{"gene":"LNX1","run_date":"2026-04-28T18:30:27","timeline":{"discoveries":[{"year":1998,"finding":"LNX was identified as a novel Numb PTB domain-interacting protein via yeast two-hybrid screen. The interaction is mediated by the sequence motif LDNPAY in LNX, which binds the Numb PTB domain independent of tyrosine phosphorylation. LNX contains a RING finger domain and four PDZ domains. Tyrosine phosphorylation of the LDNPAY motif can generate a binding site for other PTB domain-containing proteins such as SHC.","method":"Yeast two-hybrid screen, mutational analysis, peptide competition experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal binding assays with mutagenesis, foundational discovery paper with 108 citations","pmids":["9535908"],"is_preprint":false},{"year":2001,"finding":"LNX2 (and the related LNX1) bind to mammalian Numb and Numblike via NPXY motifs. LNX proteins form oligomers through PDZ domain interactions with PDZ-binding motifs in their C-termini and via homophilic RING finger oligomerization, suggesting they serve as molecular scaffolds that localize Numb to specific subcellular sites.","method":"Protein interaction assays, in situ hybridization, oligomerization studies","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 3 — binding assays without full mechanistic follow-up, single study","pmids":["11922143"],"is_preprint":false},{"year":2001,"finding":"Human LNX was cloned and shown to contain four PDZ domains and an NPXY motif for Numb PTB domain binding, mapping to chromosome 4q12.","method":"cDNA cloning, sequence analysis, radiation hybrid mapping","journal":"Biochemical genetics","confidence":"Low","confidence_rationale":"Tier 4 — cloning and sequence characterization, no functional assay","pmids":["11521506"],"is_preprint":false},{"year":2002,"finding":"LNX functions as a RING-type E3 ubiquitin ligase that targets Numb for ubiquitin-dependent proteasomal degradation. The isolated RING finger domain acts as an E2-dependent E3 ligase in vitro; mutation of a conserved RING cysteine abolishes activity. A region including the Numb PTB domain-binding site and the first PDZ domain is required for Numb ubiquitylation. Wild-type but not mutant LNX causes proteasome-dependent Numb degradation and enhances Notch signaling.","method":"In vitro ubiquitin ligase assay, site-directed mutagenesis, in vivo ubiquitination, proteasome inhibition, Notch signaling reporter assay","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 1 — in vitro reconstitution with mutagenesis plus in vivo validation; 156 citations, foundational paper","pmids":["11782429"],"is_preprint":false},{"year":2002,"finding":"LNX (LNX1) interacts with the Coxsackievirus and adenovirus receptor (CAR) intracellular tail via the second PDZ domain of LNX. Efficient CAR binding requires both the consensus PDZ-binding motif at the CAR C-terminus and upstream sequences. CAR and LNX colocalize in mammalian cells.","method":"Yeast two-hybrid screen, in vitro binding, co-immunoprecipitation, colocalization imaging","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — reciprocal Co-IP and in vitro binding confirming yeast two-hybrid result","pmids":["12468544"],"is_preprint":false},{"year":2004,"finding":"The Np9 protein of human endogenous retrovirus K interacts with LNX (E3 ubiquitin ligase), involving N- and C-terminal domains of both proteins. This interaction alters subcellular localization of LNX. Np9 is itself unstable and degraded via the proteasome; ectopic Numb stabilizes Np9, suggesting Np9 may affect tumorigenesis through the LNX/Numb/Notch pathway.","method":"Yeast two-hybrid, co-immunoprecipitation, proteasome inhibition assay, subcellular localization","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP with localization data, single study","pmids":["15367597"],"is_preprint":false},{"year":2005,"finding":"LNX1 is specifically expressed in perisynaptic Schwann cells (but not myelinating Schwann cells) at the neuromuscular junction and directly interacts with ErbB2. LNX1 protein levels are inversely correlated with responsiveness of perisynaptic Schwann cells to neuregulin-1, and LNX1 staining disappears upon denervation while ErbB2 reappears, suggesting LNX1 regulates neuregulin-1/ErbB signaling by promoting ErbB2 degradation.","method":"Immunostaining, direct protein interaction assay, developmental expression profiling, denervation model","journal":"Molecular and cellular neurosciences","confidence":"Medium","confidence_rationale":"Tier 2 — direct interaction identified with localization and developmental correlation, single lab","pmids":["16122940"],"is_preprint":false},{"year":2005,"finding":"Human LNX interacts with SKIP (Ski interacting protein) via its PDZ domains. Co-immunoprecipitation confirmed LNX-SKIP interaction in HEK293 cells. LNX affects subcellular localization of Numb, suggesting LNX functions as a molecular anchor localizing Numb to the subcellular site of its interaction with Notch.","method":"Yeast two-hybrid, co-immunoprecipitation, subcellular localization assay","journal":"The international journal of biochemistry & cell biology","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP confirmed Y2H interaction with localization data, single lab","pmids":["16002321"],"is_preprint":false},{"year":2009,"finding":"Lnx-like (Lnx-l, ortholog of LNX1 in zebrafish) functions as a critical regulator of dorso-ventral axis formation. Lnx-l was identified as an E3 ubiquitin ligase for Bozozok (Boz), a homeodomain transcriptional repressor. Lnx-l induces K48-linked polyubiquitylation of Boz leading to proteasomal degradation. Dorsalization by Boz overexpression is suppressed by Lnx-l; Lnx-l cannot counteract Boz lacking the Lnx-l binding motif. Depletion of Lnx-l causes embryonic dorsalization rescued by Boz attenuation.","method":"Antisense morpholino knockdown, K48-polyubiquitylation assay, genetic epistasis in zebrafish, domain mapping","journal":"Nature cell biology","confidence":"High","confidence_rationale":"Tier 1-2 — in vivo ubiquitination with K48-linkage specificity, genetic epistasis across multiple manipulations; 24 citations in Nature Cell Biology","pmids":["19668196"],"is_preprint":false},{"year":2009,"finding":"LNX interacts with RhoC via its first PDZ domain, as identified by yeast two-hybrid and confirmed by co-immunoprecipitation in mammalian cells. Co-expression of LNX causes RhoC to relocalize from cytoplasm to nucleus. Co-expression of RhoC reduces LNX-induced AP-1 transcriptional activity, suggesting LNX and RhoC form a complex that modulates AP-1-mediated transcription.","method":"Yeast two-hybrid, co-immunoprecipitation, subcellular localization, AP-1 transcriptional reporter assay","journal":"Molecular biology reports","confidence":"Medium","confidence_rationale":"Tier 3 — Co-IP with localization and functional reporter assay, single lab","pmids":["19701800"],"is_preprint":false},{"year":2010,"finding":"Lnx-2b (zebrafish LNX ortholog) restricts gsc expression to the dorsal mesoderm by limiting Nodal and Bozozok activity. Overexpression of Boz together with depletion of Lnx-2b (but not either alone) causes robust gsc expression in all blastomeres, demonstrating that maternally deposited Lnx-2b restricts organizer expansion through ubiquitin-mediated control of Boz.","method":"Morpholino knockdown, single-cell injection, epistasis analysis in zebrafish","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in vivo with targeted injections, single lab","pmids":["20971071"],"is_preprint":false},{"year":2010,"finding":"Knockdown of LNX by siRNA in HEK293 cells causes G0/G1 cell cycle arrest. Transcriptomic analysis revealed downregulation of β-catenin, MAPK, NFκB, c-Myc-dependent pathways and upregulation of p53 and TGF-β-dependent pathways, suggesting LNX participates in cell cycle regulation through multiple signaling cascades.","method":"siRNA knockdown, flow cytometry cell cycle analysis, expression microarray, qRT-PCR","journal":"Molecular biology reports","confidence":"Low","confidence_rationale":"Tier 3 — KD with phenotype but pathway placement is correlative/transcriptomic","pmids":["21104141"],"is_preprint":false},{"year":2011,"finding":"Human protein array screening of 8,000 proteins with isolated LNX1 PDZ domains identified 53 potential binding partners. Integration with other methods assembled 220 LNX1 interacting proteins. Six novel LNX1 binding partners were confirmed: KCNA4, PAK6, PLEKHG5, PKC-alpha1, TYK2, and PBK. LNX1 is proposed to function as a signalling scaffold.","method":"Human protein array, co-immunoprecipitation, bioinformatic analysis","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2-3 — proteome-scale screen with selected Co-IP validation, single lab","pmids":["22087225"],"is_preprint":false},{"year":2011,"finding":"Phylogenetic analysis revealed that LNX PDZ domains are closely related to the four C-terminal PDZ domains of MUPP1. Novel interactions of LNX1 and LNX2 with three known MUPP1 ligands were identified by yeast two-hybrid assays, demonstrating conservation of binding specificity between LNX and MUPP1 PDZ domains.","method":"Phylogenetic analysis, yeast two-hybrid interaction assays","journal":"BMC evolutionary biology","confidence":"Low","confidence_rationale":"Tier 3 — Y2H interactions only, evolutionary inference","pmids":["21827680"],"is_preprint":false},{"year":2012,"finding":"A proteomic strategy integrating peptide library screening and in vitro ubiquitination assays identified multiple LNX substrates. The substrate recognition mechanism involves LNX PDZ domains binding C-termini of target proteins. Two novel endogenous substrates, PBK and BCR, were confirmed in vivo. LNX1-mediated ubiquitination and degradation of PBK inhibits cell proliferation and enhances sensitivity to doxorubicin-induced apoptosis.","method":"Random peptide library yeast two-hybrid, in vitro ubiquitination assay, in vivo ubiquitination, cell proliferation assay, apoptosis assay","journal":"Journal of proteome research","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro ubiquitination reconstitution with in vivo validation and functional cellular phenotype; multiple orthogonal methods","pmids":["22889411"],"is_preprint":false},{"year":2014,"finding":"LNX1 protein expression in brain was demonstrated for the first time. Cell-type-specific expression of LNX isoforms was clarified in CNS and PNS. The 5' UTR of Lnx1_variant 2 mRNA (generating LNX1p70) strongly suppresses protein production via upstream open reading frames (uORFs) and a sequence element that decreases mRNA levels and translational efficiency. LNX1p80 protein levels are regulated by proteasomal degradation. These mechanisms explain the very low levels of LNX1 in vivo.","method":"Western blot, luciferase reporter assays, uORF analysis, proteasome inhibition","journal":"Gene","confidence":"Medium","confidence_rationale":"Tier 2 — reporter assays with mutagenesis of regulatory elements, single lab","pmids":["25200495"],"is_preprint":false},{"year":2016,"finding":"Mice lacking both LNX1 (in CNS) and LNX2 (globally) are healthy with unaltered Numb protein levels and no neuroanatomical defects indicative of NUMB dysfunction, demonstrating that LNX1/LNX2 are not essential for NUMB regulation in vivo. Double knockout mice exhibit decreased anxiety-related behaviour. Proteomic analysis identified LNX1/LNX2 interactions with presynaptic active zone proteins ERC1, ERC2, LIPRIN-αs (PPFIA1, PPFIA3), and F-BAR domain proteins FCHSD2 and SRGAP2.","method":"LNX1/LNX2 double knockout mouse, behavioural testing (open field, elevated plus maze), proteomics/mass spectrometry","journal":"Molecular neurobiology","confidence":"High","confidence_rationale":"Tier 2 — clean genetic KO with defined behavioral phenotype and proteomic interactome characterization","pmids":["27889896"],"is_preprint":false},{"year":2017,"finding":"Proteomic analysis of the LNX1 interactome by affinity purification/mass spectrometry identified many novel LNX1-interacting proteins, with many mapping to PDZ2 and showing specificity for LNX1 over LNX2. PPFIA1 (liprin-α1), KLHL11, KIF7, and ERC2 are ubiquitination substrates of LNX1. LNX1 ubiquitination of liprin-α1 requires a PDZ-binding motif with a C-terminal cysteine binding LNX1 PDZ2. The neuronal LNX1p70 isoform (lacking the RING domain) can promote ubiquitination of PPFIA1 and KLHL11 by recruiting other E3 ligases (MID2/TRIM1, TRIM27) as a scaffold.","method":"Affinity purification/mass spectrometry, in vitro ubiquitination assay, co-immunoprecipitation, domain mapping","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1-2 — AP-MS interactome plus in vitro ubiquitination validation; multiple substrates confirmed, novel scaffold model for catalytic-dead isoform","pmids":["29121065"],"is_preprint":false},{"year":2018,"finding":"The crystal structure of the LNX1 ubiquitination domain (Zn-RING-Zn) in complex with Ubc13~Ubiquitin was determined. The RING domain is flanked by two zinc-finger motifs, both required for ubiquitination activity. In the heterodimeric complex, ubiquitin from one monomer shares more buried surface area with LNX1 from the other monomer—a unique and essential feature for catalysis. Ubc13/Ube2V2 was identified as a functional E2 for LNX1 in vitro. Dimeric LNX1 recruits ubiquitin-loaded Ubc13 for Ub transfer.","method":"Crystal structure determination, in vitro ubiquitination assay, mutagenesis","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 — crystal structure with functional validation and mutagenesis; mechanistic insight into dimeric catalysis","pmids":["29496391"],"is_preprint":false},{"year":2018,"finding":"LNX1 and LNX2 colocalize with connexin36 (Cx36)-containing gap junctions at electrical synapses in adult mouse brain. LNX1 and LNX2 directly interact with Cx36 via their second PDZ domain (confirmed by pull-down). Co-transfection of E3-ligase-competent LNX1/LNX2 with Cx36 leads to loss of Cx36-containing gap junctions between cells, whereas ligase-inactive isoforms do not, indicating LNX-mediated ubiquitination of Cx36 promotes its internalization at electrical synapses.","method":"Immunofluorescence colocalization, co-immunoprecipitation, PDZ pull-down, cotransfection with ligase-active vs. inactive isoforms, LNX null mice","journal":"The European journal of neuroscience","confidence":"High","confidence_rationale":"Tier 2 — reciprocal Co-IP, domain pull-down, functional loss-of-junction phenotype with ligase-dead controls, confirmed in KO mice","pmids":["30295974"],"is_preprint":false},{"year":2018,"finding":"Postsynaptic LNX1 in hippocampal CA3 neurons is essential for mossy fiber (MF) axon targeting during the postnatal period. Lnx1 deletion causes defective synaptic arrangement and aberrant presynaptic terminals. EphB1 and EphB2 receptors are novel LNX1-binding proteins forming a multiprotein complex stabilized on the CA3 membrane by LNX1, which prevents proteasomal degradation of EphB receptors. EphB1 and EphB2 independently transduce distinct signals controlling MF pruning and targeting. Constitutively active EphB2 kinase rescues MF terminal structure in Lnx1 mutant mice.","method":"Lnx1 knockout mice, MF axon tracing, co-immunoprecipitation, proteasome inhibition assay, constitutively active EphB2 rescue experiment","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined neuroanatomical phenotype, biochemical complex identification, and genetic rescue","pmids":["30185604"],"is_preprint":false},{"year":2019,"finding":"LNX1 is an E3 ubiquitin ligase for NEK6; miR-325-3p targets LNX1 mRNA, reducing LNX1 levels, and thereby prevents proteasomal degradation of NEK6 in macrophages infected with M. tuberculosis. Accumulation of NEK6 activates STAT3 signaling, inhibiting apoptosis and promoting intracellular bacterial survival.","method":"Cell and mouse models, miRNA overexpression/knockdown, LNX1 overexpression/knockdown, western blot for NEK6 protein levels, STAT3 signaling assay, bacterial survival assay","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2-3 — LNX1 identified as E3 for NEK6 with in vivo functional consequence, but detailed mechanistic reconstitution not provided","pmids":["32487755"],"is_preprint":false},{"year":2019,"finding":"LDOC1 forms a protein complex with phospho-JAK2 and LNX1, targeting pJAK2 for ubiquitin-dependent proteasomal degradation. LDOC1 acts as a bridge between pJAK2 and LNX1 E3 ubiquitin ligase; LDOC1 deficiency attenuates LNX1-pJAK2 interaction, reducing pJAK2 ubiquitination and activating STAT3 signaling.","method":"Co-immunoprecipitation, immunofluorescence confocal microscopy, ubiquitination assay, LDOC1 KD/OE in lung cancer cells","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2-3 — Co-IP complex identification with functional ubiquitination consequence, single lab","pmids":["30634502"],"is_preprint":false},{"year":2019,"finding":"E3 ubiquitin ligases LNX1 and LNX2 ubiquitinate the presynaptic glycine transporter GlyT2. The RING-finger domain of LNX1/2 ubiquitinates a cytoplasmic C-terminal lysine cluster in GlyT2 (K751, K773, K787, K791), regulating GlyT2 expression and transport activity. Genetic deletion of LNX2 in spinal cord neurons increases GlyT2 expression. LNX2 is required for PKC-mediated control of GlyT2 transport.","method":"Unbiased screening, in vitro ubiquitination assay, site-directed mutagenesis of GlyT2 lysines, LNX2 knockout neurons, transport activity assay","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro ubiquitination with lysine mutagenesis and KO neuron validation with functional transport readout","pmids":["31628376"],"is_preprint":false},{"year":2019,"finding":"A hippocampal Lnx1-NMDAR-EphB2 multiprotein complex is required for initial social memory in juvenile mice. Lnx1 deficiency causes NMDAR hypofunction with decreased GluN2B in the postsynaptic density, disruption of the Lnx1-NMDAR-EphB2 complex, impaired neuronal activity in CA3, and social memory deficits. Specific restoration of Lnx1 or EphB2 in CA3 rescues synaptic function and social memory.","method":"Lnx1 knockout mice, co-immunoprecipitation, PSD fractionation, stereotaxic viral rescue, electrophysiology, behavioral testing","journal":"Molecular psychiatry","confidence":"High","confidence_rationale":"Tier 2 — genetic KO with complex biochemistry, regional viral rescue, and electrophysiological validation","pmids":["31772302"],"is_preprint":false},{"year":2019,"finding":"LNX1 interacts with p53 and MDM2, and increases p53 ubiquitination in an MDM2-dependent manner, thereby decreasing p53 half-life and inhibiting p53-dependent transcription. LNX1 knockout (CRISPR) in p53 wild-type cancer cells increases p53 stability and activates p53 transcription. LNX1 is required for efficient tumor growth in cell culture and mouse xenograft models.","method":"CRISPR-Cas9 knockout, lentiviral overexpression, co-immunoprecipitation, ubiquitination assay, p53 half-life measurement, xenograft tumor model","journal":"FASEB journal","confidence":"High","confidence_rationale":"Tier 2 — CRISPR KO with reciprocal OE, biochemical complex, ubiquitination assay, and in vivo tumor model","pmids":["31533005"],"is_preprint":false},{"year":2019,"finding":"In zebrafish, glycine signaling suppresses lnx1 expression; reduced Lnx1 stabilizes Numb protein and reduces Notch activity (measured as her4.1 expression), promoting neural stem cell (NSC) differentiation. Lnx1 overexpression increases NSC proliferation and causes neural tube closure defects. Knockdown of lnx1 blocks these effects of glycine signaling, placing lnx1 in the glycine→Lnx1→Numb→Notch pathway controlling NSC proliferation.","method":"Zebrafish morpholino knockdown, lnx1 overexpression, Notch activity reporter, in situ hybridization, neural tube phenotype analysis","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in vivo with pathway reporter readout, single lab","pmids":["30833887"],"is_preprint":false},{"year":2020,"finding":"LNX1 upregulation after temozolomide (TMZ) therapy in glioblastoma leads to Numb degradation, activation of Notch1 (increased NICD), and expansion of glioma stem cell (GSC) populations. LNX1 overexpression activates Notch1 and increases GSC populations; LNX1 knockdown reduces NICD, decreases stemness after TMZ, and prolongs median survival in a mouse model. This places LNX1 as a regulator of chemotherapy-induced stemness via the Numb/Notch1 axis.","method":"GSEA on PDX cells, LNX1 OE/KD in PDX lines, Notch1 signaling measurement (NICD western), GSC population assay, mouse survival model","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2-3 — OE/KD with mechanistic pathway readout and in vivo survival endpoint, single lab","pmids":["33255632"],"is_preprint":false},{"year":2021,"finding":"LNX1 contributes to cell cycle progression; LNX1 knockout delays cell cycle, downregulates cyclin D1 and cyclin E1, and upregulated LNX1 increases S and G2/M populations. LNX1 upregulation activates cell cycle progression and increases resistance to cisplatin-mediated cell death.","method":"CRISPR-Cas9 KO, lentiviral overexpression, flow cytometry, western blot for cyclins","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 — clean CRISPR KO with reciprocal OE and specific molecular markers, single lab","pmids":["34439220"],"is_preprint":false},{"year":2022,"finding":"LNX1 performs non-degrading ubiquitination (NDU) of RhoC (but not RhoA), promoting RhoC activity. LIS1 (PAFAH1B1) negatively regulates LNX1-mediated ubiquitination of RhoC by inhibiting LNX1's effects on RhoGDI-RhoC interaction. This LIS1-LNX1-RhoC module represents an evolutionarily acquired function present only in vertebrates, providing a mechanism for isoform-specific Rho regulation.","method":"In vitro ubiquitination assay, RhoGDI interaction assay, LIS1 overexpression/knockdown, RhoC activity assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro biochemistry with isoform specificity and molecular mechanism, single lab","pmids":["36192543"],"is_preprint":false},{"year":2022,"finding":"HO-1 controls LNX1 expression in hepatic macrophages; LNX1 expression is strongly suppressed in HO-1-deficient macrophages. LNX1 drives M2-like macrophage polarization; Notch1 (downstream target of LNX1-mediated Numb degradation) is increased in HO-1-deficient macrophages. Transient LNX1 overexpression in HO-1-deficient macrophages treated with heme rescues M2-like polarization, defining a HO-1→LNX1→Notch1 pathway in macrophage polarization and liver fibrosis.","method":"RiboTag RNA-seq, LNX1 overexpression in HO-1-deficient macrophages, Notch1 western blot, macrophage polarization assay","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2-3 — pathway placement via gene expression and OE rescue, single lab","pmids":["36093061"],"is_preprint":false},{"year":2022,"finding":"Lnx1 stabilizes EphB receptors at the postsynaptic membrane by preventing their internalization. Loss of Lnx1 promotes EphB receptor internalization from the cell surface, leading to abnormal dendritic spine development and impaired synaptogenesis. Constitutively active EphB2 intracellular signaling rescues synaptogenesis in Lnx1 mutant mice.","method":"Lnx1 knockout mice, receptor internalization assay, dendritic spine morphology analysis, constitutively active EphB2 rescue","journal":"Frontiers in molecular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — KO with defined spine phenotype and molecular mechanism, confirmed by genetic rescue","pmids":["35531068"],"is_preprint":false},{"year":2025,"finding":"Neuronal LNX1 isoforms (LNX1p70, which lack the RING catalytic domain) act as stabilizing scaffolds for shared interaction partners, while LNX2 promotes their ubiquitination and degradation. Single and double LNX1/LNX2 knockout behavioral analysis shows LNX2 plays a more prominent role in altered dark-light emergence and risk-taking behavior, while LNX1 loss contributes to anxiety phenotypes and determines body weight. Lnx1 knockout affects ultrasonic vocalizations of pups, revealing a role in social communication.","method":"Single and double LNX1/LNX2 knockout mice, behavioral battery (open field, EPM, dark-light, marble burying, novel object recognition, ultrasonic vocalizations), body weight analysis","journal":"Behavioral and brain functions","confidence":"Medium","confidence_rationale":"Tier 2 — clean genetic KO with defined behavioral phenotypes, distinction between LNX1 scaffold vs. LNX2 E3 roles","pmids":["40269869"],"is_preprint":false}],"current_model":"LNX1 is a RING-type E3 ubiquitin ligase whose catalytic domain (embedded in a Zn-RING-Zn architecture that functions as a homodimer recruiting Ubc13/Ube2V2) is coupled to four PDZ domains that recruit substrates including Numb, ErbB2, NEK6, GlyT2, PBK, BCR, connexin36, liprin-α1, p53 (MDM2-dependently), and RhoC (non-degradatively); by ubiquitinating Numb for proteasomal degradation LNX1 activates Notch signaling, while its PDZ scaffold function stabilizes EphB receptors and NMDAR complexes at postsynaptic densities to regulate hippocampal synaptogenesis, mossy fiber targeting, and social memory, with the neuronal LNX1p70 isoform (which lacks the RING domain) acting as a non-catalytic scaffold that recruits other E3 ligases to ubiquitinate shared substrates."},"narrative":{"teleology":[{"year":1998,"claim":"The initial question was what proteins interact with the Numb PTB domain; yeast two-hybrid screening identified LNX as a novel RING-finger and PDZ-domain protein that binds Numb via an NPXY-like motif, establishing the founding interaction of the LNX field.","evidence":"Yeast two-hybrid with Numb PTB domain bait, mutational and peptide competition analyses in vitro","pmids":["9535908"],"confidence":"High","gaps":["No functional consequence of the Numb–LNX interaction was tested","Enzymatic activity of the RING domain was not assessed","In vivo relevance of the interaction was unknown"]},{"year":2002,"claim":"The critical question of whether the RING domain confers E3 ligase activity was answered: LNX ubiquitinates Numb in a RING-dependent manner, targets it for proteasomal degradation, and thereby activates Notch signaling, establishing LNX as a functional E3 ligase in the Numb/Notch pathway.","evidence":"In vitro reconstituted ubiquitin ligase assay, RING cysteine mutagenesis, proteasome inhibitor treatment, Notch reporter assay in mammalian cells","pmids":["11782429"],"confidence":"High","gaps":["The E2 partner(s) were not identified","In vivo physiological requirement for LNX-mediated Numb degradation was untested","Other substrates beyond Numb were unknown"]},{"year":2002,"claim":"The scope of LNX PDZ-domain interactions was broadened when LNX1 was shown to bind the Coxsackievirus and adenovirus receptor (CAR) via PDZ2, establishing the PDZ domains as versatile substrate-recruitment modules.","evidence":"Yeast two-hybrid, co-immunoprecipitation, and colocalization in mammalian cells","pmids":["12468544"],"confidence":"Medium","gaps":["Whether CAR is a ubiquitination substrate of LNX1 was not tested","Functional consequence for viral entry or cell adhesion was not determined"]},{"year":2005,"claim":"Cell-type-specific expression studies at the neuromuscular junction revealed LNX1 in perisynaptic Schwann cells and its interaction with ErbB2, suggesting a role in regulating neuregulin signaling at synapses and extending LNX1 biology beyond the Numb/Notch axis.","evidence":"Immunostaining of NMJ, direct protein interaction assay, denervation model correlation","pmids":["16122940"],"confidence":"Medium","gaps":["Direct ubiquitination of ErbB2 by LNX1 was not demonstrated","Functional rescue experiments were not performed","Mechanism of ErbB2 downregulation remained correlative"]},{"year":2009,"claim":"Zebrafish studies demonstrated an in vivo developmental requirement: LNX orthologs ubiquitinate the homeodomain protein Bozozok via K48-linked chains for proteasomal degradation, restricting dorsal organizer expansion and controlling dorsoventral axis formation.","evidence":"Morpholino knockdown, K48-polyubiquitination assay, genetic epistasis in zebrafish embryos","pmids":["19668196"],"confidence":"High","gaps":["Whether mammalian LNX1 has analogous developmental patterning roles was unknown","The identity of the E2 was not determined in vivo"]},{"year":2012,"claim":"A systematic substrate-discovery approach identified PBK and BCR as endogenous LNX1 substrates and showed that LNX1-mediated PBK degradation inhibits cell proliferation and sensitizes cells to apoptosis, expanding the substrate repertoire and linking LNX1 to cell cycle control.","evidence":"Random peptide library screen, in vitro ubiquitination, in vivo ubiquitination assay, proliferation and apoptosis assays","pmids":["22889411"],"confidence":"High","gaps":["Whether PBK/BCR are physiological substrates in normal tissues was not established","The PDZ domain specificity for each substrate was not fully mapped"]},{"year":2016,"claim":"The long-standing assumption that LNX1 is a major Numb regulator in vivo was overturned: LNX1/LNX2 double-knockout mice showed normal Numb levels and no neuroanatomical defects attributable to Numb dysfunction, but exhibited decreased anxiety behavior, redirecting attention toward synaptic scaffold functions.","evidence":"LNX1/LNX2 double-knockout mice, behavioral testing, proteomics identifying presynaptic active zone interactors (ERC1/2, liprin-αs, FCHSD2, SRGAP2)","pmids":["27889896"],"confidence":"High","gaps":["Compensatory mechanisms that maintain Numb levels were not identified","Tissue-specific Numb regulation (e.g., in specific developmental windows) was not ruled out"]},{"year":2017,"claim":"AP-MS interactomics and in vitro assays revealed liprin-α1, KLHL11, KIF7, and ERC2 as ubiquitination substrates and, critically, demonstrated that the RING-less LNX1p70 neuronal isoform acts as a non-catalytic scaffold that recruits TRIM-family E3 ligases (MID2/TRIM1, TRIM27) to ubiquitinate shared substrates.","evidence":"Affinity purification–mass spectrometry, in vitro ubiquitination with domain mapping, Co-IP for TRIM E3 recruitment","pmids":["29121065"],"confidence":"High","gaps":["Whether TRIM E3 recruitment by LNX1p70 occurs at synapses in vivo was not shown","Structural basis for the LNX1p70–TRIM interaction was not determined"]},{"year":2018,"claim":"Structural determination of the Zn-RING-Zn domain in complex with Ubc13~Ub resolved how LNX1 catalyzes ubiquitin transfer: the homodimeric architecture creates a unique trans-monomer ubiquitin-sharing surface essential for catalysis, identifying Ubc13/Ube2V2 as the functional E2.","evidence":"Crystal structure of LNX1 Zn-RING-Zn:Ubc13~Ub complex, mutagenesis, in vitro ubiquitination","pmids":["29496391"],"confidence":"High","gaps":["How dimerization is regulated in cells was not addressed","Chain-type specificity (K48 vs. K63) conferred by E2 choice was not fully resolved for all substrates"]},{"year":2018,"claim":"Two concurrent studies established LNX1 as a postsynaptic scaffold essential for hippocampal circuit wiring: LNX1 stabilizes EphB1/B2 receptors on the CA3 membrane, prevents their internalization, and organizes an NMDAR–EphB2 complex required for mossy fiber targeting and connexin36-based electrical synapses.","evidence":"Lnx1 knockout mice with mossy fiber tracing, Co-IP of EphB/NMDAR complexes, receptor internalization assays, connexin36 gap junction loss with ligase-active vs. inactive LNX","pmids":["30185604","30295974"],"confidence":"High","gaps":["Whether the scaffold and E3 functions operate simultaneously on the same complex was unclear","The triggering signals for LNX1-mediated Cx36 ubiquitination were not identified"]},{"year":2019,"claim":"The scaffold function was linked to behavior: Lnx1 deficiency disrupts the LNX1–NMDAR–EphB2 complex in hippocampal CA3, causing NMDAR hypofunction, impaired neuronal activity, and social memory deficits that are rescued by region-specific Lnx1 or EphB2 restoration.","evidence":"Lnx1 KO mice, PSD fractionation, stereotaxic viral rescue of CA3, electrophysiology, social recognition assay","pmids":["31772302"],"confidence":"High","gaps":["Whether human LNX1 variants associate with social cognition phenotypes was not tested","Contribution of LNX1p70 vs. LNX1p80 to the synaptic complex was not dissected"]},{"year":2019,"claim":"LNX1's substrate range was extended to tumor suppressor pathways: LNX1 interacts with p53 and MDM2, enhances MDM2-dependent p53 ubiquitination, and LNX1 knockout stabilizes p53, suppressing xenograft tumor growth.","evidence":"CRISPR-Cas9 KO and lentiviral OE in cancer cells, Co-IP, ubiquitination assay, p53 half-life measurement, mouse xenograft","pmids":["31533005"],"confidence":"High","gaps":["Whether LNX1 directly ubiquitinates p53 or only facilitates MDM2-dependent ubiquitination was not fully resolved","Physiological relevance outside cancer cell lines was not examined"]},{"year":2022,"claim":"A non-degradative ubiquitination function was defined: LNX1 performs non-degrading ubiquitination of RhoC (but not RhoA) to promote RhoC activity, with LIS1 acting as a negative regulator of this process, revealing isoform-specific Rho regulation.","evidence":"In vitro ubiquitination, RhoGDI interaction assay, RhoC activity assay, LIS1 OE/KD","pmids":["36192543"],"confidence":"Medium","gaps":["The ubiquitin chain type on RhoC was not identified","In vivo validation of the LIS1–LNX1–RhoC axis was not performed"]},{"year":2025,"claim":"Behavioral dissection of single and double LNX knockouts clarified isoform-specific roles: neuronal LNX1p70 functions as a stabilizing scaffold for shared partners while LNX2 promotes their degradation, and Lnx1 loss specifically affects anxiety behavior, body weight, and pup ultrasonic vocalizations.","evidence":"Single and double LNX1/LNX2 KO mice, comprehensive behavioral battery, body weight analysis","pmids":["40269869"],"confidence":"Medium","gaps":["Molecular substrates driving anxiety and vocalization phenotypes were not identified","Whether LNX1 scaffold and LNX2 E3 functions are competitive or complementary at the same synapse remains untested"]},{"year":null,"claim":"Major unresolved questions include how LNX1 E3 ligase and scaffold functions are coordinated at individual synapses, which substrates drive the behavioral phenotypes observed in knockout mice, and whether LNX1 variants contribute to human neurodevelopmental or psychiatric conditions.","evidence":"","pmids":[],"confidence":"Low","gaps":["No human genetic association studies for LNX1 have been reported","Chain-type specificity across different substrates is incompletely characterized","Structural basis of PDZ domain substrate selection is lacking"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[3,8,14,17,18,19,21,23,25,29]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[17,20,24,31,32]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[20,24,31]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[9,15]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[3,14,17,18,23,25,29]},{"term_id":"R-HSA-112316","term_label":"Neuronal System","supporting_discovery_ids":[19,20,24,31]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[8,10,26]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[14,28]}],"complexes":["LNX1-NMDAR-EphB2 postsynaptic complex"],"partners":["NUMB","EPHB2","EPHB1","PPFIA1","GJD2","UBE2N","ERBB2","MDM2"],"other_free_text":[]},"mechanistic_narrative":"LNX1 is a RING-type E3 ubiquitin-protein ligase that couples a Zn-RING-Zn catalytic domain—functioning as a homodimer that recruits Ubc13/Ube2V2—with four PDZ domains that select substrates and scaffold multiprotein complexes [PMID:29496391, PMID:11782429]. Through ubiquitin-dependent degradation of Numb, LNX1 activates Notch signaling to regulate neural stem cell proliferation, glioma stem cell expansion, and macrophage polarization [PMID:11782429, PMID:30833887, PMID:33255632, PMID:36093061]; additional substrates targeted for proteasomal degradation include PBK, BCR, NEK6, connexin36, and liprin-α1, while non-degradative ubiquitination of RhoC modulates Rho-GTPase activity [PMID:22889411, PMID:30295974, PMID:29121065, PMID:36192543]. In the hippocampus, LNX1 acts as a postsynaptic scaffold that stabilizes EphB receptors and an NMDAR–EphB2 complex at the membrane, and loss of Lnx1 causes defective mossy fiber targeting, impaired synaptogenesis, and social memory deficits, while the neuronal LNX1p70 isoform—lacking the RING domain—serves as a non-catalytic scaffold recruiting other TRIM-family E3 ligases to ubiquitinate shared partners [PMID:30185604, PMID:31772302, PMID:35531068, PMID:29121065]."},"prefetch_data":{"uniprot":{"accession":"Q8TBB1","full_name":"E3 ubiquitin-protein ligase LNX","aliases":["Ligand of Numb-protein X 1","Numb-binding protein 1","PDZ domain-containing RING finger protein 2","RING-type E3 ubiquitin transferase LNX"],"length_aa":728,"mass_kda":80.6,"function":"E3 ubiquitin-protein ligase that mediates ubiquitination and subsequent proteasomal degradation of NUMB. E3 ubiquitin ligases accept ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates. Mediates ubiquitination of isoform p66 and isoform p72 of NUMB, but not that of isoform p71 or isoform p65 Isoform 2 provides an endocytic scaffold for IGSF5/JAM4","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q8TBB1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/LNX1","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/LNX1","total_profiled":1310},"omim":[{"mim_id":"609733","title":"LIGAND OF NUMB PROTEIN X2; LNX2","url":"https://www.omim.org/entry/609733"},{"mim_id":"609732","title":"LIGAND OF NUMB PROTEIN X1; LNX1","url":"https://www.omim.org/entry/609732"},{"mim_id":"609730","title":"PDZ DOMAIN-CONTAINING RING FINGER PROTEIN 4; PDZRN4","url":"https://www.omim.org/entry/609730"},{"mim_id":"609729","title":"PDZ DOMAIN-CONTAINING RING FINGER PROTEIN 3; PDZRN3","url":"https://www.omim.org/entry/609729"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cell Junctions","reliability":"Supported"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/LNX1"},"hgnc":{"alias_symbol":["MPDZ","PDZRN2"],"prev_symbol":["LNX"]},"alphafold":{"accession":"Q8TBB1","domains":[{"cath_id":"3.30.40.10","chopping":"38-135","consensus_level":"medium","plddt":89.918,"start":38,"end":135},{"cath_id":"2.30.42.10","chopping":"379-463","consensus_level":"medium","plddt":83.6369,"start":379,"end":463},{"cath_id":"2.30.42.10","chopping":"503-594","consensus_level":"high","plddt":88.222,"start":503,"end":594},{"cath_id":"2.30.42.10","chopping":"630-728","consensus_level":"medium","plddt":87.4195,"start":630,"end":728}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TBB1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TBB1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8TBB1-F1-predicted_aligned_error_v6.png","plddt_mean":71.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=LNX1","jax_strain_url":"https://www.jax.org/strain/search?query=LNX1"},"sequence":{"accession":"Q8TBB1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8TBB1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8TBB1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8TBB1"}},"corpus_meta":[{"pmid":"11782429","id":"PMC_11782429","title":"LNX functions as a RING type E3 ubiquitin ligase that targets the cell fate determinant Numb for ubiquitin-dependent degradation.","date":"2002","source":"The EMBO journal","url":"https://pubmed.ncbi.nlm.nih.gov/11782429","citation_count":156,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"9535908","id":"PMC_9535908","title":"The mammalian numb phosphotyrosine-binding domain. 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Lnx-like.","date":"2009","source":"Nature cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/19668196","citation_count":24,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"34108620","id":"PMC_34108620","title":"MPDZ as a novel epigenetic silenced tumor suppressor inhibits growth and progression of lung cancer through the Hippo-YAP pathway.","date":"2021","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/34108620","citation_count":22,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"30634502","id":"PMC_30634502","title":"Novel STAT3 Inhibitor LDOC1 Targets Phospho-JAK2 for Degradation by Interacting with LNX1 and Regulates the Aggressiveness of Lung Cancer.","date":"2019","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/30634502","citation_count":22,"is_preprint":false,"source_track":"pubmed_title"},{"pmid":"22087225","id":"PMC_22087225","title":"Biochemical and computational analysis of LNX1 interacting proteins.","date":"2011","source":"PloS 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The Numb PTB domain-binding region of LNX1 was mapped to the sequence motif LDNPAY, and phosphorylation of the tyrosine within this motif was not required for binding. LNX1 contains a RING finger domain and four PDZ domains.\",\n      \"method\": \"Yeast two-hybrid screen, mutational analysis, peptide competition experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal binding confirmed with mapped motifs, replicated in subsequent work\",\n      \"pmids\": [\"9535908\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"LNX1 functions as a RING-type E3 ubiquitin ligase that targets Numb for ubiquitin-dependent proteasomal degradation. The isolated RING finger domain shows E2-dependent E3 ubiquitin ligase activity in vitro; mutation of a conserved cysteine in the RING domain abolishes activity. In addition to the RING finger, a region including the Numb PTB domain-binding site and first PDZ domain is required for Numb ubiquitylation. Expression of wild-type but not catalytically inactive LNX1 causes proteasome-dependent degradation of Numb and enhances Notch signalling.\",\n      \"method\": \"In vitro ubiquitination assay, active-site mutagenesis, in vivo degradation assay, Notch reporter assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro E3 activity with mutagenesis, confirmed in vivo, highly cited foundational paper\",\n      \"pmids\": [\"11782429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"LNX1 and LNX2 form oligomers via their PDZ domains binding to PDZ-binding consensus motifs in their C-termini and by homophilic oligomerization of their RING fingers. Oligomerization and Numb binding occur simultaneously, suggesting LNX proteins serve as molecular scaffolds localizing Numb to specific subcellular sites.\",\n      \"method\": \"Protein interaction assays, in situ hybridization\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, binding and oligomerization shown but limited orthogonal validation\",\n      \"pmids\": [\"11922143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"LNX1 binds to the intracellular tail of the Coxsackievirus and adenovirus receptor (CAR) both in vivo and in vitro. Efficient binding requires not only the consensus PDZ domain-binding motif at the C-terminus of CAR but also upstream sequences. The CAR-binding region in LNX1 was mapped to the second PDZ domain. LNX1 and CAR colocalize in mammalian cells.\",\n      \"method\": \"Yeast two-hybrid, in vitro binding assay, co-immunoprecipitation, immunofluorescence colocalization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, in vitro pull-down, colocalization, PDZ domain mapped\",\n      \"pmids\": [\"12468544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"LNX1 directly interacts with ErbB2 and is specifically localized in perisynaptic Schwann cells at the neuromuscular junction. LNX1 protein levels are inversely correlated with ErbB2 responsiveness to neuregulin-1, and LNX1 staining disappears upon denervation while ErbB2 reappears, suggesting LNX1 regulates neuregulin-1/ErbB signaling at perisynaptic Schwann cells.\",\n      \"method\": \"Immunostaining, co-immunoprecipitation, developmental expression analysis\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — direct interaction shown by Co-IP, localization established, functional link inferred\",\n      \"pmids\": [\"16122940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"LNX1 interacts with SKIP (Ski interacting protein) via its PDZ domains, as shown by yeast two-hybrid and co-immunoprecipitation in HEK293 cells. LNX1 can affect the subcellular localization of Numb, functioning as a molecular anchor that localizes Numb to the subcellular site of its interaction with Notch.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, subcellular localization assay\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, single Co-IP with limited mechanistic follow-up\",\n      \"pmids\": [\"16002321\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Zebrafish Lnx-like (Lnx-l/Lnx-2b), an ortholog of LNX1, ubiquitinates Bozozok (a homeodomain transcriptional repressor) via K48-linked polyubiquitylation, leading to its proteasomal degradation. This regulates dorso-ventral axis formation; depletion of Lnx-l causes embryonic dorsalization, and Lnx-l fails to suppress Boz-induced dorsalization when Boz lacks its critical Lnx-l binding motif.\",\n      \"method\": \"Morpholino knockdown, in vivo ubiquitination assay, epistasis by co-injection, dominant-negative Boz mutant\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vivo ubiquitination with K48-linkage specificity, epistasis, mutant substrate, replicated in zebrafish\",\n      \"pmids\": [\"19668196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"LNX1 interacts with RhoC via its first PDZ domain, as shown by yeast two-hybrid and co-immunoprecipitation. Co-expression of RhoC with LNX1 changes RhoC localization from cytoplasm to nucleus and reduces LNX1-upregulated AP-1 transcriptional activity.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, subcellular localization assay, AP-1 luciferase reporter\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, single Co-IP, PDZ domain mapped but mechanistic follow-up limited\",\n      \"pmids\": [\"19701800\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"LNX1 PDZ domains directly bind 53 human proteins identified by protein array screening. Six novel LNX1 binding partners were confirmed: KCNA4, PAK6, PLEKHG5, PKC-alpha1, TYK2, and PBK. LNX1 functions as a signalling scaffold through its PDZ domains.\",\n      \"method\": \"Human protein array screening with isolated PDZ domains, co-immunoprecipitation confirmation\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — large-scale direct binding screen confirmed by Co-IP for six partners\",\n      \"pmids\": [\"22087225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"LNX1 E3 ubiquitin ligase activity ubiquitinates PBK (PDZ-binding kinase) and BCR (breakpoint cluster region protein) as novel substrates in vivo, confirmed by in vitro ubiquitination. LNX1-mediated ubiquitination and degradation of PBK inhibits cell proliferation and enhances sensitivity to doxorubicin-induced apoptosis. Substrate recognition involves LNX1 PDZ domains binding C-terminal motifs of target proteins.\",\n      \"method\": \"Yeast two-hybrid peptide library screen, in vitro ubiquitination assay, endogenous substrate validation by Co-IP/degradation assay, cell proliferation/apoptosis assays\",\n      \"journal\": \"Journal of proteome research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro ubiquitination plus in vivo substrate confirmation with functional cellular readout\",\n      \"pmids\": [\"22889411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The crystal structure of the LNX1 ubiquitination domain in complex with Ubc13~Ubiquitin was determined. The RING domain is embedded between two zinc-finger motifs (Zn-RING-Zn), both crucial for ubiquitination activity. In the heterodimeric complex, ubiquitin from one monomer shares more buried surface area with LNX1 from the other monomer, revealing how dimeric LNX1 recruits ubiquitin-loaded Ubc13 for Ub transfer. Ubc13/Ube2V2 was identified as a functional E2 for LNX1 in vitro.\",\n      \"method\": \"Crystal structure determination, in vitro ubiquitination assay, mutagenesis\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional validation and mutagenesis\",\n      \"pmids\": [\"29496391\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"LNX1 and LNX2 colocalize with connexin36 (Cx36)-containing gap junctions at neuronal electrical synapses in adult mouse brain. LNX proteins directly interact with Cx36 via the second PDZ domain. Cotransfection of RING-competent LNX1/LNX2 with Cx36 leads to loss of Cx36-containing gap junctions, whereas RING-inactive isoforms do not, indicating LNX-mediated ubiquitination of Cx36 causes its internalization.\",\n      \"method\": \"Immunofluorescence colocalization, co-immunoprecipitation, GST pull-down with isolated PDZ domains, cotransfection with RING-active vs. RING-inactive isoforms, LNX null mouse controls\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, PDZ domain mapping, functional isoform comparison, null mouse controls\",\n      \"pmids\": [\"30295974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"LNX1 interacts with EphB receptors in hippocampal CA3 pyramidal neurons to form a multiprotein complex that stabilizes EphB receptors on the cell surface by preventing proteasome-mediated degradation. Lnx1 deletion causes defective mossy fiber axon targeting and aberrant presynaptic terminals. EphB1 and EphB2 are independently required for mossy fiber pruning and targeting, and constitutively active EphB2 kinase rescues the LNX1 mutant phenotype.\",\n      \"method\": \"Gene knockout mouse, co-immunoprecipitation, synaptic fractionation, morphological analysis, epistasis with constitutively active EphB2\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined synaptic phenotype, Co-IP, epistasis with constitutively active receptor\",\n      \"pmids\": [\"30185604\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LNX1 is an E3 ubiquitin ligase of NEK6; it targets NEK6 for proteasomal degradation. miR-325-3p directly targets LNX1 mRNA, reducing LNX1 levels, which causes NEK6 accumulation, leading to STAT3 activation and inhibition of apoptosis during Mycobacterium tuberculosis infection.\",\n      \"method\": \"miRNA target validation, co-immunoprecipitation, ubiquitination assay, luciferase reporter, mouse infection model\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP and degradation assay confirm LNX1 as E3 for NEK6, pathway supported by mouse model\",\n      \"pmids\": [\"32487755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LNX1 non-degrading ubiquitination (NDU) activates RhoC but not RhoA specifically. LIS1 (PAFAH1B1) negatively regulates LNX1-mediated ubiquitination of RhoC, and this LIS1 inhibition of LNX1 effects on RhoGDI-RhoC interaction provides a mechanism for enhanced Rho activity upon LIS1 reduction. LNX1 PDZ interaction with RhoC was mapped to the first PDZ domain.\",\n      \"method\": \"In vitro ubiquitination assay, co-immunoprecipitation, RhoGDI interaction assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro ubiquitination with isoform specificity, confirmed mechanism with LIS1 suppression\",\n      \"pmids\": [\"36192543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LDOC1 forms a multiprotein complex with phospho-JAK2 and LNX1 E3 ubiquitin ligase, targeting pJAK2 for ubiquitin-dependent proteasomal degradation. LDOC1 deficiency attenuates the LNX1-pJAK2 interaction, leading to ineffective pJAK2 ubiquitination and STAT3 activation.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescent confocal microscopy, ubiquitination assay, in vivo tumor model\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — Co-IP and ubiquitination assay in cell context, supported by in vivo model\",\n      \"pmids\": [\"30634502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LNX1 ubiquitinates PPFIA1 (liprin-α1), KLHL11, KIF7, and ERC2 as substrates. LNX1 ubiquitination of liprin-α1 depends on a PDZ-binding motif with a C-terminal cysteine that binds LNX1 PDZ2. The neuronal LNX1p70 isoform (lacking the RING domain) can promote ubiquitination of PPFIA1 and KLHL11, possibly by recruiting other E3 ligases (MID2/TRIM1 and TRIM27) as a scaffold.\",\n      \"method\": \"Affinity purification/mass spectrometry, in vitro ubiquitination assay, PDZ domain mapping, isoform comparison\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — MS interactome with in vitro ubiquitination validation for multiple substrates\",\n      \"pmids\": [\"29121065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Lnx1 forms a multiprotein complex with NMDA receptors (NMDAR) and EphB2 in hippocampal CA3 neurons. Lnx1 deletion causes NMDAR hypofunction attributable to decreased GluN2B expression in the postsynaptic density and disruption of the Lnx1-NMDAR-EphB2 complex. Specific restoration of Lnx1 or EphB2 in CA3 rescues synaptic function and social memory.\",\n      \"method\": \"Gene knockout mouse, synaptic fractionation, co-immunoprecipitation, site-specific viral rescue, electrophysiology\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO, complex confirmed by Co-IP, site-specific rescue confirms causality\",\n      \"pmids\": [\"31772302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LNX1 E3 ubiquitin ligase activity ubiquitinates GlyT2 at a cytoplasmic C-terminal lysine cluster (K751, K773, K787, K791) via its RING domain, regulating GlyT2 expression levels and transport activity. Genetic deletion of endogenous LNX2 in spinal cord neurons increases GlyT2 expression. LNX2 is required for PKC-mediated control of GlyT2 transport.\",\n      \"method\": \"Unbiased screening, in vitro ubiquitination assay with site-directed mutagenesis, LNX2 knockout neurons, transport activity assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — in vitro ubiquitination with lysine mapping by mutagenesis, confirmed in KO neurons with functional transport readout\",\n      \"pmids\": [\"31628376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LNX1 contributes to tumor growth by promoting p53 ubiquitination and degradation in an MDM2-dependent manner. LNX1 physically interacts with both p53 and MDM2, and LNX1 knockout cells have increased p53 stability and activated p53-dependent transcription.\",\n      \"method\": \"CRISPR-Cas9 knockout, co-immunoprecipitation, ubiquitination assay, p53 half-life measurement, xenograft tumor model\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — Co-IP, ubiquitination assay, CRISPR KO with functional readout, single lab\",\n      \"pmids\": [\"31533005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"LNX1 upregulation during temozolomide therapy promotes Numb degradation, leading to Notch1 signaling activation and expansion of glioma stem cell populations. Knockdown of LNX1 reverses Numb downregulation and intracellular Notch1 (NICD) upregulation, reduces stemness after TMZ therapy, and prolongs median survival in mouse models.\",\n      \"method\": \"Gene expression analysis (GSEA), LNX1 overexpression/knockdown, western blot for Numb/NICD, GSC assays, mouse xenograft survival\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 — mechanistic pathway confirmed by OE/KD with defined readouts in vivo and in vitro\",\n      \"pmids\": [\"33255632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Lnx1 stabilizes EphB receptors on the postsynaptic membrane by preventing their internalization. Loss of Lnx1 promotes EphB receptor internalization from the cell surface, leading to abnormal dendritic spine development and impaired synaptic formation. Constitutively active EphB2 intracellular signaling rescues synaptogenesis in Lnx1 mutant mice.\",\n      \"method\": \"Lnx1 knockout mouse, receptor surface expression assay, dendritic spine morphology analysis, epistasis with constitutively active EphB2\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined synaptic phenotype, receptor internalization assay, epistasis\",\n      \"pmids\": [\"35531068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"LNX1 and LNX2 double knockout mice lacking CNS expression of both proteins show decreased anxiety-related behaviour. Proteomic analysis identified novel LNX1/2 neuronal interacting proteins including presynaptic active zone proteins ERC1, ERC2, LIPRIN-αs (PPFIA1, PPFIA3), FCHSD2, and SRGAP2.\",\n      \"method\": \"Double knockout mouse generation, behavioural analysis, affinity purification proteomics\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean double KO with defined behavioural phenotype, MS interactome for novel partners\",\n      \"pmids\": [\"27889896\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"LNX1 mediates non-degrading ubiquitination (NDU) of RhoC specifically (not RhoA), activating RhoC. LIS1 suppresses this LNX1-mediated RhoC NDU by interfering with the LNX1 effect on RhoGDI-RhoC interaction, providing a mechanism by which reduced LIS1 levels enhance Rho activity.\",\n      \"method\": \"In vitro ubiquitination assay, co-immunoprecipitation, RhoGDI pulldown, isoform-specific comparison\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro ubiquitination with isoform specificity, mechanistic LIS1 suppression demonstrated\",\n      \"pmids\": [\"36192543\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"LNX1 is a RING-type E3 ubiquitin ligase that uses its catalytic RING domain (which functions as a Zn-RING-Zn module in a dimeric complex with Ubc13 as its E2) and four PDZ domains to recruit and ubiquitinate diverse substrates—including Numb, NEK6, GlyT2, RhoC, EphB receptors, p53 (MDM2-dependently), connexin36, and others—thereby regulating Notch signaling, synaptic receptor stability, glycinergic neurotransmission, and cell fate determination; in neurons, a shorter LNX1 isoform lacking the RING domain acts instead as a scaffold to stabilize EphB receptor complexes and NMDAR multiprotein assemblies at postsynaptic densities.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\nI'll classify each paper first, then extract discoveries only from KEEP papers.\n\n**Classification:**\n- Papers about LNX1 (canonical protein): KEEP — [1],[2],[5],[8],[9],[11],[14],[15],[17],[19],[21],[22],[25],[27],[28],[29],[32],[33],[34],[35],[38],[39],[40],[42],[43],[44],[46],[47],[48],[51],[52],[56],[59],[61],[64],[65],[66] from main corpus; [28] from gene2pubmed\n- Papers about MPDZ/MUPP1 (different gene, alias collision): EXCLUDE — [3],[4],[6],[7],[10],[12],[13],[16],[18],[20],[23],[24],[26],[30],[31],[36],[37],[41],[45],[49],[50],[53],[54],[55],[57],[58],[60],[62],[63]\n- Large interactome/proteomics surveys (not specifically about LNX1): EXCLUDE from gene2pubmed — [1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22],[23],[24],[25],[26],[27],[29],[30] (these are general interactome papers, not mechanistic LNX1 studies; exception: [28] Np9/LNX which IS about LNX1 specifically)\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1998,\n      \"finding\": \"LNX was identified as a novel Numb PTB domain-interacting protein via yeast two-hybrid screen. The interaction is mediated by the sequence motif LDNPAY in LNX, which binds the Numb PTB domain independent of tyrosine phosphorylation. LNX contains a RING finger domain and four PDZ domains. Tyrosine phosphorylation of the LDNPAY motif can generate a binding site for other PTB domain-containing proteins such as SHC.\",\n      \"method\": \"Yeast two-hybrid screen, mutational analysis, peptide competition experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal binding assays with mutagenesis, foundational discovery paper with 108 citations\",\n      \"pmids\": [\"9535908\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"LNX2 (and the related LNX1) bind to mammalian Numb and Numblike via NPXY motifs. LNX proteins form oligomers through PDZ domain interactions with PDZ-binding motifs in their C-termini and via homophilic RING finger oligomerization, suggesting they serve as molecular scaffolds that localize Numb to specific subcellular sites.\",\n      \"method\": \"Protein interaction assays, in situ hybridization, oligomerization studies\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — binding assays without full mechanistic follow-up, single study\",\n      \"pmids\": [\"11922143\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Human LNX was cloned and shown to contain four PDZ domains and an NPXY motif for Numb PTB domain binding, mapping to chromosome 4q12.\",\n      \"method\": \"cDNA cloning, sequence analysis, radiation hybrid mapping\",\n      \"journal\": \"Biochemical genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — cloning and sequence characterization, no functional assay\",\n      \"pmids\": [\"11521506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"LNX functions as a RING-type E3 ubiquitin ligase that targets Numb for ubiquitin-dependent proteasomal degradation. The isolated RING finger domain acts as an E2-dependent E3 ligase in vitro; mutation of a conserved RING cysteine abolishes activity. A region including the Numb PTB domain-binding site and the first PDZ domain is required for Numb ubiquitylation. Wild-type but not mutant LNX causes proteasome-dependent Numb degradation and enhances Notch signaling.\",\n      \"method\": \"In vitro ubiquitin ligase assay, site-directed mutagenesis, in vivo ubiquitination, proteasome inhibition, Notch signaling reporter assay\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro reconstitution with mutagenesis plus in vivo validation; 156 citations, foundational paper\",\n      \"pmids\": [\"11782429\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"LNX (LNX1) interacts with the Coxsackievirus and adenovirus receptor (CAR) intracellular tail via the second PDZ domain of LNX. Efficient CAR binding requires both the consensus PDZ-binding motif at the CAR C-terminus and upstream sequences. CAR and LNX colocalize in mammalian cells.\",\n      \"method\": \"Yeast two-hybrid screen, in vitro binding, co-immunoprecipitation, colocalization imaging\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP and in vitro binding confirming yeast two-hybrid result\",\n      \"pmids\": [\"12468544\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"The Np9 protein of human endogenous retrovirus K interacts with LNX (E3 ubiquitin ligase), involving N- and C-terminal domains of both proteins. This interaction alters subcellular localization of LNX. Np9 is itself unstable and degraded via the proteasome; ectopic Numb stabilizes Np9, suggesting Np9 may affect tumorigenesis through the LNX/Numb/Notch pathway.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, proteasome inhibition assay, subcellular localization\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP with localization data, single study\",\n      \"pmids\": [\"15367597\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"LNX1 is specifically expressed in perisynaptic Schwann cells (but not myelinating Schwann cells) at the neuromuscular junction and directly interacts with ErbB2. LNX1 protein levels are inversely correlated with responsiveness of perisynaptic Schwann cells to neuregulin-1, and LNX1 staining disappears upon denervation while ErbB2 reappears, suggesting LNX1 regulates neuregulin-1/ErbB signaling by promoting ErbB2 degradation.\",\n      \"method\": \"Immunostaining, direct protein interaction assay, developmental expression profiling, denervation model\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct interaction identified with localization and developmental correlation, single lab\",\n      \"pmids\": [\"16122940\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Human LNX interacts with SKIP (Ski interacting protein) via its PDZ domains. Co-immunoprecipitation confirmed LNX-SKIP interaction in HEK293 cells. LNX affects subcellular localization of Numb, suggesting LNX functions as a molecular anchor localizing Numb to the subcellular site of its interaction with Notch.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, subcellular localization assay\",\n      \"journal\": \"The international journal of biochemistry & cell biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP confirmed Y2H interaction with localization data, single lab\",\n      \"pmids\": [\"16002321\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Lnx-like (Lnx-l, ortholog of LNX1 in zebrafish) functions as a critical regulator of dorso-ventral axis formation. Lnx-l was identified as an E3 ubiquitin ligase for Bozozok (Boz), a homeodomain transcriptional repressor. Lnx-l induces K48-linked polyubiquitylation of Boz leading to proteasomal degradation. Dorsalization by Boz overexpression is suppressed by Lnx-l; Lnx-l cannot counteract Boz lacking the Lnx-l binding motif. Depletion of Lnx-l causes embryonic dorsalization rescued by Boz attenuation.\",\n      \"method\": \"Antisense morpholino knockdown, K48-polyubiquitylation assay, genetic epistasis in zebrafish, domain mapping\",\n      \"journal\": \"Nature cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vivo ubiquitination with K48-linkage specificity, genetic epistasis across multiple manipulations; 24 citations in Nature Cell Biology\",\n      \"pmids\": [\"19668196\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"LNX interacts with RhoC via its first PDZ domain, as identified by yeast two-hybrid and confirmed by co-immunoprecipitation in mammalian cells. Co-expression of LNX causes RhoC to relocalize from cytoplasm to nucleus. Co-expression of RhoC reduces LNX-induced AP-1 transcriptional activity, suggesting LNX and RhoC form a complex that modulates AP-1-mediated transcription.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, subcellular localization, AP-1 transcriptional reporter assay\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — Co-IP with localization and functional reporter assay, single lab\",\n      \"pmids\": [\"19701800\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Lnx-2b (zebrafish LNX ortholog) restricts gsc expression to the dorsal mesoderm by limiting Nodal and Bozozok activity. Overexpression of Boz together with depletion of Lnx-2b (but not either alone) causes robust gsc expression in all blastomeres, demonstrating that maternally deposited Lnx-2b restricts organizer expansion through ubiquitin-mediated control of Boz.\",\n      \"method\": \"Morpholino knockdown, single-cell injection, epistasis analysis in zebrafish\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in vivo with targeted injections, single lab\",\n      \"pmids\": [\"20971071\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Knockdown of LNX by siRNA in HEK293 cells causes G0/G1 cell cycle arrest. Transcriptomic analysis revealed downregulation of β-catenin, MAPK, NFκB, c-Myc-dependent pathways and upregulation of p53 and TGF-β-dependent pathways, suggesting LNX participates in cell cycle regulation through multiple signaling cascades.\",\n      \"method\": \"siRNA knockdown, flow cytometry cell cycle analysis, expression microarray, qRT-PCR\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — KD with phenotype but pathway placement is correlative/transcriptomic\",\n      \"pmids\": [\"21104141\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Human protein array screening of 8,000 proteins with isolated LNX1 PDZ domains identified 53 potential binding partners. Integration with other methods assembled 220 LNX1 interacting proteins. Six novel LNX1 binding partners were confirmed: KCNA4, PAK6, PLEKHG5, PKC-alpha1, TYK2, and PBK. LNX1 is proposed to function as a signalling scaffold.\",\n      \"method\": \"Human protein array, co-immunoprecipitation, bioinformatic analysis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — proteome-scale screen with selected Co-IP validation, single lab\",\n      \"pmids\": [\"22087225\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Phylogenetic analysis revealed that LNX PDZ domains are closely related to the four C-terminal PDZ domains of MUPP1. Novel interactions of LNX1 and LNX2 with three known MUPP1 ligands were identified by yeast two-hybrid assays, demonstrating conservation of binding specificity between LNX and MUPP1 PDZ domains.\",\n      \"method\": \"Phylogenetic analysis, yeast two-hybrid interaction assays\",\n      \"journal\": \"BMC evolutionary biology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — Y2H interactions only, evolutionary inference\",\n      \"pmids\": [\"21827680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"A proteomic strategy integrating peptide library screening and in vitro ubiquitination assays identified multiple LNX substrates. The substrate recognition mechanism involves LNX PDZ domains binding C-termini of target proteins. Two novel endogenous substrates, PBK and BCR, were confirmed in vivo. LNX1-mediated ubiquitination and degradation of PBK inhibits cell proliferation and enhances sensitivity to doxorubicin-induced apoptosis.\",\n      \"method\": \"Random peptide library yeast two-hybrid, in vitro ubiquitination assay, in vivo ubiquitination, cell proliferation assay, apoptosis assay\",\n      \"journal\": \"Journal of proteome research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro ubiquitination reconstitution with in vivo validation and functional cellular phenotype; multiple orthogonal methods\",\n      \"pmids\": [\"22889411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"LNX1 protein expression in brain was demonstrated for the first time. Cell-type-specific expression of LNX isoforms was clarified in CNS and PNS. The 5' UTR of Lnx1_variant 2 mRNA (generating LNX1p70) strongly suppresses protein production via upstream open reading frames (uORFs) and a sequence element that decreases mRNA levels and translational efficiency. LNX1p80 protein levels are regulated by proteasomal degradation. These mechanisms explain the very low levels of LNX1 in vivo.\",\n      \"method\": \"Western blot, luciferase reporter assays, uORF analysis, proteasome inhibition\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — reporter assays with mutagenesis of regulatory elements, single lab\",\n      \"pmids\": [\"25200495\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Mice lacking both LNX1 (in CNS) and LNX2 (globally) are healthy with unaltered Numb protein levels and no neuroanatomical defects indicative of NUMB dysfunction, demonstrating that LNX1/LNX2 are not essential for NUMB regulation in vivo. Double knockout mice exhibit decreased anxiety-related behaviour. Proteomic analysis identified LNX1/LNX2 interactions with presynaptic active zone proteins ERC1, ERC2, LIPRIN-αs (PPFIA1, PPFIA3), and F-BAR domain proteins FCHSD2 and SRGAP2.\",\n      \"method\": \"LNX1/LNX2 double knockout mouse, behavioural testing (open field, elevated plus maze), proteomics/mass spectrometry\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with defined behavioral phenotype and proteomic interactome characterization\",\n      \"pmids\": [\"27889896\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Proteomic analysis of the LNX1 interactome by affinity purification/mass spectrometry identified many novel LNX1-interacting proteins, with many mapping to PDZ2 and showing specificity for LNX1 over LNX2. PPFIA1 (liprin-α1), KLHL11, KIF7, and ERC2 are ubiquitination substrates of LNX1. LNX1 ubiquitination of liprin-α1 requires a PDZ-binding motif with a C-terminal cysteine binding LNX1 PDZ2. The neuronal LNX1p70 isoform (lacking the RING domain) can promote ubiquitination of PPFIA1 and KLHL11 by recruiting other E3 ligases (MID2/TRIM1, TRIM27) as a scaffold.\",\n      \"method\": \"Affinity purification/mass spectrometry, in vitro ubiquitination assay, co-immunoprecipitation, domain mapping\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — AP-MS interactome plus in vitro ubiquitination validation; multiple substrates confirmed, novel scaffold model for catalytic-dead isoform\",\n      \"pmids\": [\"29121065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"The crystal structure of the LNX1 ubiquitination domain (Zn-RING-Zn) in complex with Ubc13~Ubiquitin was determined. The RING domain is flanked by two zinc-finger motifs, both required for ubiquitination activity. In the heterodimeric complex, ubiquitin from one monomer shares more buried surface area with LNX1 from the other monomer—a unique and essential feature for catalysis. Ubc13/Ube2V2 was identified as a functional E2 for LNX1 in vitro. Dimeric LNX1 recruits ubiquitin-loaded Ubc13 for Ub transfer.\",\n      \"method\": \"Crystal structure determination, in vitro ubiquitination assay, mutagenesis\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure with functional validation and mutagenesis; mechanistic insight into dimeric catalysis\",\n      \"pmids\": [\"29496391\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"LNX1 and LNX2 colocalize with connexin36 (Cx36)-containing gap junctions at electrical synapses in adult mouse brain. LNX1 and LNX2 directly interact with Cx36 via their second PDZ domain (confirmed by pull-down). Co-transfection of E3-ligase-competent LNX1/LNX2 with Cx36 leads to loss of Cx36-containing gap junctions between cells, whereas ligase-inactive isoforms do not, indicating LNX-mediated ubiquitination of Cx36 promotes its internalization at electrical synapses.\",\n      \"method\": \"Immunofluorescence colocalization, co-immunoprecipitation, PDZ pull-down, cotransfection with ligase-active vs. inactive isoforms, LNX null mice\",\n      \"journal\": \"The European journal of neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal Co-IP, domain pull-down, functional loss-of-junction phenotype with ligase-dead controls, confirmed in KO mice\",\n      \"pmids\": [\"30295974\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Postsynaptic LNX1 in hippocampal CA3 neurons is essential for mossy fiber (MF) axon targeting during the postnatal period. Lnx1 deletion causes defective synaptic arrangement and aberrant presynaptic terminals. EphB1 and EphB2 receptors are novel LNX1-binding proteins forming a multiprotein complex stabilized on the CA3 membrane by LNX1, which prevents proteasomal degradation of EphB receptors. EphB1 and EphB2 independently transduce distinct signals controlling MF pruning and targeting. Constitutively active EphB2 kinase rescues MF terminal structure in Lnx1 mutant mice.\",\n      \"method\": \"Lnx1 knockout mice, MF axon tracing, co-immunoprecipitation, proteasome inhibition assay, constitutively active EphB2 rescue experiment\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined neuroanatomical phenotype, biochemical complex identification, and genetic rescue\",\n      \"pmids\": [\"30185604\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LNX1 is an E3 ubiquitin ligase for NEK6; miR-325-3p targets LNX1 mRNA, reducing LNX1 levels, and thereby prevents proteasomal degradation of NEK6 in macrophages infected with M. tuberculosis. Accumulation of NEK6 activates STAT3 signaling, inhibiting apoptosis and promoting intracellular bacterial survival.\",\n      \"method\": \"Cell and mouse models, miRNA overexpression/knockdown, LNX1 overexpression/knockdown, western blot for NEK6 protein levels, STAT3 signaling assay, bacterial survival assay\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — LNX1 identified as E3 for NEK6 with in vivo functional consequence, but detailed mechanistic reconstitution not provided\",\n      \"pmids\": [\"32487755\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LDOC1 forms a protein complex with phospho-JAK2 and LNX1, targeting pJAK2 for ubiquitin-dependent proteasomal degradation. LDOC1 acts as a bridge between pJAK2 and LNX1 E3 ubiquitin ligase; LDOC1 deficiency attenuates LNX1-pJAK2 interaction, reducing pJAK2 ubiquitination and activating STAT3 signaling.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence confocal microscopy, ubiquitination assay, LDOC1 KD/OE in lung cancer cells\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — Co-IP complex identification with functional ubiquitination consequence, single lab\",\n      \"pmids\": [\"30634502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"E3 ubiquitin ligases LNX1 and LNX2 ubiquitinate the presynaptic glycine transporter GlyT2. The RING-finger domain of LNX1/2 ubiquitinates a cytoplasmic C-terminal lysine cluster in GlyT2 (K751, K773, K787, K791), regulating GlyT2 expression and transport activity. Genetic deletion of LNX2 in spinal cord neurons increases GlyT2 expression. LNX2 is required for PKC-mediated control of GlyT2 transport.\",\n      \"method\": \"Unbiased screening, in vitro ubiquitination assay, site-directed mutagenesis of GlyT2 lysines, LNX2 knockout neurons, transport activity assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro ubiquitination with lysine mutagenesis and KO neuron validation with functional transport readout\",\n      \"pmids\": [\"31628376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"A hippocampal Lnx1-NMDAR-EphB2 multiprotein complex is required for initial social memory in juvenile mice. Lnx1 deficiency causes NMDAR hypofunction with decreased GluN2B in the postsynaptic density, disruption of the Lnx1-NMDAR-EphB2 complex, impaired neuronal activity in CA3, and social memory deficits. Specific restoration of Lnx1 or EphB2 in CA3 rescues synaptic function and social memory.\",\n      \"method\": \"Lnx1 knockout mice, co-immunoprecipitation, PSD fractionation, stereotaxic viral rescue, electrophysiology, behavioral testing\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO with complex biochemistry, regional viral rescue, and electrophysiological validation\",\n      \"pmids\": [\"31772302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"LNX1 interacts with p53 and MDM2, and increases p53 ubiquitination in an MDM2-dependent manner, thereby decreasing p53 half-life and inhibiting p53-dependent transcription. LNX1 knockout (CRISPR) in p53 wild-type cancer cells increases p53 stability and activates p53 transcription. LNX1 is required for efficient tumor growth in cell culture and mouse xenograft models.\",\n      \"method\": \"CRISPR-Cas9 knockout, lentiviral overexpression, co-immunoprecipitation, ubiquitination assay, p53 half-life measurement, xenograft tumor model\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — CRISPR KO with reciprocal OE, biochemical complex, ubiquitination assay, and in vivo tumor model\",\n      \"pmids\": [\"31533005\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"In zebrafish, glycine signaling suppresses lnx1 expression; reduced Lnx1 stabilizes Numb protein and reduces Notch activity (measured as her4.1 expression), promoting neural stem cell (NSC) differentiation. Lnx1 overexpression increases NSC proliferation and causes neural tube closure defects. Knockdown of lnx1 blocks these effects of glycine signaling, placing lnx1 in the glycine→Lnx1→Numb→Notch pathway controlling NSC proliferation.\",\n      \"method\": \"Zebrafish morpholino knockdown, lnx1 overexpression, Notch activity reporter, in situ hybridization, neural tube phenotype analysis\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in vivo with pathway reporter readout, single lab\",\n      \"pmids\": [\"30833887\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"LNX1 upregulation after temozolomide (TMZ) therapy in glioblastoma leads to Numb degradation, activation of Notch1 (increased NICD), and expansion of glioma stem cell (GSC) populations. LNX1 overexpression activates Notch1 and increases GSC populations; LNX1 knockdown reduces NICD, decreases stemness after TMZ, and prolongs median survival in a mouse model. This places LNX1 as a regulator of chemotherapy-induced stemness via the Numb/Notch1 axis.\",\n      \"method\": \"GSEA on PDX cells, LNX1 OE/KD in PDX lines, Notch1 signaling measurement (NICD western), GSC population assay, mouse survival model\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — OE/KD with mechanistic pathway readout and in vivo survival endpoint, single lab\",\n      \"pmids\": [\"33255632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"LNX1 contributes to cell cycle progression; LNX1 knockout delays cell cycle, downregulates cyclin D1 and cyclin E1, and upregulated LNX1 increases S and G2/M populations. LNX1 upregulation activates cell cycle progression and increases resistance to cisplatin-mediated cell death.\",\n      \"method\": \"CRISPR-Cas9 KO, lentiviral overexpression, flow cytometry, western blot for cyclins\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean CRISPR KO with reciprocal OE and specific molecular markers, single lab\",\n      \"pmids\": [\"34439220\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"LNX1 performs non-degrading ubiquitination (NDU) of RhoC (but not RhoA), promoting RhoC activity. LIS1 (PAFAH1B1) negatively regulates LNX1-mediated ubiquitination of RhoC by inhibiting LNX1's effects on RhoGDI-RhoC interaction. This LIS1-LNX1-RhoC module represents an evolutionarily acquired function present only in vertebrates, providing a mechanism for isoform-specific Rho regulation.\",\n      \"method\": \"In vitro ubiquitination assay, RhoGDI interaction assay, LIS1 overexpression/knockdown, RhoC activity assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro biochemistry with isoform specificity and molecular mechanism, single lab\",\n      \"pmids\": [\"36192543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"HO-1 controls LNX1 expression in hepatic macrophages; LNX1 expression is strongly suppressed in HO-1-deficient macrophages. LNX1 drives M2-like macrophage polarization; Notch1 (downstream target of LNX1-mediated Numb degradation) is increased in HO-1-deficient macrophages. Transient LNX1 overexpression in HO-1-deficient macrophages treated with heme rescues M2-like polarization, defining a HO-1→LNX1→Notch1 pathway in macrophage polarization and liver fibrosis.\",\n      \"method\": \"RiboTag RNA-seq, LNX1 overexpression in HO-1-deficient macrophages, Notch1 western blot, macrophage polarization assay\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — pathway placement via gene expression and OE rescue, single lab\",\n      \"pmids\": [\"36093061\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Lnx1 stabilizes EphB receptors at the postsynaptic membrane by preventing their internalization. Loss of Lnx1 promotes EphB receptor internalization from the cell surface, leading to abnormal dendritic spine development and impaired synaptogenesis. Constitutively active EphB2 intracellular signaling rescues synaptogenesis in Lnx1 mutant mice.\",\n      \"method\": \"Lnx1 knockout mice, receptor internalization assay, dendritic spine morphology analysis, constitutively active EphB2 rescue\",\n      \"journal\": \"Frontiers in molecular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — KO with defined spine phenotype and molecular mechanism, confirmed by genetic rescue\",\n      \"pmids\": [\"35531068\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Neuronal LNX1 isoforms (LNX1p70, which lack the RING catalytic domain) act as stabilizing scaffolds for shared interaction partners, while LNX2 promotes their ubiquitination and degradation. Single and double LNX1/LNX2 knockout behavioral analysis shows LNX2 plays a more prominent role in altered dark-light emergence and risk-taking behavior, while LNX1 loss contributes to anxiety phenotypes and determines body weight. Lnx1 knockout affects ultrasonic vocalizations of pups, revealing a role in social communication.\",\n      \"method\": \"Single and double LNX1/LNX2 knockout mice, behavioral battery (open field, EPM, dark-light, marble burying, novel object recognition, ultrasonic vocalizations), body weight analysis\",\n      \"journal\": \"Behavioral and brain functions\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with defined behavioral phenotypes, distinction between LNX1 scaffold vs. LNX2 E3 roles\",\n      \"pmids\": [\"40269869\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"LNX1 is a RING-type E3 ubiquitin ligase whose catalytic domain (embedded in a Zn-RING-Zn architecture that functions as a homodimer recruiting Ubc13/Ube2V2) is coupled to four PDZ domains that recruit substrates including Numb, ErbB2, NEK6, GlyT2, PBK, BCR, connexin36, liprin-α1, p53 (MDM2-dependently), and RhoC (non-degradatively); by ubiquitinating Numb for proteasomal degradation LNX1 activates Notch signaling, while its PDZ scaffold function stabilizes EphB receptors and NMDAR complexes at postsynaptic densities to regulate hippocampal synaptogenesis, mossy fiber targeting, and social memory, with the neuronal LNX1p70 isoform (which lacks the RING domain) acting as a non-catalytic scaffold that recruits other E3 ligases to ubiquitinate shared substrates.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"LNX1 is a RING-type E3 ubiquitin ligase that couples PDZ domain-mediated substrate recognition with ubiquitin transfer to regulate Notch signaling, synaptic organization, and diverse signaling pathways. Its catalytic module adopts a dimeric Zn-RING-Zn architecture that partners with the E2 enzyme Ubc13/Ube2V2, and its four PDZ domains recruit substrates including Numb, NEK6, GlyT2, connexin36, PBK, BCR, and phospho-JAK2 for K48-linked proteasomal degradation, while mediating non-degrading ubiquitination of RhoC to activate Rho signaling [PMID:11782429, PMID:29496391, PMID:31628376, PMID:36192543]. LNX1-dependent degradation of Numb activates Notch signaling in contexts including glioma stem cell maintenance, and LNX1 promotes p53 degradation in an MDM2-dependent manner to support tumor growth [PMID:33255632, PMID:31533005]. In hippocampal neurons, a shorter LNX1 isoform lacking the RING domain functions as a postsynaptic scaffold that stabilizes EphB receptor–NMDAR complexes on the cell surface; Lnx1 deletion causes EphB internalization, NMDAR hypofunction, defective mossy fiber targeting, abnormal spine morphology, and impaired social memory [PMID:30185604, PMID:31772302, PMID:35531068].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"Identification of LNX1 as a PDZ- and RING-containing Numb-binding protein established the first link between this E3 ligase scaffold and cell-fate determinant biology.\",\n      \"evidence\": \"Yeast two-hybrid screen with Numb PTB domain; LDNPAY binding motif mapped by mutagenesis\",\n      \"pmids\": [\"9535908\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No enzymatic activity demonstrated at this stage\", \"Functional consequence of Numb binding unknown\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Discovery that LNX1 oligomerizes via its PDZ domains and RING finger revealed it can simultaneously self-associate and bind Numb, suggesting a scaffolding function beyond catalysis.\",\n      \"evidence\": \"Protein interaction assays and in situ hybridization in mouse tissues\",\n      \"pmids\": [\"11922143\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Oligomerization shown mainly by overexpression; stoichiometry and endogenous oligomeric state not resolved\", \"Functional consequence of oligomerization not tested\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Reconstitution of LNX1 E3 ubiquitin ligase activity and demonstration that it targets Numb for proteasomal degradation to enhance Notch signaling established LNX1's core enzymatic function and primary signaling output.\",\n      \"evidence\": \"In vitro ubiquitination with RING mutagenesis, in vivo Numb degradation assay, Notch reporter in mammalian cells\",\n      \"pmids\": [\"11782429\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"E2 partner not identified\", \"In vivo Notch phenotype in animal model not demonstrated\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Mapping LNX1's second PDZ domain as the binding site for the Coxsackievirus and adenovirus receptor (CAR) showed that individual PDZ domains recruit distinct partners, expanding the substrate/interactor repertoire.\",\n      \"evidence\": \"Yeast two-hybrid, reciprocal Co-IP, colocalization in mammalian cells\",\n      \"pmids\": [\"12468544\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LNX1 ubiquitinates CAR was not tested\", \"Functional consequence at cell junctions unknown\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Localization of LNX1 to perisynaptic Schwann cells and its inverse relationship with ErbB2 responsiveness implicated LNX1 in neuregulin signaling regulation at the neuromuscular junction.\",\n      \"evidence\": \"Immunostaining and Co-IP in sciatic nerve preparations; denervation experiments\",\n      \"pmids\": [\"16122940\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No direct ubiquitination of ErbB2 by LNX1 shown\", \"Causal role not tested by knockout or knockdown\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Demonstration that the zebrafish LNX ortholog ubiquitinates Bozozok via K48 linkage to control dorso-ventral patterning provided the first in vivo genetic evidence for LNX E3 ligase function in embryonic axis formation.\",\n      \"evidence\": \"Morpholino knockdown, in vivo ubiquitination with K48 linkage, epistasis with Boz binding-deficient mutant in zebrafish\",\n      \"pmids\": [\"19668196\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mammalian ortholog contribution to axis determination not tested\", \"Whether mammalian LNX1 ubiquitinates homeodomain repressors is unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"A protein array screen identifying 53 PDZ-mediated binding partners, with six confirmed by Co-IP, established LNX1 as a broad PDZ-scaffold hub integrating diverse signaling proteins.\",\n      \"evidence\": \"Human protein array with isolated PDZ domains; Co-IP validation for KCNA4, PAK6, PLEKHG5, PKC-α1, TYK2, PBK\",\n      \"pmids\": [\"22087225\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Most of the 53 partners not independently validated\", \"Ubiquitination of these partners not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identification of PBK and BCR as LNX1 ubiquitination substrates, with PBK degradation inhibiting proliferation and sensitizing cells to apoptosis, revealed a tumor-suppressive function for LNX1.\",\n      \"evidence\": \"Yeast two-hybrid peptide library, in vitro ubiquitination, endogenous substrate degradation, proliferation and apoptosis assays\",\n      \"pmids\": [\"22889411\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo tumor model not used\", \"Ubiquitin chain type on PBK/BCR not determined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"LNX1/LNX2 double knockout mice showing decreased anxiety and proteomic identification of presynaptic active zone partners (ERC1, ERC2, PPFIA1, PPFIA3) linked LNX proteins to synaptic organization and behavior.\",\n      \"evidence\": \"Double knockout mouse, behavioral assays, affinity purification mass spectrometry\",\n      \"pmids\": [\"27889896\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Individual contributions of LNX1 vs. LNX2 to anxiety phenotype not separated\", \"Mechanism linking active zone partners to behavioral output unclear\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The crystal structure of the LNX1 Zn-RING-Zn domain in complex with Ubc13~Ub resolved the catalytic mechanism, showing how dimeric LNX1 positions ubiquitin-loaded Ubc13 for transfer through inter-subunit contacts.\",\n      \"evidence\": \"X-ray crystallography, in vitro ubiquitination with mutagenesis confirming zinc-finger contributions\",\n      \"pmids\": [\"29496391\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of full-length LNX1 with PDZ domains not determined\", \"How substrate-bound PDZ domains orient substrates relative to the RING active site is unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"LNX1 was shown to ubiquitinate connexin36 at neuronal electrical synapses through its RING domain, causing gap junction internalization, while RING-inactive isoforms did not, distinguishing catalytic from scaffolding functions of different isoforms in vivo.\",\n      \"evidence\": \"Immunofluorescence colocalization in brain, Co-IP, GST pull-down to PDZ2, cotransfection of RING-active vs. RING-inactive isoforms, LNX null mouse controls\",\n      \"pmids\": [\"30295974\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ubiquitin chain type on Cx36 not determined\", \"Whether Cx36 gap junction loss affects circuit function not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Lnx1 knockout mice revealed that LNX1 stabilizes EphB receptors on the postsynaptic surface to direct mossy fiber targeting; constitutively active EphB2 rescued the mutant phenotype, establishing an epistatic relationship.\",\n      \"evidence\": \"Lnx1 KO mouse, Co-IP, synaptic fractionation, morphological analysis, constitutively active EphB2 rescue\",\n      \"pmids\": [\"30185604\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How the RING-lacking p70 isoform prevents EphB degradation mechanistically is unresolved\", \"Upstream signals controlling LNX1-EphB interaction unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Multiple substrates (GlyT2, NEK6, p53/MDM2, pJAK2, PPFIA1, KLHL11) were validated as LNX1 ubiquitination targets in parallel studies, consolidating LNX1's role as a multi-substrate E3 ligase spanning neurotransmission, innate immunity, and oncogenesis.\",\n      \"evidence\": \"In vitro ubiquitination with lysine mapping (GlyT2), miRNA epistasis and mouse infection model (NEK6), CRISPR KO and p53 half-life (p53), LDOC1 complex Co-IP (pJAK2), AP-MS with in vitro assay (PPFIA1/KLHL11)\",\n      \"pmids\": [\"31628376\", \"32487755\", \"31533005\", \"30634502\", \"29121065\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrate hierarchy and competition among PDZ-recruited targets not characterized\", \"Tissue-specific substrate selection mechanism unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Lnx1 deletion disrupted the Lnx1–NMDAR–EphB2 postsynaptic complex in CA3 neurons, causing NMDAR hypofunction and social memory deficits that were rescued by site-specific Lnx1 or EphB2 re-expression, establishing LNX1 as an essential scaffold for glutamatergic synapse function.\",\n      \"evidence\": \"KO mouse, synaptic fractionation, Co-IP for NMDAR-EphB2-Lnx1 complex, electrophysiology, CA3-specific viral rescue\",\n      \"pmids\": [\"31772302\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LNX1 p70 or full-length mediates the scaffold function in vivo is not resolved\", \"Role in other hippocampal subfields not explored\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"LNX1 upregulation during temozolomide therapy drives Numb degradation and Notch1 activation to expand glioma stem cells, demonstrating that the LNX1–Numb–Notch axis is co-opted in therapy resistance.\",\n      \"evidence\": \"GSEA, LNX1 overexpression/knockdown, NICD western blot, GSC assays, mouse xenograft survival\",\n      \"pmids\": [\"33255632\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of LNX1 upregulation by TMZ not identified\", \"Whether LNX1 inhibition synergizes with TMZ in patient-derived models not tested\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"LNX1-mediated non-degrading ubiquitination of RhoC (but not RhoA) activates RhoC by disrupting RhoGDI binding, and LIS1 suppresses this activity, linking LNX1 to Rho-dependent migration and lissencephaly-associated pathways.\",\n      \"evidence\": \"In vitro ubiquitination, RhoGDI pulldown, isoform-specific comparison, LIS1 co-expression\",\n      \"pmids\": [\"36192543\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitin chain type mediating non-degrading activation not characterized\", \"In vivo relevance for neuronal migration not tested\", \"Single laboratory finding\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Lnx1 loss was shown to promote EphB receptor internalization from the cell surface, causing abnormal dendritic spine development and impaired synaptogenesis, further solidifying the stabilization model for the RING-lacking neuronal isoform.\",\n      \"evidence\": \"Lnx1 KO mouse, receptor surface expression assay, dendritic spine morphology, epistasis with constitutively active EphB2\",\n      \"pmids\": [\"35531068\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which the RING-lacking isoform blocks receptor internalization remains unresolved\", \"Whether clathrin-dependent or ubiquitin-dependent endocytosis is involved is untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis for how PDZ-bound substrates are positioned relative to the dimeric RING domain for ubiquitin transfer, the tissue-specific regulation of LNX1 isoform expression, and how the RING-lacking p70 isoform mechanistically stabilizes EphB receptors and recruits heterologous E3 ligases.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length structure with PDZ domains and substrate not available\", \"Isoform-specific expression regulation unknown\", \"Mechanism of p70 scaffolding for heterologous E3 ligases (MID2/TRIM27) not validated in vivo\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 6, 9, 10, 11, 13, 18, 19]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [2, 12, 16, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 8]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [11, 12, 21]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 9, 10, 13, 18]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 6, 14, 20, 23]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [11, 12, 17, 18]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"R-HSA-1500931\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"complexes\": [\n      \"LNX1-EphB-NMDAR postsynaptic complex\",\n      \"LNX1-Ubc13/Ube2V2 E2-E3 complex\"\n    ],\n    \"partners\": [\n      \"NUMB\",\n      \"EPHB2\",\n      \"EPHB1\",\n      \"GJD2\",\n      \"GRIN2B\",\n      \"UBE2N\",\n      \"PPFIA1\",\n      \"PAFAH1B1\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"LNX1 is a RING-type E3 ubiquitin-protein ligase that couples a Zn-RING-Zn catalytic domain—functioning as a homodimer that recruits Ubc13/Ube2V2—with four PDZ domains that select substrates and scaffold multiprotein complexes [PMID:29496391, PMID:11782429]. Through ubiquitin-dependent degradation of Numb, LNX1 activates Notch signaling to regulate neural stem cell proliferation, glioma stem cell expansion, and macrophage polarization [PMID:11782429, PMID:30833887, PMID:33255632, PMID:36093061]; additional substrates targeted for proteasomal degradation include PBK, BCR, NEK6, connexin36, and liprin-α1, while non-degradative ubiquitination of RhoC modulates Rho-GTPase activity [PMID:22889411, PMID:30295974, PMID:29121065, PMID:36192543]. In the hippocampus, LNX1 acts as a postsynaptic scaffold that stabilizes EphB receptors and an NMDAR–EphB2 complex at the membrane, and loss of Lnx1 causes defective mossy fiber targeting, impaired synaptogenesis, and social memory deficits, while the neuronal LNX1p70 isoform—lacking the RING domain—serves as a non-catalytic scaffold recruiting other TRIM-family E3 ligases to ubiquitinate shared partners [PMID:30185604, PMID:31772302, PMID:35531068, PMID:29121065].\",\n  \"teleology\": [\n    {\n      \"year\": 1998,\n      \"claim\": \"The initial question was what proteins interact with the Numb PTB domain; yeast two-hybrid screening identified LNX as a novel RING-finger and PDZ-domain protein that binds Numb via an NPXY-like motif, establishing the founding interaction of the LNX field.\",\n      \"evidence\": \"Yeast two-hybrid with Numb PTB domain bait, mutational and peptide competition analyses in vitro\",\n      \"pmids\": [\"9535908\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No functional consequence of the Numb–LNX interaction was tested\", \"Enzymatic activity of the RING domain was not assessed\", \"In vivo relevance of the interaction was unknown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"The critical question of whether the RING domain confers E3 ligase activity was answered: LNX ubiquitinates Numb in a RING-dependent manner, targets it for proteasomal degradation, and thereby activates Notch signaling, establishing LNX as a functional E3 ligase in the Numb/Notch pathway.\",\n      \"evidence\": \"In vitro reconstituted ubiquitin ligase assay, RING cysteine mutagenesis, proteasome inhibitor treatment, Notch reporter assay in mammalian cells\",\n      \"pmids\": [\"11782429\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The E2 partner(s) were not identified\", \"In vivo physiological requirement for LNX-mediated Numb degradation was untested\", \"Other substrates beyond Numb were unknown\"]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"The scope of LNX PDZ-domain interactions was broadened when LNX1 was shown to bind the Coxsackievirus and adenovirus receptor (CAR) via PDZ2, establishing the PDZ domains as versatile substrate-recruitment modules.\",\n      \"evidence\": \"Yeast two-hybrid, co-immunoprecipitation, and colocalization in mammalian cells\",\n      \"pmids\": [\"12468544\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CAR is a ubiquitination substrate of LNX1 was not tested\", \"Functional consequence for viral entry or cell adhesion was not determined\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Cell-type-specific expression studies at the neuromuscular junction revealed LNX1 in perisynaptic Schwann cells and its interaction with ErbB2, suggesting a role in regulating neuregulin signaling at synapses and extending LNX1 biology beyond the Numb/Notch axis.\",\n      \"evidence\": \"Immunostaining of NMJ, direct protein interaction assay, denervation model correlation\",\n      \"pmids\": [\"16122940\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct ubiquitination of ErbB2 by LNX1 was not demonstrated\", \"Functional rescue experiments were not performed\", \"Mechanism of ErbB2 downregulation remained correlative\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Zebrafish studies demonstrated an in vivo developmental requirement: LNX orthologs ubiquitinate the homeodomain protein Bozozok via K48-linked chains for proteasomal degradation, restricting dorsal organizer expansion and controlling dorsoventral axis formation.\",\n      \"evidence\": \"Morpholino knockdown, K48-polyubiquitination assay, genetic epistasis in zebrafish embryos\",\n      \"pmids\": [\"19668196\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether mammalian LNX1 has analogous developmental patterning roles was unknown\", \"The identity of the E2 was not determined in vivo\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"A systematic substrate-discovery approach identified PBK and BCR as endogenous LNX1 substrates and showed that LNX1-mediated PBK degradation inhibits cell proliferation and sensitizes cells to apoptosis, expanding the substrate repertoire and linking LNX1 to cell cycle control.\",\n      \"evidence\": \"Random peptide library screen, in vitro ubiquitination, in vivo ubiquitination assay, proliferation and apoptosis assays\",\n      \"pmids\": [\"22889411\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether PBK/BCR are physiological substrates in normal tissues was not established\", \"The PDZ domain specificity for each substrate was not fully mapped\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"The long-standing assumption that LNX1 is a major Numb regulator in vivo was overturned: LNX1/LNX2 double-knockout mice showed normal Numb levels and no neuroanatomical defects attributable to Numb dysfunction, but exhibited decreased anxiety behavior, redirecting attention toward synaptic scaffold functions.\",\n      \"evidence\": \"LNX1/LNX2 double-knockout mice, behavioral testing, proteomics identifying presynaptic active zone interactors (ERC1/2, liprin-αs, FCHSD2, SRGAP2)\",\n      \"pmids\": [\"27889896\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Compensatory mechanisms that maintain Numb levels were not identified\", \"Tissue-specific Numb regulation (e.g., in specific developmental windows) was not ruled out\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"AP-MS interactomics and in vitro assays revealed liprin-α1, KLHL11, KIF7, and ERC2 as ubiquitination substrates and, critically, demonstrated that the RING-less LNX1p70 neuronal isoform acts as a non-catalytic scaffold that recruits TRIM-family E3 ligases (MID2/TRIM1, TRIM27) to ubiquitinate shared substrates.\",\n      \"evidence\": \"Affinity purification–mass spectrometry, in vitro ubiquitination with domain mapping, Co-IP for TRIM E3 recruitment\",\n      \"pmids\": [\"29121065\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether TRIM E3 recruitment by LNX1p70 occurs at synapses in vivo was not shown\", \"Structural basis for the LNX1p70–TRIM interaction was not determined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Structural determination of the Zn-RING-Zn domain in complex with Ubc13~Ub resolved how LNX1 catalyzes ubiquitin transfer: the homodimeric architecture creates a unique trans-monomer ubiquitin-sharing surface essential for catalysis, identifying Ubc13/Ube2V2 as the functional E2.\",\n      \"evidence\": \"Crystal structure of LNX1 Zn-RING-Zn:Ubc13~Ub complex, mutagenesis, in vitro ubiquitination\",\n      \"pmids\": [\"29496391\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How dimerization is regulated in cells was not addressed\", \"Chain-type specificity (K48 vs. K63) conferred by E2 choice was not fully resolved for all substrates\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Two concurrent studies established LNX1 as a postsynaptic scaffold essential for hippocampal circuit wiring: LNX1 stabilizes EphB1/B2 receptors on the CA3 membrane, prevents their internalization, and organizes an NMDAR–EphB2 complex required for mossy fiber targeting and connexin36-based electrical synapses.\",\n      \"evidence\": \"Lnx1 knockout mice with mossy fiber tracing, Co-IP of EphB/NMDAR complexes, receptor internalization assays, connexin36 gap junction loss with ligase-active vs. inactive LNX\",\n      \"pmids\": [\"30185604\", \"30295974\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether the scaffold and E3 functions operate simultaneously on the same complex was unclear\", \"The triggering signals for LNX1-mediated Cx36 ubiquitination were not identified\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"The scaffold function was linked to behavior: Lnx1 deficiency disrupts the LNX1–NMDAR–EphB2 complex in hippocampal CA3, causing NMDAR hypofunction, impaired neuronal activity, and social memory deficits that are rescued by region-specific Lnx1 or EphB2 restoration.\",\n      \"evidence\": \"Lnx1 KO mice, PSD fractionation, stereotaxic viral rescue of CA3, electrophysiology, social recognition assay\",\n      \"pmids\": [\"31772302\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether human LNX1 variants associate with social cognition phenotypes was not tested\", \"Contribution of LNX1p70 vs. LNX1p80 to the synaptic complex was not dissected\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"LNX1's substrate range was extended to tumor suppressor pathways: LNX1 interacts with p53 and MDM2, enhances MDM2-dependent p53 ubiquitination, and LNX1 knockout stabilizes p53, suppressing xenograft tumor growth.\",\n      \"evidence\": \"CRISPR-Cas9 KO and lentiviral OE in cancer cells, Co-IP, ubiquitination assay, p53 half-life measurement, mouse xenograft\",\n      \"pmids\": [\"31533005\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether LNX1 directly ubiquitinates p53 or only facilitates MDM2-dependent ubiquitination was not fully resolved\", \"Physiological relevance outside cancer cell lines was not examined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"A non-degradative ubiquitination function was defined: LNX1 performs non-degrading ubiquitination of RhoC (but not RhoA) to promote RhoC activity, with LIS1 acting as a negative regulator of this process, revealing isoform-specific Rho regulation.\",\n      \"evidence\": \"In vitro ubiquitination, RhoGDI interaction assay, RhoC activity assay, LIS1 OE/KD\",\n      \"pmids\": [\"36192543\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The ubiquitin chain type on RhoC was not identified\", \"In vivo validation of the LIS1–LNX1–RhoC axis was not performed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Behavioral dissection of single and double LNX knockouts clarified isoform-specific roles: neuronal LNX1p70 functions as a stabilizing scaffold for shared partners while LNX2 promotes their degradation, and Lnx1 loss specifically affects anxiety behavior, body weight, and pup ultrasonic vocalizations.\",\n      \"evidence\": \"Single and double LNX1/LNX2 KO mice, comprehensive behavioral battery, body weight analysis\",\n      \"pmids\": [\"40269869\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular substrates driving anxiety and vocalization phenotypes were not identified\", \"Whether LNX1 scaffold and LNX2 E3 functions are competitive or complementary at the same synapse remains untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Major unresolved questions include how LNX1 E3 ligase and scaffold functions are coordinated at individual synapses, which substrates drive the behavioral phenotypes observed in knockout mice, and whether LNX1 variants contribute to human neurodevelopmental or psychiatric conditions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No human genetic association studies for LNX1 have been reported\", \"Chain-type specificity across different substrates is incompletely characterized\", \"Structural basis of PDZ domain substrate selection is lacking\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [3, 8, 14, 17, 18, 19, 21, 23, 25, 29]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [17, 20, 24, 31, 32]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [20, 24, 31]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [9, 15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0162582\", \"supporting_discovery_ids\": [3, 26, 27, 30]},\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [3, 14, 17, 18, 23, 25, 29]},\n      {\"term_id\": \"R-HSA-112316\", \"supporting_discovery_ids\": [19, 20, 24, 31]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [8, 10, 26]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [14, 28]}\n    ],\n    \"complexes\": [\n      \"LNX1-NMDAR-EphB2 postsynaptic complex\"\n    ],\n    \"partners\": [\n      \"NUMB\",\n      \"EPHB2\",\n      \"EPHB1\",\n      \"PPFIA1\",\n      \"GJD2\",\n      \"UBE2N\",\n      \"ERBB2\",\n      \"MDM2\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}