NEO1

NEO1 (neogenin) is a multidomain transmembrane receptor that transduces axon guidance and morphogenetic cues to control neural development, epithelial fate, and tissue barrier integrity (PMID:33740419, PMID:32231305). Its ectodomain comprises four immunoglobulin-like domains and six fibronectin type III repeats followed by a transmembrane and intracellular segment, with isoform diversity generated by alternative splicing of the intracellular domain (PMID:9169140). NEO1 simultaneously engages Netrin-1 and RGM ligands, assembling a ternary NEO1-NET1-RGM complex that oligomerizes into a 'trimer-of-trimers' super-assembly; this higher-order arrangement is inhibitory, blocking RGMA-NEO1 growth cone collapse and NET1- or RGMA-driven neuron migration by preventing formation of signaling-competent receptor clusters (PMID:33740419). Productive Netrin-1-NEO1 signaling activates focal adhesion kinase (FAK): in embryonic stem cells, with co-receptor UNC5B, this inactivates GSK3α/β to stabilize β-catenin and dampens ERK1/2 via a PPP2R2C-PP2A complex to promote naive pluripotency (PMID:32231305), while in pancreatic epithelium FAK activation upregulates ZEB1 and SOX9 to drive epithelial-mesenchymal transition and cancer stemness (PMID:41474982). RGM-induced glycosylation and intramembrane proteolysis of NEO1 release a nuclear intracellular fragment (NeoICD) required for neuroepithelial cell elongation and neural tube morphogenesis (PMID:31399534). In astrocytes, NEO1 maintains blood-brain barrier integrity and governs inflammatory A1 polarization after subarachnoid hemorrhage through a cPLA2-MAVS-NF-κB pathway (PMID:39107268, PMID:41345945).

1. 1997 Medium

   Established the domain architecture of human neogenin, defining it as an Ig/FnIII-containing transmembrane receptor with splice variation in its intracellular domain.

   Evidence cDNA cloning, sequencing, and Northern blot of human NEO1

   PMID:9169140

   Open questions at the time

   • No ligand or signaling partner identified at this stage
   • Functional role of intracellular splice isoforms not resolved
2. 2015 Low

   Implicated nuclear translocation of neogenin as functionally important by showing an NLS missense variant abolishes nuclear import.

   Evidence Functional NLS-mutant nuclear translocation assay with in silico prediction

   PMID:26518331

   Open questions at the time

   • Single-variant functional assay with limited methodological detail
   • Downstream consequences of failed nuclear import not characterized
   • Link to a physiological phenotype not established
3. 2019 Medium

   Connected RGM ligand to regulated intramembrane proteolysis, showing the released NeoICD fragment is the morphogenetic effector for neural tube development.

   Evidence Zebrafish morpholino knockdown, cell transplantation, and NeoICD overexpression rescue

   PMID:31399534

   Open questions at the time

   • Protease responsible for cleavage not identified
   • Nuclear targets of NeoICD unknown
   • Only partial rescue achieved by NeoICD
4. 2020 High

   Defined a productive Netrin-1-NEO1 signaling output, coupling NEO1 to FAK-GSK3-β-catenin and, via UNC5B, to PP2A-ERK modulation to control stem cell pluripotency.

   Evidence mESC 2i/LIF culture, receptor knockdown/overexpression, kinase and phosphatase assays, Co-IP, replicated in human ESCs

   PMID:32231305

   Open questions at the time

   • Stoichiometry of NEO1/UNC5B receptor partitioning not resolved
   • Direct FAK-NEO1 contact not structurally defined
5. 2021 High

   Provided the structural basis for ligand integration, showing NEO1 binds NET1 and RGM simultaneously into an inhibitory super-complex that suppresses guidance signaling.

   Evidence X-ray crystallography, cryo-EM, growth cone collapse and neuron migration assays with mutagenesis

   PMID:33740419

   Open questions at the time

   • In vivo prevalence of the super-complex versus signaling-competent complexes unquantified
   • How clustering state is set in physiological membranes unknown
6. 2024 Medium

   Extended NEO1 function beyond neurons, showing astrocytic NEO1 is required for blood-brain barrier integrity after hemorrhage.

   Evidence Astrocyte GFAP-Cre conditional knockout, BBB leakage assays, TEM, SAH mouse model

   PMID:39107268

   Open questions at the time

   • Molecular link between NEO1 and endothelial proliferation not defined
   • Mechanism of hepcidin rescue unresolved
7. 2025 Medium

   Identified the inflammatory pathway downstream of astrocytic NEO1, placing it upstream of cPLA2-MAVS-NF-κB to drive A1 astrocyte polarization.

   Evidence Astrocyte conditional knockout, transcriptomics, lentiviral cPLA2 rescue, SAH model

   PMID:41345945

   Open questions at the time

   • Direct biochemical link between NEO1 receptor and cPLA2 induction not shown
   • Ligand triggering this astrocytic pathway unidentified
8. 2026 Medium

   Showed NEO1 mediates Netrin-1-driven epithelial-mesenchymal transition and cancer stemness in pancreatic tissue via FAK-ZEB1/SOX9, and supports sympathetic axonogenesis.

   Evidence Pancreatic organoids, KrasG12D mice, NEO1 KO/knockdown, NTN1 treatment and neutralizing antibody, ex vivo ganglia culture

   PMID:41474982

   Open questions at the time

   • Whether super-complex formation modulates this oncogenic signaling untested
   • Contribution of UNC5B co-receptor in this context unknown
9. 2025 Medium

   Defined a phospholipid flippase activity for the yeast ortholog Neo1, capturing PI4P in the substrate translocation pathway by cryo-EM and linking flippase loss to extracellular PI4P-mediated drug uptake.

   Evidence Cryo-EM with bound PI4P, yeast mutant and neomycin sensitivity assays, Sac1 epistasis (preprint)

   Open questions at the time

   • Activity demonstrated for yeast Neo1, not human NEO1
   • Preprint, not peer-reviewed
   • Relationship between flippase function and the receptor signaling roles of vertebrate NEO1 unestablished

• How the structurally defined inhibitory super-complex is dynamically converted to productive FAK-coupled signaling in vivo, and whether vertebrate NEO1 retains any lipid-handling activity, remain open.
• No structure of the active signaling-competent NEO1 complex with FAK
• Protease and nuclear NeoICD targets unidentified
• Flippase activity not demonstrated for human NEO1