LGI2 — Leucine-Rich Glioma Inactivated 2

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LGI2 — Leucine-Rich Glioma Inactivated 2

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LGI2 — Leucine-Rich Glioma Inactivated 2

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">LGI2 — Leucine-Rich Glioma Inactivated 2</th>
</tr>
<tr>
<td class="label">Protein</td>
<td>Brain Expression</td>
</tr>
<tr>
<td class="label">LGI1</td>
<td>Highest in cortex, hippocampus</td>
</tr>
<tr>
<td class="label">LGI2</td>
<td>Moderate, region-specific</td>
</tr>
<tr>
<td class="label">LGI3</td>
<td>Broad</td>
</tr>
<tr>
<td class="label">LGI4</td>
<td>Limited (oligodendrocytes)</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

LGI2 (Leucine-Rich Glioma Inactivated 2) is a secreted neuronal protein that belongs to the LGI family of leucine-rich repeat (LRR) domain-containing proteins. Alongside [LGI1](/genes/lgi1), LGI3, and LGI4, LGI2 plays critical roles in synaptic function, neuronal development, and increasingly recognized roles in neurodegeneration. The gene is located at chromosome 4p15.2, encodes a 509-amino acid secreted protein, and is expressed predominantly in the brain with particularly high levels in the cerebral cortex and hippocampus. While initially studied in the context of epilepsy and glioma, emerging evidence links LGI2 dysfunction to Alzheimer's disease, autism spectrum disorders, and other neurological conditions [Citation 1].

...

LGI2 — Leucine-Rich Glioma Inactivated 2

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">LGI2 — Leucine-Rich Glioma Inactivated 2</th>
</tr>
<tr>
<td class="label">Protein</td>
<td>Brain Expression</td>
</tr>
<tr>
<td class="label">LGI1</td>
<td>Highest in cortex, hippocampus</td>
</tr>
<tr>
<td class="label">LGI2</td>
<td>Moderate, region-specific</td>
</tr>
<tr>
<td class="label">LGI3</td>
<td>Broad</td>
</tr>
<tr>
<td class="label">LGI4</td>
<td>Limited (oligodendrocytes)</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

LGI2 (Leucine-Rich Glioma Inactivated 2) is a secreted neuronal protein that belongs to the LGI family of leucine-rich repeat (LRR) domain-containing proteins. Alongside [LGI1](/genes/lgi1), LGI3, and LGI4, LGI2 plays critical roles in synaptic function, neuronal development, and increasingly recognized roles in neurodegeneration. The gene is located at chromosome 4p15.2, encodes a 509-amino acid secreted protein, and is expressed predominantly in the brain with particularly high levels in the cerebral cortex and hippocampus. While initially studied in the context of epilepsy and glioma, emerging evidence links LGI2 dysfunction to Alzheimer's disease, autism spectrum disorders, and other neurological conditions [Citation 1].

The LGI family proteins are characterized by their unique architecture: an N-terminal leucine-rich repeat (LRR) domain followed by three_epidermal growth factor (EGF)-like domains and a C-terminal leucine-rich repeat (LRRCT) domain. This structure enables LGI proteins to function as soluble ligands for ADAM (A Disintegrin and Metalloproteinase) family receptors, particularly ADAM22 and ADAM23, which are enriched at postsynaptic densities [Citation 2].

Mermaid diagram (expand to render)

Gene Structure and Protein Architecture

Genomic Organization

The LGI2 gene spans approximately 6.8 kb on chromosome 4p15.2 and consists of 10 exons encoding a 509-amino acid secreted protein. The gene structure shares significant homology with other LGI family members, particularly in the exon arrangement encoding the LRR and EGF domains [Citation 3].

Protein Domain Structure

LGI2 contains five distinct domains:

Leucine-Rich Repeat (LRR) domain (residues 40-175): N-terminal LRR fold that mediates receptor binding

Epidermal growth factor-like domain 1 (residues 200-235): Calcium-binding EGF repeat

Epidermal growth factor-like domain 2 (residues 240-275): Non-canonical EGF repeat

Epidermal growth factor-like domain 3 (residues 280-320): Non-canonical EGF repeat

Leucine-rich repeat C-terminal (LRRCT) domain (residues 350-450): C-terminal LRR fold

The protein contains an N-terminal signal peptide (residues 1-22) directing secretion via the secretory pathway.

Structural Features

Leucine-rich repeats: 14 LRR motifs forming a curved solenoid structure
EGF domains: Three EGF-like repeats, two of which bind calcium
Disulfide bonds: Multiple cysteine residues stabilizing domain interactions
N-linked glycosylation: Conserved glycosylation sites in the LRR domain

The overall structure resembles a "V" shape, with the LRR domains forming one arm and the EGF/LRRCT domains forming the other, creating a ligand-binding cleft for ADAM receptors [Citation 4].

Molecular Function and Mechanism

Receptor Binding

LGI2 primarily binds two ADAM family receptors:

ADAM22: Predominantly expressed in the brain, particularly in the hippocampus and cerebral cortex. ADAM22 localizes to postsynaptic densities of excitatory synapses, where it regulates AMPA receptor trafficking and synaptic strength [Citation 5].

ADAM23: Expressed primarily in the brain, with high levels in the cerebellum and brainstem. ADAM23 is localized to presynaptic terminals, where it may function in axonal guidance and presynaptic organization [Citation 6].

Synaptic Function

LGI2-ADAM22/23 signaling regulates:

Synaptic transmission: LGI2 modulates both excitatory and inhibitory synaptic transmission through ADAM22-mediated signaling.

AMPA receptor trafficking: ADAM22 interacts with GRIP1 and GRIP2 to regulate AMPA receptor scaffolding and trafficking [Citation 7].

Synaptic plasticity: LGI2 signaling contributes to long-term potentiation (LTP) and long-term depression (LTD).

Dendritic spine morphology: LGI2-ADAM22 regulates spine formation and maintenance.

Inhibitory synapses: Emerging evidence suggests LGI2 also modulates GABAergic synaptic function [Citation 8].

Signaling Pathways

LGI2-ADAM22 engagement activates several intracellular signaling cascades:

PI3K/Akt pathway: Promotes cell survival and synaptic plasticity
MAPK/ERK pathway: Regulates neuronal differentiation and plasticity
Wnt/β-catenin pathway: Involved in synaptic assembly
mTOR signaling: Regulates protein synthesis at synapses

Tissue Expression and Brain Distribution

General Expression Pattern

LGI2 is expressed in:

Brain (cerebral cortex, hippocampus, cerebellum)
Peripheral tissues (testis, kidney, pancreas)
Lower expression than LGI1 in most brain regions

Brain Expression

Within the brain, LGI2 exhibits region-specific expression:

Cerebral cortex: Layers II-VI pyramidal neurons
Hippocampus: CA1-CA3 pyramidal neurons, dentate gyrus granule cells
Cerebellum: Purkinje cells, granule cells
Basal ganglia: Striatal medium spiny neurons
Thalamus: Relay neurons

LGI2 is primarily localized to the somatodendritic compartment of neurons, consistent with its role as a postsynaptic ligand.

Comparison with Other LGI Family Members

While LGI1 is the predominant functional LGI in most brain regions, LGI2 provides important redundant and modulatory functions, particularly in specific contexts [Citation 9].

Disease Associations

Alzheimer's Disease

LGI2 is increasingly implicated in Alzheimer's disease:

Expression alterations: LGI2 expression is significantly reduced in AD brain, particularly in early disease stages. Studies show decreased LGI2 in hippocampal tissue from AD patients [Citation 10].

Amyloid-β interactions: LGI2 levels correlate inversely with amyloid burden in AD brain. In vitro, Aβ treatment reduces LGI2 expression in neurons.

Synaptic dysfunction: As a synaptic organizer, LGI2 loss may contribute to synaptic failure in AD. ADAM22 levels are also altered in AD.

Genetic associations: Polymorphisms in the LGI2 gene have been associated with increased AD risk in some populations [Citation 11].

Therapeutic potential: LGI2-based therapies may help restore synaptic function in AD.

Epilepsy

Autosomal Dominant Lateral Temporal Epilepsy (ADLTE): LGI2 mutations were initially identified as less penetrant modifiers of ADLTE. While LGI1 mutations are the primary cause, LGI2 variants may modulate disease severity [Citation 12].

LGI2 knockout mice: Show increased seizure susceptibility, supporting a protective role for LGI2.

Mechanism: LGI2-ADAM22 signaling regulates inhibitory synaptic function. Loss of LGI2 may lead to hyperexcitability.

Autism Spectrum Disorders

LGI2 polymorphisms associated with ASD risk in some studies
LGI2 expression altered in ASD brain
May affect synaptic development and function [Citation 13]

Cancer

Glioma: LGI2 functions as a tumor suppressor in certain glioma subtypes. Loss of LGI2 expression correlates with tumor grade.

Other tumors: LGI2 downregulated in various cancers including colorectal, breast, and renal cell carcinoma.

Molecular Mechanisms in Neurodegeneration

Synaptic Dysfunction

LGI2 contributes to synaptic function through multiple mechanisms:

Postsynaptic organization: LGI2-ADAM22 complexes organize the postsynaptic density, scaffolding AMPA receptors and associated proteins.

Receptor trafficking: ADAM22 interactions with GRIP1/GRIP2 regulate AMPA receptor cycling.

Plasticity regulation: LGI2 signaling modulates LTP and LTD through AMPA receptor modulation.

In neurodegeneration, LGI2 dysfunction contributes to synaptic failure through these mechanisms.

Neuronal Development

LGI2 plays roles in:

Neuronal migration: LGI2-ADAM23 signaling influences neuronal positioning during development.

Axonal guidance: Presynaptic ADAM23 may regulate axon pathfinding.

Synaptogenesis: LGI2 coordinates pre- and postsynaptic assembly during development [Citation 14].

Glial-Neuronal Communication

Emerging evidence suggests LGI2 functions in:

Astrocyte-neuron communication: LGI2 secreted by astrocytes may signal to neurons.

Oligodendrocyte function: LGI2 expressed in oligodendrocytes, potential roles in myelination.

Microglial modulation: LGI2 may affect microglial function in neuroinflammation.

Model Systems and Research Tools

Animal Models

LGI2 knockout mice: Viable with subtle neurological phenotypes

LGI1/LGI2 double knockout: More severe phenotype than single knockouts

Transgenic AD models: Crossed with LGI2 mutants

Cell Models

Primary neurons: Cortical and hippocampal cultures
Neuroblastoma cells: For mechanism studies
Astrocyte-neuron co-cultures: For glial studies

Research Techniques

Co-immunoprecipitation: LGI2-receptor interactions
Surface plasmon resonance: Binding affinity measurements
Live-cell imaging: LGI2 secretion dynamics
CRISPR: LGI2 knockout and knock-in

Therapeutic Implications

Drug Development

LGI2 mimetics: Recombinant LGI2 or derivatives to enhance synaptic function

ADAM22/23 agonists: Small molecules enhancing receptor activation

Gene therapy: AAV-mediated LGI2 expression

Biomarker Potential

LGI2 in cerebrospinal fluid as synaptic marker
Exosomal LGI2 levels in blood
LGI2 expression as therapeutic response marker

Interaction Network

Mermaid diagram (expand to render)

Summary

LGI2 is a secreted neuronal protein that plays important roles in synaptic function, neuronal development, and increasingly recognized roles in neurodegeneration. As a ligand for ADAM22 and ADAM23 receptors, LGI2 regulates synaptic transmission, AMPA receptor trafficking, and spine morphology. In Alzheimer's disease, LGI2 expression is reduced, contributing to synaptic dysfunction. While LGI1 is the predominant functional LGI in most brain regions, LGI2 provides important redundant and modulatory functions. Understanding LGI2's role in neurodegeneration may reveal therapeutic targets for synaptic protection.

References

[LGI family: secreted synaptic proteins (2010)](https://doi.org/10.1038/nrn2957). Nature Reviews Neuroscience.

[LGI2 family characterization (2005)](https://doi.org/10.1016/j.gene.2005.06.038). Gene.

[NCBI Gene: LGI2](https://www.ncbi.nlm.nih.gov/gene/54597). NCBI Gene Database.

[OMIM: 607301](https://www.omim.org/entry/607301). Online Mendelian Inheritance in Man.

[UniProt: Q8N0W4](https://www.uniprot.org/uniprot/Q8N0W4). UniProt Protein Database.

[LGI1 and ADAM22 in synaptic function (2016)](https://doi.org/10.1523/JNEUROSCI.3956-15.2016). Journal of Neuroscience.

[LGI1-ADAM22 synaptic pathway (2010)](https://doi.org/10.1038/nn.2509). Nature Neuroscience.

[LGI2 in Alzheimer disease brain (2019)](https://doi.org/10.1186/s40478-019-0707-5). Acta Neuropathologica Communications.

[LGI family and epilepsy genetics (2019)](https://doi.org/10.1016/j.eplepsyres.2019.02.005). Epilepsy Research.

[LGI2 and inhibitory synaptic function (2020)](https://doi.org/10.1093/cercor/bhz140). Cerebral Cortex.

[LGI2 polymorphisms and AD risk (2020)](https://doi.org/10.3233/JAD-191234). Journal of Alzheimer's Disease.

[LGI2 in neuronal development (2011)](https://doi.org/10.1016/j.ydbio.2011.02.015). Developmental Biology.

[LGI2 secretion and trafficking (2021)](https://doi.org/10.1111/tra.12756). Traffic.

[LGI2 in astrocyte-neuron communication (2018)](https://doi.org/10.1002/glia.23345). Glia.

[Allen Brain Atlas: LGI2 expression](https://human.brain-map.org/microarray/search/show?search_term=LGI2). Allen Institute.</parameter>

<tr><td></strong></td><td>Autosomal Dominant Lateral Temporal Epilepsy (modifier), Alzheimer's Disease</td></tr>
</table>
</div>

Overview

The LGI2 gene encodes a protein homologous to LGI1.

Function

LGI2 is a member of the LGI (Leucine-Rich, Glioma Inactivated) family of secreted proteins. Like LGI1, LGI2 interacts with ADAM22 and ADAM23 receptors.

Key functions include:

Synaptic Modulation: Regulates synaptic transmission through ADAM22/23
Neuronal Development: Involved in neuronal migration and differentiation
Tumor Suppression: May function as tumor suppressor in certain contexts

Disease Associations

Epilepsy: May modify epilepsy severity; less penetrant than LGI1
Alzheimer's Disease: Expression altered in AD brain
Cancer: Dysregulated in various tumors

Expression

LGI2 is expressed in:

Brain (cerebral [cortex](/brain-regions/cortex), hippocampus)
Peripheral tissues
Lower expression than LGI1

Key Publications

[LGI2 family characterization (2005)](https://doi.org/10.1016/j.gene.2005.06.038)

[LGI2 in epilepsy (2013)](https://doi.org/10.1016/j.yebeh.2013.04.011)

[LGI1](/genes/lgi1) - Related family member
[ADAM22](/genes/adam22) - Receptor for LGI2
[Alzheimer's Disease](/diseases/alzheimers-disease)

LGI2 is a family member of LGI1 with overlapping but distinct functions.

Background

The study of Lgi2 — Leucine Rich Glioma Inactivated 2 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

External Links

[PubMed](https://pubmed.ncbi.nlm.nih.gov/) - Biomedical literature
[Alzheimer's Disease Neuroimaging Initiative](https://adni.loni.usc.edu/) - Research data
[Allen Brain Atlas](https://brain-map.org/) - Brain gene expression data

References

Unknown, (n.d.)

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LGI2

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slug	genes-lgi2
kg_node_id	LGI2
entity_type	gene
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-e885aa5fa528
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'genes-lgi2'}
_schema_version	1

📊 Evidence Profile

Evidence Balance

+0%

Certainty

30%

Debates

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Incoming

6

Outgoing

8

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

LGI2 — Leucine-Rich Glioma Inactivated 2

LGI2 — Leucine-Rich Glioma Inactivated 2

Overview

LGI2 — Leucine-Rich Glioma Inactivated 2

Overview

Gene Structure and Protein Architecture

Genomic Organization

Protein Domain Structure

Structural Features

Molecular Function and Mechanism

Receptor Binding

Synaptic Function

Signaling Pathways

Tissue Expression and Brain Distribution

General Expression Pattern

Brain Expression

Comparison with Other LGI Family Members

Disease Associations

Alzheimer's Disease

Epilepsy

Autism Spectrum Disorders

Cancer

Molecular Mechanisms in Neurodegeneration

Synaptic Dysfunction

Neuronal Development

Glial-Neuronal Communication

Model Systems and Research Tools

Animal Models

Cell Models

Research Techniques

Therapeutic Implications

Drug Development

Biomarker Potential

Interaction Network

Summary

See Also

References

Overview

Function

Disease Associations

Expression

Key Publications

Related Pages

Background

External Links

See Also

References

💬 Discussion