{"gene":"FBXO45","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":2009,"finding":"FBXO45 does not form a canonical SCF complex due to an amino acid substitution in the consensus sequence for Cul1 binding; instead, it specifically associates with PAM/Phr1 (a RING finger-type ubiquitin ligase) to form a novel Fbxo45-PAM ubiquitin ligase complex required for neural development, including innervation of the diaphragm, synapse formation at neuromuscular junctions, axon fiber tract development, and neuronal migration.","method":"Proteomics/mass spectrometry, knockout mice, genetic epistasis (Fbxo45-/- and Phr1-/- phenotype comparison)","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal proteomics, knockout mouse model with defined phenotypes, genetic epistasis between Fbxo45 and Phr1 replicated across two mouse models","pmids":["19398581"],"is_preprint":false},{"year":2009,"finding":"FBXO45 (human ortholog of C. elegans FSN-1) binds specifically to p73 and triggers its proteasome-dependent degradation via SCF(FBXO45)-mediated ubiquitylation both in vivo and in vitro; siRNA-mediated depletion of FBXO45 stabilizes p73 and induces p53-independent cell death.","method":"Co-immunoprecipitation, in vitro ubiquitylation assay, siRNA knockdown, proteasome inhibitor rescue","journal":"Oncogene","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro ubiquitylation assay plus in vivo co-IP and functional knockdown, single lab with multiple orthogonal methods","pmids":["19581926"],"is_preprint":false},{"year":2009,"finding":"Fbxo45 induces ubiquitin-mediated proteasomal degradation of the synaptic vesicle-priming factor Munc13-1 at synapses; knockdown of Fbxo45 in primary cultured hippocampal neurons increases the frequency of miniature excitatory postsynaptic currents.","method":"RNAi knockdown, electrophysiology (mEPSC recording), ubiquitination assay, Western blot","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — electrophysiological readout combined with ubiquitination assay and RNAi, single lab with multiple orthogonal methods","pmids":["19996097"],"is_preprint":false},{"year":2014,"finding":"Fbxo45 interacts with Par-4 (tumor suppressor) through its SPRY domain via a short consensus sequence motif in the cytoplasm, mediating Par-4 ubiquitylation and proteasomal degradation; Fbxo45 silencing stabilizes Par-4 and increases apoptosis, while a Par-4 mutant unable to bind Fbxo45 is stabilized and enhances staurosporine-induced apoptosis.","method":"Immunopurification, mass spectrometry, co-immunoprecipitation, ubiquitination assay, RNAi knockdown, site-directed mutagenesis, apoptosis assay","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — unbiased MS identification, domain mutagenesis, ubiquitination assay, and functional readout in single lab","pmids":["24992930"],"is_preprint":false},{"year":2014,"finding":"Fbxo45 interacts with N-cadherin; Fbxo45 depletion results in enhanced proteolysis of N-cadherin (not ubiquitination-mediated degradation), while ectopic Fbxo45 expression decreases N-cadherin proteolysis, and Fbxo45 depletion impairs neuronal differentiation and neuronal process formation.","method":"Mass spectrometry-based proteomic screen, co-immunoprecipitation, RNAi knockdown, ectopic overexpression, Western blot, neuronal differentiation assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — proteomics-identified interaction confirmed by Co-IP, functional readout, single lab","pmids":["25143387"],"is_preprint":false},{"year":2015,"finding":"The atypical Skp1-Pam-Fbxo45 (SPF) E3 ligase complex promotes ubiquitin-proteasome-dependent degradation of core EMT transcription factors (Zeb1/2, Snai1/2, Twist1); Fbxo45 recognizes Zeb2 via its SPRY domain and Snai1, Snai2, and Twist1 via its F-box domain; K48-linked ubiquitination of Zeb2 requires a functional SBD domain; miR-27a* downregulates Fbxo45 expression, preventing EMT-TF degradation.","method":"Co-immunoprecipitation, ubiquitination assay, domain mutagenesis, miRNA overexpression, Western blot","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — domain mutagenesis identifying SPRY vs F-box substrate specificity, ubiquitination assay, single lab","pmids":["25460509"],"is_preprint":false},{"year":2015,"finding":"Hey1 directly interacts with FBXO45 and indirectly with SKP1 via FBXO45; Hey1 expression induces translocation of FBXO45 and PAM into the nucleus, potentially redirecting the ubiquitin ligase complex to nuclear targets; no evidence for FBXO45-dependent ubiquitination of Hey1 itself.","method":"Tandem affinity purification, mass spectrometry, co-immunoprecipitation, subcellular fractionation/localization, overexpression","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — TAP-MS identification confirmed by Co-IP, nuclear translocation demonstrated by localization experiment, single lab","pmids":["26068074"],"is_preprint":false},{"year":2018,"finding":"Spinal TNF-α impedes Fbxo45-dependent Munc13-1 ubiquitination in the dorsal horn; neuropathic injury decreases spinal Fbxo45 expression, Fbxo45-Munc13-1 co-precipitation, and Munc13-1 ubiquitination, leading to accumulation of Munc13-1 at presynaptic areas and increased excitatory neurotransmission; focal knockdown of spinal Fbxo45 in naive animals produces allodynia.","method":"Rat behavioral model, co-immunoprecipitation, ubiquitination assay, electrophysiology (mEPSC), TNF-α intrathecal injection, siRNA knockdown","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo mechanistic dissection with co-IP, ubiquitination, electrophysiology, and cytokine intervention, single lab","pmids":["30042425"],"is_preprint":false},{"year":2019,"finding":"FBXO45-MYCBP2 E3 ubiquitin ligase targets FBXW7 for ubiquitylation and proteasomal degradation specifically during prolonged mitotic arrest; FBXO45 binds a conserved acidic N-terminal motif of FBXW7; this interaction promotes mitotic slippage and prevents mitotic cell death, thereby counteracting FBXW7 tumor suppressor function.","method":"Co-immunoprecipitation, ubiquitination assay, time-lapse microscopy, RNAi, site-directed mutagenesis of FBXW7 motif","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, ubiquitination assay, motif mutagenesis, live-cell imaging, single lab with multiple orthogonal methods","pmids":["31285543"],"is_preprint":false},{"year":2020,"finding":"Fbxo45 binds SPRY motifs in the extracellular domain of N-cadherin (not involved in homophilic cell-cell adhesion); Fbxo45 appears to be secreted by a nonclassical mechanism independent of ER-to-Golgi transport; both Fbxo45 suppression and N-cadherin SPRY-motif mutation inhibit radial neuron migration in vivo.","method":"Proximity ligation, affinity purification proteomics, in utero electroporation/in vivo migration assay, SPRY-motif mutagenesis of N-cadherin, nonclassical secretion analysis","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 / Moderate — dual proteomic screens, in vivo functional validation with SPRY-motif mutagenesis, localization/secretion mechanism, single lab with multiple orthogonal methods","pmids":["32341084"],"is_preprint":false},{"year":2021,"finding":"FBXO45 promotes IGF2BP1 ubiquitination at Lys190 and Lys450 sites, leading to IGF2BP1 activation and subsequent upregulation of PLK1 expression, inducing cell proliferation and liver tumorigenesis; PLK1 inhibition or IGF2BP1 knockdown blocks FBXO45-driven tumorigenesis.","method":"Co-immunoprecipitation, ubiquitination assay with site-specific mutagenesis (Lys190/450), transgenic mice, in vitro and in vivo functional assays, IHC","journal":"eLife","confidence":"High","confidence_rationale":"Tier 2 / Moderate — site-specific ubiquitination mutagenesis, transgenic mouse model with epistasis rescue, multiple orthogonal methods, single lab","pmids":["34779401"],"is_preprint":false},{"year":2021,"finding":"DNAJB9 stabilizes FBXO45 protein by suppressing FBXO45 self-ubiquitination; stabilized FBXO45 promotes Lys48-linked polyubiquitination of ZEB1, leading to its degradation and inhibition of EMT.","method":"Co-immunoprecipitation, ubiquitination assay, overexpression/knockdown, in vivo metastasis assay","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitination assay confirming K48 linkage, co-IP, in vivo validation, single lab","pmids":["33966034"],"is_preprint":false},{"year":2022,"finding":"Fbxo45 binds to USP49 via its SPRY domain and, enhanced by NEK6 kinase, mediates USP49 ubiquitination and proteasomal degradation, thereby promoting pancreatic cancer cell viability and motility.","method":"Co-immunoprecipitation, ubiquitination assay, kinase (NEK6) co-expression, RNAi knockdown, xenograft mouse model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP, ubiquitination assay, kinase enhancement, in vivo validation, single lab","pmids":["35279684"],"is_preprint":false},{"year":2022,"finding":"FBXO45 induces K6-linked polyubiquitination of NP-STEP46 (active form of STEP phosphatase), leading to its proteasomal degradation in the nucleus, thereby sustaining phospho-ERK levels and promoting NSCLC tumor growth; FBXO45 silencing sensitizes cells to EGFR-TKI.","method":"In vitro and in vivo ubiquitination assay (K6 linkage-specific), co-immunoprecipitation, RNAi, xenograft model, ERK phosphorylation measurement","journal":"Molecular oncology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — linkage-specific ubiquitination assay, co-IP, in vivo validation, single lab","pmids":["35838331"],"is_preprint":false},{"year":2022,"finding":"Fbxo45 binds GGNBP2 via its SPRY domain and targets it for ubiquitination and proteasomal degradation in esophageal squamous cell carcinoma cells, promoting tumor growth and invasion.","method":"Co-immunoprecipitation, ubiquitination assay, domain analysis (SPRY), RNAi knockdown, overexpression, xenograft mouse model","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP with domain-level analysis, ubiquitination assay, in vivo validation, single lab","pmids":["36127399"],"is_preprint":false},{"year":2022,"finding":"FBXO45 binds IFNLR1 (IFN-λ receptor) intracellular domain and mediates its polyubiquitination and proteasomal degradation; K319R/K320R IFNLR1 mutant shows reduced polyubiquitination and greater stability; FBXO45 expression is induced by influenza infection and negatively regulates interferon-stimulated gene expression.","method":"Proximity ligation biotin screen, co-immunoprecipitation, ubiquitination assay, site-directed mutagenesis (K319R/K320R), siRNA knockdown, overexpression","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — unbiased proximal ligation screen, mutagenesis of ubiquitination sites, ubiquitination assay, functional ISG readout, single lab with multiple orthogonal methods","pmids":["36379255"],"is_preprint":false},{"year":2022,"finding":"RBX1 directly binds FBXO45 and promotes its ubiquitination and degradation; this destabilization of FBXO45 leads to accumulation of TWIST1 and enhanced EMT/metastasis in triple-negative breast cancer.","method":"Co-immunoprecipitation, ubiquitination assay, RNAi knockdown, overexpression","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — co-IP and ubiquitination assay, single lab, limited methodological detail in abstract","pmids":["35802537"],"is_preprint":false},{"year":2024,"finding":"FBXO45 is a cell-cycle-regulated protein degraded upon CDK1-mediated phosphorylation during S/G2 phase; during S phase or DNA damage repair, FBXO45 binds UPF1 and recruits the phosphatase PPP6C to inhibit UPF1 phosphorylation, thereby preventing degradation of replication-dependent histone mRNAs and ensuring adequate histone supply; loss of FBXO45 in AT2 cells causes UPF1 hyperphosphorylation, histone insufficiency, genomic instability, and spontaneous lung adenocarcinoma in mice.","method":"Conditional knockout mice (AT2-specific), co-immunoprecipitation (FBXO45-UPF1-PPP6C), phosphorylation assays, histone mRNA stability assays, CDK1 kinase assay, genomic instability analysis","journal":"Cell death and differentiation","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (KO mouse, co-IP of ternary complex, kinase-mediated degradation, mRNA stability, spontaneous tumorigenesis), single lab","pmids":["39672818"],"is_preprint":false},{"year":2024,"finding":"FBXO45 interacts with BIM and mediates its ubiquitination and proteasomal degradation; knockdown of FBXO45 inhibits breast cancer cell proliferation via BIM pathway stabilization and induces apoptosis.","method":"Co-immunoprecipitation, ubiquitination assay, cycloheximide chase assay, RNAi knockdown, overexpression, xenograft model","journal":"BMC cancer","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — co-IP, ubiquitination and CHX chase assays, in vivo validation, single lab","pmids":["38773471"],"is_preprint":false},{"year":2025,"finding":"FBXO45 mediates ubiquitination of HIV-1 Tat (requiring Tat phosphorylation at S62), directing it to SQSTM1/p62-dependent autophagic degradation; FBXO45 suppresses HIV-1 replication and maintains viral latency; FBXO45 overexpression attenuates viral rebound after antiretroviral therapy withdrawal.","method":"TurboID proximity labeling, co-immunoprecipitation, ubiquitination assay, site-directed mutagenesis (S62A Tat, autophagy pathway), HIV-1 replication assay, siRNA knockdown","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — TurboID-identified interaction, mutagenesis of phosphorylation/ubiquitination sites, autophagic degradation mechanistic dissection, single lab","pmids":["39936917"],"is_preprint":false},{"year":2025,"finding":"SETD7 promotes p53 mono-methylation which activates FBXO45 transcription; FBXO45 then mediates proteasomal degradation of GPX4, leading to lipid peroxidation and oxidative stress-induced endothelial dysfunction; SETD7 deficiency reduces FBXO45 transcription, inhibiting GPX4 degradation.","method":"SETD7 knockout mice, endothelial-specific AAV knockdown, co-immunoprecipitation, Western blot, lipid peroxidation assay, glucose-stressed endothelial cells","journal":"Cardiovascular diabetology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo mouse model with multiple cell contexts, mechanistic pathway placement (SETD7-p53-FBXO45-GPX4), single lab","pmids":["40275362"],"is_preprint":false},{"year":2025,"finding":"FBXO45 promotes Lys103 ubiquitination of TFG (Trk-fused gene), enhancing TFG stability; stabilized TFG facilitates binding of ATF2 transcription factor, upregulating NF-κB p65 expression and promoting migration, invasion, and lung metastasis of TP53-mutant HCC cells.","method":"Co-immunoprecipitation, ubiquitination assay with site-specific mutagenesis (Lys103), orthotopic xenograft model, ATF2/NF-κB reporter assays, siRNA knockdown, overexpression","journal":"JHEP reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — site-specific ubiquitination mutagenesis, downstream transcription factor activation, orthotopic in vivo model, single lab","pmids":["41030651"],"is_preprint":false},{"year":2025,"finding":"FBXO45 interacts with and ubiquitinates DUSP2, leading to its proteasomal degradation, ERK1/2 activation, and enhanced glycolysis in cervical cancer cells.","method":"Co-immunoprecipitation, ubiquitination assay, overexpression/knockdown, Seahorse metabolic assay, xenograft model","journal":"Naunyn-Schmiedeberg's archives of pharmacology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — co-IP and ubiquitination assay, single lab, no mutagenesis or domain mapping reported in abstract","pmids":["40637745"],"is_preprint":false},{"year":2025,"finding":"FBXO45 promotes ubiquitination and degradation of Erbin in clear cell renal cell carcinoma, enhancing cell viability, motility, and sunitinib resistance; Fbxo45 expression is negatively correlated with Erbin expression in ccRCC.","method":"Co-immunoprecipitation (implied by negative correlation and functional rescue), overexpression/knockdown, xenograft model, sunitinib sensitivity assay","journal":"Experimental cell research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — functional evidence and co-expression data, limited mechanistic detail in abstract, single lab","pmids":["41285235"],"is_preprint":false}],"current_model":"FBXO45 is an atypical F-box protein that does not form canonical SCF complexes (due to substitution in the Cul1-binding sequence) but instead partners with PAM/MycBP2 (RING finger E3) and SKP1 to form the SPF (Skp1-Pam-Fbxo45) ubiquitin ligase complex, which targets a diverse array of substrates—including Munc13-1, p73, Par-4, FBXW7, IGF2BP1, EMT transcription factors, USP49, GGNBP2, IFNLR1, TFG, GPX4, BIM, DUSP2, NP-STEP46, and HIV-1 Tat—for ubiquitylation and proteasomal or autophagic degradation; in the nervous system FBXO45 is essential for synapse formation, neuromuscular junction development, and neuronal migration (partly through regulating N-cadherin proteolysis and extracellular SPRY-domain binding), while in dividing cells it is CDK1-phosphorylated for cell-cycle-regulated degradation and participates in histone mRNA stability via a FBXO45-UPF1-PPP6C complex, collectively placing FBXO45 as a context-dependent E3 ligase adaptor with critical roles in neural development, mitotic fate decisions, genomic integrity, innate immunity, and cancer progression."},"narrative":{"mechanistic_narrative":"FBXO45 is an atypical F-box protein that operates as the substrate-recognition adaptor of a non-canonical ubiquitin ligase: a substitution in its Cul1-binding sequence precludes formation of a classical SCF complex, and instead FBXO45 associates with the RING-finger ligase PAM/MycBP2 (and SKP1) to assemble an E3 complex essential for neural development, including diaphragm innervation, neuromuscular junction synapse formation, axon tract development, and neuronal migration [PMID:19398581]. The protein recognizes substrates through two distinct modules—its SPRY domain and its F-box domain—allowing it to engage a broad substrate repertoire [PMID:25460509]. In the nervous system it controls synaptic strength by ubiquitylating the vesicle-priming factor Munc13-1 [PMID:19996097] and guides radial neuron migration by binding SPRY motifs in the extracellular domain of N-cadherin via a nonclassical secretion route [PMID:32341084]. FBXO45 directs substrates to proteasomal degradation through diverse ubiquitin linkages, including K48-linked chains on EMT transcription factors such as ZEB1 [PMID:33966034] and K6-linked chains on the STEP phosphatase NP-STEP46 [PMID:35838331], and can also route substrates to p62/SQSTM1-dependent autophagy, as for phosphorylated HIV-1 Tat [PMID:39936917]. Through degradation of tumor suppressors and apoptotic regulators—p73 [PMID:19581926], Par-4 [PMID:24992930], FBXW7 during mitotic arrest [PMID:31285543], and BIM [PMID:38773471]—and activation of oncogenic effectors such as IGF2BP1 [PMID:34779401], FBXO45 functions as a context-dependent regulator of apoptosis, mitotic fate, and tumor progression. It additionally maintains genomic integrity by forming an FBXO45-UPF1-PPP6C complex that stabilizes replication-dependent histone mRNAs, with its own abundance gated by CDK1-mediated phosphorylation for cell-cycle-regulated turnover [PMID:39672818].","teleology":[{"year":2009,"claim":"Established that FBXO45 is not a canonical SCF adaptor but instead partners with the RING ligase PAM/Phr1, defining the architecture of a novel E3 complex required for nervous system development.","evidence":"Proteomics, knockout mice, and Fbxo45/Phr1 genetic epistasis","pmids":["19398581"],"confidence":"High","gaps":["Did not enumerate the developmental substrates degraded by the complex","Cul1-independence shown but the full subunit composition of the active ligase not biochemically reconstituted"]},{"year":2009,"claim":"Identified the first defined degradation substrates, showing FBXO45 controls apoptotic/tumor-suppressor output (p73) and synaptic transmission (Munc13-1) through ubiquitin-proteasome targeting.","evidence":"Co-IP, in vitro ubiquitylation, siRNA, and mEPSC electrophysiology in neurons","pmids":["19581926","19996097"],"confidence":"High","gaps":["Recognition motifs on p73 and Munc13-1 not mapped","Whether degradation requires PAM/MycBP2 catalytic activity not tested in these reports"]},{"year":2014,"claim":"Revealed the SPRY domain as a substrate-docking module and uncovered a non-degradative N-cadherin function, broadening FBXO45 roles beyond proteasomal turnover.","evidence":"MS screens, SPRY consensus-motif identification for Par-4, Co-IP and proteolysis assays for N-cadherin","pmids":["24992930","25143387"],"confidence":"High","gaps":["Mechanism by which FBXO45 limits N-cadherin proteolysis without ubiquitinating it unclear","Relative contributions of SPRY vs F-box recognition not yet generalized"]},{"year":2015,"claim":"Defined dual substrate-recognition logic and named the SPF complex, linking FBXO45 to EMT control by degrading core EMT transcription factors via distinct domains.","evidence":"Co-IP, ubiquitination assays, domain mutagenesis (SPRY for Zeb2, F-box for Snai1/2/Twist1), miR-27a* regulation; TAP-MS Hey1 interaction and nuclear redirection","pmids":["25460509","26068074"],"confidence":"Medium","gaps":["Hey1-driven nuclear relocalization not connected to specific nuclear substrates","In vivo relevance of EMT-TF degradation not tested here"]},{"year":2018,"claim":"Connected FBXO45 substrate targeting to physiological signaling by showing inflammatory TNF-α suppresses Fbxo45-mediated Munc13-1 turnover to drive pain.","evidence":"Rat neuropathic model, Co-IP, ubiquitination, mEPSC, intrathecal TNF-α and siRNA","pmids":["30042425"],"confidence":"Medium","gaps":["Molecular link between TNF-α signaling and reduced Fbxo45 activity not resolved","Single in vivo model"]},{"year":2019,"claim":"Placed FBXO45 in mitotic fate control by demonstrating it degrades the tumor suppressor FBXW7 during prolonged mitotic arrest to promote slippage and survival.","evidence":"Reciprocal Co-IP, ubiquitination, FBXW7 motif mutagenesis, time-lapse imaging","pmids":["31285543"],"confidence":"High","gaps":["Trigger restricting this activity to mitotic arrest not defined","Whether MYCBP2 catalysis is rate-limiting not tested"]},{"year":2021,"claim":"Expanded FBXO45 outputs to non-degradative activation and revealed regulation of its own stability, with IGF2BP1 site-specific ubiquitination driving tumorigenesis and DNAJB9 suppressing FBXO45 auto-ubiquitination.","evidence":"Site-specific ubiquitination mutagenesis (IGF2BP1 K190/K450), transgenic mice, K48 ubiquitination assays for ZEB1, in vivo metastasis","pmids":["34779401","33966034"],"confidence":"Medium","gaps":["How a single adaptor produces activating vs degradative ubiquitination not mechanistically unified","Auto-ubiquitination regulators beyond DNAJB9 unknown"]},{"year":2022,"claim":"Demonstrated diverse linkage chemistry and broad substrate scope across cancers and innate immunity, including K6-linked NP-STEP46 degradation and IFNLR1 turnover that dampens interferon signaling.","evidence":"Linkage-specific ubiquitination assays, site mutagenesis (IFNLR1 K319/K320R), proximity-ligation screens, kinase enhancement (NEK6), xenografts for USP49/GGNBP2; RBX1-driven FBXO45 destabilization","pmids":["35279684","35838331","36127399","36379255","35802537"],"confidence":"Medium","gaps":["Determinants selecting K6 vs K48 linkage not defined","How kinases like NEK6 and ligases like RBX1 are integrated with the SPF complex remains incomplete"]},{"year":2024,"claim":"Identified a non-ligase scaffolding function in genome maintenance and clarified cell-cycle control of FBXO45 itself, with the FBXO45-UPF1-PPP6C complex protecting histone mRNAs and CDK1 phosphorylation gating FBXO45 degradation.","evidence":"AT2-specific conditional knockout mice, ternary-complex Co-IP, CDK1 kinase and phosphatase assays, histone mRNA stability, spontaneous tumorigenesis; BIM degradation Co-IP/CHX in breast cancer","pmids":["39672818","38773471"],"confidence":"High","gaps":["How FBXO45 switches between ligase-adaptor and PPP6C-scaffold roles is unresolved","Structural basis of the UPF1-PPP6C ternary complex unknown"]},{"year":2025,"claim":"Extended FBXO45 to autophagic substrate routing, transcriptional pathway placement, and additional disease contexts, including p62-dependent degradation of HIV-1 Tat and SETD7-p53-driven FBXO45 transcription degrading GPX4.","evidence":"TurboID, autophagy-pathway mutagenesis (Tat S62A), SETD7 knockout mice, site-specific ubiquitination (TFG K103), metabolic and xenograft assays for DUSP2/Erbin","pmids":["39936917","40275362","41030651","40637745","41285235"],"confidence":"Medium","gaps":["What dictates proteasomal vs autophagic routing of FBXO45 substrates is undefined","DUSP2 and Erbin findings lack domain/site mapping"]},{"year":null,"claim":"It remains unresolved how a single adaptor integrates SPRY- versus F-box-based recognition, selects among ubiquitin linkage types and degradation routes (proteasome vs autophagy), and toggles between E3-adaptor and non-catalytic scaffold roles.","evidence":"No reconstitution or structural study in the timeline resolves these selectivity rules","pmids":[],"confidence":"Low","gaps":["No structure of FBXO45 bound to PAM/MycBP2-SKP1 or substrates","No unifying model linking substrate identity to linkage type and degradation pathway"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,3,8,10,15,17]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[0,5,17]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[4,9,17]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[3]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[6,13,17]},{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[9]}],"pathway":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,3,8]}],"complexes":["SPF (Skp1-Pam-Fbxo45) ubiquitin ligase complex","FBXO45-MYCBP2/PAM E3 ligase","FBXO45-UPF1-PPP6C complex"],"partners":["MYCBP2","SKP1","FBXW7","UPF1","PPP6C","IGF2BP1","N-CADHERIN","USP49"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P0C2W1","full_name":"F-box/SPRY domain-containing protein 1","aliases":["F-box only protein 45","hFbxo45"],"length_aa":286,"mass_kda":30.6,"function":"Component of E3 ubiquitin ligase complex consisting of FBXO45, MYCBP2 and SKP1 (PubMed:29997255). Functions in substrate recognition but also plays an important role in assembly of the complex (PubMed:29997255). Required for normal neuromuscular synaptogenesis, axon pathfinding and neuronal migration (By similarity). Regulates neuron migration during brain development through interaction with N-cadherin/CDH2 after secretion via a non-classical mechanism (By similarity). Plays a role in the regulation of neurotransmission at mature neurons (By similarity). May control synaptic activity by controlling UNC13A via ubiquitin dependent pathway (By similarity). Specifically recognizes TP73, promoting its ubiquitination and degradation. Polyubiquitinates NMNAT2, an adenylyltransferase that acts as an axon maintenance factor, and regulates its stability and degradation by the proteasome (PubMed:29997255). Also acts by ubiquitinating FBXW7 during prolonged mitotic arrest and promotes FBXW7 proteasomal degradation (PubMed:31285543). Induces subsequently an increase in mitotic slippage and prevents mitotic cell death (PubMed:31285543). In response to influenza infection, mediates interferon-lambda receptor IFNLR1 polyubiquitination and degradation through the ubiquitin-proteasome system by docking with its intracellular receptor domain (PubMed:36379255)","subcellular_location":"Secreted; Postsynaptic cell membrane; Presynaptic cell membrane; Nucleus","url":"https://www.uniprot.org/uniprotkb/P0C2W1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/FBXO45","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"CALM1","stoichiometry":0.2},{"gene":"VCP","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/FBXO45","total_profiled":1310},"omim":[{"mim_id":"609425","title":"CHROMOSOME 3q29 DELETION SYNDROME","url":"https://www.omim.org/entry/609425"},{"mim_id":"609112","title":"F-BOX ONLY PROTEIN 45; FBXO45","url":"https://www.omim.org/entry/609112"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Plasma membrane","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"},{"location":"Vesicles","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/FBXO45"},"hgnc":{"alias_symbol":["Fbx45"],"prev_symbol":[]},"alphafold":{"accession":"P0C2W1","domains":[{"cath_id":"-","chopping":"40-86","consensus_level":"medium","plddt":95.2781,"start":40,"end":86},{"cath_id":"2.60.120.920","chopping":"115-280","consensus_level":"high","plddt":96.3751,"start":115,"end":280}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P0C2W1","model_url":"https://alphafold.ebi.ac.uk/files/AF-P0C2W1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P0C2W1-F1-predicted_aligned_error_v6.png","plddt_mean":88.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=FBXO45","jax_strain_url":"https://www.jax.org/strain/search?query=FBXO45"},"sequence":{"accession":"P0C2W1","fasta_url":"https://rest.uniprot.org/uniprotkb/P0C2W1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P0C2W1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P0C2W1"}},"corpus_meta":[{"pmid":"19398581","id":"PMC_19398581","title":"Fbxo45 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Knockdown Restrains the Progression of Bladder Cancer via the ERK/Cyclin D1/CDK4 Pathway.","date":"2024","source":"Archivos espanoles de urologia","url":"https://pubmed.ncbi.nlm.nih.gov/39238305","citation_count":1,"is_preprint":false},{"pmid":"41285235","id":"PMC_41285235","title":"Fbxo45 promotes cell viability, invasion and sunitinib resistance of clear cell renal cell carcinoma by targeting Erbin.","date":"2025","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/41285235","citation_count":1,"is_preprint":false},{"pmid":"41030651","id":"PMC_41030651","title":"Elevated FBXO45 promotes TFG ubiquitination and drives lung metastasis of hepatocellular carcinoma.","date":"2025","source":"JHEP reports : innovation in hepatology","url":"https://pubmed.ncbi.nlm.nih.gov/41030651","citation_count":0,"is_preprint":false},{"pmid":"40637745","id":"PMC_40637745","title":"FBXO45 enhances cell viability and glycolysis in cervical cancer via DUSP2 ubiquitination-mediated 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  \"finding\": \"FBXO45 does not form a canonical SCF complex due to an amino acid substitution in the consensus sequence for Cul1 binding; instead, it specifically associates with PAM/Phr1 (a RING finger-type ubiquitin ligase) to form a novel Fbxo45-PAM ubiquitin ligase complex required for neural development, including innervation of the diaphragm, synapse formation at neuromuscular junctions, axon fiber tract development, and neuronal migration.\",\n      \"method\": \"Proteomics/mass spectrometry, knockout mice, genetic epistasis (Fbxo45-/- and Phr1-/- phenotype comparison)\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal proteomics, knockout mouse model with defined phenotypes, genetic epistasis between Fbxo45 and Phr1 replicated across two mouse models\",\n      \"pmids\": [\"19398581\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"FBXO45 (human ortholog of C. elegans FSN-1) binds specifically to p73 and triggers its proteasome-dependent degradation via SCF(FBXO45)-mediated ubiquitylation both in vivo and in vitro; siRNA-mediated depletion of FBXO45 stabilizes p73 and induces p53-independent cell death.\",\n      \"method\": \"Co-immunoprecipitation, in vitro ubiquitylation assay, siRNA knockdown, proteasome inhibitor rescue\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro ubiquitylation assay plus in vivo co-IP and functional knockdown, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"19581926\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Fbxo45 induces ubiquitin-mediated proteasomal degradation of the synaptic vesicle-priming factor Munc13-1 at synapses; knockdown of Fbxo45 in primary cultured hippocampal neurons increases the frequency of miniature excitatory postsynaptic currents.\",\n      \"method\": \"RNAi knockdown, electrophysiology (mEPSC recording), ubiquitination assay, Western blot\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — electrophysiological readout combined with ubiquitination assay and RNAi, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"19996097\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Fbxo45 interacts with Par-4 (tumor suppressor) through its SPRY domain via a short consensus sequence motif in the cytoplasm, mediating Par-4 ubiquitylation and proteasomal degradation; Fbxo45 silencing stabilizes Par-4 and increases apoptosis, while a Par-4 mutant unable to bind Fbxo45 is stabilized and enhances staurosporine-induced apoptosis.\",\n      \"method\": \"Immunopurification, mass spectrometry, co-immunoprecipitation, ubiquitination assay, RNAi knockdown, site-directed mutagenesis, apoptosis assay\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — unbiased MS identification, domain mutagenesis, ubiquitination assay, and functional readout in single lab\",\n      \"pmids\": [\"24992930\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Fbxo45 interacts with N-cadherin; Fbxo45 depletion results in enhanced proteolysis of N-cadherin (not ubiquitination-mediated degradation), while ectopic Fbxo45 expression decreases N-cadherin proteolysis, and Fbxo45 depletion impairs neuronal differentiation and neuronal process formation.\",\n      \"method\": \"Mass spectrometry-based proteomic screen, co-immunoprecipitation, RNAi knockdown, ectopic overexpression, Western blot, neuronal differentiation assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — proteomics-identified interaction confirmed by Co-IP, functional readout, single lab\",\n      \"pmids\": [\"25143387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"The atypical Skp1-Pam-Fbxo45 (SPF) E3 ligase complex promotes ubiquitin-proteasome-dependent degradation of core EMT transcription factors (Zeb1/2, Snai1/2, Twist1); Fbxo45 recognizes Zeb2 via its SPRY domain and Snai1, Snai2, and Twist1 via its F-box domain; K48-linked ubiquitination of Zeb2 requires a functional SBD domain; miR-27a* downregulates Fbxo45 expression, preventing EMT-TF degradation.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, domain mutagenesis, miRNA overexpression, Western blot\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — domain mutagenesis identifying SPRY vs F-box substrate specificity, ubiquitination assay, single lab\",\n      \"pmids\": [\"25460509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Hey1 directly interacts with FBXO45 and indirectly with SKP1 via FBXO45; Hey1 expression induces translocation of FBXO45 and PAM into the nucleus, potentially redirecting the ubiquitin ligase complex to nuclear targets; no evidence for FBXO45-dependent ubiquitination of Hey1 itself.\",\n      \"method\": \"Tandem affinity purification, mass spectrometry, co-immunoprecipitation, subcellular fractionation/localization, overexpression\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — TAP-MS identification confirmed by Co-IP, nuclear translocation demonstrated by localization experiment, single lab\",\n      \"pmids\": [\"26068074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Spinal TNF-α impedes Fbxo45-dependent Munc13-1 ubiquitination in the dorsal horn; neuropathic injury decreases spinal Fbxo45 expression, Fbxo45-Munc13-1 co-precipitation, and Munc13-1 ubiquitination, leading to accumulation of Munc13-1 at presynaptic areas and increased excitatory neurotransmission; focal knockdown of spinal Fbxo45 in naive animals produces allodynia.\",\n      \"method\": \"Rat behavioral model, co-immunoprecipitation, ubiquitination assay, electrophysiology (mEPSC), TNF-α intrathecal injection, siRNA knockdown\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo mechanistic dissection with co-IP, ubiquitination, electrophysiology, and cytokine intervention, single lab\",\n      \"pmids\": [\"30042425\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FBXO45-MYCBP2 E3 ubiquitin ligase targets FBXW7 for ubiquitylation and proteasomal degradation specifically during prolonged mitotic arrest; FBXO45 binds a conserved acidic N-terminal motif of FBXW7; this interaction promotes mitotic slippage and prevents mitotic cell death, thereby counteracting FBXW7 tumor suppressor function.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, time-lapse microscopy, RNAi, site-directed mutagenesis of FBXW7 motif\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, ubiquitination assay, motif mutagenesis, live-cell imaging, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"31285543\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Fbxo45 binds SPRY motifs in the extracellular domain of N-cadherin (not involved in homophilic cell-cell adhesion); Fbxo45 appears to be secreted by a nonclassical mechanism independent of ER-to-Golgi transport; both Fbxo45 suppression and N-cadherin SPRY-motif mutation inhibit radial neuron migration in vivo.\",\n      \"method\": \"Proximity ligation, affinity purification proteomics, in utero electroporation/in vivo migration assay, SPRY-motif mutagenesis of N-cadherin, nonclassical secretion analysis\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — dual proteomic screens, in vivo functional validation with SPRY-motif mutagenesis, localization/secretion mechanism, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"32341084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"FBXO45 promotes IGF2BP1 ubiquitination at Lys190 and Lys450 sites, leading to IGF2BP1 activation and subsequent upregulation of PLK1 expression, inducing cell proliferation and liver tumorigenesis; PLK1 inhibition or IGF2BP1 knockdown blocks FBXO45-driven tumorigenesis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay with site-specific mutagenesis (Lys190/450), transgenic mice, in vitro and in vivo functional assays, IHC\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-specific ubiquitination mutagenesis, transgenic mouse model with epistasis rescue, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"34779401\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"DNAJB9 stabilizes FBXO45 protein by suppressing FBXO45 self-ubiquitination; stabilized FBXO45 promotes Lys48-linked polyubiquitination of ZEB1, leading to its degradation and inhibition of EMT.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, overexpression/knockdown, in vivo metastasis assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitination assay confirming K48 linkage, co-IP, in vivo validation, single lab\",\n      \"pmids\": [\"33966034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Fbxo45 binds to USP49 via its SPRY domain and, enhanced by NEK6 kinase, mediates USP49 ubiquitination and proteasomal degradation, thereby promoting pancreatic cancer cell viability and motility.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, kinase (NEK6) co-expression, RNAi knockdown, xenograft mouse model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP, ubiquitination assay, kinase enhancement, in vivo validation, single lab\",\n      \"pmids\": [\"35279684\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FBXO45 induces K6-linked polyubiquitination of NP-STEP46 (active form of STEP phosphatase), leading to its proteasomal degradation in the nucleus, thereby sustaining phospho-ERK levels and promoting NSCLC tumor growth; FBXO45 silencing sensitizes cells to EGFR-TKI.\",\n      \"method\": \"In vitro and in vivo ubiquitination assay (K6 linkage-specific), co-immunoprecipitation, RNAi, xenograft model, ERK phosphorylation measurement\",\n      \"journal\": \"Molecular oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — linkage-specific ubiquitination assay, co-IP, in vivo validation, single lab\",\n      \"pmids\": [\"35838331\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Fbxo45 binds GGNBP2 via its SPRY domain and targets it for ubiquitination and proteasomal degradation in esophageal squamous cell carcinoma cells, promoting tumor growth and invasion.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, domain analysis (SPRY), RNAi knockdown, overexpression, xenograft mouse model\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP with domain-level analysis, ubiquitination assay, in vivo validation, single lab\",\n      \"pmids\": [\"36127399\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"FBXO45 binds IFNLR1 (IFN-λ receptor) intracellular domain and mediates its polyubiquitination and proteasomal degradation; K319R/K320R IFNLR1 mutant shows reduced polyubiquitination and greater stability; FBXO45 expression is induced by influenza infection and negatively regulates interferon-stimulated gene expression.\",\n      \"method\": \"Proximity ligation biotin screen, co-immunoprecipitation, ubiquitination assay, site-directed mutagenesis (K319R/K320R), siRNA knockdown, overexpression\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — unbiased proximal ligation screen, mutagenesis of ubiquitination sites, ubiquitination assay, functional ISG readout, single lab with multiple orthogonal methods\",\n      \"pmids\": [\"36379255\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"RBX1 directly binds FBXO45 and promotes its ubiquitination and degradation; this destabilization of FBXO45 leads to accumulation of TWIST1 and enhanced EMT/metastasis in triple-negative breast cancer.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, RNAi knockdown, overexpression\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — co-IP and ubiquitination assay, single lab, limited methodological detail in abstract\",\n      \"pmids\": [\"35802537\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FBXO45 is a cell-cycle-regulated protein degraded upon CDK1-mediated phosphorylation during S/G2 phase; during S phase or DNA damage repair, FBXO45 binds UPF1 and recruits the phosphatase PPP6C to inhibit UPF1 phosphorylation, thereby preventing degradation of replication-dependent histone mRNAs and ensuring adequate histone supply; loss of FBXO45 in AT2 cells causes UPF1 hyperphosphorylation, histone insufficiency, genomic instability, and spontaneous lung adenocarcinoma in mice.\",\n      \"method\": \"Conditional knockout mice (AT2-specific), co-immunoprecipitation (FBXO45-UPF1-PPP6C), phosphorylation assays, histone mRNA stability assays, CDK1 kinase assay, genomic instability analysis\",\n      \"journal\": \"Cell death and differentiation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (KO mouse, co-IP of ternary complex, kinase-mediated degradation, mRNA stability, spontaneous tumorigenesis), single lab\",\n      \"pmids\": [\"39672818\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"FBXO45 interacts with BIM and mediates its ubiquitination and proteasomal degradation; knockdown of FBXO45 inhibits breast cancer cell proliferation via BIM pathway stabilization and induces apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, cycloheximide chase assay, RNAi knockdown, overexpression, xenograft model\",\n      \"journal\": \"BMC cancer\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — co-IP, ubiquitination and CHX chase assays, in vivo validation, single lab\",\n      \"pmids\": [\"38773471\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FBXO45 mediates ubiquitination of HIV-1 Tat (requiring Tat phosphorylation at S62), directing it to SQSTM1/p62-dependent autophagic degradation; FBXO45 suppresses HIV-1 replication and maintains viral latency; FBXO45 overexpression attenuates viral rebound after antiretroviral therapy withdrawal.\",\n      \"method\": \"TurboID proximity labeling, co-immunoprecipitation, ubiquitination assay, site-directed mutagenesis (S62A Tat, autophagy pathway), HIV-1 replication assay, siRNA knockdown\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — TurboID-identified interaction, mutagenesis of phosphorylation/ubiquitination sites, autophagic degradation mechanistic dissection, single lab\",\n      \"pmids\": [\"39936917\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SETD7 promotes p53 mono-methylation which activates FBXO45 transcription; FBXO45 then mediates proteasomal degradation of GPX4, leading to lipid peroxidation and oxidative stress-induced endothelial dysfunction; SETD7 deficiency reduces FBXO45 transcription, inhibiting GPX4 degradation.\",\n      \"method\": \"SETD7 knockout mice, endothelial-specific AAV knockdown, co-immunoprecipitation, Western blot, lipid peroxidation assay, glucose-stressed endothelial cells\",\n      \"journal\": \"Cardiovascular diabetology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo mouse model with multiple cell contexts, mechanistic pathway placement (SETD7-p53-FBXO45-GPX4), single lab\",\n      \"pmids\": [\"40275362\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FBXO45 promotes Lys103 ubiquitination of TFG (Trk-fused gene), enhancing TFG stability; stabilized TFG facilitates binding of ATF2 transcription factor, upregulating NF-κB p65 expression and promoting migration, invasion, and lung metastasis of TP53-mutant HCC cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay with site-specific mutagenesis (Lys103), orthotopic xenograft model, ATF2/NF-κB reporter assays, siRNA knockdown, overexpression\",\n      \"journal\": \"JHEP reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-specific ubiquitination mutagenesis, downstream transcription factor activation, orthotopic in vivo model, single lab\",\n      \"pmids\": [\"41030651\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FBXO45 interacts with and ubiquitinates DUSP2, leading to its proteasomal degradation, ERK1/2 activation, and enhanced glycolysis in cervical cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, overexpression/knockdown, Seahorse metabolic assay, xenograft model\",\n      \"journal\": \"Naunyn-Schmiedeberg's archives of pharmacology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — co-IP and ubiquitination assay, single lab, no mutagenesis or domain mapping reported in abstract\",\n      \"pmids\": [\"40637745\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"FBXO45 promotes ubiquitination and degradation of Erbin in clear cell renal cell carcinoma, enhancing cell viability, motility, and sunitinib resistance; Fbxo45 expression is negatively correlated with Erbin expression in ccRCC.\",\n      \"method\": \"Co-immunoprecipitation (implied by negative correlation and functional rescue), overexpression/knockdown, xenograft model, sunitinib sensitivity assay\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — functional evidence and co-expression data, limited mechanistic detail in abstract, single lab\",\n      \"pmids\": [\"41285235\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FBXO45 is an atypical F-box protein that does not form canonical SCF complexes (due to substitution in the Cul1-binding sequence) but instead partners with PAM/MycBP2 (RING finger E3) and SKP1 to form the SPF (Skp1-Pam-Fbxo45) ubiquitin ligase complex, which targets a diverse array of substrates—including Munc13-1, p73, Par-4, FBXW7, IGF2BP1, EMT transcription factors, USP49, GGNBP2, IFNLR1, TFG, GPX4, BIM, DUSP2, NP-STEP46, and HIV-1 Tat—for ubiquitylation and proteasomal or autophagic degradation; in the nervous system FBXO45 is essential for synapse formation, neuromuscular junction development, and neuronal migration (partly through regulating N-cadherin proteolysis and extracellular SPRY-domain binding), while in dividing cells it is CDK1-phosphorylated for cell-cycle-regulated degradation and participates in histone mRNA stability via a FBXO45-UPF1-PPP6C complex, collectively placing FBXO45 as a context-dependent E3 ligase adaptor with critical roles in neural development, mitotic fate decisions, genomic integrity, innate immunity, and cancer progression.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FBXO45 is an atypical F-box protein that operates as the substrate-recognition adaptor of a non-canonical ubiquitin ligase: a substitution in its Cul1-binding sequence precludes formation of a classical SCF complex, and instead FBXO45 associates with the RING-finger ligase PAM/MycBP2 (and SKP1) to assemble an E3 complex essential for neural development, including diaphragm innervation, neuromuscular junction synapse formation, axon tract development, and neuronal migration [#0]. The protein recognizes substrates through two distinct modules\\u2014its SPRY domain and its F-box domain\\u2014allowing it to engage a broad substrate repertoire [#5]. In the nervous system it controls synaptic strength by ubiquitylating the vesicle-priming factor Munc13-1 [#2] and guides radial neuron migration by binding SPRY motifs in the extracellular domain of N-cadherin via a nonclassical secretion route [#9]. FBXO45 directs substrates to proteasomal degradation through diverse ubiquitin linkages, including K48-linked chains on EMT transcription factors such as ZEB1 [#11] and K6-linked chains on the STEP phosphatase NP-STEP46 [#13], and can also route substrates to p62/SQSTM1-dependent autophagy, as for phosphorylated HIV-1 Tat [#19]. Through degradation of tumor suppressors and apoptotic regulators\\u2014p73 [#1], Par-4 [#3], FBXW7 during mitotic arrest [#8], and BIM [#18]\\u2014and activation of oncogenic effectors such as IGF2BP1 [#10], FBXO45 functions as a context-dependent regulator of apoptosis, mitotic fate, and tumor progression. It additionally maintains genomic integrity by forming an FBXO45-UPF1-PPP6C complex that stabilizes replication-dependent histone mRNAs, with its own abundance gated by CDK1-mediated phosphorylation for cell-cycle-regulated turnover [#17].\",\n  \"teleology\": [\n    {\n      \"year\": 2009,\n      \"claim\": \"Established that FBXO45 is not a canonical SCF adaptor but instead partners with the RING ligase PAM/Phr1, defining the architecture of a novel E3 complex required for nervous system development.\",\n      \"evidence\": \"Proteomics, knockout mice, and Fbxo45/Phr1 genetic epistasis\",\n      \"pmids\": [\"19398581\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not enumerate the developmental substrates degraded by the complex\", \"Cul1-independence shown but the full subunit composition of the active ligase not biochemically reconstituted\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Identified the first defined degradation substrates, showing FBXO45 controls apoptotic/tumor-suppressor output (p73) and synaptic transmission (Munc13-1) through ubiquitin-proteasome targeting.\",\n      \"evidence\": \"Co-IP, in vitro ubiquitylation, siRNA, and mEPSC electrophysiology in neurons\",\n      \"pmids\": [\"19581926\", \"19996097\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Recognition motifs on p73 and Munc13-1 not mapped\", \"Whether degradation requires PAM/MycBP2 catalytic activity not tested in these reports\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Revealed the SPRY domain as a substrate-docking module and uncovered a non-degradative N-cadherin function, broadening FBXO45 roles beyond proteasomal turnover.\",\n      \"evidence\": \"MS screens, SPRY consensus-motif identification for Par-4, Co-IP and proteolysis assays for N-cadherin\",\n      \"pmids\": [\"24992930\", \"25143387\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which FBXO45 limits N-cadherin proteolysis without ubiquitinating it unclear\", \"Relative contributions of SPRY vs F-box recognition not yet generalized\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Defined dual substrate-recognition logic and named the SPF complex, linking FBXO45 to EMT control by degrading core EMT transcription factors via distinct domains.\",\n      \"evidence\": \"Co-IP, ubiquitination assays, domain mutagenesis (SPRY for Zeb2, F-box for Snai1/2/Twist1), miR-27a* regulation; TAP-MS Hey1 interaction and nuclear redirection\",\n      \"pmids\": [\"25460509\", \"26068074\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Hey1-driven nuclear relocalization not connected to specific nuclear substrates\", \"In vivo relevance of EMT-TF degradation not tested here\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Connected FBXO45 substrate targeting to physiological signaling by showing inflammatory TNF-\\u03b1 suppresses Fbxo45-mediated Munc13-1 turnover to drive pain.\",\n      \"evidence\": \"Rat neuropathic model, Co-IP, ubiquitination, mEPSC, intrathecal TNF-\\u03b1 and siRNA\",\n      \"pmids\": [\"30042425\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular link between TNF-\\u03b1 signaling and reduced Fbxo45 activity not resolved\", \"Single in vivo model\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Placed FBXO45 in mitotic fate control by demonstrating it degrades the tumor suppressor FBXW7 during prolonged mitotic arrest to promote slippage and survival.\",\n      \"evidence\": \"Reciprocal Co-IP, ubiquitination, FBXW7 motif mutagenesis, time-lapse imaging\",\n      \"pmids\": [\"31285543\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger restricting this activity to mitotic arrest not defined\", \"Whether MYCBP2 catalysis is rate-limiting not tested\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Expanded FBXO45 outputs to non-degradative activation and revealed regulation of its own stability, with IGF2BP1 site-specific ubiquitination driving tumorigenesis and DNAJB9 suppressing FBXO45 auto-ubiquitination.\",\n      \"evidence\": \"Site-specific ubiquitination mutagenesis (IGF2BP1 K190/K450), transgenic mice, K48 ubiquitination assays for ZEB1, in vivo metastasis\",\n      \"pmids\": [\"34779401\", \"33966034\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How a single adaptor produces activating vs degradative ubiquitination not mechanistically unified\", \"Auto-ubiquitination regulators beyond DNAJB9 unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Demonstrated diverse linkage chemistry and broad substrate scope across cancers and innate immunity, including K6-linked NP-STEP46 degradation and IFNLR1 turnover that dampens interferon signaling.\",\n      \"evidence\": \"Linkage-specific ubiquitination assays, site mutagenesis (IFNLR1 K319/K320R), proximity-ligation screens, kinase enhancement (NEK6), xenografts for USP49/GGNBP2; RBX1-driven FBXO45 destabilization\",\n      \"pmids\": [\"35279684\", \"35838331\", \"36127399\", \"36379255\", \"35802537\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Determinants selecting K6 vs K48 linkage not defined\", \"How kinases like NEK6 and ligases like RBX1 are integrated with the SPF complex remains incomplete\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified a non-ligase scaffolding function in genome maintenance and clarified cell-cycle control of FBXO45 itself, with the FBXO45-UPF1-PPP6C complex protecting histone mRNAs and CDK1 phosphorylation gating FBXO45 degradation.\",\n      \"evidence\": \"AT2-specific conditional knockout mice, ternary-complex Co-IP, CDK1 kinase and phosphatase assays, histone mRNA stability, spontaneous tumorigenesis; BIM degradation Co-IP/CHX in breast cancer\",\n      \"pmids\": [\"39672818\", \"38773471\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How FBXO45 switches between ligase-adaptor and PPP6C-scaffold roles is unresolved\", \"Structural basis of the UPF1-PPP6C ternary complex unknown\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended FBXO45 to autophagic substrate routing, transcriptional pathway placement, and additional disease contexts, including p62-dependent degradation of HIV-1 Tat and SETD7-p53-driven FBXO45 transcription degrading GPX4.\",\n      \"evidence\": \"TurboID, autophagy-pathway mutagenesis (Tat S62A), SETD7 knockout mice, site-specific ubiquitination (TFG K103), metabolic and xenograft assays for DUSP2/Erbin\",\n      \"pmids\": [\"39936917\", \"40275362\", \"41030651\", \"40637745\", \"41285235\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"What dictates proteasomal vs autophagic routing of FBXO45 substrates is undefined\", \"DUSP2 and Erbin findings lack domain/site mapping\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unresolved how a single adaptor integrates SPRY- versus F-box-based recognition, selects among ubiquitin linkage types and degradation routes (proteasome vs autophagy), and toggles between E3-adaptor and non-catalytic scaffold roles.\",\n      \"evidence\": \"No reconstitution or structural study in the timeline resolves these selectivity rules\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structure of FBXO45 bound to PAM/MycBP2-SKP1 or substrates\", \"No unifying model linking substrate identity to linkage type and degradation pathway\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 3, 8, 10, 15, 17]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [0, 5, 17]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [4, 9, 17]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [3]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [6, 13, 17]},\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 3, 8]}\n    ],\n    \"complexes\": [\"SPF (Skp1-Pam-Fbxo45) ubiquitin ligase complex\", \"FBXO45-MYCBP2/PAM E3 ligase\", \"FBXO45-UPF1-PPP6C complex\"],\n    \"partners\": [\"MYCBP2\", \"SKP1\", \"FBXW7\", \"UPF1\", \"PPP6C\", \"IGF2BP1\", \"N-cadherin\", \"USP49\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}