{"gene":"RSPO1","run_date":"2026-06-10T07:46:28","timeline":{"discoveries":[{"year":2011,"finding":"LGR4 and LGR5 associate with the Frizzled/LRP Wnt receptor complex and mediate RSPO1-dependent enhancement of canonical WNT3A signaling; removal of LGR4 abrogates RSPO1-mediated signal enhancement, which is rescued by re-expression of LGR4, -5, or -6, establishing LGR4/5/6 as facultative Wnt receptor components required for R-spondin signaling.","method":"Mass spectrometry (complex identification), conditional gene deletion in mouse gut, HEK293 cell rescue experiments, intestinal crypt culture organoids","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP/MS plus genetic rescue in multiple systems, replicated across cellular and in vivo contexts","pmids":["21727895"],"is_preprint":false},{"year":2011,"finding":"RSPO1 binds to LGR4 and LGR5 through its Furin domains, and LGR4/LGR5 promote RSPO1-mediated Wnt/β-catenin signaling; internalization via Clathrin (but not Caveolin) is required for R-spondin-triggered β-catenin signaling, distinguishing its endocytic mechanism from Wnt3a-mediated signaling.","method":"Gain- and loss-of-function experiments in mammalian cells and Xenopus embryos, Clathrin/Caveolin inhibition assays, binding assays","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — orthogonal genetic and pharmacological approaches in two biological systems, clear mechanistic distinction from Wnt3a pathway","pmids":["21909076"],"is_preprint":false},{"year":2008,"finding":"RSPO1 controls ovarian differentiation in XX gonads by activating the canonical β-catenin signaling pathway; Rspo1 knockout mice show masculinized gonads with absent female-specific Wnt4 activation, XY-like vascularization/steroidogenesis, and failure of germ cells to enter meiosis, demonstrating that RSPO1 is an essential regulator of canonical β-catenin signaling for female development.","method":"Rspo1 knockout mouse model, molecular analyses of Wnt4 expression, histological analysis of gonad phenotype","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean loss-of-function mouse knockout with defined molecular pathway (β-catenin/Wnt4) and multiple phenotypic readouts","pmids":["18250098"],"is_preprint":false},{"year":2013,"finding":"Crystal structures of RSPO1 in complex with LGR5 and RNF43 ectodomains reveal that RSPO1 is sandwiched between LGR5 and RNF43: its cysteine-rich domain rod module contacts LGR5 while a hairpin inserts into RNF43; LGR5 does not contact RNF43 but increases RSPO1 affinity for RNF43, supporting LGR5 as an engagement receptor and RNF43 as an effector receptor.","method":"X-ray crystallography of ternary complex","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure of ternary complex with direct functional assignment of engagement vs effector receptor roles","pmids":["23756651"],"is_preprint":false},{"year":2013,"finding":"Multiple crystal structures of the ZNRF3 ectodomain, the Fu1-Fu2 fragment of Rspo2, and their complexes with ZNRF3 and RNF43 ectodomains show that a prominent loop in Fu1 clamps into equivalent grooves in ZNRF3/RNF43; Rspo binding enhances dimerization of ZNRF3 but not RNF43; signaling potency depends on ability to recruit ZNRF3/RNF43 via Fu1 into a complex with LGR receptors that interact via Fu2.","method":"X-ray crystallography, biophysical binding assays, cellular signaling assays, mutagenesis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures plus biophysical and cellular validation with mutagenesis, multiple orthogonal methods","pmids":["24225776"],"is_preprint":false},{"year":2013,"finding":"Crystal structure of R-spondin 1 in complex with the LGR5 ectodomain (2.0 Å and 3.2 Å resolution) shows ecto-LGR5 binds Rspo1 at its concave LRR surface forming a 2:2 complex; a phenylalanine clamp (Phe106/Phe110 of Rspo1 pinching Ala190 of LGR5) is critical for binding; anonychia-related mutations reduce Rspo1 signaling but not LGR5 binding.","method":"X-ray crystallography, binding assays, mutagenesis, signaling assays","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure plus mutagenesis with functional validation, multiple orthogonal methods","pmids":["23809763"],"is_preprint":false},{"year":2013,"finding":"Crystal structure of LGR4 ECD with RSPO1 N-terminal fragment (containing both FU-CRD1 and FU-CRD2) shows that LGR4 uses its concave surface to bind RSPO1-2F; both furin-like cysteine-rich domains of RSPO1 contribute to LGR4 interaction; all RSPO1-binding residues are conserved in LGR4-6, explaining promiscuous R-spondin binding.","method":"X-ray crystallography, binding assays, mutagenesis","journal":"Genes & development","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with binding and cellular functional assays, identifies critical residues","pmids":["23756652"],"is_preprint":false},{"year":2013,"finding":"R-spondin interacts with ZNRF3/RNF43 and LGR4 through distinct motifs; both LGR4-binding and ZNRF3-binding motifs of R-spondin are required for LGR4/ZNRF3 interaction, membrane clearance of ZNRF3, and Wnt signaling activation; R-spondin primarily functions by binding and inhibiting ZNRF3, with LGR4/5 serving as engagement receptors and ZNRF3/RNF43 as effector receptors.","method":"Mutational analysis of R-spondin binding motifs, ZNRF3 membrane clearance assay, Wnt signaling reporter assays","journal":"EMBO reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal mutagenesis mapping two distinct binding interfaces with functional readouts across multiple assays","pmids":["24165923"],"is_preprint":false},{"year":2012,"finding":"RSPO1 potentiates Wnt/β-catenin signaling through LGR4 and LGR5; siRNA screen identified LGR4 as a specific receptor for RSPO; depletion of LGR4 completely abolished RSPO-induced β-catenin signaling; RSPO binds the extracellular domain of LGR4 and LGR5; LGR4 overexpression sensitizes cells to RSPO; no G-protein coupling of LGR4 was detected in RSPO-treated cells.","method":"Unbiased siRNA screen, binding assays, overexpression rescue, signaling reporter assays, G-protein coupling assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — unbiased screen plus multiple orthogonal functional validations; G-protein-independent mechanism established by negative coupling result","pmids":["22815884"],"is_preprint":false},{"year":2008,"finding":"All four R-spondin family members activate canonical Wnt signaling via a common mechanism requiring Wnt ligands and LRP6; the cysteine-rich furin domains are sufficient and essential for Wnt amplification; RSPOs antagonize DKK1 by interfering with DKK1-mediated LRP6/Kremen association, suggesting that Wnt amplification by RSPOs may occur through DKK1 inhibition.","method":"Deletion mutant analysis, TOPFLASH reporter assay, DKK1 antagonism assays, LRP6/Kremen interaction assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic domain deletion analysis plus mechanistic epistasis experiments across all four family members","pmids":["18400942"],"is_preprint":false},{"year":2011,"finding":"RSPO1 activates the WNT/β-catenin signaling pathway in germ cells of XX gonads; in Rspo1(-/-) XX gonads, germ cell proliferation, Stra8 expression (early meiotic marker), and entry into meiosis are all impaired, and germ cell sex reversal occurs prior to Sertoli cell differentiation, indicating β-catenin signaling acts within germ cells to promote oogonial differentiation.","method":"Mouse knockout model (Rspo1-/-), meiosis markers, histological analysis, epistasis with somatic cell differentiation","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic KO with defined cellular phenotype and molecular pathway placement across multiple readouts","pmids":["21991325"],"is_preprint":false},{"year":2012,"finding":"Simultaneous ablation of Rspo1 and Wnt4 impairs proliferation of coelomic epithelium cells in early XY gonads, reducing progenitors of Sertoli cells and resulting in hypoplastic testis; individual knockouts do not show this phenotype, establishing RSPO1 and WNT4 as functionally cooperative regulators of gonadal progenitor proliferation independent of sex.","method":"Double knockout mouse model (Wnt4-/-;Rspo1-/-), histological and cell proliferation analysis","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with double knockout revealing cooperative function not apparent in single knockouts","pmids":["23095882"],"is_preprint":false},{"year":2013,"finding":"RSPO1 reconstitutes a ternary complex with LGR4 and ZNRF3; RSPO proteins bind LGR4 with nanomolar affinities in decreasing order RSPO4 > RSPO2 > RSPO3 > RSPO1; RSPO2 and RSPO3 form detectable ternary RSPO:LGR4:ZNRF3 complexes, while RSPO4:ZNRF3 complexes were not detected; stronger signaling potency of RSPO2/3 correlates with their stronger binding of both receptors.","method":"In vitro reconstitution with bacterially expressed proteins, TR-FRET binding assay, native gel electrophoresis, cell-based signaling assay","journal":"Biochemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution of ternary complex with purified components, multiple biophysical methods","pmids":["24050775"],"is_preprint":false},{"year":2017,"finding":"RSPO ligands and Wnt ligands have qualitatively distinct, non-interchangeable roles in Lgr5+ intestinal stem cell self-renewal; Wnt proteins maintain RSPO receptor expression (basal competency) while RSPO ligands actively drive stem cell self-renewal and expansion; the default fate of Lgr5+ ISCs is to differentiate unless both RSPO and Wnt ligands are present.","method":"In vivo Lgr5+ ISC fate analysis, gain-of-function with RSPO ligands and non-lipidated Wnt analogue, intestinal organoid culture","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal in vivo and in vitro approaches distinguishing RSPO and Wnt ligand functions","pmids":["28467820"],"is_preprint":false},{"year":2011,"finding":"RSPO1/Wnt signaling promotes developmental angiogenesis via a Vegfc/Vegfr3 pathway; zebrafish rspo1 mutation impairs angiogenesis without affecting primary vasculogenesis; endothelial cell-autonomous inhibition of canonical Wnt signaling blocks angiogenesis; Vegfc expression is dependent on Rspo1 and Wnt; Vegfc and Vegfr3 are necessary downstream of Rspo1-Wnt for angiogenesis.","method":"Zebrafish forward genetic screen, morpholino knockdown, endothelial cell-autonomous Wnt inhibition, epistasis with Vegfc/Vegfr3","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis defining a linear pathway with cell-autonomous experiments and multiple readouts","pmids":["22007135"],"is_preprint":false},{"year":2013,"finding":"Crystal structures of ZNRF3 ectodomain alone and in complex with RSPO1 show ZNRF3 binds RSPO1 via its Fu1 domain with micromolar affinity; the ZNRF3-binding site on RSPO1 Fu2 overlaps with trans-interactions in 2:2 LGR5-RSPO1 complexes, suggesting ZNRF3/RNF43 binding would disrupt such arrangements; anonychia-related mutations in RSPO4 map to the observed interface.","method":"X-ray crystallography, affinity measurements, mutagenesis analysis","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures with biophysical affinity measurements and disease mutation mapping","pmids":["24349440"],"is_preprint":false},{"year":2014,"finding":"Crystal structure of LGR4-Rspo1 complex identifies the concave surface of LGR4 as the sole binding site for R-spondins; Rspo1 adopts a flat β-fold architecture bound through electrostatic and hydrophobic interactions; all Rspo1-binding residues are conserved in LGR4-6; this one-site binding model is mechanistically distinct from LGR1-3 and LGR7-8 ligand recognition.","method":"X-ray crystallography using hybrid LRR technique, binding and cellular assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure with binding validation and mechanistic comparison to related receptors","pmids":["25480784"],"is_preprint":false},{"year":2015,"finding":"Crystal structure of LGR5 complexed with Rspo2 (at high resolution) shows engagement almost identical to RSPO1; LGR5 ectodomain exhibits nearly 9° plasticity in horseshoe fold; low-resolution ternary LGR5-Rspo2-ZNRF3 structure confirms Rspo proteins cross-link LGRs and ZNRF3 into a 2:2:2 complex with ZNRF3, whereas a 1:1:1 complex is formed with RNF43.","method":"X-ray crystallography of binary and ternary complexes","journal":"Journal of structural biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structures of binary and ternary complexes establishing stoichiometry difference between ZNRF3 and RNF43 complexes","pmids":["26123262"],"is_preprint":false},{"year":2014,"finding":"Signaling potency of RSPOs is determined by ternary complex formation ability (dependent on combined LGR4 and ZNRF3 binding); efficacy depends on ZNRF3 recruitment; RSPO2/3/4 have stronger signaling potencies than RSPO1; engineering RSPO2 ZNRF3-binding region onto RSPO4's LGR4-binding region creates a 'Superspondin' with 10-fold enhanced potency; RSPO1 has the weakest ZNRF3 binding among the four members.","method":"Purified protein binding assays, chimeric protein engineering, cell-based signaling assays, mutagenesis","journal":"Molecular pharmacology","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with purified components, chimera engineering with defined functional outcomes, multiple orthogonal assays","pmids":["25504990"],"is_preprint":false},{"year":2020,"finding":"RSPO1 expression in Rspo1(-/-) nephron progenitors (cap mesenchymal cells) is required for mesenchyme-to-epithelial transition (MET) linked to Bmp7 expression, SMAD1/5 phosphorylation, and activation of Lef1, Fgf8, and Wnt4; RSPO1 and RSPO3 act redundantly to permit WNT/β-catenin signaling and nephron progenitor maintenance; surprisingly, full knockout of LGR4/5/6 only mildly affects progenitor numbers but does not interfere with MET, revealing LGR-independent functions for R-spondins.","method":"Tissue-specific conditional knockout (Rspo1/Rspo3 and Lgr4/5/6 in cap mesenchyme), phospho-SMAD analysis, gene expression analysis","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple conditional knockouts with detailed molecular pathway analysis, LGR-independent mechanism revealed by genetic dissection","pmids":["32324134"],"is_preprint":false},{"year":2023,"finding":"RSPO1 inhibits beige adipocyte thermogenesis via LGR4-Wnt/β-catenin signaling; humanized knockin mice with RSPO1 p.R219W mutation show suppressed thermogenesis and obesity; the R219W mutation disrupts RSPO1's electrostatic interaction with the extracellular matrix, causing excessive RSPO1 release that hyperactivates LGR4-Wnt/β-catenin and attenuates mitochondrial respiration and thermogenic capacity in beige adipocytes.","method":"Whole-exome sequencing, knockin mouse model, adipose-specific overexpression, Rspo1 ablation, mechanistic RSPO1 administration to differentiated adipocytes","journal":"Advanced science (Weinheim, Baden-Wurttemberg, Germany)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — humanized knockin plus multiple mechanistic approaches in single study, but some aspects rely on overexpression/administration rather than endogenous manipulation","pmids":["36755192"],"is_preprint":false},{"year":2020,"finding":"In response to hormonal signaling, Amphiregulin (Areg) secreted by ER-positive luminal mammary cells induces RSPO1 expression in ER-negative luminal cells in a paracrine, EGFR-dependent manner, establishing an Estrogen-Areg-Rspo1 regulatory axis controlling RSPO1 expression in the mammary gland.","method":"Conditional cell-type specific analysis, paracrine co-culture experiments, EGFR inhibition, expression analysis","journal":"Developmental biology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — paracrine mechanism established with pharmacological and genetic tools but single lab","pmids":["31610144"],"is_preprint":false},{"year":2017,"finding":"RSPO1 is required for hematopoietic stem cell (HSC) specification in zebrafish through control of two parallel signaling pathways: Wnt16/DeltaC/DeltaD and Vegfa/Tgfβ1; Rspo1 acts upstream of both pathways to coordinate HSC specification with vessel patterning.","method":"Zebrafish genetic analysis, epistasis experiments with Wnt16 and Vegfa pathways","journal":"Development (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis in zebrafish defining upstream pathway position, single lab","pmids":["28087636"],"is_preprint":false},{"year":2013,"finding":"RSPO1 injection into the third brain ventricle of male rats inhibits food intake and decreases neuropeptide Y while increasing proopiomelanocortin expression in the arcuate nucleus; LGR4 (RSPO1 receptor) is expressed in arcuate, ventromedial, and median eminence hypothalamic nuclei colocalizing with NPY, POMC and BDNF neurons; Rspo1 is expressed by neurons and is down-regulated by fasting.","method":"In situ hybridization, intracerebroventricular injection, food intake measurement, gene expression analysis","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — direct localization and functional injection experiments, multiple readouts, single lab","pmids":["24280058"],"is_preprint":false},{"year":2023,"finding":"Bispecific ROTACs (signaling-disabled RSPO chimeras) leverage RSPO specificity for ZNRF3/RNF43 E3 ubiquitin ligases to target degradation of transmembrane proteins; a bispecific RSPO2 chimera (R2PD1) targeting PD-L1 induces lysosomal degradation of PD-L1 strictly dependent on ZNRF3/RNF43, confirming RSPO's mechanistic role in directing ZNRF3/RNF43-mediated lysosomal degradation.","method":"Bispecific protein engineering, PD-L1 degradation assay, ZNRF3/RNF43 dependency assay, T cell reactivation assay","journal":"Cell chemical biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proof-of-concept reconstitution demonstrating ZNRF3/RNF43-dependent mechanism, single lab","pmids":["37321224"],"is_preprint":false},{"year":2004,"finding":"R-spondin (RSPO1) encodes a secreted protein with a thrombospondin type 1 motif expressed in the dorsal neural tube; transfection of epitope-tagged R-spondin into COS7 and 293 cells shows both nuclear and secreted localization, suggesting processing-dependent localization; its expression is reduced in Wnt-1/3a double-knockout mice, placing it downstream of Wnt-1/3a signaling.","method":"Northern blot, in situ hybridization, epitope-tag transfection/fractionation, Wnt-1/3a double knockout expression analysis","journal":"Biochimica et biophysica acta","confidence":"Low","confidence_rationale":"Tier 3 / Weak — initial characterization with single subcellular localization experiment and one genetic association, foundational but limited mechanistic depth","pmids":["14732490"],"is_preprint":false},{"year":2011,"finding":"RSPO1 augments β-catenin signaling in a dose-dependent manner; co-transfection of RSPO1 with CTNNB1 (β-catenin) results in ~10-fold synergistic activation of a TOPFLASH reporter; wild-type RSPO1 shows strong nuclear localization in several cell lines; an individual with a RSPO1 splice mutation shows reduced β-catenin protein and WNT4 mRNA in ovotestis tissue.","method":"TOPFLASH reporter transfection assay, subcellular localization (nuclear staining), patient tissue analysis","journal":"PloS one","confidence":"Low","confidence_rationale":"Tier 3 / Weak — reporter assay and localization without mechanistic follow-up; nuclear localization finding is potentially important but not mechanistically resolved","pmids":["21297984"],"is_preprint":false},{"year":2020,"finding":"RSPO1 overexpression in ApcMin/+ mice increases apoptosis and reduces Wnt signaling and proliferation in adenomas; this effect is mediated in part through activation of TGFβ/SMAD2 signaling, as TGFBR inhibition restores organoid formation and Wnt target gene expression suppressed by RSPO1; RSPO1 thus activates a cross-talk between Wnt and TGFβ pathways in adenoma cells.","method":"AAV-RSPO1-Fc delivery to ApcMin/+ mice, organoid culture with RSPO1 and TGFBR inhibitor, scRNA-seq, immunohistochemistry, phospho-SMAD2 analysis","journal":"Gastroenterology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro evidence for RSPO1-TGFβ pathway cross-talk, multiple readouts, single lab","pmids":["32941878"],"is_preprint":false},{"year":2020,"finding":"Rspo1/Rspo3-LGR4 signaling in hepatocytes inhibits cholesterol synthesis via the AMPKα-SREBP2 pathway; Rspo1 increases phosphorylation of AMPKα Thr172, reducing SREBP2 nuclear translocation; hepatic LGR4 knockdown increases cholesterol synthesis and decreases AMPKα phosphorylation; AMPKα knockdown abrogates Rspo1-induced inhibition of cholesterol synthesis.","method":"LGR4/Rspo1/Rspo3 knockdown mice, AMPKα agonist/antagonist/shRNA epistasis, SREBP2 nuclear translocation assay, phospho-AMPKα analysis","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis experiments linking LGR4 to AMPKα-SREBP2, multiple genetic tools, single lab","pmids":["32926477"],"is_preprint":false},{"year":2023,"finding":"LGR4 and LGR5 form distinct homodimers; only LGR4 (not LGR5) complexes with RNF43/ZNRF3 to provide high-affinity bivalent binding of RSPO ligands; co-expression of ZNRF3 with LGR4 greatly increases binding affinity for monovalent RSPO2 furin domain, whereas co-expression with LGR5 has no effect, establishing distinct receptor complex architectures that explain differential RSPO signaling through LGR4 vs LGR5.","method":"Binding affinity assays with monovalent and bivalent RSPO in whole cells, co-expression experiments, structural modeling","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — quantitative binding in cellular context with mechanistic interpretation, single lab","pmids":["37402772"],"is_preprint":false}],"current_model":"RSPO1 is a secreted glycoprotein that potentiates canonical Wnt/β-catenin signaling by bridging LGR4/5/6 (engagement receptors) with the transmembrane E3 ubiquitin ligases ZNRF3/RNF43 (effector receptors) through its furin-like (Fu1/Fu2) domains, forming a ternary complex that clears ZNRF3/RNF43 from the cell surface and thereby protects Frizzled/LRP Wnt receptor complexes from ubiquitin-mediated degradation; structural studies define the binding interfaces, and RSPO1's signaling potency is weaker than RSPO2/3 due to its lower affinity for ZNRF3; in vivo, RSPO1 is essential for ovarian differentiation (via β-catenin activation opposing Sox9/testis fate), germ cell meiosis, nephron progenitor maintenance, hematopoietic stem cell specification, and intestinal stem cell self-renewal, where it cooperates non-interchangeably with Wnt ligands."},"narrative":{"mechanistic_narrative":"RSPO1 is a secreted glycoprotein that amplifies canonical Wnt/β-catenin signaling by acting as a molecular bridge between two receptor classes, and through this activity governs gonadal sex determination, stem cell maintenance, and tissue morphogenesis [PMID:21909076, PMID:18250098, PMID:18400942]. Its tandem furin-like cysteine-rich domains carry out distinct binding functions: Fu2 engages the concave leucine-rich-repeat surface of the LGR4/5/6 receptors, while Fu1 clamps into equivalent grooves on the transmembrane E3 ubiquitin ligases ZNRF3/RNF43, and both interfaces are required to assemble a ternary complex, clear ZNRF3/RNF43 from the cell surface, and activate signaling [PMID:23756651, PMID:24225776, PMID:24165923, PMID:25480784]. Within this architecture LGR4/5/6 serve as engagement receptors that increase RSPO1 affinity for the effector receptors ZNRF3/RNF43, and RSPO1's comparatively weak ZNRF3 binding makes it the least potent family member [PMID:23756651, PMID:24050775, PMID:25504990]; this ZNRF3/RNF43-directed lysosomal degradation activity is sufficiently modular that signaling-disabled RSPO chimeras can be repurposed to degrade unrelated transmembrane targets [PMID:37321224]. RSPO1 requires Wnt ligands and LRP6 for Wnt amplification and provides a self-renewal signal non-interchangeable with that of Wnt in Lgr5+ intestinal stem cells [PMID:18400942, PMID:28467820]. In vivo, RSPO1 is an essential driver of XX ovarian differentiation, activating β-catenin and Wnt4 to oppose testis fate and to promote germ cell entry into meiosis, and it cooperates with WNT4 in gonadal progenitor proliferation [PMID:18250098, PMID:21991325, PMID:23095882]. RSPO1 additionally supports developmental angiogenesis and hematopoietic stem cell specification, and it operates partly through LGR-independent and TGFβ/SMAD cross-talk routes in nephron progenitor maintenance and intestinal adenomas [PMID:22007135, PMID:28087636, PMID:32324134, PMID:32941878].","teleology":[{"year":2004,"claim":"Established RSPO1 as a secreted Wnt-responsive protein, placing it within the Wnt circuitry before its receptor mechanism was known.","evidence":"Expression analysis and epitope-tag fractionation in cell lines and Wnt-1/3a double-knockout mice","pmids":["14732490"],"confidence":"Low","gaps":["Single localization experiment with ambiguous nuclear/secreted partition","No receptor or biochemical mechanism defined","Functional role inferred only from expression dependence"]},{"year":2008,"claim":"Defined the minimal signaling unit and an early mechanistic model, showing the furin domains are sufficient and essential for Wnt amplification across all four family members.","evidence":"Domain deletion analysis and TOPFLASH/DKK1 antagonism assays for all R-spondins","pmids":["18400942"],"confidence":"High","gaps":["DKK1-inhibition model later superseded by the LGR/ZNRF3 receptor mechanism","Did not identify the engagement receptor"]},{"year":2008,"claim":"Demonstrated the central in vivo role of RSPO1 in female sex determination, linking it to β-catenin/Wnt4 activation opposing testis fate.","evidence":"Rspo1 knockout mouse with gonadal histology and Wnt4 expression analysis","pmids":["18250098"],"confidence":"High","gaps":["Receptor mediating the gonadal effect not identified at this stage","Cell-autonomy within germ vs somatic cells not resolved here"]},{"year":2011,"claim":"Identified LGR4/5/6 as the facultative Wnt-receptor components required for RSPO signaling, resolving how RSPO is sensed at the membrane.","evidence":"Mass spectrometry of receptor complexes, conditional deletion and rescue in mouse gut and HEK293, organoid culture; binding and clathrin-dependence assays in cells and Xenopus","pmids":["21727895","21909076"],"confidence":"High","gaps":["Effector that translates LGR engagement into Wnt potentiation not yet defined","Did not explain differential potency among RSPO family members"]},{"year":2011,"claim":"Placed β-catenin signaling cell-autonomously within germ cells, refining the gonadal model to show RSPO1 promotes oogonial differentiation and meiotic entry.","evidence":"Rspo1-/- XX gonad analysis with Stra8 and meiosis markers and epistasis to somatic differentiation","pmids":["21991325"],"confidence":"High","gaps":["Direct germ-cell receptor not identified","Quantitative contribution of germ vs somatic signaling unresolved"]},{"year":2012,"claim":"Independently confirmed LGR4 as a specific, G-protein-independent RSPO receptor via unbiased screening.","evidence":"siRNA screen, binding, overexpression, reporter, and G-protein coupling assays","pmids":["22815884"],"confidence":"High","gaps":["Mechanism downstream of LGR4 binding still unexplained","Effector receptor not yet incorporated"]},{"year":2012,"claim":"Revealed cooperative, sex-independent function of RSPO1 with WNT4 in gonadal progenitor proliferation, exposed only by combined loss.","evidence":"Wnt4-/-;Rspo1-/- double knockout with proliferation and histology","pmids":["23095882"],"confidence":"High","gaps":["Molecular basis of WNT4/RSPO1 cooperativity not dissected","Receptor usage in progenitors not defined"]},{"year":2013,"claim":"Established the two-receptor mechanism structurally and functionally: RSPO1 bridges LGR (engagement) and ZNRF3/RNF43 (effector) E3 ligases through distinct Fu2 and Fu1 interfaces, clearing the ligases to protect Wnt receptors.","evidence":"Multiple crystal structures of binary and ternary complexes plus mutagenesis, biophysics, membrane-clearance and reporter assays","pmids":["23756651","24225776","23809763","23756652","24165923","24349440","24050775"],"confidence":"High","gaps":["Stoichiometric differences between ZNRF3 and RNF43 complexes not yet resolved","Family-wide potency determinants only partially quantified"]},{"year":2014,"claim":"Defined potency determinants quantitatively, showing signaling strength scales with ternary-complex formation and that RSPO1 has the weakest ZNRF3 binding of the family.","evidence":"Purified-protein binding, chimera ('Superspondin') engineering, and cell signaling assays; LGR4 single-site structure","pmids":["25504990","25480784"],"confidence":"High","gaps":["Why RSPO1 evolved lower ZNRF3 affinity not addressed","In vivo consequence of potency differences not tested here"]},{"year":2015,"claim":"Resolved complex stoichiometry, showing RSPO cross-links LGR and ZNRF3 into a 2:2:2 assembly versus 1:1:1 with RNF43.","evidence":"Crystal structures of binary and ternary LGR5-Rspo-ZNRF3/RNF43 complexes","pmids":["26123262"],"confidence":"High","gaps":["Functional consequence of distinct ZNRF3 vs RNF43 stoichiometry not fully defined"]},{"year":2017,"claim":"Distinguished RSPO and Wnt ligand functions, showing they are non-interchangeable in Lgr5+ intestinal stem cell self-renewal.","evidence":"In vivo ISC fate analysis with RSPO and non-lipidated Wnt analogue and organoid culture","pmids":["28467820"],"confidence":"High","gaps":["Molecular basis of qualitative difference between RSPO and Wnt inputs not resolved"]},{"year":2017,"claim":"Extended RSPO1 function to hematopoietic stem cell specification and angiogenesis, placing it upstream of parallel Wnt/Notch and Vegf signaling.","evidence":"Zebrafish genetics and epistasis with Wnt16/DeltaC/DeltaD, Vegfa/Tgfβ1 and Vegfc/Vegfr3","pmids":["28087636","22007135"],"confidence":"Medium","gaps":["Receptor mediating these effects not defined in zebrafish","Conservation of HSC role in mammals not established here"]},{"year":2020,"claim":"Uncovered LGR-independent and TGFβ-crosstalk functions, showing RSPO1 maintains nephron progenitors and restrains adenoma growth through non-canonical routes.","evidence":"Conditional Rspo1/Rspo3 and Lgr4/5/6 knockouts with phospho-SMAD analysis; AAV-RSPO1 delivery to ApcMin/+ mice with organoid TGFBR inhibition","pmids":["32324134","32941878"],"confidence":"High","gaps":["Receptor mediating LGR-independent activity unidentified","Direct link between RSPO1 and SMAD signaling not biochemically defined"]},{"year":2023,"claim":"Demonstrated the modularity and physiological breadth of RSPO1's ZNRF3/RNF43-directed degradation activity, from engineered target degradation to metabolic regulation.","evidence":"Bispecific ROTAC PD-L1 degradation with ZNRF3/RNF43 dependency; humanized R219W knockin obesity model; AMPKα-SREBP2 epistasis in hepatocytes; cellular LGR4 vs LGR5 complex-architecture binding","pmids":["37321224","36755192","32926477","37402772"],"confidence":"Medium","gaps":["Several metabolic findings rely on overexpression/administration rather than endogenous manipulation","Single-lab observations awaiting independent confirmation","Mechanistic link between LGR4 engagement and AMPKα not biochemically resolved"]},{"year":null,"claim":"The identity of the receptor(s) mediating RSPO1's LGR-independent and TGFβ/SMAD-coupled functions, and the basis of the reported nuclear localization, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No receptor identified for LGR-independent activity","Nuclear localization role and processing not mechanistically resolved","Crosstalk to TGFβ/AMPK pathways lacks a defined biochemical intermediary"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[1,7,9,18]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,8]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[3,7,24]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[25]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,7]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,8,9]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[2,11,14,22]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[2,10]}],"complexes":["RSPO1–LGR4/5/6–ZNRF3/RNF43 ternary complex"],"partners":["LGR4","LGR5","LGR6","ZNRF3","RNF43","LRP6","WNT4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q2MKA7","full_name":"R-spondin-1","aliases":["Roof plate-specific spondin-1","hRspo1"],"length_aa":263,"mass_kda":29.0,"function":"Activator of the canonical Wnt signaling pathway by acting as a ligand for LGR4-6 receptors (PubMed:29769720). 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removal of LGR4 abrogates RSPO1-mediated signal enhancement, which is rescued by re-expression of LGR4, -5, or -6, establishing LGR4/5/6 as facultative Wnt receptor components required for R-spondin signaling.\",\n      \"method\": \"Mass spectrometry (complex identification), conditional gene deletion in mouse gut, HEK293 cell rescue experiments, intestinal crypt culture organoids\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP/MS plus genetic rescue in multiple systems, replicated across cellular and in vivo contexts\",\n      \"pmids\": [\"21727895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RSPO1 binds to LGR4 and LGR5 through its Furin domains, and LGR4/LGR5 promote RSPO1-mediated Wnt/β-catenin signaling; internalization via Clathrin (but not Caveolin) is required for R-spondin-triggered β-catenin signaling, distinguishing its endocytic mechanism from Wnt3a-mediated signaling.\",\n      \"method\": \"Gain- and loss-of-function experiments in mammalian cells and Xenopus embryos, Clathrin/Caveolin inhibition assays, binding assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — orthogonal genetic and pharmacological approaches in two biological systems, clear mechanistic distinction from Wnt3a pathway\",\n      \"pmids\": [\"21909076\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"RSPO1 controls ovarian differentiation in XX gonads by activating the canonical β-catenin signaling pathway; Rspo1 knockout mice show masculinized gonads with absent female-specific Wnt4 activation, XY-like vascularization/steroidogenesis, and failure of germ cells to enter meiosis, demonstrating that RSPO1 is an essential regulator of canonical β-catenin signaling for female development.\",\n      \"method\": \"Rspo1 knockout mouse model, molecular analyses of Wnt4 expression, histological analysis of gonad phenotype\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean loss-of-function mouse knockout with defined molecular pathway (β-catenin/Wnt4) and multiple phenotypic readouts\",\n      \"pmids\": [\"18250098\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structures of RSPO1 in complex with LGR5 and RNF43 ectodomains reveal that RSPO1 is sandwiched between LGR5 and RNF43: its cysteine-rich domain rod module contacts LGR5 while a hairpin inserts into RNF43; LGR5 does not contact RNF43 but increases RSPO1 affinity for RNF43, supporting LGR5 as an engagement receptor and RNF43 as an effector receptor.\",\n      \"method\": \"X-ray crystallography of ternary complex\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure of ternary complex with direct functional assignment of engagement vs effector receptor roles\",\n      \"pmids\": [\"23756651\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Multiple crystal structures of the ZNRF3 ectodomain, the Fu1-Fu2 fragment of Rspo2, and their complexes with ZNRF3 and RNF43 ectodomains show that a prominent loop in Fu1 clamps into equivalent grooves in ZNRF3/RNF43; Rspo binding enhances dimerization of ZNRF3 but not RNF43; signaling potency depends on ability to recruit ZNRF3/RNF43 via Fu1 into a complex with LGR receptors that interact via Fu2.\",\n      \"method\": \"X-ray crystallography, biophysical binding assays, cellular signaling assays, mutagenesis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures plus biophysical and cellular validation with mutagenesis, multiple orthogonal methods\",\n      \"pmids\": [\"24225776\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structure of R-spondin 1 in complex with the LGR5 ectodomain (2.0 Å and 3.2 Å resolution) shows ecto-LGR5 binds Rspo1 at its concave LRR surface forming a 2:2 complex; a phenylalanine clamp (Phe106/Phe110 of Rspo1 pinching Ala190 of LGR5) is critical for binding; anonychia-related mutations reduce Rspo1 signaling but not LGR5 binding.\",\n      \"method\": \"X-ray crystallography, binding assays, mutagenesis, signaling assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure plus mutagenesis with functional validation, multiple orthogonal methods\",\n      \"pmids\": [\"23809763\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structure of LGR4 ECD with RSPO1 N-terminal fragment (containing both FU-CRD1 and FU-CRD2) shows that LGR4 uses its concave surface to bind RSPO1-2F; both furin-like cysteine-rich domains of RSPO1 contribute to LGR4 interaction; all RSPO1-binding residues are conserved in LGR4-6, explaining promiscuous R-spondin binding.\",\n      \"method\": \"X-ray crystallography, binding assays, mutagenesis\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with binding and cellular functional assays, identifies critical residues\",\n      \"pmids\": [\"23756652\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"R-spondin interacts with ZNRF3/RNF43 and LGR4 through distinct motifs; both LGR4-binding and ZNRF3-binding motifs of R-spondin are required for LGR4/ZNRF3 interaction, membrane clearance of ZNRF3, and Wnt signaling activation; R-spondin primarily functions by binding and inhibiting ZNRF3, with LGR4/5 serving as engagement receptors and ZNRF3/RNF43 as effector receptors.\",\n      \"method\": \"Mutational analysis of R-spondin binding motifs, ZNRF3 membrane clearance assay, Wnt signaling reporter assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal mutagenesis mapping two distinct binding interfaces with functional readouts across multiple assays\",\n      \"pmids\": [\"24165923\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"RSPO1 potentiates Wnt/β-catenin signaling through LGR4 and LGR5; siRNA screen identified LGR4 as a specific receptor for RSPO; depletion of LGR4 completely abolished RSPO-induced β-catenin signaling; RSPO binds the extracellular domain of LGR4 and LGR5; LGR4 overexpression sensitizes cells to RSPO; no G-protein coupling of LGR4 was detected in RSPO-treated cells.\",\n      \"method\": \"Unbiased siRNA screen, binding assays, overexpression rescue, signaling reporter assays, G-protein coupling assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — unbiased screen plus multiple orthogonal functional validations; G-protein-independent mechanism established by negative coupling result\",\n      \"pmids\": [\"22815884\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"All four R-spondin family members activate canonical Wnt signaling via a common mechanism requiring Wnt ligands and LRP6; the cysteine-rich furin domains are sufficient and essential for Wnt amplification; RSPOs antagonize DKK1 by interfering with DKK1-mediated LRP6/Kremen association, suggesting that Wnt amplification by RSPOs may occur through DKK1 inhibition.\",\n      \"method\": \"Deletion mutant analysis, TOPFLASH reporter assay, DKK1 antagonism assays, LRP6/Kremen interaction assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic domain deletion analysis plus mechanistic epistasis experiments across all four family members\",\n      \"pmids\": [\"18400942\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RSPO1 activates the WNT/β-catenin signaling pathway in germ cells of XX gonads; in Rspo1(-/-) XX gonads, germ cell proliferation, Stra8 expression (early meiotic marker), and entry into meiosis are all impaired, and germ cell sex reversal occurs prior to Sertoli cell differentiation, indicating β-catenin signaling acts within germ cells to promote oogonial differentiation.\",\n      \"method\": \"Mouse knockout model (Rspo1-/-), meiosis markers, histological analysis, epistasis with somatic cell differentiation\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic KO with defined cellular phenotype and molecular pathway placement across multiple readouts\",\n      \"pmids\": [\"21991325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Simultaneous ablation of Rspo1 and Wnt4 impairs proliferation of coelomic epithelium cells in early XY gonads, reducing progenitors of Sertoli cells and resulting in hypoplastic testis; individual knockouts do not show this phenotype, establishing RSPO1 and WNT4 as functionally cooperative regulators of gonadal progenitor proliferation independent of sex.\",\n      \"method\": \"Double knockout mouse model (Wnt4-/-;Rspo1-/-), histological and cell proliferation analysis\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with double knockout revealing cooperative function not apparent in single knockouts\",\n      \"pmids\": [\"23095882\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"RSPO1 reconstitutes a ternary complex with LGR4 and ZNRF3; RSPO proteins bind LGR4 with nanomolar affinities in decreasing order RSPO4 > RSPO2 > RSPO3 > RSPO1; RSPO2 and RSPO3 form detectable ternary RSPO:LGR4:ZNRF3 complexes, while RSPO4:ZNRF3 complexes were not detected; stronger signaling potency of RSPO2/3 correlates with their stronger binding of both receptors.\",\n      \"method\": \"In vitro reconstitution with bacterially expressed proteins, TR-FRET binding assay, native gel electrophoresis, cell-based signaling assay\",\n      \"journal\": \"Biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution of ternary complex with purified components, multiple biophysical methods\",\n      \"pmids\": [\"24050775\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RSPO ligands and Wnt ligands have qualitatively distinct, non-interchangeable roles in Lgr5+ intestinal stem cell self-renewal; Wnt proteins maintain RSPO receptor expression (basal competency) while RSPO ligands actively drive stem cell self-renewal and expansion; the default fate of Lgr5+ ISCs is to differentiate unless both RSPO and Wnt ligands are present.\",\n      \"method\": \"In vivo Lgr5+ ISC fate analysis, gain-of-function with RSPO ligands and non-lipidated Wnt analogue, intestinal organoid culture\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal in vivo and in vitro approaches distinguishing RSPO and Wnt ligand functions\",\n      \"pmids\": [\"28467820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RSPO1/Wnt signaling promotes developmental angiogenesis via a Vegfc/Vegfr3 pathway; zebrafish rspo1 mutation impairs angiogenesis without affecting primary vasculogenesis; endothelial cell-autonomous inhibition of canonical Wnt signaling blocks angiogenesis; Vegfc expression is dependent on Rspo1 and Wnt; Vegfc and Vegfr3 are necessary downstream of Rspo1-Wnt for angiogenesis.\",\n      \"method\": \"Zebrafish forward genetic screen, morpholino knockdown, endothelial cell-autonomous Wnt inhibition, epistasis with Vegfc/Vegfr3\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis defining a linear pathway with cell-autonomous experiments and multiple readouts\",\n      \"pmids\": [\"22007135\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Crystal structures of ZNRF3 ectodomain alone and in complex with RSPO1 show ZNRF3 binds RSPO1 via its Fu1 domain with micromolar affinity; the ZNRF3-binding site on RSPO1 Fu2 overlaps with trans-interactions in 2:2 LGR5-RSPO1 complexes, suggesting ZNRF3/RNF43 binding would disrupt such arrangements; anonychia-related mutations in RSPO4 map to the observed interface.\",\n      \"method\": \"X-ray crystallography, affinity measurements, mutagenesis analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures with biophysical affinity measurements and disease mutation mapping\",\n      \"pmids\": [\"24349440\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Crystal structure of LGR4-Rspo1 complex identifies the concave surface of LGR4 as the sole binding site for R-spondins; Rspo1 adopts a flat β-fold architecture bound through electrostatic and hydrophobic interactions; all Rspo1-binding residues are conserved in LGR4-6; this one-site binding model is mechanistically distinct from LGR1-3 and LGR7-8 ligand recognition.\",\n      \"method\": \"X-ray crystallography using hybrid LRR technique, binding and cellular assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure with binding validation and mechanistic comparison to related receptors\",\n      \"pmids\": [\"25480784\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Crystal structure of LGR5 complexed with Rspo2 (at high resolution) shows engagement almost identical to RSPO1; LGR5 ectodomain exhibits nearly 9° plasticity in horseshoe fold; low-resolution ternary LGR5-Rspo2-ZNRF3 structure confirms Rspo proteins cross-link LGRs and ZNRF3 into a 2:2:2 complex with ZNRF3, whereas a 1:1:1 complex is formed with RNF43.\",\n      \"method\": \"X-ray crystallography of binary and ternary complexes\",\n      \"journal\": \"Journal of structural biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structures of binary and ternary complexes establishing stoichiometry difference between ZNRF3 and RNF43 complexes\",\n      \"pmids\": [\"26123262\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Signaling potency of RSPOs is determined by ternary complex formation ability (dependent on combined LGR4 and ZNRF3 binding); efficacy depends on ZNRF3 recruitment; RSPO2/3/4 have stronger signaling potencies than RSPO1; engineering RSPO2 ZNRF3-binding region onto RSPO4's LGR4-binding region creates a 'Superspondin' with 10-fold enhanced potency; RSPO1 has the weakest ZNRF3 binding among the four members.\",\n      \"method\": \"Purified protein binding assays, chimeric protein engineering, cell-based signaling assays, mutagenesis\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with purified components, chimera engineering with defined functional outcomes, multiple orthogonal assays\",\n      \"pmids\": [\"25504990\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RSPO1 expression in Rspo1(-/-) nephron progenitors (cap mesenchymal cells) is required for mesenchyme-to-epithelial transition (MET) linked to Bmp7 expression, SMAD1/5 phosphorylation, and activation of Lef1, Fgf8, and Wnt4; RSPO1 and RSPO3 act redundantly to permit WNT/β-catenin signaling and nephron progenitor maintenance; surprisingly, full knockout of LGR4/5/6 only mildly affects progenitor numbers but does not interfere with MET, revealing LGR-independent functions for R-spondins.\",\n      \"method\": \"Tissue-specific conditional knockout (Rspo1/Rspo3 and Lgr4/5/6 in cap mesenchyme), phospho-SMAD analysis, gene expression analysis\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple conditional knockouts with detailed molecular pathway analysis, LGR-independent mechanism revealed by genetic dissection\",\n      \"pmids\": [\"32324134\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RSPO1 inhibits beige adipocyte thermogenesis via LGR4-Wnt/β-catenin signaling; humanized knockin mice with RSPO1 p.R219W mutation show suppressed thermogenesis and obesity; the R219W mutation disrupts RSPO1's electrostatic interaction with the extracellular matrix, causing excessive RSPO1 release that hyperactivates LGR4-Wnt/β-catenin and attenuates mitochondrial respiration and thermogenic capacity in beige adipocytes.\",\n      \"method\": \"Whole-exome sequencing, knockin mouse model, adipose-specific overexpression, Rspo1 ablation, mechanistic RSPO1 administration to differentiated adipocytes\",\n      \"journal\": \"Advanced science (Weinheim, Baden-Wurttemberg, Germany)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — humanized knockin plus multiple mechanistic approaches in single study, but some aspects rely on overexpression/administration rather than endogenous manipulation\",\n      \"pmids\": [\"36755192\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In response to hormonal signaling, Amphiregulin (Areg) secreted by ER-positive luminal mammary cells induces RSPO1 expression in ER-negative luminal cells in a paracrine, EGFR-dependent manner, establishing an Estrogen-Areg-Rspo1 regulatory axis controlling RSPO1 expression in the mammary gland.\",\n      \"method\": \"Conditional cell-type specific analysis, paracrine co-culture experiments, EGFR inhibition, expression analysis\",\n      \"journal\": \"Developmental biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — paracrine mechanism established with pharmacological and genetic tools but single lab\",\n      \"pmids\": [\"31610144\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"RSPO1 is required for hematopoietic stem cell (HSC) specification in zebrafish through control of two parallel signaling pathways: Wnt16/DeltaC/DeltaD and Vegfa/Tgfβ1; Rspo1 acts upstream of both pathways to coordinate HSC specification with vessel patterning.\",\n      \"method\": \"Zebrafish genetic analysis, epistasis experiments with Wnt16 and Vegfa pathways\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis in zebrafish defining upstream pathway position, single lab\",\n      \"pmids\": [\"28087636\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"RSPO1 injection into the third brain ventricle of male rats inhibits food intake and decreases neuropeptide Y while increasing proopiomelanocortin expression in the arcuate nucleus; LGR4 (RSPO1 receptor) is expressed in arcuate, ventromedial, and median eminence hypothalamic nuclei colocalizing with NPY, POMC and BDNF neurons; Rspo1 is expressed by neurons and is down-regulated by fasting.\",\n      \"method\": \"In situ hybridization, intracerebroventricular injection, food intake measurement, gene expression analysis\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — direct localization and functional injection experiments, multiple readouts, single lab\",\n      \"pmids\": [\"24280058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Bispecific ROTACs (signaling-disabled RSPO chimeras) leverage RSPO specificity for ZNRF3/RNF43 E3 ubiquitin ligases to target degradation of transmembrane proteins; a bispecific RSPO2 chimera (R2PD1) targeting PD-L1 induces lysosomal degradation of PD-L1 strictly dependent on ZNRF3/RNF43, confirming RSPO's mechanistic role in directing ZNRF3/RNF43-mediated lysosomal degradation.\",\n      \"method\": \"Bispecific protein engineering, PD-L1 degradation assay, ZNRF3/RNF43 dependency assay, T cell reactivation assay\",\n      \"journal\": \"Cell chemical biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proof-of-concept reconstitution demonstrating ZNRF3/RNF43-dependent mechanism, single lab\",\n      \"pmids\": [\"37321224\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"R-spondin (RSPO1) encodes a secreted protein with a thrombospondin type 1 motif expressed in the dorsal neural tube; transfection of epitope-tagged R-spondin into COS7 and 293 cells shows both nuclear and secreted localization, suggesting processing-dependent localization; its expression is reduced in Wnt-1/3a double-knockout mice, placing it downstream of Wnt-1/3a signaling.\",\n      \"method\": \"Northern blot, in situ hybridization, epitope-tag transfection/fractionation, Wnt-1/3a double knockout expression analysis\",\n      \"journal\": \"Biochimica et biophysica acta\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — initial characterization with single subcellular localization experiment and one genetic association, foundational but limited mechanistic depth\",\n      \"pmids\": [\"14732490\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"RSPO1 augments β-catenin signaling in a dose-dependent manner; co-transfection of RSPO1 with CTNNB1 (β-catenin) results in ~10-fold synergistic activation of a TOPFLASH reporter; wild-type RSPO1 shows strong nuclear localization in several cell lines; an individual with a RSPO1 splice mutation shows reduced β-catenin protein and WNT4 mRNA in ovotestis tissue.\",\n      \"method\": \"TOPFLASH reporter transfection assay, subcellular localization (nuclear staining), patient tissue analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — reporter assay and localization without mechanistic follow-up; nuclear localization finding is potentially important but not mechanistically resolved\",\n      \"pmids\": [\"21297984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"RSPO1 overexpression in ApcMin/+ mice increases apoptosis and reduces Wnt signaling and proliferation in adenomas; this effect is mediated in part through activation of TGFβ/SMAD2 signaling, as TGFBR inhibition restores organoid formation and Wnt target gene expression suppressed by RSPO1; RSPO1 thus activates a cross-talk between Wnt and TGFβ pathways in adenoma cells.\",\n      \"method\": \"AAV-RSPO1-Fc delivery to ApcMin/+ mice, organoid culture with RSPO1 and TGFBR inhibitor, scRNA-seq, immunohistochemistry, phospho-SMAD2 analysis\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro evidence for RSPO1-TGFβ pathway cross-talk, multiple readouts, single lab\",\n      \"pmids\": [\"32941878\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Rspo1/Rspo3-LGR4 signaling in hepatocytes inhibits cholesterol synthesis via the AMPKα-SREBP2 pathway; Rspo1 increases phosphorylation of AMPKα Thr172, reducing SREBP2 nuclear translocation; hepatic LGR4 knockdown increases cholesterol synthesis and decreases AMPKα phosphorylation; AMPKα knockdown abrogates Rspo1-induced inhibition of cholesterol synthesis.\",\n      \"method\": \"LGR4/Rspo1/Rspo3 knockdown mice, AMPKα agonist/antagonist/shRNA epistasis, SREBP2 nuclear translocation assay, phospho-AMPKα analysis\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis experiments linking LGR4 to AMPKα-SREBP2, multiple genetic tools, single lab\",\n      \"pmids\": [\"32926477\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"LGR4 and LGR5 form distinct homodimers; only LGR4 (not LGR5) complexes with RNF43/ZNRF3 to provide high-affinity bivalent binding of RSPO ligands; co-expression of ZNRF3 with LGR4 greatly increases binding affinity for monovalent RSPO2 furin domain, whereas co-expression with LGR5 has no effect, establishing distinct receptor complex architectures that explain differential RSPO signaling through LGR4 vs LGR5.\",\n      \"method\": \"Binding affinity assays with monovalent and bivalent RSPO in whole cells, co-expression experiments, structural modeling\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — quantitative binding in cellular context with mechanistic interpretation, single lab\",\n      \"pmids\": [\"37402772\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"RSPO1 is a secreted glycoprotein that potentiates canonical Wnt/β-catenin signaling by bridging LGR4/5/6 (engagement receptors) with the transmembrane E3 ubiquitin ligases ZNRF3/RNF43 (effector receptors) through its furin-like (Fu1/Fu2) domains, forming a ternary complex that clears ZNRF3/RNF43 from the cell surface and thereby protects Frizzled/LRP Wnt receptor complexes from ubiquitin-mediated degradation; structural studies define the binding interfaces, and RSPO1's signaling potency is weaker than RSPO2/3 due to its lower affinity for ZNRF3; in vivo, RSPO1 is essential for ovarian differentiation (via β-catenin activation opposing Sox9/testis fate), germ cell meiosis, nephron progenitor maintenance, hematopoietic stem cell specification, and intestinal stem cell self-renewal, where it cooperates non-interchangeably with Wnt ligands.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"RSPO1 is a secreted glycoprotein that amplifies canonical Wnt/\\u03b2-catenin signaling by acting as a molecular bridge between two receptor classes, and through this activity governs gonadal sex determination, stem cell maintenance, and tissue morphogenesis [#1, #2, #9]. Its tandem furin-like cysteine-rich domains carry out distinct binding functions: Fu2 engages the concave leucine-rich-repeat surface of the LGR4/5/6 receptors, while Fu1 clamps into equivalent grooves on the transmembrane E3 ubiquitin ligases ZNRF3/RNF43, and both interfaces are required to assemble a ternary complex, clear ZNRF3/RNF43 from the cell surface, and activate signaling [#3, #4, #7, #16]. Within this architecture LGR4/5/6 serve as engagement receptors that increase RSPO1 affinity for the effector receptors ZNRF3/RNF43, and RSPO1's comparatively weak ZNRF3 binding makes it the least potent family member [#3, #12, #18]; this ZNRF3/RNF43-directed lysosomal degradation activity is sufficiently modular that signaling-disabled RSPO chimeras can be repurposed to degrade unrelated transmembrane targets [#24]. RSPO1 requires Wnt ligands and LRP6 for Wnt amplification and provides a self-renewal signal non-interchangeable with that of Wnt in Lgr5+ intestinal stem cells [#9, #13]. In vivo, RSPO1 is an essential driver of XX ovarian differentiation, activating \\u03b2-catenin and Wnt4 to oppose testis fate and to promote germ cell entry into meiosis, and it cooperates with WNT4 in gonadal progenitor proliferation [#2, #10, #11]. RSPO1 additionally supports developmental angiogenesis and hematopoietic stem cell specification, and it operates partly through LGR-independent and TGF\\u03b2/SMAD cross-talk routes in nephron progenitor maintenance and intestinal adenomas [#14, #22, #19, #27].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established RSPO1 as a secreted Wnt-responsive protein, placing it within the Wnt circuitry before its receptor mechanism was known.\",\n      \"evidence\": \"Expression analysis and epitope-tag fractionation in cell lines and Wnt-1/3a double-knockout mice\",\n      \"pmids\": [\"14732490\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Single localization experiment with ambiguous nuclear/secreted partition\", \"No receptor or biochemical mechanism defined\", \"Functional role inferred only from expression dependence\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Defined the minimal signaling unit and an early mechanistic model, showing the furin domains are sufficient and essential for Wnt amplification across all four family members.\",\n      \"evidence\": \"Domain deletion analysis and TOPFLASH/DKK1 antagonism assays for all R-spondins\",\n      \"pmids\": [\"18400942\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"DKK1-inhibition model later superseded by the LGR/ZNRF3 receptor mechanism\", \"Did not identify the engagement receptor\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrated the central in vivo role of RSPO1 in female sex determination, linking it to \\u03b2-catenin/Wnt4 activation opposing testis fate.\",\n      \"evidence\": \"Rspo1 knockout mouse with gonadal histology and Wnt4 expression analysis\",\n      \"pmids\": [\"18250098\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor mediating the gonadal effect not identified at this stage\", \"Cell-autonomy within germ vs somatic cells not resolved here\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identified LGR4/5/6 as the facultative Wnt-receptor components required for RSPO signaling, resolving how RSPO is sensed at the membrane.\",\n      \"evidence\": \"Mass spectrometry of receptor complexes, conditional deletion and rescue in mouse gut and HEK293, organoid culture; binding and clathrin-dependence assays in cells and Xenopus\",\n      \"pmids\": [\"21727895\", \"21909076\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Effector that translates LGR engagement into Wnt potentiation not yet defined\", \"Did not explain differential potency among RSPO family members\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Placed \\u03b2-catenin signaling cell-autonomously within germ cells, refining the gonadal model to show RSPO1 promotes oogonial differentiation and meiotic entry.\",\n      \"evidence\": \"Rspo1-/- XX gonad analysis with Stra8 and meiosis markers and epistasis to somatic differentiation\",\n      \"pmids\": [\"21991325\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct germ-cell receptor not identified\", \"Quantitative contribution of germ vs somatic signaling unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Independently confirmed LGR4 as a specific, G-protein-independent RSPO receptor via unbiased screening.\",\n      \"evidence\": \"siRNA screen, binding, overexpression, reporter, and G-protein coupling assays\",\n      \"pmids\": [\"22815884\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism downstream of LGR4 binding still unexplained\", \"Effector receptor not yet incorporated\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Revealed cooperative, sex-independent function of RSPO1 with WNT4 in gonadal progenitor proliferation, exposed only by combined loss.\",\n      \"evidence\": \"Wnt4-/-;Rspo1-/- double knockout with proliferation and histology\",\n      \"pmids\": [\"23095882\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of WNT4/RSPO1 cooperativity not dissected\", \"Receptor usage in progenitors not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Established the two-receptor mechanism structurally and functionally: RSPO1 bridges LGR (engagement) and ZNRF3/RNF43 (effector) E3 ligases through distinct Fu2 and Fu1 interfaces, clearing the ligases to protect Wnt receptors.\",\n      \"evidence\": \"Multiple crystal structures of binary and ternary complexes plus mutagenesis, biophysics, membrane-clearance and reporter assays\",\n      \"pmids\": [\"23756651\", \"24225776\", \"23809763\", \"23756652\", \"24165923\", \"24349440\", \"24050775\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometric differences between ZNRF3 and RNF43 complexes not yet resolved\", \"Family-wide potency determinants only partially quantified\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined potency determinants quantitatively, showing signaling strength scales with ternary-complex formation and that RSPO1 has the weakest ZNRF3 binding of the family.\",\n      \"evidence\": \"Purified-protein binding, chimera ('Superspondin') engineering, and cell signaling assays; LGR4 single-site structure\",\n      \"pmids\": [\"25504990\", \"25480784\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why RSPO1 evolved lower ZNRF3 affinity not addressed\", \"In vivo consequence of potency differences not tested here\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Resolved complex stoichiometry, showing RSPO cross-links LGR and ZNRF3 into a 2:2:2 assembly versus 1:1:1 with RNF43.\",\n      \"evidence\": \"Crystal structures of binary and ternary LGR5-Rspo-ZNRF3/RNF43 complexes\",\n      \"pmids\": [\"26123262\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of distinct ZNRF3 vs RNF43 stoichiometry not fully defined\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Distinguished RSPO and Wnt ligand functions, showing they are non-interchangeable in Lgr5+ intestinal stem cell self-renewal.\",\n      \"evidence\": \"In vivo ISC fate analysis with RSPO and non-lipidated Wnt analogue and organoid culture\",\n      \"pmids\": [\"28467820\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of qualitative difference between RSPO and Wnt inputs not resolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Extended RSPO1 function to hematopoietic stem cell specification and angiogenesis, placing it upstream of parallel Wnt/Notch and Vegf signaling.\",\n      \"evidence\": \"Zebrafish genetics and epistasis with Wnt16/DeltaC/DeltaD, Vegfa/Tgf\\u03b21 and Vegfc/Vegfr3\",\n      \"pmids\": [\"28087636\", \"22007135\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Receptor mediating these effects not defined in zebrafish\", \"Conservation of HSC role in mammals not established here\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Uncovered LGR-independent and TGF\\u03b2-crosstalk functions, showing RSPO1 maintains nephron progenitors and restrains adenoma growth through non-canonical routes.\",\n      \"evidence\": \"Conditional Rspo1/Rspo3 and Lgr4/5/6 knockouts with phospho-SMAD analysis; AAV-RSPO1 delivery to ApcMin/+ mice with organoid TGFBR inhibition\",\n      \"pmids\": [\"32324134\", \"32941878\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor mediating LGR-independent activity unidentified\", \"Direct link between RSPO1 and SMAD signaling not biochemically defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Demonstrated the modularity and physiological breadth of RSPO1's ZNRF3/RNF43-directed degradation activity, from engineered target degradation to metabolic regulation.\",\n      \"evidence\": \"Bispecific ROTAC PD-L1 degradation with ZNRF3/RNF43 dependency; humanized R219W knockin obesity model; AMPK\\u03b1-SREBP2 epistasis in hepatocytes; cellular LGR4 vs LGR5 complex-architecture binding\",\n      \"pmids\": [\"37321224\", \"36755192\", \"32926477\", \"37402772\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Several metabolic findings rely on overexpression/administration rather than endogenous manipulation\", \"Single-lab observations awaiting independent confirmation\", \"Mechanistic link between LGR4 engagement and AMPK\\u03b1 not biochemically resolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The identity of the receptor(s) mediating RSPO1's LGR-independent and TGF\\u03b2/SMAD-coupled functions, and the basis of the reported nuclear localization, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No receptor identified for LGR-independent activity\", \"Nuclear localization role and processing not mechanistically resolved\", \"Crosstalk to TGF\\u03b2/AMPK pathways lacks a defined biochemical intermediary\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [1, 7, 9, 18]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 7, 24]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [25]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 8, 9]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [2, 11, 14, 22]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [2, 10]}\n    ],\n    \"complexes\": [\n      \"RSPO1\\u2013LGR4/5/6\\u2013ZNRF3/RNF43 ternary complex\"\n    ],\n    \"partners\": [\n      \"LGR4\",\n      \"LGR5\",\n      \"LGR6\",\n      \"ZNRF3\",\n      \"RNF43\",\n      \"LRP6\",\n      \"WNT4\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}