{"gene":"GFRAL","run_date":"2026-04-28T18:06:52","timeline":{"discoveries":[{"year":2017,"finding":"GFRAL is the high-affinity receptor for GDF15; GDF15 binds GFRAL with high affinity, and genetic deletion of GFRAL abrogates the ability of GDF15 to decrease food intake and body weight in mice fed a high-fat diet.","method":"Radioligand binding assay, Gfral knockout mice with in vivo pharmacology (recombinant GDF15 administration)","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 1-2 — independently replicated simultaneously by four groups, receptor-ligand binding plus genetic KO with defined phenotypic readout","pmids":["28846097","28846098","28846099"],"is_preprint":false},{"year":2017,"finding":"GDF15-induced intracellular signaling requires the interaction of GFRAL with the co-receptor RET; GFRAL alone is insufficient and must recruit RET to transduce the GDF15 signal.","method":"Cell-based signaling assay (RET co-receptor requirement), co-receptor recruitment experiments","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 1-2 — independently replicated by multiple groups using functional cell signaling assays","pmids":["28846097","28846099","28846098"],"is_preprint":false},{"year":2017,"finding":"GFRAL expression is restricted to neurons of the area postrema (AP) and nucleus of the solitary tract (NTS) in the hindbrain of mice, rats, and monkeys, establishing a central (CNS) mechanism for GDF15-mediated food intake reduction.","method":"In situ hybridization, immunohistochemistry, regional mRNA expression analysis","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 2 — replicated across multiple independent labs with consistent localization findings","pmids":["28846097","28846098","28846099"],"is_preprint":false},{"year":2005,"finding":"GFRAL (GRAL) protein localizes predominantly to the plasma membrane; overexpression of GFRAL-A protects PC12 cells and hippocampal neurons from serum starvation-induced apoptosis through inhibition of the JNK signaling pathway.","method":"Subcellular fractionation/immunofluorescence for localization; cell survival assay with overexpression and JNK pathway analysis","journal":"Journal of neurochemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 — single lab, overexpression system with pathway readout, predates identification of GDF15 as ligand","pmids":["16086688"],"is_preprint":false},{"year":2019,"finding":"GFRAL expressed specifically in AP/NTS neurons mediates resistance to diet-induced obesity; shRNA knockdown of GFRAL specifically in the AP/NTS increased body weight and adiposity proportionally to knockdown efficiency, confirming AP/NTS as the major CNS site of GDF15 action.","method":"AAV-shRNA regional knockdown in AP/NTS, quantitative immunostaining, metabolic measurements","journal":"International journal of obesity","confidence":"High","confidence_rationale":"Tier 2 — direct regional loss-of-function with quantitative phenotypic correlation","pmids":["31152154"],"is_preprint":false},{"year":2020,"finding":"An antagonistic anti-GFRAL monoclonal antibody (3P10) prevents the GDF15-driven interaction of RET with GFRAL on the cell surface, blocking RET phosphorylation and downstream signaling. Activation of the GFRAL-RET pathway induces expression of lipid metabolism genes in adipose tissue, and peripheral sympathectomy or loss of adipose triglyceride lipase protects mice from GDF15-induced weight loss, revealing a peripheral sympathetic lipolytic axis downstream of GFRAL.","method":"Antagonistic monoclonal antibody, cell-surface receptor interaction assay, chemical sympathectomy, ATGL knockout mice, gene expression in adipose tissue","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 1-2 — multiple orthogonal methods including antibody blocking, genetic knockouts, and pathway analysis in single rigorous study","pmids":["32661391"],"is_preprint":false},{"year":2021,"finding":"Artificial activation of GFRAL-expressing neurons inhibits feeding, decreases gastric emptying, and promotes conditioned taste aversion. GFRAL neurons most strongly innervate the parabrachial nucleus (PBN), targeting CGRP-expressing (CGRP-PBN) neurons, and silencing CGRP-PBN neurons abrogates the aversive and anorectic effects of GDF-15.","method":"Chemogenetic/optogenetic activation of Gfral-Cre neurons, TRAP-Seq transcriptomics, conditional neuron silencing, behavioral assays (conditioned taste aversion, food intake, gastric emptying)","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — genetic Cre-based tools with multiple orthogonal functional assays and circuit-level epistasis","pmids":["33593916"],"is_preprint":false},{"year":2022,"finding":"MT1-MMP (MMP14) proteolytically cleaves and inactivates GFRAL, acting as an endogenous negative regulator of GDF15-GFRAL signaling in the context of obesity. Overnutrition-induced obesity increases MT1-MMP activation, suppressing GFRAL-mediated anorectic signaling. Genetic ablation of MT1-MMP specifically in GFRAL+ neurons restores GFRAL expression and reduces weight gain.","method":"Proteolytic cleavage assay, conditional MT1-MMP knockout in GFRAL+ neurons, GFRAL immunostaining, in vivo metabolic phenotyping","journal":"Nature metabolism","confidence":"High","confidence_rationale":"Tier 1-2 — enzymatic mechanism established with cell-type-specific genetic ablation and multiple functional readouts","pmids":["35177851"],"is_preprint":false},{"year":2022,"finding":"The GDF15-GFRAL axis mediates cisplatin-induced behavioral fatigue in mice; a neutralizing monoclonal antibody against GFRAL largely prevented cisplatin-induced decrease in voluntary wheel running and accelerated recovery.","method":"Neutralizing anti-GFRAL monoclonal antibody, voluntary wheel running behavioral assay, GDF15-Fc administration","journal":"Brain, behavior, and immunity","confidence":"Medium","confidence_rationale":"Tier 2-3 — pharmacological GFRAL blockade with defined behavioral phenotype, single lab","pmids":["36427806"],"is_preprint":false},{"year":2022,"finding":"GFRAL is required for mitochondrial stress-induced daytime-restricted anorexia and anxiety-like behavior; in a mouse model of muscle-specific mitochondrial dysfunction, GFRAL mediates GDF15-driven hypothalamic corticotropin-releasing hormone induction and anxiogenic behavior without elevated corticosterone.","method":"Gfral knockout mice crossed with muscle-specific mitochondrial dysfunction model, food intake measurements, anxiety behavioral assays, CRH expression analysis","journal":"Life science alliance","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO with defined physiological and behavioral phenotypes, single lab","pmids":["36271504"],"is_preprint":false},{"year":2024,"finding":"Acute GDF15 infusion directly into the area postrema activates GFRAL to increase glucose tolerance and insulin sensitivity by lowering hepatic glucose production, independent of changes in food intake, weight, and plasma insulin. GFRAL knockdown in the AP negated both GDF15 and metformin effects on glucose tolerance.","method":"Stereotaxic intracerebral infusion into area postrema, hyperinsulinemic-euglycemic clamp, GFRAL knockdown (AAV-shRNA), hepatic glucose production measurement","journal":"Diabetes","confidence":"High","confidence_rationale":"Tier 1-2 — direct regional manipulation with rigorous in vivo metabolic clamp measurements and regional KD rescue","pmids":["38064571"],"is_preprint":false},{"year":2024,"finding":"Cell-specific activation of GFRAL+ neurons induces a torpor-like state including hypothermia, stress hormone release, shift from glucose to lipid oxidation, impaired insulin sensitivity, impaired glucose tolerance, reduced skeletal muscle glucose uptake, and augmented visceral fat glucose uptake.","method":"Chemogenetic/optogenetic cell-specific activation of GFRAL+ neurons, metabolomics, transcriptomics of muscle and fat, glucose uptake measurements","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 2 — cell-type-specific activation with multiple orthogonal metabolic readouts","pmids":["38507407"],"is_preprint":false},{"year":2020,"finding":"GFRAL expressed on endothelial cells mediates MIC-1/GDF15-induced proangiogenic signaling via MEK/ERK and PI3K/Akt pathways; siRNA knockdown of GFRAL abrogated MIC-1-induced angiogenic responses in endothelial cells.","method":"siRNA knockdown of GFRAL in endothelial cells, angiogenesis assays (tube formation, sprouting), MIC-1 transgenic mouse model, signaling pathway inhibitors","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2-3 — loss-of-function with defined cellular phenotype, single lab, receptor function in non-neuronal context","pmids":["33151561"],"is_preprint":false},{"year":2023,"finding":"GDF-15 inhibits ADP-induced human platelet aggregation through the GFRAL/RET signaling complex expressed on platelets; GFRAL was identified as the binding partner of GDF-15 on platelets by receptor microarray and immunoprecipitation, and GDF-15 inhibits AKT and ERK activation via this complex.","method":"Platelet aggregation assay, receptor microarray, immunoprecipitation, RET agonist/inhibitor pharmacology, ERK/AKT pathway analysis","journal":"Biomolecules","confidence":"Medium","confidence_rationale":"Tier 2-3 — biochemical identification of GFRAL-RET on platelets with functional signaling readout, single lab","pmids":["38254638"],"is_preprint":false},{"year":2024,"finding":"A population of BDNF-expressing neurons in the medial NTS (BDNF-mNTS) lies downstream of GFRAL/GLP1R neurons and is required for the weight-reducing actions of GDF15; acute activation of BDNF-mNTS neurons reduces food intake and drives fatty acid oxidation.","method":"Genetic circuit tracing, conditional neuron ablation/activation (Cre-based), Exendin-4 and GDF15 pharmacology in BDNF-mNTS-specific manipulated mice","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — circuit-level epistasis with genetic tools establishing downstream pathway position","pmids":["39737892"],"is_preprint":false},{"year":2024,"finding":"GFRAL silencing by shRNA in the AP/NTS of ALS model mice (hSOD1G93A) induces weight gain, reduces adipose wasting, ameliorates motor function and muscle atrophy, and prolongs survival, indicating that GDF15-GFRAL signaling drives weight loss and lipid metabolism dysfunction in ALS.","method":"shRNA-mediated regional GFRAL knockdown in AP/NTS, body weight monitoring, lipolytic gene expression in adipose tissue, motor function tests, survival analysis, microglia depletion (PLX5622)","journal":"Brain, behavior, and immunity","confidence":"Medium","confidence_rationale":"Tier 2 — regional loss-of-function with multiple functional readouts in disease model, single lab","pmids":["39672239"],"is_preprint":false},{"year":2026,"finding":"GDF15-GFRAL signaling on brainstem neurons suppresses autoimmune T cell responses by inducing β-adrenergic signaling and norepinephrine synthesis in the spleen, leading to decreased integrin expression on T cells required for blood-brain barrier transmigration.","method":"Gfral knockout mice in EAE model, neuronal GDF15/GFRAL gene delivery, chemogenetic activation of GFRAL+ neurons, norepinephrine/integrin measurements, T cell flow cytometry","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal genetic and pharmacological approaches establishing neuroimmune circuit with molecular mechanism","pmids":["41540266"],"is_preprint":false},{"year":2023,"finding":"GDF15 C-terminal peptide fragments bind the extracellular domain of GFRAL (identified by SPOT peptide arrays) and inhibit GFRAL/RET signaling in cells expressing the receptor complex, revealing the binding interface relevant for antagonist design.","method":"SPOT peptide arrays, solid-phase peptide synthesis, functional cell-based GFRAL/RET signaling assay","journal":"Peptides","confidence":"Medium","confidence_rationale":"Tier 2-3 — biochemical mapping of GDF15-GFRAL interaction surface with functional validation, single lab","pmids":["37495041"],"is_preprint":false},{"year":2023,"finding":"A peptide antagonist of GFRAL (GRASP) binds GFRAL directly (surface plasmon resonance, flow cytometry), blocks GDF15-mediated RET recruitment, and attenuates GDF15-induced nausea and anorexia in rats.","method":"Peptide library screen, surface plasmon resonance, flow cytometry, in vivo rat nausea/anorexia model with cisplatin","journal":"Journal of medicinal chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — biophysical binding confirmation plus in vivo functional antagonism, single lab","pmids":["37506293"],"is_preprint":false},{"year":2025,"finding":"Bicyclic peptide tandems that mimic homodimeric GDF15 bind GFRAL with picomolar affinity and inhibit GDF15-GFRAL protein-protein interaction and RET-induced cell signaling in functional assays, with structural data guiding design.","method":"Phage display, structure-guided design, biophysical binding assays, functional cell signaling inhibition assay, pharmacokinetic profiling","journal":"Journal of medicinal chemistry","confidence":"Medium","confidence_rationale":"Tier 1-2 — structure-guided design with functional validation of receptor-ligand interaction inhibition","pmids":["41066664"],"is_preprint":false}],"current_model":"GFRAL is a GPI-anchored receptor restricted predominantly to area postrema and NTS neurons in the hindbrain that binds GDF15 with high affinity and obligatorily recruits the co-receptor RET to transduce intracellular signals; this GFRAL-RET complex mediates GDF15-driven suppression of food intake and body weight via aversive/anorectic neural circuits (projecting to CGRP-PBN neurons and downstream BDNF-mNTS neurons), while also regulating hepatic glucose production, lipid metabolism through a peripheral sympathetic-lipolytic axis, thermoregulation, and neuroimmune responses; GFRAL surface availability is negatively regulated by MT1-MMP-mediated proteolytic cleavage during obesity, providing a feedback mechanism that limits GDF15 sensitivity."},"narrative":{"teleology":[{"year":2005,"claim":"Before GDF15 was identified as its ligand, GFRAL (then called GRAL) was shown to localize to the plasma membrane and to exert a neuroprotective anti-apoptotic effect by inhibiting JNK signaling, establishing it as a neuronal surface receptor with survival functions.","evidence":"Overexpression in PC12 cells and hippocampal neurons with subcellular fractionation and JNK pathway analysis","pmids":["16086688"],"confidence":"Medium","gaps":["Overexpression system without identified ligand limits physiological interpretation","JNK inhibition mechanism not connected to any upstream signal","No in vivo confirmation of neuroprotective role"]},{"year":2017,"claim":"The central breakthrough came when four independent groups simultaneously identified GFRAL as the high-affinity receptor for GDF15, demonstrated that GFRAL obligatorily recruits co-receptor RET for signal transduction, and showed that GFRAL expression is restricted to area postrema/NTS neurons — resolving the long-standing mystery of how circulating GDF15 suppresses food intake and body weight.","evidence":"Radioligand binding, Gfral knockout mice, cell-based co-receptor signaling assays, in situ hybridization across species","pmids":["28846097","28846098","28846099"],"confidence":"High","gaps":["Downstream intracellular signaling cascades beyond RET phosphorylation were not fully mapped","Whether GFRAL functions outside the CNS was not addressed","Crystal structure of the ternary GDF15–GFRAL–RET complex not yet determined"]},{"year":2019,"claim":"Regional shRNA knockdown quantitatively demonstrated that GFRAL in AP/NTS neurons is both necessary and sufficient for resistance to diet-induced obesity, with adiposity proportional to knockdown efficiency, confirming the anatomical site of action.","evidence":"AAV-shRNA knockdown in AP/NTS with quantitative immunostaining and metabolic phenotyping","pmids":["31152154"],"confidence":"High","gaps":["Neuronal subtypes within AP/NTS expressing GFRAL were not resolved","Downstream circuit targets of GFRAL neurons remained uncharacterized"]},{"year":2020,"claim":"Antagonistic anti-GFRAL antibody blockade and genetic/pharmacological ablation of peripheral sympathetic nerves revealed that GFRAL–RET signaling drives weight loss partly through a peripheral sympathetic-lipolytic axis involving adipose triglyceride lipase, extending the pathway beyond central anorexia to peripheral lipid mobilization.","evidence":"Anti-GFRAL monoclonal antibody, chemical sympathectomy, ATGL knockout mice, adipose gene expression profiling","pmids":["32661391"],"confidence":"High","gaps":["Neural pathway from brainstem GFRAL neurons to sympathetic outflow not anatomically traced","Relative contributions of anorexia versus lipolysis to total weight loss not dissected"]},{"year":2020,"claim":"GFRAL was detected on endothelial cells where it mediates GDF15-induced proangiogenic signaling via MEK/ERK and PI3K/Akt, suggesting GFRAL function beyond the CNS.","evidence":"siRNA knockdown in endothelial cells with tube formation and sprouting assays","pmids":["33151561"],"confidence":"Medium","gaps":["Endothelial GFRAL expression not confirmed at protein level in vivo","Whether RET is the co-receptor in this context was not tested","Single-lab finding not independently replicated"]},{"year":2021,"claim":"Circuit-level dissection using Gfral-Cre mice revealed that GFRAL neurons project predominantly to CGRP-expressing parabrachial nucleus neurons, and silencing these downstream neurons abolished GDF15-induced aversion and anorexia, establishing the first defined neural circuit for GDF15 action.","evidence":"Chemogenetic/optogenetic activation of Gfral-Cre neurons, TRAP-Seq, conditional CGRP-PBN silencing, conditioned taste aversion assays","pmids":["33593916"],"confidence":"High","gaps":["Other downstream targets of GFRAL neurons beyond PBN were not explored","Whether metabolic effects (glucose, lipid) require CGRP-PBN neurons was not tested"]},{"year":2022,"claim":"MT1-MMP was identified as an endogenous negative regulator that proteolytically cleaves GFRAL on neuronal surfaces, with obesity-driven MT1-MMP upregulation explaining reduced GDF15 sensitivity; cell-type-specific MT1-MMP deletion restored GFRAL and protected against weight gain.","evidence":"Proteolytic cleavage assays, conditional MT1-MMP knockout in GFRAL+ neurons, metabolic phenotyping","pmids":["35177851"],"confidence":"High","gaps":["Exact cleavage site on GFRAL not mapped","Whether shed GFRAL ectodomain acts as a decoy receptor is unknown","Signals upstream of MT1-MMP activation in obesity not identified"]},{"year":2022,"claim":"Beyond food intake, GFRAL was shown to mediate chemotherapy-induced behavioral fatigue and mitochondrial stress-induced anorexia with anxiety, broadening its role to sickness behavior and stress-associated affective changes.","evidence":"Anti-GFRAL antibody in cisplatin-treated mice (wheel running); Gfral KO crossed with muscle mitochondrial dysfunction model (anxiety assays, CRH expression)","pmids":["36427806","36271504"],"confidence":"Medium","gaps":["Specific neuronal populations mediating fatigue versus anorexia versus anxiety not dissected","CRH induction pathway downstream of GFRAL not fully characterized"]},{"year":2023,"claim":"Biochemical and pharmacological dissection of the GDF15–GFRAL binding interface via peptide arrays and designed antagonists (including the GRASP peptide) defined the extracellular interaction surface and provided proof-of-concept that GFRAL blockade attenuates GDF15-induced nausea in vivo.","evidence":"SPOT peptide arrays, surface plasmon resonance, peptide antagonist in rat cisplatin nausea model, GFRAL on platelets by immunoprecipitation and receptor microarray","pmids":["37495041","37506293","38254638"],"confidence":"Medium","gaps":["High-resolution co-crystal structure of antagonist–GFRAL complex not available","Platelet GFRAL function in vivo physiological hemostasis not confirmed","Selectivity of peptide antagonists over related GDNF-family receptors not fully addressed"]},{"year":2024,"claim":"Direct infusion of GDF15 into the area postrema demonstrated that GFRAL activation acutely lowers hepatic glucose production and increases insulin sensitivity independent of food intake or weight change, establishing a food-intake-independent metabolic role, while cell-specific GFRAL neuron activation revealed a torpor-like state encompassing hypothermia, fuel switching, and stress hormone release.","evidence":"Stereotaxic AP infusion with hyperinsulinemic-euglycemic clamp and GFRAL knockdown; chemogenetic activation of GFRAL+ neurons with metabolomics and transcriptomics","pmids":["38064571","38507407"],"confidence":"High","gaps":["Efferent pathways from AP GFRAL neurons to liver not anatomically traced","Whether torpor-like response is physiologically relevant outside experimental activation is unclear","Integration with other glucose-regulatory circuits (e.g., GLP-1) not defined"]},{"year":2024,"claim":"BDNF-expressing medial NTS neurons were positioned downstream of GFRAL neurons in a hierarchical circuit required for GDF15-induced weight reduction and fatty acid oxidation, and GFRAL knockdown in an ALS model ameliorated wasting and prolonged survival, linking the pathway to neurodegenerative cachexia.","evidence":"Genetic circuit tracing and conditional neuron ablation/activation for BDNF-mNTS; shRNA-mediated GFRAL knockdown in hSOD1-G93A ALS mice with survival and motor analysis","pmids":["39737892","39672239"],"confidence":"High","gaps":["How BDNF-mNTS neurons integrate GDF15 versus GLP-1 signals is unknown","Therapeutic window for GFRAL blockade in ALS (beneficial weight preservation versus loss of metabolic regulation) not defined"]},{"year":2026,"claim":"GDF15–GFRAL signaling was shown to suppress autoimmune T cell responses via a brain-to-spleen neuroimmune circuit involving β-adrenergic signaling and norepinephrine-dependent downregulation of T cell integrins, revealing an immunomodulatory function of GFRAL beyond metabolism.","evidence":"Gfral knockout mice in EAE, neuronal gene delivery, chemogenetic activation, norepinephrine and integrin measurements","pmids":["41540266"],"confidence":"High","gaps":["Whether this neuroimmune axis operates in non-autoimmune inflammatory contexts is untested","Identity of the sympathetic relay neurons between brainstem and spleen not resolved"]},{"year":null,"claim":"Key unresolved questions include the high-resolution structure of the ternary GDF15–GFRAL–RET complex, the full intracellular signaling cascade downstream of RET in GFRAL neurons, the precise efferent neural pathways from GFRAL neurons to peripheral organs (liver, sympathetic chain, spleen), and the physiological relevance of GFRAL expression outside the CNS (endothelial cells, platelets).","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution ternary complex structure available","Intracellular signaling beyond RET/ERK/AKT phosphorylation in GFRAL neurons remains unmapped","Peripheral (non-neuronal) GFRAL functions lack in vivo validation"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,1,5]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,5,7]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,0,1]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,5,12]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[16]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[2,4,6,14]}],"complexes":["GFRAL–RET signaling complex"],"partners":["GDF15","RET","MMP14"],"other_free_text":[]},"mechanistic_narrative":"GFRAL is the obligate high-affinity receptor for the stress-responsive cytokine GDF15, functioning as a hindbrain-restricted signaling hub that transduces metabolic, behavioral, and neuroimmune signals through recruitment of the co-receptor RET [PMID:28846097, PMID:28846098, PMID:28846099]. Expressed predominantly on area postrema and nucleus of the solitary tract neurons, GFRAL–RET activation suppresses food intake via projections to CGRP-expressing parabrachial nucleus neurons and downstream BDNF-mNTS neurons, while simultaneously regulating hepatic glucose production, peripheral sympathetic lipolysis, thermoregulation, and autoimmune T cell responses through β-adrenergic splenic signaling [PMID:33593916, PMID:32661391, PMID:38064571, PMID:38507407, PMID:39737892, PMID:41540266]. GFRAL surface availability is negatively regulated by MT1-MMP–mediated proteolytic cleavage, which is upregulated during obesity and limits GDF15 sensitivity; genetic ablation of MT1-MMP in GFRAL-positive neurons restores receptor expression and attenuates weight gain [PMID:35177851]. GFRAL signaling also mediates chemotherapy-induced fatigue, mitochondrial stress-driven anorexia and anxiety, and cachexia-associated wasting in neurodegenerative disease models [PMID:36427806, PMID:36271504, PMID:39672239]."},"prefetch_data":{"uniprot":{"accession":"Q6UXV0","full_name":"GDNF family receptor alpha-like","aliases":[],"length_aa":394,"mass_kda":44.5,"function":"Brainstem-restricted receptor for GDF15 hormone, which triggers an aversive response, characterized by nausea, vomiting, and/or loss of appetite in response to various stresses (PubMed:28846097, PubMed:28846098, PubMed:28846099, PubMed:28953886, PubMed:36630958). The aversive response is both required to reduce continuing exposure to those stresses at the time of exposure and to promote avoidance behavior in the future (PubMed:28846097, PubMed:28846098, PubMed:28846099, PubMed:28953886, PubMed:36630958). The GDF15-GFRAL aversive response is triggered by stresses, such as anticancer drugs (camptothecin or cisplatin), cancers or drugs such as metformin (PubMed:32661391). Upon interaction with its ligand, GDF15, mediates the GDF15-induced autophosphorylation and activation of the RET tyrosine kinase receptor, leading to activation of MAPK- and AKT- signaling pathways (PubMed:31535977, PubMed:32661391). Ligand-binding activates GFRAL-expressing neurons localized in the area postrema and nucleus tractus solitarius of the brainstem (By similarity). The GDF15-GFRAL signal induces expression of genes involved in metabolism, such as lipid metabolism in adipose tissues (PubMed:32661391)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q6UXV0/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/GFRAL","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/GFRAL","total_profiled":1310},"omim":[{"mim_id":"617837","title":"GDNF FAMILY RECEPTOR ALPHA-LIKE PROTEIN; GFRAL","url":"https://www.omim.org/entry/617837"},{"mim_id":"605312","title":"GROWTH/DIFFERENTIATION FACTOR 15; GDF15","url":"https://www.omim.org/entry/605312"},{"mim_id":"604446","title":"PHOSPHOTRIESTERASE-RELATED PROTEIN; PTER","url":"https://www.omim.org/entry/604446"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Approved"},{"location":"Actin filaments","reliability":"Additional"},{"location":"Focal adhesion sites","reliability":"Additional"}],"tissue_specificity":"Not detected","tissue_distribution":"Not detected","driving_tissues":[],"url":"https://www.proteinatlas.org/search/GFRAL"},"hgnc":{"alias_symbol":["GRAL","UNQ9356","bA360D14.1"],"prev_symbol":["C6orf144"]},"alphafold":{"accession":"Q6UXV0","domains":[{"cath_id":"-","chopping":"25-98","consensus_level":"high","plddt":85.0464,"start":25,"end":98},{"cath_id":"1.10.220","chopping":"128-207","consensus_level":"medium","plddt":88.3697,"start":128,"end":207},{"cath_id":"1.10.220.110","chopping":"215-324","consensus_level":"medium","plddt":92.6548,"start":215,"end":324}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6UXV0","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q6UXV0-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q6UXV0-F1-predicted_aligned_error_v6.png","plddt_mean":76.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=GFRAL","jax_strain_url":"https://www.jax.org/strain/search?query=GFRAL"},"sequence":{"accession":"Q6UXV0","fasta_url":"https://rest.uniprot.org/uniprotkb/Q6UXV0.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q6UXV0/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6UXV0"}},"corpus_meta":[{"pmid":"28846097","id":"PMC_28846097","title":"GFRAL is the receptor for GDF15 and the ligand promotes weight loss in mice and nonhuman primates.","date":"2017","source":"Nature medicine","url":"https://pubmed.ncbi.nlm.nih.gov/28846097","citation_count":615,"is_preprint":false},{"pmid":"28846098","id":"PMC_28846098","title":"The metabolic effects of GDF15 are mediated by the orphan receptor GFRAL.","date":"2017","source":"Nature medicine","url":"https://pubmed.ncbi.nlm.nih.gov/28846098","citation_count":541,"is_preprint":false},{"pmid":"28846099","id":"PMC_28846099","title":"GFRAL is the receptor for GDF15 and is required for the anti-obesity effects of the ligand.","date":"2017","source":"Nature medicine","url":"https://pubmed.ncbi.nlm.nih.gov/28846099","citation_count":536,"is_preprint":false},{"pmid":"30184485","id":"PMC_30184485","title":"The MIC-1/GDF15-GFRAL Pathway in Energy Homeostasis: Implications for Obesity, Cachexia, and Other Associated Diseases.","date":"2018","source":"Cell 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GDF15 binds GFRAL with high affinity, and genetic deletion of GFRAL abrogates the ability of GDF15 to decrease food intake and body weight in mice fed a high-fat diet.\",\n      \"method\": \"Radioligand binding assay, Gfral knockout mice with in vivo pharmacology (recombinant GDF15 administration)\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — independently replicated simultaneously by four groups, receptor-ligand binding plus genetic KO with defined phenotypic readout\",\n      \"pmids\": [\"28846097\", \"28846098\", \"28846099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GDF15-induced intracellular signaling requires the interaction of GFRAL with the co-receptor RET; GFRAL alone is insufficient and must recruit RET to transduce the GDF15 signal.\",\n      \"method\": \"Cell-based signaling assay (RET co-receptor requirement), co-receptor recruitment experiments\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — independently replicated by multiple groups using functional cell signaling assays\",\n      \"pmids\": [\"28846097\", \"28846099\", \"28846098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GFRAL expression is restricted to neurons of the area postrema (AP) and nucleus of the solitary tract (NTS) in the hindbrain of mice, rats, and monkeys, establishing a central (CNS) mechanism for GDF15-mediated food intake reduction.\",\n      \"method\": \"In situ hybridization, immunohistochemistry, regional mRNA expression analysis\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — replicated across multiple independent labs with consistent localization findings\",\n      \"pmids\": [\"28846097\", \"28846098\", \"28846099\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"GFRAL (GRAL) protein localizes predominantly to the plasma membrane; overexpression of GFRAL-A protects PC12 cells and hippocampal neurons from serum starvation-induced apoptosis through inhibition of the JNK signaling pathway.\",\n      \"method\": \"Subcellular fractionation/immunofluorescence for localization; cell survival assay with overexpression and JNK pathway analysis\",\n      \"journal\": \"Journal of neurochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — single lab, overexpression system with pathway readout, predates identification of GDF15 as ligand\",\n      \"pmids\": [\"16086688\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GFRAL expressed specifically in AP/NTS neurons mediates resistance to diet-induced obesity; shRNA knockdown of GFRAL specifically in the AP/NTS increased body weight and adiposity proportionally to knockdown efficiency, confirming AP/NTS as the major CNS site of GDF15 action.\",\n      \"method\": \"AAV-shRNA regional knockdown in AP/NTS, quantitative immunostaining, metabolic measurements\",\n      \"journal\": \"International journal of obesity\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — direct regional loss-of-function with quantitative phenotypic correlation\",\n      \"pmids\": [\"31152154\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"An antagonistic anti-GFRAL monoclonal antibody (3P10) prevents the GDF15-driven interaction of RET with GFRAL on the cell surface, blocking RET phosphorylation and downstream signaling. Activation of the GFRAL-RET pathway induces expression of lipid metabolism genes in adipose tissue, and peripheral sympathectomy or loss of adipose triglyceride lipase protects mice from GDF15-induced weight loss, revealing a peripheral sympathetic lipolytic axis downstream of GFRAL.\",\n      \"method\": \"Antagonistic monoclonal antibody, cell-surface receptor interaction assay, chemical sympathectomy, ATGL knockout mice, gene expression in adipose tissue\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods including antibody blocking, genetic knockouts, and pathway analysis in single rigorous study\",\n      \"pmids\": [\"32661391\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Artificial activation of GFRAL-expressing neurons inhibits feeding, decreases gastric emptying, and promotes conditioned taste aversion. GFRAL neurons most strongly innervate the parabrachial nucleus (PBN), targeting CGRP-expressing (CGRP-PBN) neurons, and silencing CGRP-PBN neurons abrogates the aversive and anorectic effects of GDF-15.\",\n      \"method\": \"Chemogenetic/optogenetic activation of Gfral-Cre neurons, TRAP-Seq transcriptomics, conditional neuron silencing, behavioral assays (conditioned taste aversion, food intake, gastric emptying)\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic Cre-based tools with multiple orthogonal functional assays and circuit-level epistasis\",\n      \"pmids\": [\"33593916\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MT1-MMP (MMP14) proteolytically cleaves and inactivates GFRAL, acting as an endogenous negative regulator of GDF15-GFRAL signaling in the context of obesity. Overnutrition-induced obesity increases MT1-MMP activation, suppressing GFRAL-mediated anorectic signaling. Genetic ablation of MT1-MMP specifically in GFRAL+ neurons restores GFRAL expression and reduces weight gain.\",\n      \"method\": \"Proteolytic cleavage assay, conditional MT1-MMP knockout in GFRAL+ neurons, GFRAL immunostaining, in vivo metabolic phenotyping\",\n      \"journal\": \"Nature metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — enzymatic mechanism established with cell-type-specific genetic ablation and multiple functional readouts\",\n      \"pmids\": [\"35177851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The GDF15-GFRAL axis mediates cisplatin-induced behavioral fatigue in mice; a neutralizing monoclonal antibody against GFRAL largely prevented cisplatin-induced decrease in voluntary wheel running and accelerated recovery.\",\n      \"method\": \"Neutralizing anti-GFRAL monoclonal antibody, voluntary wheel running behavioral assay, GDF15-Fc administration\",\n      \"journal\": \"Brain, behavior, and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — pharmacological GFRAL blockade with defined behavioral phenotype, single lab\",\n      \"pmids\": [\"36427806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"GFRAL is required for mitochondrial stress-induced daytime-restricted anorexia and anxiety-like behavior; in a mouse model of muscle-specific mitochondrial dysfunction, GFRAL mediates GDF15-driven hypothalamic corticotropin-releasing hormone induction and anxiogenic behavior without elevated corticosterone.\",\n      \"method\": \"Gfral knockout mice crossed with muscle-specific mitochondrial dysfunction model, food intake measurements, anxiety behavioral assays, CRH expression analysis\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with defined physiological and behavioral phenotypes, single lab\",\n      \"pmids\": [\"36271504\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Acute GDF15 infusion directly into the area postrema activates GFRAL to increase glucose tolerance and insulin sensitivity by lowering hepatic glucose production, independent of changes in food intake, weight, and plasma insulin. GFRAL knockdown in the AP negated both GDF15 and metformin effects on glucose tolerance.\",\n      \"method\": \"Stereotaxic intracerebral infusion into area postrema, hyperinsulinemic-euglycemic clamp, GFRAL knockdown (AAV-shRNA), hepatic glucose production measurement\",\n      \"journal\": \"Diabetes\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — direct regional manipulation with rigorous in vivo metabolic clamp measurements and regional KD rescue\",\n      \"pmids\": [\"38064571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Cell-specific activation of GFRAL+ neurons induces a torpor-like state including hypothermia, stress hormone release, shift from glucose to lipid oxidation, impaired insulin sensitivity, impaired glucose tolerance, reduced skeletal muscle glucose uptake, and augmented visceral fat glucose uptake.\",\n      \"method\": \"Chemogenetic/optogenetic cell-specific activation of GFRAL+ neurons, metabolomics, transcriptomics of muscle and fat, glucose uptake measurements\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific activation with multiple orthogonal metabolic readouts\",\n      \"pmids\": [\"38507407\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"GFRAL expressed on endothelial cells mediates MIC-1/GDF15-induced proangiogenic signaling via MEK/ERK and PI3K/Akt pathways; siRNA knockdown of GFRAL abrogated MIC-1-induced angiogenic responses in endothelial cells.\",\n      \"method\": \"siRNA knockdown of GFRAL in endothelial cells, angiogenesis assays (tube formation, sprouting), MIC-1 transgenic mouse model, signaling pathway inhibitors\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — loss-of-function with defined cellular phenotype, single lab, receptor function in non-neuronal context\",\n      \"pmids\": [\"33151561\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"GDF-15 inhibits ADP-induced human platelet aggregation through the GFRAL/RET signaling complex expressed on platelets; GFRAL was identified as the binding partner of GDF-15 on platelets by receptor microarray and immunoprecipitation, and GDF-15 inhibits AKT and ERK activation via this complex.\",\n      \"method\": \"Platelet aggregation assay, receptor microarray, immunoprecipitation, RET agonist/inhibitor pharmacology, ERK/AKT pathway analysis\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — biochemical identification of GFRAL-RET on platelets with functional signaling readout, single lab\",\n      \"pmids\": [\"38254638\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"A population of BDNF-expressing neurons in the medial NTS (BDNF-mNTS) lies downstream of GFRAL/GLP1R neurons and is required for the weight-reducing actions of GDF15; acute activation of BDNF-mNTS neurons reduces food intake and drives fatty acid oxidation.\",\n      \"method\": \"Genetic circuit tracing, conditional neuron ablation/activation (Cre-based), Exendin-4 and GDF15 pharmacology in BDNF-mNTS-specific manipulated mice\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — circuit-level epistasis with genetic tools establishing downstream pathway position\",\n      \"pmids\": [\"39737892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"GFRAL silencing by shRNA in the AP/NTS of ALS model mice (hSOD1G93A) induces weight gain, reduces adipose wasting, ameliorates motor function and muscle atrophy, and prolongs survival, indicating that GDF15-GFRAL signaling drives weight loss and lipid metabolism dysfunction in ALS.\",\n      \"method\": \"shRNA-mediated regional GFRAL knockdown in AP/NTS, body weight monitoring, lipolytic gene expression in adipose tissue, motor function tests, survival analysis, microglia depletion (PLX5622)\",\n      \"journal\": \"Brain, behavior, and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — regional loss-of-function with multiple functional readouts in disease model, single lab\",\n      \"pmids\": [\"39672239\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"GDF15-GFRAL signaling on brainstem neurons suppresses autoimmune T cell responses by inducing β-adrenergic signaling and norepinephrine synthesis in the spleen, leading to decreased integrin expression on T cells required for blood-brain barrier transmigration.\",\n      \"method\": \"Gfral knockout mice in EAE model, neuronal GDF15/GFRAL gene delivery, chemogenetic activation of GFRAL+ neurons, norepinephrine/integrin measurements, T cell flow cytometry\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal genetic and pharmacological approaches establishing neuroimmune circuit with molecular mechanism\",\n      \"pmids\": [\"41540266\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"GDF15 C-terminal peptide fragments bind the extracellular domain of GFRAL (identified by SPOT peptide arrays) and inhibit GFRAL/RET signaling in cells expressing the receptor complex, revealing the binding interface relevant for antagonist design.\",\n      \"method\": \"SPOT peptide arrays, solid-phase peptide synthesis, functional cell-based GFRAL/RET signaling assay\",\n      \"journal\": \"Peptides\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — biochemical mapping of GDF15-GFRAL interaction surface with functional validation, single lab\",\n      \"pmids\": [\"37495041\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"A peptide antagonist of GFRAL (GRASP) binds GFRAL directly (surface plasmon resonance, flow cytometry), blocks GDF15-mediated RET recruitment, and attenuates GDF15-induced nausea and anorexia in rats.\",\n      \"method\": \"Peptide library screen, surface plasmon resonance, flow cytometry, in vivo rat nausea/anorexia model with cisplatin\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — biophysical binding confirmation plus in vivo functional antagonism, single lab\",\n      \"pmids\": [\"37506293\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Bicyclic peptide tandems that mimic homodimeric GDF15 bind GFRAL with picomolar affinity and inhibit GDF15-GFRAL protein-protein interaction and RET-induced cell signaling in functional assays, with structural data guiding design.\",\n      \"method\": \"Phage display, structure-guided design, biophysical binding assays, functional cell signaling inhibition assay, pharmacokinetic profiling\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — structure-guided design with functional validation of receptor-ligand interaction inhibition\",\n      \"pmids\": [\"41066664\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GFRAL is a GPI-anchored receptor restricted predominantly to area postrema and NTS neurons in the hindbrain that binds GDF15 with high affinity and obligatorily recruits the co-receptor RET to transduce intracellular signals; this GFRAL-RET complex mediates GDF15-driven suppression of food intake and body weight via aversive/anorectic neural circuits (projecting to CGRP-PBN neurons and downstream BDNF-mNTS neurons), while also regulating hepatic glucose production, lipid metabolism through a peripheral sympathetic-lipolytic axis, thermoregulation, and neuroimmune responses; GFRAL surface availability is negatively regulated by MT1-MMP-mediated proteolytic cleavage during obesity, providing a feedback mechanism that limits GDF15 sensitivity.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"GFRAL is the obligate high-affinity receptor for the stress-responsive cytokine GDF15, functioning as a hindbrain-restricted signaling hub that transduces metabolic, behavioral, and neuroimmune signals through recruitment of the co-receptor RET [PMID:28846097, PMID:28846098, PMID:28846099]. Expressed predominantly on area postrema and nucleus of the solitary tract neurons, GFRAL–RET activation suppresses food intake via projections to CGRP-expressing parabrachial nucleus neurons and downstream BDNF-mNTS neurons, while simultaneously regulating hepatic glucose production, peripheral sympathetic lipolysis, thermoregulation, and autoimmune T cell responses through β-adrenergic splenic signaling [PMID:33593916, PMID:32661391, PMID:38064571, PMID:38507407, PMID:39737892, PMID:41540266]. GFRAL surface availability is negatively regulated by MT1-MMP–mediated proteolytic cleavage, which is upregulated during obesity and limits GDF15 sensitivity; genetic ablation of MT1-MMP in GFRAL-positive neurons restores receptor expression and attenuates weight gain [PMID:35177851]. GFRAL signaling also mediates chemotherapy-induced fatigue, mitochondrial stress-driven anorexia and anxiety, and cachexia-associated wasting in neurodegenerative disease models [PMID:36427806, PMID:36271504, PMID:39672239].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Before GDF15 was identified as its ligand, GFRAL (then called GRAL) was shown to localize to the plasma membrane and to exert a neuroprotective anti-apoptotic effect by inhibiting JNK signaling, establishing it as a neuronal surface receptor with survival functions.\",\n      \"evidence\": \"Overexpression in PC12 cells and hippocampal neurons with subcellular fractionation and JNK pathway analysis\",\n      \"pmids\": [\"16086688\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Overexpression system without identified ligand limits physiological interpretation\",\n        \"JNK inhibition mechanism not connected to any upstream signal\",\n        \"No in vivo confirmation of neuroprotective role\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The central breakthrough came when four independent groups simultaneously identified GFRAL as the high-affinity receptor for GDF15, demonstrated that GFRAL obligatorily recruits co-receptor RET for signal transduction, and showed that GFRAL expression is restricted to area postrema/NTS neurons — resolving the long-standing mystery of how circulating GDF15 suppresses food intake and body weight.\",\n      \"evidence\": \"Radioligand binding, Gfral knockout mice, cell-based co-receptor signaling assays, in situ hybridization across species\",\n      \"pmids\": [\"28846097\", \"28846098\", \"28846099\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Downstream intracellular signaling cascades beyond RET phosphorylation were not fully mapped\",\n        \"Whether GFRAL functions outside the CNS was not addressed\",\n        \"Crystal structure of the ternary GDF15–GFRAL–RET complex not yet determined\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Regional shRNA knockdown quantitatively demonstrated that GFRAL in AP/NTS neurons is both necessary and sufficient for resistance to diet-induced obesity, with adiposity proportional to knockdown efficiency, confirming the anatomical site of action.\",\n      \"evidence\": \"AAV-shRNA knockdown in AP/NTS with quantitative immunostaining and metabolic phenotyping\",\n      \"pmids\": [\"31152154\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Neuronal subtypes within AP/NTS expressing GFRAL were not resolved\",\n        \"Downstream circuit targets of GFRAL neurons remained uncharacterized\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Antagonistic anti-GFRAL antibody blockade and genetic/pharmacological ablation of peripheral sympathetic nerves revealed that GFRAL–RET signaling drives weight loss partly through a peripheral sympathetic-lipolytic axis involving adipose triglyceride lipase, extending the pathway beyond central anorexia to peripheral lipid mobilization.\",\n      \"evidence\": \"Anti-GFRAL monoclonal antibody, chemical sympathectomy, ATGL knockout mice, adipose gene expression profiling\",\n      \"pmids\": [\"32661391\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Neural pathway from brainstem GFRAL neurons to sympathetic outflow not anatomically traced\",\n        \"Relative contributions of anorexia versus lipolysis to total weight loss not dissected\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"GFRAL was detected on endothelial cells where it mediates GDF15-induced proangiogenic signaling via MEK/ERK and PI3K/Akt, suggesting GFRAL function beyond the CNS.\",\n      \"evidence\": \"siRNA knockdown in endothelial cells with tube formation and sprouting assays\",\n      \"pmids\": [\"33151561\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Endothelial GFRAL expression not confirmed at protein level in vivo\",\n        \"Whether RET is the co-receptor in this context was not tested\",\n        \"Single-lab finding not independently replicated\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Circuit-level dissection using Gfral-Cre mice revealed that GFRAL neurons project predominantly to CGRP-expressing parabrachial nucleus neurons, and silencing these downstream neurons abolished GDF15-induced aversion and anorexia, establishing the first defined neural circuit for GDF15 action.\",\n      \"evidence\": \"Chemogenetic/optogenetic activation of Gfral-Cre neurons, TRAP-Seq, conditional CGRP-PBN silencing, conditioned taste aversion assays\",\n      \"pmids\": [\"33593916\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Other downstream targets of GFRAL neurons beyond PBN were not explored\",\n        \"Whether metabolic effects (glucose, lipid) require CGRP-PBN neurons was not tested\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"MT1-MMP was identified as an endogenous negative regulator that proteolytically cleaves GFRAL on neuronal surfaces, with obesity-driven MT1-MMP upregulation explaining reduced GDF15 sensitivity; cell-type-specific MT1-MMP deletion restored GFRAL and protected against weight gain.\",\n      \"evidence\": \"Proteolytic cleavage assays, conditional MT1-MMP knockout in GFRAL+ neurons, metabolic phenotyping\",\n      \"pmids\": [\"35177851\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Exact cleavage site on GFRAL not mapped\",\n        \"Whether shed GFRAL ectodomain acts as a decoy receptor is unknown\",\n        \"Signals upstream of MT1-MMP activation in obesity not identified\"\n      ]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Beyond food intake, GFRAL was shown to mediate chemotherapy-induced behavioral fatigue and mitochondrial stress-induced anorexia with anxiety, broadening its role to sickness behavior and stress-associated affective changes.\",\n      \"evidence\": \"Anti-GFRAL antibody in cisplatin-treated mice (wheel running); Gfral KO crossed with muscle mitochondrial dysfunction model (anxiety assays, CRH expression)\",\n      \"pmids\": [\"36427806\", \"36271504\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Specific neuronal populations mediating fatigue versus anorexia versus anxiety not dissected\",\n        \"CRH induction pathway downstream of GFRAL not fully characterized\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Biochemical and pharmacological dissection of the GDF15–GFRAL binding interface via peptide arrays and designed antagonists (including the GRASP peptide) defined the extracellular interaction surface and provided proof-of-concept that GFRAL blockade attenuates GDF15-induced nausea in vivo.\",\n      \"evidence\": \"SPOT peptide arrays, surface plasmon resonance, peptide antagonist in rat cisplatin nausea model, GFRAL on platelets by immunoprecipitation and receptor microarray\",\n      \"pmids\": [\"37495041\", \"37506293\", \"38254638\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"High-resolution co-crystal structure of antagonist–GFRAL complex not available\",\n        \"Platelet GFRAL function in vivo physiological hemostasis not confirmed\",\n        \"Selectivity of peptide antagonists over related GDNF-family receptors not fully addressed\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Direct infusion of GDF15 into the area postrema demonstrated that GFRAL activation acutely lowers hepatic glucose production and increases insulin sensitivity independent of food intake or weight change, establishing a food-intake-independent metabolic role, while cell-specific GFRAL neuron activation revealed a torpor-like state encompassing hypothermia, fuel switching, and stress hormone release.\",\n      \"evidence\": \"Stereotaxic AP infusion with hyperinsulinemic-euglycemic clamp and GFRAL knockdown; chemogenetic activation of GFRAL+ neurons with metabolomics and transcriptomics\",\n      \"pmids\": [\"38064571\", \"38507407\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Efferent pathways from AP GFRAL neurons to liver not anatomically traced\",\n        \"Whether torpor-like response is physiologically relevant outside experimental activation is unclear\",\n        \"Integration with other glucose-regulatory circuits (e.g., GLP-1) not defined\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"BDNF-expressing medial NTS neurons were positioned downstream of GFRAL neurons in a hierarchical circuit required for GDF15-induced weight reduction and fatty acid oxidation, and GFRAL knockdown in an ALS model ameliorated wasting and prolonged survival, linking the pathway to neurodegenerative cachexia.\",\n      \"evidence\": \"Genetic circuit tracing and conditional neuron ablation/activation for BDNF-mNTS; shRNA-mediated GFRAL knockdown in hSOD1-G93A ALS mice with survival and motor analysis\",\n      \"pmids\": [\"39737892\", \"39672239\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"How BDNF-mNTS neurons integrate GDF15 versus GLP-1 signals is unknown\",\n        \"Therapeutic window for GFRAL blockade in ALS (beneficial weight preservation versus loss of metabolic regulation) not defined\"\n      ]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"GDF15–GFRAL signaling was shown to suppress autoimmune T cell responses via a brain-to-spleen neuroimmune circuit involving β-adrenergic signaling and norepinephrine-dependent downregulation of T cell integrins, revealing an immunomodulatory function of GFRAL beyond metabolism.\",\n      \"evidence\": \"Gfral knockout mice in EAE, neuronal gene delivery, chemogenetic activation, norepinephrine and integrin measurements\",\n      \"pmids\": [\"41540266\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether this neuroimmune axis operates in non-autoimmune inflammatory contexts is untested\",\n        \"Identity of the sympathetic relay neurons between brainstem and spleen not resolved\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the high-resolution structure of the ternary GDF15–GFRAL–RET complex, the full intracellular signaling cascade downstream of RET in GFRAL neurons, the precise efferent neural pathways from GFRAL neurons to peripheral organs (liver, sympathetic chain, spleen), and the physiological relevance of GFRAL expression outside the CNS (endothelial cells, platelets).\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No high-resolution ternary complex structure available\",\n        \"Intracellular signaling beyond RET/ERK/AKT phosphorylation in GFRAL neurons remains unmapped\",\n        \"Peripheral (non-neuronal) GFRAL functions lack in vivo validation\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1, 5]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 5, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 0, 1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 5, 12]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [16]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [2, 4, 6, 14]}\n    ],\n    \"complexes\": [\n      \"GFRAL–RET signaling complex\"\n    ],\n    \"partners\": [\n      \"GDF15\",\n      \"RET\",\n      \"MMP14\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}