{"gene":"VIP","run_date":"2026-06-11T09:02:06","timeline":{"discoveries":[{"year":2020,"finding":"Food intake activates enteric VIP-producing neurons whose projections in the lamina propria contact ILC3s expressing VIPR2 (VPAC2); VIP-VIPR2 signaling inhibits IL-22 production by ILC3s, reduces antimicrobial peptide secretion from epithelial cells, and increases expression of lipid-binding proteins and transporters, thereby enhancing lipid absorption at the cost of innate immune protection.","method":"In vivo chemogenetics, conditional neuron ablation, ILC3-specific receptor knockout, cytokine measurements, histology in mice","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal genetic and chemogenetic approaches in a single rigorous study establishing circuit-level mechanism","pmids":["32050257"],"is_preprint":false},{"year":2019,"finding":"Intestinal ILC3s express VIPR2 at high levels; VIP activation of VIPR2 on ILC3s markedly enhances IL-22 production and epithelial barrier function in a circadian/food-intake-dependent manner, and VIPR2 deficiency impairs IL-22 production and increases susceptibility to inflammation-induced gut injury.","method":"Flow cytometry, cytokine ELISA, VIPR2-knockout mice, gut injury models","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — receptor-specific knockout with defined cellular phenotype, replicated across multiple experimental conditions","pmids":["31873294"],"is_preprint":false},{"year":2022,"finding":"Enteric VIP neurons activate fut2 expression (α1,2-fucosylation) in intestinal epithelial cells via the VIPR1 receptor through the Erk1/2–c-Fos signaling pathway, shaping gut microbiota composition and susceptibility to alcohol-associated liver disease.","method":"Subdiaphragmatic vagotomy, chemogenetics, enteric neuron–intestinal organoid coculture, transcriptomics, signaling pathway inhibitors","journal":"Cell host & microbe","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (chemogenetics, organoid coculture, pathway inhibitors) establishing receptor-to-pathway mechanism","pmids":["36150396"],"is_preprint":false},{"year":1989,"finding":"VIP exerts its biological effects via receptor-mediated activation of adenylyl cyclase, increasing intracellular cAMP, and acts as a neurotransmitter, neuromodulator, and secretagog; it is encoded by a 7-exon gene in humans where each exon encodes a distinct functional domain of the precursor protein.","method":"Molecular biology (gene cloning, exon mapping), receptor binding assays, cAMP measurements, immunocytochemistry","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — review consolidating molecular biology and receptor pharmacology from multiple studies, cAMP signaling confirmed by direct assay","pmids":["2698176"],"is_preprint":false},{"year":2002,"finding":"VIP signals through two G protein-coupled receptors, VPAC1 and VPAC2, which activate adenylyl cyclase (cAMP pathway); receptor–ligand interaction domains were identified by site-directed mutagenesis and receptor chimera construction; receptors undergo desensitization, internalization, and phosphorylation upon VIP binding.","method":"Site-directed mutagenesis, receptor chimeras, radioligand binding, cAMP assays, receptor internalization assays","journal":"Receptors & channels","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis and chimeric receptor studies with functional readouts replicated across multiple labs","pmids":["12529932"],"is_preprint":false},{"year":2002,"finding":"In activated macrophages, VIP inhibits production of pro-inflammatory cytokines/chemokines and nitric oxide, and stimulates IL-10 production, through effects on transcription factors NFκB, CREB, c-Jun, JunB, and IRF-1 via VPAC1/VPAC2 receptors; in T cells, VIP inhibits FasL expression through NFκB, NFAT, and Egr2/3, promoting Th2 cell survival.","method":"Cell culture, cytokine ELISA, transcription factor assays (EMSA, reporter), receptor-specific agonists/antagonists","journal":"Critical reviews in oral biology and medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple transcription factor readouts and receptor pharmacology in single-lab studies","pmids":["12090463"],"is_preprint":false},{"year":1987,"finding":"VIP and PHI are co-encoded in the same precursor, co-localized in the same nerve fibers, co-released in approximately equimolar amounts upon vagal stimulation from pig pancreatic neurons, and have additive effects on exocrine pancreatic secretion of fluid and bicarbonate; co-release is blocked by hexamethonium and mimicked by cholinergic agonists.","method":"Immunohistochemistry, isolated perfused pig pancreas, electrical nerve stimulation, radioimmunoassay, gel chromatography","journal":"The American journal of physiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct in vitro organ perfusion with pharmacological dissection and peptide quantification","pmids":["3548423"],"is_preprint":false},{"year":1991,"finding":"The mouse VIP gene contains 7 exons spanning 8 kb; both VIP and PHI coding sequences are present on the same mRNA with no evidence of differential splicing to produce separate transcripts; two polyadenylation sites in exon 7 give rise to a prominent 1700-base mRNA and a rare 1000-base species.","method":"Genomic cloning, Southern blot, S1 nuclease protection, RNase H-directed digestion with specific oligonucleotides","journal":"Brain research. Molecular brain research","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct sequencing and RNase H experiments establish gene structure and co-encoding of VIP and PHI","pmids":["1851524"],"is_preprint":false},{"year":1986,"finding":"The human VIP gene contains exons encoding both VIP and PHM-27 (a related peptide); in a VIP-producing buccal tumor, a major transcript retains intron sequences, suggesting VIP gene expression is regulated at the RNA processing level.","method":"Gene isolation with synthetic oligonucleotide probes, chemical nucleotide sequencing, RNA analysis","journal":"Peptides","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — direct sequencing of gene and detection of unspliced transcript in a single tumor model","pmids":["3748844"],"is_preprint":false},{"year":1985,"finding":"VIP and PHM are co-produced from a common larger precursor in VIP-secreting tumors, but post-translational processing differs between tissues, resulting in variable VIP/PHM ratios (0.5–8.5); two larger molecular forms containing both VIP and PHM immunoreactivity were identified by gel chromatography.","method":"Radioimmunoassay, gel chromatography, protein denaturation/reduction experiments on human VIP-omas","journal":"Peptides","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — biochemical characterization of precursor processing in multiple human tumors","pmids":["3840886"],"is_preprint":false},{"year":2006,"finding":"Mice with targeted deletion of the VIP gene spontaneously develop airway hyperresponsiveness to methacholine and increased peribronchiolar/perivascular inflammatory infiltrates with elevated cytokines in BAL fluid; intraperitoneal VIP administration over 2 weeks virtually eliminated airway hyperresponsiveness and reduced inflammation, demonstrating that endogenous VIP is a component of anti-asthma defense mechanisms.","method":"VIP gene knockout mice, methacholine challenge, ELISA for cytokines, histology, VIP replacement therapy","journal":"American journal of physiology. Lung cellular and molecular physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with pharmacological rescue providing causal mechanism","pmids":["16782752"],"is_preprint":false},{"year":2004,"finding":"VIP and NO are co-transmitters in myenteric neurons co-innervating gastrointestinal smooth muscle; at the presynaptic level, VIP induces NO release from isolated myenteric ganglia and NO facilitates VIP release; at the postsynaptic level, VIP acts via VPAC receptors/cAMP and also induces smooth muscle NO production, with VIP and NO operating as parallel co-transmitters on adenylyl cyclase/cAMP and guanylate cyclase/cGMP pathways respectively.","method":"Isolated myenteric ganglia, isolated smooth muscle cells, pharmacological dissection with specific inhibitors, cAMP/cGMP measurements","journal":"Current pharmaceutical design","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct assays on isolated tissue with pharmacological dissection, single-lab review integrating multiple experiments","pmids":["15320758"],"is_preprint":false},{"year":2006,"finding":"VIP is a transcriptional target of the orphan nuclear receptor Nurr1; Nurr1 directly transactivates the VIP promoter through Nurr1-responsive cis elements; loss of Nurr1 function in vivo reduces VIP mRNA levels in the developing midbrain; VIP mediates dopaminergic cell survival when cells are challenged with paraquat.","method":"Differential display, promoter reporter assay, VIP mRNA/protein measurements in Nurr1-regulated dopaminergic cell line, Nurr1 knockout in vivo (in situ hybridization), paraquat survival assay","journal":"Experimental neurology","confidence":"High","confidence_rationale":"Tier 1 / Strong — promoter transactivation assay combined with in vivo knockout validation and functional survival assay","pmids":["16999955"],"is_preprint":false},{"year":2006,"finding":"VIP regulates localized Ca²⁺ transients (Ca²⁺ puffs) and spontaneous transient outward currents (STOCs) in colonic smooth muscle cells via adenylyl cyclase-dependent cAMP synthesis and PKA-dependent regulation of ryanodine receptor channels; disruption of AKAP associations blocks VIP effects, indicating spatial organization of PKA signaling is required.","method":"Confocal Ca²⁺ imaging, patch-clamp electrophysiology, pharmacological inhibitors (MDL-12330A, AKAP St-Ht31 inhibitory peptide, ryanodine receptor blockers), dibutyryl-cAMP application","journal":"American journal of physiology. Cell physiology","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct electrophysiology and Ca²⁺ imaging with pharmacological dissection of signaling components","pmids":["16571863"],"is_preprint":false},{"year":2018,"finding":"mTOR signaling in VIP neurons regulates circadian clock synchrony: conditional knockout of mTOR in VIP-expressing cells impairs synchronization among SCN neurons and produces erratic circadian behavior; mTOR in VIP neurons of the olfactory bulb is activated by odor stimuli and is required for odor-evoked c-Fos responses and normal olfactory sensitivity.","method":"Cre-LoxP conditional knockout, wheel-running behavior, SCN cellular imaging, c-Fos immunostaining, olfactory sensitivity testing","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific conditional knockout with multiple behavioral and cellular phenotypic readouts","pmids":["29555746"],"is_preprint":false},{"year":2007,"finding":"VIP and VPAC2 signaling are critical for intercellular synchronization among SCN neurons and for circadian rhythms of metabolism and feeding; mice lacking either VIP or VPAC2 receptor show advanced and dampened daily metabolic/feeding rhythms, and VPAC2-knockout mice have globally reduced metabolic rate.","method":"VIP-knockout and VPAC2-knockout mice, metabolic monitoring, wheel-running behavior, light/dark and constant light conditions","journal":"American journal of physiology. Regulatory, integrative and comparative physiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent genetic knockouts with multiple physiological readouts","pmids":["18032467"],"is_preprint":false},{"year":2020,"finding":"Ablation of VIP neurons in the adult SCN shortens circadian period and reduces duration of daily activity, and severely dampens corticosterone rhythms, but does not abolish locomotor rhythmicity; in contrast, neonatal SCN VIP neuron ablation dramatically reduces circadian gene expression and mimics global Vip deletion, indicating developmental and adult roles of VIP neurons in SCN function differ.","method":"Caspase3-mediated cell ablation in VIP-Cre mice, wheel-running, corticosterone measurements, SCN PER2::LUC bioluminescence recording","journal":"Journal of biological rhythms","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific ablation at distinct developmental stages with multiple physiological and molecular readouts","pmids":["32536240"],"is_preprint":false},{"year":2017,"finding":"ErbB4 deletion specifically from VIP interneurons during development alters VIP interneuron activity patterns, severely dysregulates cortical temporal organization and state dependence, reduces cortical responses to sensory stimuli, and impairs sensory learning; phenotypes emerge during adolescence.","method":"Conditional ErbB4 knockout in VIP interneurons, in vivo electrophysiology, sensory learning behavioral assays","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional genetic deletion with in vivo circuit-level and behavioral readouts","pmids":["28817803"],"is_preprint":false},{"year":2019,"finding":"Nicotine directly depolarizes and excites VIP interneurons via nicotinic acetylcholine receptors; chemogenetic inhibition of VIP neurons prevents nicotine's indirect excitatory effects on pyramidal neurons, establishing that VIP cells disinhibit pyramidal cells (by inhibiting other interneurons) in auditory cortex.","method":"Whole-cell patch-clamp recordings in vitro, receptor antagonists, DREADD-mediated chemogenetic inhibition of VIP neurons","journal":"Synapse (New York, N.Y.)","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct electrophysiology combined with chemogenetic circuit dissection","pmids":["31081950"],"is_preprint":false},{"year":2016,"finding":"VIP+ interneurons exert a state-independent facilitation of neocortical network activity; pharmacogenetic blockade of VIP+ cell output reduces network activity during locomotion, non-locomotion, anesthesia, and visual stimulation. VIP+ cell activity correlates most strongly with mean population activity of nearby excitatory neurons.","method":"In vivo Ca²⁺ imaging (two-photon), pharmacogenetic (DREADD) blockade of VIP+ neurons in mouse visual cortex","journal":"Journal of neurophysiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo Ca²⁺ imaging combined with pharmacogenetic manipulation with multiple brain-state readouts","pmids":["26961109"],"is_preprint":false},{"year":2003,"finding":"VIP stimulates astrocytes to secrete neuroprotective proteins including activity-dependent neurotrophic factor (ADNF) and activity-dependent neuroprotective protein (ADNP); ADNP was discovered as a glial-cell mediator of VIP-induced neuroprotection. The lipophilic VIP analog SNV was identified as retaining neuroprotective activity with improved stability.","method":"Embryonic neuron cultures, astrocyte conditioned medium experiments, protein identification, analog synthesis and activity assays","journal":"Journal of molecular neuroscience : MN","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro cell culture with conditioned medium and protein identification, single-lab system","pmids":["14501014"],"is_preprint":false},{"year":2000,"finding":"VIP and its potent lipophilic analog SNV promote human keratinocyte proliferation via VPAC1 and VPAC2 receptors; keratinocytes express PACAP but not VIP mRNA, suggesting paracrine VIP and autocrine PACAP signaling; VIP and SNV increase nitric oxide and cGMP levels in keratinocytes; SNV does not elevate cAMP (unlike VIP), indicating differential downstream signaling.","method":"RT-PCR for receptor expression, cell proliferation assays, cAMP and cGMP measurements, NO measurement","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple signaling readouts with receptor expression analysis, single lab","pmids":["10858492"],"is_preprint":false},{"year":1991,"finding":"A VIP antagonist (neurotensin-VIP hybrid) binds VIP receptors on spinal cord cells with 10-fold higher affinity than VIP itself, but requires 1000-fold higher concentrations to displace VIP from lymphoid cell receptors, demonstrating pharmacological heterogeneity between central nervous system and immune VIP receptors.","method":"Competitive radioligand displacement assays on spinal cord cells and lymphoid cells","journal":"Brain research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct receptor binding assays across two cell types with quantified pharmacology","pmids":["1647246"],"is_preprint":false},{"year":1997,"finding":"VIP-1 receptor expression is required for VIP-stimulated growth of pancreatic adenocarcinoma cells; VIP (100 pM) stimulates Capan-2 cell growth via VIP-1 receptors coupled to adenylyl cyclase (half-maximal cAMP increase at 0.5–5 nM VIP); secretin (1 μM but not 1 nM) also stimulates cAMP, consistent with VIP-1 receptor pharmacology.","method":"RT-PCR/Southern blot for receptor expression, cAMP assay, [³H]-thymidine incorporation for cell growth","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — receptor-coupled cAMP and proliferation assays with pharmacological receptor identification","pmids":["9108448"],"is_preprint":false},{"year":2000,"finding":"VIP and PACAP inhibit LPS-stimulated TGF-β1 production in macrophages (both Raw 264.7 cell line and peritoneal macrophages) by reducing TGF-β1 steady-state mRNA levels; this effect is mediated through VPAC1, VPAC2, and PAC1 receptors; VIP acts primarily through the cAMP pathway while PACAP activates both cAMP and protein kinase C pathways.","method":"LPS stimulation of macrophages, cytokine ELISA, Northern/RT-PCR for mRNA levels, receptor-selective pharmacology, PKC/PKA pathway inhibitors, in vivo VIP administration","journal":"Journal of neuroimmunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple readouts (mRNA, protein, in vivo), pathway pharmacology in two macrophage systems","pmids":["10808055"],"is_preprint":false},{"year":2005,"finding":"In prostate LNCaP cells, VIP induces c-fos mRNA and protein expression via a Ca²⁺-dependent mechanism; VIP elevates intracellular Ca²⁺, and chelation with BAPTA/AM abolishes c-fos induction; VIP stimulates VEGF mRNA and protein expression through both cAMP/PKA and Ca²⁺ pathways, and AP-1 binding (c-Fos/c-Jun) is required for VEGF upregulation; VIP also induces neuroendocrine differentiation (neurite outgrowth) partially dependent on Ca²⁺.","method":"RT-PCR, Western blot, fura-2 Ca²⁺ imaging, BAPTA/AM chelation, specific kinase inhibitors (H89, curcumin), real-time RT-PCR","journal":"Biochimica et biophysica acta","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple signaling pathway readouts with pharmacological dissection in a single cell line","pmids":["15921770"],"is_preprint":false},{"year":2011,"finding":"VPAC1 receptor signaling mediates VIP enhancement of DSS-induced colitis severity; in VPAC2-knockout mice, colitis is worsened and suppression of VPAC1 signals with PKA inhibitors reduces clinical severity and tissue levels of IL-6, IL-1β, and MMP-9, demonstrating that VPAC1 and VPAC2 have opposing roles in regulating mucosal inflammation.","method":"VPAC1-KO and VPAC2-KO mice, DSS-induced colitis model, myeloperoxidase assay, cytokine/MMP ELISA, PKA inhibitor treatment","journal":"Cellular immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — two receptor-specific knockouts with pharmacological rescue and multiple inflammatory markers","pmids":["21295288"],"is_preprint":false},{"year":2010,"finding":"VIP/PACAP activation of VPAC1/VPAC2 receptors in CA1 pyramidal cells increases evoked NMDA currents via the cAMP/PKA pathway, while PACAP activation of PAC1 receptors enhances NMDA receptor function through a PLC/PKC/Pyk2/Src signaling pathway.","method":"Electrophysiology (patch-clamp) in hippocampal neurons, pharmacological receptor and pathway dissection","journal":"Journal of molecular neuroscience : MN","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct electrophysiology with receptor-selective pharmacology, but abstract does not specify full experimental detail","pmids":["20414742"],"is_preprint":false},{"year":1997,"finding":"A goldfish full-length VIP receptor expressed in COS-7 cells couples to cAMP production in response to VIP and PACAP; VIP shows higher potency than PACAP (EC50 of VIP = 1 nM), establishing conserved receptor-G protein coupling across vertebrate evolution.","method":"cDNA cloning, heterologous expression in COS-7 cells, cAMP radioimmunoassay, competitive peptide concentration-response","journal":"General and comparative endocrinology","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct functional expression in defined cell system, single lab","pmids":["9038250"],"is_preprint":false},{"year":2010,"finding":"VPAC1 receptor is localized to the nuclear fraction of human breast cancer cells, while VPAC2 receptor is extranuclear; both receptors are functional as shown by VIP-stimulated cAMP production from both plasma membrane and nuclear fractions; VIP also increases its own intracellular and extracellular levels, suggesting an autocrine/intracrine regulatory loop.","method":"Subcellular fractionation, Western blot, cAMP assay on nuclear and membrane fractions, immunohistochemistry of breast tumor samples","journal":"Peptides","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — fractionation with functional cAMP assay in two cell lines, single lab","pmids":["20691743"],"is_preprint":false},{"year":1994,"finding":"VIP-R2 (VPAC2) expression in T lymphocytes is inducible upon TCR/CD3 stimulation, whereas VIP-R1 (VPAC1) is constitutively expressed; VIP itself can induce VIP-R2 gene expression in T cells in the absence of additional stimuli, suggesting positive autoregulation of the VIP signaling axis in lymphocytes.","method":"RT-PCR for VIP-R1 and VIP-R2 mRNA in unstimulated and TCR-stimulated lymphocyte subpopulations","journal":"Journal of neuroimmunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mRNA expression in defined cell populations and subpopulations with specific stimulation, single lab","pmids":["8784257"],"is_preprint":false},{"year":1994,"finding":"VIP mRNA is expressed in rat T and B lymphocytes (thymocytes, splenic and lymph node T and B cells) and in a T-T hybridoma, establishing that immune cells themselves can produce VIP as a potential autocrine/paracrine cytokine.","method":"RT-PCR, Southern blot analysis, confirmed by size comparison with cortical VIP cDNA","journal":"Regulatory peptides","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — RT-PCR with Southern blot confirmation, single lab and single method","pmids":["8190917"],"is_preprint":false},{"year":2020,"finding":"Loss of MeCP2 specifically from VIP interneurons replicates key neural and behavioral phenotypes of global Mecp2 loss of function (Rett Syndrome model), identifying VIP interneuron dysfunction as a key pathophysiological node.","method":"Conditional Mecp2 knockout restricted to VIP interneurons, behavioral phenotyping, neural circuit analysis","journal":"eLife","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific genetic knockout with behavioral and neural phenotypes, single lab","pmids":["32343226"],"is_preprint":false}],"current_model":"VIP is a 28-amino-acid neuropeptide co-encoded with PHI/PHM on a 7-exon gene, processed from a common precursor, stored in dense-core vesicles and co-released with PHI; it signals through two class B GPCRs (VPAC1 and VPAC2) primarily via adenylyl cyclase/cAMP/PKA and also through Ca²⁺/PLC pathways, mediating smooth muscle relaxation (via cAMP and ryanodine receptor-dependent Ca²⁺ transients), disinhibition of cortical pyramidal neurons through GABAergic VIP+ interneurons, circadian pacemaker synchrony in the SCN via VPAC2/mTOR signaling, intestinal neuro-immune regulation (suppressing or enhancing ILC3-derived IL-22 depending on context via VIPR2), epithelial fucosylation via VIPR1/Erk1-c-Fos, and immunomodulation through inhibition of pro-inflammatory transcription factors (NFκB, CREB, AP-1) in macrophages and T cells; its transcription is regulated by the nuclear receptor Nurr1 in dopaminergic neurons, and its endogenous absence causes airway hyperresponsiveness, circadian deficits, and enhanced intestinal inflammation."},"narrative":{"mechanistic_narrative":"VIP is a vagally-regulated neuropeptide that acts as a neurotransmitter, neuromodulator, and secretagog, signaling through two class B G protein-coupled receptors, VPAC1 and VPAC2, that couple to adenylyl cyclase to raise intracellular cAMP [PMID:2698176, PMID:12529932]. It is co-encoded with the related peptide PHI/PHM on a 7-exon gene and processed from a common precursor whose products are co-localized and co-released in approximately equimolar amounts upon vagal stimulation [PMID:3548423, PMID:1851524]. Downstream of receptor binding, VIP engages cAMP/PKA signaling spatially organized by AKAP scaffolds to control ryanodine-receptor-dependent Ca²⁺ transients and outward currents in smooth muscle [PMID:16571863], and in different contexts recruits parallel Ca²⁺/PLC and nitric oxide/cGMP pathways alongside co-transmitter NO in enteric neurons [PMID:15320758, PMID:15921770]. In the brain, VIP is expressed by a defined class of cortical interneurons that disinhibit pyramidal cells and facilitate network activity [PMID:31081950, PMID:26961109], and VIP/VPAC2 signaling synchronizes suprachiasmatic-nucleus pacemaker neurons to sustain circadian and metabolic rhythms, a function dependent on mTOR within VIP neurons [PMID:18032467, PMID:29555746, PMID:32536240]. At mucosal surfaces, food-activated enteric VIP neurons signal to ILC3s through VIPR2 to bidirectionally tune IL-22 production and epithelial barrier defense, and through VIPR1/Erk1–2–c-Fos drive epithelial fucosylation that shapes the microbiota [PMID:32050257, PMID:31873294, PMID:36150396]. VIP is broadly anti-inflammatory, inhibiting pro-inflammatory transcription factors (NFκB, CREB, AP-1, IRF-1) and cytokine production in macrophages and T cells while promoting IL-10 [PMID:12090463]. Its transcription is directly activated by the orphan nuclear receptor Nurr1 in midbrain dopaminergic neurons, where VIP supports neuronal survival [PMID:16999955]. Genetic deletion of VIP causes airway hyperresponsiveness with inflammation that is reversed by VIP replacement, establishing endogenous VIP as a component of anti-asthma defense [PMID:16782752].","teleology":[{"year":1985,"claim":"Established that VIP and the related peptide PHM derive from a single larger precursor, raising the question of how one gene generates multiple bioactive peptides and how processing varies by tissue.","evidence":"Radioimmunoassay, gel chromatography, and reduction experiments on human VIP-omas","pmids":["3840886"],"confidence":"Medium","gaps":["Precursor processing enzymes not identified","Mechanism controlling tissue-specific VIP/PHM ratios unresolved"]},{"year":1986,"claim":"Defined the human VIP gene as encoding both VIP and PHM-27 and detected unspliced transcripts in a tumor, introducing RNA-processing-level regulation of VIP expression.","evidence":"Gene isolation, chemical sequencing, and RNA analysis of a VIP-producing buccal tumor","pmids":["3748844"],"confidence":"Medium","gaps":["Intron retention observed in a single tumor","Physiological significance of unspliced transcript unknown"]},{"year":1987,"claim":"Showed that VIP and PHI are co-released in equimolar amounts upon vagal stimulation with additive secretory effects, establishing them as functional co-transmitters under cholinergic control.","evidence":"Immunohistochemistry, isolated perfused pig pancreas with electrical nerve stimulation, radioimmunoassay","pmids":["3548423"],"confidence":"High","gaps":["Receptor mediating co-transmitter effects not defined here","Generalization beyond pancreas not addressed"]},{"year":1989,"claim":"Consolidated VIP as a neurotransmitter/secretagog acting through receptor-mediated adenylyl cyclase activation and mapped its 7-exon gene with each exon encoding a functional domain.","evidence":"Review integrating gene cloning, exon mapping, receptor binding, and cAMP assays","pmids":["2698176"],"confidence":"Medium","gaps":["Distinct receptor subtypes not yet resolved","Non-cAMP signaling not characterized"]},{"year":1991,"claim":"Confirmed gene structure showing VIP and PHI co-encoded on the same mRNA with no differential splicing, and demonstrated pharmacological heterogeneity between CNS and immune VIP receptors.","evidence":"Mouse genomic cloning with RNase H mapping; competitive radioligand displacement on spinal cord versus lymphoid cells","pmids":["1851524","1647246"],"confidence":"High","gaps":["Molecular identity of receptor subtypes underlying pharmacological differences not established","Functional consequences of receptor heterogeneity unaddressed"]},{"year":1994,"claim":"Demonstrated that lymphocytes produce VIP and regulate its receptors, with VPAC2 inducible by TCR stimulation and VIP, suggesting an autocrine/paracrine immune signaling loop.","evidence":"RT-PCR and Southern blot for VIP and receptor mRNA in T and B lymphocyte subpopulations","pmids":["8190917","8784257"],"confidence":"Medium","gaps":["Functional consequences of lymphocyte-derived VIP not tested","Single method/lab evidence for receptor autoregulation"]},{"year":1997,"claim":"Linked a specific VIP receptor (VIP-1/VPAC1) coupled to adenylyl cyclase to cancer cell proliferation, and demonstrated evolutionary conservation of VIP receptor–cAMP coupling.","evidence":"Receptor expression analysis with cAMP/thymidine assays in pancreatic carcinoma cells; goldfish receptor heterologous expression in COS-7","pmids":["9108448","9038250"],"confidence":"Medium","gaps":["Receptor subtype assignment based on pharmacology, not direct cloning in human cells","In vivo relevance to tumor growth not shown"]},{"year":2000,"claim":"Extended VIP signaling beyond cAMP, showing receptor-dependent regulation of NO/cGMP in keratinocytes and cAMP-mediated suppression of macrophage TGF-β1, distinguishing VIP from PACAP downstream wiring.","evidence":"Receptor expression, cAMP/cGMP/NO measurements, proliferation assays; LPS-stimulated macrophage cytokine and mRNA analysis with pathway inhibitors","pmids":["10858492","10808055"],"confidence":"Medium","gaps":["Differential signaling of the SNV analog mechanistically unexplained","Single-lab cell-line systems"]},{"year":2002,"claim":"Resolved the molecular pharmacology of VPAC1 and VPAC2, mapping ligand-interaction domains and demonstrating receptor desensitization/internalization, and defined VIP's anti-inflammatory program at the transcription-factor level.","evidence":"Site-directed mutagenesis, receptor chimeras, radioligand and cAMP assays; macrophage/T-cell transcription-factor reporter and EMSA assays","pmids":["12529932","12090463"],"confidence":"High","gaps":["Structural basis of receptor activation not solved","Cell-type-specific differences in transcription-factor targeting unresolved"]},{"year":2006,"claim":"Dissected the proximal signaling of VIP-induced smooth muscle relaxation (cAMP/PKA/AKAP/ryanodine receptor), identified Nurr1 as a direct transcriptional activator of VIP supporting dopaminergic survival, and showed endogenous VIP defends against airway hyperresponsiveness.","evidence":"Ca²⁺ imaging and patch-clamp with pathway inhibitors; promoter reporter and Nurr1 knockout with survival assay; VIP-knockout mice with methacholine challenge and rescue","pmids":["16571863","16999955","16782752"],"confidence":"High","gaps":["Tissue-specificity of AKAP-anchored PKA signaling not generalized","Whether VIP loss contributes to human asthma not addressed"]},{"year":2007,"claim":"Established VIP/VPAC2 signaling as essential for SCN neuronal synchronization driving circadian and metabolic rhythms.","evidence":"VIP- and VPAC2-knockout mice with metabolic monitoring and behavioral recording under varying light conditions","pmids":["18032467"],"confidence":"High","gaps":["Intracellular pathway linking VPAC2 to clock gene expression not defined here"]},{"year":2010,"claim":"Expanded VIP signaling to neuronal plasticity (cAMP/PKA enhancement of NMDA currents), nuclear/extranuclear receptor compartmentalization, and an autocrine/intracrine loop in cancer cells.","evidence":"Hippocampal patch-clamp with receptor pharmacology; subcellular fractionation and cAMP assay in breast cancer cells","pmids":["20414742","20691743"],"confidence":"Medium","gaps":["Functional role of nuclear VPAC1 unresolved","Mechanism of intracrine VIP delivery to nuclear receptors unknown"]},{"year":2011,"claim":"Revealed that VPAC1 and VPAC2 exert opposing effects on mucosal inflammation, with VPAC1/PKA driving colitis severity, refining VIP's net immune role as receptor-dependent.","evidence":"VPAC1- and VPAC2-knockout mice in DSS colitis with PKA inhibitor rescue and inflammatory marker quantification","pmids":["21295288"],"confidence":"High","gaps":["Cellular targets of opposing receptor signals not pinpointed","Reconciliation with anti-inflammatory VIP effects context-dependent"]},{"year":2018,"claim":"Identified mTOR within VIP neurons as a molecular requirement for SCN circadian synchrony and olfactory sensory responses, providing an intracellular effector for VIP-neuron function.","evidence":"Conditional mTOR knockout in VIP-expressing cells with behavioral, SCN imaging, and olfactory readouts","pmids":["29555746"],"confidence":"High","gaps":["Link between mTOR and VIP peptide release not established","Mechanism of mTOR activation by odor in VIP neurons unclear"]},{"year":2020,"claim":"Defined the enteric VIP–ILC3 circuit as a feeding-gated rheostat of innate immunity and lipid absorption, and established VIP interneurons as critical nodes in cortical and Rett-syndrome pathophysiology.","evidence":"In vivo chemogenetics, conditional ablation, ILC3-specific VIPR2 knockout, cytokine/histology; conditional Mecp2 deletion in VIP interneurons; caspase ablation of SCN VIP neurons","pmids":["32050257","32343226","32536240"],"confidence":"High","gaps":["Reconciliation of opposing VIPR2 effects on IL-22 across studies context-dependent","Downstream effectors of VIP-interneuron dysfunction in Rett model not fully mapped"]},{"year":2022,"claim":"Demonstrated that enteric VIP neurons control epithelial α1,2-fucosylation via VIPR1/Erk1–2–c-Fos, linking neuronal VIP output to microbiota composition and liver disease susceptibility.","evidence":"Vagotomy, chemogenetics, enteric neuron–organoid coculture, transcriptomics, pathway inhibitors in mice","pmids":["36150396"],"confidence":"High","gaps":["Whether fut2 induction is direct or relayed through other epithelial signals unresolved","Human relevance of the VIP–fucosylation axis not tested"]},{"year":null,"claim":"How VIP-precursor processing, receptor subtype selection (VPAC1 vs VPAC2), and downstream pathway choice (cAMP/PKA vs Ca²⁺/PLC vs NO/cGMP) are integrated to produce opposing context-dependent outcomes in immunity and inflammation remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying model reconciling pro- and anti-inflammatory VIP actions","Structural basis of biased receptor signaling not determined","Tissue determinants of differential precursor processing unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[3,4,6]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[3,4,13]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[6,9]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[3,4,13]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,5,26]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[14,18,19]},{"term_id":"R-HSA-9909396","term_label":"Circadian clock","supporting_discovery_ids":[14,15,16]}],"complexes":[],"partners":["VPAC1","VPAC2","VIPR1","VIPR2","PHI","NURR1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P01282","full_name":"VIP peptides","aliases":[],"length_aa":170,"mass_kda":19.2,"function":"VIP is a neuropeptide involved in a diverse array of physiological processes through activating the PACAP subfamily of class B1 G protein-coupled receptors: VIP receptor 1 (VPR1) and VIP receptor 2 (VPR2) (PubMed:1318039, PubMed:36385145, PubMed:8933357). 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PHM-27 is a potent agonist of the calcitonin receptor CALCR, with similar efficacy as calcitonin (PubMed:15013843) Bioactive forms that cause vasodilation (PubMed:15013843, PubMed:3654650)","subcellular_location":"Secreted","url":"https://www.uniprot.org/uniprotkb/P01282/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/VIP","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/VIP","total_profiled":1310},"omim":[{"mim_id":"611648","title":"DIPHOSPHOINOSITOL PENTAKISPHOSPHATE KINASE 2; PPIP5K2","url":"https://www.omim.org/entry/611648"},{"mim_id":"610979","title":"DIPHOSPHOINOSITOL PENTAKISPHOSPHATE KINASE 1; PPIP5K1","url":"https://www.omim.org/entry/610979"},{"mim_id":"610376","title":"ATYPICAL CHEMOKINE RECEPTOR 3; 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Treatment.","date":"2023","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/37998384","citation_count":36,"is_preprint":false},{"pmid":"22991228","id":"PMC_22991228","title":"Therapeutic potential of VIP vs PACAP in diabetes.","date":"2012","source":"Journal of molecular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/22991228","citation_count":36,"is_preprint":false},{"pmid":"23900722","id":"PMC_23900722","title":"Antiproliferative effects of PACAP and VIP in serum-starved glioma cells.","date":"2013","source":"Journal of molecular neuroscience : MN","url":"https://pubmed.ncbi.nlm.nih.gov/23900722","citation_count":36,"is_preprint":false},{"pmid":"15921770","id":"PMC_15921770","title":"Vasoactive intestinal peptide (VIP) induces c-fos expression in LNCaP prostate cancer cells through a mechanism that involves Ca2+ signalling. Implications in angiogenesis and neuroendocrine differentiation.","date":"2005","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/15921770","citation_count":36,"is_preprint":false},{"pmid":"2178250","id":"PMC_2178250","title":"Vasoactive intestinal peptide (VIP): an amnestic neuropeptide.","date":"1990","source":"Peptides","url":"https://pubmed.ncbi.nlm.nih.gov/2178250","citation_count":36,"is_preprint":false},{"pmid":"16999955","id":"PMC_16999955","title":"VIP is a transcriptional target of Nurr1 in dopaminergic cells.","date":"2006","source":"Experimental neurology","url":"https://pubmed.ncbi.nlm.nih.gov/16999955","citation_count":35,"is_preprint":false},{"pmid":"31081950","id":"PMC_31081950","title":"Nicotine excites VIP interneurons to disinhibit pyramidal neurons in auditory cortex.","date":"2019","source":"Synapse (New York, N.Y.)","url":"https://pubmed.ncbi.nlm.nih.gov/31081950","citation_count":34,"is_preprint":false},{"pmid":"19859678","id":"PMC_19859678","title":"VIP and PACAP.","date":"2010","source":"Results and problems in cell differentiation","url":"https://pubmed.ncbi.nlm.nih.gov/19859678","citation_count":33,"is_preprint":false},{"pmid":"32595454","id":"PMC_32595454","title":"VIP Modulation of Hippocampal Synaptic Plasticity: A Role for VIP Receptors as Therapeutic Targets in Cognitive Decline and Mesial Temporal Lobe Epilepsy.","date":"2020","source":"Frontiers in cellular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/32595454","citation_count":33,"is_preprint":false},{"pmid":"9363981","id":"PMC_9363981","title":"(Stearyl, Norleucine17)VIP hybrid antagonizes VIP receptors on non-small cell lung cancer cells.","date":"1997","source":"Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/9363981","citation_count":33,"is_preprint":false},{"pmid":"27507936","id":"PMC_27507936","title":"Distinct Roles of SOM and VIP Interneurons during Cortical Up States.","date":"2016","source":"Frontiers in neural circuits","url":"https://pubmed.ncbi.nlm.nih.gov/27507936","citation_count":33,"is_preprint":false},{"pmid":"12570811","id":"PMC_12570811","title":"VIP and drug design.","date":"2003","source":"Current pharmaceutical design","url":"https://pubmed.ncbi.nlm.nih.gov/12570811","citation_count":32,"is_preprint":false},{"pmid":"21524251","id":"PMC_21524251","title":"VIP-induced neuroprotection of the developing brain.","date":"2011","source":"Current pharmaceutical design","url":"https://pubmed.ncbi.nlm.nih.gov/21524251","citation_count":32,"is_preprint":false},{"pmid":"21295288","id":"PMC_21295288","title":"VPAC1 (vasoactive intestinal peptide (VIP) receptor type 1) G protein-coupled receptor mediation of VIP enhancement of murine experimental colitis.","date":"2011","source":"Cellular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/21295288","citation_count":32,"is_preprint":false},{"pmid":"34944993","id":"PMC_34944993","title":"The Vulvar Immunohistochemical Panel (VIP) Project: Molecular Profiles of Vulvar Squamous Cell Carcinoma.","date":"2021","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/34944993","citation_count":31,"is_preprint":false},{"pmid":"12763526","id":"PMC_12763526","title":"VIP- and PACAP-mediated immunomodulation as prospective therapeutic tools.","date":"2003","source":"Trends in molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/12763526","citation_count":30,"is_preprint":false},{"pmid":"17683807","id":"PMC_17683807","title":"Vasoactive intestinal peptide (VIP) increases vascular endothelial growth factor (VEGF) expression and secretion in human breast cancer cells.","date":"2007","source":"Regulatory peptides","url":"https://pubmed.ncbi.nlm.nih.gov/17683807","citation_count":30,"is_preprint":false},{"pmid":"7630581","id":"PMC_7630581","title":"Role of VIP in the regulation of LH secretion in the female rat.","date":"1995","source":"Neuroscience and biobehavioral reviews","url":"https://pubmed.ncbi.nlm.nih.gov/7630581","citation_count":29,"is_preprint":false},{"pmid":"2272357","id":"PMC_2272357","title":"Cardiac responses to VIP and VIP-ergic-cholinergic interaction in isolated dog heart preparations.","date":"1990","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/2272357","citation_count":29,"is_preprint":false},{"pmid":"28472856","id":"PMC_28472856","title":"Multiple cell types form the VIP amacrine cell population.","date":"2017","source":"The Journal of comparative neurology","url":"https://pubmed.ncbi.nlm.nih.gov/28472856","citation_count":28,"is_preprint":false},{"pmid":"27381006","id":"PMC_27381006","title":"VIP impairs acquisition of the macrophage proinflammatory polarization profile.","date":"2016","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/27381006","citation_count":28,"is_preprint":false},{"pmid":"21524252","id":"PMC_21524252","title":"Immunomodulatory roles of VIP and PACAP in models of multiple sclerosis.","date":"2011","source":"Current pharmaceutical design","url":"https://pubmed.ncbi.nlm.nih.gov/21524252","citation_count":27,"is_preprint":false},{"pmid":"21666233","id":"PMC_21666233","title":"VIP and growth factors in the infected cornea.","date":"2011","source":"Investigative ophthalmology & visual science","url":"https://pubmed.ncbi.nlm.nih.gov/21666233","citation_count":27,"is_preprint":false},{"pmid":"16571863","id":"PMC_16571863","title":"VIP and PACAP regulate localized Ca2+ transients via cAMP-dependent mechanism.","date":"2006","source":"American journal of physiology. Cell physiology","url":"https://pubmed.ncbi.nlm.nih.gov/16571863","citation_count":27,"is_preprint":false},{"pmid":"9928018","id":"PMC_9928018","title":"Analogues of VIP, helodermin, and PACAP discriminate between rat and human VIP1 and VIP2 receptors.","date":"1998","source":"Annals of the New York Academy of Sciences","url":"https://pubmed.ncbi.nlm.nih.gov/9928018","citation_count":27,"is_preprint":false},{"pmid":"32536240","id":"PMC_32536240","title":"Different Roles for VIP Neurons in the Neonatal and Adult Suprachiasmatic Nucleus.","date":"2020","source":"Journal of biological rhythms","url":"https://pubmed.ncbi.nlm.nih.gov/32536240","citation_count":26,"is_preprint":false},{"pmid":"22728770","id":"PMC_22728770","title":"Vasoactive intestinal peptide (VIP) inhibits human renal cell carcinoma proliferation.","date":"2012","source":"Biochimica et biophysica acta","url":"https://pubmed.ncbi.nlm.nih.gov/22728770","citation_count":26,"is_preprint":false},{"pmid":"34179269","id":"PMC_34179269","title":"Visible Immunoprecipitation (VIP) Assay: a Simple and Versatile Method forVisual Detection of Protein-protein Interactions.","date":"2018","source":"Bio-protocol","url":"https://pubmed.ncbi.nlm.nih.gov/34179269","citation_count":26,"is_preprint":false},{"pmid":"10808055","id":"PMC_10808055","title":"Vasoactive intestinal peptide (VIP) inhibits TGF-beta1 production in murine macrophages.","date":"2000","source":"Journal of neuroimmunology","url":"https://pubmed.ncbi.nlm.nih.gov/10808055","citation_count":26,"is_preprint":false},{"pmid":"3840886","id":"PMC_3840886","title":"Evidence for common precursors but differential processing of VIP and PHM in VIP-producing tumors.","date":"1985","source":"Peptides","url":"https://pubmed.ncbi.nlm.nih.gov/3840886","citation_count":26,"is_preprint":false},{"pmid":"3748844","id":"PMC_3748844","title":"Structure and expression of the vasoactive intestinal peptide (VIP) gene in a human tumor.","date":"1986","source":"Peptides","url":"https://pubmed.ncbi.nlm.nih.gov/3748844","citation_count":25,"is_preprint":false},{"pmid":"22957100","id":"PMC_22957100","title":"Agnathan VIP, PACAP and their receptors: ancestral origins of today's highly diversified forms.","date":"2012","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22957100","citation_count":25,"is_preprint":false},{"pmid":"8719036","id":"PMC_8719036","title":"A VIP hybrid antagonist: from developmental neurobiology to clinical applications.","date":"1995","source":"Cellular and molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/8719036","citation_count":24,"is_preprint":false},{"pmid":"32460660","id":"PMC_32460660","title":"Reduced VIP Expression Affects Circadian Clock Function in VIP-IRES-CRE Mice (JAX 010908).","date":"2020","source":"Journal of biological rhythms","url":"https://pubmed.ncbi.nlm.nih.gov/32460660","citation_count":23,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":47513,"output_tokens":7786,"usd":0.129664,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":17693,"output_tokens":5275,"usd":0.11017,"stage2_stop_reason":"end_turn"},"total_usd":0.239834,"stage1_batch_id":"msgbatch_01UT1AahFPCAyn2uVweS7A9z","stage2_batch_id":"msgbatch_01HuKWtKNT4Pqj1bc8eEP5RV","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2020,\n      \"finding\": \"Food intake activates enteric VIP-producing neurons whose projections in the lamina propria contact ILC3s expressing VIPR2 (VPAC2); VIP-VIPR2 signaling inhibits IL-22 production by ILC3s, reduces antimicrobial peptide secretion from epithelial cells, and increases expression of lipid-binding proteins and transporters, thereby enhancing lipid absorption at the cost of innate immune protection.\",\n      \"method\": \"In vivo chemogenetics, conditional neuron ablation, ILC3-specific receptor knockout, cytokine measurements, histology in mice\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal genetic and chemogenetic approaches in a single rigorous study establishing circuit-level mechanism\",\n      \"pmids\": [\"32050257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Intestinal ILC3s express VIPR2 at high levels; VIP activation of VIPR2 on ILC3s markedly enhances IL-22 production and epithelial barrier function in a circadian/food-intake-dependent manner, and VIPR2 deficiency impairs IL-22 production and increases susceptibility to inflammation-induced gut injury.\",\n      \"method\": \"Flow cytometry, cytokine ELISA, VIPR2-knockout mice, gut injury models\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — receptor-specific knockout with defined cellular phenotype, replicated across multiple experimental conditions\",\n      \"pmids\": [\"31873294\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Enteric VIP neurons activate fut2 expression (α1,2-fucosylation) in intestinal epithelial cells via the VIPR1 receptor through the Erk1/2–c-Fos signaling pathway, shaping gut microbiota composition and susceptibility to alcohol-associated liver disease.\",\n      \"method\": \"Subdiaphragmatic vagotomy, chemogenetics, enteric neuron–intestinal organoid coculture, transcriptomics, signaling pathway inhibitors\",\n      \"journal\": \"Cell host & microbe\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (chemogenetics, organoid coculture, pathway inhibitors) establishing receptor-to-pathway mechanism\",\n      \"pmids\": [\"36150396\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1989,\n      \"finding\": \"VIP exerts its biological effects via receptor-mediated activation of adenylyl cyclase, increasing intracellular cAMP, and acts as a neurotransmitter, neuromodulator, and secretagog; it is encoded by a 7-exon gene in humans where each exon encodes a distinct functional domain of the precursor protein.\",\n      \"method\": \"Molecular biology (gene cloning, exon mapping), receptor binding assays, cAMP measurements, immunocytochemistry\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — review consolidating molecular biology and receptor pharmacology from multiple studies, cAMP signaling confirmed by direct assay\",\n      \"pmids\": [\"2698176\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"VIP signals through two G protein-coupled receptors, VPAC1 and VPAC2, which activate adenylyl cyclase (cAMP pathway); receptor–ligand interaction domains were identified by site-directed mutagenesis and receptor chimera construction; receptors undergo desensitization, internalization, and phosphorylation upon VIP binding.\",\n      \"method\": \"Site-directed mutagenesis, receptor chimeras, radioligand binding, cAMP assays, receptor internalization assays\",\n      \"journal\": \"Receptors & channels\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis and chimeric receptor studies with functional readouts replicated across multiple labs\",\n      \"pmids\": [\"12529932\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"In activated macrophages, VIP inhibits production of pro-inflammatory cytokines/chemokines and nitric oxide, and stimulates IL-10 production, through effects on transcription factors NFκB, CREB, c-Jun, JunB, and IRF-1 via VPAC1/VPAC2 receptors; in T cells, VIP inhibits FasL expression through NFκB, NFAT, and Egr2/3, promoting Th2 cell survival.\",\n      \"method\": \"Cell culture, cytokine ELISA, transcription factor assays (EMSA, reporter), receptor-specific agonists/antagonists\",\n      \"journal\": \"Critical reviews in oral biology and medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple transcription factor readouts and receptor pharmacology in single-lab studies\",\n      \"pmids\": [\"12090463\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"VIP and PHI are co-encoded in the same precursor, co-localized in the same nerve fibers, co-released in approximately equimolar amounts upon vagal stimulation from pig pancreatic neurons, and have additive effects on exocrine pancreatic secretion of fluid and bicarbonate; co-release is blocked by hexamethonium and mimicked by cholinergic agonists.\",\n      \"method\": \"Immunohistochemistry, isolated perfused pig pancreas, electrical nerve stimulation, radioimmunoassay, gel chromatography\",\n      \"journal\": \"The American journal of physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct in vitro organ perfusion with pharmacological dissection and peptide quantification\",\n      \"pmids\": [\"3548423\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"The mouse VIP gene contains 7 exons spanning 8 kb; both VIP and PHI coding sequences are present on the same mRNA with no evidence of differential splicing to produce separate transcripts; two polyadenylation sites in exon 7 give rise to a prominent 1700-base mRNA and a rare 1000-base species.\",\n      \"method\": \"Genomic cloning, Southern blot, S1 nuclease protection, RNase H-directed digestion with specific oligonucleotides\",\n      \"journal\": \"Brain research. Molecular brain research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct sequencing and RNase H experiments establish gene structure and co-encoding of VIP and PHI\",\n      \"pmids\": [\"1851524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1986,\n      \"finding\": \"The human VIP gene contains exons encoding both VIP and PHM-27 (a related peptide); in a VIP-producing buccal tumor, a major transcript retains intron sequences, suggesting VIP gene expression is regulated at the RNA processing level.\",\n      \"method\": \"Gene isolation with synthetic oligonucleotide probes, chemical nucleotide sequencing, RNA analysis\",\n      \"journal\": \"Peptides\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — direct sequencing of gene and detection of unspliced transcript in a single tumor model\",\n      \"pmids\": [\"3748844\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1985,\n      \"finding\": \"VIP and PHM are co-produced from a common larger precursor in VIP-secreting tumors, but post-translational processing differs between tissues, resulting in variable VIP/PHM ratios (0.5–8.5); two larger molecular forms containing both VIP and PHM immunoreactivity were identified by gel chromatography.\",\n      \"method\": \"Radioimmunoassay, gel chromatography, protein denaturation/reduction experiments on human VIP-omas\",\n      \"journal\": \"Peptides\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — biochemical characterization of precursor processing in multiple human tumors\",\n      \"pmids\": [\"3840886\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Mice with targeted deletion of the VIP gene spontaneously develop airway hyperresponsiveness to methacholine and increased peribronchiolar/perivascular inflammatory infiltrates with elevated cytokines in BAL fluid; intraperitoneal VIP administration over 2 weeks virtually eliminated airway hyperresponsiveness and reduced inflammation, demonstrating that endogenous VIP is a component of anti-asthma defense mechanisms.\",\n      \"method\": \"VIP gene knockout mice, methacholine challenge, ELISA for cytokines, histology, VIP replacement therapy\",\n      \"journal\": \"American journal of physiology. Lung cellular and molecular physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with pharmacological rescue providing causal mechanism\",\n      \"pmids\": [\"16782752\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"VIP and NO are co-transmitters in myenteric neurons co-innervating gastrointestinal smooth muscle; at the presynaptic level, VIP induces NO release from isolated myenteric ganglia and NO facilitates VIP release; at the postsynaptic level, VIP acts via VPAC receptors/cAMP and also induces smooth muscle NO production, with VIP and NO operating as parallel co-transmitters on adenylyl cyclase/cAMP and guanylate cyclase/cGMP pathways respectively.\",\n      \"method\": \"Isolated myenteric ganglia, isolated smooth muscle cells, pharmacological dissection with specific inhibitors, cAMP/cGMP measurements\",\n      \"journal\": \"Current pharmaceutical design\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct assays on isolated tissue with pharmacological dissection, single-lab review integrating multiple experiments\",\n      \"pmids\": [\"15320758\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"VIP is a transcriptional target of the orphan nuclear receptor Nurr1; Nurr1 directly transactivates the VIP promoter through Nurr1-responsive cis elements; loss of Nurr1 function in vivo reduces VIP mRNA levels in the developing midbrain; VIP mediates dopaminergic cell survival when cells are challenged with paraquat.\",\n      \"method\": \"Differential display, promoter reporter assay, VIP mRNA/protein measurements in Nurr1-regulated dopaminergic cell line, Nurr1 knockout in vivo (in situ hybridization), paraquat survival assay\",\n      \"journal\": \"Experimental neurology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — promoter transactivation assay combined with in vivo knockout validation and functional survival assay\",\n      \"pmids\": [\"16999955\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"VIP regulates localized Ca²⁺ transients (Ca²⁺ puffs) and spontaneous transient outward currents (STOCs) in colonic smooth muscle cells via adenylyl cyclase-dependent cAMP synthesis and PKA-dependent regulation of ryanodine receptor channels; disruption of AKAP associations blocks VIP effects, indicating spatial organization of PKA signaling is required.\",\n      \"method\": \"Confocal Ca²⁺ imaging, patch-clamp electrophysiology, pharmacological inhibitors (MDL-12330A, AKAP St-Ht31 inhibitory peptide, ryanodine receptor blockers), dibutyryl-cAMP application\",\n      \"journal\": \"American journal of physiology. Cell physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct electrophysiology and Ca²⁺ imaging with pharmacological dissection of signaling components\",\n      \"pmids\": [\"16571863\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"mTOR signaling in VIP neurons regulates circadian clock synchrony: conditional knockout of mTOR in VIP-expressing cells impairs synchronization among SCN neurons and produces erratic circadian behavior; mTOR in VIP neurons of the olfactory bulb is activated by odor stimuli and is required for odor-evoked c-Fos responses and normal olfactory sensitivity.\",\n      \"method\": \"Cre-LoxP conditional knockout, wheel-running behavior, SCN cellular imaging, c-Fos immunostaining, olfactory sensitivity testing\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific conditional knockout with multiple behavioral and cellular phenotypic readouts\",\n      \"pmids\": [\"29555746\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"VIP and VPAC2 signaling are critical for intercellular synchronization among SCN neurons and for circadian rhythms of metabolism and feeding; mice lacking either VIP or VPAC2 receptor show advanced and dampened daily metabolic/feeding rhythms, and VPAC2-knockout mice have globally reduced metabolic rate.\",\n      \"method\": \"VIP-knockout and VPAC2-knockout mice, metabolic monitoring, wheel-running behavior, light/dark and constant light conditions\",\n      \"journal\": \"American journal of physiology. Regulatory, integrative and comparative physiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent genetic knockouts with multiple physiological readouts\",\n      \"pmids\": [\"18032467\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Ablation of VIP neurons in the adult SCN shortens circadian period and reduces duration of daily activity, and severely dampens corticosterone rhythms, but does not abolish locomotor rhythmicity; in contrast, neonatal SCN VIP neuron ablation dramatically reduces circadian gene expression and mimics global Vip deletion, indicating developmental and adult roles of VIP neurons in SCN function differ.\",\n      \"method\": \"Caspase3-mediated cell ablation in VIP-Cre mice, wheel-running, corticosterone measurements, SCN PER2::LUC bioluminescence recording\",\n      \"journal\": \"Journal of biological rhythms\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific ablation at distinct developmental stages with multiple physiological and molecular readouts\",\n      \"pmids\": [\"32536240\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"ErbB4 deletion specifically from VIP interneurons during development alters VIP interneuron activity patterns, severely dysregulates cortical temporal organization and state dependence, reduces cortical responses to sensory stimuli, and impairs sensory learning; phenotypes emerge during adolescence.\",\n      \"method\": \"Conditional ErbB4 knockout in VIP interneurons, in vivo electrophysiology, sensory learning behavioral assays\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional genetic deletion with in vivo circuit-level and behavioral readouts\",\n      \"pmids\": [\"28817803\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Nicotine directly depolarizes and excites VIP interneurons via nicotinic acetylcholine receptors; chemogenetic inhibition of VIP neurons prevents nicotine's indirect excitatory effects on pyramidal neurons, establishing that VIP cells disinhibit pyramidal cells (by inhibiting other interneurons) in auditory cortex.\",\n      \"method\": \"Whole-cell patch-clamp recordings in vitro, receptor antagonists, DREADD-mediated chemogenetic inhibition of VIP neurons\",\n      \"journal\": \"Synapse (New York, N.Y.)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct electrophysiology combined with chemogenetic circuit dissection\",\n      \"pmids\": [\"31081950\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"VIP+ interneurons exert a state-independent facilitation of neocortical network activity; pharmacogenetic blockade of VIP+ cell output reduces network activity during locomotion, non-locomotion, anesthesia, and visual stimulation. VIP+ cell activity correlates most strongly with mean population activity of nearby excitatory neurons.\",\n      \"method\": \"In vivo Ca²⁺ imaging (two-photon), pharmacogenetic (DREADD) blockade of VIP+ neurons in mouse visual cortex\",\n      \"journal\": \"Journal of neurophysiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo Ca²⁺ imaging combined with pharmacogenetic manipulation with multiple brain-state readouts\",\n      \"pmids\": [\"26961109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"VIP stimulates astrocytes to secrete neuroprotective proteins including activity-dependent neurotrophic factor (ADNF) and activity-dependent neuroprotective protein (ADNP); ADNP was discovered as a glial-cell mediator of VIP-induced neuroprotection. The lipophilic VIP analog SNV was identified as retaining neuroprotective activity with improved stability.\",\n      \"method\": \"Embryonic neuron cultures, astrocyte conditioned medium experiments, protein identification, analog synthesis and activity assays\",\n      \"journal\": \"Journal of molecular neuroscience : MN\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro cell culture with conditioned medium and protein identification, single-lab system\",\n      \"pmids\": [\"14501014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"VIP and its potent lipophilic analog SNV promote human keratinocyte proliferation via VPAC1 and VPAC2 receptors; keratinocytes express PACAP but not VIP mRNA, suggesting paracrine VIP and autocrine PACAP signaling; VIP and SNV increase nitric oxide and cGMP levels in keratinocytes; SNV does not elevate cAMP (unlike VIP), indicating differential downstream signaling.\",\n      \"method\": \"RT-PCR for receptor expression, cell proliferation assays, cAMP and cGMP measurements, NO measurement\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple signaling readouts with receptor expression analysis, single lab\",\n      \"pmids\": [\"10858492\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1991,\n      \"finding\": \"A VIP antagonist (neurotensin-VIP hybrid) binds VIP receptors on spinal cord cells with 10-fold higher affinity than VIP itself, but requires 1000-fold higher concentrations to displace VIP from lymphoid cell receptors, demonstrating pharmacological heterogeneity between central nervous system and immune VIP receptors.\",\n      \"method\": \"Competitive radioligand displacement assays on spinal cord cells and lymphoid cells\",\n      \"journal\": \"Brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct receptor binding assays across two cell types with quantified pharmacology\",\n      \"pmids\": [\"1647246\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"VIP-1 receptor expression is required for VIP-stimulated growth of pancreatic adenocarcinoma cells; VIP (100 pM) stimulates Capan-2 cell growth via VIP-1 receptors coupled to adenylyl cyclase (half-maximal cAMP increase at 0.5–5 nM VIP); secretin (1 μM but not 1 nM) also stimulates cAMP, consistent with VIP-1 receptor pharmacology.\",\n      \"method\": \"RT-PCR/Southern blot for receptor expression, cAMP assay, [³H]-thymidine incorporation for cell growth\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — receptor-coupled cAMP and proliferation assays with pharmacological receptor identification\",\n      \"pmids\": [\"9108448\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"VIP and PACAP inhibit LPS-stimulated TGF-β1 production in macrophages (both Raw 264.7 cell line and peritoneal macrophages) by reducing TGF-β1 steady-state mRNA levels; this effect is mediated through VPAC1, VPAC2, and PAC1 receptors; VIP acts primarily through the cAMP pathway while PACAP activates both cAMP and protein kinase C pathways.\",\n      \"method\": \"LPS stimulation of macrophages, cytokine ELISA, Northern/RT-PCR for mRNA levels, receptor-selective pharmacology, PKC/PKA pathway inhibitors, in vivo VIP administration\",\n      \"journal\": \"Journal of neuroimmunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple readouts (mRNA, protein, in vivo), pathway pharmacology in two macrophage systems\",\n      \"pmids\": [\"10808055\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"In prostate LNCaP cells, VIP induces c-fos mRNA and protein expression via a Ca²⁺-dependent mechanism; VIP elevates intracellular Ca²⁺, and chelation with BAPTA/AM abolishes c-fos induction; VIP stimulates VEGF mRNA and protein expression through both cAMP/PKA and Ca²⁺ pathways, and AP-1 binding (c-Fos/c-Jun) is required for VEGF upregulation; VIP also induces neuroendocrine differentiation (neurite outgrowth) partially dependent on Ca²⁺.\",\n      \"method\": \"RT-PCR, Western blot, fura-2 Ca²⁺ imaging, BAPTA/AM chelation, specific kinase inhibitors (H89, curcumin), real-time RT-PCR\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple signaling pathway readouts with pharmacological dissection in a single cell line\",\n      \"pmids\": [\"15921770\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"VPAC1 receptor signaling mediates VIP enhancement of DSS-induced colitis severity; in VPAC2-knockout mice, colitis is worsened and suppression of VPAC1 signals with PKA inhibitors reduces clinical severity and tissue levels of IL-6, IL-1β, and MMP-9, demonstrating that VPAC1 and VPAC2 have opposing roles in regulating mucosal inflammation.\",\n      \"method\": \"VPAC1-KO and VPAC2-KO mice, DSS-induced colitis model, myeloperoxidase assay, cytokine/MMP ELISA, PKA inhibitor treatment\",\n      \"journal\": \"Cellular immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two receptor-specific knockouts with pharmacological rescue and multiple inflammatory markers\",\n      \"pmids\": [\"21295288\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"VIP/PACAP activation of VPAC1/VPAC2 receptors in CA1 pyramidal cells increases evoked NMDA currents via the cAMP/PKA pathway, while PACAP activation of PAC1 receptors enhances NMDA receptor function through a PLC/PKC/Pyk2/Src signaling pathway.\",\n      \"method\": \"Electrophysiology (patch-clamp) in hippocampal neurons, pharmacological receptor and pathway dissection\",\n      \"journal\": \"Journal of molecular neuroscience : MN\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct electrophysiology with receptor-selective pharmacology, but abstract does not specify full experimental detail\",\n      \"pmids\": [\"20414742\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"A goldfish full-length VIP receptor expressed in COS-7 cells couples to cAMP production in response to VIP and PACAP; VIP shows higher potency than PACAP (EC50 of VIP = 1 nM), establishing conserved receptor-G protein coupling across vertebrate evolution.\",\n      \"method\": \"cDNA cloning, heterologous expression in COS-7 cells, cAMP radioimmunoassay, competitive peptide concentration-response\",\n      \"journal\": \"General and comparative endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct functional expression in defined cell system, single lab\",\n      \"pmids\": [\"9038250\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"VPAC1 receptor is localized to the nuclear fraction of human breast cancer cells, while VPAC2 receptor is extranuclear; both receptors are functional as shown by VIP-stimulated cAMP production from both plasma membrane and nuclear fractions; VIP also increases its own intracellular and extracellular levels, suggesting an autocrine/intracrine regulatory loop.\",\n      \"method\": \"Subcellular fractionation, Western blot, cAMP assay on nuclear and membrane fractions, immunohistochemistry of breast tumor samples\",\n      \"journal\": \"Peptides\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — fractionation with functional cAMP assay in two cell lines, single lab\",\n      \"pmids\": [\"20691743\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"VIP-R2 (VPAC2) expression in T lymphocytes is inducible upon TCR/CD3 stimulation, whereas VIP-R1 (VPAC1) is constitutively expressed; VIP itself can induce VIP-R2 gene expression in T cells in the absence of additional stimuli, suggesting positive autoregulation of the VIP signaling axis in lymphocytes.\",\n      \"method\": \"RT-PCR for VIP-R1 and VIP-R2 mRNA in unstimulated and TCR-stimulated lymphocyte subpopulations\",\n      \"journal\": \"Journal of neuroimmunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mRNA expression in defined cell populations and subpopulations with specific stimulation, single lab\",\n      \"pmids\": [\"8784257\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1994,\n      \"finding\": \"VIP mRNA is expressed in rat T and B lymphocytes (thymocytes, splenic and lymph node T and B cells) and in a T-T hybridoma, establishing that immune cells themselves can produce VIP as a potential autocrine/paracrine cytokine.\",\n      \"method\": \"RT-PCR, Southern blot analysis, confirmed by size comparison with cortical VIP cDNA\",\n      \"journal\": \"Regulatory peptides\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — RT-PCR with Southern blot confirmation, single lab and single method\",\n      \"pmids\": [\"8190917\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Loss of MeCP2 specifically from VIP interneurons replicates key neural and behavioral phenotypes of global Mecp2 loss of function (Rett Syndrome model), identifying VIP interneuron dysfunction as a key pathophysiological node.\",\n      \"method\": \"Conditional Mecp2 knockout restricted to VIP interneurons, behavioral phenotyping, neural circuit analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific genetic knockout with behavioral and neural phenotypes, single lab\",\n      \"pmids\": [\"32343226\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"VIP is a 28-amino-acid neuropeptide co-encoded with PHI/PHM on a 7-exon gene, processed from a common precursor, stored in dense-core vesicles and co-released with PHI; it signals through two class B GPCRs (VPAC1 and VPAC2) primarily via adenylyl cyclase/cAMP/PKA and also through Ca²⁺/PLC pathways, mediating smooth muscle relaxation (via cAMP and ryanodine receptor-dependent Ca²⁺ transients), disinhibition of cortical pyramidal neurons through GABAergic VIP+ interneurons, circadian pacemaker synchrony in the SCN via VPAC2/mTOR signaling, intestinal neuro-immune regulation (suppressing or enhancing ILC3-derived IL-22 depending on context via VIPR2), epithelial fucosylation via VIPR1/Erk1-c-Fos, and immunomodulation through inhibition of pro-inflammatory transcription factors (NFκB, CREB, AP-1) in macrophages and T cells; its transcription is regulated by the nuclear receptor Nurr1 in dopaminergic neurons, and its endogenous absence causes airway hyperresponsiveness, circadian deficits, and enhanced intestinal inflammation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"VIP is a vagally-regulated neuropeptide that acts as a neurotransmitter, neuromodulator, and secretagog, signaling through two class B G protein-coupled receptors, VPAC1 and VPAC2, that couple to adenylyl cyclase to raise intracellular cAMP [#3, #4]. It is co-encoded with the related peptide PHI/PHM on a 7-exon gene and processed from a common precursor whose products are co-localized and co-released in approximately equimolar amounts upon vagal stimulation [#6, #7]. Downstream of receptor binding, VIP engages cAMP/PKA signaling spatially organized by AKAP scaffolds to control ryanodine-receptor-dependent Ca\\u00b2\\u207a transients and outward currents in smooth muscle [#13], and in different contexts recruits parallel Ca\\u00b2\\u207a/PLC and nitric oxide/cGMP pathways alongside co-transmitter NO in enteric neurons [#11, #25]. In the brain, VIP is expressed by a defined class of cortical interneurons that disinhibit pyramidal cells and facilitate network activity [#18, #19], and VIP/VPAC2 signaling synchronizes suprachiasmatic-nucleus pacemaker neurons to sustain circadian and metabolic rhythms, a function dependent on mTOR within VIP neurons [#15, #14, #16]. At mucosal surfaces, food-activated enteric VIP neurons signal to ILC3s through VIPR2 to bidirectionally tune IL-22 production and epithelial barrier defense, and through VIPR1/Erk1\\u20132\\u2013c-Fos drive epithelial fucosylation that shapes the microbiota [#0, #1, #2]. VIP is broadly anti-inflammatory, inhibiting pro-inflammatory transcription factors (NF\\u03baB, CREB, AP-1, IRF-1) and cytokine production in macrophages and T cells while promoting IL-10 [#5]. Its transcription is directly activated by the orphan nuclear receptor Nurr1 in midbrain dopaminergic neurons, where VIP supports neuronal survival [#12]. Genetic deletion of VIP causes airway hyperresponsiveness with inflammation that is reversed by VIP replacement, establishing endogenous VIP as a component of anti-asthma defense [#10].\",\n  \"teleology\": [\n    {\n      \"year\": 1985,\n      \"claim\": \"Established that VIP and the related peptide PHM derive from a single larger precursor, raising the question of how one gene generates multiple bioactive peptides and how processing varies by tissue.\",\n      \"evidence\": \"Radioimmunoassay, gel chromatography, and reduction experiments on human VIP-omas\",\n      \"pmids\": [\"3840886\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Precursor processing enzymes not identified\", \"Mechanism controlling tissue-specific VIP/PHM ratios unresolved\"]\n    },\n    {\n      \"year\": 1986,\n      \"claim\": \"Defined the human VIP gene as encoding both VIP and PHM-27 and detected unspliced transcripts in a tumor, introducing RNA-processing-level regulation of VIP expression.\",\n      \"evidence\": \"Gene isolation, chemical sequencing, and RNA analysis of a VIP-producing buccal tumor\",\n      \"pmids\": [\"3748844\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Intron retention observed in a single tumor\", \"Physiological significance of unspliced transcript unknown\"]\n    },\n    {\n      \"year\": 1987,\n      \"claim\": \"Showed that VIP and PHI are co-released in equimolar amounts upon vagal stimulation with additive secretory effects, establishing them as functional co-transmitters under cholinergic control.\",\n      \"evidence\": \"Immunohistochemistry, isolated perfused pig pancreas with electrical nerve stimulation, radioimmunoassay\",\n      \"pmids\": [\"3548423\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor mediating co-transmitter effects not defined here\", \"Generalization beyond pancreas not addressed\"]\n    },\n    {\n      \"year\": 1989,\n      \"claim\": \"Consolidated VIP as a neurotransmitter/secretagog acting through receptor-mediated adenylyl cyclase activation and mapped its 7-exon gene with each exon encoding a functional domain.\",\n      \"evidence\": \"Review integrating gene cloning, exon mapping, receptor binding, and cAMP assays\",\n      \"pmids\": [\"2698176\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Distinct receptor subtypes not yet resolved\", \"Non-cAMP signaling not characterized\"]\n    },\n    {\n      \"year\": 1991,\n      \"claim\": \"Confirmed gene structure showing VIP and PHI co-encoded on the same mRNA with no differential splicing, and demonstrated pharmacological heterogeneity between CNS and immune VIP receptors.\",\n      \"evidence\": \"Mouse genomic cloning with RNase H mapping; competitive radioligand displacement on spinal cord versus lymphoid cells\",\n      \"pmids\": [\"1851524\", \"1647246\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular identity of receptor subtypes underlying pharmacological differences not established\", \"Functional consequences of receptor heterogeneity unaddressed\"]\n    },\n    {\n      \"year\": 1994,\n      \"claim\": \"Demonstrated that lymphocytes produce VIP and regulate its receptors, with VPAC2 inducible by TCR stimulation and VIP, suggesting an autocrine/paracrine immune signaling loop.\",\n      \"evidence\": \"RT-PCR and Southern blot for VIP and receptor mRNA in T and B lymphocyte subpopulations\",\n      \"pmids\": [\"8190917\", \"8784257\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequences of lymphocyte-derived VIP not tested\", \"Single method/lab evidence for receptor autoregulation\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Linked a specific VIP receptor (VIP-1/VPAC1) coupled to adenylyl cyclase to cancer cell proliferation, and demonstrated evolutionary conservation of VIP receptor\\u2013cAMP coupling.\",\n      \"evidence\": \"Receptor expression analysis with cAMP/thymidine assays in pancreatic carcinoma cells; goldfish receptor heterologous expression in COS-7\",\n      \"pmids\": [\"9108448\", \"9038250\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor subtype assignment based on pharmacology, not direct cloning in human cells\", \"In vivo relevance to tumor growth not shown\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Extended VIP signaling beyond cAMP, showing receptor-dependent regulation of NO/cGMP in keratinocytes and cAMP-mediated suppression of macrophage TGF-\\u03b21, distinguishing VIP from PACAP downstream wiring.\",\n      \"evidence\": \"Receptor expression, cAMP/cGMP/NO measurements, proliferation assays; LPS-stimulated macrophage cytokine and mRNA analysis with pathway inhibitors\",\n      \"pmids\": [\"10858492\", \"10808055\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Differential signaling of the SNV analog mechanistically unexplained\", \"Single-lab cell-line systems\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Resolved the molecular pharmacology of VPAC1 and VPAC2, mapping ligand-interaction domains and demonstrating receptor desensitization/internalization, and defined VIP's anti-inflammatory program at the transcription-factor level.\",\n      \"evidence\": \"Site-directed mutagenesis, receptor chimeras, radioligand and cAMP assays; macrophage/T-cell transcription-factor reporter and EMSA assays\",\n      \"pmids\": [\"12529932\", \"12090463\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of receptor activation not solved\", \"Cell-type-specific differences in transcription-factor targeting unresolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Dissected the proximal signaling of VIP-induced smooth muscle relaxation (cAMP/PKA/AKAP/ryanodine receptor), identified Nurr1 as a direct transcriptional activator of VIP supporting dopaminergic survival, and showed endogenous VIP defends against airway hyperresponsiveness.\",\n      \"evidence\": \"Ca\\u00b2\\u207a imaging and patch-clamp with pathway inhibitors; promoter reporter and Nurr1 knockout with survival assay; VIP-knockout mice with methacholine challenge and rescue\",\n      \"pmids\": [\"16571863\", \"16999955\", \"16782752\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Tissue-specificity of AKAP-anchored PKA signaling not generalized\", \"Whether VIP loss contributes to human asthma not addressed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Established VIP/VPAC2 signaling as essential for SCN neuronal synchronization driving circadian and metabolic rhythms.\",\n      \"evidence\": \"VIP- and VPAC2-knockout mice with metabolic monitoring and behavioral recording under varying light conditions\",\n      \"pmids\": [\"18032467\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Intracellular pathway linking VPAC2 to clock gene expression not defined here\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Expanded VIP signaling to neuronal plasticity (cAMP/PKA enhancement of NMDA currents), nuclear/extranuclear receptor compartmentalization, and an autocrine/intracrine loop in cancer cells.\",\n      \"evidence\": \"Hippocampal patch-clamp with receptor pharmacology; subcellular fractionation and cAMP assay in breast cancer cells\",\n      \"pmids\": [\"20414742\", \"20691743\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional role of nuclear VPAC1 unresolved\", \"Mechanism of intracrine VIP delivery to nuclear receptors unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Revealed that VPAC1 and VPAC2 exert opposing effects on mucosal inflammation, with VPAC1/PKA driving colitis severity, refining VIP's net immune role as receptor-dependent.\",\n      \"evidence\": \"VPAC1- and VPAC2-knockout mice in DSS colitis with PKA inhibitor rescue and inflammatory marker quantification\",\n      \"pmids\": [\"21295288\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cellular targets of opposing receptor signals not pinpointed\", \"Reconciliation with anti-inflammatory VIP effects context-dependent\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified mTOR within VIP neurons as a molecular requirement for SCN circadian synchrony and olfactory sensory responses, providing an intracellular effector for VIP-neuron function.\",\n      \"evidence\": \"Conditional mTOR knockout in VIP-expressing cells with behavioral, SCN imaging, and olfactory readouts\",\n      \"pmids\": [\"29555746\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Link between mTOR and VIP peptide release not established\", \"Mechanism of mTOR activation by odor in VIP neurons unclear\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defined the enteric VIP\\u2013ILC3 circuit as a feeding-gated rheostat of innate immunity and lipid absorption, and established VIP interneurons as critical nodes in cortical and Rett-syndrome pathophysiology.\",\n      \"evidence\": \"In vivo chemogenetics, conditional ablation, ILC3-specific VIPR2 knockout, cytokine/histology; conditional Mecp2 deletion in VIP interneurons; caspase ablation of SCN VIP neurons\",\n      \"pmids\": [\"32050257\", \"32343226\", \"32536240\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Reconciliation of opposing VIPR2 effects on IL-22 across studies context-dependent\", \"Downstream effectors of VIP-interneuron dysfunction in Rett model not fully mapped\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated that enteric VIP neurons control epithelial \\u03b11,2-fucosylation via VIPR1/Erk1\\u20132\\u2013c-Fos, linking neuronal VIP output to microbiota composition and liver disease susceptibility.\",\n      \"evidence\": \"Vagotomy, chemogenetics, enteric neuron\\u2013organoid coculture, transcriptomics, pathway inhibitors in mice\",\n      \"pmids\": [\"36150396\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether fut2 induction is direct or relayed through other epithelial signals unresolved\", \"Human relevance of the VIP\\u2013fucosylation axis not tested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How VIP-precursor processing, receptor subtype selection (VPAC1 vs VPAC2), and downstream pathway choice (cAMP/PKA vs Ca\\u00b2\\u207a/PLC vs NO/cGMP) are integrated to produce opposing context-dependent outcomes in immunity and inflammation remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying model reconciling pro- and anti-inflammatory VIP actions\", \"Structural basis of biased receptor signaling not determined\", \"Tissue determinants of differential precursor processing unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [3, 4, 6]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [3, 4, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [6, 9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 4, 13]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 5, 26]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [14, 18, 19]},\n      {\"term_id\": \"R-HSA-9909396\", \"supporting_discovery_ids\": [14, 15, 16]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"VPAC1\", \"VPAC2\", \"VIPR1\", \"VIPR2\", \"PHI\", \"Nurr1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":8,"faith_total":8,"faith_pct":100.0}}