{"gene":"HCRTR1","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2008,"finding":"OX1R contains an immunoreceptor tyrosine-based inhibitory motif (ITIM) at Y358 that drives apoptosis in cancer cells. Orexin-induced apoptosis requires Gq protein coupling but is independent of phospholipase C activation; instead, Y358 phosphorylation recruits SHP-2 phosphatase. Mutation of Y358 to F abolished ITIM tyrosine phosphorylation, SHP-2 recruitment, and apoptosis, but not inositol phosphate formation or calcium signaling.","method":"Site-directed mutagenesis (Y358F), transfection in CHO cells, tyrosine phosphatase inhibitor (PAO), dominant-negative SHP-2, Gαq-null fibroblasts, phospholipase C inhibitor U-73122","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution in multiple cell types, active-site mutagenesis, and multiple orthogonal pharmacological tools in a single rigorous study","pmids":["18198212"],"is_preprint":false},{"year":2009,"finding":"OX1R also contains a functional immunoreceptor tyrosine-based switch motif (ITSM) at Y83 in the first intracellular loop that is mandatory for OX1R-mediated apoptosis. Mutation of Y83 to F abolished ITSM phosphorylation, SHP-2 recruitment, and apoptosis, without altering Gq-mediated inositol phosphate formation or calcium transients. A structural model showed ITSM and ITIM phosphotyrosines are spatially compatible with simultaneous interaction with both SH2 domains of SHP-2.","method":"Site-directed mutagenesis (Y83F), functional IP/calcium assays, SHP-2 recruitment assays, computational structural modeling of OX1R","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 1 / Strong — mutagenesis with multiple orthogonal functional readouts (apoptosis, IP formation, calcium, SHP-2 recruitment) plus structural modeling in one rigorous study","pmids":["19661287"],"is_preprint":false},{"year":2012,"finding":"OX1R drives apoptosis in colon cancer cells through a Gq protein-dependent but phospholipase C-independent mechanism: the freed Gq βγ dimer stimulates Src-tyrosine kinase, which phosphorylates the ITIM motifs in OX1R, leading to SHP-2 recruitment and activation, followed by cytochrome c release and caspase-3/7 activation.","method":"Review consolidating prior experimental data; downstream pathway shown by pharmacological and genetic perturbations in prior studies (Gq null cells, PLC inhibitors, SHP-2 dominant-negative, caspase assays)","journal":"British journal of pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic synthesis supported by multiple prior experimental papers from the same lab; single-group replication","pmids":["21627633"],"is_preprint":false},{"year":2018,"finding":"GHSR1a (ghrelin receptor) and OX1R form constitutive heterodimers, demonstrated by BRET, FRET, and co-immunoprecipitation. A peptide mimicking the 5th transmembrane domain of OX1R impaired heterodimer formation. In GHSR1a/OX1R heterodimer-expressing cells, ghrelin (but not orexin-A) shifted signaling from Gαq to Gαs, increasing cAMP and CREB reporter activity compared to GHSR1a alone.","method":"BRET, FRET, Co-IP, transmembrane peptide interference, cAMP assay, CRE-luciferase reporter","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple resonance energy transfer methods plus Co-IP and functional cAMP assays; single lab","pmids":["30065627"],"is_preprint":false},{"year":2019,"finding":"APJ (apelin receptor) and OX1R form a constitutive GPCR heterodimer. Both receptors co-internalize upon stimulation with their respective agonists (apelin-13 or orexin-A). In vitro transmembrane peptide interference experiments using BRET and immunostaining identified TM4 and TM5 of APJ as the interaction interface of the APJ-OX1R heterodimer; co-internalization was disrupted by these peptides.","method":"BRET, Co-IP, immunostaining, transmembrane peptide interference assays","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus BRET and functional co-internalization; single lab","pmids":["31668922"],"is_preprint":false},{"year":2015,"finding":"Computational modeling of OX1R using the OX2R crystal structure as template revealed two alternative binding modes for orexin-A peptide (C-terminus in binding pocket near Tyr6.48 and Gln3.32), differing by ~100° peptide rotation, both consistent with prior site-directed mutagenesis data.","method":"Homology modeling (based on OX2R, NTSR1, CXCR4 structures), ZDOCK/RDOCK docking of 4301 complexes, multidimensional scaling and clustering","journal":"BMC structural biology","confidence":"Low","confidence_rationale":"Tier 4 / Weak — computational prediction only, no experimental validation of the proposed binding modes","pmids":["25957175"],"is_preprint":false},{"year":2014,"finding":"Orexin-A protects rat hepatocytes from apoptosis via the OX1R/PI3K/AKT signaling pathway, inducing phosphorylation of FoxO1 and mTORC1. OX1R antagonist SB334867, AKT antagonist, FoxO1 inhibitor, and mTORC1 inhibitor each blocked these effects.","method":"RT-PCR, western blot, pharmacological inhibitors (SB334867, PF-04691502, AS1842856, everolimus), cell viability and apoptosis assays in primary rat hepatocytes","journal":"International journal of molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple pharmacological inhibitors at different pathway nodes with specific functional readouts; single lab","pmids":["24807827"],"is_preprint":false},{"year":2016,"finding":"Orexin-A promotes glutamate (Glu) uptake in astrocytes under anoxia/hypoglycemic conditions via OX1R, upregulating GLT-1 expression through a PKCα/ERK1/2 signaling cascade. OX1R antagonist reversed these effects; PKCα or ERK1/2 inhibitors constrained GLT-1 expression; GLT-1 overexpression rescued cells from the inhibitor-induced apoptosis.","method":"Pharmacological inhibitors (OX1R antagonist, PKCα inhibitor, ERK1/2 inhibitor), GLT-1 overexpression, western blot, Glu uptake assay in astrocytes under OGD conditions","journal":"Molecular and cellular biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis established through pharmacological cascade dissection and rescue experiment; single lab","pmids":["27837432"],"is_preprint":false},{"year":2020,"finding":"Orexin-A exerts neuroprotective effects in cerebral ischemia-reperfusion injury by suppressing over-activated autophagy through the OX1R-mediated MAPK/ERK/mTOR pathway, reducing neuronal apoptosis. OX1R was identified as the mediating receptor based on pathway protein levels (p-ERK1/2, p-mTOR, LC3B, Beclin-1, p62) in MCAO rats and OGD/R cells.","method":"Western blot, CCK8 cell viability, acridine orange staining (autophagic vacuoles), Hoechst/TUNEL apoptosis assays, MCAO rat model and OGD/R cell model","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal assays in parallel in vivo and in vitro models; single lab","pmids":["33212156"],"is_preprint":false},{"year":2021,"finding":"Orexin-A alleviates astrocytic apoptosis and inflammation in cerebral ischemia/reperfusion injury by inhibiting OX1R-mediated NF-κB and MAPK/ERK and MAPK/p38 signaling pathways, including suppression of nuclear translocation of NF-κB p65 and upregulation of Bcl-2/Bax ratio.","method":"Western blot, ELISA, Hoechst staining, immunofluorescence, TTC staining, MCAO/R rat model and OGD/R U251 cell model","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple signaling nodes assessed with orthogonal methods in parallel in vivo and in vitro; single lab","pmids":["34358627"],"is_preprint":false},{"year":2021,"finding":"Orexin-A potentiates glycine currents in spinal cord ventral horn neurons by activating OX1R via an IP3/intracellular Ca2+/PKC-dependent signaling pathway. Extracellular Ca2+ removal did not block the effect; chelation of intracellular Ca2+ with BAPTA or blockade of IP3 receptors (heparin, Xe-C) abolished it; PKC inhibitor (Bis-IV) nullified the effect; PKC activator (PMA) occluded the orexin-A effect.","method":"Patch-clamp electrophysiology in acutely isolated spinal neurons, OX1R antagonist (SB334867), Ca2+-free solution, BAPTA internal infusion, IP3 receptor antagonists, PKC inhibitor/activator","journal":"Brain research bulletin","confidence":"High","confidence_rationale":"Tier 1 / Strong — electrophysiological reconstitution with systematic pharmacological dissection of signaling cascade using multiple orthogonal tools","pmids":["33515654"],"is_preprint":false},{"year":2021,"finding":"Orexin-A inhibits GABA currents in spinal cord ventral horn neurons by activating both OX1R and OX2R via a Ca2+-independent PKC signaling pathway. Simultaneous blockade of OX1R and OX2R completely abolished the suppressive effect; separate blockade partially relieved it. PKC inhibitor (Bis-IV) abolished the effect; PKC activator (PMA) occluded it; Rp-cAMP (PKA inhibitor) did not affect it; Ca2+ chelation did not significantly change the effect.","method":"Patch-clamp electrophysiology, selective OX1R antagonist (SB334867) and OX2R antagonist (TCSOX229), PKC inhibitor/activator, PKA inhibitor, Ca2+ chelator BAPTA, Ca2+-free extracellular solution","journal":"Journal of Southern Medical University","confidence":"High","confidence_rationale":"Tier 1 / Strong — electrophysiological reconstitution with systematic dissection using receptor subtype-selective antagonists and signaling pathway inhibitors","pmids":["34134956"],"is_preprint":false},{"year":2018,"finding":"Orexin-A exerts neuroprotective effects on MPTP-treated parkinsonian mice via OX1R, increasing BDNF protein in dopaminergic neurons. The protective effects were blocked by OX1R antagonist SB334867. In SH-SY5Y cells, orexin-A induced BDNF upregulation via OX1R through PI3K and PKC signaling pathways.","method":"MPTP mouse model of PD, OX1R antagonist (SB334867), Western blot, immunohistochemistry, behavioral assays, pharmacological inhibitors of PI3K and PKC in SH-SY5Y cells","journal":"Frontiers in neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro pharmacological dissection with multiple readouts; single lab","pmids":["30524223"],"is_preprint":false},{"year":2023,"finding":"α-Synuclein physically interacts with OX1R and promotes OX1R degradation through both proteasomal and lysosomal pathways. Overexpression of α-Synuclein downregulated OX1R-mediated signaling and damaged orexin neurons. In vivo injection of α-Synuclein into the lateral hypothalamic area damaged orexin neurons and induced RBD-like sleep patterns.","method":"Co-immunoprecipitation (interaction), proteasome/lysosome inhibitor experiments (degradation pathway), lentiviral overexpression, in vivo stereotaxic injection, sleep pattern analysis, western blot","journal":"Neuromolecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP interaction plus mechanistic degradation pathway analysis with proteasome/lysosome inhibitors; single lab","pmids":["36689149"],"is_preprint":false},{"year":2023,"finding":"Orexin-A/OX1R activates the mTOR/p70S6K1 pathway to inhibit autophagy in adrenocortical cells (H295R and Y-1), and this autophagy suppression promotes cortisol secretion by increasing expression of 3β-hydroxysteroid dehydrogenase/isomerase.","method":"Transmission electron microscopy (autophagosomes), western blot (LC3, p62, mTOR, p70S6K1), ELISA (cortisol), OX1R antagonist and mTOR inhibitor treatments in adrenocortical cell lines","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods linking OX1R to defined mTOR pathway and steroidogenesis endpoint; single lab","pmids":["37572990"],"is_preprint":false},{"year":2021,"finding":"Cannabidiol (CBD) acts as a selective antagonist at OX1R (Ki ~1.58 μM) with no significant binding at OX2R. In vitro functional assays (intracellular calcium imaging and mobilization) confirmed CBD antagonism at OX1R. Molecular docking rationalized the OX1R subtype selectivity at the molecular level.","method":"Radioligand binding assay (Ki determination), intracellular calcium imaging, calcium mobilization assay, molecular docking and molecular dynamics","journal":"Biomolecules","confidence":"Medium","confidence_rationale":"Tier 1–2 / Moderate — in vitro binding and functional antagonism assays with computational binding mode rationalization; single lab","pmids":["34439801"],"is_preprint":false},{"year":2009,"finding":"OX1R in the rostral medullary raphe contributes to the hypercapnic chemoreflex specifically during wakefulness in the dark (active) period in rats. Focal OX1R antagonism by microdialysis of SB-334867 into the rostral medullary raphe caused a 16% reduction in CO2-induced hyperventilation during wakefulness in the dark period, with no effect during NREM sleep or in the light period.","method":"Microdialysis of selective OX1R antagonist (SB-334867) into rostral medullary raphe, ventilation measurement in air and 7% CO2, state-dependent analysis (wakefulness vs. sleep, dark vs. light period)","journal":"Respiratory physiology & neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — focal pharmacological blockade with state-dependent and anatomical controls; single lab","pmids":["19995618"],"is_preprint":false},{"year":2011,"finding":"Hcrtr1 signaling specifically promotes depression-like behavioral despair: Hcrtr1-null mice showed significantly reduced behavioral despair in forced swim and tail suspension tests, and wild-type mice treated with OX1R antagonist SB-334867 recapitulated this effect. No anxiety-like behavior difference was noted with hcrtr1 deletion, in contrast to hcrtr2-null mice which showed increased behavioral despair.","method":"Genetic knockout (Hcrtr1-null mice), pharmacological antagonism (SB-334867), forced swim test, tail suspension test, anxiety-like behavior assays","journal":"Behavioural brain research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and pharmacological convergence on the same behavioral phenotype with receptor subtype specificity established by parallel hcrtr2 null comparison","pmids":["21377495"],"is_preprint":false},{"year":2018,"finding":"OX1R is ectopically expressed in ulcerative colitis-affected colonic epithelium and mediates the anti-inflammatory effect of orexin-A. Injection of orexin-A improved inflammatory symptoms in two colitis murine models, while an inactive orexin-A analog, OX1R-specific antagonist SB-408124, or treatment of OX1R knockout mice with orexin-A had no protective effect. Orexin-A decreased pro-inflammatory cytokines in immune cells, particularly T-cells, and inhibited canonical NF-κB activation.","method":"Immunohistochemistry (OX1R expression in UC), two colitis mouse models (DSS), OX1R knockout mice, OX1R antagonist (SB-408124), inactive analog control, cytokine assays, NF-κB activation assay","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic (OX1R KO) and pharmacological approaches with multiple controls converging on OX1R as necessary mediator; single lab","pmids":["30251681"],"is_preprint":false},{"year":2025,"finding":"OX1R-specific loss in dopaminergic VTA neurons (DA-Ox1R-KO mice) abolished the excitatory response of DA VTA cells to OXA (orexin-A), demonstrating that OXA enhances DA VTA neuronal excitability specifically through OX1R. DA-Ox1R-KO mice displayed anxiety-like behavior and context-dependent hyperactivity, placing OX1R signaling in DA neurons upstream of these behavioral outputs.","method":"Conditional genetic knockout (Hcrtr1 selectively deleted in DA cells), patch-clamp electrophysiology of VTA DA neurons, behavioral phenotyping","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific genetic knockout with electrophysiological validation of receptor function loss; preprint, single lab","pmids":["bio_10.1101_2025.02.14.638329"],"is_preprint":true},{"year":2024,"finding":"Optical stimulation of lateral hypothalamic orexin/dynorphin (LH-ox/dyn) inputs in the VTA activates DA VTA neurons via Ox1R signaling. The diverse firing responses of VTA DA neurons to LH optical stimulation were blocked by Ox1R antagonism (alongside KOR blockade), and projection-specific effects were observed: LH ox/dyn input inhibited BLA-projecting DA neurons (dynorphin predominating via KOR) and bidirectionally modulated nucleus accumbens-projecting DA neurons sensitive to both Ox1R and KOR.","method":"Optogenetics, patch-clamp electrophysiology, circuit tracing, pharmacological blockade of Ox1R and KOR in orexin-Cre mice","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — circuit-specific optogenetic stimulation with electrophysiology and receptor pharmacology; preprint, single lab","pmids":["bio_10.1101_2024.08.01.606179"],"is_preprint":true},{"year":2025,"finding":"OX1R in the paraventricular nucleus (PVN) contributes to SF-induced aggravation of myocardial ischemia-reperfusion injury via sympathetic hyperactivation. PVN OX1R expression was upregulated by sleep fragmentation. Pharmacological blockade of OX1R in the PVN with SB-334867 (stereotaxic injection) significantly ameliorated cardiac dysfunction, reduced infarct size, and suppressed sympathetic hyperactivity.","method":"Stereotaxic OX1R antagonist (SB-334867) injection into PVN, echocardiography, heart rate variability analysis, western blot, qRT-PCR, immunohistochemistry in SF mouse model","journal":"Annals of medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — focal pharmacological blockade in a specific brain region with multiple cardiovascular readouts; single lab","pmids":["41369031"],"is_preprint":false},{"year":2024,"finding":"CRF neuron-specific deletion of HcrtR1 (OX1R) significantly reduced alcohol intake in mice, with sex-specific effects on BNST excitability during protracted withdrawal. These genetic epistasis experiments place HcrtR1 signaling in CRF neurons upstream of excessive alcohol consumption behavior.","method":"Conditional genetic knockout (HcrtR1 deleted specifically in CRF neurons), alcohol drinking assays, patch-clamp electrophysiology (BNST excitability), anxiety behavioral tests, sex-specific analysis","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific genetic epistasis with electrophysiological and behavioral phenotyping; preprint, single lab","pmids":["bio_10.1101_2024.09.07.609774"],"is_preprint":true}],"current_model":"HCRTR1 (OX1R) is a Gq-coupled GPCR that mediates diverse downstream signaling: canonical Gq activation drives IP3/Ca2+/PKC-dependent modulation of ion channels (potentiating glycine currents and inhibiting GABA currents in spinal neurons); a non-canonical pathway uses Gq βγ to activate Src kinase, phosphorylating two immunoreceptor tyrosine-based motifs (ITIM at Y358 and ITSM at Y83) in OX1R, which recruits and activates SHP-2 phosphatase to trigger mitochondrial apoptosis (cytochrome c release, caspase-3/7 activation) in cancer cells; OX1R additionally signals through PI3K/AKT, MAPK/ERK, and mTOR pathways to regulate autophagy, cell survival, and steroidogenesis; OX1R forms functional heterodimers with GHSR1a and APJ that alter downstream G protein coupling; OX1R in specific brain nuclei (VTA dopamine neurons, PVN, medullary raphe, BNST CRF neurons) contributes to arousal, mood, cardiovascular regulation, and addiction-related behaviors; and α-synuclein interacts directly with OX1R to promote its proteasomal and lysosomal degradation."},"narrative":{"mechanistic_narrative":"HCRTR1 (OX1R) is a Gq-coupled G protein-coupled receptor for orexin-A that transduces ligand binding into divergent signaling outputs controlling neuronal excitability, cell survival, autophagy, and behavior [PMID:18198212, PMID:33515654]. Canonical Gq signaling drives an IP3/intracellular Ca2+/PKC cascade that modulates ion channels in spinal ventral horn neurons, potentiating glycine currents [PMID:33515654] and, together with OX2R via a Ca2+-independent PKC route, suppressing GABA currents [PMID:34134956]. In parallel, OX1R executes a non-canonical, phospholipase C-independent death pathway: freed Gq βγ activates Src, which phosphorylates an ITIM at Y358 and an ITSM at Y83 in the receptor's intracellular regions, recruiting SHP-2 to trigger cytochrome c release and caspase-3/7 activation in cancer cells [PMID:18198212, PMID:19661287, PMID:21627633]. Beyond these, OX1R engages PI3K/AKT, MAPK/ERK, and mTOR/p70S6K1 cascades to control cell survival, autophagy, and steroidogenesis—protecting hepatocytes and neurons from apoptosis [PMID:24807827, PMID:33212156], suppressing autophagy to promote cortisol secretion in adrenocortical cells [PMID:37572990], and limiting inflammatory NF-κB signaling [PMID:34358627, PMID:30251681]. OX1R forms constitutive heterodimers with GHSR1a and APJ that reshape its G protein coupling and trafficking [PMID:30065627, PMID:31668922]. In the CNS, OX1R signaling in defined nuclei contributes to behavioral despair [PMID:21377495], VTA dopamine neuron excitability and associated anxiety/addiction phenotypes [PMID:bio_10.1101_2025.02.14.638329, PMID:bio_10.1101_2024.09.07.609774], and cardiorespiratory regulation [PMID:19995618, PMID:41369031]. α-Synuclein binds OX1R directly and promotes its proteasomal and lysosomal degradation, linking receptor turnover to orexin neuron dysfunction [PMID:36689149].","teleology":[{"year":2008,"claim":"Established that OX1R signals to apoptosis through a previously unrecognized tyrosine-based motif rather than its canonical Ca2+ pathway, redefining the receptor as a death-signaling GPCR in cancer.","evidence":"Y358F mutagenesis, transfection in CHO cells, Gαq-null fibroblasts, PLC inhibitor, dominant-negative SHP-2","pmids":["18198212"],"confidence":"High","gaps":["Did not identify the upstream tyrosine kinase phosphorylating Y358","Generality across non-cancer cell types untested"]},{"year":2009,"claim":"Showed that a second motif (ITSM Y83) is co-required with the ITIM, defining a bipartite phosphotyrosine docking site for both SHP-2 SH2 domains and clarifying how the receptor engages the phosphatase.","evidence":"Y83F mutagenesis, IP/calcium and SHP-2 recruitment assays, computational structural modeling","pmids":["19661287"],"confidence":"High","gaps":["Structural model not experimentally validated","Stoichiometry of OX1R-SHP-2 binding not directly measured"]},{"year":2012,"claim":"Consolidated the death pathway by identifying Gq βγ-activated Src as the kinase upstream of ITIM phosphorylation in colon cancer, completing a receptor-to-mitochondria signaling chain.","evidence":"Review synthesizing Gq-null cell, PLC inhibitor, dominant-negative SHP-2 and caspase data","pmids":["21627633"],"confidence":"Medium","gaps":["Single-group synthesis without independent replication","Direct demonstration that βγ-Src acts on OX1R in situ limited"]},{"year":2014,"claim":"Demonstrated that OX1R can also be pro-survival via PI3K/AKT-FoxO1-mTORC1, establishing context-dependence of orexin signaling outcomes.","evidence":"Pharmacological inhibitors at multiple pathway nodes in primary rat hepatocytes","pmids":["24807827"],"confidence":"Medium","gaps":["Did not reconcile pro-survival vs pro-apoptotic outcomes mechanistically","Single tissue context"]},{"year":2015,"claim":"Provided a structural hypothesis for orexin-A engagement of OX1R, proposing alternative binding modes consistent with mutagenesis.","evidence":"Homology modeling on OX2R/NTSR1/CXCR4 templates with docking and clustering","pmids":["25957175"],"confidence":"Low","gaps":["Computational only; no experimental validation of binding modes","Cannot distinguish which mode is functional"]},{"year":2018,"claim":"Showed that OX1R does not signal in isolation but forms a constitutive heterodimer with GHSR1a that reprograms G protein coupling toward Gs/cAMP, expanding the receptor's signaling repertoire.","evidence":"BRET, FRET, Co-IP, TM5 peptide interference, cAMP and CRE-luciferase assays","pmids":["30065627"],"confidence":"Medium","gaps":["In vivo relevance of heterodimer not established","Single lab"]},{"year":2019,"claim":"Extended heterodimerization to APJ, defining the TM4/TM5 interface and showing co-internalization, indicating combinatorial regulation of OX1R trafficking.","evidence":"BRET, reciprocal Co-IP, immunostaining, TM peptide interference","pmids":["31668922"],"confidence":"Medium","gaps":["Functional signaling consequences of APJ-OX1R heterodimer not quantified","Single lab"]},{"year":2021,"claim":"Dissected the canonical OX1R cascade in native spinal neurons, showing IP3/intracellular Ca2+/PKC potentiates glycine currents while a Ca2+-independent PKC route (OX1R+OX2R) inhibits GABA currents, mapping receptor coupling to specific inhibitory neurotransmission.","evidence":"Patch-clamp with subtype-selective antagonists, Ca2+ chelation, IP3R and PKC inhibitors/activators","pmids":["33515654","34134956"],"confidence":"High","gaps":["Target ion channels not molecularly identified","PKC isoform specificity not resolved"]},{"year":2021,"claim":"Established OX1R as a neuroprotective/anti-inflammatory node in cerebral ischemia via MAPK/ERK/mTOR control of autophagy and NF-κB/MAPK suppression, broadening its physiological roles.","evidence":"Western blot, viability/apoptosis assays in MCAO/R rat and OGD/R cell models with OX1R antagonism","pmids":["33212156","34358627"],"confidence":"Medium","gaps":["Receptor assignment based largely on pathway readouts and antagonist","No genetic loss-of-function in these models"]},{"year":2023,"claim":"Identified α-synuclein as a direct binding partner that drives OX1R degradation through proteasomal and lysosomal routes, linking receptor turnover to orexin neuron loss and sleep pathology.","evidence":"Co-IP, proteasome/lysosome inhibitors, lentiviral overexpression, in vivo LHA injection, sleep analysis","pmids":["36689149"],"confidence":"Medium","gaps":["Binding interface on OX1R not mapped","E3 ligase mediating degradation unknown"]},{"year":2023,"claim":"Connected OX1R-mTOR/p70S6K1 autophagy suppression to steroidogenesis, showing the receptor regulates cortisol output via 3β-HSD induction.","evidence":"TEM, western blot, ELISA with OX1R and mTOR inhibitors in adrenocortical lines","pmids":["37572990"],"confidence":"Medium","gaps":["Causal link between autophagy and 3β-HSD not fully isolated","Single lab"]},{"year":2024,"claim":"Used cell-type-specific deletion to place OX1R signaling in CRF neurons upstream of excessive alcohol consumption and BNST excitability, establishing circuit-level behavioral causality.","evidence":"Conditional HcrtR1 KO in CRF neurons, drinking assays, BNST patch-clamp (preprint)","pmids":["bio_10.1101_2024.09.07.609774"],"confidence":"Medium","gaps":["Preprint, single lab","Sex-specific mechanism not resolved"]},{"year":2025,"claim":"Demonstrated that OX1R mediates orexin-A excitation of VTA dopamine neurons and is required for normal anxiety and activity behaviors, anchoring the receptor in dopaminergic circuit function.","evidence":"DA-cell-specific Hcrtr1 KO, VTA patch-clamp, behavioral phenotyping; LH ox/dyn optogenetics (preprints)","pmids":["bio_10.1101_2025.02.14.638329","bio_10.1101_2024.08.01.606179"],"confidence":"Medium","gaps":["Preprints, single lab","Downstream effectors of DA neuron excitation not defined"]},{"year":null,"claim":"How OX1R selects between pro-apoptotic (Src/SHP-2), pro-survival (PI3K/AKT), and canonical Ca2+/PKC outputs in a cell-context-dependent manner remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying model linking ligand/cofactor context to pathway choice","Heterodimer contribution to output selection in vivo unknown","No experimental high-resolution structure of OX1R complexes in the corpus"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,10,11]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[0,15]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[3,4]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,3,4]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,10,11]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,2,6]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[8,14]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[10,11,19]}],"complexes":["GHSR1a-OX1R heterodimer","APJ-OX1R heterodimer"],"partners":["SHP-2","SRC","GHSR1A","APJ","SNCA"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O43613","full_name":"Orexin/Hypocretin receptor type 1","aliases":["Hypocretin receptor type 1","Orexin receptor type 1","Ox-1-R","Ox1-R","Ox1R"],"length_aa":425,"mass_kda":47.5,"function":"G-protein coupled receptor that binds the neuropeptide orexin-A with high affinity, and orexin-B with lower affinity, two peptides derived from a common precursor, prepro-orexin (PubMed:32669442, PubMed:9491897). Its activity is mediated via a G(q)-protein-coupled pathway, which activates the phosphatidylinositol-calcium second messenger system in response to orexin-A binding (PubMed:32669442). In addition to G(q)-mediated signaling, orexin-A stimulation also promotes beta-arrestin recruitment, leading to receptor internalization (PubMed:15683363, PubMed:32669442). 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Orexin-induced apoptosis requires Gq protein coupling but is independent of phospholipase C activation; instead, Y358 phosphorylation recruits SHP-2 phosphatase. Mutation of Y358 to F abolished ITIM tyrosine phosphorylation, SHP-2 recruitment, and apoptosis, but not inositol phosphate formation or calcium signaling.\",\n      \"method\": \"Site-directed mutagenesis (Y358F), transfection in CHO cells, tyrosine phosphatase inhibitor (PAO), dominant-negative SHP-2, Gαq-null fibroblasts, phospholipase C inhibitor U-73122\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution in multiple cell types, active-site mutagenesis, and multiple orthogonal pharmacological tools in a single rigorous study\",\n      \"pmids\": [\"18198212\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"OX1R also contains a functional immunoreceptor tyrosine-based switch motif (ITSM) at Y83 in the first intracellular loop that is mandatory for OX1R-mediated apoptosis. Mutation of Y83 to F abolished ITSM phosphorylation, SHP-2 recruitment, and apoptosis, without altering Gq-mediated inositol phosphate formation or calcium transients. A structural model showed ITSM and ITIM phosphotyrosines are spatially compatible with simultaneous interaction with both SH2 domains of SHP-2.\",\n      \"method\": \"Site-directed mutagenesis (Y83F), functional IP/calcium assays, SHP-2 recruitment assays, computational structural modeling of OX1R\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — mutagenesis with multiple orthogonal functional readouts (apoptosis, IP formation, calcium, SHP-2 recruitment) plus structural modeling in one rigorous study\",\n      \"pmids\": [\"19661287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"OX1R drives apoptosis in colon cancer cells through a Gq protein-dependent but phospholipase C-independent mechanism: the freed Gq βγ dimer stimulates Src-tyrosine kinase, which phosphorylates the ITIM motifs in OX1R, leading to SHP-2 recruitment and activation, followed by cytochrome c release and caspase-3/7 activation.\",\n      \"method\": \"Review consolidating prior experimental data; downstream pathway shown by pharmacological and genetic perturbations in prior studies (Gq null cells, PLC inhibitors, SHP-2 dominant-negative, caspase assays)\",\n      \"journal\": \"British journal of pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic synthesis supported by multiple prior experimental papers from the same lab; single-group replication\",\n      \"pmids\": [\"21627633\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"GHSR1a (ghrelin receptor) and OX1R form constitutive heterodimers, demonstrated by BRET, FRET, and co-immunoprecipitation. A peptide mimicking the 5th transmembrane domain of OX1R impaired heterodimer formation. In GHSR1a/OX1R heterodimer-expressing cells, ghrelin (but not orexin-A) shifted signaling from Gαq to Gαs, increasing cAMP and CREB reporter activity compared to GHSR1a alone.\",\n      \"method\": \"BRET, FRET, Co-IP, transmembrane peptide interference, cAMP assay, CRE-luciferase reporter\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple resonance energy transfer methods plus Co-IP and functional cAMP assays; single lab\",\n      \"pmids\": [\"30065627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"APJ (apelin receptor) and OX1R form a constitutive GPCR heterodimer. Both receptors co-internalize upon stimulation with their respective agonists (apelin-13 or orexin-A). In vitro transmembrane peptide interference experiments using BRET and immunostaining identified TM4 and TM5 of APJ as the interaction interface of the APJ-OX1R heterodimer; co-internalization was disrupted by these peptides.\",\n      \"method\": \"BRET, Co-IP, immunostaining, transmembrane peptide interference assays\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus BRET and functional co-internalization; single lab\",\n      \"pmids\": [\"31668922\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Computational modeling of OX1R using the OX2R crystal structure as template revealed two alternative binding modes for orexin-A peptide (C-terminus in binding pocket near Tyr6.48 and Gln3.32), differing by ~100° peptide rotation, both consistent with prior site-directed mutagenesis data.\",\n      \"method\": \"Homology modeling (based on OX2R, NTSR1, CXCR4 structures), ZDOCK/RDOCK docking of 4301 complexes, multidimensional scaling and clustering\",\n      \"journal\": \"BMC structural biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — computational prediction only, no experimental validation of the proposed binding modes\",\n      \"pmids\": [\"25957175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Orexin-A protects rat hepatocytes from apoptosis via the OX1R/PI3K/AKT signaling pathway, inducing phosphorylation of FoxO1 and mTORC1. OX1R antagonist SB334867, AKT antagonist, FoxO1 inhibitor, and mTORC1 inhibitor each blocked these effects.\",\n      \"method\": \"RT-PCR, western blot, pharmacological inhibitors (SB334867, PF-04691502, AS1842856, everolimus), cell viability and apoptosis assays in primary rat hepatocytes\",\n      \"journal\": \"International journal of molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple pharmacological inhibitors at different pathway nodes with specific functional readouts; single lab\",\n      \"pmids\": [\"24807827\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Orexin-A promotes glutamate (Glu) uptake in astrocytes under anoxia/hypoglycemic conditions via OX1R, upregulating GLT-1 expression through a PKCα/ERK1/2 signaling cascade. OX1R antagonist reversed these effects; PKCα or ERK1/2 inhibitors constrained GLT-1 expression; GLT-1 overexpression rescued cells from the inhibitor-induced apoptosis.\",\n      \"method\": \"Pharmacological inhibitors (OX1R antagonist, PKCα inhibitor, ERK1/2 inhibitor), GLT-1 overexpression, western blot, Glu uptake assay in astrocytes under OGD conditions\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis established through pharmacological cascade dissection and rescue experiment; single lab\",\n      \"pmids\": [\"27837432\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Orexin-A exerts neuroprotective effects in cerebral ischemia-reperfusion injury by suppressing over-activated autophagy through the OX1R-mediated MAPK/ERK/mTOR pathway, reducing neuronal apoptosis. OX1R was identified as the mediating receptor based on pathway protein levels (p-ERK1/2, p-mTOR, LC3B, Beclin-1, p62) in MCAO rats and OGD/R cells.\",\n      \"method\": \"Western blot, CCK8 cell viability, acridine orange staining (autophagic vacuoles), Hoechst/TUNEL apoptosis assays, MCAO rat model and OGD/R cell model\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal assays in parallel in vivo and in vitro models; single lab\",\n      \"pmids\": [\"33212156\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Orexin-A alleviates astrocytic apoptosis and inflammation in cerebral ischemia/reperfusion injury by inhibiting OX1R-mediated NF-κB and MAPK/ERK and MAPK/p38 signaling pathways, including suppression of nuclear translocation of NF-κB p65 and upregulation of Bcl-2/Bax ratio.\",\n      \"method\": \"Western blot, ELISA, Hoechst staining, immunofluorescence, TTC staining, MCAO/R rat model and OGD/R U251 cell model\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple signaling nodes assessed with orthogonal methods in parallel in vivo and in vitro; single lab\",\n      \"pmids\": [\"34358627\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Orexin-A potentiates glycine currents in spinal cord ventral horn neurons by activating OX1R via an IP3/intracellular Ca2+/PKC-dependent signaling pathway. Extracellular Ca2+ removal did not block the effect; chelation of intracellular Ca2+ with BAPTA or blockade of IP3 receptors (heparin, Xe-C) abolished it; PKC inhibitor (Bis-IV) nullified the effect; PKC activator (PMA) occluded the orexin-A effect.\",\n      \"method\": \"Patch-clamp electrophysiology in acutely isolated spinal neurons, OX1R antagonist (SB334867), Ca2+-free solution, BAPTA internal infusion, IP3 receptor antagonists, PKC inhibitor/activator\",\n      \"journal\": \"Brain research bulletin\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — electrophysiological reconstitution with systematic pharmacological dissection of signaling cascade using multiple orthogonal tools\",\n      \"pmids\": [\"33515654\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Orexin-A inhibits GABA currents in spinal cord ventral horn neurons by activating both OX1R and OX2R via a Ca2+-independent PKC signaling pathway. Simultaneous blockade of OX1R and OX2R completely abolished the suppressive effect; separate blockade partially relieved it. PKC inhibitor (Bis-IV) abolished the effect; PKC activator (PMA) occluded it; Rp-cAMP (PKA inhibitor) did not affect it; Ca2+ chelation did not significantly change the effect.\",\n      \"method\": \"Patch-clamp electrophysiology, selective OX1R antagonist (SB334867) and OX2R antagonist (TCSOX229), PKC inhibitor/activator, PKA inhibitor, Ca2+ chelator BAPTA, Ca2+-free extracellular solution\",\n      \"journal\": \"Journal of Southern Medical University\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — electrophysiological reconstitution with systematic dissection using receptor subtype-selective antagonists and signaling pathway inhibitors\",\n      \"pmids\": [\"34134956\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Orexin-A exerts neuroprotective effects on MPTP-treated parkinsonian mice via OX1R, increasing BDNF protein in dopaminergic neurons. The protective effects were blocked by OX1R antagonist SB334867. In SH-SY5Y cells, orexin-A induced BDNF upregulation via OX1R through PI3K and PKC signaling pathways.\",\n      \"method\": \"MPTP mouse model of PD, OX1R antagonist (SB334867), Western blot, immunohistochemistry, behavioral assays, pharmacological inhibitors of PI3K and PKC in SH-SY5Y cells\",\n      \"journal\": \"Frontiers in neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro pharmacological dissection with multiple readouts; single lab\",\n      \"pmids\": [\"30524223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"α-Synuclein physically interacts with OX1R and promotes OX1R degradation through both proteasomal and lysosomal pathways. Overexpression of α-Synuclein downregulated OX1R-mediated signaling and damaged orexin neurons. In vivo injection of α-Synuclein into the lateral hypothalamic area damaged orexin neurons and induced RBD-like sleep patterns.\",\n      \"method\": \"Co-immunoprecipitation (interaction), proteasome/lysosome inhibitor experiments (degradation pathway), lentiviral overexpression, in vivo stereotaxic injection, sleep pattern analysis, western blot\",\n      \"journal\": \"Neuromolecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP interaction plus mechanistic degradation pathway analysis with proteasome/lysosome inhibitors; single lab\",\n      \"pmids\": [\"36689149\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Orexin-A/OX1R activates the mTOR/p70S6K1 pathway to inhibit autophagy in adrenocortical cells (H295R and Y-1), and this autophagy suppression promotes cortisol secretion by increasing expression of 3β-hydroxysteroid dehydrogenase/isomerase.\",\n      \"method\": \"Transmission electron microscopy (autophagosomes), western blot (LC3, p62, mTOR, p70S6K1), ELISA (cortisol), OX1R antagonist and mTOR inhibitor treatments in adrenocortical cell lines\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods linking OX1R to defined mTOR pathway and steroidogenesis endpoint; single lab\",\n      \"pmids\": [\"37572990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Cannabidiol (CBD) acts as a selective antagonist at OX1R (Ki ~1.58 μM) with no significant binding at OX2R. In vitro functional assays (intracellular calcium imaging and mobilization) confirmed CBD antagonism at OX1R. Molecular docking rationalized the OX1R subtype selectivity at the molecular level.\",\n      \"method\": \"Radioligand binding assay (Ki determination), intracellular calcium imaging, calcium mobilization assay, molecular docking and molecular dynamics\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — in vitro binding and functional antagonism assays with computational binding mode rationalization; single lab\",\n      \"pmids\": [\"34439801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"OX1R in the rostral medullary raphe contributes to the hypercapnic chemoreflex specifically during wakefulness in the dark (active) period in rats. Focal OX1R antagonism by microdialysis of SB-334867 into the rostral medullary raphe caused a 16% reduction in CO2-induced hyperventilation during wakefulness in the dark period, with no effect during NREM sleep or in the light period.\",\n      \"method\": \"Microdialysis of selective OX1R antagonist (SB-334867) into rostral medullary raphe, ventilation measurement in air and 7% CO2, state-dependent analysis (wakefulness vs. sleep, dark vs. light period)\",\n      \"journal\": \"Respiratory physiology & neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — focal pharmacological blockade with state-dependent and anatomical controls; single lab\",\n      \"pmids\": [\"19995618\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Hcrtr1 signaling specifically promotes depression-like behavioral despair: Hcrtr1-null mice showed significantly reduced behavioral despair in forced swim and tail suspension tests, and wild-type mice treated with OX1R antagonist SB-334867 recapitulated this effect. No anxiety-like behavior difference was noted with hcrtr1 deletion, in contrast to hcrtr2-null mice which showed increased behavioral despair.\",\n      \"method\": \"Genetic knockout (Hcrtr1-null mice), pharmacological antagonism (SB-334867), forced swim test, tail suspension test, anxiety-like behavior assays\",\n      \"journal\": \"Behavioural brain research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and pharmacological convergence on the same behavioral phenotype with receptor subtype specificity established by parallel hcrtr2 null comparison\",\n      \"pmids\": [\"21377495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"OX1R is ectopically expressed in ulcerative colitis-affected colonic epithelium and mediates the anti-inflammatory effect of orexin-A. Injection of orexin-A improved inflammatory symptoms in two colitis murine models, while an inactive orexin-A analog, OX1R-specific antagonist SB-408124, or treatment of OX1R knockout mice with orexin-A had no protective effect. Orexin-A decreased pro-inflammatory cytokines in immune cells, particularly T-cells, and inhibited canonical NF-κB activation.\",\n      \"method\": \"Immunohistochemistry (OX1R expression in UC), two colitis mouse models (DSS), OX1R knockout mice, OX1R antagonist (SB-408124), inactive analog control, cytokine assays, NF-κB activation assay\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic (OX1R KO) and pharmacological approaches with multiple controls converging on OX1R as necessary mediator; single lab\",\n      \"pmids\": [\"30251681\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"OX1R-specific loss in dopaminergic VTA neurons (DA-Ox1R-KO mice) abolished the excitatory response of DA VTA cells to OXA (orexin-A), demonstrating that OXA enhances DA VTA neuronal excitability specifically through OX1R. DA-Ox1R-KO mice displayed anxiety-like behavior and context-dependent hyperactivity, placing OX1R signaling in DA neurons upstream of these behavioral outputs.\",\n      \"method\": \"Conditional genetic knockout (Hcrtr1 selectively deleted in DA cells), patch-clamp electrophysiology of VTA DA neurons, behavioral phenotyping\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific genetic knockout with electrophysiological validation of receptor function loss; preprint, single lab\",\n      \"pmids\": [\"bio_10.1101_2025.02.14.638329\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Optical stimulation of lateral hypothalamic orexin/dynorphin (LH-ox/dyn) inputs in the VTA activates DA VTA neurons via Ox1R signaling. The diverse firing responses of VTA DA neurons to LH optical stimulation were blocked by Ox1R antagonism (alongside KOR blockade), and projection-specific effects were observed: LH ox/dyn input inhibited BLA-projecting DA neurons (dynorphin predominating via KOR) and bidirectionally modulated nucleus accumbens-projecting DA neurons sensitive to both Ox1R and KOR.\",\n      \"method\": \"Optogenetics, patch-clamp electrophysiology, circuit tracing, pharmacological blockade of Ox1R and KOR in orexin-Cre mice\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — circuit-specific optogenetic stimulation with electrophysiology and receptor pharmacology; preprint, single lab\",\n      \"pmids\": [\"bio_10.1101_2024.08.01.606179\"],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"OX1R in the paraventricular nucleus (PVN) contributes to SF-induced aggravation of myocardial ischemia-reperfusion injury via sympathetic hyperactivation. PVN OX1R expression was upregulated by sleep fragmentation. Pharmacological blockade of OX1R in the PVN with SB-334867 (stereotaxic injection) significantly ameliorated cardiac dysfunction, reduced infarct size, and suppressed sympathetic hyperactivity.\",\n      \"method\": \"Stereotaxic OX1R antagonist (SB-334867) injection into PVN, echocardiography, heart rate variability analysis, western blot, qRT-PCR, immunohistochemistry in SF mouse model\",\n      \"journal\": \"Annals of medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — focal pharmacological blockade in a specific brain region with multiple cardiovascular readouts; single lab\",\n      \"pmids\": [\"41369031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CRF neuron-specific deletion of HcrtR1 (OX1R) significantly reduced alcohol intake in mice, with sex-specific effects on BNST excitability during protracted withdrawal. These genetic epistasis experiments place HcrtR1 signaling in CRF neurons upstream of excessive alcohol consumption behavior.\",\n      \"method\": \"Conditional genetic knockout (HcrtR1 deleted specifically in CRF neurons), alcohol drinking assays, patch-clamp electrophysiology (BNST excitability), anxiety behavioral tests, sex-specific analysis\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific genetic epistasis with electrophysiological and behavioral phenotyping; preprint, single lab\",\n      \"pmids\": [\"bio_10.1101_2024.09.07.609774\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"HCRTR1 (OX1R) is a Gq-coupled GPCR that mediates diverse downstream signaling: canonical Gq activation drives IP3/Ca2+/PKC-dependent modulation of ion channels (potentiating glycine currents and inhibiting GABA currents in spinal neurons); a non-canonical pathway uses Gq βγ to activate Src kinase, phosphorylating two immunoreceptor tyrosine-based motifs (ITIM at Y358 and ITSM at Y83) in OX1R, which recruits and activates SHP-2 phosphatase to trigger mitochondrial apoptosis (cytochrome c release, caspase-3/7 activation) in cancer cells; OX1R additionally signals through PI3K/AKT, MAPK/ERK, and mTOR pathways to regulate autophagy, cell survival, and steroidogenesis; OX1R forms functional heterodimers with GHSR1a and APJ that alter downstream G protein coupling; OX1R in specific brain nuclei (VTA dopamine neurons, PVN, medullary raphe, BNST CRF neurons) contributes to arousal, mood, cardiovascular regulation, and addiction-related behaviors; and α-synuclein interacts directly with OX1R to promote its proteasomal and lysosomal degradation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"HCRTR1 (OX1R) is a Gq-coupled G protein-coupled receptor for orexin-A that transduces ligand binding into divergent signaling outputs controlling neuronal excitability, cell survival, autophagy, and behavior [#0, #10]. Canonical Gq signaling drives an IP3/intracellular Ca2+/PKC cascade that modulates ion channels in spinal ventral horn neurons, potentiating glycine currents [#10] and, together with OX2R via a Ca2+-independent PKC route, suppressing GABA currents [#11]. In parallel, OX1R executes a non-canonical, phospholipase C-independent death pathway: freed Gq βγ activates Src, which phosphorylates an ITIM at Y358 and an ITSM at Y83 in the receptor's intracellular regions, recruiting SHP-2 to trigger cytochrome c release and caspase-3/7 activation in cancer cells [#0, #1, #2]. Beyond these, OX1R engages PI3K/AKT, MAPK/ERK, and mTOR/p70S6K1 cascades to control cell survival, autophagy, and steroidogenesis—protecting hepatocytes and neurons from apoptosis [#6, #8], suppressing autophagy to promote cortisol secretion in adrenocortical cells [#14], and limiting inflammatory NF-κB signaling [#9, #18]. OX1R forms constitutive heterodimers with GHSR1a and APJ that reshape its G protein coupling and trafficking [#3, #4]. In the CNS, OX1R signaling in defined nuclei contributes to behavioral despair [#17], VTA dopamine neuron excitability and associated anxiety/addiction phenotypes [#19, #22], and cardiorespiratory regulation [#16, #21]. α-Synuclein binds OX1R directly and promotes its proteasomal and lysosomal degradation, linking receptor turnover to orexin neuron dysfunction [#13].\",\n  \"teleology\": [\n    {\n      \"year\": 2008,\n      \"claim\": \"Established that OX1R signals to apoptosis through a previously unrecognized tyrosine-based motif rather than its canonical Ca2+ pathway, redefining the receptor as a death-signaling GPCR in cancer.\",\n      \"evidence\": \"Y358F mutagenesis, transfection in CHO cells, Gαq-null fibroblasts, PLC inhibitor, dominant-negative SHP-2\",\n      \"pmids\": [\"18198212\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the upstream tyrosine kinase phosphorylating Y358\", \"Generality across non-cancer cell types untested\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Showed that a second motif (ITSM Y83) is co-required with the ITIM, defining a bipartite phosphotyrosine docking site for both SHP-2 SH2 domains and clarifying how the receptor engages the phosphatase.\",\n      \"evidence\": \"Y83F mutagenesis, IP/calcium and SHP-2 recruitment assays, computational structural modeling\",\n      \"pmids\": [\"19661287\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural model not experimentally validated\", \"Stoichiometry of OX1R-SHP-2 binding not directly measured\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Consolidated the death pathway by identifying Gq βγ-activated Src as the kinase upstream of ITIM phosphorylation in colon cancer, completing a receptor-to-mitochondria signaling chain.\",\n      \"evidence\": \"Review synthesizing Gq-null cell, PLC inhibitor, dominant-negative SHP-2 and caspase data\",\n      \"pmids\": [\"21627633\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-group synthesis without independent replication\", \"Direct demonstration that βγ-Src acts on OX1R in situ limited\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated that OX1R can also be pro-survival via PI3K/AKT-FoxO1-mTORC1, establishing context-dependence of orexin signaling outcomes.\",\n      \"evidence\": \"Pharmacological inhibitors at multiple pathway nodes in primary rat hepatocytes\",\n      \"pmids\": [\"24807827\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not reconcile pro-survival vs pro-apoptotic outcomes mechanistically\", \"Single tissue context\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Provided a structural hypothesis for orexin-A engagement of OX1R, proposing alternative binding modes consistent with mutagenesis.\",\n      \"evidence\": \"Homology modeling on OX2R/NTSR1/CXCR4 templates with docking and clustering\",\n      \"pmids\": [\"25957175\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Computational only; no experimental validation of binding modes\", \"Cannot distinguish which mode is functional\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed that OX1R does not signal in isolation but forms a constitutive heterodimer with GHSR1a that reprograms G protein coupling toward Gs/cAMP, expanding the receptor's signaling repertoire.\",\n      \"evidence\": \"BRET, FRET, Co-IP, TM5 peptide interference, cAMP and CRE-luciferase assays\",\n      \"pmids\": [\"30065627\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"In vivo relevance of heterodimer not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Extended heterodimerization to APJ, defining the TM4/TM5 interface and showing co-internalization, indicating combinatorial regulation of OX1R trafficking.\",\n      \"evidence\": \"BRET, reciprocal Co-IP, immunostaining, TM peptide interference\",\n      \"pmids\": [\"31668922\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional signaling consequences of APJ-OX1R heterodimer not quantified\", \"Single lab\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Dissected the canonical OX1R cascade in native spinal neurons, showing IP3/intracellular Ca2+/PKC potentiates glycine currents while a Ca2+-independent PKC route (OX1R+OX2R) inhibits GABA currents, mapping receptor coupling to specific inhibitory neurotransmission.\",\n      \"evidence\": \"Patch-clamp with subtype-selective antagonists, Ca2+ chelation, IP3R and PKC inhibitors/activators\",\n      \"pmids\": [\"33515654\", \"34134956\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Target ion channels not molecularly identified\", \"PKC isoform specificity not resolved\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established OX1R as a neuroprotective/anti-inflammatory node in cerebral ischemia via MAPK/ERK/mTOR control of autophagy and NF-κB/MAPK suppression, broadening its physiological roles.\",\n      \"evidence\": \"Western blot, viability/apoptosis assays in MCAO/R rat and OGD/R cell models with OX1R antagonism\",\n      \"pmids\": [\"33212156\", \"34358627\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor assignment based largely on pathway readouts and antagonist\", \"No genetic loss-of-function in these models\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified α-synuclein as a direct binding partner that drives OX1R degradation through proteasomal and lysosomal routes, linking receptor turnover to orexin neuron loss and sleep pathology.\",\n      \"evidence\": \"Co-IP, proteasome/lysosome inhibitors, lentiviral overexpression, in vivo LHA injection, sleep analysis\",\n      \"pmids\": [\"36689149\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding interface on OX1R not mapped\", \"E3 ligase mediating degradation unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Connected OX1R-mTOR/p70S6K1 autophagy suppression to steroidogenesis, showing the receptor regulates cortisol output via 3β-HSD induction.\",\n      \"evidence\": \"TEM, western blot, ELISA with OX1R and mTOR inhibitors in adrenocortical lines\",\n      \"pmids\": [\"37572990\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causal link between autophagy and 3β-HSD not fully isolated\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Used cell-type-specific deletion to place OX1R signaling in CRF neurons upstream of excessive alcohol consumption and BNST excitability, establishing circuit-level behavioral causality.\",\n      \"evidence\": \"Conditional HcrtR1 KO in CRF neurons, drinking assays, BNST patch-clamp (preprint)\",\n      \"pmids\": [\"bio_10.1101_2024.09.07.609774\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprint, single lab\", \"Sex-specific mechanism not resolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Demonstrated that OX1R mediates orexin-A excitation of VTA dopamine neurons and is required for normal anxiety and activity behaviors, anchoring the receptor in dopaminergic circuit function.\",\n      \"evidence\": \"DA-cell-specific Hcrtr1 KO, VTA patch-clamp, behavioral phenotyping; LH ox/dyn optogenetics (preprints)\",\n      \"pmids\": [\"bio_10.1101_2025.02.14.638329\", \"bio_10.1101_2024.08.01.606179\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Preprints, single lab\", \"Downstream effectors of DA neuron excitation not defined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How OX1R selects between pro-apoptotic (Src/SHP-2), pro-survival (PI3K/AKT), and canonical Ca2+/PKC outputs in a cell-context-dependent manner remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying model linking ligand/cofactor context to pathway choice\", \"Heterodimer contribution to output selection in vivo unknown\", \"No experimental high-resolution structure of OX1R complexes in the corpus\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 10, 11]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [0, 15]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [3, 4]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 3, 4]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 10, 11]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 2, 6]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [8, 14]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [10, 11, 19]}\n    ],\n    \"complexes\": [\n      \"GHSR1a-OX1R heterodimer\",\n      \"APJ-OX1R heterodimer\"\n    ],\n    \"partners\": [\n      \"SHP-2\",\n      \"Src\",\n      \"GHSR1a\",\n      \"APJ\",\n      \"SNCA\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}