GO:0045046 protein import into peroxisome membrane: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0045046 describes the targeting of proteins into the peroxisomal membrane, a process whose signals and mechanism differ from peroxisomal matrix protein import.
• Peroxisomal membrane protein (PMP) import is not fully understood but is thought to involve PEX19 as a chaperone and PEX3 as a membrane docking factor.
• Recent work proposes that PMP import occurs through a nuclear pore-like phase at the peroxisomal membrane.
• PEX13 regulates ubiquitinated PEX5 and peroxisomal ROS to prevent pexophagy, linking membrane protein import to organelle quality control.
• PEX39 was recently identified as a factor facilitating peroxisomal import of PTS2-containing proteins, expanding the known import machinery.
• Dysfunction of peroxisomal membrane protein import is linked to peroxisome biogenesis disorders and broader metabolic and neurodegenerative pathology.
Description
Protein import into peroxisome membrane (GO:0045046) is the biological process by which proteins are targeted to and inserted into the peroxisomal membrane. This process is distinct from peroxisomal matrix protein import, as it uses different signals and a different mechanism that remains incompletely understood. Peroxisomes are single-membrane organelles essential for fatty acid oxidation, ether lipid synthesis, and reactive oxygen species metabolism, and their membrane must acquire a specific set of proteins to carry out these functions. Understanding how membrane proteins reach the peroxisome is therefore central to peroxisome biology and to the molecular basis of peroxisome biogenesis disorders. Unlike matrix proteins, which carry peroxisomal targeting signals PTS1 or PTS2 and are imported through a receptor cycle involving PEX5 and PEX7, peroxisomal membrane proteins (PMPs) are targeted by distinct internal signals and are inserted into the membrane through a pathway that is still being defined. Several models have been proposed, including direct insertion from the cytosol and insertion via the endoplasmic reticulum, and recent evidence suggests that PMP import may involve a nuclear pore-like phase at the peroxisomal membrane. Key proteins implicated in this process include PEX19, a cytosolic chaperone and import receptor for PMPs, and PEX3, a membrane anchor that receives PMP cargo. For researchers, GO:0045046 provides a precise ontology handle for annotating genes, designing functional screens, and interpreting proteomic or imaging data focused on peroxisomal membrane biogenesis. Because the mechanism is not fully resolved, the term also marks an active area of cell biology where CRISPR-based models, live-cell imaging, and biochemical reconstitution can make important contributions.
protein import into peroxisome membrane At A Glance
| GO ID | GO:0045046 |
|---|---|
| GO term | protein import into peroxisome membrane |
| Ontology | biological_process |
| Synonym | peroxisome membrane protein import; protein transport into peroxisome membrane |
| Major function | Targeting and insertion of proteins into the peroxisomal membrane |
| Distinct from | Peroxisomal matrix protein import (PTS1/PTS2 pathways) |
| Key machinery | PEX19 chaperone/receptor, PEX3 docking factor, and associated membrane proteins |
| Emerging model | Nuclear pore-like phase at the peroxisomal membrane |
| Disease relevance | Peroxisome biogenesis disorders and related metabolic/neurodegenerative conditions |
What Is GO:0045046?
GO:0045046, protein import into peroxisome membrane, is defined as the targeting of proteins into the peroxisomal membrane. The process is not well understood, but both the signals and the mechanism differ from those involved in peroxisomal matrix protein import. In other words, it covers the steps by which newly synthesized membrane proteins are recognized, delivered to the peroxisome, and inserted into its membrane, as opposed to the import of soluble enzymes into the peroxisomal lumen.
Why Is protein import into peroxisome membrane Important in Cell Biology?
GO:0045046 is important because the peroxisomal membrane must acquire a specific complement of proteins to support essential metabolic functions, including fatty acid oxidation, plasmalogen synthesis, and ROS detoxification. Defects in peroxisome biogenesis, including membrane protein import, cause peroxisome biogenesis disorders with severe neurological and metabolic phenotypes. Because the mechanism of PMP import is distinct from matrix protein import, it represents a unique cell biological problem and a potential target for understanding organelle assembly and quality control.
• Defines a distinct protein targeting pathway that is separate from PTS1/PTS2 matrix import.
• Required for building the peroxisomal membrane and maintaining organelle function.
• Linked to peroxisome biogenesis disorders and metabolic disease.
• PEX13 regulates ubiquitinated PEX5 and peroxisomal ROS to prevent pexophagy, connecting import to organelle turnover.
• PEX39 facilitates PTS2 protein import, showing crosstalk between import subsystems.
• Provides a model for studying membrane protein insertion outside the ER/mitochondria.
• Relevant to neurodegeneration and developmental disorders associated with peroxisomal dysfunction.
• Offers targets for CRISPR screens and imaging-based assays of organelle biogenesis.
• Connects to phase separation and nuclear pore-like mechanisms in organelle biology.
• Supports annotation and functional genomics of peroxisomal membrane proteins.
What Happens During protein import into peroxisome membrane?
Recognition of membrane protein cargo
In simple terms: The cell must first recognize which proteins belong in the peroxisome membrane.
Peroxisomal membrane proteins (PMPs) carry internal targeting signals that are distinct from the PTS1 and PTS2 signals used by matrix proteins. PEX19 is thought to act as a cytosolic chaperone and import receptor that binds newly synthesized PMPs and protects them during delivery to the peroxisome. This recognition step is a key point of regulation and a major focus of current research because the exact signal motifs are still being defined.
Docking at the peroxisomal membrane
In simple terms: The cargo-loaded receptor docks onto the peroxisome surface.
PEX3 is a peroxisomal membrane protein that serves as a docking factor for the PEX19-cargo complex. The interaction between PEX19 and PEX3 is believed to be a central step in PMP import, and disruption of this interaction impairs membrane protein targeting. Recent models suggest that the docking and insertion steps may involve a nuclear pore-like phase at the peroxisomal membrane, providing a new framework for understanding how PMPs are translocated.
Insertion into the membrane
In simple terms: The protein is inserted into the peroxisomal membrane.
After docking, PMPs are inserted into the peroxisomal membrane, a step that is not fully understood but is thought to require additional factors and possibly a translocon-like assembly. The process differs from matrix protein import, which uses a receptor cycle involving PEX5 and PEX7 and a matrix protein import machinery. The insertion step is a major gap in knowledge and an active area for biochemical and imaging studies.
Quality control and pexophagy regulation
In simple terms: The cell monitors import and can degrade damaged peroxisomes.
PEX13 prevents pexophagy by regulating ubiquitinated PEX5 and peroxisomal ROS, linking membrane protein import to organelle quality control. This suggests that defects in PMP import or associated machinery can trigger selective autophagy of peroxisomes, a process relevant to cellular stress responses and disease. Understanding this crosstalk is important for interpreting phenotypes of import mutants.
Phase separation and nuclear pore-like model
In simple terms: Import may occur through a specialized phase at the membrane.
Recent studies propose that protein import into peroxisomes occurs through a nuclear pore-like phase, and that peroxisome biogenesis can be initiated by protein phase separation. These findings suggest that PMP import may involve liquid-liquid phase separation and a distinct structural organization at the peroxisomal membrane. This model is still emerging and requires further validation but offers a new conceptual framework for the field.
Key Genes Involved in GO:0045046 protein import into peroxisome membrane
The following genes and proteins have been implicated in protein import into peroxisome membrane (GO:0045046) and related peroxisomal biogenesis processes.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PEX19 | Cytosolic chaperone and import receptor for peroxisomal membrane proteins | Central to PMP targeting; knockout causes severe peroxisome biogenesis defects |
| PEX3 | Peroxisomal membrane docking factor for PEX19-cargo complex | Essential for PMP insertion; mutations cause peroxisome biogenesis disorders |
| PEX13 | Regulates ubiquitinated PEX5 and peroxisomal ROS to prevent pexophagy | Links import to organelle quality control; knockout affects pexophagy |
| PEX5 | Matrix protein import receptor; also involved in ubiquitination and pexophagy regulation | Crosstalk with membrane protein import and quality control |
| PEX7 | Matrix protein import receptor for PTS2 proteins | Distinct from PMP import but relevant to overall peroxisome function |
| PEX39 | Facilitates peroxisomal import of PTS2-containing proteins | Newly identified factor; expands import machinery |
| PEX1 | AAA-ATPase involved in peroxisome biogenesis | Mutations cause peroxisome biogenesis disorders |
| PEX6 | AAA-ATPase involved in peroxisome biogenesis | Mutations cause peroxisome biogenesis disorders |
| PEX10 | RING finger protein involved in matrix protein import | Relevant to overall peroxisome biogenesis |
| PEX12 | RING finger protein involved in matrix protein import | Relevant to overall peroxisome biogenesis |
| PEX14 | Peroxisomal membrane protein involved in matrix protein import | Docking factor for PEX5; relevant to import machinery |
| PEX2 | RING finger protein involved in matrix protein import | Relevant to peroxisome biogenesis |
| PEX26 | Recruits PEX1/PEX6 to peroxisomal membrane | Relevant to peroxisome biogenesis |
| PEX16 | Peroxisomal membrane protein involved in peroxisome biogenesis | Relevant to membrane assembly |
| PEX11 | Peroxisomal membrane protein involved in peroxisome proliferation | Relevant to organelle dynamics |
| PEX18 | Involved in PTS2 import in yeast | Model organism studies of import |
| PEX21 | Involved in PTS2 import in yeast | Model organism studies of import |
| PEX8 | Peroxisomal matrix protein involved in import | Relevant to import cycle |
How Is protein import into peroxisome membrane Regulated?
The regulation of protein import into peroxisome membrane is not fully understood, but several layers of control have been proposed. PEX13 regulates ubiquitinated PEX5 and peroxisomal ROS to prevent pexophagy, indicating that import is coupled to organelle quality control. The process may also be influenced by phase separation and the nuclear pore-like phase model, which could provide a regulatory mechanism for cargo selection and insertion. Additionally, the interplay between matrix and membrane protein import pathways suggests that overall peroxisome biogenesis is coordinated, although specific signaling pathways remain to be defined.
protein import into peroxisome membrane and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PEX19 | Peroxisome biogenesis disorder | Knockout cell line; rescue with wild-type or mutant PEX19 |
| PEX3 | Peroxisome biogenesis disorder | Knockout cell line; imaging of peroxisomal membrane |
| PEX13 | Pexophagy dysregulation and ROS stress | Knockout cell line; pexophagy assays |
| PEX5 | Matrix protein import defect and pexophagy | Point mutation knock-in; ubiquitination assays |
| PEX39 | PTS2 import defect | Knockout cell line; PTS2 reporter import assay |
Peroxisome biogenesis disorders
Mutations in genes required for peroxisome biogenesis, including PEX19 and PEX3, cause peroxisome biogenesis disorders with severe neurological and metabolic phenotypes. Defects in protein import into peroxisome membrane contribute to the loss of functional peroxisomes and the accumulation of very long-chain fatty acids. These disorders highlight the clinical importance of understanding PMP import mechanisms.
Neurodegeneration and metabolic disease
Peroxisomal dysfunction is linked to neurodegeneration and metabolic disease, and membrane protein import is essential for maintaining peroxisomal functions such as plasmalogen synthesis and fatty acid oxidation. Disruption of PMP import may therefore contribute to neuronal damage and metabolic imbalance. Research into GO:0045046 could inform therapeutic strategies for these conditions.
Cancer and cellular stress
Peroxisomal ROS metabolism and pexophagy regulation are connected to cellular stress responses, and PEX13-mediated control of ubiquitinated PEX5 and ROS prevents pexophagy. Dysregulation of these processes may influence cancer cell survival and stress adaptation, although direct links to PMP import remain to be fully established. Further studies are needed to clarify the role of GO:0045046 in cancer biology.
From protein import into peroxisome membrane-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is PEX19 required for PMP import? | PEX19 knockout cell line |
| Does a specific PMP signal motif direct import? | Point mutation knock-in of candidate signal |
| Can a tagged PMP be tracked in live cells? | Tagged knock-in of PMP with fluorescent tag |
| Does overexpression of PEX3 enhance import? | Overexpression cell line |
| Which genes regulate pexophagy upon import stress? | CRISPR library screening |
| Does a disease-associated mutation impair import? | Knock-in of patient mutation |
How to Study the protein import into peroxisome membrane Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Fluorescence microscopy | Localization and dynamics of tagged PMPs | Live-cell imaging of import |
| Proteomics | Protein interactions and cargo identification | Mapping PEX19/PEX3 interactome |
| CRISPR knockout screen | Genes required for PMP import | Discovery of new import factors |
| Reporter import assay | Efficiency of PMP targeting | High-throughput screening |
| Phase separation assay | Liquid-liquid phase separation of import components | Testing nuclear pore-like model |
| Pexophagy assay | Autophagic degradation of peroxisomes | Quality control studies |
| Ubiquitination assay | PEX5 ubiquitination status | Regulation by PEX13 |
Fluorescence imaging of peroxisomal membrane proteins
Live-cell fluorescence imaging using tagged PMPs allows tracking of import and insertion into the peroxisomal membrane. This approach can reveal dynamic intermediates and the nuclear pore-like phase proposed for PMP import. High-resolution microscopy is essential for studying this process in situ.
Proteomics and interactomics
Proteomic approaches can identify PMP cargo and interactors of PEX19 and PEX3, helping to define the import machinery. Affinity purification coupled to mass spectrometry is useful for mapping the PMP import complex. These methods complement genetic screens and imaging.
CRISPR screens and functional genomics
CRISPR knockout screens can identify genes required for PMP import and peroxisome biogenesis. Reporter-based assays for PMP localization enable high-throughput screening. Such screens can uncover new factors like PEX39.
Biochemical reconstitution and phase separation assays
In vitro reconstitution and phase separation assays can test whether PMP import involves liquid-liquid phase separation. These approaches help validate the nuclear pore-like phase model. They are complementary to cell-based studies.
How CRISPR Can Be Used to Study GO:0045046 protein import into peroxisome membrane
Knockout
CRISPR knockout of PEX19, PEX3, or PEX13 can abolish or impair protein import into peroxisome membrane, providing causal evidence for their roles. Knockout cell lines are valuable for rescue experiments and for assessing downstream effects on peroxisomal metabolism. These models help define the essential components of the import pathway.
Point Mutation
Point mutation knock-in can be used to test the function of specific residues in PEX19 or PEX3, such as those involved in cargo binding or docking. This approach can dissect the molecular details of PMP recognition and insertion. It is also useful for modeling patient mutations.
Knock-in
Tagged knock-in of PMPs or import machinery components enables live-cell imaging and proteomic analysis without overexpression artifacts. Knock-in of fluorescent tags can reveal real-time import dynamics. This strategy is powerful for studying the nuclear pore-like phase model.
Overexpression
Overexpression of PEX19, PEX3, or candidate PMPs can enhance or saturate the import pathway, helping to identify rate-limiting steps. Overexpression models are useful for biochemical purification of import complexes. They can also reveal dominant-negative effects of mutant proteins.
How EDITGENE Supports protein import into peroxisome membrane Research
Researchers studying protein import into peroxisome membrane-related genes often need to determine whether a candidate gene is causally involved in PMP targeting, how specific mutations affect import, and which factors regulate the pathway. EDITGENE provides a comprehensive suite of CRISPR-based services to address these questions with publication-grade rigor.
Contact EDITGENE today to design your custom CRISPR model for protein import into peroxisome membrane research.
Frequently Asked Questions About protein import into peroxisome membrane
What is protein import into peroxisome membrane (GO:0045046)?
It is the biological process of targeting proteins into the peroxisomal membrane, using signals and mechanisms distinct from peroxisomal matrix protein import.
What genes are involved in protein import into peroxisome membrane?
Key genes include PEX19, PEX3, PEX13, and other PEX genes, with emerging roles for PEX39 and matrix import factors.
How does peroxisomal membrane protein import differ from matrix protein import?
Membrane protein import uses internal signals and PEX19/PEX3, while matrix import uses PTS1/PTS2 signals and PEX5/PEX7.
What is the role of PEX19 in peroxisome membrane protein import?
PEX19 acts as a cytosolic chaperone and import receptor that binds PMPs and delivers them to PEX3 at the peroxisome.
What is the role of PEX3 in peroxisome membrane protein import?
PEX3 is a membrane docking factor that receives PEX19-cargo complexes and facilitates PMP insertion.
Is protein import into peroxisome membrane understood?
No, the process is not well understood, and current models include direct insertion and a nuclear pore-like phase.
What diseases are linked to defects in peroxisome membrane protein import?
Peroxisome biogenesis disorders, neurodegeneration, and metabolic diseases are linked to impaired peroxisomal biogenesis.
How can CRISPR be used to study protein import into peroxisome membrane?
CRISPR knockout, point mutation, knock-in, and overexpression models can test gene function and model patient mutations.
What methods are used to study peroxisomal membrane protein import?
Fluorescence imaging, proteomics, CRISPR screens, and phase separation assays are commonly used.
What is the nuclear pore-like phase model for peroxisome protein import?
It proposes that protein import into peroxisomes occurs through a nuclear pore-like phase, based on recent evidence.
Conclusion
GO:0045046, protein import into peroxisome membrane, defines a distinct and still poorly understood pathway for building the peroxisomal membrane. Key factors such as PEX19 and PEX3 have been identified, and emerging models involving phase separation and a nuclear pore-like phase are reshaping the field. Defects in this process are linked to peroxisome biogenesis disorders and broader metabolic and neurodegenerative disease. Continued research using CRISPR models, imaging, and proteomics will be essential to fully resolve the mechanism and its disease relevance.
References
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- 2. Kumar R et al.. 2024. The peroxisome: an update on mysteries 3.0.. Histochem Cell Biol 161(2):99-132 PMID: 38244103
- 3. Okumoto K et al.. 2020. Peroxisome: Metabolic Functions and Biogenesis.. Adv Exp Med Biol 1299:3-17 PMID: 33417203
- 4. Ravindran R et al.. 2023. Peroxisome biogenesis initiated by protein phase separation.. Nature 617(7961):608-615 PMID: 37165185
- 5. Demers ND et al.. 2023. PEX13 prevents pexophagy by regulating ubiquitinated PEX5 and peroxisomal ROS.. Autophagy 19(6):1781-1802 PMID: 36541703
- 6. Skowyra ML et al.. 2024. Towards solving the mystery of peroxisomal matrix protein import.. Trends Cell Biol 34(5):388-405 PMID: 37743160
- 7. Chen WW et al.. 2025. PEX39 facilitates the peroxisomal import of PTS2-containing proteins.. Nat Cell Biol 27(8):1256-1271 PMID: 40739340
- 8. Walter T et al.. 2019. Current Advances in Protein Import into Peroxisomes.. Protein J 38(3):351-362 PMID: 31054036
