LGI1 (Leucine-Rich Glioma Inactivated 1) encodes a secreted neuronal protein that serves as a critical regulator of synaptic transmission and neuronal excitability. Originally identified as a tumor suppressor gene in gliomas, LGI1 has emerged as a crucial component of synaptic function through its interactions with ADAM22 and ADAM23 receptor proteins["@scheel2002"]PMID: 16467533. Located at chromosome 10q24.3, LGI1 plays essential roles in AMPA receptor trafficking, synaptic plasticity, and cognitive function. The gene is implicated in autosomal dominant lateral temporal epilepsy (ADLTE), Alzheimer's disease, and prion disease pathogenesis["@yuan2012"]PMID: 31229456.
LGI1 (Leucine-Rich Glioma Inactivated 1) encodes a secreted neuronal protein that serves as a critical regulator of synaptic transmission and neuronal excitability. Originally identified as a tumor suppressor gene in gliomas, LGI1 has emerged as a crucial component of synaptic function through its interactions with ADAM22 and ADAM23 receptor proteins["@scheel2002"]PMID: 16467533. Located at chromosome 10q24.3, LGI1 plays essential roles in AMPA receptor trafficking, synaptic plasticity, and cognitive function. The gene is implicated in autosomal dominant lateral temporal epilepsy (ADLTE), Alzheimer's disease, and prion disease pathogenesis["@yuan2012"]PMID: 31229456.
<div class="infobox infobox-gene">
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<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">LGI1 — Leucine-Rich Glioma Inactivated 1</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>LGI1</td></tr>
<tr><td><strong>Full Name</strong></td><td>Leucine-Rich Glioma Inactivated 1</td></tr>
<tr><td><strong>Chromosomal Location</strong></td><td>10q24.3</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td><a href="https://www.ncbi.nlm.nih.gov/gene/2709" target="_blank">2709</a></td></tr>
<tr><td><strong>OMIM</strong></td><td><a href="https://www.omim.org/entry/604619" target="_blank">604619</a></td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000162711</td></tr>
<tr><td><strong>UniProt ID</strong></td><td><a href="https://www.uniprot.org/uniprot/O75771" target="_blank">O75771</a></td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>[Autosomal Dominant Lateral Temporal Epilepsy](/diseases/temporal-lobe-epilepsy), [Alzheimer's Disease](/diseases/alzheimers-disease), [Prion Disease](/diseases/prion-disease), [ALS](/diseases/amyotrophic-lateral-sclerosis)</td></tr>
</table>
</div>
LGI1 is a secreted protein of 557 amino acids with a distinctive domain organization: PMID: 16467533
Leucine-rich repeats (LRR): The N-terminal region contains multiple LRR motifs that mediate protein-protein interactions and are crucial for receptor binding.
Cystatin-like domain: The C-terminal portion contains a cystatin-like domain that contributes to protein stability and may have protease inhibitor activity.
Signal peptide: A signal peptide sequence directs LGI1 to the secretory pathway, enabling its function as a synaptic signaling molecule.
Secreted nature: LGI1 is secreted from neurons and acts in a paracrine or autocrine manner on postsynaptic receptors.
LGI1 belongs to a family of LGI-related proteins:
LGI2: Closest homolog with partially overlapping functions
LGI3: Expressed in brain with potential roles in neuronal function
LGI4: Involved in peripheral nerve development
This family shares structural features but has distinct expression patterns and functions. PMID: 31229456
LGI1 exhibits specific expression in the central nervous system:
PMID: 30283395
Within neurons, LGI1 is localized to:
LGI1 functions by binding to ADAM (A Disintegrin And Metalloproteinase) receptor proteinsPMID: 16467533PMID: 30867319:
PMID: 15199738
ADAM22: The primary LGI1 receptor, localized to postsynaptic membranes of excitatory synapses. ADAM22 is a receptor with no catalytic activity, functioning primarily as a scaffold.
ADAM23: Expressed in brain with overlapping functions with ADAM22
Interaction mechanism: LGI1 acts as a bridging molecule between presynaptic and postsynaptic membranes, facilitating synaptic adhesion.
The LGI1-ADAM22 complex regulates synaptic function:
AMPA receptor trafficking: LGI1-ADAM22 signaling promotes the trafficking and stabilization of AMPA receptors at synapses, enhancing synaptic transmission.
Synaptic strength: The complex contributes to synaptic strength and plasticity through AMPA receptor regulation.
Synapse formation: LGI1 plays roles in synapse formation and maintenance during development.
LGI1 mutations cause ADLTE, formerly called autosomal dominant partial epilepsy with auditory featuresPMID: 27289197PMID: 31211361:
Inheritance: Autosomal dominant with high penetrance
Phenotype: Seizures originating in the lateral temporal lobe, often with auditory symptoms (tinnitus, buzzing)
Pathogenic mechanisms: Dominant-negative effects or loss of function disrupt synaptic signaling and neuronal excitability
Treatment response: Generally responds well to anti-epileptic drugs
LGI1 is implicated in Alzheimer's disease through multiple mechanismsPMID: 21820146:
Expression changes: LGI1 expression is reduced in AD brain, particularly in affected temporal lobe regions
Genetic variants: LGI1 polymorphisms may modify AD risk and age of onset
Synaptic dysfunction: Loss of LGI1 function contributes to AMPA receptor trafficking deficits and synaptic loss
Potential biomarker: LGI1 levels in CSF may serve as a disease marker
LGI1 interacts with the cellular prion protein (PrP^c)PMID: 30833798:
Prion interaction: LGI1 binds to prion protein, potentially influencing prion pathogenesis
Disease modification: LGI1 may modify the progression of prion diseases
Mechanistic significance: This interaction suggests LGI1 participates in broader synaptic vulnerability pathways
LGI1 alterations have been observed in ALS:
Expression changes: LGI1 expression is altered in ALS motor neurons
Potential mechanisms: Dysregulated LGI1 signaling may contribute to synaptic dysfunction in ALS
Therapeutic implications: LGI1-based therapies may have potential in ALS
LGI1 critically regulates AMPA receptor functionPMID: 20457065:
Receptor insertion: Promotes the insertion of AMPA receptors into the postsynaptic membrane
Receptor stabilization: Helps stabilize AMPA receptors at synapses
Synaptic plasticity: Supports LTP and LTD through AMPA receptor regulation
Excitatory transmission: LGI1 loss reduces excitatory synaptic strength
LGI1 is secreted from neurons and acts on both pre- and postsynaptic compartmentsPMID: 20534845PMID: 31167347:
Secretion mechanism:
LGI1 plays roles in synaptic developmentPMID: 30626902:
Synapse formation: Facilitates the formation of excitatory synapses during development
Synapse maturation: Promotes synaptic maturation and the acquisition of proper physiological properties
Synapse maintenance: Helps maintain synaptic structure and function throughout life
LGI1 modulates neuronal excitabilityPMID: 29447922:
Excitability regulation: LGI1 signaling affects neuronal firing properties
Hyperexcitability prevention: Loss of LGI1 function can lead to neuronal hyperexcitability and seizures
Temporal lobe specificity: The high LGI1 expression in temporal lobe explains the seizure focus in ADLTE
Upon LGI1-ADAM22 binding, several intracellular pathways are activated:
| Pathway | Effect | Downstream Targets |
|---------|--------|-------------------|
| PI3K/Akt | Survival, trafficking | mTOR, GSK3β |
| MAPK/ERK | Plasticity, growth | CREB, Elk-1 |
| CaMKII | Synaptic plasticity | AMPA receptors |
| PSD-95 | Scaffold organization | NMDA receptors |
LGI1 interacts with PSD-95 through ADAM22:
LGI1 shows specificity for certain AMPAR subunits:
Over 30 pathogenic LGI1 variants have been identifiedPMID: 27289197PMID: 22150208PMID: 30670673:
Mutation types:
Specific mutations correlate with severity:
LGI1 is significantly altered in AD brainsPMID: 21820146:
Multiple mechanisms contribute to LGI1 loss in AD:
Restoring LGI1 function in AD may provide benefits:
LGI1 directly interacts with cellular prion protein (PrP^c)PMID: 30833798:
Binding characteristics:
LGI1 may modify prion disease progression:
LGI1 variants have been associated with migraine:
Some evidence links LGI1 to schizophrenia:
LGI1's role in synapse formation relates to ASD:
Recombinant LGI1 protein has therapeutic potentialPMID: 33974017:
Drugs enhancing LGI1 signaling:
Viral vector approaches:
ASO-based approaches:
Knockout mice:
LGI1 levels in cerebrospinal fluid:
Peripheral LGI1 measurement:
LGI1 represents a potential therapeutic targetPMID: 33974017:
Protein replacement: Recombinant LGI1 protein may have therapeutic potential
Small molecule approaches: Compounds that enhance LGI1 signaling
Gene therapy: Viral vector-mediated LGI1 delivery
For neurodegenerative diseases:
Alzheimer's disease: Restoring LGI1 function may improve synaptic plasticity
Prion disease: Modulating LGI1-PrP interaction may modify disease progression
Epilepsy: Understanding LGI1 dysfunction guides anti-seizure drug development
Lgi1-deficient mice display significant phenotypes:
Seizures: Spontaneous seizures observed in some lines
Behavioral abnormalities: Altered behavior including anxiety-like phenotypes
Synaptic deficits: Impaired synaptic transmission and plasticity
Development: Some developmental abnormalities
Mouse models with Lgi1 mutations:
ADLTE models: Transgenic mice with patient mutations recapitulate key features
Conditional deletion: Region-specific deletion reveals circuit-specific roles
Rescue studies: Viral delivery of LGI1 reverses some deficits
LGI1 interacts with key synaptic proteins:
ADAM22: Primary receptor mediating postsynaptic effects
ADAM23: Secondary receptor with overlapping functions
GRIP1: Scaffold protein linking ADAM22 to other synaptic proteins
AMPA receptor subunits: GluA1, GluA2 as downstream effectors
LGI1 affects multiple signaling pathways:
PICK1: Protein interacting with C kinase
GRIP: Glutamate receptor interacting protein
PSD-95: Postsynaptic density protein