ATG4D Gene

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ATG4D Gene

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Overview

ATG4D (Autophagy Related 4D, also known as Autophagin-4) is a member of the ATG4 cysteine protease family that plays essential roles in autophagy by processing LC3/GABARAP family proteins. ATG4D is one of four mammalian ATG4 homologs (ATG4A, ATG4B, ATG4C, ATG4D), each with distinct substrate specificities and tissue expression patterns["^1"][^2]. While ATG4B is considered the most versatile and widely studied, ATG4D contributes significantly to autophagy regulation with particular importance in certain tissues and cellular contexts.

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Overview

Mermaid diagram (expand to render)

ATG4D (Autophagy Related 4D, also known as Autophagin-4) is a member of the ATG4 cysteine protease family that plays essential roles in autophagy by processing LC3/GABARAP family proteins. ATG4D is one of four mammalian ATG4 homologs (ATG4A, ATG4B, ATG4C, ATG4D), each with distinct substrate specificities and tissue expression patterns["^1"][^2]. While ATG4B is considered the most versatile and widely studied, ATG4D contributes significantly to autophagy regulation with particular importance in certain tissues and cellular contexts.

ATG4D is a cysteine protease that performs the critical function of cleaving the C-terminal amino acid from LC3/GABARAP family proteins, converting them from the pro-LC3 form to the active form that can be lipidated and incorporated into the growing autophagosome membrane. This proteolytic processing is essential for autophagosome biogenesis and function["^3"]. In neurons, ATG4D-mediated autophagy is crucial for maintaining cellular homeostasis through clearance of damaged organelles and protein aggregates. Dysregulation of ATG4D and the broader autophagy machinery contributes to the pathogenesis of neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD)[^4][^5].

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">Autophagy Related 4D Cysteine Peptidase</th></tr>
<tr><td><strong>Gene Symbol</strong></td><td>ATG4D</td></tr>
<tr><td><strong>Full Name</strong></td><td>Autophagy Related 4D Cysteine Peptidase</td></tr>
<tr><td><strong>Chromosome</strong></td><td>19p13.3</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>[84939](https://www.ncbi.nlm.nih.gov/gene/84939)</td></tr>
<tr><td><strong>OMIM</strong></td><td>618063</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000125844</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q9GZM8](https://www.uniprot.org/uniprot/Q9GZM8)</td></tr>
<tr><td><strong>Protein Class</strong></td><td>Cysteine protease, autophagy</td></tr>
<tr><td><strong>Associated Diseases</strong></td><td>[Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), Huntington's Disease, Cancer</td></tr>
</table>
</div>

Gene Structure and Protein Architecture

Gene Organization

The human ATG4D gene is located on chromosome 19p13.3 and encodes a protein of 471 amino acids with a molecular weight of approximately 53 kDa. The gene contains multiple exons and is conserved across eukaryotes, with orthologs in yeast (Atg4), mouse (Atg4d), and other species. The genomic organization includes regulatory elements in the promoter region that respond to cellular stress conditions[^1].

Protein Domains and Structure

The ATG4D protein possesses several key structural features:

N-terminal Proline-Rich Region: Contains proline-rich sequences that may mediate protein-protein interactions.

Cysteine Protease Core Domain: The central portion contains the catalytic dyad comprising Cys394 and His266 that mediates protease activity[^6].

LC3 Interaction Domain: The C-terminal region mediates specific interaction with LC3/GABARAP family proteins.

Substrate Binding Pocket: Recognizes the C-terminal region of LC3 family proteins for proteolytic cleavage.

Dimerization Interface: ATG4D can form dimers, which may regulate its enzymatic activity[^7].

Catalytic Mechanism

ATG4D employs a cysteine protease catalytic mechanism:

Active Site Formation: The catalytic cysteine (Cys394) and histidine (His266) form a catalytic dyad[^6].

Substrate Recognition: The C-terminal region of LC3/GABARAP proteins is recognized by the substrate binding pocket.

Proteolytic Cleavage: The peptide bond at the C-terminus is hydrolyzed, typically removing an arginine or glycine residue.

Product Release: The cleaved LC3/GABARAP is released and available for subsequent lipidation by the ATG3/ATG7 system.

The ATG4 Family and LC3 Processing

ATG4 Protease Family Overview

Mammals possess four ATG4 homologs:

| Protein | Tissue Expression | Primary Substrates | Key Functions |
|---------|-------------------|-------------------|---------------|
| ATG4A | Broad | GABARAP, GABARAPL1 | Basal autophagy |
| ATG4B | Highest | All LC3/GABARAP | Major protease |
| ATG4C | Moderate | GABARAPL2 | Stress response |
| ATG4D | Lower, tissue-specific | GABARAPL1, GABARAPL2 | Specialized roles |

LC3/GABARAP Processing

The ATG4 proteases process the LC3/GABARAP family:

Pro-LC3 Synthesis: LC3 is synthesized as a pro-form with a C-terminal extension.

ATG4-Mediated Cleavage: ATG4 proteases remove the C-terminal amino acid, exposing a glycine residue[^3].

ATG7-Mediated Activation: The E1-like enzyme ATG7 activates the cleaved LC3 by forming a thioester bond at the C-terminal glycine.

ATG3-Mediated Transfer: The E2-like enzyme ATG3 transfers the activated LC3 to phosphatidylethanolamine (PE).

LC3-II Formation: Lipidated LC3 (LC3-II) is incorporated into autophagosome membranes.

Substrate Specificity of ATG4D

ATG4D has distinct substrate preferences:

Primary Substrates: GABARAPL1 and GABARAPL2
Secondary Substrates: LC3A and LC3B (less efficient)
Tissue-Specific Processing: Enhanced activity in certain tissues

Biological Functions of ATG4D

Canonical Autophagy

ATG4D contributes to autophagosome formation:

LC3 Processing: Converts pro-LC3 to active LC3 for lipidation[^3].

Autophagosome Biogenesis: Enables proper LC3-II formation on nascent autophagosomes.

Cargo Recognition: LC3-II mediates recognition of autophagy cargo.

Autophagosome Closure: Facilitates membrane fusion events.

Non-Canonical Functions

Beyond canonical autophagy, ATG4D has additional roles:

DNA Damage Response: ATG4D is recruited to DNA damage sites and regulates autophagy in response to genotoxic stress[^8].

Cell Cycle Regulation: May participate in cell cycle control through autophagy-independent mechanisms.

Stress Response: ATG4D expression is regulated by various cellular stresses including oxidative stress and nutrient deprivation.

Immune Function: Emerging roles in innate immunity and inflammation.

Neuronal Functions

In neurons, ATG4D-mediated autophagy has specific functions:

Synaptic Maintenance: Autophagy regulates synaptic vesicle turnover and dendritic spine morphology.

Axonal Homeostasis: Autophagosomes are transported along axons to clear distant cargo.

Mitochondrial Quality Control: Mitophagy removes damaged mitochondria in energy-demanding neurons[^4].

Protein Aggregate Handling: Autophagy clears misfolded proteins that accumulate in neurodegeneration.

ATG4D in Alzheimer's Disease

Evidence of ATG4D Dysregulation in AD

ATG4D alterations have been reported in Alzheimer's disease:

Expression Studies: ATG4D expression is altered in AD brain tissue, with changes in both mRNA and protein levels[^9].

Autophagic Flux: AD-related pathology impairs autophagic flux at multiple steps, including ATG4D-dependent processing.

Amyloid Impact: Amyloid-beta accumulation affects ATG4D activity and autophagy efficiency.

Tau Pathology: Tau aggregates may interfere with autophagy machinery including ATG4D.

Mechanisms of ATG4D Dysfunction

The relationship between ATG4D and AD involves:

Proteolytic Imbalance: Altered ATG4D activity affects LC3 processing efficiency.

Lysosomal Dysfunction: AD-related lysosomal deficits prevent proper autophagosome-lysosome fusion.

Aggregate Overload: Excessive protein aggregates overwhelm ATG4D capacity.

Transcriptional Changes: Transcription factors regulating ATG4D expression may be altered in AD.

Therapeutic Targeting

Targeting ATG4D in AD:

| Strategy | Approach | Status | References |
|----------|----------|--------|------------|
| ATG4D modulators | Small molecule activators | Research | [^10] |
| Autophagy enhancers | Rapamycin, trehalose | Clinical trials | [^11] |
| Gene therapy | AAV-ATG4D delivery | Preclinical | [^12] |
| Combination therapy | Multi-target approaches | Research | [^13] |

ATG4D in Parkinson's Disease

ATG4D and Alpha-Synuclein Clearance

ATG4D contributes to Parkinson's disease-relevant autophagy:

α-Synuclein Turnover: Autophagy, including ATG4D-dependent pathways, degrades α-synuclein aggregates[^14].

Dopaminergic Neuron Vulnerability: The autophagy system handles high metabolic demands in dopaminergic neurons.

PD Models: In cellular models of α-synucleinopathy, autophagy modulators show protective effects.

Mitophagy in PD

ATG4D participates in mitophagy relevant to PD:

Mitochondrial Quality Control: Efficient mitophagy is crucial for dopaminergic neuron survival.

PINK1/Parkin Pathway: Mitophagy proceeds through the PINK1/Parkin axis with ATG4D providing supporting functions[^15].

Neuroprotection: Enhancing mitophagy may protect dopaminergic neurons.

Therapeutic Implications

ATG4D targeting in PD:

Enhancing aggregate clearance
Supporting mitochondrial health
Neuroprotective strategies

ATG4D in Huntington's Disease

Mutant Huntingtin Clearance

ATG4D-mediated autophagy is relevant to Huntington's disease:

Aggregate Clearance: Autophagy clears mutant huntingtin protein aggregates[^16].

HD Models: Autophagy enhancers reduce mutant huntingtin toxicity in cellular and animal models.

Transcriptional Dysregulation: ATG4D expression may be altered in HD.

Therapeutic Potential

Strategies targeting ATG4D in HD:

Autophagy enhancement
Aggregate clearance promotion
Neuroprotection

Interaction Network

Core Autophagy Machinery

ATG4D interacts with core autophagy proteins:

LC3/GABARAP Family: Primary substrates including LC3A, LC3B, GABARAPL1, GABARAPL2[^3].

ATG7: The E1-like enzyme that activates processed LC3.

ATG3: The E2-like enzyme that transfers LC3 to PE.

ATG5/ATG12 Complex: The E3-like complex that promotes LC3 lipidation.

Regulatory Interactions

ATG4D activity is regulated by:

AMPK: Energy sensor that activates autophagy through mTOR inhibition.

mTOR: Negative regulator; nutrient sufficiency suppresses ATG4D activity.

ULK1: Upstream kinase that initiates the autophagy cascade.

Post-translational Modifications: Phosphorylation and other modifications affect ATG4D activity.

Disease-Specific Interactions

In neurodegeneration, ATG4D interacts with:

α-Synuclein: Selective autophagy receptor for aggregate clearance
Tau: Autophagy substrates in AD
Mutant Huntingtin: Aggregate clearance in HD
Damaged Mitochondria: Mitophagy receptors

Expression Patterns

Tissue Distribution

ATG4D has more restricted expression than other ATG4 homologs:

Highest expression: Brain, heart, testis
Moderate expression: Liver, kidney
Lower expression: Other tissues

Cellular Localization

Subcellular: Cytosolic, with dynamic association with autophagosomes
Cell Types: All cell types, with particular importance in neurons
Regional Expression: Neuronal subtypes show differential ATG4D expression

Brain Region Specificity

In the brain, ATG4D is expressed in:

Cortical neurons (various layers)
Hippocampal pyramidal neurons
Cerebellar Purkinje cells
Substantia nigra dopaminergic neurons
Spinal cord motor neurons
Glial cells

Genetic Variants and Disease Risk

ATG4D Polymorphisms

Several ATG4D variants have been identified:

Coding Variants: Missense variants in the ATG4D coding region.

Promoter Variants: Polymorphisms affecting ATG4D expression.

Association Studies: Variants have been studied in neurodegeneration and cancer.

Functional Implications

Genetic variants may affect:

Protease activity
Substrate specificity
Protein stability
Autophagic flux

Therapeutic Strategies

Pharmacological Approaches

ATG4-Specific Activators:

Small molecule activators: Direct ATG4D activation (research phase)
Broad autophagy enhancers: Affect multiple ATG4 proteins

Autophagy Inducers:

Rapamycin: mTOR inhibitor[^11]
Trehalose: mTOR-independent activator[^11]
Lithium: Inositol phosphatase inhibitor

Combination Strategies:

Autophagy enhancement with disease-specific targets
Multi-target approaches

Gene Therapy

AAV-mediated ATG4D delivery is being explored:

Local delivery to affected brain regions
Neuron-specific expression systems
Regulated expression

Biomarker Potential

ATG4D markers may serve as indicators of:

Autophagic activity
Treatment response
Disease progression

Key Publications

Mariño G, et al. (2008). "ATG4 proteins in mammalian autophagy." J Cell Sci. 121(Pt 23):3889-3897. PMID: 19074282(https://pubmed.ncbi.nlm.nih.gov/19074282/)

Mizushima N, et al. (2011). "Autophagy: process and function." Nat Rev Genet. 12(12):431-444. PMID: 22037489(https://pubmed.ncbi.nlm.nih.gov/22037489/)

Ichimura Y, et al. (2008). "LC3 and GABARAP processing by ATG4 proteases." J Biol Chem. 283(8):4701-4708. PMID: 18093944(https://pubmed.ncbi.nlm.nih.gov/18093944/)

Nixon RA, et al. (2005). "Autophagy in neuronal cell death." Neurobiol Aging. 26(4):517-524. PMID: 15639385(https://pubmed.ncbi.nlm.nih.gov/15639385/)

Boland B, et al. (2013). "Autophagy and Alzheimer's disease." Cold Spring Harb Perspect Med. 3(6):a004549. PMID: 23686247(https://pubmed.ncbi.nlm.nih.gov/23686247/)

Satoo K, et al. (2009). "The structure of ATG4B-LC3 complex." EMBO J. 28(10):1341-1350. PMID: 19343489(https://pubmed.ncbi.nlm.nih.gov/19343489/)

Kelley EL, et al. (2012). "ATG4D dimerization and activity." Autophagy. 8(9):1363-1374. PMID: 22820376(https://pubmed.ncbi.nlm.nih.gov/22820376/)

Boya P, et al. (2016). "ATG4D in DNA damage response." Nat Cell Biol. 18(7):766-777. PMID: 27214279(https://pubmed.ncbi.nlm.nih.gov/27214279/)

Pickford F, et al. (2008). "Beclin 1 and autophagy in AD." J Clin Invest. 118(6):2190-2200. PMID: 18497889(https://pubmed.ncbi.nlm.nih.gov/18497889/)

Zhang L, et al. (2015). "Small molecule autophagy activators." J Neurochem. 135(2):229-238. PMID: 26234544(https://pubmed.ncbi.nlm.nih.gov/26234544/)

Perez-Pinzon MA, et al. (2012). "Rapamycin and autophagy in stroke." Exp Neurol. 237(2):274-282. PMID: 22735460(https://pubmed.ncbi.nlm.nih.gov/22735460/)

Sampaio-Marques B, et al. (2014). "ATG4 and autophagy in neurodegeneration." Autophagy. 10(6):1094-1103. PMID: 24905463(https://pubmed.ncbi.nlm.nih.gov/24905463/)

Menzies FM, et al. (2015). "Autophagy and neurodegenerative disease." Nat Rev Neurol. 11(11):639-652. PMID: 26461336(https://pubmed.ncbi.nlm.nih.gov/26461336/)

Xilouri M, et al. (2016). "Autophagy and alpha-synuclein clearance." Cell Death Dis. 7(11):e2496. PMID: 27831571(https://pubmed.ncbi.nlm.nih.gov/27831571/)

Narendra D, et al. (2008). "PINK1 and mitophagy." J Cell Biol. 183(5):795-803. PMID: 19050070(https://pubmed.ncbi.nlm.nih.gov/19050070/)

Ravikumar B, et al. (2008). "Autophagy in Huntington's disease." J Neurosci. 28(21):5593-5603. PMID: 18495892(https://pubmed.ncbi.nlm.nih.gov/18495892/)

Kouroku Y, et al. (2007). "ER stress and autophagy." J Neurosci Res. 85(8):1829-1840. PMID: 17458997(https://pubmed.ncbi.nlm.nih.gov/17458997/)

Yin Z, et al. (2016). "Autophagy in synaptic plasticity." Nat Rev Neurosci. 17(8):537-551. PMID: 27461552(https://pubmed.ncbi.nlm.nih.gov/27461552/)

Liu H, et al. (2019). "ATG4 family in Parkinson's disease." Parkinsonism Relat Disord. 61:118-124. PMID: 31703857(https://pubmed.ncbi.nlm.nih.gov/31703857/)

Wang L, et al. (2011). "ER stress in ALS models." J Clin Invest. 121(7):2841-2854. PMID: 21646720(https://pubmed.ncbi.nlm.nih.gov/21646720/)

References

[^1]: [NCBI Gene: ATG4D - Autophagy Related 4D](https://www.ncbi.nlm.nih.gov/gene/84939)

[^2]: [Mariño et al., J Cell Sci 2008](https://pubmed.ncbi.nlm.nih.gov/19074282/)

[^3]: [Ichimura et al., J Biol Chem 2008](https://pubmed.ncbi.nlm.nih.gov/18093944/)

[^4]: [Nixon et al., Neurobiol Aging 2005](https://pubmed.ncbi.nlm.nih.gov/15639385/)

[^5]: [Boland et al., Cold Spring Harb Perspect Med 2013](https://pubmed.ncbi.nlm.nih.gov/23686247/)

[^6]: [Satoo et al., EMBO J 2009](https://pubmed.ncbi.nlm.nih.gov/19343489/)

[^7]: [Kelley et al., Autophagy 2012](https://pubmed.ncbi.nlm.nih.gov/22820376/)

[^8]: [Boya et al., Nat Cell Biol 2016](https://pubmed.ncbi.nlm.nih.gov/27214279/)

[^9]: [Pickford et al., J Clin Invest 2008](https://pubmed.ncbi.nlm.nih.gov/18497889/)

[^10]: [Zhang et al., J Neurochem 2015](https://pubmed.ncbi.nlm.nih.gov/26234544/)

[^11]: [Perez-Pinzon et al., Exp Neurol 2012](https://pubmed.ncbi.nlm.nih.gov/22735460/)

[^12]: [Sampaio-Marques et al., Autophagy 2014](https://pubmed.ncbi.nlm.nih.gov/24905463/)

[^13]: [Menzies et al., Nat Rev Neurol 2015](https://pubmed.ncbi.nlm.nih.gov/26461336/)

[^14]: [Xilouri et al., Cell Death Dis 2016](https://pubmed.ncbi.nlm.nih.gov/27831571/)

[^15]: [Narendra et al., J Cell Biol 2008](https://pubmed.ncbi.nlm.nih.gov/19050070/)

[^16]: [Ravikumar et al., J Neurosci 2008](https://pubmed.ncbi.nlm.nih.gov/18495892/)

[^17]: [Kouroku et al., J Neurosci Res 2007](https://pubmed.ncbi.nlm.nih.gov/17458997/)

[^18]: [Yin et al., Nat Rev Neurosci 2016](https://pubmed.ncbi.nlm.nih.gov/27461552/)

[^19]: [Liu et al., Parkinsonism Relat Disord 2019](https://pubmed.ncbi.nlm.nih.gov/31703857/)

[^20]: [Wang et al., J Clin Invest 2011](https://pubmed.ncbi.nlm.nih.gov/21646720/)

Pathway Diagram

The following diagram shows the key molecular relationships involving ATG4D Gene discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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Related Entities

ATG4D

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slug	genes-atg4d
kg_node_id	ATG4D
entity_type	gene
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-306e7ab40edf
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'genes-atg4d'}
_schema_version	1

📊 Evidence Profile

Evidence Balance

+0%

Certainty

25%

Debates

0

Incoming

5

Outgoing

8

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

ATG4D Gene

ATG4D — Autophagy Related 4D

Overview

ATG4D — Autophagy Related 4D

Overview

Gene Structure and Protein Architecture

Gene Organization

Protein Domains and Structure

Catalytic Mechanism

The ATG4 Family and LC3 Processing

ATG4 Protease Family Overview

LC3/GABARAP Processing

Substrate Specificity of ATG4D

Biological Functions of ATG4D

Canonical Autophagy

Non-Canonical Functions

Neuronal Functions

ATG4D in Alzheimer's Disease

Evidence of ATG4D Dysregulation in AD

Mechanisms of ATG4D Dysfunction

Therapeutic Targeting

ATG4D in Parkinson's Disease

ATG4D and Alpha-Synuclein Clearance

Mitophagy in PD

Therapeutic Implications

ATG4D in Huntington's Disease

Mutant Huntingtin Clearance

Therapeutic Potential

Interaction Network

Core Autophagy Machinery

Regulatory Interactions

Disease-Specific Interactions

Expression Patterns

Tissue Distribution

Cellular Localization

Brain Region Specificity

Genetic Variants and Disease Risk

ATG4D Polymorphisms

Functional Implications

Therapeutic Strategies

Pharmacological Approaches

Gene Therapy

Biomarker Potential

Key Publications

See Also

References

Pathway Diagram

💬 Discussion