GO:0120323 lipid ubiquitination: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0120323 lipid ubiquitination is the biological process in which one or more ubiquitin groups are covalently added to a lipid molecule.
• The process expands the ubiquitin code beyond proteins and regulates membrane dynamics, lipid metabolism, and innate immunity [2, 4].
• Key enzymes include the ubiquitin-activating enzyme UBA1, ubiquitin-conjugating enzymes such as UBE2J2, and ubiquitin ligases such as RNF213 and ITCH [5, 6, 7].
• Lipid ubiquitination controls ER-phagy, lysophagy, and ERAD, linking lipid chemistry to organelle quality control [1, 5, 6].
• Dysregulation of lipid ubiquitination is implicated in cancer, neurodegeneration, and metabolic disorders.
• CRISPR knockout, point-mutation, knock-in, and overexpression models are essential to dissect the causal roles of lipid-ubiquitination enzymes [1, 5, 6].
Description
Lipid ubiquitination (GO:0120323) is a biological process in which one or more ubiquitin groups are added to a lipid molecule. This definition places lipids alongside proteins as substrates of the ubiquitin system, expanding the known ubiquitin code to include non-protein targets. The process is emerging as a critical regulator of membrane remodeling, organelle quality control, and host defense [1, 4]. For researchers, lipid ubiquitination offers a new layer of regulation that connects lipid metabolism to protein degradation and signaling pathways. Understanding this process requires identifying the enzymes that attach ubiquitin to lipids, the lipid substrates involved, and the downstream consequences for cellular homeostasis [2, 4]. Recent studies have shown that ubiquitination of lipids and lipid-associated structures controls ER-phagy, lysophagy, and ER-associated degradation (ERAD), highlighting its broad physiological importance [1, 5, 6]. As the field grows, lipid ubiquitination is becoming a focal point for therapeutic targeting in cancer, neurodegeneration, and infectious diseases [4, 7].
lipid ubiquitination At A Glance
| GO ID | GO:0120323 |
|---|---|
| GO term | lipid ubiquitination |
| Ontology | biological_process |
| Synonym | none |
| Major function | Covalent attachment of ubiquitin to lipid molecules, regulating membrane dynamics and lipid metabolism [2, 4] |
| Key enzymes | UBA1, UBE2J2, RNF213, ITCH, UBE3C [3, 5, 6, 7] |
| Substrates | Lipids such as lipopolysaccharide and membrane lipids |
| Associated processes | ER-phagy, lysophagy, ERAD, innate immunity [1, 5, 6, 7] |
| Disease relevance | Cancer, neurodegeneration, metabolic disorders |
What Is GO:0120323?
GO:0120323 lipid ubiquitination is defined as the process in which one or more ubiquitin groups are added to a lipid. This covalent modification can occur on various lipid species, including lipopolysaccharide and possibly other membrane lipids, and is mediated by enzymatic machinery that transfers ubiquitin from a ubiquitin-conjugating enzyme to the lipid substrate [2, 7]. Unlike protein ubiquitination, which typically targets lysine residues, lipid ubiquitination involves the attachment of ubiquitin to lipid hydroxyl or other reactive groups, though the exact chemistry may vary by substrate. The process is part of the broader ubiquitin code and can signal for downstream events such as membrane remodeling, autophagy, or immune signaling [2, 4].
Why Is lipid ubiquitination Important in Cell Biology?
Lipid ubiquitination is important because it represents a non-canonical ubiquitin modification that directly impacts membrane biology and cellular stress responses [2, 4]. By tagging lipids with ubiquitin, cells can recruit autophagy receptors and other effector proteins to specific membranes, thereby controlling organelle turnover and lipid homeostasis [1, 4]. This process is also a key component of innate immunity, as ubiquitination of bacterial lipopolysaccharide by RNF213 restricts intracellular bacterial infection. Dysregulation of lipid ubiquitination has been linked to cancer, neurodegeneration, and metabolic diseases, making it a promising target for therapeutic intervention. Furthermore, understanding lipid ubiquitination provides insight into the broader ubiquitin code and its role in health and disease.
• Regulates ER-phagy and endoplasmic reticulum remodeling.
• Controls lysophagy initiation upon lysosomal damage.
• Modulates ERAD efficiency in response to membrane lipid saturation.
• Mediates innate immune defense against bacterial pathogens.
• Influences autophagy through ATG4B ubiquitination.
• Connects lipid metabolism to protein degradation pathways.
• Implicated in cancer, neurodegeneration, and metabolic disorders.
• Expands the ubiquitin code beyond proteins.
• Provides potential biomarkers and therapeutic targets.
• Requires advanced CRISPR models for mechanistic studies [1, 5, 6].
What Happens During lipid ubiquitination?
Activation and Conjugation of Ubiquitin
In simple terms: Ubiquitin is first activated and then passed to an enzyme that can attach it to a lipid.
The process begins with the ATP-dependent activation of ubiquitin by the E1 enzyme UBA1, followed by transfer to an E2 ubiquitin-conjugating enzyme such as UBE2J2. UBE2J2 sensitizes the ERAD ubiquitination cascade to changes in membrane lipid saturation, indicating that lipid environment influences E2 activity. This step is essential for providing the activated ubiquitin that will be attached to lipid substrates.
Substrate Recognition and Lipid Targeting
In simple terms: Specific enzymes recognize lipid targets and bring ubiquitin to them.
E3 ubiquitin ligases confer substrate specificity. For example, RNF213 ubiquitinates lipopolysaccharide during bacterial infection, targeting it for host defense. ITCH, in complex with SPG20, mediates lysophagy initiation by ubiquitinating lipids on damaged lysosomes. The recognition of lipid substrates often depends on membrane composition and curvature, as seen in ERAD regulation by lipid saturation.
Formation of Ubiquitin-Lipid Conjugates
In simple terms: Ubiquitin becomes covalently attached to the lipid molecule.
The E3 ligase catalyzes the formation of an isopeptide or ester bond between the C-terminal glycine of ubiquitin and a reactive group on the lipid. This creates a ubiquitin-lipid conjugate that can serve as a signaling platform. The exact chemistry may vary depending on the lipid; for instance, lipopolysaccharide ubiquitination by RNF213 occurs on specific hydroxyl groups.
Downstream Signaling and Membrane Remodeling
In simple terms: The ubiquitin tag on lipids recruits other proteins that trigger cellular responses.
Ubiquitinated lipids recruit ubiquitin-binding proteins that mediate membrane remodeling, autophagy, or immune signaling [2, 4]. For example, ubiquitination of ER membranes by UBE3C regulates autophagy via ATG4B. In ER-phagy, lipid ubiquitination helps recruit autophagy receptors to the endoplasmic reticulum. These events lead to organelle turnover, lipid droplet dynamics, and pathogen clearance [4, 7].
Deubiquitination and Reversibility
In simple terms: Enzymes can remove ubiquitin from lipids, making the process reversible.
Deubiquitinating enzymes (DUBs) can cleave ubiquitin from lipids, allowing dynamic regulation. Although specific lipid DUBs are less characterized, the reversibility of ubiquitination is a hallmark of the ubiquitin system. This balance between ubiquitination and deubiquitination ensures proper membrane homeostasis and prevents excessive autophagy or immune activation.
Key Genes Involved in GO:0120323 lipid ubiquitination
The following genes encode enzymes and effectors that participate in or regulate lipid ubiquitination, as supported by published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| UBA1 | E1 ubiquitin-activating enzyme | Initiates ubiquitin activation for all ubiquitination pathways, including lipid ubiquitination |
| UBE2J2 | E2 ubiquitin-conjugating enzyme | Sensitizes ERAD to membrane lipid saturation |
| RNF213 | E3 ubiquitin ligase | Ubiquitinates lipopolysaccharide during bacterial infection |
| ITCH | E3 ubiquitin ligase | Mediates lysophagy initiation via SPG20-ITCH complex |
| UBE3C | E3 ubiquitin ligase | Tunes autophagy via ATG4B ubiquitination |
| ATG4B | Cysteine protease | Regulated by ubiquitination to control autophagy |
| SPG20 | Adaptor protein | Forms complex with ITCH for lysophagy |
| ER-phagy receptors | Autophagy receptors | Recognize ubiquitinated ER membranes |
| Lipid metabolism enzymes | Lipid synthesis and remodeling | Linked to ubiquitination in lipid metabolism |
| UBXN proteins | Ubiquitin-binding adaptors | May recognize ubiquitinated lipids |
| Proteasome subunits | Degradation machinery | Potential crosstalk with lipid ubiquitination |
| Autophagy machinery | Autophagosome formation | Downstream of lipid ubiquitination [1, 3] |
| Innate immune sensors | Pathogen detection | RNF213-mediated lipopolysaccharide ubiquitination |
| Membrane trafficking proteins | Vesicle transport | Regulated by lipid ubiquitination |
| DUBs | Deubiquitinating enzymes | Reverse lipid ubiquitination |
| E2 variants | Ubiquitin conjugation | Potential lipid substrate specificity |
| E3 ligases | Substrate recognition | Diverse roles in lipid ubiquitination [6, 7] |
How Is lipid ubiquitination Regulated?
Lipid ubiquitination is regulated at multiple levels. The availability of ubiquitin, E1, E2, and E3 enzymes determines the rate of conjugate formation. Membrane lipid composition, particularly saturation, can influence E2 activity, as shown for UBE2J2 in ERAD. Cellular stress conditions, such as bacterial infection or lysosomal damage, trigger specific E3 ligases like RNF213 and ITCH to ubiquitinate lipids [6, 7]. Autophagy-related signals also modulate lipid ubiquitination through UBE3C and ATG4B. Additionally, deubiquitinating enzymes provide a counterbalance, ensuring reversibility. The integration of these signals allows cells to adapt membrane dynamics to environmental cues.
lipid ubiquitination and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| RNF213 | Moyamoya disease, mycobacterial infection | Knockout mice, infection models |
| ITCH | Neurodegeneration, autoimmune disorders | Conditional knockout, lysophagy assays |
| UBE3C | Cancer, autophagy dysregulation | Knockout cell lines, xenografts |
| UBE2J2 | Metabolic stress, ERAD dysfunction | Point-mutation knock-in, lipid saturation models |
| ATG4B | Cancer, autophagy-related diseases | Overexpression and knockout models |
Cancer
Dysregulation of ubiquitination pathways, including lipid ubiquitination, is increasingly linked to cancer. Alterations in E3 ligases such as ITCH and UBE3C can affect autophagy and cell survival, contributing to tumorigenesis [3, 6]. Lipid metabolism reprogramming is a hallmark of cancer, and lipid ubiquitination may influence membrane remodeling and signaling in cancer cells. Targeting lipid ubiquitination enzymes could offer new therapeutic strategies.
Neurodegeneration
Defects in autophagy and ER-phagy, processes regulated by lipid ubiquitination, are implicated in neurodegenerative diseases [1, 3]. For example, impaired lysophagy due to ITCH dysfunction may lead to accumulation of damaged lysosomes, a feature of neurodegeneration. Mutations in SPG20 cause hereditary spastic paraplegia, and its role in lysophagy suggests a link to lipid ubiquitination. Modulating lipid ubiquitination may protect neurons from proteotoxic stress.
Infectious Diseases
RNF213-mediated ubiquitination of lipopolysaccharide is a critical host defense mechanism against bacterial pathogens. Polymorphisms in RNF213 are associated with susceptibility to mycobacterial infections and Moyamoya disease, highlighting the importance of lipid ubiquitination in immunity. Understanding this process could inform vaccine development and antimicrobial therapies.
Metabolic Disorders
Lipid ubiquitination is intertwined with lipid metabolism, and its dysregulation may contribute to obesity, diabetes, and fatty liver disease. UBE2J2 senses membrane lipid saturation and adjusts ERAD, linking lipid stress to protein quality control. Therapeutic targeting of lipid ubiquitination pathways could improve metabolic health.
From lipid ubiquitination-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of RNF213 affect lipopolysaccharide ubiquitination? | RNF213 knockout cells and infection assays |
| How does UBE2J2 point mutation alter ERAD under lipid saturation? | UBE2J2 point-mutation knock-in cells |
| Can ITCH knockout impair lysophagy? | ITCH knockout cells with lysosomal damage |
| Does UBE3C overexpression enhance autophagy? | UBE3C overexpression cell lines |
| What is the role of lipid ubiquitination in ER-phagy? | Tagged knock-in of ER-phagy receptors |
| Can CRISPR library screening identify new lipid ubiquitination regulators? | Genome-wide CRISPR knockout library |
How to Study the lipid ubiquitination Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Mass spectrometry | Ubiquitin-lipid conjugates | Discovery of lipid substrates |
| Lipidomics | Lipid species profiles | Identifying ubiquitinated lipids |
| Fluorescence microscopy | Localization of ubiquitin and lipids | Visualizing ER-phagy and lysophagy [1, 6] |
| CRISPR knockout screening | Gene function in lipid ubiquitination | Identifying novel regulators |
| In vitro ubiquitination assay | Enzymatic activity | Reconstituting lipid ubiquitination [2, 7] |
| Immunoprecipitation | Protein-protein interactions | Isolating ubiquitinated lipid complexes |
| RNA-seq | Transcriptional changes | Assessing pathway activation |
| Ribo-seq | Translation efficiency | Measuring stress responses |
Proteomics and Lipidomics
Mass spectrometry-based proteomics can identify ubiquitin-lipid conjugates and interacting proteins. Lipidomics complements this by profiling lipid species that are ubiquitinated. These methods are essential for discovering new substrates and enzymes in lipid ubiquitination [2, 4].
Imaging and Fluorescence Microscopy
Fluorescently tagged ubiquitin and lipid markers allow visualization of lipid ubiquitination at membranes [1, 6]. Live-cell imaging can track ER-phagy and lysophagy dynamics in real time [1, 6]. Super-resolution microscopy can resolve nanoscale ubiquitin-lipid clusters.
CRISPR Screening and Functional Genomics
Genome-wide CRISPR knockout or activation screens can identify genes that regulate lipid ubiquitination. These screens are powerful for uncovering novel E3 ligases or DUBs. Follow-up validation with targeted knockouts confirms hits [1, 5].
Biochemical Assays
In vitro ubiquitination assays with recombinant E1, E2, E3, and lipid substrates can reconstitute the reaction [2, 7]. These assays measure conjugate formation and enzyme kinetics. They are critical for mechanistic studies of lipid ubiquitination.
How CRISPR Can Be Used to Study GO:0120323 lipid ubiquitination
Knockout
CRISPR knockout of genes such as RNF213, ITCH, or UBE3C can abolish lipid ubiquitination and reveal loss-of-function phenotypes [3, 6, 7]. Knockout cell lines are valuable for studying autophagy, ERAD, and infection [1, 5]. These models help establish causality between lipid ubiquitination and cellular processes.
Point Mutation
Point mutations in catalytic residues of E2 or E3 enzymes can dissect enzymatic activity without affecting protein stability. For example, UBE2J2 point mutants can test its role in sensing lipid saturation. Such models are ideal for separating ubiquitination from other functions.
Knock-in
Knock-in of tagged ubiquitin or lipid-binding domains allows tracking of lipid ubiquitination in live cells. Tagged knock-in of ER-phagy receptors can monitor their recruitment to ubiquitinated membranes. This approach provides spatial and temporal resolution.
Overexpression
Overexpression of E3 ligases like UBE3C or RNF213 can enhance lipid ubiquitination and amplify downstream effects [3, 7]. Overexpression models are useful for gain-of-function studies and drug screening. They complement knockout approaches to establish sufficiency.
How EDITGENE Supports lipid ubiquitination Research
Researchers studying lipid ubiquitination-related genes often need to determine whether a candidate gene is causally involved in the process or merely correlated with it. CRISPR-based models provide the gold standard for establishing causality, and EDITGENE offers a comprehensive suite of services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for lipid ubiquitination research.
Frequently Asked Questions About lipid ubiquitination
What is lipid ubiquitination?
Lipid ubiquitination is the biological process in which one or more ubiquitin groups are added to a lipid molecule, as defined by GO:0120323.
What genes are involved in lipid ubiquitination?
Key genes include UBA1, UBE2J2, RNF213, ITCH, UBE3C, and ATG4B, among others [2, 3, 5, 6, 7].
What is the GO ID for lipid ubiquitination?
The GO ID is GO:0120323.
How does lipid ubiquitination regulate autophagy?
Lipid ubiquitination recruits autophagy receptors to membranes, controlling ER-phagy and lysophagy [1, 6].
Is lipid ubiquitination reversible?
Yes, deubiquitinating enzymes can remove ubiquitin from lipids, making the process reversible.
What diseases are linked to lipid ubiquitination?
Dysregulation is implicated in cancer, neurodegeneration, infectious diseases, and metabolic disorders [4, 7].
Which enzymes catalyze lipid ubiquitination?
E1 (UBA1), E2 (UBE2J2), and E3 ligases (RNF213, ITCH, UBE3C) catalyze the reaction [3, 5, 6, 7].
How can I study lipid ubiquitination in the lab?
Use CRISPR knockout, point mutation, knock-in, overexpression models, proteomics, lipidomics, and imaging [1, 4, 5].
What is the role of RNF213 in lipid ubiquitination?
RNF213 ubiquitinates lipopolysaccharide during bacterial infection, acting as a host defense mechanism.
Does lipid ubiquitination occur on the endoplasmic reticulum?
Yes, lipid ubiquitination on the ER regulates ER-phagy and ERAD [1, 5].
Conclusion
Lipid ubiquitination (GO:0120323) is a rapidly growing area of research that extends the ubiquitin code to lipids, with critical roles in membrane remodeling, autophagy, immunity, and disease [2, 4]. The identification of key enzymes such as RNF213, ITCH, and UBE2J2 has provided mechanistic insights into how lipid ubiquitination controls ER-phagy, lysophagy, and ERAD [1, 5, 6, 7]. As the field advances, CRISPR-based models will be indispensable for dissecting causal relationships and developing therapeutic strategies. EDITGENE is committed to supporting this research with tailored gene-editing services.
References
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- 2. Dikic I et al.. 2023. An expanded lexicon for the ubiquitin code.. Nat Rev Mol Cell Biol 24(4):273-287 PMID: 36284179
- 3. Sun C et al.. 2024. UBE3C tunes autophagy via ATG4B ubiquitination.. Autophagy 20(3):645-658 PMID: 38146933
- 4. Loix M et al.. 2024. The ubiquitous role of ubiquitination in lipid metabolism.. Trends Cell Biol 34(5):416-429 PMID: 37770289
- 5. Vrentzou A et al.. 2025. UBE2J2 sensitizes the ERAD ubiquitination cascade to changes in membrane lipid saturation.. Nat Commun 16(1):8973 PMID: 41068091
- 6. Gahlot P et al.. 2024. Lysosomal damage sensing and lysophagy initiation by SPG20-ITCH.. Mol Cell 84(8):1556-1569.e10 PMID: 38503285
- 7. Otten EG et al.. 2021. Ubiquitylation of lipopolysaccharide by RNF213 during bacterial infection.. Nature 594(7861):111-116 PMID: 34012115
