GO:0000835 ER ubiquitin ligase complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0000835 defines a ubiquitin ligase complex located in the endoplasmic reticulum (ER) that attaches ubiquitin to substrate proteins.
• The ER ubiquitin ligase complex is a central executor of ER-associated protein degradation (ERAD), a quality-control pathway that removes misfolded or orphaned ER proteins.
• Key complexes include HRD1 (SYVN1) and RNF185/Membralin (TMEM259), which recognize distinct transmembrane degrons and ubiquitinate substrates.
• Substrate processing involves retrotranslocation, ubiquitination, and extraction by VCP/p97 for proteasomal degradation.
• Dysfunction of ER ubiquitin ligase complexes is linked to metabolic liver disease, neurodegeneration, and impaired mitochondrial dynamics.
• CRISPR knockout, point-mutation, knock-in, and overexpression models enable precise interrogation of ER ubiquitin ligase complex components and their substrates.
Description
The endoplasmic reticulum (ER) is the entry point for secretory and membrane proteins, and it maintains a dedicated quality-control system to eliminate terminally misfolded or unassembled proteins. Central to this system is the ER ubiquitin ligase complex (GO:0000835), a cellular component that catalyzes the covalent attachment of ubiquitin to ER-associated substrates, tagging them for degradation. This complex is not a single entity but a family of membrane-embedded ubiquitin ligases, including HRD1 (SYVN1) and RNF185/Membralin, each with distinct substrate specificities and regulatory partners. For researchers, GO:0000835 provides a precise ontological handle to study ER protein homeostasis, ER-associated degradation (ERAD), and the cellular response to ER stress. Mutations or dysregulation of ER ubiquitin ligase components have been implicated in metabolic disorders such as nonalcoholic fatty liver disease (NAFLD) and in the regulation of mitochondrial dynamics. Understanding the composition, assembly, and catalytic mechanisms of this complex is therefore essential for both basic cell biology and therapeutic development. This article integrates authoritative QuickGO annotation with verified PubMed literature to deliver a research-grade overview of GO:0000835, covering its definition, structure, molecular mechanism, key genes, disease relevance, and state-of-the-art methods including CRISPR-based models.
ER ubiquitin ligase complex At A Glance
| GO ID | GO:0000835 |
|---|---|
| GO term | ER ubiquitin ligase complex |
| Ontology | cellular_component |
| Synonym | None listed in QuickGO |
| Major function | Catalyzes ubiquitination of ER-associated substrate proteins, often directing them to ERAD and proteasomal degradation. |
| Subcellular location | Endoplasmic reticulum membrane. |
| Representative subunits | HRD1 (SYVN1), RNF185, Membralin (TMEM259), and associated E2 enzymes. |
| Biological context | ER protein quality control, ERAD, unfolded protein response. |
| Disease links | NAFLD, neurodegeneration, metabolic disorders. |
What Is GO:0000835?
GO:0000835 (ER ubiquitin ligase complex) is a cellular component defined by the Gene Ontology as a ubiquitin ligase complex found in the endoplasmic reticulum [QuickGO]. In practical terms, it is a membrane-associated enzymatic machine that recruits E2 ubiquitin-conjugating enzymes and substrates to facilitate ubiquitin transfer, thereby controlling the stability of ER proteins.
Why Is ER ubiquitin ligase complex Important in Cell Biology?
The ER ubiquitin ligase complex is essential for ER proteostasis because it decides the fate of newly synthesized proteins, eliminating those that fail to fold or assemble. Its activity protects cells from proteotoxic stress and is tightly linked to lipid metabolism, mitochondrial dynamics, and autophagy. Dysregulation of this complex contributes to human diseases ranging from fatty liver disease to neurodegeneration, making it a high-value target for mechanistic and therapeutic research.
• Maintains ER protein quality control by ubiquitinating misfolded or orphaned proteins.
• Executes ERAD, a major degradation pathway for secretory and membrane proteins.
• Prevents proteotoxic stress that can trigger apoptosis and disease.
• Regulates mitochondrial dynamics in brown adipocytes via ERAD.
• Modulates autophagy initiation through VCP/p97 UFMylation and BECN1 stabilization.
• Contributes to NAFLD progression through TRIB3-TRIM8 regulation of HNF4α.
• Provides potential biomarkers and drug targets for metabolic and neurodegenerative diseases.
• Enables precise CRISPR-based dissection of ubiquitin ligase components and substrates.
• Links ER homeostasis to systemic metabolism and inflammation.
• Offers a model system for studying membrane protein degradation and ubiquitin signaling.
Structure and Composition of ER ubiquitin ligase complex
Membrane-embedded E3 ligases
In simple terms: The core of the complex is a set of proteins that sit in the ER membrane and grab target proteins.
The ER ubiquitin ligase complex is anchored in the ER membrane by integral membrane E3 ligases such as HRD1 (SYVN1) and RNF185. HRD1 is a multi-spanning membrane protein that forms a complex with SEL1L and other cofactors to recognize misfolded luminal and membrane substrates. RNF185 associates with Membralin (TMEM259) to form a distinct complex that targets a subset of ER membrane proteins.
Adaptor and accessory proteins
In simple terms: Helper proteins help the ligase recognize which proteins need to be destroyed.
Adaptor proteins such as SEL1L for HRD1 and Membralin for RNF185 are critical for substrate recruitment and complex stability. These adaptors contain domains that bind to exposed hydrophobic patches or specific degrons on substrate proteins, ensuring selectivity. Additional accessory factors, including Derlin proteins and VCP/p97, assist in retrotranslocation and extraction of ubiquitinated substrates.
E2 ubiquitin-conjugating enzymes
In simple terms: The E2 enzyme is the worker that actually attaches ubiquitin to the target.
E3 ligases within the ER complex cooperate with specific E2 ubiquitin-conjugating enzymes, such as UBE2J1 or UBE2G2, to transfer ubiquitin to substrate lysine residues. The choice of E2 influences ubiquitin chain topology, which in turn determines whether substrates are routed to the proteasome or other degradation routes.
Assembly and stoichiometry
In simple terms: The complex is built from several parts that must come together in the right amounts.
Assembly of the HRD1 complex requires co-translational insertion of HRD1 into the ER membrane and subsequent association with SEL1L and other partners. The RNF185/Membralin complex similarly depends on Membralin for stability and function. Disruption of subunit stoichiometry can lead to loss of ligase activity and accumulation of substrates.
Key Genes Involved in GO:0000835 ER ubiquitin ligase complex
The following genes encode core and auxiliary components of the ER ubiquitin ligase complex and its regulatory network.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SYVN1 (HRD1) | E3 ubiquitin ligase in ERAD | Central to ER quality control; linked to neurodegeneration and metabolic disease. |
| SEL1L | Adaptor for HRD1 | Required for HRD1 stability and substrate recognition. |
| RNF185 | E3 ubiquitin ligase | Forms complex with Membralin to degrade ER membrane proteins. |
| TMEM259 (Membralin) | Adaptor for RNF185 | Essential for RNF185 complex function; mutations linked to neurodegeneration. |
| VCP (p97) | AAA+ ATPase | Extracts ubiquitinated substrates from ER for proteasomal degradation. |
| UBE2J1 | E2 ubiquitin-conjugating enzyme | Partners with ER E3 ligases for ubiquitin transfer. |
| UBE2G2 | E2 ubiquitin-conjugating enzyme | Involved in ERAD ubiquitination. |
| DERL1 | Retrotranslocation channel | Facilitates movement of substrates from ER to cytosol. |
| DERL2 | Retrotranslocation channel | Works with DERL1 in ERAD. |
| BECN1 | Autophagy regulator | Stabilized by VCP/p97 UFMylation; links ERAD to autophagy. |
| TRIB3 | Pseudokinase | Forms complex with TRIM8 to regulate HNF4α stability in NAFLD. |
| TRIM8 | E3 ubiquitin ligase | Partners with TRIB3 to degrade HNF4α. |
| HNF4α | Transcription factor | Regulated by TRIB3-TRIM8; involved in NAFLD progression. |
| MFN1 | Mitochondrial fusion protein | Regulated by ERAD in brown adipocytes. |
| MFN2 | Mitochondrial fusion protein | Regulated by ERAD in brown adipocytes. |
| ATF6 | ER stress transcription factor | Indirectly linked to ERAD capacity. |
| XBP1 | ER stress transcription factor | Regulates ERAD gene expression. |
| EDEM1 | ER degradation enhancer | Assists in substrate recognition for ERAD. |
How Is ER ubiquitin ligase complex Regulated?
The ER ubiquitin ligase complex is regulated at multiple levels. Transcriptional induction of HRD1 and other ERAD components occurs downstream of the unfolded protein response (UPR) through ATF6 and XBP1. Post-translational modifications, including UFMylation, modulate the activity of VCP/p97 and its partners, thereby influencing ERAD flux and autophagy initiation. In metabolic tissues, the TRIB3-TRIM8 complex regulates HNF4α stability, linking ER ubiquitin ligase activity to NAFLD progression. Additionally, ERAD activity is tuned by substrate availability and by the assembly state of the ligase complexes themselves.
ER ubiquitin ligase complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| TRIB3 | NAFLD progression | Liver-specific knockout or overexpression in mice. |
| TRIM8 | NAFLD progression | CRISPR knockout in hepatocyte cell lines. |
| RNF185 | Neurodegeneration | Knockout or point-mutation in neuronal cells. |
| TMEM259 | Neurodegeneration | Knock-in of patient mutations in iPSC-derived neurons. |
| MFN1/MFN2 | Mitochondrial dynamics in brown adipocytes | Conditional knockout in brown adipose tissue. |
ER ubiquitin ligase complex in metabolic liver disease
The TRIB3-TRIM8 complex drives NAFLD progression by regulating the stability of HNF4α, a key transcription factor in hepatic lipid metabolism. This demonstrates that ER-associated ubiquitin ligases can directly influence metabolic disease pathogenesis. Targeting this complex may offer therapeutic opportunities for NAFLD.
ER ubiquitin ligase complex and neurodegeneration
Mutations in components of the ER ubiquitin ligase complex, such as RNF185 and Membralin, have been linked to neurodegenerative conditions. Impaired ERAD leads to accumulation of toxic protein aggregates, a hallmark of many neurodegenerative diseases. Understanding how these ligases recognize substrates may reveal new therapeutic targets.
ER ubiquitin ligase complex in mitochondrial dynamics
ERAD regulates mitochondrial dynamics in brown adipocytes by controlling the turnover of mitochondrial fusion proteins MFN1 and MFN2. This cross-talk between ER quality control and mitochondrial function highlights the broader physiological importance of ER ubiquitin ligase complexes.
ER ubiquitin ligase complex and autophagy
VCP/p97 UFMylation stabilizes BECN1 and facilitates autophagy initiation, linking ER ubiquitin ligase complex activity to autophagic pathways. This connection suggests that ERAD dysfunction may impact autophagy and cellular stress responses.
From ER ubiquitin ligase complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of HRD1 impair ERAD? | CRISPR knockout of SYVN1 in HEK293 or HeLa cells. |
| How do point mutations in RNF185 affect substrate ubiquitination? | Point-mutation knock-in via CRISPR in cell lines. |
| Can tagged HRD1 be used to isolate the complex? | Knock-in of FLAG or HA tag at endogenous SYVN1 locus. |
| Does overexpression of Membralin rescue RNF185 function? | Overexpression of TMEM259 in knockout background. |
| What is the role of TRIB3-TRIM8 in HNF4α stability? | Liver-specific knockout or overexpression in mice. |
| How does ERAD regulate mitochondrial dynamics? | Knockout of ERAD components in brown adipocytes. |
How to Study the ER ubiquitin ligase complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| AP-MS | Protein-protein interactions | Identifying subunits of HRD1 or RNF185 complexes. |
| Ubiquitin remnant profiling | Ubiquitination sites on substrates | Mapping ERAD substrate ubiquitination. |
| In vitro ubiquitination | Catalytic activity of E3 ligases | Testing mutant ligase activity. |
| Live-cell imaging | Subcellular localization and dynamics | Tracking ER localization of tagged ligases. |
| CRISPR knockout screens | Gene essentiality and pathway interactions | Discovering regulators of ERAD. |
| RNA-seq | Transcriptional changes | Measuring UPR target gene induction. |
| Proximity labeling (BioID) | Interactome in living cells | Mapping dynamic complex components. |
| Co-immunoprecipitation | Physical associations | Validating adaptor-ligase interactions. |
Proteomics and interactomics
Affinity purification coupled with mass spectrometry (AP-MS) can identify subunits and substrates of the ER ubiquitin ligase complex. Proximity labeling approaches such as BioID can map the interactome in living cells. These methods reveal dynamic changes in complex composition under ER stress.
Ubiquitination assays
In vitro ubiquitination assays using recombinant E1, E2, E3, and substrate proteins can measure catalytic activity of the ER ubiquitin ligase complex. In vivo, ubiquitin remnant profiling by mass spectrometry identifies ubiquitinated lysine residues on substrates.
Imaging and subcellular localization
Fluorescence microscopy and live-cell imaging can track the localization of tagged ligase subunits and substrates within the ER. Co-localization with ER markers such as calnexin confirms ER residency.
CRISPR screening and functional genomics
Genome-wide CRISPR knockout screens can identify genes that modulate ERAD efficiency or sensitivity to ER stress. Focused screens targeting ubiquitin ligase components can uncover synthetic lethal interactions.
How CRISPR Can Be Used to Study GO:0000835 ER ubiquitin ligase complex
Knockout
CRISPR knockout of core ER ubiquitin ligase genes such as SYVN1, RNF185, or TMEM259 abolishes complex activity and leads to substrate accumulation. These models are essential for defining the physiological roles of individual ligases in ERAD and disease.
Point Mutation
Introducing disease-associated point mutations into endogenous ligase genes via CRISPR base editing or homology-directed repair allows precise structure-function analysis. Such models can reveal how specific residues affect substrate recognition or catalytic activity.
Knock-in
Knock-in of epitope tags (e.g., FLAG, HA) or fluorescent proteins at endogenous loci enables endogenous complex purification and live-cell imaging. This approach preserves physiological expression levels and regulatory context.
Overexpression
Overexpression of wild-type or mutant ligase subunits can rescue knockout phenotypes or induce dominant-negative effects. These models are useful for testing gain-of-function mechanisms in disease.
How EDITGENE Supports ER ubiquitin ligase complex Research
Researchers studying ER ubiquitin ligase complex-related genes often need to determine whether a candidate gene is causally involved in ERAD, substrate recognition, or disease progression. EDITGENE provides end-to-end CRISPR services to generate precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for ER ubiquitin ligase complex research.
Frequently Asked Questions About ER ubiquitin ligase complex
What is the ER ubiquitin ligase complex?
The ER ubiquitin ligase complex (GO:0000835) is a ubiquitin ligase complex located in the endoplasmic reticulum that attaches ubiquitin to substrate proteins, often targeting them for degradation.
What genes are involved in the ER ubiquitin ligase complex?
Key genes include SYVN1 (HRD1), SEL1L, RNF185, TMEM259 (Membralin), VCP, UBE2J1, and UBE2G2.
What is the function of GO:0000835?
Its function is to catalyze ubiquitination of ER-associated proteins, facilitating ER-associated degradation (ERAD) and protein quality control.
How is the ER ubiquitin ligase complex linked to disease?
Dysregulation is linked to NAFLD, neurodegeneration, and impaired mitochondrial dynamics.
What is the role of HRD1 in ERAD?
HRD1 (SYVN1) is an E3 ligase that forms a complex with SEL1L to recognize and ubiquitinate misfolded ER proteins.
How does RNF185/Membralin complex function?
RNF185 associates with Membralin to form a distinct ER ubiquitin ligase complex that targets specific ER membrane proteins for degradation.
What methods are used to study the ER ubiquitin ligase complex?
Common methods include AP-MS, ubiquitination assays, live-cell imaging, and CRISPR screens.
Can CRISPR be used to study ER ubiquitin ligase complex genes?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models enable precise functional studies.
What diseases are associated with ER ubiquitin ligase complex dysfunction?
NAFLD, neurodegeneration, and metabolic disorders have been linked to dysfunction of this complex.
How does the ER ubiquitin ligase complex regulate autophagy?
VCP/p97 UFMylation stabilizes BECN1, linking ERAD to autophagy initiation.
Conclusion
The ER ubiquitin ligase complex (GO:0000835) is a cornerstone of ER protein quality control, orchestrating the ubiquitination and degradation of misfolded or orphaned proteins. Its components, including HRD1 and RNF185/Membralin, are critical for ERAD and are implicated in metabolic and neurodegenerative diseases. Advances in CRISPR-based models and multi-omics methods continue to unravel the complex regulation and substrate specificity of this machinery. EDITGENE provides comprehensive CRISPR services to support mechanistic and translational research on ER ubiquitin ligase complex genes.
References
- 1. Krshnan L et al.. 2022. Endoplasmic Reticulum-Associated Protein Degradation.. Cold Spring Harb Perspect Biol 14(12) PMID: 35940909
- 3. van de Weijer ML et al.. 2020. Quality Control of ER Membrane Proteins by the RNF185/Membralin Ubiquitin Ligase Complex.. Mol Cell 79(5):768-781.e7 PMID: 32738194
- 4. Wang Z et al.. 2024. VCP/p97 UFMylation stabilizes BECN1 and facilitates the initiation of autophagy.. Autophagy 20(9):2041-2054 PMID: 38762759
- 5. Christianson JC et al.. 2023. Mechanisms of substrate processing during ER-associated protein degradation.. Nat Rev Mol Cell Biol 24(11):777-796 PMID: 37528230
- 6. Guo L et al.. 2025. Structural insights into the human HRD1 ubiquitin ligase complex.. Nat Commun 16(1):6007 PMID: 40593878
- 7. Xiao MC et al.. 2024. TRIB3-TRIM8 complex drives NAFLD progression by regulating HNF4α stability.. J Hepatol 80(5):778-791 PMID: 38237865
- 8. Zhou Z et al.. 2020. Endoplasmic reticulum-associated degradation regulates mitochondrial dynamics in brown adipocytes.. Science 368(6486):54-60 PMID: 32193362
