recapitulate native heme-iron NGB activity\",\n        \"Relative contributions of direct ROS scavenging versus signaling pathway activation are unresolved\",\n        \"In vivo validation of this engineered construct was not performed\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"In vivo delivery of NGB protein to the hypoxic retina reduced pro-inflammatory cytokines and microglial activation, extending NGB's neuroprotective and anti-inflammatory function to a defined tissue beyond the brain.\",\n      \"evidence\": \"Intravitreal NGB protein injection in a rat hypoxia model with ELISA for cytokines/chemokines and immunohistochemistry for microglia\",\n      \"pmids\": [\"31827177\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Signaling pathway mediating anti-inflammatory action in retina was not delineated\",\n        \"Long-term functional visual outcomes were not assessed\",\n        \"Single model system without genetic loss-of-function control\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrating that NGB suppresses NF-κB nuclear translocation and NLRP3 inflammasome assembly resolved how NGB exerts anti-inflammatory activity at the molecular level, adding inflammasome inhibition and anti-pyroptotic effects to its functional repertoire.\",\n      \"evidence\": \"Mn-TAT PTD-Ngb treatment of LPS-stimulated neuronal cells with Western blot for NF-κB/MAPK/Nrf2, ELISA for IL-1β/IL-18, ROS assay\",\n      \"pmids\": [\"32470548\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct physical interaction between NGB and NF-κB or NLRP3 components not demonstrated\",\n        \"Engineered Mn-porphyrin construct used rather than wild-type heme NGB\",\n        \"Mechanism of NGB access to inflammatory signaling complexes is unknown\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identification of CREB as a direct transcriptional activator of the NGB promoter established a positive-feedback loop (Akt→CREB→NGB) and demonstrated that NGB is required for neuroprotection against oxidative stress, as its knockdown abolished the protective phenotype.\",\n      \"evidence\": \"Luciferase reporter assay and ChIP showing CREB binding to NGB promoter; siRNA knockdown of NGB with loss of protection against H₂O₂\",\n      \"pmids\": [\"34751416\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Other transcription factors regulating NGB expression were not explored\",\n        \"Feedback loop kinetics and saturation behavior are uncharacterized\",\n        \"Validation limited to a single oxidative stress stimulus (H₂O₂)\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The direct molecular targets through which NGB protein engages PI3K/Akt signaling, and whether NGB's endogenous ligand-binding or redox-cycling activity is required for signal transduction, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No direct binding partner for NGB upstream of PI3K has been identified\",\n        \"No structure–function study dissecting heme redox state requirements for neuroprotection\",\n        \"No NGB conditional knockout in vivo model confirming endogenous necessity for neuroprotection\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016209\", \"supporting_discovery_ids\": [2, 4]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [4, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"AKT1\",\n      \"CREB1\",\n      \"NRF2\",\n      \"BCL2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"Neuroglobin (NGB) is a monomeric, brain-enriched hexacoordinated globin that couples cellular oxygen and redox status to neuroprotective signaling. Its heme iron shuttles between a six-coordinate bis-histidyl state (His64-Fe-His96) and a five-coordinate state competent for O₂, CO, and nitrite binding, with O₂ affinity modulated ~10-fold by an intramolecular Cys46–Cys55 disulfide bond and by hypoxia-induced phosphorylation that promotes 14-3-3 binding and heme pocket opening [PMID:14530264, PMID:21965683]. In its ferric (oxidized) form NGB acts as a guanine nucleotide dissociation inhibitor for Gαi, liberating Gβγ to initiate survival signaling, and binds cytochrome c to block apoptosome/caspase-9 activation; in its deoxyferrous form it functions as a nitrite reductase generating NO that inhibits mitochondrial respiration via cytochrome c oxidase [PMID:12860983, PMID:20091232, PMID:21296891]. NGB transcription is directly driven by CREB binding to its promoter, and its downstream protective effects converge on the PI3K/Akt/CREB/Nrf2 axis to suppress oxidative stress and mitochondrial apoptosis [PMID:34751416, PMID:31882813].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Identification of NGB as a novel vertebrate globin with high O₂ affinity predominantly expressed in the brain established that neurons possess a dedicated oxygen-binding protein distinct from hemoglobin and myoglobin.\",\n      \"evidence\": \"cDNA cloning, recombinant protein expression, O₂ equilibrium measurements showing P50 ~2 torr\",\n      \"pmids\": [\"11029004\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological function beyond O₂ supply was unknown\", \"Subcellular localization not resolved\", \"Regulation of expression not characterized\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"The demonstration that deoxy-NGB adopts a hexacoordinated bis-histidyl heme (His-Fe²⁺-His) explained why exogenous ligands must compete with an internal ligand, fundamentally distinguishing NGB's ligand-binding mechanism from classical pentacoordinate globins.\",\n      \"evidence\": \"Absorption spectroscopy, flash photolysis, and site-directed mutagenesis of recombinant human and mouse NGB\",\n      \"pmids\": [\"11473128\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of distal and proximal histidines not yet confirmed by mutagenesis\", \"Functional consequence of hexacoordination in cells unknown\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Crystal structures and systematic mutagenesis identified His64 as the distal ligand and His96 as the proximal ligand, revealed the globin fold with an elongated internal cavity system for ligand migration, and showed that the Cys46–Cys55 disulfide bond increases O₂ affinity ~10-fold by modulating histidine dissociation rate — directly linking cellular redox state to NGB's gas-binding properties.\",\n      \"evidence\": \"X-ray crystallography, resonance Raman spectroscopy, site-directed mutagenesis, mass spectrometry, and O₂ binding assays\",\n      \"pmids\": [\"12962627\", \"14645216\", \"14530264\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether disulfide-dependent affinity shift operates under physiological redox conditions in neurons\", \"Structural basis for transition between 6c and 5c states not fully resolved\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"The discovery that ferric NGB acts as a GDI for Gαi — binding exclusively to GDP-Gαi, blocking nucleotide exchange, and liberating Gβγ — established a non-canonical signaling function for a globin and linked NGB's oxidation state to G-protein-coupled neuroprotective signaling.\",\n      \"evidence\": \"Surface plasmon resonance, GDP dissociation and GTPγS binding assays with purified proteins\",\n      \"pmids\": [\"12860983\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo confirmation of NGB-Gαi interaction in neurons\", \"Which downstream effectors of Gβγ mediate the survival signal\", \"Whether GDI activity occurs at endogenous NGB concentrations\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Demonstration that NGB binds cytochrome c to block apoptosome assembly and caspase-9 activation, and that NGB overexpression reduces ROS/RNS and neuronal death after ischemia in vivo, established NGB as an anti-apoptotic factor operating at the mitochondrial pathway.\",\n      \"evidence\": \"Cytochrome c binding and caspase inhibition assays; NGB-overexpressing transgenic mice subjected to bilateral carotid occlusion with ROS, lipid peroxidation, and histological readouts\",\n      \"pmids\": [\"20091232\", \"20571522\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and affinity of NGB–cytochrome c interaction in the cytosol\", \"Whether NGB directly reduces cytochrome c or blocks its interaction with Apaf-1\", \"Contribution relative to other anti-apoptotic proteins\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Establishing that deoxygenated NGB is a nitrite reductase generating NO — regulated by the Cys46/Cys55 disulfide and by hypoxia-induced phosphorylation and 14-3-3 binding that stabilize the 5-coordinate state — revealed a post-translational modification cascade that tunes NGB's enzymatic activity to inhibit mitochondrial respiration under hypoxia.\",\n      \"evidence\": \"In vitro nitrite reduction kinetics with WT and mutant NGB; lentiviral expression in cells with respirometry; co-IP of phospho-NGB with 14-3-3 under hypoxia in SH-SY5Y cells\",\n      \"pmids\": [\"21296891\", \"21965683\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the kinase(s) phosphorylating NGB\", \"Quantitative contribution of NGB-derived NO relative to NOS-derived NO in hypoxic neurons\", \"Whether 14-3-3 isoform selectivity exists\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"A high-resolution (1.74 Å) crystal structure of wild-type NGB captured two conformations of the CD loop harboring the Cys46–Cys55 disulfide, providing a structural basis for the redox-sensitive transition between high- and low-affinity O₂ binding states.\",\n      \"evidence\": \"X-ray crystallography at 1.74 Å resolution\",\n      \"pmids\": [\"24699645\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structure of the reduced (dithiol) form for direct comparison\", \"Dynamics of conformational switching in solution remain uncharacterized\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showing that CREB directly binds the NGB promoter and that NGB knockdown abolishes Akt/CREB-mediated neuroprotection closed a positive feedback loop: NGB activates Akt/CREB signaling, and CREB in turn drives NGB transcription, placing NGB as both effector and target of a self-reinforcing pro-survival circuit.\",\n      \"evidence\": \"ChIP assay, luciferase reporter, siRNA knockdown in cell culture under oxidative stress\",\n      \"pmids\": [\"34751416\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether the CREB–NGB feedback loop operates in vivo during ischemia\", \"Relative contribution of other transcription factors to NGB expression\", \"Epigenetic regulation of NGB promoter not explored\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the identity of the kinase(s) that phosphorylate NGB under hypoxia, the precise stoichiometry and structural basis of the NGB–cytochrome c anti-apoptotic interaction, whether NGB's GDI activity for Gαi operates at endogenous protein concentrations in neurons, and the in vivo significance of NGB-derived NO relative to canonical NO sources during ischemia.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Kinase identity for NGB phosphorylation\", \"NGB–cytochrome c structural interface\", \"Endogenous-level GDI activity validation\", \"In vivo NO quantitation from NGB nitrite reductase\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [12, 16]},\n      {\"term_id\": \"GO:0016209\", \"supporting_discovery_ids\": [15, 21]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [8, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0162582\", \"supporting_discovery_ids\": [5, 17]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [14, 19]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [5, 17, 22]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"GNAI1\",\n      \"FLOT1\",\n      \"CYCS\",\n      \"YWHAB\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}