LC3 (Microtubule-Associated Protein 1 Light Chain 3)

LC3 (Microtubule-Associated Protein 1 Light Chain 3)

Introduction

LC3 (Microtubule-Associated Protein 1 Light Chain 3), also known as MAP1LC3 (Microtubule-Associated Protein 1 Light Chain 3), is a fundamental protein in the [autophagy](/entities/autophagy) pathway and serves as a key marker for autophagosome formation. LC3 plays critical roles in neurodegenerative diseases, where autophagy dysfunction is a central pathological feature.

LC3 (Microtubule-Associated Protein 1 Light Chain 3)

Introduction

LC3 (Microtubule-Associated Protein 1 Light Chain 3), also known as MAP1LC3 (Microtubule-Associated Protein 1 Light Chain 3), is a fundamental protein in the [autophagy](/entities/autophagy) pathway and serves as a key marker for autophagosome formation. LC3 plays critical roles in neurodegenerative diseases, where autophagy dysfunction is a central pathological feature.

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">LC3 (Microtubule-Associated Protein 1 Light Chain 3)</th>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>Microtubule-Associated Protein 1 Light Chain 3</td>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>MAP1LC3 (MAP1A, MAP1B)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td>[Q9GZF4](https://www.uniprot.org/uniprot/Q9GZF4) (LC3A), [Q9GZY8](https://www.uniprot.org/uniprot/Q9GZY8) (LC3B)</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~17 kDa</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>LC3, ATG8, Autophagin</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/ad" style="color:#ef9a9a">AD</a>, <a href="/wiki/ali" style="color:#ef9a9a">ALI</a>, <a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">ALZHEIMER</a>, <a href="/wiki/alzheimer's-disease" style="color:#ef9a9a">ALZHEIMER'S DISEASE</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">2307 edges</a></td>
</tr>
</table>

Isoforms

The LC3 family consists of multiple isoforms:

• LC3A (MAP1LC3A) - widely expressed in various tissues
• LC3B (MAP1LC3B) - the most studied isoform, commonly used as an autophagy marker
• LC3C (MAP1LC3C) - more restricted expression pattern
• GABARAP and GATE-16 - related proteins in the ATG8 family[@shpilka2021]

Structure

LC3 belongs to the ATG8 family of proteins and undergoes post-translational modifications essential for its function. The protein contains:

• An N-terminal helical domain
• A ubiquitin-like (Ubl) domain that undergoes lipidation
• A C-terminal glycine exposed by ATG4 protease cleavage[@ichimura2020]

Role in Autophagy

LC3 is central to the autophagy process:

Role in Neurodegenerative Diseases

Alzheimer Disease

In Alzheimer disease (AD), autophagy is significantly impaired at multiple stages:

• Reduced autophagosome-lysosome fusion leads to accumulation of autophagic vacuoles in [neurons](/entities/neurons)[@nixon2019a]
• LC3-positive autophagosomes accumulate in vulnerable neurons, indicating attempted but failed autophagy
• [Amyloid-beta](/proteins/amyloid-beta) (A beta) plaques can be enclosed by LC3-positive membranes, suggesting autophagy attempts to clear A beta aggregates
• The [presenilin](/proteins/presenilin-1-protein) mutations in familial AD impair lysosomal function, downstream of LC3-mediated autophagy[@lee2020]

Parkinson Disease

In Parkinson disease (PD), LC3 and autophagy play critical roles:

• [Alpha-synuclein](/proteins/alpha-synuclein) is degraded by both autophagy and the proteasome
• LC3-positive inclusions are found in PD brains, particularly in [Lewy bodies](/diseases/lewy-body-disease)
• Mutations in [GBA](/genes/gba) (glucocerebrosidase) impair autophagy flux and lead to alpha-synuclein accumulation
• PINK1 and Parkin-mediated mitophagy involves LC3 recruitment to damaged mitochondria[@pickrell2019]

Amyotrophic Lateral Sclerosis

In ALS, autophagy dysfunction contributes to disease progression:

• Mutations in [C9orf72](/genes/c9orf72) dipeptide repeat proteins impair autophagy
• [TDP-43](/mechanisms/tdp-43-proteinopathy) pathology disrupts autophagy-lysosomal pathways
• LC3 aggregation is observed in motor neurons of ALS patients[@chen2020]

Therapeutic Implications

Targeting the autophagy pathway via LC3 modulation represents a therapeutic strategy:

• Autophagy enhancers (rapamycin, carbamazepine) promote LC3-mediated autophagosome formation
• Gene therapy approaches to increase LC3 expression are under investigation
• Small molecules that facilitate LC3 lipidation are being developed[@rubinsztein2019]

Interactions

LC3 interacts with numerous proteins:

• [p62/SQSTM1](/proteins/p62-protein) - autophagy receptor for selective autophagy
• [PINK1](/genes/pink1) - kinase activated in damaged mitochondria
• [Parkin](/genes/parkin) - E3 ubiquitin ligase in mitophagy
• [ATG proteins](/proteins/atg5-protein) - autophagy machinery components
• [OPTN](/genes/optn) - optineurin, autophagy receptor
• [NBR1](/genes/nbr1) - autophagy receptor[@johansen2021]

Pathway & Interaction Diagram

Interactive diagram showing LC3's key relationships in the SciDEX knowledge graph (15 connections shown).

See Also

• [Autophagy](/mechanisms/autophagy)
• [Mitophagy](/mechanisms/mitophagy)
• [p62 Protein](/proteins/p62-protein)
• [Alpha-synuclein](/proteins/alpha-synuclein)
• [Alzheimer Disease](/diseases/alzheimers-disease)
• [Parkinson Disease](/diseases/parkinsons-disease)

References