HERC1 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 1

HERC1 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 1

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HERC1 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 1</th>
</tr>
<tr>
<td class="label">Tissue</td>
<td>Expression Level</td>
</tr>
<tr>
<td class="label">Brain</td>
<td>Very High</td>
</tr>
<tr>
<td class="label">Testis</td>
<td>High</td>
</tr>
<tr>
<td class="label">Lung</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Liver</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Heart</td>
<td>Low-Moderate</td>
</tr>
<tr>
<td class="label">Kidney</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Partner</td>
<td>Interaction</td>
</tr>
<tr>
<td class="label">p62/SQSTM1</td>
<td>Direct binding</td>
</tr>
<tr>
<td class="label">AMPK</td>
<td>Signaling</td>
</tr>
<tr>
<td class="label">mTOR</td>
<td>Signaling</td>
</tr>
<tr>
<td class="label">p53</td>
<td>DNA damage</td>
</tr>
<tr>
<td class="label">Beclin-1</td>
<td>Direct binding</td>
</tr>
<tr>
<td class="label">LC3</td>
<td>Direct binding</td>
</tr>
<tr>
<td class="label">Pathway</td>
<td>HERC1 Role</td>
</tr>
<tr>
<td class="label">mTOR</td>
<td>Modulates activity</td>
</tr>
<tr>
<td class="label">AMPK</td>
<td>Energy stress response</td>
</tr>
<tr>
<td class="label">p53</td>
<td>DNA damage response</td>
</tr>
<tr>
<td cl

HERC1 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 1

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HERC1 — HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 1</th>
</tr>
<tr>
<td class="label">Tissue</td>
<td>Expression Level</td>
</tr>
<tr>
<td class="label">Brain</td>
<td>Very High</td>
</tr>
<tr>
<td class="label">Testis</td>
<td>High</td>
</tr>
<tr>
<td class="label">Lung</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Liver</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Heart</td>
<td>Low-Moderate</td>
</tr>
<tr>
<td class="label">Kidney</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Partner</td>
<td>Interaction</td>
</tr>
<tr>
<td class="label">p62/SQSTM1</td>
<td>Direct binding</td>
</tr>
<tr>
<td class="label">AMPK</td>
<td>Signaling</td>
</tr>
<tr>
<td class="label">mTOR</td>
<td>Signaling</td>
</tr>
<tr>
<td class="label">p53</td>
<td>DNA damage</td>
</tr>
<tr>
<td class="label">Beclin-1</td>
<td>Direct binding</td>
</tr>
<tr>
<td class="label">LC3</td>
<td>Direct binding</td>
</tr>
<tr>
<td class="label">Pathway</td>
<td>HERC1 Role</td>
</tr>
<tr>
<td class="label">mTOR</td>
<td>Modulates activity</td>
</tr>
<tr>
<td class="label">AMPK</td>
<td>Energy stress response</td>
</tr>
<tr>
<td class="label">p53</td>
<td>DNA damage response</td>
</tr>
<tr>
<td class="label">NF-κB</td>
<td>Inflammatory signaling</td>
</tr>
<tr>
<td class="label">MAPK</td>
<td>Stress response</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

HERC1 (HECT and RLD Domain Containing E3 Ubiquitin Protein Ligase 1) is a massive E3 ubiquitin ligase enzyme that plays critical roles in protein quality control, autophagy, DNA repair, and cellular signaling. The HERC1 gene (ENSG00000102786) is located on chromosome 15q22.31 and encodes a protein of 4,862 amino acids, making it one of the largest known E3 ubiquitin ligases in humans [1](https://pubmed.ncbi.nlm.nih.gov/32717140/).

The HERC family consists of two members in mammals (HERC1 and HERC2), both characterized by having a HECT (Homologous to E6-AP C-terminus) domain responsible for ubiquitin ligase activity and an N-terminal RCC1-like domain (RLD) that mediates protein-protein interactions. HERC1 is ubiquitously expressed with particularly high levels in the brain, where it performs essential functions in neuronal protein homeostasis [2](https://pubmed.ncbi.nlm.nih.gov/31616256/).

Given the critical importance of protein quality control in neurons—due to their post-mitotic nature and high metabolic activity—HERC1 dysfunction has been strongly implicated in neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), and various neurodevelopmental disorders. The accumulation of misfolded proteins into toxic aggregates is a hallmark of these diseases, and HERC1's role in ubiquitin-mediated degradation makes it a key player in preventing such pathology.

Molecular Biology and Structure

Gene Organization

The HERC1 gene spans approximately 46 kb of genomic DNA and comprises 54 exons. It encodes a protein of 4,862 amino acids with a molecular weight of approximately 532 kDa. The gene is located on chromosome 15q22.31, a region that has been implicated in various neurological disorders.

Protein Domain Architecture

HERC1 contains several distinct functional domains:

• Seven repeats of the RCC1 motif
• Mediates guanine nucleotide exchange
• Facilitates protein-protein interactions
• Required for proper subcellular localization

• Catalytic domain (~350 amino acids)
• Contains active site cysteine for ubiquitin thioester formation
• Transfers ubiquitin to substrate proteins
• Forms E3 ubiquitin ligase activity

• Connect RLD and HECT domains
• Contain regulatory phosphorylation sites
• Flexible regions allowing domain rearrangements

• Multiple protein-binding motifs
• Nuclear localization signals
• Membrane association domains

Structural Insights

The structure of HERC1 reveals:

• Extended, multi-domain architecture
• Catalytic HECT domain at C-terminus
• N-terminal RLD for substrate recruitment
• Flexible hinge regions for regulatory control
• Dimerization capability through HECT domain

Function in Cellular Physiology

Ubiquitin-Proteasome System

HERC1 is a key component of the ubiquitin-proteasome system (UPS), which is the primary pathway for targeted protein degradation in eukaryotic cells. The UPS involves:

HERC1 catalyzes the formation of ubiquitin chains on target proteins:

• K48-linked chains: Target for proteasomal degradation
• K63-linked chains: Non-degradative signaling roles
• Other linkages: Various cellular regulatory functions

Autophagy Regulation

Beyond the proteasome, HERC1 regulates autophagy—the lysosomal degradation pathway:

Autophagy initiation:

• HERC1 ubiquitinates mTOR pathway components
• Modulates AMPK signaling
• Controls autophagy initiation complexes

• Regulates Beclin-1 and PI3K complexes
• Controls LC3 lipidation
• Facilitates autophagosome nucleation

• Modulates p62/SQSTM1 function
• Controls selective autophagy receptors
• Links ubiquitinated cargo to autophagosomes

DNA Repair

HERC1 participates in DNA damage response:

• Checkpoint regulation: Controls cell cycle arrest
• DNA repair recruitment: Facilitates repair complex assembly
• Chromatin remodeling: Modulates accessibility
• Apoptosis regulation: Decisions between repair and cell death

Synaptic Function

In neurons, HERC1 regulates:

• Synaptic plasticity: Long-term potentiation and depression
• Protein trafficking: Synaptic vesicle proteins
• Receptor turnover: NMDA and AMPA receptor degradation
• Presynaptic function: Neurotransmitter release

Disease Associations

Alzheimer's Disease (AD)

HERC1 dysfunction is strongly implicated in AD pathogenesis through multiple mechanisms [3](https://pubmed.ncbi.nlm.nih.gov/31470367/):

Amyloid metabolism:

• HERC1 regulates APP (Amyloid Precursor Protein) processing
• Affects amyloid-β production and clearance
• Linked to amyloid plaque formation

• HERC1 modulates tau phosphorylation
• Controls tau degradation pathways
• Associated with neurofibrillary tangles

• Impaired UPS in AD brains
• HERC1 downregulation contributes to accumulation
• Synergistic with other E3 ligase deficiencies

• Enhancing HERC1 activity may improve clearance
• Gene therapy approaches under investigation
• Small molecule activators in development

Parkinson's Disease (PD)

HERC1 contributes to PD through:

α-Synuclein metabolism:

• HERC1 regulates α-synuclein degradation
• Impaired clearance leads to Lewy body formation
• Autophagy enhancement may be therapeutic

• HERC1 modulates mitophagy
• PINK1/PARKIN pathway interactions
• Dopaminergic neuron vulnerability

• HERC1 interacts with LRRK2 kinase
• Mutations in both proteins increase PD risk
• Common pathways in protein handling

Neurodevelopmental Disorders

HERC1 mutations cause:

• Neurodevelopmental delay: Cognitive impairment
• Motor dysfunction: Ataxia, movement disorders
• Seizures: Epileptic activity
• Dysmorphic features: Developmental anomalies

Cancer

While primarily studied in neurodegeneration, HERC1 has roles in cancer:

• Altered expression in various tumors
• Cell cycle dysregulation
• DNA repair pathways
• Prognostic significance in some cancers

Expression Pattern

Tissue Distribution

Brain Regional Expression

Within the brain, HERC1 shows highest expression in:

• Hippocampus: CA regions, dentate gyrus (memory)
• Cerebral cortex: All layers (cognitive function)
• Cerebellum: Purkinje cells (motor coordination)
• Basal ganglia: Striatum (movement control)
• Substantia nigra: Dopaminergic neurons

Cellular Localization

HERC1 localizes to:

• Cytoplasm: Primary location, diffuse distribution
• Nucleus: Nuclear envelope, some nuclear functions
• Endoplasmic reticulum: Membrane associations
• Synaptic terminals: Pre- and post-synaptic
• Axonal compartments: Transport vesicles

Therapeutic Implications

Alzheimer's Disease

Therapeutic strategies targeting HERC1:

Current approaches:

• Histone deacetylase (HDAC) inhibitors
• mTOR inhibitors (rapamycin, rapalogs)
• Natural compounds (resveratrol, curcumin)

Parkinson's Disease

HERC1-based PD therapies:

• α-Synuclein clearance enhancement
• Mitophagy restoration
• LRRK2 pathway modulation

Neurodevelopmental Disorders

Gene therapy approaches:

• AAV-mediated HERC1 delivery
• CRISPR-based correction
• Small molecule correctors

Interactions and Pathways

Protein Interactions

HERC1 interacts with multiple proteins:

Signaling Pathways

Ubiquitination Targets

Key substrates for HERC1-mediated ubiquitination:

• mTOR complex components
• AMPK subunits
• p62/SQSTM1
• Various transcription factors
• Cell cycle regulators

Cross-Links

• [Ubiquitin-Proteasome System](/mechanisms/ubiquitin-proteasome-system)
• [Protein Quality Control](/mechanisms/protein-quality-control-network)
• [Autophagy-Lysosome Pathway](/mechanisms/autophagy-lysosome-neurodegeneration)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Amyloid Precursor Protein](/proteins/app)
• [Tau Protein](/proteins/tau)
• [Alpha-Synuclein](/proteins/alpha-synuclein)
• [LRRK2](/genes/lrrk2)
• [PINK1](/genes/pink1)
• [PARKIN](/genes/parkin)
• [HERC2](/genes/herc2)

See Also

• [Ubiquitin-Proteasome System](/mechanisms/ubiquitin-proteasome-system)
• [Protein Quality Control](/mechanisms/protein-quality-control-network)
• [Autophagy-Lysosome Pathway](/mechanisms/autophagy-lysosome-neurodegeneration)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)

External Links

• [NCBI Gene: HERC1](https://www.ncbi.nlm.nih.gov/gene/8925)
• [UniProt: Q9Y4F5](https://www.uniprot.org/uniprot/Q9Y4F5)
• [Ensembl: ENSG00000102786](https://www.ensembl.org/Human/Gene/Summary?g=ENSG00000102786)
• [GeneCards: HERC1](https://www.genecards.org/cgi-bin/carddisp.pl?gene=HERC1)
• [OMIM: 605109](https://www.omim.org/entry/605109)

References