ATG17 (Autophagy-Related 17), also known as RB1CC1 (RB1-Inducible Coiled-Coil 1) or FIP200 (Focal Adhesion Kinase Family Interacting Protein of 200 kDa), is a critical autophagy protein that plays essential roles in autophagosome formation. While ATG17 was originally identified in yeast as a component of the autophagy machinery, the mammalian ortholog RB1CC1/FIP200 functions as a large scaffolding protein that integrates autophagy initiation signals and coordinates the assembly of the ULK1 complex. This gene has attracted significant attention in neurodegenerative disease research due to the central role of autophagy in clearing toxic protein aggregates characteristic of diseases like Parkinson's and Alzheimer's.
ATG17/RB1CC1 is a key regulator of the Initiation phase of autophagy, forming a complex with ULK1, ATG13, and ATG101. This complex responds to cellular energy status (via AMPK) and nutrient availability (via mTORC1) to trigger autophagosome nucleation. The dysfunction of this pathway has been implicated in multiple neurodegenerative disorders where impaired autophagy leads to accumulation of toxic protein aggregates.
| Property |
Value |
| Gene Symbol |
ATG17 (yeast) / RB1CC1 (human) |
| Protein |
RB1CC1/FIP200 protein |
| Synonyms |
FIP200, RB1CC1, ULK4 |
| Chromosomal Location |
8q11.21 (human) |
| NCBI Gene ID |
9919 (RB1CC1) |
| UniProt ID |
Q8WWI9 (human) |
| Gene Family |
Autophagy-related (ATG) proteins |
| Protein Length |
1894 amino acids |
| Molecular Weight |
~200 kDa |
ATG17/RB1CC1 functions as a core component of the ULK1 complex, which initiates the autophagic process:
Nutrient depletion / Energy stress
↓
┌───────────┴───────────┐
↓ ↓
AMPK activation mTORC1 inhibition
↓ ↓
└───────────┬───────────┘
↓
ULK1 complex activation
(ULK1-ATG13-RB1CC1-ATG101)
↓
ATG14L phosphorylation
↓
PI3K complex recruitment
↓
Autophagosome nucleation
- Scaffold for ULK1 complex: RB1CC1 provides a platform for ULK1, ATG13, and ATG101 assembly
- Kinase activation: Facilitates ULK1 autophosphorylation and activation
- Phosphorylation targets: Phosphorylates multiple downstream autophagy proteins
- Substrate recruitment: Organizes proteins for autophagosome formation
- mTORC1 regulation: Responds to nutrient signaling via mTORC1 inhibition
- AMPK signaling: Activated by AMPK during energy stress
RB1CC1 is widely expressed in human tissues:
- Brain: High expression in neurons, particularly in the hippocampus and cortex
- Liver: Essential for hepatic autophagy and metabolism
- Muscle: Important for skeletal muscle homeostasis
- Pancreas: Role in pancreatic beta-cell function
- Heart: Cardiac autophagy regulation
- Cytoplasmic: Primarily localizes to the cytoplasm
- Autophagosomal membrane: Recruited to forming autophagosomes
- Pre-autophagosomal structure (PAS): Functions at the site of autophagosome biogenesis
Autophagy dysfunction is a hallmark of Parkinson's disease, and RB1CC1 plays critical roles:
- Aggregate clearance: RB1CC1-mediated autophagy is crucial for clearing alpha-synuclein aggregates
- Loss of function: Impaired RB1CC1 function leads to alpha-synuclein accumulation
- Mutant alpha-synuclein: Mutant forms may interfere with autophagy initiation
- Therapeutic target: Enhancing RB1CC1 activity may promote alpha-synuclein clearance
- Neuronal protection: RB1CC1 activity protects dopaminergic neurons from stress
- Mitochondrial quality control: Mitophagy mediated by RB1CC1 removes damaged mitochondria
- Energy homeostasis: Autophagy maintains cellular energy balance
- Cell death prevention: RB1CC1 deficiency leads to increased neuronal death
- RB1CC1 variants: Genetic polymorphisms have been investigated in PD risk
- Gene expression: Altered RB1CC1 expression in PD brain tissue
RB1CC1 dysfunction contributes to multiple aspects of AD pathogenesis:
- APP processing: RB1CC1 affects amyloid precursor protein processing
- Aβ degradation: Autophagy mediated by RB1CC1 can degrade Aβ oligomers
- Clearance deficits: Impaired RB1CC1 leads to Aβ accumulation
- Tau clearance: RB1CC1-mediated autophagy clears phosphorylated tau
- Tau aggregation: Loss of RB1CC1 promotes tau aggregate formation
- NFT formation: Contributes to neurofibrillary tangle formation
- Synaptic autophagy: RB1CC1 regulates synaptic protein turnover
- Presynaptic terminals: Important for presynaptic autophagy
- Synaptic loss: Dysfunction contributes to synapse elimination
- Motor neuron survival: RB1CC1 is essential for motor neuron viability
- Protein aggregate clearance: Clears aggregating proteins in ALS
- Mitochondrial quality control: Mitophagy removes damaged mitochondria
- Dysfunction mechanisms: Multiple ALS-associated mutations affect autophagy
- Mutant huntingtin clearance: RB1CC1 helps clear mutant huntingtin protein
- Aggregate reduction: Enhancing RB1CC1 reduces huntingtin aggregates
- Neuroprotection: RB1CC1 activity provides neuroprotective effects
The RB1CC1-containing ULK1 complex integrates multiple upstream signals:
Nutrient Sensing:
- mTORC1 directly phosphorylates ULK1 and ATG13 when nutrients are abundant
- Amino acid withdrawal relieves this inhibition
- RB1CC1 senses amino acid availability through interactions withCASTOR proteins
Energy Sensing:
- AMPK activates ULK1 by direct phosphorylation when AMP/ATP ratio increases
- RB1CC1 phosphorylation by AMPK enhances complex activity
- This connects cellular energy status to autophagy initiation
Growth Factor Signaling:
- Insulin and IGF-1 signaling through mTORC1 represses autophagy
- Growth factor withdrawal activates ULK1 complex
- RB1CC1 contains phosphorylation sites for multiple growth factor-regulated kinases
¶ Autophagy Flux and RB1CC1
RB1CC1 plays a critical role in monitoring autophagy flux:
- LC3 lipidation: RB1CC1 activity promotes LC3-I to LC3-II conversion
- Autophagosome maturation: Coordinates with ATG5-ATG12 conjugate system
- Cargo recognition: Partners with p62/SQSTM1 for selective autophagy
- Fusion with lysosomes: Coordinates with SNARE proteins for membrane fusion
Dysregulated autophagy flux contributes to neurodegenerative disease progression when RB1CC1 function is impaired.
RB1CC1 (scaffold)
↓
Binds ULK1 kinase domain
↓
Recruits ATG13
↓
Recruits ATG101
↓
Complete ULK1 complex formation
| Pathway |
Regulation |
Effect |
| AMPK |
Phosphorylates ULK1 |
Activates autophagy |
| mTORC1 |
Inhibits ULK1 complex |
Represses autophagy |
| p53 |
Transcriptional regulation |
Promotes autophagy |
| NF-κB |
Transcriptional regulation |
Cell survival signaling |
- Phosphorylation: Multiple serine/threonine phosphorylation sites
- Ubiquitination: Regulates protein stability and localization
- Acetylation: Affects complex assembly
| Interactor |
Interaction Type |
Functional Effect |
| ULK1 |
Kinase binding |
Autophagy initiation |
| ATG13 |
Scaffold binding |
Complex formation |
| ATG101 |
Scaffold binding |
Complex formation |
| ATG14 |
Phosphorylation target |
Autophagosome nucleation |
| PI3K complex |
Recruitment |
PI3P production |
| FIP200 |
Self-interaction |
Complex stability |
¶ Protein Structure and Domains
RB1CC1/FIP200 contains multiple functional domains:
- Coiled-coil regions: Multiple coiled-coil domains mediate protein-protein interactions
- FIP200 family domain: Conserved domain of unknown function
- ATGL domain: ATG13-binding region essential for complex formation
- LRR domain: Leucine-rich repeat for protein interactions
- C-terminal domain: Regulates ULK1 kinase activity
The protein functions as a homodimer, with dimerization mediated by the coiled-coil regions.
RB1CC1 integrates signals from multiple pathways:
- AMPK-mTOR axis: Central regulator of autophagy initiation
- p53 pathway: Transcriptional regulation of autophagy genes
- NF-κB signaling: Survival signaling cross-talk
| Compound |
Development Stage |
Mechanism |
| Rapamycin |
Clinical use |
mTORC1 inhibition → ULK1 activation |
| Torin1 |
Research tool |
mTORC1 inhibition |
| AICAR |
Research tool |
AMPK activation |
| Metformin |
Clinical use |
AMPK activation |
- RB1CC1 overexpression: Viral vector delivery to enhance autophagy
- ULK1 activation: Upstream autophagy enhancement
- Combination approaches: RB1CC1 with other autophagy genes
- No RB1CC1-targeted therapies in clinical trials for neurodegeneration
- Rapamycin (mTOR inhibitor) has been tested in clinical trials
- Autophagy modulation remains an active research area
- RB1CC1 expression: Can be measured in blood and CSF
- Autophagy markers: LC3, p62 turnover
- Imaging targets: PET ligands for autophagy visualization (under development)
- CRISPR-Cas9: RB1CC1 knockout in cells and animals
- RNAi: knockdown of RB1CC1 expression
- Fluorescent reporters: LC3-GFP, mRFP-GFP-LC3
- Protease inhibitors: Study of autophagy flux
- RB1CC1 knockout mice: Embryonic lethal in complete knockout
- Conditional knockouts: Tissue-specific deletion
- Neuron-specific deletion: Brain-specific autophagy deficiency
- Electron microscopy: Visualize autophagosomes
- Western blot: LC3 lipidation (LC3-II)
- Immunofluorescence: Colocalization studies
- Biochemical assays: Autophagy flux measurements
- Yeast: ATG17 as the founding member
- Mammals: RB1CC1/FIP200 is the functional ortholog
- Drosophila: dFIP200 ortholog
- Conservation: Essential autophagy function conserved
- ATG17 is one of the core autophagy (ATG) genes
- Present in all eukaryotes
- Essential for autophagy in all species studied
- Specific activators: Need for RB1CC1-specific activators
- Brain-penetrant compounds: CNS drug delivery challenges
- Biomarkers: Need for patient selection markers
- Clinical translation: Translation from preclinical to clinical
- Selective autophagy: RB1CC1 in mitophagy and aggrephagy
- Neuroinflammation: Cross-talk between autophagy and inflammation
- Combination therapy: RB1CC1 with protein clearance therapies
- Gene therapy: AAV-mediated RB1CC1 delivery