ATG13 (Autophagy Related 13) is a key regulator of autophagy, a critical cellular process for degrading and recycling damaged organelles and protein aggregates. The ATG13 protein is part of the ULK1 complex (ULK1-ATG13-FIP200-ATG101), which initiates autophagosome formation in response to cellular energy status and nutrient availability. This protein plays a crucial role in neuronal health and is implicated in neurodegenerative diseases through its function in mitophagy and aggregate clearance.
| Autophagy Related 13 Protein |
|---|
| Protein Name | ATG13 |
| Gene | ATG13 |
| UniProt ID | Q9UQL6 |
| PDB Structures | 5C6Z, 5ZVN, 5G0F |
| Molecular Weight | 52 kDa |
| Subcellular Localization | Cytoplasm, Autophagosome |
| Protein Family | ATG13 family |
ATG13 is a 459 amino acid protein with an intrinsically disordered region that serves as a scaffold for the ULK1 complex. The protein contains an LC3-interacting region (LIR) that binds to LC3/GABARAP proteins during autophagy initiation. ATG13 also has a domain that interacts with FIP200 and ATG101 to form the stable ULK1 complex.
¶ Domain Architecture
flowchart TD
A["ATG13 459 aa"] --> B["N-terminus<br/>aa 1-150"]
A --> C["Central Scaffold<br/>aa 150-350"]
A --> D["LIR Domain<br/>aa 350-400"]
A --> E["C-terminus<br/>aa 400-459"]
B --> F["ULK1 Binding"]
C --> G["FIP200 Binding"]
C --> H["ATG101 Binding"]
D --> I["LC3/GABARAP Interaction"]
E --> J["Regulation Sites"]
| Feature |
Location |
Function |
| ULK1-binding domain |
N-terminus |
Binds and activates ULK1 kinase |
| FIP200-interacting region |
Central |
Scaffold for complex formation |
| ATG101-binding site |
Central |
Stabilizes ULK1 complex |
| LIR (LC3-interacting region) |
aa 350-400 |
Binds LC3/GABARAP proteins |
| Multiple phosphorylation sites |
Throughout |
Regulation by mTOR/AMPK |
¶ ULK1 Complex Assembly and Regulation
ATG13 is a critical regulator of autophagy initiation. As part of the ULK1 complex (ULK1-ATG13-FIP200-ATG101), ATG13 senses cellular energy status via AMPK and nutrient status via mTOR. When nutrients are scarce or energy is low, ATG13 promotes ULK1 kinase activation, leading to downstream autophagy induction.
Complex regulation:
- Nutrient-rich conditions: mTOR phosphorylates ATG13, inhibiting ULK1 activity
- Starvation: mTOR inhibition allows ATG13 to activate ULK1
- Energy depletion: AMPK phosphorylates ULK1, activating autophagy
- Stress response: ATG13 integrates multiple signals to control autophagosome formation
In neurons, ATG13-mediated autophagy is essential for:
- Synaptic protein turnover: Degradation of old synaptic components
- Mitochondrial quality control: Mitophagy removes damaged mitochondria
- Aggregate clearance: Removes misfolded proteins and aggregates
- Axonal transport: Autophagosomes move along axons to deliver cargo to lysosomes
flowchart TD
A["Nutrient/Energy Status"] --> B{"mTOR Active?"}
B -->|"Yes"| C["mTOR phosphorylates ATG13"]
C --> D["ULK1 inhibited"]
D --> E["Autophagy suppressed"]
B -->|"No"| F["mTOR inactive"]
F --> G["AMPK activates ULK1"]
G --> H["ULK1 phosphorylates ATG13"]
H --> I["PI3K complex recruitment"]
I --> J["Isolation membrane nucleation"]
J --> K["Autophagosome formation"]
L["P62 binds aggregates"] --> K
K --> M["LC3-II formation"]
M --> N["Autophagosome-lysosome fusion"]
N --> O["Degradation"]
Dysregulation of ATG13 contributes to neurodegenerative diseases through impaired autophagy:
- Impaired mitophagy leads to accumulation of damaged mitochondria in dopaminergic neurons
- PINK1/PARKIN pathway dysfunction: ATG13 interacts with PINK1
- Alpha-synuclein clearance is reduced
- Dopaminergic neuron vulnerability: High energy demand makes neurons dependent on mitophagy
- Reduced autophagy impairs clearance of amyloid-beta and tau aggregates
- Synaptic dysfunction: Impaired clearance of damaged synaptic proteins
- Neuronal death: Accumulation of toxic protein aggregates
- Defective autophagy contributes to TDP-43 proteinopathy
- Motor neuron vulnerability: High protein turnover demands
- Aggregate accumulation: TDP-43 inclusions not cleared
- Impaired clearance of mutant huntingtin protein
- Macroautophagy defects: Failed cargo recognition
- Neuronal dysfunction: Aggregate-mediated toxicity
ATG13 plays a direct role in mitophagy through its interaction with the PINK1-PARKIN pathway:
- PINK1 stabilization on damaged mitochondria triggers PARKIN recruitment
- ATG13 assists in the formation of mitophagosomes
- LC3 lipidation is required for autophagosome membrane expansion
- Damaged mitochondria are selectively eliminated
| Target |
Agent |
Mechanism |
Status |
| mTOR inhibitors |
Rapamycin, Everolimus |
Induce autophagy via ATG13/ULK1 |
Approved |
| ULK1 activators |
AZD8055, Torin1 |
Activate autophagy initiation |
Research |
| Autophagy inducers |
Trehalose, Spermidine, Lithium |
Multiple pathways |
Preclinical |
- ATG13 phosphorylation modulators: Develop compounds targeting ATG13 kinases/phosphatases
- LIR domain agonists: Promote LC3 interaction
- Gene therapy: AAV-mediated ATG13 expression
- Trehalose: Induces TFEB and autophagy
- Spermin: Promotes autophagy flux
- Lithium: Inhibits GSK-3β, activates autophagy
- Resveratrol: Activates SIRT1, enhances autophagy
flowchart LR
subgraph Inputs
AmTOR["AmTOR Signaling"]
B["AMPK Signaling"]
C["Calcineurin"]
end
A --> D["ATG13 Phosphorylation"]
B --> E["ULK1 Activation"]
C --> F["TFEB Activation"]
D --> G["ULK1 Complex"]
E --> G
F --> H[" lysosomal biogenesis"]
G --> I["Autophagosome Formation"]
H --> J["Autophagy Flux"]
I --> K["Protein Aggregate Clearance"]
J --> K
K --> L["Neuronal Health"]