LINGO2

LINGO2 is a transmembrane leucine-rich repeat/Ig-domain cell-surface receptor that couples the trefoil factor TFF3 to EGFR-dependent cytoprotective signaling and that independently shapes neuronal synapse biology and neurodegenerative pathology (PMID:31562318, PMID:39443477, PMID:40169805). At epithelial surfaces LINGO2 forms an inhibitory complex with EGFR; TFF3 binding to LINGO2 disrupts this complex, de-repressing EGFR signaling to block apoptosis and promote wound healing (PMID:31562318), and the same TFF3-LINGO2 axis drives EGFR/Src activation and Bcl-2 induction to confer neuroprotection in ischemic brain (PMID:37935323). In T cells the TFF3-LINGO2 interaction restrains IFNγ+ TH1 expansion and favors TH2 commitment, enabling type-2 immunity and helminth clearance (PMID:38336020). Beyond receptor signaling, LINGO2 contributes to neuronal connectivity: its ectodomain is shed by ADAM10 to yield a soluble fragment (sLingo2) that organizes excitatory synapses and increases excitatory transmission (PMID:39443477). In Alzheimer's disease models LINGO2 levels are set post-transcriptionally by Mettl3-mediated m6A modification, which recruits Ythdf2 to degrade Lingo2 mRNA; reduced LINGO2 enhances APP–Bace1 interaction and Aβ production, and loss of LINGO2 mediates APP-driven neurite and transcriptional deficits (PMID:38918213, PMID:40169805). In gastric cancer LINGO2 promotes AKT/ERK/MEK signaling, EMT, and a CD44+ stem-like population (PMID:30696080).

1. 2019 High

   Established LINGO2 as a TFF3 receptor that gates EGFR signaling, answering how the secreted trefoil factor TFF3 transduces a cytoprotective signal at the epithelial surface.

   Evidence Reciprocal co-IP, co-localization, and Lingo2-deficient mice with colitis/helminth and apoptosis readouts in intestinal epithelium

   PMID:31562318

   Open questions at the time

   • Structural basis of the LINGO2-EGFR inhibitory complex unresolved
   • Stoichiometry and direct vs. indirect nature of LINGO2-EGFR contact not defined
2. 2019 Medium

   Showed LINGO2 drives pro-tumorigenic kinase signaling, extending its functional reach beyond epithelial repair into cancer.

   Evidence siRNA knockdown in gastric cancer cell lines with phospho-kinase, EMT/stemness marker, and tumorigenicity readouts

   PMID:30696080

   Open questions at the time

   • No upstream binding partner or direct mechanism linking LINGO2 to AKT/ERK/MEK established
   • Relationship to the EGFR axis not tested
3. 2023 Medium

   Generalized the TFF3-LINGO2-EGFR axis to the CNS, showing it mediates TFF3 neuroprotection after ischemic stroke.

   Evidence Co-IP, intracerebroventricular siRNA knockdown, EGFR inhibitor pharmacology, and behavioral assays in a rat MCAO model

   PMID:37935323

   Open questions at the time

   • Single-lab pharmacology and knockdown
   • Cell types in brain mediating the axis not resolved
4. 2024 Medium

   Defined a distinct LINGO2 function in synapse formation via regulated ectodomain shedding, separating its receptor role from a secreted synaptogenic role.

   Evidence Secretome analysis, ADAM10 sheddase identification, synaptogenesis assays in mouse and human neurons, and mEPSC electrophysiology

   PMID:39443477

   Open questions at the time

   • Postsynaptic receptor/partner for sLingo2 unknown
   • Relationship between shedding and EGFR signaling not addressed
5. 2024 Medium

   Implicated LINGO2 as a downstream effector of APP-driven neurodegeneration, showing its loss rescues familial AD neuronal phenotypes.

   Evidence LINGO2 knockdown in isogenic APPV717I iPSC-derived neurons with neurite outgrowth, snRNA-seq rescue, and xenograft models

   PMID:38918213

   Open questions at the time

   • Mechanism linking APP to LINGO2 not defined in this study
   • Direction of effect appears opposite to the m6A study and is not reconciled
6. 2024 High

   Demonstrated a cell-autonomous role for LINGO2 in T cells, showing TFF3-LINGO2 signaling restrains TH1 expansion to permit type-2 immunity.

   Evidence T cell-specific conditional Lingo2 knockout in Trichuris muris infection with TH1/TH2 flow cytometry and IFNγ blockade epistasis

   PMID:38336020

   Open questions at the time

   • Downstream signaling in T cells (EGFR involvement) not shown
   • Direct TFF3-LINGO2 binding in T cells not biochemically confirmed
7. 2025 High

   Established epitranscriptomic control of LINGO2 and connected its levels to amyloid processing, answering how LINGO2 abundance is regulated and how it modulates Aβ production.

   Evidence m6A-seq/MeRIP, Ythdf2 binding, APP-Bace1 co-IP, Mettl3 knockout/knock-in mice, Lingo2 overexpression, and STM2457 in 5xFAD mice

   PMID:40169805

   Open questions at the time

   • Molecular mechanism by which LINGO2 restrains APP-Bace1 interaction unknown
   • Apparent contradiction with iPSC study where LINGO2 loss is protective not reconciled

• Whether LINGO2's epithelial/T-cell receptor role, its synaptogenic shed-ectodomain role, and its amyloid-modulating role share a unifying biochemical mechanism remains unknown.
• No structure of LINGO2 or its complexes
• Opposing directionality of LINGO2 effects across AD models unresolved
• Whether EGFR signaling underlies the synaptic and neurodegenerative phenotypes untested