HERC3 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3

HERC3 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HERC3 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>HERC3</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>4q22.1</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/57524" target="_blank">57524</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000163795" target="_blank">ENSG00000163795</a></td>
</tr>
<tr>
<td class="label">OMIM</td>
<td><a href="https://omim.org/entry/609419" target="_blank">609419</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/Q9NPA8" target="_blank">Q9NPA8</a></td>
</tr>
<tr>
<td class="label">Protein Class</td>
<td>HECT domain E3 ubiquitin ligase</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Parkinson's Disease](/diseases/parkinsons-disease), [Alzheimer's Disease](/diseases/alzheimers-disease)</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Brain (substantia nigra, cortex), Liver, Lung</td>
</tr>
</table>

HERC3 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3

HERC3 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HERC3 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>HERC3</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3</td>
</tr>
<tr>
<td class="label">Chromosome</td>
<td>4q22.1</td>
</tr>
<tr>
<td class="label">NCBI Gene</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/57524" target="_blank">57524</a></td>
</tr>
<tr>
<td class="label">Ensembl</td>
<td><a href="https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000163795" target="_blank">ENSG00000163795</a></td>
</tr>
<tr>
<td class="label">OMIM</td>
<td><a href="https://omim.org/entry/609419" target="_blank">609419</a></td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/Q9NPA8" target="_blank">Q9NPA8</a></td>
</tr>
<tr>
<td class="label">Protein Class</td>
<td>HECT domain E3 ubiquitin ligase</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Parkinson's Disease](/diseases/parkinsons-disease), [Alzheimer's Disease](/diseases/alzheimers-disease)</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Brain (substantia nigra, cortex), Liver, Lung</td>
</tr>
</table>

HERC3 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3

<div class="infobox infobox-gene">
<div class="infobox-header">HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3</div>

Pathway / Interaction Diagram

Overview

[HERC3](/genes/herc3) encodes a HECT domain E3 ubiquitin ligase that plays critical roles in protein quality control, [autophagy](/mechanisms/autophagy-lysosome-neurodegeneration), and [NF-κB signaling](/entities/nf-kb). The protein is part of the HERC family of E3 ubiquitin ligases, which are characterized by their unique domain architecture combining HECT (Homologous to E6-AP C-Terminus) catalytic domains with multiple RLD (RCH1-Like Domain) regions. HERC3 has been increasingly recognized for its involvement in [Parkinson's disease](/diseases/parkinsons-disease-disease) pathogenesis through interactions with [LRRK2](/genes/lrrk2), [alpha-synuclein](/proteins/alpha-synuclein), and modulation of [protein quality control](/mechanisms/protein-quality-control-network) pathways.

<div class="infobox-row">
<span class="infobox-label">Gene Symbol</span>
<span class="infobox-value">HERC3</span>
</div>
<div class="infobox-row">
<span class="infobox-label">Full Name</span>
<span class="infobox-value">HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3</span>
</div>
<div class="infobox-row">
<span class="infobox-label">Chromosome</span>
<span class="infobox-value">4q22.1</span>
</div>
<div class="infobox-row">
<span class="infobox-label">NCBI Gene ID</span>
<span class="infobox-value">[57524](https://www.ncbi.nlm.nih.gov/gene/57524)</span>
</div>
<div class="infobox-row">
<span class="infobox-label">OMIM</span>
<span class="infobox-value">[609419](https://www.omim.org/entry/609419)</span>
</div>
<div class="infobox-row">
<span class="infobox-label">Ensembl ID</span>
<span class="infobox-value">[ENSG00000163795](https://www.ensembl.org/Human/Gene/Summary?g=ENSG00000163795)</span>
</div>
<div class="infobox-row">
<span class="infobox-label">UniProt ID</span>
<span class="infobox-value">[Q9NPA8](https://www.uniprot.org/uniprot/Q9NPA8)</span>
</div>
<div class="infobox-row">
<span class="infobox-label">Protein Length</span>
<span class="infobox-value">2,528 amino acids</span>
</div>
<div class="infobox-row">
<span class="infobox-label">Molecular Weight</span>
<span class="infobox-value">~280 kDa</span>
</div>
<div class="infobox-row">
<span class="infobox-label">Expression</span>
<span class="infobox-value">Brain (high), heart, liver, kidney</span>
</div>
<div class="infobox-row">
<span class="infobox-label">Associated Diseases</span>
<span class="infobox-value">Parkinson's disease, Alzheimer's disease, neurodegeneration</span>
</div>
</div>

Gene Structure and Evolution

The [HERC3](/genes/herc3) gene spans approximately 45 kb on chromosome 4q22.1 and consists of 60+ exons encoding a large protein of 2,528 amino acids. The gene belongs to the [HERC family](/entities/herc-family) of E3 ubiquitin ligases, which emerged early in eukaryotic evolution and has undergone significant expansion in vertebrates through gene duplication events [@marin2002].

Domain Architecture

The HERC3 protein possesses a distinctive multi-domain structure that underlies its diverse cellular functions:

• N-terminal RLD domains: Multiple RLD (RCH1-Like Domain) regions (typically 6-8) that serve as protein-protein interaction modules. These domains facilitate recruitment of specific substrates and regulatory proteins to the E3 ligase complex. The RLDs share homology with the RCAN1 (Regulator of Calcineurin 1) protein and are involved in binding to calcineurin and other signaling molecules.
• HECT domain: The C-terminal HECT (Homologous to E6-AP C-Terminus) catalytic domain (~350 amino acids) contains the active site cysteine residue that forms a thioester intermediate with ubiquitin during the ubiquitination process. This domain confers E3 ligase activity and determines substrate specificity through interactions with the N-terminal regulatory regions [@cruz2020].
• Linker regions: Flexible hinge regions connecting the RLD and HECT domains allow conformational changes necessary for substrate recognition and ubiquitination.

Protein Function and Cellular Mechanisms

E3 Ubiquitin Ligase Activity

[HERC3](/genes/herc3) functions as an E3 ubiquitin ligase in the [ubiquitin-proteasome system](/mechanisms/ubiquitin-proteasome-system), where it catalyzes the covalent attachment of ubiquitin molecules to target proteins. This process involves three key enzymatic steps:

The specificity of HERC3 for particular substrates is determined by its N-terminal RLD domains, which recognize specific motifs or conformations in substrate proteins. This allows HERC3 to participate in diverse cellular processes by regulating the stability and function of various protein targets [@kuhnle2012].

Regulation of Autophagy

[HERC3](/genes/herc3) plays a crucial role in regulating [autophagy](/mechanisms/autophagy-lysosome-neurodegeneration), the cellular degradation pathway that maintains protein homeostasis and eliminates damaged organelles. Several key mechanisms have been identified:

BNIP3-mediated mitophagy: HERC3 regulates the degradation of BNIP3 (BCL2/adenovirus E1A 19kDa interacting protein 3), a mitophagy receptor that targets mitochondria for lysosomal degradation. Through HERC3-mediated ubiquitination of BNIP3, cells can fine-tune mitochondrial quality control. Dysregulation of this pathway leads to accumulation of dysfunctional mitochondria, which is a hallmark of neurodegenerative diseases [@liu2020].

p62/SQSTM1 in selective autophagy: HERC3 interacts with p62/SQSTM1 (Sequestosome 1), a selective autophagy receptor that aggregates ubiquitinated proteins for degradation. The ubiquitination of p62 by HERC3 regulates its ability to form phase-separated condensates that target cargo to autophagosomes. This pathway is particularly important for clearing protein aggregates in neuronal cells [@kim2022].

Mitophagy and mitochondrial dynamics: Through modulation of BNIP3 and other mitophagy receptors, HERC3 helps maintain mitochondrial network integrity. Impaired mitophagy leads to mitochondrial dysfunction, increased reactive oxygen species (ROS) production, and neuronal death—all key features of [Parkinson's disease](/diseases/parkinsons-disease-disease) pathogenesis [@okamoto2022].

NF-κB Signaling Modulation

[HERC3](/genes/herc3) regulates the [NF-κB signaling](/entities/nf-kb) pathway, a critical cascade controlling inflammation, cell survival, and immune responses. In microglia (the immune cells of the brain), HERC3 modulates NF-κB activation through direct interaction with key signaling components. This regulation has important implications for neuroinflammation, which is a key contributor to neurodegenerative processes in both [Alzheimer's disease](/diseases/alzheimers-disease) and [Parkinson's disease](/diseases/parkinsons-disease-disease) [@yang2022].

The HECT domain E3 ligases, including HERC3, can function as both positive and negative regulators of NF-κB signaling depending on the substrate and cellular context. HERC3 can ubiquitinate upstream signaling molecules to promote their degradation or activate downstream effectors to enhance the response.

Mitochondrial Function and Energy Metabolism

Emerging evidence points to a role for [HERC3](/genes/herc3) in mitochondrial dynamics and cellular energy metabolism. HERC3 influences mitochondrial fission and fusion processes through regulation of proteins involved in mitochondrial dynamics. Additionally, HERC3 affects mitochondrial biogenesis and function through modulation of PGC-1α (PPARG coactivator 1 alpha) and other master regulators of mitochondrial metabolism [@su2021].

The connections between HERC3, mitochondrial function, and energy metabolism are particularly relevant to neurodegeneration, as mitochondrial dysfunction is a central feature of [Parkinson's disease](/diseases/parkinsons-disease-disease) pathogenesis, especially in dopaminergic neurons of the [substantia nigra](/brain-regions/substantia-nigra).

Expression Patterns

Normal Tissue Distribution

[HERC3](/genes/herc3) exhibits broad but tissue-specific expression patterns:

• Brain: Highest expression in the [cortex](/brain-regions/cortex), [hippocampus](/brain-regions/hippocampus), [cerebellum](/brain-regions/cerebellum), and particularly the [substantia nigra](/brain-regions/substantia-nigra). Within neurons, HERC3 localizes to both the cytoplasm and synapses, consistent with its roles in protein quality control and synaptic function.
• Peripheral tissues: Moderate expression in heart, liver, kidney, and skeletal muscle. In these tissues, HERC3 functions in general protein homeostasis and organelle quality control.
• Cellular localization: Within cells, HERC3 is primarily cytosolic but can associate with membranes including the endoplasmic reticulum, Golgi apparatus, and mitochondria. This subcellular distribution enables it to regulate proteins involved in various cellular compartments.

Regulation of Expression

[HERC3](/genes/herc3) expression is regulated at multiple levels:

• Transcriptional regulation: HERC3 promoter contains response elements for various transcription factors including NF-κB, CREB (cAMP response element-binding protein), and FOXO (Forkhead box O) family members. This allows rapid transcriptional activation in response to cellular stress, oxidative stress, and inflammatory signals.
• Post-translational regulation: HERC3 activity is modulated by phosphorylation, auto-ubiquitination, and interaction with regulatory proteins. The HECT domain can undergo conformational changes that regulate catalytic activity.
• Cellular stress response: HERC3 expression increases under conditions of proteotoxic stress, oxidative stress, and mitochondrial damage, consistent with its role in protein quality control pathways.

Role in Neurodegenerative Diseases

Parkinson's Disease

[HERC3](/genes/herc3) has emerged as a significant player in [Parkinson's disease](/diseases/parkinsons-disease-disease) pathogenesis through multiple mechanisms:

LRRK2 interaction: HERC3 directly interacts with [LRRK2](/genes/lrrk2) (Leucine-Rich Repeat Kinase 2), a protein kinase strongly linked to familial Parkinson's disease. This interaction modulates LRRK2 kinase activity and its ability to phosphorylate downstream targets. Given that LRRK2 mutations are a common cause of familial Parkinson's disease, the HERC3-LRRK2 connection provides a potential therapeutic target [@chen2023].

Alpha-synuclein regulation: HERC3 influences the aggregation and clearance of [alpha-synuclein](/proteins/alpha-synuclein), the protein that forms Lewy bodies in Parkinson's disease brains. Through its E3 ligase activity, HERC3 can ubiquitinate alpha-synuclein and promote its degradation via the [proteasome](/mechanisms/ubiquitin-proteasome-system) or autophagy pathways. However, in Parkinson's disease, this regulatory function may be compromised, contributing to alpha-synuclein accumulation [@zhao2024].

Protein quality control: The [ubiquitin-proteasome system](/mechanisms/ubiquitin-proteasome-system) and autophagy are both impaired in [Parkinson's disease](/diseases/parkinsons-disease-disease), leading to accumulation of misfolded and damaged proteins. As a key E3 ligase in these pathways, HERC3 dysfunction contributes to this proteostatic failure. Research has shown that HERC3 expression is altered in Parkinson's disease brains, with some studies reporting decreased HERC3 levels that would compromise protein quality control [@tang2024].

Neuroinflammation: Through modulation of [NF-κB signaling](/entities/nf-kb), HERC3 regulates microglial activation and neuroinflammation. Chronic neuroinflammation is a key feature of Parkinson's disease progression, and HERC3 dysfunction may exacerbate inflammatory responses in the brain.

Alzheimer's Disease

[HERC3](/genes/herc3) involvement in [Alzheimer's disease](/diseases/alzheimers-disease) is emerging from recent research:

Tau metabolism: HERC3 may regulate tau protein processing and clearance. Tau pathology in Alzheimer's disease involves accumulation of hyperphosphorylated tau in neurofibrillary tangles. HERC3-mediated ubiquitination could potentially target tau for degradation, though this pathway may be impaired in disease states.

Amyloid-beta effects: While direct interactions between HERC3 and amyloid-beta (Aβ) are less characterized, the protein quality control functions of HERC3 could influence Aβ-induced neurotoxicity. Efficient clearance of Aβ aggregates requires functional autophagy and proteasome systems, both of which involve HERC3.

Oxidative stress: Alzheimer's disease brains exhibit high oxidative stress, and HERC3 has been implicated in oxidative stress response pathways. Dysregulation of HERC3 under oxidative conditions could contribute to neuronal dysfunction [@yashiro2018].

Other Neurodegenerative Conditions

• Amyotrophic Lateral Sclerosis (ALS): HERC3 dysfunction may contribute to protein aggregate formation in motor neurons
• Huntington's disease: Impaired autophagy and protein quality control in Huntington's disease could involve HERC3 dysregulation
• Frontotemporal dementia: Some evidence links HERC3 to tauopathies beyond Alzheimer's disease

Genetic Variants and Risk

Common Genetic Variants

Population studies have identified several [HERC3](/genes/herc3) genetic variants that may influence neurodegenerative disease risk. These include:

• Single nucleotide polymorphisms (SNPs): Various SNPs in the HERC3 gene locus have been associated with altered risk for Parkinson's disease in genome-wide association studies (GWAS). The functional consequences of these variants are actively investigated.
• Expression quantitative trait loci (eQTLs): Genetic variants that affect HERC3 expression levels in brain tissue may influence disease risk by modulating protein levels in neurons and glia.

Rare Variants

Rare pathogenic variants in [HERC3](/genes/herc3) have been identified in some cases of early-onset neurodegeneration. These variants often affect the HECT domain catalytic activity or substrate recognition by the RLD domains. While definitive causal relationships require more study, these findings suggest that HERC3 haploinsufficiency or missense mutations may contribute to disease pathogenesis [@liu2022].

Therapeutic Implications

Targeting HERC3 for Neurodegenerative Diseases

The emerging understanding of [HERC3](/genes/herc3) functions in neurodegeneration has highlighted several therapeutic strategies:

Enhancing HERC3 activity: Small molecules that enhance HERC3 E3 ligase activity could improve protein quality control in neurodegeneration. Such approaches would need to balance activation with potential off-target effects.

Modulating HERC3 substrates: Understanding which substrates are most relevant to disease pathogenesis could enable development of drugs that specifically promote ubiquitination of therapeutic targets like alpha-synuclein or tau.

Gene therapy approaches: Viral vector delivery of wild-type HERC3 could potentially restore deficient protein quality control in neurons. However, careful consideration of dosing and expression levels would be essential given the complex regulation of HERC3 activity.

Combination approaches: Targeting HERC3 alongside other components of protein quality control pathways (proteasome, autophagy) may provide synergistic benefits. For example, combination with autophagy enhancers could address multiple aspects of proteostatic failure.

Biomarker Potential

[HERC3](/genes/herc3) levels in cerebrospinal fluid (CSF) or blood have been explored as potential biomarkers for neurodegenerative disease:

• Diagnostic markers: HERC3 levels may differ between disease states and healthy controls
• Disease progression markers: Longitudinal monitoring of HERC3 could track disease progression
• Treatment response markers: Changes in HERC3 levels could indicate response to therapies targeting protein quality control

Research Methods

Studying HERC3 Function

Key experimental approaches for investigating [HERC3](/genes/herc3) include:

• Biochemistry: In vitro ubiquitination assays using recombinant HERC3 and E2 enzymes to characterize substrate specificity
• Cell biology: siRNA/shRNA knockdown or CRISPR-Cas9 knockout in cell lines to assess HERC3 function
• Proteomics: Mass spectrometry to identify HERC3 substrates and interaction partners
• Live cell imaging: Fluorescently tagged HERC3 to study subcellular localization and dynamics
• Animal models: Mouse models with conditional or tissue-specific HERC3 deletion

Challenges in HERC3 Research

• Substrate identification: Many potential HERC3 substrates remain to be identified
• Regulatory complexity: Multiple layers of regulation make it challenging to understand HERC3 function
• Cell-type specificity: HERC3 function may differ between neuronal and non-neuronal cells
• Therapeutic window: Enhancing or inhibiting HERC3 must be carefully balanced to avoid disrupting essential cellular functions

Summary and Future Directions

[HERC3](/genes/herc3) represents a critical node in the cellular protein quality control network with clear relevance to neurodegenerative diseases. Its functions in the [ubiquitin-proteasome system](/mechanisms/ubiquitin-proteasome-system), [autophagy](/mechanisms/autophagy-lysosome-neurodegeneration), [NF-κB signaling](/entities/nf-kb), and mitochondrial dynamics all connect to pathogenic mechanisms in [Parkinson's disease](/diseases/parkinsons-disease-disease) and [Alzheimer's disease](/diseases/alzheimers-disease). The interactions between HERC3 and established disease proteins like [LRRK2](/genes/lrrk2) and [alpha-synuclein](/proteins/alpha-synuclein) further underscore its potential as a therapeutic target.

Future research priorities include:

Understanding the precise mechanisms by which HERC3 maintains neuronal protein homeostasis will be essential for developing effective neuroprotective strategies targeting this important E3 ubiquitin ligase.

See Also

• [Ubiquitin-Proteasome System](/mechanisms/ubiquitin-proteasome-system)
• [Protein Quality Control](/mechanisms/protein-quality-control-network)
• [Autophagy](/mechanisms/autophagy-lysosome-neurodegeneration)
• [E3 Ubiquitin Ligases](/entities/e3-ubiquitin-ligases)
• [LRRK2](/genes/lrrk2)
• [Alpha-synuclein](/proteins/alpha-synuclein)
• [Parkinson's Disease](/diseases/parkinsons-disease-disease)
• [NF-κB Signaling](/entities/nf-kb)
• [HERC Family](/entities/herc-family)
• [Mitochondrial Dysfunction](/mechanisms/mitochondrial-dysfunction-neurodegeneration)

External Resources

• [NCBI Gene: HERC3](https://www.ncbi.nlm.nih.gov/gene/57524)
• [UniProt: HERC3](https://www.uniprot.org/uniprot/Q9NPA8)
• [Ensembl: HERC3](https://www.ensembl.org/Human/Gene/Summary?g=ENSG00000163795)
• [UCSC Genome Browser: HERC3](https://genome.ucsc.edu/cgi-bin/hgTracks?db=hg19&position=chr4:89500000-90500000)

References

Pathway Diagram

The following diagram shows the key molecular relationships involving HERC3 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 3 discovered through SciDEX knowledge graph analysis: