{"gene":"TAC3","run_date":"2026-04-28T21:42:58","timeline":{"discoveries":[{"year":2010,"finding":"Loss-of-function mutations in TAC3 (neurokinin B gene) cause normosmic congenital hypogonadotropic hypogonadism (CHH) in humans by impairing hypothalamic GnRH pulsatile release; pulsatile GnRH administration restored LH secretion and fertility, establishing the hypothalamic origin of the gonadotropin deficiency.","method":"Human genetics (homozygous splice-site mutations in TAC3 identified in CHH patients), hormonal profiling, pulsatile GnRH challenge","journal":"The Journal of clinical endocrinology and metabolism","confidence":"High","confidence_rationale":"Tier 2 — loss-of-function human genetics with defined neuroendocrine phenotype, replicated across multiple unrelated kindreds","pmids":["20194706"],"is_preprint":false},{"year":2011,"finding":"TAC3 mutations (splice-site deletion of neurokinin B) and TACR3 mutations produce a distinct neuroendocrine profile characterized by low GnRH pulsatile frequency, low-frequency alpha-subunit pulses, and an elevated FSH/LH ratio; pulsatile GnRH corrected these deficits, confirming that NKB acts upstream of the pituitary at the hypothalamic level.","method":"Cohort sequencing, functional modeling of missense mutant NK3R (Tyr267Asn misfolding), LH pulse profiling, pulsatile GnRH challenge","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (genetics, functional cell assay, endocrine profiling) in a single study","pmids":["22031817"],"is_preprint":false},{"year":2011,"finding":"In the male mouse arcuate nucleus, NKB (encoded by Tac2, the rodent ortholog) is coexpressed with kisspeptin and dynorphin in KNDy neurons; senktide (NK3R agonist) activates KNDy neurons (which express Tacr3) but has no direct effect on GnRH neurons, establishing NKB as an auto-feedback signal within KNDy neurons to generate pulsatile kisspeptin/GnRH secretion.","method":"In situ hybridization for mRNA coexpression, electrophysiology (senktide stimulation of KNDy vs GnRH neurons), LH secretion assays","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (mRNA colocalization, electrophysiology, hormone assays) demonstrating direct circuit mechanism","pmids":["21914775"],"is_preprint":false},{"year":2014,"finding":"The Tac2 gene product NKB, acting through the NK3 receptor (Nk3R), is required for fear memory consolidation in the centromedial amygdala (CeM); Tac2 is colocalized with GAD65 and CaMKIIα neurons in CeM, lentiviral Tac2 overexpression enhances fear consolidation, and this effect is blocked by the NK3R antagonist osanetant.","method":"Lentiviral overexpression, DREADDs-based chemogenetic silencing, NK3R antagonist (osanetant) blockade, fear conditioning behavioral assays, immunofluorescence colocalization","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal gain- and loss-of-function approaches with defined molecular and behavioral readouts","pmids":["24976214"],"is_preprint":false},{"year":2009,"finding":"The human TAC3 gene promoter is directly bound and regulated by Neuron Restrictive Silencing Factor (NRSF/REST) and its truncated isoform sNRSF, leading to increased TAC3 expression; chromatin immunoprecipitation (ChIP) confirmed direct NRSF binding to the NKB promoter in vivo, and the anticonvulsant carbamazepine diminished this induction.","method":"ChIP (chromatin immunoprecipitation), reporter gene assay, RT-PCR of endogenous TAC3 expression","journal":"Neuropeptides","confidence":"High","confidence_rationale":"Tier 1/2 — direct in vivo ChIP evidence of transcription factor binding, combined with reporter assay and endogenous gene expression data","pmids":["19539370"],"is_preprint":false},{"year":2018,"finding":"NKB/NK3R signaling in the posterodorsal medial amygdala (MePD) induces LH release in a kisspeptin-independent manner; chemogenetic (DREADD) activation of MePD Kiss1 neurons also induces LH release, but NKB stimulation of LH in the MePD is independent of Kiss1 neurons, demonstrating two distinct neuronal circuits in the MePD regulating reproductive function.","method":"Chemogenetic (DREADD) activation of cell-type-specific neuronal populations, NK3R agonist stereotaxic injection, LH measurement, genetic Kiss1r knockout comparison","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific chemogenetics with genetic controls provides clean circuit-level dissection","pmids":["30565563"],"is_preprint":false},{"year":2012,"finding":"In zebrafish (Danio rerio), TAC3 encodes two precursors (TAC3a and TAC3b) producing four NKB-like peptides; transcription reporter assays in eukaryotic cells showed that these NKB peptides activate TACR3 downstream signaling, establishing functional conservation of the TAC3/TACR3 system in teleosts.","method":"cDNA cloning, genomic synteny/phylogenetic analysis, transcription reporter assays in cultured cells","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 for functional assay, but single lab; establishes receptor specificity of TAC3 products in a non-mammalian vertebrate","pmids":["22580006"],"is_preprint":false},{"year":2014,"finding":"In carp pituitary cells, NKB (TAC3 product) stimulates prolactin (PRL) and somatolactin-α (SLα) secretion and gene expression via NK2 and NK3 receptors respectively, through adenylate cyclase/cAMP/PKA, phospholipase C/IP3/PKC, and Ca2+/CaM/CaMKII signaling cascades, without affecting LH.","method":"Primary pituitary cell culture, receptor-selective agonist/antagonist treatments, signaling pathway inhibitors, mRNA/protein expression assays","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple signaling pathway dissections in primary cells, single lab fish model","pmids":["24971612"],"is_preprint":false},{"year":1993,"finding":"Chimeric NK1/NK3 receptor studies identified that multiple transmembrane domains contribute to tachykinin peptide binding selectivity; neurokinin B (NK3 preferred ligand) binding is most sensitive to exchange of the carboxyl-terminal transmembrane segments, while the NK3-selective agonist senktide requires transmembrane segments III and IV from the NK3 receptor.","method":"Chimeric receptor construction, stable transfection, competition binding studies","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — systematic chimeric receptor mutagenesis with binding studies defining molecular determinants of ligand selectivity","pmids":["7681831"],"is_preprint":false},{"year":1994,"finding":"Species-selective binding of SR 48968 to human vs. rat NK3 receptor was mapped to two residues in the second transmembrane segment (Met134 and Ala146 in human); human/rat chimeric NK3 receptors and single point mutants (V121M and G133A in rat) confirmed these residues collectively account for the species difference in affinity.","method":"Chimeric receptor construction, point mutagenesis, radioligand binding in transfected CHO cells","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — site-directed mutagenesis with binding assays identifying specific residues responsible for pharmacological difference","pmids":["8117303"],"is_preprint":false},{"year":1998,"finding":"A naturally occurring bis-His zinc-binding site in transmembrane segment V (positions V:01 and V:05) of the NK3A receptor has a positive modulatory effect on neurokinin B binding and function; Zn2+ enhanced [MePhe7]NKB binding to ~150% and potentiated NKB signaling, an effect abolished by Ala-substitution of HisV:01.","method":"Site-directed mutagenesis (Ala substitution of HisV:01), radioligand binding, functional assays with ZnCl2","journal":"FEBS letters","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis combined with pharmacological assays identifying an endogenous modulatory site","pmids":["9849872"],"is_preprint":false},{"year":1998,"finding":"NK3R stimulation in the guinea-pig locus coeruleus increases firing rate of noradrenergic neurons; in vivo microdialysis confirmed that NK3R activation (senktide) increases norepinephrine release in the medial prefrontal cortex, effects blocked by SR 142801 but not its inactive enantiomer SR 142806.","method":"Electrophysiology (slice recording), in vivo microdialysis, behavioral assays, pharmacological antagonism","journal":"Neuroscience","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal in vitro and in vivo methods demonstrating NK3R-mediated noradrenergic activation","pmids":["8865192"],"is_preprint":false},{"year":1998,"finding":"NK3R activation (senktide) in the guinea-pig substantia nigra and ventral tegmental area markedly enhances dopamine release in striatum, nucleus accumbens, and prefrontal cortex; NK3R activation in the septal area enhances acetylcholine release in hippocampus; both effects are dose-dependently blocked by SR142801 but not its inactive enantiomer.","method":"In vivo microdialysis with selective NK3R agonist (senktide) and antagonist (SR142801), regional brain stereotaxic injection","journal":"Neuropeptides","confidence":"High","confidence_rationale":"Tier 2 — in vivo microdialysis with pharmacological validation using stereoselective antagonist pair","pmids":["9845011"],"is_preprint":false},{"year":1994,"finding":"NK3R stimulation by senktide in guinea-pig colon circular muscle produces NANC relaxation and membrane hyperpolarization primarily through nitric oxide release, as demonstrated by complete blockade with the NO synthase inhibitor L-NOARG (reversed by L-arginine); this effect is tetrodotoxin-sensitive and omega-conotoxin-insensitive, indicating neuronal NK3R-mediated NO release not requiring N-type Ca2+ channels.","method":"Isolated organ bath pharmacology, electrophysiology (sucrose gap), pharmacological dissection with L-NOARG, tetrodotoxin, omega-conotoxin","journal":"Regulatory peptides","confidence":"High","confidence_rationale":"Tier 1/2 — in vitro tissue assay with multiple pharmacological tools defining NO as the mediator","pmids":["7531357"],"is_preprint":false},{"year":1995,"finding":"In rat mesenteric artery, NK3R activation (senktide) produces endothelium-dependent vasorelaxation mediated by nitric oxide; this was blocked by L-NOARG (NO synthase inhibitor) and by SR 142801 (selective NK3R antagonist) but not by NK1 or NK2 antagonists.","method":"Isolated vessel pharmacology, endothelium removal, NO synthase inhibition, selective receptor antagonists","journal":"British journal of pharmacology","confidence":"High","confidence_rationale":"Tier 1/2 — in vitro vascular assay with receptor-selective pharmacology and mechanistic dissection of NO pathway","pmids":["8680725"],"is_preprint":false},{"year":1996,"finding":"NK3R activation by senktide in mesencephalic dopamine neuron cultures increases spontaneous [3H]dopamine release and intracellular Ca2+ in a Ca2+-dependent, tetrodotoxin-resistant (direct) manner; effects blocked by NK3R antagonist SR142801 but not NK1 or NK2 antagonists, and pre-treatment with the DA neurotoxin MPP+ abolished senktide-responsive Ca2+ elevations, confirming the response is in DA neurons.","method":"Primary mesencephalic cell cultures, [3H]DA release assay, fluo-3 Ca2+ imaging, pharmacological dissection, MPP+ neurotoxin pretreatment","journal":"The European journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal biochemical and imaging methods in primary neurons with rigorous pharmacological controls","pmids":["9081631"],"is_preprint":false},{"year":2008,"finding":"Chronic L-DOPA treatment in the 6-OHDA rat model of Parkinson's disease increases striatal NKB expression (TAC3/Tac2 product) in the dopamine-depleted hemisphere; NK3R activation (senktide) increases dopamine release (amperometry) and phosphorylation of tyrosine hydroxylase at Ser19 (CaMKII site) and CaMKII at Thr286 in striatal slices, effects blocked by NK3R antagonist SB222200; combined NK3R antagonism with L-DOPA increases contralateral rotations, indicating NKB/NK3R exerts feedback inhibition on L-DOPA actions.","method":"6-OHDA lesion rat model, in situ hybridization, pharmacological treatments, amperometry, phosphoprotein immunoblotting, behavioral rotometry","journal":"Neuropharmacology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (biochemistry, amperometry, behavior) in a validated disease model","pmids":["18423776"],"is_preprint":false},{"year":2005,"finding":"NK3R agonist-induced internalization of the NK3R on vasopressin neurons in the hypothalamic paraventricular nucleus (PVN) was demonstrated in vivo; senktide injection caused translocation of NK3R immunoreactivity from the plasma membrane to cytoplasm (internalization), which was blocked by NK3R antagonist SB-222200 that also blocked senktide-induced vasopressin release; hypertonic saline similarly caused NK3R internalization on VP neurons.","method":"In vivo stereotaxic injection, immunohistochemistry to track NK3R subcellular localization, VP radioimmunoassay, NK3R antagonist pretreatment","journal":"American journal of physiology. Regulatory, integrative and comparative physiology","confidence":"Medium","confidence_rationale":"Tier 2 — ligand-induced receptor internalization as functional readout combined with VP secretion, single lab","pmids":["16357093"],"is_preprint":false},{"year":2000,"finding":"NK3R and NK1R in rat myenteric neurons undergo independent, agonist-induced endocytosis: selective NK3R agonist senktide triggers NK3R endocytosis without affecting NK1R, and this is blocked by NK3R antagonist SR-142801 but not NK1R antagonist; monensin (recycling blocker) accumulates NK1R but not NK3R in cytoplasm, indicating different recycling mechanisms for the two receptor subtypes.","method":"Immunohistochemistry tracking receptor subcellular distribution, selective agonists/antagonists, pharmacological recycling inhibitor (monensin)","journal":"Neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — direct subcellular localization tracking with receptor-selective pharmacology, single lab","pmids":["10996469"],"is_preprint":false},{"year":1992,"finding":"NK3R (neurokinin B receptor) activation in rat paraventricular nucleus (PVN) increases blood pressure, an effect blocked by vasopressin V1 receptor antagonist, establishing that NK3R stimulation in the PVN triggers vasopressin release from the pituitary to cause pressor responses.","method":"Stereotaxic microinjection of senktide into PVN, blood pressure measurement, V1 receptor antagonist pretreatment","journal":"Brain research","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo pharmacological epistasis placing NK3R upstream of vasopressin release, single lab","pmids":["1281741"],"is_preprint":false},{"year":2011,"finding":"TACR3 promoter DNA methylation at a specific CpG site is decreased in marmoset monkeys after repeated cocaine administration in a conditioned place preference paradigm, identifying TACR3 as a locus for cocaine-induced epigenetic modification.","method":"Bisulfite pyrosequencing of TACR3 promoter CpG sites in brain tissue from conditioned place preference paradigm marmosets","journal":"Addiction biology","confidence":"Low","confidence_rationale":"Tier 3 — single lab, single method (DNA methylation), no direct functional demonstration of altered TAC3/TACR3 expression or signaling","pmids":["22070124"],"is_preprint":false},{"year":2014,"finding":"NKB (TAC3 product) and NK3R are expressed and functionally active in human ovarian granulosa cells; kisspeptin increases intracellular Ca2+ in granulosa cells while NKB inhibits kisspeptin-induced Ca2+ mobilization, an effect partially mediated by NK3R and blocked by a cocktail of NK1/NK2/NK3 receptor antagonists.","method":"RT-PCR, immunocytochemistry, western blot, intracellular Ca2+ measurement (live imaging), tachykinin receptor antagonist pharmacology","journal":"Human reproduction","confidence":"Medium","confidence_rationale":"Tier 2/3 — multiple expression and functional methods, but functional signal partially receptor-independent; single lab","pmids":["25316443"],"is_preprint":false}],"current_model":"TAC3 encodes neurokinin B (NKB), which acts primarily through its cognate G protein-coupled receptor NK3R (TACR3) to regulate hypothalamic GnRH pulsatile secretion via an auto-feedback loop in KNDy (kisspeptin/NKB/dynorphin) arcuate neurons, with loss-of-function mutations in TAC3 causing normosmic congenital hypogonadotropic hypogonadism in humans; beyond reproduction, NKB/NK3R signaling modulates dopaminergic and noradrenergic neurotransmission, fear memory consolidation in the centromedial amygdala, vasopressin release from the hypothalamic PVN, and peripheral functions including nitric oxide-mediated smooth muscle relaxation, with the TAC3 gene itself regulated transcriptionally by NRSF/REST-family factors."},"narrative":{"teleology":[{"year":1992,"claim":"Early work established that NKB's receptor NK3R is functionally active in the hypothalamic PVN, where it triggers vasopressin-dependent cardiovascular responses, revealing a central neuroendocrine role for the TAC3/NK3R axis beyond classical peripheral tachykinin functions.","evidence":"Stereotaxic senktide microinjection into rat PVN with blood pressure recording and V1 receptor antagonist blockade","pmids":["1281741"],"confidence":"Medium","gaps":["Single lab; vasopressin release was inferred from V1 antagonist blockade rather than measured directly","Endogenous NKB involvement not demonstrated (only exogenous agonist)","Downstream intracellular signaling not characterized"]},{"year":1993,"claim":"Chimeric NK1/NK3 receptor studies defined the molecular determinants of NKB binding selectivity, showing that carboxyl-terminal transmembrane domains are critical for NKB recognition while transmembrane segments III–IV govern senktide selectivity, providing the first structural framework for how NK3R distinguishes NKB from other tachykinins.","evidence":"Chimeric receptor construction with stable transfection and competition radioligand binding","pmids":["7681831","8117303"],"confidence":"High","gaps":["No crystal structure or cryo-EM confirmation of binding poses","Species-selective residues mapped but broader structure–function of full-length receptor unknown"]},{"year":1994,"claim":"NK3R activation was shown to mediate nitric oxide-dependent NANC relaxation in gut smooth muscle and endothelium-dependent vasorelaxation in mesenteric artery, establishing NKB/NK3R as a peripheral regulator of smooth muscle tone through an NO signaling pathway.","evidence":"Isolated organ bath pharmacology with NO synthase inhibitors, endothelium removal, and selective NK3R antagonists in guinea-pig colon and rat mesenteric artery","pmids":["7531357","8680725"],"confidence":"High","gaps":["Source of endogenous NKB in these tissues not identified","In vivo relevance of NKB-mediated vasodilation not demonstrated"]},{"year":1996,"claim":"NKB/NK3R signaling was demonstrated to directly stimulate dopamine release and intracellular Ca²⁺ elevation in mesencephalic dopamine neurons, and to enhance noradrenergic and cholinergic transmission in vivo, revealing NKB as a modulator of multiple monoaminergic and cholinergic systems.","evidence":"Primary mesencephalic cultures with [³H]DA release and Ca²⁺ imaging; in vivo microdialysis in guinea-pig locus coeruleus, substantia nigra, VTA, and septal area with senktide and stereoselective NK3R antagonists","pmids":["9081631","8865192","9845011"],"confidence":"High","gaps":["Circuit-level connectivity between NKB-expressing neurons and dopaminergic/noradrenergic targets not mapped","Physiological conditions that trigger endogenous NKB release onto these neurons remain unclear"]},{"year":1998,"claim":"A zinc-binding site in NK3R transmembrane segment V was identified as a positive allosteric modulator of NKB binding and signaling, revealing an endogenous modulatory mechanism for NK3R pharmacology.","evidence":"Site-directed mutagenesis of HisV:01 with radioligand binding and functional assays in the presence of ZnCl₂","pmids":["9849872"],"confidence":"High","gaps":["Physiological relevance of zinc modulation at synaptic concentrations not established","No structural confirmation of the zinc coordination geometry"]},{"year":2005,"claim":"NK3R activation on hypothalamic PVN vasopressin neurons was shown to trigger receptor internalization in vivo, providing a cellular mechanism for signal termination and confirming that NKB/NK3R drives vasopressin secretion through direct action on VP neurons.","evidence":"In vivo stereotaxic injection with immunohistochemical tracking of NK3R subcellular redistribution and VP radioimmunoassay","pmids":["16357093"],"confidence":"Medium","gaps":["Single lab observation","Kinetics and recycling pathway of internalized NK3R on VP neurons not characterized","Contribution of endogenous NKB versus pharmacological agonist dosing unclear"]},{"year":2008,"claim":"In a Parkinson's disease model, chronic L-DOPA upregulated striatal NKB expression, and NK3R activation stimulated dopamine release via CaMKII/tyrosine hydroxylase phosphorylation, while NK3R blockade enhanced L-DOPA behavioral effects — positioning NKB/NK3R as a feedback inhibitor of dopaminergic signaling relevant to L-DOPA therapy.","evidence":"6-OHDA rat model with in situ hybridization, amperometry in striatal slices, phosphoprotein immunoblotting, and behavioral rotometry","pmids":["18423776"],"confidence":"High","gaps":["Mechanism of NKB upregulation by L-DOPA not defined","Translational relevance to human PD not tested"]},{"year":2009,"claim":"NRSF/REST was identified as a direct transcriptional regulator of TAC3, with ChIP confirming binding to the NKB promoter and carbamazepine reducing NRSF-driven TAC3 induction, establishing a transcriptional control mechanism for NKB expression.","evidence":"Chromatin immunoprecipitation, reporter gene assays, and RT-PCR of endogenous TAC3","pmids":["19539370"],"confidence":"High","gaps":["Physiological signals that modulate NRSF occupancy at TAC3 promoter in neurons not identified","Whether sNRSF isoform has distinct regulatory effects in vivo is unknown"]},{"year":2010,"claim":"Human genetic evidence established that TAC3 loss-of-function mutations cause normosmic congenital hypogonadotropic hypogonadism by impairing hypothalamic GnRH pulse generation, placing NKB as essential for reproductive neuroendocrine function.","evidence":"Homozygous TAC3 splice-site mutations in CHH kindreds; hormonal profiling and pulsatile GnRH rescue of LH secretion and fertility","pmids":["20194706","22031817"],"confidence":"High","gaps":["Genotype–phenotype variability (some patients show partial reversal) not mechanistically explained","Whether heterozygous carriers have subtle reproductive phenotypes is unclear"]},{"year":2011,"claim":"The KNDy neuron model was experimentally validated: NKB is coexpressed with kisspeptin and dynorphin in arcuate neurons, and NK3R agonism directly activates KNDy neurons but not GnRH neurons, establishing NKB as an auto-feedback signal that shapes pulsatile kisspeptin/GnRH output.","evidence":"In situ hybridization for mRNA colocalization, electrophysiology of KNDy vs. GnRH neurons in mouse brain slices, LH secretion assays","pmids":["21914775"],"confidence":"High","gaps":["Relative contributions of NKB versus dynorphin in setting pulse frequency not quantified","Whether NKB acts solely in autocrine mode or also on neighboring KNDy neurons is unresolved"]},{"year":2014,"claim":"NKB/NK3R signaling was shown to be necessary and sufficient for fear memory consolidation in the centromedial amygdala, extending TAC3 function beyond neuroendocrine regulation to emotional memory circuits.","evidence":"Lentiviral Tac2 overexpression, DREADD-based chemogenetic silencing, NK3R antagonist osanetant, and fear conditioning behavioral assays in mice","pmids":["24976214"],"confidence":"High","gaps":["Downstream molecular targets of NK3R in CeM fear circuits not identified","Relevance to human PTSD or anxiety disorders not tested"]},{"year":2018,"claim":"NKB/NK3R signaling in the medial amygdala was found to drive LH release through a kisspeptin-independent pathway, revealing a second, extrahypothalamic reproductive circuit distinct from the canonical arcuate KNDy mechanism.","evidence":"Cell-type-specific DREADD activation, NK3R agonist stereotaxic injection, LH measurement, and Kiss1r knockout comparison in mice","pmids":["30565563"],"confidence":"High","gaps":["Identity of the downstream relay neurons from MePD to GnRH neurons is unknown","Physiological conditions that engage the MePD NKB pathway versus the arcuate KNDy pathway are not defined"]},{"year":null,"claim":"Key unresolved questions include: how NKB pulse dynamics are translated into GnRH pulse frequency at the molecular level, the identity of downstream effectors mediating NK3R actions in fear and dopaminergic circuits, and the physiological significance of peripheral NKB/NK3R signaling (ovarian, vascular) in humans.","evidence":"","pmids":[],"confidence":"Low","gaps":["No integrated model connecting NKB pulse generation, kisspeptin release, and GnRH neuron activation at single-cell resolution","Structural basis of NKB–NK3R interaction remains without cryo-EM or crystal structure","Relative contributions of autocrine vs. paracrine NKB signaling within KNDy network are not quantified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,1,2,3,8]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,2,3,13,14]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,3,7,11,12,15]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[3,11,12,15,16]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,1,2,5]}],"complexes":[],"partners":["TACR3","KISS1","PDYN","REST"],"other_free_text":[]},"mechanistic_narrative":"TAC3 encodes neurokinin B (NKB), a tachykinin neuropeptide that signals through the NK3 receptor (TACR3/NK3R) to regulate diverse neuroendocrine and peripheral functions. In the hypothalamus, NKB operates as an autocrine/paracrine signal within arcuate KNDy (kisspeptin/NKB/dynorphin) neurons to drive pulsatile GnRH secretion, and loss-of-function mutations in TAC3 cause normosmic congenital hypogonadotropic hypogonadism in humans [PMID:20194706, PMID:21914775]. Beyond reproduction, NKB/NK3R signaling directly stimulates dopamine release from mesencephalic neurons, enhances noradrenergic transmission in the locus coeruleus, promotes vasopressin release from hypothalamic paraventricular nucleus neurons, mediates fear memory consolidation in the centromedial amygdala, and induces nitric oxide-dependent smooth muscle relaxation in gut and vasculature [PMID:9081631, PMID:8865192, PMID:1281741, PMID:24976214, PMID:7531357, PMID:8680725]. TAC3 transcription is directly regulated by NRSF/REST binding to its promoter [PMID:19539370]."},"prefetch_data":{"uniprot":{"accession":"Q9UHF0","full_name":"Tachykinin-3","aliases":["ZNEUROK1"],"length_aa":121,"mass_kda":13.4,"function":"Tachykinins are active peptides which excite neurons, evoke behavioral responses, are potent vasodilators and secretagogues, and contract (directly or indirectly) many smooth muscles Is a ligand for TACR3, and triggers G protein-coupled receptor signaling via activation of G(q) and phosphatidylinositol hydrolysis by phospholipase C (PubMed:37391393). Binding to TACR3 also triggers signaling via activation of adenylate cyclase activity which results in increased intracellular levels of cyclic AMP (cAMP) (By similarity). Is a critical central regulator of gonadal function (By similarity) (PubMed:19079066)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/Q9UHF0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/TAC3","classification":"Not Classified","n_dependent_lines":4,"n_total_lines":1208,"dependency_fraction":0.0033112582781456954},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/TAC3","total_profiled":1310},"omim":[{"mim_id":"614840","title":"HYPOGONADOTROPIC HYPOGONADISM 11 WITH OR WITHOUT ANOSMIA; HH11","url":"https://www.omim.org/entry/614840"},{"mim_id":"614839","title":"HYPOGONADOTROPIC HYPOGONADISM 10 WITH OR WITHOUT ANOSMIA; HH10","url":"https://www.omim.org/entry/614839"},{"mim_id":"603856","title":"MAKORIN 3; MKRN3","url":"https://www.omim.org/entry/603856"},{"mim_id":"162332","title":"TACHYKININ RECEPTOR 3; TACR3","url":"https://www.omim.org/entry/162332"},{"mim_id":"162330","title":"TACHYKININ 3; TAC3","url":"https://www.omim.org/entry/162330"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Vesicles","reliability":"Approved"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"placenta","ntpm":404.6}],"url":"https://www.proteinatlas.org/search/TAC3"},"hgnc":{"alias_symbol":["ZNEUROK1","NKB","NK3","LncZBTB39-1:2","LncZBTB39"],"prev_symbol":["NKNB"]},"alphafold":{"accession":"Q9UHF0","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UHF0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UHF0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9UHF0-F1-predicted_aligned_error_v6.png","plddt_mean":64.88},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=TAC3","jax_strain_url":"https://www.jax.org/strain/search?query=TAC3"},"sequence":{"accession":"Q9UHF0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9UHF0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9UHF0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9UHF0"}},"corpus_meta":[{"pmid":"21914775","id":"PMC_21914775","title":"Regulation of NKB pathways and their roles in the control of Kiss1 neurons in the arcuate nucleus of the male mouse.","date":"2011","source":"Endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/21914775","citation_count":190,"is_preprint":false},{"pmid":"8824334","id":"PMC_8824334","title":"Characterization of antisera specific to NK1, NK2, and NK3 neurokinin receptors and their utilization to localize receptors in the rat gastrointestinal tract.","date":"1996","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/8824334","citation_count":189,"is_preprint":false},{"pmid":"20194706","id":"PMC_20194706","title":"TAC3 and TACR3 defects cause hypothalamic congenital hypogonadotropic hypogonadism in humans.","date":"2010","source":"The Journal of clinical endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/20194706","citation_count":181,"is_preprint":false},{"pmid":"7830490","id":"PMC_7830490","title":"SR 142801, the first potent non-peptide antagonist of the tachykinin NK3 receptor.","date":"1995","source":"Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/7830490","citation_count":169,"is_preprint":false},{"pmid":"8788251","id":"PMC_8788251","title":"Localization of the neuromedin K receptor (NK3) in the central nervous system of the rat.","date":"1996","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/8788251","citation_count":166,"is_preprint":false},{"pmid":"10559189","id":"PMC_10559189","title":"The homeodomain protein NK-3 recruits Groucho and a histone deacetylase complex to repress transcription.","date":"1999","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10559189","citation_count":142,"is_preprint":false},{"pmid":"19755669","id":"PMC_19755669","title":"Sex differences in the regulation of Kiss1/NKB neurons in juvenile mice: implications for the timing of puberty.","date":"2009","source":"American journal of physiology. 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immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/30870678","citation_count":20,"is_preprint":false},{"pmid":"8751080","id":"PMC_8751080","title":"Effect of SR 142801 on nitric oxide-dependent and independent responses to tachykinin NK3 receptor agonists in isolated guinea-pig colon.","date":"1995","source":"Naunyn-Schmiedeberg's archives of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/8751080","citation_count":20,"is_preprint":false},{"pmid":"9017229","id":"PMC_9017229","title":"Antidiuretic action of tachykinin NK-3 receptor in the rat paraventricular nucleus.","date":"1996","source":"Brain research","url":"https://pubmed.ncbi.nlm.nih.gov/9017229","citation_count":20,"is_preprint":false},{"pmid":"18423776","id":"PMC_18423776","title":"Neurokinin B/NK3 receptors exert feedback inhibition on L-DOPA actions in the 6-OHDA lesion rat model of Parkinson's 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via myenteric neurons and tachykinin NK2/NK3 receptors.","date":"2004","source":"British journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/14718265","citation_count":17,"is_preprint":false},{"pmid":"21376585","id":"PMC_21376585","title":"Discovery of 3-aryl-5-acylpiperazinyl-pyrazoles as antagonists to the NK3 receptor.","date":"2011","source":"Bioorganic & medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/21376585","citation_count":17,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":55842,"output_tokens":5473,"usd":0.124811},"stage2":{"model":"claude-opus-4-6","input_tokens":9004,"output_tokens":3239,"usd":0.188993},"total_usd":0.313804,"stage1_batch_id":"msgbatch_01RPbVc9PDH9zQmYK5Hs6srm","stage2_batch_id":"msgbatch_01JVbVLzeKN2yVrsGp3zC8aM","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2010,\n      \"finding\": \"Loss-of-function mutations in TAC3 (neurokinin B gene) cause normosmic congenital hypogonadotropic hypogonadism (CHH) in humans by impairing hypothalamic GnRH pulsatile release; pulsatile GnRH administration restored LH secretion and fertility, establishing the hypothalamic origin of the gonadotropin deficiency.\",\n      \"method\": \"Human genetics (homozygous splice-site mutations in TAC3 identified in CHH patients), hormonal profiling, pulsatile GnRH challenge\",\n      \"journal\": \"The Journal of clinical endocrinology and metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — loss-of-function human genetics with defined neuroendocrine phenotype, replicated across multiple unrelated kindreds\",\n      \"pmids\": [\"20194706\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TAC3 mutations (splice-site deletion of neurokinin B) and TACR3 mutations produce a distinct neuroendocrine profile characterized by low GnRH pulsatile frequency, low-frequency alpha-subunit pulses, and an elevated FSH/LH ratio; pulsatile GnRH corrected these deficits, confirming that NKB acts upstream of the pituitary at the hypothalamic level.\",\n      \"method\": \"Cohort sequencing, functional modeling of missense mutant NK3R (Tyr267Asn misfolding), LH pulse profiling, pulsatile GnRH challenge\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (genetics, functional cell assay, endocrine profiling) in a single study\",\n      \"pmids\": [\"22031817\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"In the male mouse arcuate nucleus, NKB (encoded by Tac2, the rodent ortholog) is coexpressed with kisspeptin and dynorphin in KNDy neurons; senktide (NK3R agonist) activates KNDy neurons (which express Tacr3) but has no direct effect on GnRH neurons, establishing NKB as an auto-feedback signal within KNDy neurons to generate pulsatile kisspeptin/GnRH secretion.\",\n      \"method\": \"In situ hybridization for mRNA coexpression, electrophysiology (senktide stimulation of KNDy vs GnRH neurons), LH secretion assays\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (mRNA colocalization, electrophysiology, hormone assays) demonstrating direct circuit mechanism\",\n      \"pmids\": [\"21914775\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The Tac2 gene product NKB, acting through the NK3 receptor (Nk3R), is required for fear memory consolidation in the centromedial amygdala (CeM); Tac2 is colocalized with GAD65 and CaMKIIα neurons in CeM, lentiviral Tac2 overexpression enhances fear consolidation, and this effect is blocked by the NK3R antagonist osanetant.\",\n      \"method\": \"Lentiviral overexpression, DREADDs-based chemogenetic silencing, NK3R antagonist (osanetant) blockade, fear conditioning behavioral assays, immunofluorescence colocalization\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal gain- and loss-of-function approaches with defined molecular and behavioral readouts\",\n      \"pmids\": [\"24976214\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"The human TAC3 gene promoter is directly bound and regulated by Neuron Restrictive Silencing Factor (NRSF/REST) and its truncated isoform sNRSF, leading to increased TAC3 expression; chromatin immunoprecipitation (ChIP) confirmed direct NRSF binding to the NKB promoter in vivo, and the anticonvulsant carbamazepine diminished this induction.\",\n      \"method\": \"ChIP (chromatin immunoprecipitation), reporter gene assay, RT-PCR of endogenous TAC3 expression\",\n      \"journal\": \"Neuropeptides\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — direct in vivo ChIP evidence of transcription factor binding, combined with reporter assay and endogenous gene expression data\",\n      \"pmids\": [\"19539370\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"NKB/NK3R signaling in the posterodorsal medial amygdala (MePD) induces LH release in a kisspeptin-independent manner; chemogenetic (DREADD) activation of MePD Kiss1 neurons also induces LH release, but NKB stimulation of LH in the MePD is independent of Kiss1 neurons, demonstrating two distinct neuronal circuits in the MePD regulating reproductive function.\",\n      \"method\": \"Chemogenetic (DREADD) activation of cell-type-specific neuronal populations, NK3R agonist stereotaxic injection, LH measurement, genetic Kiss1r knockout comparison\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific chemogenetics with genetic controls provides clean circuit-level dissection\",\n      \"pmids\": [\"30565563\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"In zebrafish (Danio rerio), TAC3 encodes two precursors (TAC3a and TAC3b) producing four NKB-like peptides; transcription reporter assays in eukaryotic cells showed that these NKB peptides activate TACR3 downstream signaling, establishing functional conservation of the TAC3/TACR3 system in teleosts.\",\n      \"method\": \"cDNA cloning, genomic synteny/phylogenetic analysis, transcription reporter assays in cultured cells\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 for functional assay, but single lab; establishes receptor specificity of TAC3 products in a non-mammalian vertebrate\",\n      \"pmids\": [\"22580006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"In carp pituitary cells, NKB (TAC3 product) stimulates prolactin (PRL) and somatolactin-α (SLα) secretion and gene expression via NK2 and NK3 receptors respectively, through adenylate cyclase/cAMP/PKA, phospholipase C/IP3/PKC, and Ca2+/CaM/CaMKII signaling cascades, without affecting LH.\",\n      \"method\": \"Primary pituitary cell culture, receptor-selective agonist/antagonist treatments, signaling pathway inhibitors, mRNA/protein expression assays\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple signaling pathway dissections in primary cells, single lab fish model\",\n      \"pmids\": [\"24971612\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"Chimeric NK1/NK3 receptor studies identified that multiple transmembrane domains contribute to tachykinin peptide binding selectivity; neurokinin B (NK3 preferred ligand) binding is most sensitive to exchange of the carboxyl-terminal transmembrane segments, while the NK3-selective agonist senktide requires transmembrane segments III and IV from the NK3 receptor.\",\n      \"method\": \"Chimeric receptor construction, stable transfection, competition binding studies\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic chimeric receptor mutagenesis with binding studies defining molecular determinants of ligand selectivity\",\n      \"pmids\": [\"7681831\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"Species-selective binding of SR 48968 to human vs. rat NK3 receptor was mapped to two residues in the second transmembrane segment (Met134 and Ala146 in human); human/rat chimeric NK3 receptors and single point mutants (V121M and G133A in rat) confirmed these residues collectively account for the species difference in affinity.\",\n      \"method\": \"Chimeric receptor construction, point mutagenesis, radioligand binding in transfected CHO cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — site-directed mutagenesis with binding assays identifying specific residues responsible for pharmacological difference\",\n      \"pmids\": [\"8117303\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"A naturally occurring bis-His zinc-binding site in transmembrane segment V (positions V:01 and V:05) of the NK3A receptor has a positive modulatory effect on neurokinin B binding and function; Zn2+ enhanced [MePhe7]NKB binding to ~150% and potentiated NKB signaling, an effect abolished by Ala-substitution of HisV:01.\",\n      \"method\": \"Site-directed mutagenesis (Ala substitution of HisV:01), radioligand binding, functional assays with ZnCl2\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis combined with pharmacological assays identifying an endogenous modulatory site\",\n      \"pmids\": [\"9849872\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"NK3R stimulation in the guinea-pig locus coeruleus increases firing rate of noradrenergic neurons; in vivo microdialysis confirmed that NK3R activation (senktide) increases norepinephrine release in the medial prefrontal cortex, effects blocked by SR 142801 but not its inactive enantiomer SR 142806.\",\n      \"method\": \"Electrophysiology (slice recording), in vivo microdialysis, behavioral assays, pharmacological antagonism\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal in vitro and in vivo methods demonstrating NK3R-mediated noradrenergic activation\",\n      \"pmids\": [\"8865192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"NK3R activation (senktide) in the guinea-pig substantia nigra and ventral tegmental area markedly enhances dopamine release in striatum, nucleus accumbens, and prefrontal cortex; NK3R activation in the septal area enhances acetylcholine release in hippocampus; both effects are dose-dependently blocked by SR142801 but not its inactive enantiomer.\",\n      \"method\": \"In vivo microdialysis with selective NK3R agonist (senktide) and antagonist (SR142801), regional brain stereotaxic injection\",\n      \"journal\": \"Neuropeptides\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — in vivo microdialysis with pharmacological validation using stereoselective antagonist pair\",\n      \"pmids\": [\"9845011\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"NK3R stimulation by senktide in guinea-pig colon circular muscle produces NANC relaxation and membrane hyperpolarization primarily through nitric oxide release, as demonstrated by complete blockade with the NO synthase inhibitor L-NOARG (reversed by L-arginine); this effect is tetrodotoxin-sensitive and omega-conotoxin-insensitive, indicating neuronal NK3R-mediated NO release not requiring N-type Ca2+ channels.\",\n      \"method\": \"Isolated organ bath pharmacology, electrophysiology (sucrose gap), pharmacological dissection with L-NOARG, tetrodotoxin, omega-conotoxin\",\n      \"journal\": \"Regulatory peptides\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — in vitro tissue assay with multiple pharmacological tools defining NO as the mediator\",\n      \"pmids\": [\"7531357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"In rat mesenteric artery, NK3R activation (senktide) produces endothelium-dependent vasorelaxation mediated by nitric oxide; this was blocked by L-NOARG (NO synthase inhibitor) and by SR 142801 (selective NK3R antagonist) but not by NK1 or NK2 antagonists.\",\n      \"method\": \"Isolated vessel pharmacology, endothelium removal, NO synthase inhibition, selective receptor antagonists\",\n      \"journal\": \"British journal of pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1/2 — in vitro vascular assay with receptor-selective pharmacology and mechanistic dissection of NO pathway\",\n      \"pmids\": [\"8680725\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"NK3R activation by senktide in mesencephalic dopamine neuron cultures increases spontaneous [3H]dopamine release and intracellular Ca2+ in a Ca2+-dependent, tetrodotoxin-resistant (direct) manner; effects blocked by NK3R antagonist SR142801 but not NK1 or NK2 antagonists, and pre-treatment with the DA neurotoxin MPP+ abolished senktide-responsive Ca2+ elevations, confirming the response is in DA neurons.\",\n      \"method\": \"Primary mesencephalic cell cultures, [3H]DA release assay, fluo-3 Ca2+ imaging, pharmacological dissection, MPP+ neurotoxin pretreatment\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal biochemical and imaging methods in primary neurons with rigorous pharmacological controls\",\n      \"pmids\": [\"9081631\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Chronic L-DOPA treatment in the 6-OHDA rat model of Parkinson's disease increases striatal NKB expression (TAC3/Tac2 product) in the dopamine-depleted hemisphere; NK3R activation (senktide) increases dopamine release (amperometry) and phosphorylation of tyrosine hydroxylase at Ser19 (CaMKII site) and CaMKII at Thr286 in striatal slices, effects blocked by NK3R antagonist SB222200; combined NK3R antagonism with L-DOPA increases contralateral rotations, indicating NKB/NK3R exerts feedback inhibition on L-DOPA actions.\",\n      \"method\": \"6-OHDA lesion rat model, in situ hybridization, pharmacological treatments, amperometry, phosphoprotein immunoblotting, behavioral rotometry\",\n      \"journal\": \"Neuropharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (biochemistry, amperometry, behavior) in a validated disease model\",\n      \"pmids\": [\"18423776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"NK3R agonist-induced internalization of the NK3R on vasopressin neurons in the hypothalamic paraventricular nucleus (PVN) was demonstrated in vivo; senktide injection caused translocation of NK3R immunoreactivity from the plasma membrane to cytoplasm (internalization), which was blocked by NK3R antagonist SB-222200 that also blocked senktide-induced vasopressin release; hypertonic saline similarly caused NK3R internalization on VP neurons.\",\n      \"method\": \"In vivo stereotaxic injection, immunohistochemistry to track NK3R subcellular localization, VP radioimmunoassay, NK3R antagonist pretreatment\",\n      \"journal\": \"American journal of physiology. Regulatory, integrative and comparative physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — ligand-induced receptor internalization as functional readout combined with VP secretion, single lab\",\n      \"pmids\": [\"16357093\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"NK3R and NK1R in rat myenteric neurons undergo independent, agonist-induced endocytosis: selective NK3R agonist senktide triggers NK3R endocytosis without affecting NK1R, and this is blocked by NK3R antagonist SR-142801 but not NK1R antagonist; monensin (recycling blocker) accumulates NK1R but not NK3R in cytoplasm, indicating different recycling mechanisms for the two receptor subtypes.\",\n      \"method\": \"Immunohistochemistry tracking receptor subcellular distribution, selective agonists/antagonists, pharmacological recycling inhibitor (monensin)\",\n      \"journal\": \"Neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct subcellular localization tracking with receptor-selective pharmacology, single lab\",\n      \"pmids\": [\"10996469\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1992,\n      \"finding\": \"NK3R (neurokinin B receptor) activation in rat paraventricular nucleus (PVN) increases blood pressure, an effect blocked by vasopressin V1 receptor antagonist, establishing that NK3R stimulation in the PVN triggers vasopressin release from the pituitary to cause pressor responses.\",\n      \"method\": \"Stereotaxic microinjection of senktide into PVN, blood pressure measurement, V1 receptor antagonist pretreatment\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo pharmacological epistasis placing NK3R upstream of vasopressin release, single lab\",\n      \"pmids\": [\"1281741\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"TACR3 promoter DNA methylation at a specific CpG site is decreased in marmoset monkeys after repeated cocaine administration in a conditioned place preference paradigm, identifying TACR3 as a locus for cocaine-induced epigenetic modification.\",\n      \"method\": \"Bisulfite pyrosequencing of TACR3 promoter CpG sites in brain tissue from conditioned place preference paradigm marmosets\",\n      \"journal\": \"Addiction biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, single method (DNA methylation), no direct functional demonstration of altered TAC3/TACR3 expression or signaling\",\n      \"pmids\": [\"22070124\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"NKB (TAC3 product) and NK3R are expressed and functionally active in human ovarian granulosa cells; kisspeptin increases intracellular Ca2+ in granulosa cells while NKB inhibits kisspeptin-induced Ca2+ mobilization, an effect partially mediated by NK3R and blocked by a cocktail of NK1/NK2/NK3 receptor antagonists.\",\n      \"method\": \"RT-PCR, immunocytochemistry, western blot, intracellular Ca2+ measurement (live imaging), tachykinin receptor antagonist pharmacology\",\n      \"journal\": \"Human reproduction\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2/3 — multiple expression and functional methods, but functional signal partially receptor-independent; single lab\",\n      \"pmids\": [\"25316443\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"TAC3 encodes neurokinin B (NKB), which acts primarily through its cognate G protein-coupled receptor NK3R (TACR3) to regulate hypothalamic GnRH pulsatile secretion via an auto-feedback loop in KNDy (kisspeptin/NKB/dynorphin) arcuate neurons, with loss-of-function mutations in TAC3 causing normosmic congenital hypogonadotropic hypogonadism in humans; beyond reproduction, NKB/NK3R signaling modulates dopaminergic and noradrenergic neurotransmission, fear memory consolidation in the centromedial amygdala, vasopressin release from the hypothalamic PVN, and peripheral functions including nitric oxide-mediated smooth muscle relaxation, with the TAC3 gene itself regulated transcriptionally by NRSF/REST-family factors.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"TAC3 encodes neurokinin B (NKB), a tachykinin neuropeptide that signals through the NK3 receptor (TACR3/NK3R) to regulate diverse neuroendocrine and peripheral functions. In the hypothalamus, NKB operates as an autocrine/paracrine signal within arcuate KNDy (kisspeptin/NKB/dynorphin) neurons to drive pulsatile GnRH secretion, and loss-of-function mutations in TAC3 cause normosmic congenital hypogonadotropic hypogonadism in humans [PMID:20194706, PMID:21914775]. Beyond reproduction, NKB/NK3R signaling directly stimulates dopamine release from mesencephalic neurons, enhances noradrenergic transmission in the locus coeruleus, promotes vasopressin release from hypothalamic paraventricular nucleus neurons, mediates fear memory consolidation in the centromedial amygdala, and induces nitric oxide-dependent smooth muscle relaxation in gut and vasculature [PMID:9081631, PMID:8865192, PMID:1281741, PMID:24976214, PMID:7531357, PMID:8680725]. TAC3 transcription is directly regulated by NRSF/REST binding to its promoter [PMID:19539370].\",\n  \"teleology\": [\n    {\n      \"year\": 1992,\n      \"claim\": \"Early work established that NKB's receptor NK3R is functionally active in the hypothalamic PVN, where it triggers vasopressin-dependent cardiovascular responses, revealing a central neuroendocrine role for the TAC3/NK3R axis beyond classical peripheral tachykinin functions.\",\n      \"evidence\": \"Stereotaxic senktide microinjection into rat PVN with blood pressure recording and V1 receptor antagonist blockade\",\n      \"pmids\": [\"1281741\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; vasopressin release was inferred from V1 antagonist blockade rather than measured directly\", \"Endogenous NKB involvement not demonstrated (only exogenous agonist)\", \"Downstream intracellular signaling not characterized\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Chimeric NK1/NK3 receptor studies defined the molecular determinants of NKB binding selectivity, showing that carboxyl-terminal transmembrane domains are critical for NKB recognition while transmembrane segments III–IV govern senktide selectivity, providing the first structural framework for how NK3R distinguishes NKB from other tachykinins.\",\n      \"evidence\": \"Chimeric receptor construction with stable transfection and competition radioligand binding\",\n      \"pmids\": [\"7681831\", \"8117303\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal structure or cryo-EM confirmation of binding poses\", \"Species-selective residues mapped but broader structure–function of full-length receptor unknown\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"NK3R activation was shown to mediate nitric oxide-dependent NANC relaxation in gut smooth muscle and endothelium-dependent vasorelaxation in mesenteric artery, establishing NKB/NK3R as a peripheral regulator of smooth muscle tone through an NO signaling pathway.\",\n      \"evidence\": \"Isolated organ bath pharmacology with NO synthase inhibitors, endothelium removal, and selective NK3R antagonists in guinea-pig colon and rat mesenteric artery\",\n      \"pmids\": [\"7531357\", \"8680725\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Source of endogenous NKB in these tissues not identified\", \"In vivo relevance of NKB-mediated vasodilation not demonstrated\"]\n    },\n    {\n      \"year\": 1996,\n      \"claim\": \"NKB/NK3R signaling was demonstrated to directly stimulate dopamine release and intracellular Ca²⁺ elevation in mesencephalic dopamine neurons, and to enhance noradrenergic and cholinergic transmission in vivo, revealing NKB as a modulator of multiple monoaminergic and cholinergic systems.\",\n      \"evidence\": \"Primary mesencephalic cultures with [³H]DA release and Ca²⁺ imaging; in vivo microdialysis in guinea-pig locus coeruleus, substantia nigra, VTA, and septal area with senktide and stereoselective NK3R antagonists\",\n      \"pmids\": [\"9081631\", \"8865192\", \"9845011\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Circuit-level connectivity between NKB-expressing neurons and dopaminergic/noradrenergic targets not mapped\", \"Physiological conditions that trigger endogenous NKB release onto these neurons remain unclear\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"A zinc-binding site in NK3R transmembrane segment V was identified as a positive allosteric modulator of NKB binding and signaling, revealing an endogenous modulatory mechanism for NK3R pharmacology.\",\n      \"evidence\": \"Site-directed mutagenesis of HisV:01 with radioligand binding and functional assays in the presence of ZnCl₂\",\n      \"pmids\": [\"9849872\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological relevance of zinc modulation at synaptic concentrations not established\", \"No structural confirmation of the zinc coordination geometry\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"NK3R activation on hypothalamic PVN vasopressin neurons was shown to trigger receptor internalization in vivo, providing a cellular mechanism for signal termination and confirming that NKB/NK3R drives vasopressin secretion through direct action on VP neurons.\",\n      \"evidence\": \"In vivo stereotaxic injection with immunohistochemical tracking of NK3R subcellular redistribution and VP radioimmunoassay\",\n      \"pmids\": [\"16357093\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab observation\", \"Kinetics and recycling pathway of internalized NK3R on VP neurons not characterized\", \"Contribution of endogenous NKB versus pharmacological agonist dosing unclear\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"In a Parkinson's disease model, chronic L-DOPA upregulated striatal NKB expression, and NK3R activation stimulated dopamine release via CaMKII/tyrosine hydroxylase phosphorylation, while NK3R blockade enhanced L-DOPA behavioral effects — positioning NKB/NK3R as a feedback inhibitor of dopaminergic signaling relevant to L-DOPA therapy.\",\n      \"evidence\": \"6-OHDA rat model with in situ hybridization, amperometry in striatal slices, phosphoprotein immunoblotting, and behavioral rotometry\",\n      \"pmids\": [\"18423776\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of NKB upregulation by L-DOPA not defined\", \"Translational relevance to human PD not tested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"NRSF/REST was identified as a direct transcriptional regulator of TAC3, with ChIP confirming binding to the NKB promoter and carbamazepine reducing NRSF-driven TAC3 induction, establishing a transcriptional control mechanism for NKB expression.\",\n      \"evidence\": \"Chromatin immunoprecipitation, reporter gene assays, and RT-PCR of endogenous TAC3\",\n      \"pmids\": [\"19539370\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological signals that modulate NRSF occupancy at TAC3 promoter in neurons not identified\", \"Whether sNRSF isoform has distinct regulatory effects in vivo is unknown\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Human genetic evidence established that TAC3 loss-of-function mutations cause normosmic congenital hypogonadotropic hypogonadism by impairing hypothalamic GnRH pulse generation, placing NKB as essential for reproductive neuroendocrine function.\",\n      \"evidence\": \"Homozygous TAC3 splice-site mutations in CHH kindreds; hormonal profiling and pulsatile GnRH rescue of LH secretion and fertility\",\n      \"pmids\": [\"20194706\", \"22031817\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Genotype–phenotype variability (some patients show partial reversal) not mechanistically explained\", \"Whether heterozygous carriers have subtle reproductive phenotypes is unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"The KNDy neuron model was experimentally validated: NKB is coexpressed with kisspeptin and dynorphin in arcuate neurons, and NK3R agonism directly activates KNDy neurons but not GnRH neurons, establishing NKB as an auto-feedback signal that shapes pulsatile kisspeptin/GnRH output.\",\n      \"evidence\": \"In situ hybridization for mRNA colocalization, electrophysiology of KNDy vs. GnRH neurons in mouse brain slices, LH secretion assays\",\n      \"pmids\": [\"21914775\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of NKB versus dynorphin in setting pulse frequency not quantified\", \"Whether NKB acts solely in autocrine mode or also on neighboring KNDy neurons is unresolved\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"NKB/NK3R signaling was shown to be necessary and sufficient for fear memory consolidation in the centromedial amygdala, extending TAC3 function beyond neuroendocrine regulation to emotional memory circuits.\",\n      \"evidence\": \"Lentiviral Tac2 overexpression, DREADD-based chemogenetic silencing, NK3R antagonist osanetant, and fear conditioning behavioral assays in mice\",\n      \"pmids\": [\"24976214\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream molecular targets of NK3R in CeM fear circuits not identified\", \"Relevance to human PTSD or anxiety disorders not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"NKB/NK3R signaling in the medial amygdala was found to drive LH release through a kisspeptin-independent pathway, revealing a second, extrahypothalamic reproductive circuit distinct from the canonical arcuate KNDy mechanism.\",\n      \"evidence\": \"Cell-type-specific DREADD activation, NK3R agonist stereotaxic injection, LH measurement, and Kiss1r knockout comparison in mice\",\n      \"pmids\": [\"30565563\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the downstream relay neurons from MePD to GnRH neurons is unknown\", \"Physiological conditions that engage the MePD NKB pathway versus the arcuate KNDy pathway are not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: how NKB pulse dynamics are translated into GnRH pulse frequency at the molecular level, the identity of downstream effectors mediating NK3R actions in fear and dopaminergic circuits, and the physiological significance of peripheral NKB/NK3R signaling (ovarian, vascular) in humans.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No integrated model connecting NKB pulse generation, kisspeptin release, and GnRH neuron activation at single-cell resolution\", \"Structural basis of NKB–NK3R interaction remains without cryo-EM or crystal structure\", \"Relative contributions of autocrine vs. paracrine NKB signaling within KNDy network are not quantified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 1, 2, 3, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 2, 3, 13, 14]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 7, 11, 12, 15]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [3, 11, 12, 15, 16]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 1, 2, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"TACR3\",\n      \"KISS1\",\n      \"PDYN\",\n      \"REST\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}