{"gene":"FEZ1","run_date":"2026-06-09T23:54:43","timeline":{"discoveries":[{"year":1997,"finding":"UNC-76 (FEZ1 ortholog) is required for normal axonal bundling and elongation within axon bundles in C. elegans; the protein is found in cell bodies and processes of all neurons throughout development. At least one human FEZ1 homolog can functionally complement unc-76 in C. elegans, demonstrating conserved function in axonal outgrowth.","method":"Genetic loss-of-function in C. elegans, neuronal localization by expression analysis, cross-species functional complementation","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic loss-of-function with defined phenotype, cross-species rescue providing functional validation, replicated across nematode and human homologs","pmids":["9096408"],"is_preprint":false},{"year":1999,"finding":"FEZ1 (fasciculation and elongation protein zeta-1) is a substrate of PKCzeta: it was identified as a PKCzeta-interacting protein via yeast two-hybrid, interacts with the NH2-terminal V1 domain of PKCzeta, and is phosphorylated by PKCzeta in COS-7 cells. Constitutively active PKCzeta causes cytoplasmic translocation of FEZ1, and staurosporin treatment causes FEZ1 translocation from cytoplasm to plasma membrane. Co-expression of FEZ1 and constitutively active PKCzeta stimulates neuronal differentiation of PC12 cells.","method":"Yeast two-hybrid screening, co-immunoprecipitation, phosphorylation assay in COS-7 cells, PKC inhibitor treatment, PC12 differentiation assay","journal":"The Journal of cell biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal yeast two-hybrid and coexpression phosphorylation assay, functional PKC inhibitor validation, multiple orthogonal methods in one study","pmids":["9971736"],"is_preprint":false},{"year":2001,"finding":"FEZ1/LZTS1 protein is hyperphosphorylated by cAMP-dependent kinase (PKA) during cell-cycle progression, associates with microtubule components, and interacts with p34(cdc2) at late S-G2/M stage in vivo. Restoration of FEZ1 in Fez1-negative cancer cells suppresses tumorigenicity and causes G2/M accumulation.","method":"Immunoprecipitation of Fez1 with microtubule components and p34(cdc2), phosphorylation assay, tumor suppression assay in nude mice, cell cycle analysis by FACS","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo co-immunoprecipitation, kinase phosphorylation assay, functional rescue with defined phenotype, multiple orthogonal methods","pmids":["11504921"],"is_preprint":false},{"year":2003,"finding":"Drosophila UNC-76 (FEZ1 ortholog) binds directly to the tail domain of kinesin heavy chain (KHC), forming a stable complex in vivo, as demonstrated by yeast two-hybrid and copurification assays. Loss of Unc-76 function causes locomotion and axonal transport defects similar to kinesin mutants, and Unc-76 shows dosage-sensitive genetic interactions with Khc and kinesin light chain mutations, placing UNC-76 in the kinesin-I axonal transport pathway.","method":"Yeast two-hybrid, copurification, genetic epistasis (dosage-sensitive interactions with Khc and Klc mutants), loss-of-function locomotion and axonal transport assay","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — yeast two-hybrid plus copurification (two orthogonal binding methods) combined with genetic epistasis placing UNC-76 in the kinesin pathway","pmids":["12925768"],"is_preprint":false},{"year":2004,"finding":"FEZ1 is polyubiquitylated by the U-box-type ubiquitin ligase E4B on Lys27 of ubiquitin, but this modification does not lead to its proteolytic degradation. The E4B–FEZ1 interaction is enhanced by constitutively active PKCzeta. Expression of dominant-negative E4B inhibits neurite extension induced by NGF or by FEZ1/active-PKCzeta co-expression in PC12 cells, indicating that E4B-mediated ubiquitylation of FEZ1 is required for neuritogenesis.","method":"Yeast two-hybrid, co-immunoprecipitation, in vitro polyubiquitylation assay, dominant-negative E4B overexpression in PC12 cells, neurite outgrowth assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro ubiquitylation assay combined with dominant-negative functional assay and co-IP, multiple orthogonal methods in one study","pmids":["15466860"],"is_preprint":false},{"year":2005,"finding":"FEZ1 protein associates with microtubules and directly interacts with JC virus agnoprotein in vitro. Agnoprotein induces the dissociation of FEZ1 from microtubules (microtubule cosedimentation assay), agnoprotein inhibits FEZ1-promoted neurite outgrowth, and FEZ1 overexpression suppresses JCV protein expression and intracellular trafficking, indicating FEZ1 promotes neurite extension via its microtubule association.","method":"Yeast two-hybrid, in vitro binding assay, microtubule cosedimentation assay, neurite outgrowth assay in PC12 cells, viral infection/expression assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro binding plus cosedimentation plus functional neurite/viral assays, multiple orthogonal methods","pmids":["15843383"],"is_preprint":false},{"year":2005,"finding":"FEZ1 overexpression confers post-entry resistance to retroviruses: infected cells show normal viral DNA synthesis but reduced circular DNA formation, indicating a block after reverse transcription but before nuclear entry. FEZ1 knockdown in resistant cells partially restores infectivity.","method":"Affymetrix gene chip expression profiling, retroviral infection assay, viral DNA quantification (Southern/PCR), RNAi knockdown","journal":"Genes & development","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined mechanistic step (post-reverse transcription/pre-nuclear entry) identified by viral DNA analysis, with RNAi validation; single lab","pmids":["15879557"],"is_preprint":false},{"year":2006,"finding":"FEZ1 dimerizes through its C-terminal coiled-coil region, and this same region mediates heterodimerization with FEZ2 and interaction with at least 10 interacting proteins identified by yeast two-hybrid, including transcription regulatory proteins SAP30L, DRAP1, and BAF60a (confirmed by in vitro pulldown with recombinant proteins).","method":"Yeast two-hybrid screen of human fetal brain cDNA library, in vitro pulldown with recombinant fusion proteins, deletion mapping","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — yeast two-hybrid plus in vitro pulldown confirmation for 8 interactions; single lab but two orthogonal binding methods","pmids":["16484223"],"is_preprint":false},{"year":2006,"finding":"FEZ1 promotes axon formation in hippocampal neurons; RNAi-mediated silencing of FEZ1 represses axon formation and retards anterograde mitochondrial movement in neurites, and causes mitochondrial elongation, placing FEZ1 upstream of mitochondrial transport in establishing neuronal polarity.","method":"RNAi knockdown in rat embryo hippocampal neurons, live-cell imaging of mitochondrial motility, immunofluorescence","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — RNAi knockdown with defined cellular phenotype (axon formation, mitochondrial motility), single lab","pmids":["17173861"],"is_preprint":false},{"year":2006,"finding":"C. elegans UNC-69 physically interacts with UNC-76 (FEZ1 ortholog) and they colocalize as puncta in neuronal processes. The UNC-69/UNC-76 complex cooperates to regulate axon extension, fasciculation, and presynaptic organization. Genetic analysis shows overlapping loss-of-function phenotypes (axon outgrowth/guidance defects and synaptic vesicle mislocalization).","method":"Yeast two-hybrid, co-localization imaging in C. elegans neurons, genetic loss-of-function double-mutant analysis","journal":"Journal of biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — physical interaction (yeast two-hybrid) plus in vivo co-localization plus genetic epistasis, multiple orthogonal methods","pmids":["16725058"],"is_preprint":false},{"year":2007,"finding":"FEZ1 associates with kinesin superfamily protein 5 (KIF5/kinesin-1) and tubulin by co-immunoprecipitation and pulldown assay in PC12 cells. NGF-stimulated FEZ1 co-localizes with mitochondria in neurites, and FEZ1 siRNA knockdown reduces anterograde mitochondrial motility, suggesting FEZ1/kinesin complex mediates mitochondrial transport along microtubules.","method":"Co-immunoprecipitation, pulldown assay, RNAi knockdown, live-cell imaging of mitochondrial motility in NGF-treated PC12 cells","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP and pulldown confirming FEZ1/KIF5 interaction, combined with RNAi functional validation of mitochondrial transport, replicated concept from PMID:17173861","pmids":["17669366"],"is_preprint":false},{"year":2007,"finding":"Lzts1 knockout MEFs show increased Cdc25C degradation during M phase, leading to decreased Cdk1 activity. This results in accelerated mitotic progression, resistance to taxol/nocodazole-induced M phase arrest, and improper chromosome segregation. Lzts1-deficient mice show increased incidence of spontaneous and carcinogen-induced cancers, establishing LZTS1 as a regulator of Cdk1/Cdc25C interaction during mitosis.","method":"Knockout mouse model, MEF isolation, Western blot for Cdc25C and Cdk1 activity, drug sensitivity assay, chromosome segregation analysis, tumor incidence monitoring","journal":"Cancer cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout with mechanistic dissection (Cdc25C stability, Cdk1 activity), multiple cellular phenotypes, in vivo tumor incidence data","pmids":["17349584"],"is_preprint":false},{"year":2009,"finding":"Neuronal FEZ1 expression (high in neurons, low in astrocytes/microglia) underlies intrinsic resistance to HIV-1 nuclear entry: siRNA knockdown of endogenous FEZ1 in neurons increases HIV-1 infectivity, while FEZ1 overexpression in microglia (sensitive cells) increases resistance. FEZ1 resistance is not IFN-inducible, defining it as a constitutive neuron-specific antiviral factor acting before nuclear entry.","method":"siRNA knockdown in primary neurons, FEZ1 overexpression in microglia, pseudotyped HIV-1 infection assay with quantification of early infection","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — bidirectional gain/loss-of-function with defined infectivity readout, single lab","pmids":["19667186"],"is_preprint":false},{"year":2009,"finding":"FEZ1 is a natively unfolded protein that dimerizes in solution. Small-angle X-ray scattering reveals an elongated dimeric shape; in vitro pulldown shows dimerization involves the N-terminus. PKC phosphorylates FEZ1 predominantly in its C-terminal region, and this phosphorylation inhibits FEZ1 interaction with the CLASP2-interacting domain in vitro, without major conformational changes.","method":"Circular dichroism, fluorescence spectroscopy, limited proteolysis, SAXS, in vitro pulldown, in vitro PKC phosphorylation assay","journal":"Proteins","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple biophysical methods (SAXS, CD, fluorescence) plus in vitro phosphorylation with functional consequence (inhibited CLASP2 interaction), single lab but orthogonal methods","pmids":["18615714"],"is_preprint":false},{"year":2010,"finding":"FEZ1 forms an intermolecular disulfide bond through Cys-133 that is essential for dimerization, demonstrated in the fragment FEZ1(92-194), full-length recombinant FEZ1, and endogenous FEZ1 from HEK293 cells. This disulfide-mediated dimerization may enable FEZ1 to act as a bivalent transport adaptor.","method":"In vitro pulldown of recombinant FEZ1 fragments, mass spectrometry analysis, isolation of endogenous FEZ1 from HEK293 cells, disulfide bond identification","journal":"Journal of proteome research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and endogenous validation of disulfide bond, mass spectrometry identification of Cys-133, single lab","pmids":["20812761"],"is_preprint":false},{"year":2011,"finding":"FEZ1 interacts with DISC1 to synergistically regulate dendritic growth of newborn neurons in the adult mouse hippocampus. This FEZ1-DISC1 pathway is parallel to and complementary with the DISC1-NDEL1 pathway that regulates cell positioning; epistasis analysis of two independent patient cohorts shows interaction between FEZ1 and DISC1 (but not FEZ1 and NDEL1) for schizophrenia risk.","method":"Co-immunoprecipitation, in vivo knockdown in adult mouse hippocampus, morphological analysis of newborn neurons, genetic epistasis analysis in two patient cohorts","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo functional epistasis (parallel pathway dissection) combined with co-IP and two independent human cohort genetic epistasis analyses","pmids":["22099459"],"is_preprint":false},{"year":2013,"finding":"FEZ1 forms a stable complex with SCOCO (UNC-69 homolog) through coiled-coil interactions. Structural analysis by NMR, crosslinking-MS, and SAXS shows FEZ1(92-194) homodimerizes in antiparallel topology, and the FEZ1/SCOCO interaction interface is consistent with the UNC-76/UNC-69 interaction. A heterotetrameric complex model is supported by SAXS.","method":"NMR, cross-linking coupled with mass spectrometry, SAXS, molecular modelling, in vitro complex formation","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Moderate — multiple structural/biophysical methods (NMR, crosslink-MS, SAXS) converging on same interaction interface, single lab","pmids":["24116125"],"is_preprint":false},{"year":2013,"finding":"SCOCO forms a parallel left-handed coiled-coil dimer and forms a stable homogeneous complex with the coiled-coil domain of FEZ1. SCOCO dimerization and surface residue R117 are important for the SCOCO-FEZ1 interaction, established by crystal structure determination and mutagenesis.","method":"X-ray crystallography of SCOCO coiled-coil domain at 2.7 Å, site-directed mutagenesis (E93V/K97L and N125L/N132V double mutants), multi-angle laser light scattering, native mass spectrometry, in vitro complex formation assay","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure plus mutagenesis plus orthogonal biophysical validation (MALS, native MS), single lab","pmids":["24098481"],"is_preprint":false},{"year":2014,"finding":"Cdc20/APC (anaphase-promoting complex) ubiquitin ligase controls dendrite growth in neurons by targeting FEZ1 for degradation. BubR1 modulates Cdc20/APC activity and thereby FEZ1 levels; BubR1 is deacetylated by HDAC11, which disinhibits Cdc20/APC. This pathway operates in hippocampal dentate granule cells and olfactory bulb neurons.","method":"Overexpression and knockdown of Cdc20/APC and BubR1 in neurons, ubiquitin-mediated degradation assay, dendrite morphology analysis, acetylation status analysis of BubR1","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — gain/loss-of-function of multiple pathway components with defined morphological readout (dendrite growth), single lab","pmids":["24726361"],"is_preprint":false},{"year":2015,"finding":"HIV-1 associates with the kinesin-1 adaptor FEZ1; RNAi depletion of FEZ1 blocks early HIV-1 infection with virus showing bidirectional but no net movement toward the nucleus. The ability of exogenously expressed FEZ1 to promote HIV-1 infection requires its binding to kinesin-1. Both dynein and kinesin-1 are required for HIV-1 trafficking to the nucleus.","method":"RNAi knockdown, live-cell single-particle tracking of HIV-1 particles, exogenous expression of FEZ1 variants (including kinesin-1 binding mutants), early infection assay","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — bidirectional RNAi and rescue with binding-mutant FEZ1 defining kinesin-1 dependency, combined with quantitative live-cell particle tracking","pmids":["25818806"],"is_preprint":false},{"year":2016,"finding":"MARK/PAR-1 kinases phosphorylate FEZ1 at serine 58, regulating its function as a kinesin-1 adapter for presynaptic cargo transport. Loss of MARK/PAR-1 causes FEZ1, kinesin-1, and presynaptic cargoes to co-aggregate in cell bodies and axons instead of being transported. Unphosphorylated FEZ1 co-aggregates with kinesin-1 and cargoes are also found in Alzheimer's disease model mouse brains.","method":"Phosphorylation assay, mass spectrometry identification of phosphorylation site, MARK/PAR-1 loss-of-function in neurons, immunofluorescence, live-cell imaging, analysis of transgenic AD mouse brain","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — phosphorylation site identified by mass spectrometry, loss-of-function with specific transport phenotype, replicated in disease model, multiple orthogonal methods","pmids":["27247180"],"is_preprint":false},{"year":2018,"finding":"In C. elegans, UNC-76/FEZ1 and UNC-16/JIP3 limit mitochondrial density in neuronal processes by maintaining the balance of anterograde and retrograde mitochondrial transport. unc-76 mutants show increased mitochondrial density, elevated kinesin heavy and light chain levels in neurons, and a net anterograde bias in mitochondrial flux that is partly dependent on dynein.","method":"Genetic loss-of-function (unc-76 mutants), live-cell fluorescence imaging of mitochondrial transport, quantification of mitochondrial density and flux, genetic epistasis with dynein mutants","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function with quantitative live-cell transport imaging and epistasis with dynein, single lab","pmids":["29895958"],"is_preprint":false},{"year":2019,"finding":"FEZ1 directly interacts with HIV-1 capsid protein (CA) hexamers, specifically binding through acidic poly-glutamate stretches to the positively charged central pore of CA hexamers. This interaction competes with nucleotides and inositol hexaphosphate (IP6) at the same site. Mutation of FEZ1 capsid-interacting residues significantly reduces HIV-1 trafficking toward the nucleus and early infection.","method":"Direct binding assay, all-atom molecular dynamics simulations, competition assay with IP6/nucleotides, site-directed mutagenesis of FEZ1 interacting residues, single-particle HIV-1 trafficking assay, early infection assay","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — direct binding defined with MD simulation and mutagenesis, competition assay establishing binding site, functional validation by trafficking and infection assay, multiple orthogonal methods","pmids":["31422020"],"is_preprint":false},{"year":2021,"finding":"FEZ1 forms a complex with CRMP1 at neuronal growth cones and is required for axonal development; FEZ1 deficiency causes growth cone collapse and impaired axonal development similar to CRMP1 loss. Separately, FEZ1 forms a complex with DCC and Syntaxin-1 (components of the Netrin-1 signaling pathway), and FEZ1-deficient neurons fail to respond to Netrin-1 or Sema3A guidance cues.","method":"Co-immunoprecipitation, co-localization imaging, loss-of-function (FEZ1 deficiency) in rat hippocampal neurons, axon/dendrite morphology analysis, guidance cue response assay (Netrin-1, Sema3A)","journal":"eNeuro","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — co-IP identifies complexes, loss-of-function shows defined morphological and signaling phenotype, single lab","pmids":["33771901"],"is_preprint":false},{"year":2021,"finding":"FEZ1 deletion in rat motor neurons strongly impairs axon and dendrite development and significantly delays synaptic protein transport into developing neurites. Drosophila unc-76 mutants show severe locomotion impairment and reduced synaptic boutons at neuromuscular junctions. Pharmacological activation of UNC-51/ATG1 (a FEZ1-activating kinase) with rapamycin and metformin ameliorates these defects.","method":"FEZ1 deletion in human ES-derived and rat neurons, neurite morphology analysis, synaptic protein transport assay, Drosophila unc-76 genetic analysis, pharmacological rescue with rapamycin/metformin","journal":"Human molecular genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic loss-of-function across two model systems with defined cellular and synaptic phenotypes, pharmacological rescue, single lab","pmids":["33395696"],"is_preprint":false},{"year":2017,"finding":"FEZ1 interacts with the retinoic acid receptor (RAR) through its coiled-coil region (interacting with the ligand-binding domain of RAR). In the presence of retinoic acid, FEZ1 induces hoxb4 gene expression, demonstrating a role in transcriptional regulation.","method":"In vitro binding assay, co-immunoprecipitation, interaction interface mapping, 86-gene panel expression assay in cells co-expressing FEZ1 and RAR","journal":"FEBS open bio","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — in vitro binding and co-IP plus functional gene expression readout, single lab, single gene target confirmed","pmids":["29321952"],"is_preprint":false},{"year":2009,"finding":"FEZ1 interacts with NEK1 and CLASP2 through coiled-coil interactions in vitro, and all three proteins co-localize with gamma-tubulin in a perinuclear/centrosomal region in mammalian cells. FEZ1/CLASP2 co-localization is inhibited by PMA treatment, and CLASP2 is phosphorylated by active PKC isoforms, suggesting PKC regulates FEZ1/CLASP2 centrosomal complex.","method":"In vitro pulldown (coiled-coil interactions), co-localization imaging, PMA treatment, PKC phosphorylation assay","journal":"Molecular and cellular biochemistry","confidence":"Low","confidence_rationale":"Tier 3 / Weak — in vitro pulldown and co-localization, single lab, no loss-of-function validation of centrosomal function","pmids":["19924516"],"is_preprint":false},{"year":2022,"finding":"SCOC, ULK1, and NBR1 directly bind to FEZ1 protein to form a protein complex, as demonstrated by immunoprecipitation. All four proteins (FEZ1/SCOC/ULK1/NBR1) are targets of miR-129-5p, and their expression is regulated coordinately in neuronal autophagy.","method":"Immunoprecipitation, dual-luciferase reporter system (miR-129-5p target validation), overexpression/interference of miR-129-5p in neuronal cells","journal":"Bioengineered","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single immunoprecipitation assay, single lab, limited mechanistic follow-up on complex function","pmids":["35435132"],"is_preprint":false}],"current_model":"FEZ1 (UNC-76) is a kinesin-1 adaptor protein that forms an elongated dimer (stabilized by a Cys-133 disulfide bond) and mediates anterograde axonal transport of mitochondria and presynaptic cargo by binding KIF5/kinesin-1 and tubulin; its transport activity is regulated by phosphorylation at Ser58 by MARK/PAR-1 kinases and by PKCzeta (which also promotes neuronal differentiation), and its stability is controlled by Cdc20/APC-mediated ubiquitin-proteasomal degradation; at the cell cycle level, FEZ1 stabilizes Cdc25C to maintain Cdk1 activity during mitosis, and it also acts as a capsid-associated host factor exploited by HIV-1 for inward nuclear trafficking by binding the central pore of CA hexamers via acidic poly-glutamate stretches."},"narrative":{"mechanistic_narrative":"FEZ1 (fasciculation and elongation protein zeta-1, ortholog of C. elegans UNC-76) is a kinesin-1 adaptor that drives anterograde microtubule-based transport in neurons and controls axonal outgrowth, fasciculation, and neuronal polarity [PMID:9096408, PMID:12925768, PMID:17173861]. It is a natively unfolded, elongated dimer whose self-association requires its N-terminus and an intermolecular Cys-133 disulfide bond, configuring it as a bivalent transport adaptor [PMID:18615714, PMID:20812761]. Through its C-terminal coiled-coil region FEZ1 binds the kinesin heavy chain tail and tubulin and recruits cargoes—mitochondria and presynaptic components—for delivery into developing neurites, so that its loss stalls anterograde mitochondrial movement and synaptic protein transport [PMID:12925768, PMID:17669366, PMID:25818806, PMID:33395696]. Transport activity is set by phosphorylation: MARK/PAR-1 kinases phosphorylate FEZ1 at Ser58 to license cargo movement, and loss of this control causes FEZ1, kinesin-1, and presynaptic cargoes to co-aggregate in cell bodies and axons, a state also seen in Alzheimer's disease model brains [PMID:27247180]. FEZ1 is also a PKCzeta substrate that, together with active PKCzeta and E4B-mediated Lys27 polyubiquitylation, promotes neuronal differentiation and neurite extension [PMID:9971736, PMID:15466860], and it acts within DISC1, CRMP1, and Netrin-1/DCC-Syntaxin-1 signaling modules to support dendritic and axonal development and guidance-cue responses [PMID:22099459, PMID:33771901]. Independently, the FEZ1/LZTS1 product functions in mitosis, where it associates with microtubules and Cdk1 and stabilizes Cdc25C to sustain Cdk1 activity; its loss accelerates mitosis, causes chromosome missegregation, and predisposes to tumors [PMID:11504921, PMID:17349584]. FEZ1 additionally serves as a constitutive, neuron-enriched host factor for HIV-1: it binds the central pore of capsid hexamers through acidic poly-glutamate stretches and links the incoming capsid to kinesin-1 for inward trafficking toward the nucleus [PMID:19667186, PMID:25818806, PMID:31422020].","teleology":[{"year":1997,"claim":"Established FEZ1's ancestral function by showing its C. elegans ortholog UNC-76 is required for axon bundling and elongation, with human FEZ1 able to rescue the defect—defining a conserved role in axonal outgrowth.","evidence":"Genetic loss-of-function and cross-species complementation in C. elegans","pmids":["9096408"],"confidence":"High","gaps":["Molecular partners and biochemical activity unresolved","No mechanism for how the protein supports outgrowth"]},{"year":1999,"claim":"Identified FEZ1 as a PKCzeta substrate and effector, linking it to a kinase signal that triggers cytoplasmic translocation and drives neuronal differentiation.","evidence":"Yeast two-hybrid, co-IP, phosphorylation assay, and PC12 differentiation assay","pmids":["9971736"],"confidence":"High","gaps":["Phosphorylation sites not mapped","Downstream effect of phosphorylation on cargo binding not defined"]},{"year":2001,"claim":"Connected FEZ1/LZTS1 to the cell cycle, showing PKA-dependent hyperphosphorylation, association with microtubules and p34cdc2, and tumor-suppressor activity with G2/M accumulation.","evidence":"Co-IP, phosphorylation assay, nude mouse tumor suppression and FACS cell-cycle analysis","pmids":["11504921"],"confidence":"High","gaps":["Direct molecular target in the cell cycle not yet identified","Relationship between neuronal and mitotic roles unclear"]},{"year":2003,"claim":"Placed FEZ1/UNC-76 directly in the kinesin-1 axonal transport pathway by demonstrating direct binding to the kinesin heavy chain tail plus dosage-sensitive genetic interactions.","evidence":"Yeast two-hybrid, copurification, and genetic epistasis with Khc/Klc in Drosophila","pmids":["12925768"],"confidence":"High","gaps":["Specific cargoes transported not identified","Regulation of the FEZ1–kinesin interaction unknown"]},{"year":2004,"claim":"Showed E4B ubiquitin ligase polyubiquitylates FEZ1 on Lys27 of ubiquitin in a non-degradative manner required for neuritogenesis, defining a PKCzeta-enhanced regulatory modification.","evidence":"In vitro ubiquitylation, co-IP, and dominant-negative E4B neurite outgrowth assay in PC12 cells","pmids":["15466860"],"confidence":"High","gaps":["Functional consequence of K27 linkage on FEZ1 activity not defined","Whether this regulates transport vs differentiation unclear"]},{"year":2005,"claim":"Established that FEZ1's microtubule association underlies neurite extension and is targeted by JC virus agnoprotein, which dissociates FEZ1 from microtubules.","evidence":"In vitro binding, microtubule cosedimentation, and neurite/viral assays","pmids":["15843383"],"confidence":"High","gaps":["Microtubule-binding interface not mapped","Relationship to kinesin-1 binding not resolved"]},{"year":2006,"claim":"Defined FEZ1 as a retroviral restriction factor acting after reverse transcription but before nuclear entry, the first link to viral nuclear trafficking.","evidence":"Expression profiling, retroviral infection with viral DNA quantification, and RNAi knockdown","pmids":["15879557"],"confidence":"Medium","gaps":["Molecular mechanism of the block undefined","Direct viral binding partner not identified"]},{"year":2006,"claim":"Mapped FEZ1's C-terminal coiled-coil as the hub for homodimerization, FEZ2 heterodimerization, and binding to transcriptional regulators, broadening its interactome.","evidence":"Yeast two-hybrid screen with in vitro pulldown confirmation and deletion mapping","pmids":["16484223"],"confidence":"Medium","gaps":["Functional significance of transcriptional-regulator interactions untested","Cellular relevance of FEZ1/FEZ2 heterodimers unknown"]},{"year":2006,"claim":"Linked FEZ1 directly to mitochondrial transport and neuronal polarity, showing knockdown represses axon formation and slows anterograde mitochondrial movement.","evidence":"RNAi and live mitochondrial imaging in rat hippocampal neurons","pmids":["17173861"],"confidence":"Medium","gaps":["Adaptor that couples FEZ1 to mitochondria not identified here","Single-lab finding"]},{"year":2006,"claim":"Identified the conserved UNC-69/UNC-76 complex regulating axon extension, fasciculation, and presynaptic organization, extending FEZ1 function into synaptic assembly.","evidence":"Yeast two-hybrid, in vivo colocalization, and double-mutant genetics in C. elegans","pmids":["16725058"],"confidence":"High","gaps":["Biochemical role of the complex in transport not defined","Human SCOCO equivalence not established here"]},{"year":2007,"claim":"Resolved the molecular adaptor link by showing FEZ1 associates with KIF5/kinesin-1 and tubulin and is required for anterograde mitochondrial motility in neurites.","evidence":"Co-IP, pulldown, RNAi, and live imaging in NGF-treated PC12 cells","pmids":["17669366"],"confidence":"High","gaps":["Direct mitochondrial receptor unidentified","How phosphorylation gates the KIF5 interaction not addressed"]},{"year":2007,"claim":"Established the mitotic mechanism of LZTS1/FEZ1: knockout MEFs degrade Cdc25C, lower Cdk1 activity, missegregate chromosomes, and mice develop cancers, defining a Cdk1/Cdc25C regulatory role.","evidence":"Knockout mouse, MEF analysis, Cdk1 activity assays, and tumor incidence","pmids":["17349584"],"confidence":"High","gaps":["Direct biochemical mechanism of Cdc25C stabilization undefined","Integration with neuronal transport role unresolved"]},{"year":2009,"claim":"Characterized FEZ1 biophysically as an elongated, natively unfolded dimer and showed PKC phosphorylates its C-terminus to inhibit CLASP2 binding, linking conformation-independent phosphoregulation to partner selection.","evidence":"CD, fluorescence, limited proteolysis, SAXS, and in vitro PKC phosphorylation","pmids":["18615714"],"confidence":"High","gaps":["Functional consequence of CLASP2 inhibition in cells not tested","Precise phosphosites not mapped here"]},{"year":2009,"claim":"Defined neuron-specific FEZ1 expression as the basis for constitutive, IFN-independent resistance to HIV-1 nuclear entry, demonstrated bidirectionally.","evidence":"siRNA in primary neurons and FEZ1 overexpression in microglia with HIV-1 infection assays","pmids":["19667186"],"confidence":"Medium","gaps":["Molecular target on the virus not yet identified","Reconciliation with pro-trafficking role came only later"]},{"year":2010,"claim":"Identified the Cys-133 intermolecular disulfide as essential for FEZ1 dimerization, providing a structural basis for bivalent adaptor function.","evidence":"In vitro and endogenous pulldowns with mass spectrometry disulfide mapping","pmids":["20812761"],"confidence":"Medium","gaps":["Redox regulation of dimerization in vivo untested","Relationship to N-terminal dimerization interface unclear"]},{"year":2011,"claim":"Placed FEZ1 in a DISC1-dependent pathway controlling dendritic growth of adult-born neurons and linked the interaction to schizophrenia risk in human cohorts.","evidence":"Co-IP, in vivo hippocampal knockdown, and genetic epistasis in two patient cohorts","pmids":["22099459"],"confidence":"High","gaps":["Mechanism by which DISC1 modulates FEZ1 transport activity undefined","Causal variant not identified"]},{"year":2013,"claim":"Provided structural definition of the FEZ1 coiled-coil, showing antiparallel homodimerization and a heterotetrameric FEZ1/SCOCO complex, the human counterpart of UNC-76/UNC-69.","evidence":"NMR, crosslinking-MS, SAXS, and modelling (with companion SCOCO crystal structure and mutagenesis)","pmids":["24116125","24098481"],"confidence":"High","gaps":["Functional role of the FEZ1/SCOCO tetramer in transport not assayed","Stoichiometry in cells not confirmed"]},{"year":2014,"claim":"Showed Cdc20/APC ubiquitin ligase targets FEZ1 for degradation to limit dendrite growth, with BubR1/HDAC11 controlling APC activity—defining proteolytic control of FEZ1 levels in neurons.","evidence":"Gain/loss-of-function of APC components, degradation assays, and dendrite morphology","pmids":["24726361"],"confidence":"Medium","gaps":["Degron on FEZ1 not mapped","Interplay with non-degradative E4B ubiquitylation unresolved"]},{"year":2015,"claim":"Reversed the antiviral picture by demonstrating FEZ1 promotes early HIV-1 infection as a kinesin-1 adaptor, with depletion causing bidirectional but non-productive viral movement.","evidence":"RNAi, single-particle tracking, and rescue with kinesin-1-binding mutants","pmids":["25818806"],"confidence":"High","gaps":["Direct viral binding site not yet defined here","Determinants of net directionality with dynein unresolved"]},{"year":2016,"claim":"Identified Ser58 as the MARK/PAR-1 phosphosite that licenses FEZ1's kinesin-1 adaptor function for presynaptic cargo, with loss causing pathological co-aggregation also seen in Alzheimer's models.","evidence":"Mass spectrometry phosphosite mapping, MARK/PAR-1 loss-of-function, imaging, and AD mouse brain analysis","pmids":["27247180"],"confidence":"High","gaps":["How Ser58 phosphorylation alters cargo affinity mechanistically undefined","Causal role in disease aggregation not established"]},{"year":2018,"claim":"Demonstrated FEZ1/UNC-76 limits neuronal mitochondrial density by balancing anterograde and retrograde transport, refining its role beyond simple anterograde delivery.","evidence":"C. elegans genetics, quantitative live transport imaging, and dynein epistasis","pmids":["29895958"],"confidence":"Medium","gaps":["Mechanism by which FEZ1 affects motor levels unknown","Direct coupling to dynein not established"]},{"year":2019,"claim":"Resolved the molecular basis of FEZ1-HIV-1 capsid engagement: acidic poly-glutamate stretches bind the positively charged CA hexamer central pore, competing with IP6/nucleotides, and are required for nuclear trafficking.","evidence":"Direct binding, MD simulation, IP6 competition, mutagenesis, and single-particle trafficking","pmids":["31422020"],"confidence":"High","gaps":["Whether capsid binding alters normal cellular cargo handling unknown","Structural complex not determined experimentally"]},{"year":2021,"claim":"Embedded FEZ1 in growth-cone guidance machinery, showing it complexes with CRMP1 and with DCC/Syntaxin-1 and is required for Netrin-1 and Sema3A responses.","evidence":"Co-IP, colocalization, and loss-of-function guidance assays in rat hippocampal neurons","pmids":["33771901"],"confidence":"Medium","gaps":["Whether transport vs scaffolding underlies guidance defects unclear","Single-lab finding"]},{"year":2021,"claim":"Showed FEZ1 deletion impairs axon/dendrite development and delays synaptic protein transport across model systems, with pharmacological UNC-51/ATG1 activation rescuing defects—pointing to a druggable kinase upstream.","evidence":"FEZ1 deletion in human ES-derived and rat neurons, Drosophila genetics, and rapamycin/metformin rescue","pmids":["33395696"],"confidence":"Medium","gaps":["How UNC-51/ATG1 activates FEZ1 mechanistically undefined","Site of ATG1 regulation on FEZ1 not mapped"]},{"year":null,"claim":"How FEZ1's distinct roles—neuronal kinesin-1 transport, mitotic Cdc25C/Cdk1 regulation, transcriptional partnerships, and viral capsid binding—are coordinated within a single protein, and how its multiple phosphorylation and ubiquitylation events are integrated, remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No unified model linking transport and cell-cycle functions","Phospho-/ubiquitin code controlling cargo selection not deciphered","No high-resolution structure of FEZ1 bound to kinesin-1 or cargo"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060090","term_label":"molecular adaptor 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Able to restore partial locomotion and axonal fasciculation to C.elegans unc-76 mutants in germline transformation experiments. 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one","url":"https://pubmed.ncbi.nlm.nih.gov/24116125","citation_count":6,"is_preprint":false},{"pmid":"29321952","id":"PMC_29321952","title":"Fasciculation and elongation zeta-1 protein (FEZ1) interacts with the retinoic acid receptor and participates in transcriptional regulation of the Hoxb4 gene.","date":"2017","source":"FEBS open bio","url":"https://pubmed.ncbi.nlm.nih.gov/29321952","citation_count":6,"is_preprint":false},{"pmid":"37746155","id":"PMC_37746155","title":"Expression of the schizophrenia associated gene FEZ1 in the early developing fetal human forebrain.","date":"2023","source":"Frontiers in neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/37746155","citation_count":3,"is_preprint":false},{"pmid":"39894009","id":"PMC_39894009","title":"Blood transcriptomics identifies FEZ1 as a potential biomarker for inflammatory bowel disease.","date":"2025","source":"Computers in biology and medicine","url":"https://pubmed.ncbi.nlm.nih.gov/39894009","citation_count":2,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":30091,"output_tokens":7703,"usd":0.102909,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":17070,"output_tokens":6726,"usd":0.12675,"stage2_stop_reason":"end_turn"},"total_usd":0.229659,"stage1_batch_id":"msgbatch_01AsR7g8dGTEiEw9U83bJeWn","stage2_batch_id":"msgbatch_01YV5ZyxtFNUZEjxRcpd9jzb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"UNC-76 (FEZ1 ortholog) is required for normal axonal bundling and elongation within axon bundles in C. elegans; the protein is found in cell bodies and processes of all neurons throughout development. At least one human FEZ1 homolog can functionally complement unc-76 in C. elegans, demonstrating conserved function in axonal outgrowth.\",\n      \"method\": \"Genetic loss-of-function in C. elegans, neuronal localization by expression analysis, cross-species functional complementation\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic loss-of-function with defined phenotype, cross-species rescue providing functional validation, replicated across nematode and human homologs\",\n      \"pmids\": [\"9096408\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"FEZ1 (fasciculation and elongation protein zeta-1) is a substrate of PKCzeta: it was identified as a PKCzeta-interacting protein via yeast two-hybrid, interacts with the NH2-terminal V1 domain of PKCzeta, and is phosphorylated by PKCzeta in COS-7 cells. Constitutively active PKCzeta causes cytoplasmic translocation of FEZ1, and staurosporin treatment causes FEZ1 translocation from cytoplasm to plasma membrane. Co-expression of FEZ1 and constitutively active PKCzeta stimulates neuronal differentiation of PC12 cells.\",\n      \"method\": \"Yeast two-hybrid screening, co-immunoprecipitation, phosphorylation assay in COS-7 cells, PKC inhibitor treatment, PC12 differentiation assay\",\n      \"journal\": \"The Journal of cell biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal yeast two-hybrid and coexpression phosphorylation assay, functional PKC inhibitor validation, multiple orthogonal methods in one study\",\n      \"pmids\": [\"9971736\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"FEZ1/LZTS1 protein is hyperphosphorylated by cAMP-dependent kinase (PKA) during cell-cycle progression, associates with microtubule components, and interacts with p34(cdc2) at late S-G2/M stage in vivo. Restoration of FEZ1 in Fez1-negative cancer cells suppresses tumorigenicity and causes G2/M accumulation.\",\n      \"method\": \"Immunoprecipitation of Fez1 with microtubule components and p34(cdc2), phosphorylation assay, tumor suppression assay in nude mice, cell cycle analysis by FACS\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo co-immunoprecipitation, kinase phosphorylation assay, functional rescue with defined phenotype, multiple orthogonal methods\",\n      \"pmids\": [\"11504921\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"Drosophila UNC-76 (FEZ1 ortholog) binds directly to the tail domain of kinesin heavy chain (KHC), forming a stable complex in vivo, as demonstrated by yeast two-hybrid and copurification assays. Loss of Unc-76 function causes locomotion and axonal transport defects similar to kinesin mutants, and Unc-76 shows dosage-sensitive genetic interactions with Khc and kinesin light chain mutations, placing UNC-76 in the kinesin-I axonal transport pathway.\",\n      \"method\": \"Yeast two-hybrid, copurification, genetic epistasis (dosage-sensitive interactions with Khc and Klc mutants), loss-of-function locomotion and axonal transport assay\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — yeast two-hybrid plus copurification (two orthogonal binding methods) combined with genetic epistasis placing UNC-76 in the kinesin pathway\",\n      \"pmids\": [\"12925768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"FEZ1 is polyubiquitylated by the U-box-type ubiquitin ligase E4B on Lys27 of ubiquitin, but this modification does not lead to its proteolytic degradation. The E4B–FEZ1 interaction is enhanced by constitutively active PKCzeta. Expression of dominant-negative E4B inhibits neurite extension induced by NGF or by FEZ1/active-PKCzeta co-expression in PC12 cells, indicating that E4B-mediated ubiquitylation of FEZ1 is required for neuritogenesis.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, in vitro polyubiquitylation assay, dominant-negative E4B overexpression in PC12 cells, neurite outgrowth assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro ubiquitylation assay combined with dominant-negative functional assay and co-IP, multiple orthogonal methods in one study\",\n      \"pmids\": [\"15466860\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"FEZ1 protein associates with microtubules and directly interacts with JC virus agnoprotein in vitro. Agnoprotein induces the dissociation of FEZ1 from microtubules (microtubule cosedimentation assay), agnoprotein inhibits FEZ1-promoted neurite outgrowth, and FEZ1 overexpression suppresses JCV protein expression and intracellular trafficking, indicating FEZ1 promotes neurite extension via its microtubule association.\",\n      \"method\": \"Yeast two-hybrid, in vitro binding assay, microtubule cosedimentation assay, neurite outgrowth assay in PC12 cells, viral infection/expression assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro binding plus cosedimentation plus functional neurite/viral assays, multiple orthogonal methods\",\n      \"pmids\": [\"15843383\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"FEZ1 overexpression confers post-entry resistance to retroviruses: infected cells show normal viral DNA synthesis but reduced circular DNA formation, indicating a block after reverse transcription but before nuclear entry. FEZ1 knockdown in resistant cells partially restores infectivity.\",\n      \"method\": \"Affymetrix gene chip expression profiling, retroviral infection assay, viral DNA quantification (Southern/PCR), RNAi knockdown\",\n      \"journal\": \"Genes & development\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined mechanistic step (post-reverse transcription/pre-nuclear entry) identified by viral DNA analysis, with RNAi validation; single lab\",\n      \"pmids\": [\"15879557\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"FEZ1 dimerizes through its C-terminal coiled-coil region, and this same region mediates heterodimerization with FEZ2 and interaction with at least 10 interacting proteins identified by yeast two-hybrid, including transcription regulatory proteins SAP30L, DRAP1, and BAF60a (confirmed by in vitro pulldown with recombinant proteins).\",\n      \"method\": \"Yeast two-hybrid screen of human fetal brain cDNA library, in vitro pulldown with recombinant fusion proteins, deletion mapping\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — yeast two-hybrid plus in vitro pulldown confirmation for 8 interactions; single lab but two orthogonal binding methods\",\n      \"pmids\": [\"16484223\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"FEZ1 promotes axon formation in hippocampal neurons; RNAi-mediated silencing of FEZ1 represses axon formation and retards anterograde mitochondrial movement in neurites, and causes mitochondrial elongation, placing FEZ1 upstream of mitochondrial transport in establishing neuronal polarity.\",\n      \"method\": \"RNAi knockdown in rat embryo hippocampal neurons, live-cell imaging of mitochondrial motility, immunofluorescence\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — RNAi knockdown with defined cellular phenotype (axon formation, mitochondrial motility), single lab\",\n      \"pmids\": [\"17173861\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"C. elegans UNC-69 physically interacts with UNC-76 (FEZ1 ortholog) and they colocalize as puncta in neuronal processes. The UNC-69/UNC-76 complex cooperates to regulate axon extension, fasciculation, and presynaptic organization. Genetic analysis shows overlapping loss-of-function phenotypes (axon outgrowth/guidance defects and synaptic vesicle mislocalization).\",\n      \"method\": \"Yeast two-hybrid, co-localization imaging in C. elegans neurons, genetic loss-of-function double-mutant analysis\",\n      \"journal\": \"Journal of biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — physical interaction (yeast two-hybrid) plus in vivo co-localization plus genetic epistasis, multiple orthogonal methods\",\n      \"pmids\": [\"16725058\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"FEZ1 associates with kinesin superfamily protein 5 (KIF5/kinesin-1) and tubulin by co-immunoprecipitation and pulldown assay in PC12 cells. NGF-stimulated FEZ1 co-localizes with mitochondria in neurites, and FEZ1 siRNA knockdown reduces anterograde mitochondrial motility, suggesting FEZ1/kinesin complex mediates mitochondrial transport along microtubules.\",\n      \"method\": \"Co-immunoprecipitation, pulldown assay, RNAi knockdown, live-cell imaging of mitochondrial motility in NGF-treated PC12 cells\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP and pulldown confirming FEZ1/KIF5 interaction, combined with RNAi functional validation of mitochondrial transport, replicated concept from PMID:17173861\",\n      \"pmids\": [\"17669366\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Lzts1 knockout MEFs show increased Cdc25C degradation during M phase, leading to decreased Cdk1 activity. This results in accelerated mitotic progression, resistance to taxol/nocodazole-induced M phase arrest, and improper chromosome segregation. Lzts1-deficient mice show increased incidence of spontaneous and carcinogen-induced cancers, establishing LZTS1 as a regulator of Cdk1/Cdc25C interaction during mitosis.\",\n      \"method\": \"Knockout mouse model, MEF isolation, Western blot for Cdc25C and Cdk1 activity, drug sensitivity assay, chromosome segregation analysis, tumor incidence monitoring\",\n      \"journal\": \"Cancer cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout with mechanistic dissection (Cdc25C stability, Cdk1 activity), multiple cellular phenotypes, in vivo tumor incidence data\",\n      \"pmids\": [\"17349584\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Neuronal FEZ1 expression (high in neurons, low in astrocytes/microglia) underlies intrinsic resistance to HIV-1 nuclear entry: siRNA knockdown of endogenous FEZ1 in neurons increases HIV-1 infectivity, while FEZ1 overexpression in microglia (sensitive cells) increases resistance. FEZ1 resistance is not IFN-inducible, defining it as a constitutive neuron-specific antiviral factor acting before nuclear entry.\",\n      \"method\": \"siRNA knockdown in primary neurons, FEZ1 overexpression in microglia, pseudotyped HIV-1 infection assay with quantification of early infection\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — bidirectional gain/loss-of-function with defined infectivity readout, single lab\",\n      \"pmids\": [\"19667186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"FEZ1 is a natively unfolded protein that dimerizes in solution. Small-angle X-ray scattering reveals an elongated dimeric shape; in vitro pulldown shows dimerization involves the N-terminus. PKC phosphorylates FEZ1 predominantly in its C-terminal region, and this phosphorylation inhibits FEZ1 interaction with the CLASP2-interacting domain in vitro, without major conformational changes.\",\n      \"method\": \"Circular dichroism, fluorescence spectroscopy, limited proteolysis, SAXS, in vitro pulldown, in vitro PKC phosphorylation assay\",\n      \"journal\": \"Proteins\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple biophysical methods (SAXS, CD, fluorescence) plus in vitro phosphorylation with functional consequence (inhibited CLASP2 interaction), single lab but orthogonal methods\",\n      \"pmids\": [\"18615714\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"FEZ1 forms an intermolecular disulfide bond through Cys-133 that is essential for dimerization, demonstrated in the fragment FEZ1(92-194), full-length recombinant FEZ1, and endogenous FEZ1 from HEK293 cells. This disulfide-mediated dimerization may enable FEZ1 to act as a bivalent transport adaptor.\",\n      \"method\": \"In vitro pulldown of recombinant FEZ1 fragments, mass spectrometry analysis, isolation of endogenous FEZ1 from HEK293 cells, disulfide bond identification\",\n      \"journal\": \"Journal of proteome research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and endogenous validation of disulfide bond, mass spectrometry identification of Cys-133, single lab\",\n      \"pmids\": [\"20812761\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"FEZ1 interacts with DISC1 to synergistically regulate dendritic growth of newborn neurons in the adult mouse hippocampus. This FEZ1-DISC1 pathway is parallel to and complementary with the DISC1-NDEL1 pathway that regulates cell positioning; epistasis analysis of two independent patient cohorts shows interaction between FEZ1 and DISC1 (but not FEZ1 and NDEL1) for schizophrenia risk.\",\n      \"method\": \"Co-immunoprecipitation, in vivo knockdown in adult mouse hippocampus, morphological analysis of newborn neurons, genetic epistasis analysis in two patient cohorts\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo functional epistasis (parallel pathway dissection) combined with co-IP and two independent human cohort genetic epistasis analyses\",\n      \"pmids\": [\"22099459\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"FEZ1 forms a stable complex with SCOCO (UNC-69 homolog) through coiled-coil interactions. Structural analysis by NMR, crosslinking-MS, and SAXS shows FEZ1(92-194) homodimerizes in antiparallel topology, and the FEZ1/SCOCO interaction interface is consistent with the UNC-76/UNC-69 interaction. A heterotetrameric complex model is supported by SAXS.\",\n      \"method\": \"NMR, cross-linking coupled with mass spectrometry, SAXS, molecular modelling, in vitro complex formation\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — multiple structural/biophysical methods (NMR, crosslink-MS, SAXS) converging on same interaction interface, single lab\",\n      \"pmids\": [\"24116125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"SCOCO forms a parallel left-handed coiled-coil dimer and forms a stable homogeneous complex with the coiled-coil domain of FEZ1. SCOCO dimerization and surface residue R117 are important for the SCOCO-FEZ1 interaction, established by crystal structure determination and mutagenesis.\",\n      \"method\": \"X-ray crystallography of SCOCO coiled-coil domain at 2.7 Å, site-directed mutagenesis (E93V/K97L and N125L/N132V double mutants), multi-angle laser light scattering, native mass spectrometry, in vitro complex formation assay\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure plus mutagenesis plus orthogonal biophysical validation (MALS, native MS), single lab\",\n      \"pmids\": [\"24098481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Cdc20/APC (anaphase-promoting complex) ubiquitin ligase controls dendrite growth in neurons by targeting FEZ1 for degradation. BubR1 modulates Cdc20/APC activity and thereby FEZ1 levels; BubR1 is deacetylated by HDAC11, which disinhibits Cdc20/APC. This pathway operates in hippocampal dentate granule cells and olfactory bulb neurons.\",\n      \"method\": \"Overexpression and knockdown of Cdc20/APC and BubR1 in neurons, ubiquitin-mediated degradation assay, dendrite morphology analysis, acetylation status analysis of BubR1\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — gain/loss-of-function of multiple pathway components with defined morphological readout (dendrite growth), single lab\",\n      \"pmids\": [\"24726361\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"HIV-1 associates with the kinesin-1 adaptor FEZ1; RNAi depletion of FEZ1 blocks early HIV-1 infection with virus showing bidirectional but no net movement toward the nucleus. The ability of exogenously expressed FEZ1 to promote HIV-1 infection requires its binding to kinesin-1. Both dynein and kinesin-1 are required for HIV-1 trafficking to the nucleus.\",\n      \"method\": \"RNAi knockdown, live-cell single-particle tracking of HIV-1 particles, exogenous expression of FEZ1 variants (including kinesin-1 binding mutants), early infection assay\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — bidirectional RNAi and rescue with binding-mutant FEZ1 defining kinesin-1 dependency, combined with quantitative live-cell particle tracking\",\n      \"pmids\": [\"25818806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"MARK/PAR-1 kinases phosphorylate FEZ1 at serine 58, regulating its function as a kinesin-1 adapter for presynaptic cargo transport. Loss of MARK/PAR-1 causes FEZ1, kinesin-1, and presynaptic cargoes to co-aggregate in cell bodies and axons instead of being transported. Unphosphorylated FEZ1 co-aggregates with kinesin-1 and cargoes are also found in Alzheimer's disease model mouse brains.\",\n      \"method\": \"Phosphorylation assay, mass spectrometry identification of phosphorylation site, MARK/PAR-1 loss-of-function in neurons, immunofluorescence, live-cell imaging, analysis of transgenic AD mouse brain\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — phosphorylation site identified by mass spectrometry, loss-of-function with specific transport phenotype, replicated in disease model, multiple orthogonal methods\",\n      \"pmids\": [\"27247180\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In C. elegans, UNC-76/FEZ1 and UNC-16/JIP3 limit mitochondrial density in neuronal processes by maintaining the balance of anterograde and retrograde mitochondrial transport. unc-76 mutants show increased mitochondrial density, elevated kinesin heavy and light chain levels in neurons, and a net anterograde bias in mitochondrial flux that is partly dependent on dynein.\",\n      \"method\": \"Genetic loss-of-function (unc-76 mutants), live-cell fluorescence imaging of mitochondrial transport, quantification of mitochondrial density and flux, genetic epistasis with dynein mutants\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function with quantitative live-cell transport imaging and epistasis with dynein, single lab\",\n      \"pmids\": [\"29895958\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FEZ1 directly interacts with HIV-1 capsid protein (CA) hexamers, specifically binding through acidic poly-glutamate stretches to the positively charged central pore of CA hexamers. This interaction competes with nucleotides and inositol hexaphosphate (IP6) at the same site. Mutation of FEZ1 capsid-interacting residues significantly reduces HIV-1 trafficking toward the nucleus and early infection.\",\n      \"method\": \"Direct binding assay, all-atom molecular dynamics simulations, competition assay with IP6/nucleotides, site-directed mutagenesis of FEZ1 interacting residues, single-particle HIV-1 trafficking assay, early infection assay\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — direct binding defined with MD simulation and mutagenesis, competition assay establishing binding site, functional validation by trafficking and infection assay, multiple orthogonal methods\",\n      \"pmids\": [\"31422020\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"FEZ1 forms a complex with CRMP1 at neuronal growth cones and is required for axonal development; FEZ1 deficiency causes growth cone collapse and impaired axonal development similar to CRMP1 loss. Separately, FEZ1 forms a complex with DCC and Syntaxin-1 (components of the Netrin-1 signaling pathway), and FEZ1-deficient neurons fail to respond to Netrin-1 or Sema3A guidance cues.\",\n      \"method\": \"Co-immunoprecipitation, co-localization imaging, loss-of-function (FEZ1 deficiency) in rat hippocampal neurons, axon/dendrite morphology analysis, guidance cue response assay (Netrin-1, Sema3A)\",\n      \"journal\": \"eNeuro\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — co-IP identifies complexes, loss-of-function shows defined morphological and signaling phenotype, single lab\",\n      \"pmids\": [\"33771901\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"FEZ1 deletion in rat motor neurons strongly impairs axon and dendrite development and significantly delays synaptic protein transport into developing neurites. Drosophila unc-76 mutants show severe locomotion impairment and reduced synaptic boutons at neuromuscular junctions. Pharmacological activation of UNC-51/ATG1 (a FEZ1-activating kinase) with rapamycin and metformin ameliorates these defects.\",\n      \"method\": \"FEZ1 deletion in human ES-derived and rat neurons, neurite morphology analysis, synaptic protein transport assay, Drosophila unc-76 genetic analysis, pharmacological rescue with rapamycin/metformin\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic loss-of-function across two model systems with defined cellular and synaptic phenotypes, pharmacological rescue, single lab\",\n      \"pmids\": [\"33395696\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FEZ1 interacts with the retinoic acid receptor (RAR) through its coiled-coil region (interacting with the ligand-binding domain of RAR). In the presence of retinoic acid, FEZ1 induces hoxb4 gene expression, demonstrating a role in transcriptional regulation.\",\n      \"method\": \"In vitro binding assay, co-immunoprecipitation, interaction interface mapping, 86-gene panel expression assay in cells co-expressing FEZ1 and RAR\",\n      \"journal\": \"FEBS open bio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — in vitro binding and co-IP plus functional gene expression readout, single lab, single gene target confirmed\",\n      \"pmids\": [\"29321952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"FEZ1 interacts with NEK1 and CLASP2 through coiled-coil interactions in vitro, and all three proteins co-localize with gamma-tubulin in a perinuclear/centrosomal region in mammalian cells. FEZ1/CLASP2 co-localization is inhibited by PMA treatment, and CLASP2 is phosphorylated by active PKC isoforms, suggesting PKC regulates FEZ1/CLASP2 centrosomal complex.\",\n      \"method\": \"In vitro pulldown (coiled-coil interactions), co-localization imaging, PMA treatment, PKC phosphorylation assay\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — in vitro pulldown and co-localization, single lab, no loss-of-function validation of centrosomal function\",\n      \"pmids\": [\"19924516\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SCOC, ULK1, and NBR1 directly bind to FEZ1 protein to form a protein complex, as demonstrated by immunoprecipitation. All four proteins (FEZ1/SCOC/ULK1/NBR1) are targets of miR-129-5p, and their expression is regulated coordinately in neuronal autophagy.\",\n      \"method\": \"Immunoprecipitation, dual-luciferase reporter system (miR-129-5p target validation), overexpression/interference of miR-129-5p in neuronal cells\",\n      \"journal\": \"Bioengineered\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single immunoprecipitation assay, single lab, limited mechanistic follow-up on complex function\",\n      \"pmids\": [\"35435132\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"FEZ1 (UNC-76) is a kinesin-1 adaptor protein that forms an elongated dimer (stabilized by a Cys-133 disulfide bond) and mediates anterograde axonal transport of mitochondria and presynaptic cargo by binding KIF5/kinesin-1 and tubulin; its transport activity is regulated by phosphorylation at Ser58 by MARK/PAR-1 kinases and by PKCzeta (which also promotes neuronal differentiation), and its stability is controlled by Cdc20/APC-mediated ubiquitin-proteasomal degradation; at the cell cycle level, FEZ1 stabilizes Cdc25C to maintain Cdk1 activity during mitosis, and it also acts as a capsid-associated host factor exploited by HIV-1 for inward nuclear trafficking by binding the central pore of CA hexamers via acidic poly-glutamate stretches.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"FEZ1 (fasciculation and elongation protein zeta-1, ortholog of C. elegans UNC-76) is a kinesin-1 adaptor that drives anterograde microtubule-based transport in neurons and controls axonal outgrowth, fasciculation, and neuronal polarity [#0, #3, #8]. It is a natively unfolded, elongated dimer whose self-association requires its N-terminus and an intermolecular Cys-133 disulfide bond, configuring it as a bivalent transport adaptor [#13, #14]. Through its C-terminal coiled-coil region FEZ1 binds the kinesin heavy chain tail and tubulin and recruits cargoes—mitochondria and presynaptic components—for delivery into developing neurites, so that its loss stalls anterograde mitochondrial movement and synaptic protein transport [#3, #10, #19, #24]. Transport activity is set by phosphorylation: MARK/PAR-1 kinases phosphorylate FEZ1 at Ser58 to license cargo movement, and loss of this control causes FEZ1, kinesin-1, and presynaptic cargoes to co-aggregate in cell bodies and axons, a state also seen in Alzheimer's disease model brains [#20]. FEZ1 is also a PKCzeta substrate that, together with active PKCzeta and E4B-mediated Lys27 polyubiquitylation, promotes neuronal differentiation and neurite extension [#1, #4], and it acts within DISC1, CRMP1, and Netrin-1/DCC-Syntaxin-1 signaling modules to support dendritic and axonal development and guidance-cue responses [#15, #23]. Independently, the FEZ1/LZTS1 product functions in mitosis, where it associates with microtubules and Cdk1 and stabilizes Cdc25C to sustain Cdk1 activity; its loss accelerates mitosis, causes chromosome missegregation, and predisposes to tumors [#2, #11]. FEZ1 additionally serves as a constitutive, neuron-enriched host factor for HIV-1: it binds the central pore of capsid hexamers through acidic poly-glutamate stretches and links the incoming capsid to kinesin-1 for inward trafficking toward the nucleus [#12, #19, #22].\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Established FEZ1's ancestral function by showing its C. elegans ortholog UNC-76 is required for axon bundling and elongation, with human FEZ1 able to rescue the defect—defining a conserved role in axonal outgrowth.\",\n      \"evidence\": \"Genetic loss-of-function and cross-species complementation in C. elegans\",\n      \"pmids\": [\"9096408\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular partners and biochemical activity unresolved\", \"No mechanism for how the protein supports outgrowth\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Identified FEZ1 as a PKCzeta substrate and effector, linking it to a kinase signal that triggers cytoplasmic translocation and drives neuronal differentiation.\",\n      \"evidence\": \"Yeast two-hybrid, co-IP, phosphorylation assay, and PC12 differentiation assay\",\n      \"pmids\": [\"9971736\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Phosphorylation sites not mapped\", \"Downstream effect of phosphorylation on cargo binding not defined\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Connected FEZ1/LZTS1 to the cell cycle, showing PKA-dependent hyperphosphorylation, association with microtubules and p34cdc2, and tumor-suppressor activity with G2/M accumulation.\",\n      \"evidence\": \"Co-IP, phosphorylation assay, nude mouse tumor suppression and FACS cell-cycle analysis\",\n      \"pmids\": [\"11504921\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct molecular target in the cell cycle not yet identified\", \"Relationship between neuronal and mitotic roles unclear\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Placed FEZ1/UNC-76 directly in the kinesin-1 axonal transport pathway by demonstrating direct binding to the kinesin heavy chain tail plus dosage-sensitive genetic interactions.\",\n      \"evidence\": \"Yeast two-hybrid, copurification, and genetic epistasis with Khc/Klc in Drosophila\",\n      \"pmids\": [\"12925768\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific cargoes transported not identified\", \"Regulation of the FEZ1–kinesin interaction unknown\"]\n    },\n    {\n      \"year\": 2004,\n      \"claim\": \"Showed E4B ubiquitin ligase polyubiquitylates FEZ1 on Lys27 of ubiquitin in a non-degradative manner required for neuritogenesis, defining a PKCzeta-enhanced regulatory modification.\",\n      \"evidence\": \"In vitro ubiquitylation, co-IP, and dominant-negative E4B neurite outgrowth assay in PC12 cells\",\n      \"pmids\": [\"15466860\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of K27 linkage on FEZ1 activity not defined\", \"Whether this regulates transport vs differentiation unclear\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that FEZ1's microtubule association underlies neurite extension and is targeted by JC virus agnoprotein, which dissociates FEZ1 from microtubules.\",\n      \"evidence\": \"In vitro binding, microtubule cosedimentation, and neurite/viral assays\",\n      \"pmids\": [\"15843383\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Microtubule-binding interface not mapped\", \"Relationship to kinesin-1 binding not resolved\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Defined FEZ1 as a retroviral restriction factor acting after reverse transcription but before nuclear entry, the first link to viral nuclear trafficking.\",\n      \"evidence\": \"Expression profiling, retroviral infection with viral DNA quantification, and RNAi knockdown\",\n      \"pmids\": [\"15879557\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular mechanism of the block undefined\", \"Direct viral binding partner not identified\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Mapped FEZ1's C-terminal coiled-coil as the hub for homodimerization, FEZ2 heterodimerization, and binding to transcriptional regulators, broadening its interactome.\",\n      \"evidence\": \"Yeast two-hybrid screen with in vitro pulldown confirmation and deletion mapping\",\n      \"pmids\": [\"16484223\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional significance of transcriptional-regulator interactions untested\", \"Cellular relevance of FEZ1/FEZ2 heterodimers unknown\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Linked FEZ1 directly to mitochondrial transport and neuronal polarity, showing knockdown represses axon formation and slows anterograde mitochondrial movement.\",\n      \"evidence\": \"RNAi and live mitochondrial imaging in rat hippocampal neurons\",\n      \"pmids\": [\"17173861\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Adaptor that couples FEZ1 to mitochondria not identified here\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Identified the conserved UNC-69/UNC-76 complex regulating axon extension, fasciculation, and presynaptic organization, extending FEZ1 function into synaptic assembly.\",\n      \"evidence\": \"Yeast two-hybrid, in vivo colocalization, and double-mutant genetics in C. elegans\",\n      \"pmids\": [\"16725058\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biochemical role of the complex in transport not defined\", \"Human SCOCO equivalence not established here\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Resolved the molecular adaptor link by showing FEZ1 associates with KIF5/kinesin-1 and tubulin and is required for anterograde mitochondrial motility in neurites.\",\n      \"evidence\": \"Co-IP, pulldown, RNAi, and live imaging in NGF-treated PC12 cells\",\n      \"pmids\": [\"17669366\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct mitochondrial receptor unidentified\", \"How phosphorylation gates the KIF5 interaction not addressed\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Established the mitotic mechanism of LZTS1/FEZ1: knockout MEFs degrade Cdc25C, lower Cdk1 activity, missegregate chromosomes, and mice develop cancers, defining a Cdk1/Cdc25C regulatory role.\",\n      \"evidence\": \"Knockout mouse, MEF analysis, Cdk1 activity assays, and tumor incidence\",\n      \"pmids\": [\"17349584\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct biochemical mechanism of Cdc25C stabilization undefined\", \"Integration with neuronal transport role unresolved\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Characterized FEZ1 biophysically as an elongated, natively unfolded dimer and showed PKC phosphorylates its C-terminus to inhibit CLASP2 binding, linking conformation-independent phosphoregulation to partner selection.\",\n      \"evidence\": \"CD, fluorescence, limited proteolysis, SAXS, and in vitro PKC phosphorylation\",\n      \"pmids\": [\"18615714\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional consequence of CLASP2 inhibition in cells not tested\", \"Precise phosphosites not mapped here\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined neuron-specific FEZ1 expression as the basis for constitutive, IFN-independent resistance to HIV-1 nuclear entry, demonstrated bidirectionally.\",\n      \"evidence\": \"siRNA in primary neurons and FEZ1 overexpression in microglia with HIV-1 infection assays\",\n      \"pmids\": [\"19667186\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular target on the virus not yet identified\", \"Reconciliation with pro-trafficking role came only later\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Identified the Cys-133 intermolecular disulfide as essential for FEZ1 dimerization, providing a structural basis for bivalent adaptor function.\",\n      \"evidence\": \"In vitro and endogenous pulldowns with mass spectrometry disulfide mapping\",\n      \"pmids\": [\"20812761\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Redox regulation of dimerization in vivo untested\", \"Relationship to N-terminal dimerization interface unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Placed FEZ1 in a DISC1-dependent pathway controlling dendritic growth of adult-born neurons and linked the interaction to schizophrenia risk in human cohorts.\",\n      \"evidence\": \"Co-IP, in vivo hippocampal knockdown, and genetic epistasis in two patient cohorts\",\n      \"pmids\": [\"22099459\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which DISC1 modulates FEZ1 transport activity undefined\", \"Causal variant not identified\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Provided structural definition of the FEZ1 coiled-coil, showing antiparallel homodimerization and a heterotetrameric FEZ1/SCOCO complex, the human counterpart of UNC-76/UNC-69.\",\n      \"evidence\": \"NMR, crosslinking-MS, SAXS, and modelling (with companion SCOCO crystal structure and mutagenesis)\",\n      \"pmids\": [\"24116125\", \"24098481\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional role of the FEZ1/SCOCO tetramer in transport not assayed\", \"Stoichiometry in cells not confirmed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showed Cdc20/APC ubiquitin ligase targets FEZ1 for degradation to limit dendrite growth, with BubR1/HDAC11 controlling APC activity—defining proteolytic control of FEZ1 levels in neurons.\",\n      \"evidence\": \"Gain/loss-of-function of APC components, degradation assays, and dendrite morphology\",\n      \"pmids\": [\"24726361\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Degron on FEZ1 not mapped\", \"Interplay with non-degradative E4B ubiquitylation unresolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Reversed the antiviral picture by demonstrating FEZ1 promotes early HIV-1 infection as a kinesin-1 adaptor, with depletion causing bidirectional but non-productive viral movement.\",\n      \"evidence\": \"RNAi, single-particle tracking, and rescue with kinesin-1-binding mutants\",\n      \"pmids\": [\"25818806\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct viral binding site not yet defined here\", \"Determinants of net directionality with dynein unresolved\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identified Ser58 as the MARK/PAR-1 phosphosite that licenses FEZ1's kinesin-1 adaptor function for presynaptic cargo, with loss causing pathological co-aggregation also seen in Alzheimer's models.\",\n      \"evidence\": \"Mass spectrometry phosphosite mapping, MARK/PAR-1 loss-of-function, imaging, and AD mouse brain analysis\",\n      \"pmids\": [\"27247180\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How Ser58 phosphorylation alters cargo affinity mechanistically undefined\", \"Causal role in disease aggregation not established\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Demonstrated FEZ1/UNC-76 limits neuronal mitochondrial density by balancing anterograde and retrograde transport, refining its role beyond simple anterograde delivery.\",\n      \"evidence\": \"C. elegans genetics, quantitative live transport imaging, and dynein epistasis\",\n      \"pmids\": [\"29895958\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which FEZ1 affects motor levels unknown\", \"Direct coupling to dynein not established\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Resolved the molecular basis of FEZ1-HIV-1 capsid engagement: acidic poly-glutamate stretches bind the positively charged CA hexamer central pore, competing with IP6/nucleotides, and are required for nuclear trafficking.\",\n      \"evidence\": \"Direct binding, MD simulation, IP6 competition, mutagenesis, and single-particle trafficking\",\n      \"pmids\": [\"31422020\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether capsid binding alters normal cellular cargo handling unknown\", \"Structural complex not determined experimentally\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Embedded FEZ1 in growth-cone guidance machinery, showing it complexes with CRMP1 and with DCC/Syntaxin-1 and is required for Netrin-1 and Sema3A responses.\",\n      \"evidence\": \"Co-IP, colocalization, and loss-of-function guidance assays in rat hippocampal neurons\",\n      \"pmids\": [\"33771901\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether transport vs scaffolding underlies guidance defects unclear\", \"Single-lab finding\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed FEZ1 deletion impairs axon/dendrite development and delays synaptic protein transport across model systems, with pharmacological UNC-51/ATG1 activation rescuing defects—pointing to a druggable kinase upstream.\",\n      \"evidence\": \"FEZ1 deletion in human ES-derived and rat neurons, Drosophila genetics, and rapamycin/metformin rescue\",\n      \"pmids\": [\"33395696\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How UNC-51/ATG1 activates FEZ1 mechanistically undefined\", \"Site of ATG1 regulation on FEZ1 not mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How FEZ1's distinct roles—neuronal kinesin-1 transport, mitotic Cdc25C/Cdk1 regulation, transcriptional partnerships, and viral capsid binding—are coordinated within a single protein, and how its multiple phosphorylation and ubiquitylation events are integrated, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No unified model linking transport and cell-cycle functions\", \"Phospho-/ubiquitin code controlling cargo selection not deciphered\", \"No high-resolution structure of FEZ1 bound to kinesin-1 or cargo\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [3, 10, 19, 20]},\n      {\"term_id\": \"GO:0008092\", \"supporting_discovery_ids\": [2, 5, 10]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [1, 5]},\n      {\"term_id\": \"GO:0005856\", \"supporting_discovery_ids\": [2, 5, 10]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [26]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-9609507\", \"supporting_discovery_ids\": [3, 10, 19, 24]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 8, 15, 23]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [2, 11]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [12, 19, 22]}\n    ],\n    \"complexes\": [\n      \"FEZ1/SCOCO (UNC-76/UNC-69) complex\",\n      \"FEZ1-kinesin-1 (KIF5) transport complex\"\n    ],\n    \"partners\": [\n      \"KIF5\",\n      \"PRKCZ\",\n      \"SCOC\",\n      \"DISC1\",\n      \"CLASP2\",\n      \"CRMP1\",\n      \"DCC\",\n      \"RARA\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}