LC3 (Microtubule-Associated Protein 1 Light Chain 3)
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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.
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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.
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]
The lipidation process converts LC3-I to LC3-II (phosphatidylethanolamine-conjugated form), which is the active form that localizes to autophagosomal membranes.
Role in Autophagy
LC3 is central to the autophagy process:
Initiation: Under nutrient starvation or cellular stress, the autophagy pathway is activated
Lipidation: LC3-I is conjugated to phosphatidylethanolamine by ATG7 (E1-like) and ATG3 (E2-like), forming LC3-II
Membrane recruitment: LC3-II is incorporated into the growing isolation membrane and autophagosome
Cargo recognition: LC3-II interacts with autophagy receptors like [p62/SQSTM1](/proteins/p62-protein) for selective cargo loading
Fusion: LC3-II on the autophagosome membrane facilitates fusion with lysosomes[@mizushima2018]
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
Interactive diagram showing LC3's key relationships in the SciDEX knowledge graph (15 connections shown).
Mermaid diagram (expand to render)
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
[Klionsky DJ, et al, Guidelines for the use and interpretation of assays for monitoring autophagy (2021)](https://pubmed.ncbi.nlm.nih.gov/33634751/)
[Nixon RA, The role of autophagy in neurodegenerative disease (2019)](https://pubmed.ncbi.nlm.nih.gov/23846430/)
[Shpilka T, Weidberg H, Dikstein S, Elazar Z, Atg8: an autophagy-related ubiquitin-like protein family (2021)](https://pubmed.ncbi.nlm.nih.gov/21880108/)
[Ichimura Y, et al, A ubiquitin-like system mediates protein lipidation (2020)](https://pubmed.ncbi.nlm.nih.gov/11108836/)
[Mizushima N, Yoshimori T, Ohsumi Y, The role of Atg proteins in autophagosome formation (2018)](https://pubmed.ncbi.nlm.nih.gov/18983342/)
[Nixon RA, Yang DS, Autophagy failure in Alzheimer disease (2019)](https://pubmed.ncbi.nlm.nih.gov/21614001/)
[Lee JH, et al, Presenilin mutations regulate autophagy in Alzheimer disease (2020)](https://pubmed.ncbi.nlm.nih.gov/33082315/)
[Pickrell AM, Youle RJ, The roles of PINK1, parkin, and mitochondrial fidelity in Parkinson disease (2019)](https://pubmed.ncbi.nlm.nih.gov/25618789/)
[Chen S, et al, Autophagy dysfunction in ALS (2020)](https://pubmed.ncbi.nlm.nih.gov/32384877/)
[Rubinsztein DC, Codogno P, Levine B, Autophagy modulation as a therapeutic target for neurodegenerative diseases (2019)](https://pubmed.ncbi.nlm.nih.gov/22827985/)