ATG17 Gene

ATG17 — RB1CC1/FIP200

Introduction

ATG17 (also known as RB1CC1 or FIP200) encodes a critical scaffold protein in the autophagy initiation machinery. Formerly named ATG17 (Autophagy Related 17), the gene was renamed RB1CC1 (RB1 Inducible Coiled-Coil 1) due to its discovery as a RB1 tumor suppressor-interacting protein, while FIP200 (Focal Adhesion Kinase Family Interacting Protein of 200 kDa) remains a widely used alternate name. This protein forms the backbone of the ULK1 complex that nucleates autophagosome formation, making it essential for cellular homeostasis and survival["@rubinsztein2022"].

ATG17 — RB1CC1/FIP200

Introduction

ATG17 (also known as RB1CC1 or FIP200) encodes a critical scaffold protein in the autophagy initiation machinery. Formerly named ATG17 (Autophagy Related 17), the gene was renamed RB1CC1 (RB1 Inducible Coiled-Coil 1) due to its discovery as a RB1 tumor suppressor-interacting protein, while FIP200 (Focal Adhesion Kinase Family Interacting Protein of 200 kDa) remains a widely used alternate name. This protein forms the backbone of the ULK1 complex that nucleates autophagosome formation, making it essential for cellular homeostasis and survival["@rubinsztein2022"].

<div class="infobox infobox-gene">
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<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">RB1CC1/FIP200/ATG17</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>ATG17 (RB1CC1)</td></tr>
<tr><td><strong>Full Name</strong></td><td>RB1 Inducible Coiled-Coil 1</td></tr>
<tr><td><strong>Chromosome</strong></td><td>8q11.23</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[9881](https://www.ncbi.nlm.nih.gov/gene/9881)</td></tr>
<tr><td><strong>OMIM</strong></td><td>604791</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000055118</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q8TF72](https://www.uniprot.org/uniprot/Q8TF72)</td></tr>
<tr><td><strong>Protein Class</strong></td><td>Scaffold Protein / Autophagy Initiation</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>[Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), ALS, FTD, Cancer</td></tr>
</table>
</div>

Gene Structure and Protein Architecture

Gene Organization

The ATG17 gene spans approximately 40 kb on chromosome 8q11.23 and consists of 46 exons encoding a 1,524 amino acid protein with a molecular weight of approximately 200 kDa. The gene exhibits broad tissue expression with particularly high levels in the brain, heart, and skeletal muscle.

Protein Domains and Structure

The RB1CC1/FIP200 protein contains several critical functional domains[@kourtis2021]:

| Domain | Position | Function |
|--------|----------|----------|
| N-terminal coiled-coil domain | 1-400 | Homodimerization, ULK1/2 binding |
| FIP200 interaction domain | 400-800 | Self-association, complex formation |
| ATG101 binding region | 800-1100 | ATG101 recruitment |
| C-terminal focal adhesion targeting (FAT) domain | 1400-1524 | Subcellular localization |
| LC3-interacting region (LIR) | Multiple | Selective autophagy receptor binding |

The protein functions as a homodimer through its N-terminal coiled-coil domains, creating a elongated dimeric structure that serves as a platform for complex assembly. The multiple LIR motifs enable interaction with various autophagy receptors during selective autophagy processes.

Homology and Evolution

While yeast Atg17 is a smaller 37 kDa protein, mammalian RB1CC1/FIP200 represents a functionally conserved ortholog with additional domains acquired during evolution. The core scaffolding function is conserved, but mammalian RB1CC1 has acquired additional regulatory functions through protein-protein interactions[@mizushima2010].

The ULK1 Complex: Architecture and Function

Complex Composition

ATG17/RB1CC1 forms the central scaffold of the ULK1 complex, which consists of four core components[@itakura2012][@ganley2013]:

The complex has a stoichiometry of 1:1:2:1 for ULK1:ATG13:ATG17:ATG101, with ATG17 forming a dimer that provides two binding sites for ULK1-ATG13 dimers.

Initiation Mechanism

The ULK1 complex responds to cellular nutrient status through two primary regulatory pathways[@kim2021]:

mTORC1 Inhibition Pathway:

• Under nutrient-rich conditions, mTORC1 phosphorylates ULK1 and ATG13, maintaining the complex in an inactive state
• Upon nutrient withdrawal, mTORC1 dissociates, allowing ULK1 auto-activation
• ULK1 phosphorylates multiple downstream targets to initiate autophagy

• Energy stress activates AMPK, which directly phosphorylates ULK1 at multiple sites
• AMPK activation occurs in parallel with mTORC1 inhibition
• This provides a second independent activation signal

Role in Autophagosome Formation

Membrane Recruitment

Once activated, the ULK1 complex translocates to the phagophore assembly site (PAS), where ATG17 plays a critical scaffolding role[@nixon2020]:

LC3 Lipidation

ATG17 coordinates with the ATG12-ATG5-ATG16L1 conjugation system to facilitate LC3 lipidation:

• ATG17 recruits ATG16L1 to the expanding phagophore
• LC3 (MAP1LC3A/B) is conjugated to phosphatidylethanolamine
• Lipidated LC3 marks the growing autophagosome and recruits cargo receptors

Closure and Maturation

The complex remains associated with the expanding phagophore until closure:

• ATG17 helps orchestrate the final membrane sealing event
• The mature autophagosome then fuses with lysosomes
• ATG17 is not required for late-stage fusion events

Autophagy in Neurodegeneration

Alzheimer's Disease

Autophagy is profoundly impaired in Alzheimer's disease, and ATG17 dysfunction contributes to disease pathogenesis through multiple mechanisms[@nixon2020][@urschke2022]:

Amyloid-β Clearance:

• Impaired ATG17 function reduces autophagic clearance of amyloid-β
• Aβ accumulates in autophagic vacuoles within neurons
• This creates a vicious cycle where Aβ further inhibits autophagy

• Hyperphosphorylated tau disrupts autophagy through multiple mechanisms
• ATG17 expression is reduced in AD brain
• Restoring ATG17 function may enhance tau clearance

• Neurons are particularly dependent on autophagy due to their post-mitotic state
• Accumulation of damaged proteins and organelles leads to proteostasis collapse
• Autophagy enhancement is a therapeutic target

Parkinson's Disease

ATG17 is critical for mitophagy—the selective autophagy of damaged mitochondria[@tamara2022]:

PINK1-PARKIN Pathway:

• Mitochondrial damage stabilizes PINK1 on the outer membrane
• PINK1 phosphorylates ubiquitin and PARKIN
• Phospho-ubiquitin chains recruit autophagy receptors
• ATG17 coordinates autophagosome formation around damaged mitochondria

• PD neurons are particularly vulnerable to mitochondrial dysfunction
• Impaired mitophagy leads to accumulation of dysfunctional mitochondria
• Enhancing ATG17-mediated mitophagy may protect dopaminergic neurons

• ATG17 expression is reduced in PD brain
• Small molecules enhancing ULK1 complex function are under development
• Gene therapy approaches to boost ATG17 are being explored

Amyotrophic Lateral Sclerosis and Frontotemporal Dementia

Mutations in ATG17/RB1CC1 have been linked to ALS and FTD[@yamamoto2020]:

FIP200 Mutations:

• Rare missense mutations in RB1CC1 are associated with familial ALS
• These mutations impair autophagy function
• TDP-43 pathology may be exacerbated by autophagy dysfunction

• Enhancing autophagy may help clear TDP-43 aggregates
• AAV-mediated ATG17 overexpression is being explored
• Small molecule activators of the ULK1 complex are in development

Interaction Network

ATG17 interacts with multiple proteins to coordinate autophagy initiation[@mari2020]:

| Protein | Interaction Type | Functional Role |
|---------|------------------|-----------------|
| ULK1 | Direct binding | Kinase activation, complex assembly |
| ULK2 | Direct binding | Redundant kinase function |
| ATG13 | Direct binding | Regulatory subunit |
| ATG101 | Direct binding | Complex stabilization |
| VPS34 | Indirect via recruitment | PI3K recruitment |
| BECN1 | Indirect via recruitment | PI3K complex component |
| RB1 | Direct binding | Tumor suppressor function |
| FAK | Direct binding | Cell adhesion signaling |
| p53 | Transcriptional regulation | Tumor suppression |

Expression and Regulation

Brain Distribution

ATG17 is widely expressed in the central nervous system:

| Brain Region | Expression Level | Significance |
|--------------|------------------|---------------|
| Cerebral Cortex | High | High neuronal density, elevated autophagy demand |
| Hippocampus | High | Memory formation, CA1 particularly vulnerable |
| Basal Ganglia | High | Dopaminergic neuron maintenance |
| Cerebellum | High | Purkinje cell function |
| Brainstem | Moderate | Vital function maintenance |
| White Matter | Lower | Lower metabolic activity |

Cellular Expression

• Neurons: High expression; particularly important for protein homeostasis
• Astrocytes: Moderate expression; supports neuronal metabolism
• Microglia: Moderate expression; involved in phagocytosis
• Oligodendrocytes: Lower expression

Regulatory Mechanisms

ATG17 expression and activity are regulated at multiple levels:

Therapeutic Implications

Pharmacological Approaches

Several strategies to enhance ATG17 function are under development[@martinez2016]:

ULK1 Kinase Activators:

• Small molecules that activate ULK1 upstream of ATG17
• May enhance autophagy initiation
• Currently in preclinical development

• Rapamycin and analogues inhibit mTORC1
• Release ULK1 complex from inhibition
• FDA-approved for other indications

• Natural compounds (e.g., curcumin, resveratrol) enhance autophagy
• May act partially through ATG17 pathway
• Clinical trials in AD/PD ongoing

Gene Therapy Approaches

• AAV-mediated ATG17 overexpression
• CRISPR-based gene editing to enhance expression
• miRNA antagonists to reduce inhibitory miRNAs

Combination Strategies

• Autophagy enhancement combined with Aβ/tau targeting
• Multi-target approaches for synergistic effects
• Personalized medicine based on genotype

Key Publications

See Also

• [ATG5 Gene](/genes/ATG5) - Autophagy conjugation system
• [ATG7 Gene](/genes/atg7) - Autophagy conjugation system
• [ULK1 Gene](/genes/ULK1) - Kinase in autophagy initiation
• [Autophagy Pathway](/mechanisms/autophagy-lysosome-pathway) - Autophagy mechanisms
• [Mitophagy Pathway](/mechanisms/mitophagy) - Mitochondrial autophagy
• [Alzheimer's Disease](/diseases/alzheimers-disease) - AD overview
• [Parkinson's Disease](/diseases/parkinsons-disease) - PD overview

External Links

• [GeneCards - RB1CC1](https://www.genecards.org/cgi-bin/carddisp.pl?gene=RB1CC1)
• [UniProt - RB1CC1](https://www.uniprot.org/uniprot/Q8TF72)
• [NCBI Gene - RB1CC1](https://www.ncbi.nlm.nih.gov/gene/9881)
• [OMIM - RB1CC1](https://www.omim.org/entry/604791)
• [Ensembl - RB1CC1](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000055118)
• [Allen Brain Atlas - RB1CC1](https://human.brain-map.org/microarray/search/show?search_term=RB1CC1)

Pathway Diagram

The following diagram shows the key molecular relationships involving ATG17 Gene discovered through SciDEX knowledge graph analysis: