GO:0016562 protein import into peroxisome matrix, receptor recycling: Mechanism, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0016562 describes the step in peroxisomal matrix protein import in which peroxisome targeting sequence (PTS) receptors release their cargo and are returned to the cytosol for further rounds of import.
• The process is essential for maintaining a functional peroxisomal import cycle and for preventing receptor depletion at the peroxisomal membrane.
• PEX5 is the major PTS1 receptor; its recycling involves ubiquitination, extraction from the membrane by AAA-ATPases, and deubiquitination.
• Defects in receptor recycling are linked to peroxisome biogenesis disorders, including Zellweger spectrum disorders, and to broader cellular stress responses.
• Key experimental approaches include fluorescence imaging of tagged PEX5, ubiquitination assays, and proteomic analysis of peroxisomal fractions.
• CRISPR-based knockout, point-mutation, and knock-in models are powerful tools for dissecting the molecular requirements of receptor recycling.
Description
Peroxisomes are single-membrane organelles that carry out essential metabolic functions, including fatty acid oxidation and detoxification of reactive oxygen species. Most peroxisomal matrix proteins are synthesized in the cytosol and imported post-translationally via peroxisome targeting sequences (PTSs) that are recognized by soluble receptors. The import cycle requires not only cargo delivery but also the efficient recycling of the receptors back to the cytosol, a process captured by the Gene Ontology term GO:0016562, protein import into peroxisome matrix, receptor recycling. This term specifically refers to the dissociation of peroxisome targeting sequence receptors from cargo proteins and their return to the cytosol, which is a prerequisite for sustained import activity. Receptor recycling is a highly regulated and energy-dependent process. In mammals, the PTS1 receptor PEX5 is monoubiquitinated at a conserved cysteine residue, extracted from the peroxisomal membrane by the AAA-ATPase complex PEX1/PEX6, and then deubiquitinated in the cytosol to allow another round of import. The PTS2 receptor PEX7 follows a distinct but conceptually similar recycling route, often assisted by co-receptors. Because defects in these steps lead to peroxisomal protein import deficiencies, receptor recycling is a focal point for understanding peroxisome biogenesis disorders and for developing therapeutic strategies. For researchers, GO:0016562 provides a precise framework to annotate genes and experimental observations related to the terminal steps of peroxisomal matrix protein import. Studies using yeast, mammalian cells, and plant models have revealed conserved and organism-specific features of receptor recycling. This article integrates authoritative QuickGO data with verified PubMed literature to summarize the mechanism, key genes, disease relevance, and research methods associated with this GO term.
protein import into peroxisome matrix, receptor recycling At A Glance
| GO ID | GO:0016562 |
|---|---|
| GO term | protein import into peroxisome matrix, receptor recycling |
| Ontology | biological_process |
| Synonym | peroxisome matrix protein import, receptor recycling; peroxisome receptor recycling; PTS receptor recycling; receptor recycling during peroxisome matrix protein import |
| Major function | Releases PTS receptors from cargo and returns them to the cytosol to sustain peroxisomal matrix protein import |
| Cellular location | Peroxisomal membrane and cytosol |
| Key molecular players | PEX5, PEX7, PEX1, PEX6, PEX10, PEX12, PEX13, PEX14, ubiquitin-conjugating enzymes, deubiquitinases |
| Energy requirement | ATP-dependent extraction of receptors by AAA-ATPases |
| Related disorders | Peroxisome biogenesis disorders, including Zellweger spectrum disorders |
What Is GO:0016562?
GO:0016562, protein import into peroxisome matrix, receptor recycling, is defined as the process in which peroxisome targeting sequence receptors dissociate from cargo proteins and are returned to the cytosol. This step completes the peroxisomal matrix protein import cycle by regenerating free receptors that can engage newly synthesized cargo in the cytosol.
Why Is protein import into peroxisome matrix, receptor recycling Important in Cell Biology?
Receptor recycling is essential for maintaining the peroxisomal matrix protein import cycle and thus for the organelle's metabolic functions. Without efficient recycling, receptors become trapped at the peroxisomal membrane, leading to import deficiency and impaired peroxisomal metabolism. This process is also a quality-control node that integrates ubiquitination, ATP-dependent extraction, and deubiquitination, making it a sensitive indicator of peroxisomal health and a potential target for therapeutic intervention in peroxisome biogenesis disorders.
• Sustains peroxisomal matrix protein import by regenerating free PTS receptors.
• Prevents receptor depletion and accumulation at the peroxisomal membrane.
• Links peroxisomal import to cellular ubiquitin and ATP-dependent quality-control pathways.
• Defects cause peroxisome biogenesis disorders such as Zellweger spectrum disorders.
• Provides a mechanistic explanation for clinical phenotypes associated with PEX gene mutations.
• Serves as a model for studying receptor recycling in other organellar import systems.
• Enables functional annotation of uncharacterized PEX genes and interacting proteins.
• Offers targets for small-molecule or genetic modulation of peroxisomal activity.
• Facilitates cross-species comparisons of peroxisome biogenesis mechanisms.
• Supports the development of diagnostic and experimental biomarkers for peroxisomal dysfunction.
What Happens During protein import into peroxisome matrix, receptor recycling?
Cargo Release and Receptor Dissociation
In simple terms: The receptor lets go of its cargo inside the peroxisome.
After delivering a PTS-containing cargo protein into the peroxisomal matrix, the receptor must release the cargo to become available for another import cycle. For PEX5, cargo release is thought to occur at the peroxisomal membrane or within the matrix, and it is coupled to conformational changes in the receptor. The dissociation step is a prerequisite for subsequent receptor ubiquitination and extraction.
Ubiquitination of the Receptor
In simple terms: The receptor gets tagged with a small protein called ubiquitin.
PEX5 is monoubiquitinated at a conserved cysteine residue by a peroxisomal ubiquitin-conjugating enzyme complex that includes PEX10 and PEX12. This ubiquitination serves as a signal for receptor extraction from the membrane. In yeast and mammals, the ubiquitination step is tightly regulated and can be modulated by the presence of cargo and by other PEX proteins.
ATP-Dependent Extraction by AAA-ATPases
In simple terms: Molecular motors pull the receptor out of the peroxisomal membrane using energy.
The AAA-ATPase complex PEX1/PEX6, often with the adaptor PEX26, recognizes ubiquitinated PEX5 and extracts it from the peroxisomal membrane into the cytosol. This step requires ATP hydrolysis and is essential for recycling. In yeast, the AAA-ATPase Cdc48p (p97 in mammals) has also been implicated in peroxisomal quality control and receptor extraction under certain conditions.
Deubiquitination and Receptor Reuse
In simple terms: The ubiquitin tag is removed so the receptor can be used again.
Once in the cytosol, PEX5 is deubiquitinated by specific deubiquitinases, allowing it to bind new cargo and re-enter the import cycle. The identity of the deubiquitinase(s) may vary by organism, but the requirement for tag removal is conserved. Failure to deubiquitinate can lead to receptor degradation or aggregation, impairing import.
Recycling of the PTS2 Receptor PEX7
In simple terms: A second receptor also needs to be recycled, but it uses different helpers.
The PTS2 receptor PEX7 follows a distinct recycling pathway that often depends on co-receptors such as PEX18/PEX20 in yeast or PEX5L in mammals. PEX7 recycling also involves ubiquitination and AAA-ATPase-mediated extraction, although the precise molecular details differ from PEX5. This diversity highlights the need for organism-specific studies of receptor recycling.
Key Genes Involved in GO:0016562 protein import into peroxisome matrix, receptor recycling
The following genes and proteins are central to GO:0016562, based on published literature on peroxisome biogenesis and receptor recycling.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PEX5 | PTS1 receptor; binds cargo, becomes ubiquitinated, and is recycled | Core component for studying receptor recycling; frequent target for knockout and tagged knock-in models |
| PEX7 | PTS2 receptor; recycled via co-receptors | Model for receptor-specific recycling mechanisms |
| PEX1 | AAA-ATPase; extracts ubiquitinated receptors | Mutations cause peroxisome biogenesis disorders; target for functional rescue studies |
| PEX6 | AAA-ATPase; partners with PEX1 in receptor extraction | Key for ATP-dependent recycling assays |
| PEX10 | RING-finger ubiquitin ligase; ubiquitinates PEX5 | Target for point mutations affecting ubiquitination |
| PEX12 | RING-finger ubiquitin ligase; partners with PEX10 | Used to dissect ubiquitination cascade |
| PEX13 | Peroxisomal membrane docking protein for PEX5 | Important for early import steps and receptor handoff |
| PEX14 | Peroxisomal membrane docking protein; interacts with PEX5 | Target for studying receptor docking and release |
| PEX26 | Adaptor for PEX1/PEX6 at the peroxisomal membrane | Relevant for extraction complex assembly |
| UBB | Ubiquitin precursor; provides ubiquitin moieties | Used in ubiquitination assays |
| UBC | Ubiquitin-conjugating enzymes; may assist PEX10/PEX12 | Candidate modifiers of receptor recycling |
| CDC48 (p97) | AAA-ATPase involved in peroxisomal quality control | Studied in yeast models of receptor extraction |
| PEX18 | Yeast co-receptor for PEX7 recycling | Model for PTS2 receptor recycling |
| PEX20 | Yeast co-receptor for PEX7 recycling | Model for PTS2 receptor recycling |
| PEX5L | Mammalian long isoform of PEX5; may assist PEX7 | Relevant for PTS2 import in mammals |
| LONP2 | Peroxisomal protease; may degrade misfolded receptors | Potential quality-control factor |
| ATG proteins | Autophagy-related proteins; may intersect with peroxisomal quality control | Studied in pexophagy and receptor turnover |
| USP30 | Mitochondrial deubiquitinase; potential analog for peroxisomal deubiquitination | Candidate for deubiquitination studies |
How Is protein import into peroxisome matrix, receptor recycling Regulated?
Receptor recycling is regulated at multiple levels. Ubiquitination of PEX5 is controlled by the peroxisomal ubiquitin-conjugating complex and can be influenced by cargo binding and PEX14 availability. ATP levels and the activity of PEX1/PEX6 determine the efficiency of receptor extraction. In yeast, Cdc48p-mediated quality control can modulate receptor turnover under stress conditions. Additionally, deubiquitination rates affect the pool of free receptor available for import. These regulatory layers ensure that peroxisomal import adapts to metabolic demands and cellular stress.
protein import into peroxisome matrix, receptor recycling and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PEX1 | Zellweger spectrum disorder | Knockout or point-mutation cell lines; patient-derived fibroblasts |
| PEX6 | Peroxisome biogenesis disorder | Knockout models; rescue with wild-type or mutant PEX6 |
| PEX10 | Peroxisome biogenesis disorder | Point mutations in RING domain; ubiquitination assays |
| PEX12 | Peroxisome biogenesis disorder | Knockout and knock-in models |
| PEX5 | Peroxisome biogenesis disorder; metabolic stress | Tagged knock-in for live-cell imaging; knockout for import assays |
Peroxisome Biogenesis Disorders
Mutations in PEX genes that participate in receptor recycling, such as PEX1, PEX6, PEX10, and PEX12, cause peroxisome biogenesis disorders, including Zellweger spectrum disorders. These disorders are characterized by defective peroxisomal matrix protein import, leading to multi-systemic symptoms such as neurological impairment, liver dysfunction, and developmental delay. The severity often correlates with the degree of recycling impairment.
Neurodegeneration
Peroxisomal dysfunction, including impaired receptor recycling, has been linked to neurodegenerative processes. The accumulation of very-long-chain fatty acids and other metabolites due to import defects can contribute to neuronal damage. Studies in model organisms suggest that compromised PEX5 recycling may exacerbate oxidative stress and neuroinflammation.
Cancer and Metabolic Stress
Altered peroxisomal metabolism is observed in some cancers, and receptor recycling efficiency may influence tumor cell survival under metabolic stress. However, direct evidence linking GO:0016562 to cancer remains limited, and further research is needed.
From protein import into peroxisome matrix, receptor recycling-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of PEX5 impair receptor recycling? | PEX5 knockout cell line |
| Which residues of PEX5 are required for ubiquitination? | Point-mutation knock-in of PEX5 cysteine mutants |
| Can wild-type PEX1 rescue recycling in patient cells? | Knock-in of wild-type PEX1 into mutant background |
| Where does PEX5 localize during recycling? | Tagged knock-in of PEX5 with fluorescent protein |
| Does overexpression of PEX6 enhance recycling? | Overexpression of PEX6 in mammalian cells |
| What is the role of Cdc48p in peroxisomal quality control? | Yeast CDC48 knockout or point mutants |
How to Study the protein import into peroxisome matrix, receptor recycling Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Fluorescence microscopy | Receptor localization and dynamics | Live-cell imaging of PEX5 recycling |
| Ubiquitination assay | Monoubiquitination of PEX5 | Testing PEX10/PEX12 requirement |
| Subcellular fractionation | Distribution of receptors between peroxisomes and cytosol | Assessing recycling efficiency |
| CRISPR knockout screen | Genes affecting receptor recycling | Identifying novel regulators |
| Proximity ligation assay | Interaction between PEX5 and PEX14 | Studying docking and release |
| ATPase activity assay | ATP hydrolysis by PEX1/PEX6 | Measuring extraction complex function |
| Western blot | Receptor levels and ubiquitination status | Validating knockout or mutant phenotypes |
| RNA-seq | Transcriptional changes upon recycling defects | Identifying compensatory pathways |
Fluorescence Imaging of Tagged Receptors
Live-cell imaging of fluorescently tagged PEX5 or PEX7 allows real-time visualization of receptor recycling between the peroxisomal membrane and the cytosol. This method can reveal defects in receptor extraction or re-import in mutant backgrounds.
Ubiquitination Assays
In vivo and in vitro ubiquitination assays using tagged ubiquitin or receptor-specific antibodies can detect monoubiquitination of PEX5. These assays are useful for testing the requirement of PEX10, PEX12, and other components.
Proteomic Analysis of Peroxisomal Fractions
Subcellular fractionation followed by mass spectrometry can quantify the distribution of receptors and cargo between peroxisomes and cytosol. This approach helps assess recycling efficiency and identify interacting proteins.
Genetic Screens and CRISPR Libraries
CRISPR knockout libraries can be used to identify genes that modify receptor recycling, such as deubiquitinases or AAA-ATPase adaptors. Hit validation often involves targeted knockout or point mutations.
How CRISPR Can Be Used to Study GO:0016562 protein import into peroxisome matrix, receptor recycling
Knockout
CRISPR knockout of PEX5, PEX1, PEX6, or other recycling genes can abolish receptor recycling and cause peroxisomal import defects. These models are useful for studying the consequences of recycling loss and for testing rescue constructs.
Point Mutation
Point mutations in the ubiquitination site of PEX5 (e.g., cysteine to serine) or in the ATPase domains of PEX1/PEX6 can dissect specific steps of recycling. CRISPR-mediated point mutation allows precise modification of endogenous loci.
Knock-in
Knock-in of fluorescent or affinity tags into endogenous PEX genes enables visualization and purification of recycling complexes. This approach preserves native regulation and is ideal for live-cell imaging.
Overexpression
Overexpression of wild-type or mutant PEX proteins can enhance or disrupt recycling, respectively. This strategy is useful for gain-of-function studies and for testing dominant-negative effects.
How EDITGENE Supports protein import into peroxisome matrix, receptor recycling Research
Researchers studying protein import into peroxisome matrix, receptor recycling-related genes often need to determine whether a candidate gene is causally involved in receptor recycling or is merely correlated with peroxisomal dysfunction. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models for such functional studies.
Contact EDITGENE today to design your custom CRISPR model for protein import into peroxisome matrix, receptor recycling research.
Frequently Asked Questions About protein import into peroxisome matrix, receptor recycling
What is GO:0016562?
GO:0016562 is a Gene Ontology biological process term defined as the process in which peroxisome targeting sequence receptors dissociate from cargo proteins and are returned to the cytosol.
What genes are involved in protein import into peroxisome matrix, receptor recycling?
Key genes include PEX5, PEX7, PEX1, PEX6, PEX10, PEX12, PEX13, PEX14, and PEX26, among others.
Why is receptor recycling important for peroxisomes?
It regenerates free receptors to sustain peroxisomal matrix protein import and prevents receptor depletion.
What diseases are linked to defects in peroxisome receptor recycling?
Mutations in PEX genes cause peroxisome biogenesis disorders, including Zellweger spectrum disorders.
How is PEX5 recycled?
PEX5 is monoubiquitinated, extracted from the peroxisomal membrane by PEX1/PEX6 AAA-ATPases, and deubiquitinated in the cytosol.
What is the role of ubiquitination in receptor recycling?
Ubiquitination tags the receptor for extraction by AAA-ATPases, a prerequisite for recycling.
Which methods are used to study receptor recycling?
Common methods include fluorescence imaging, ubiquitination assays, subcellular fractionation, and CRISPR screens.
Can CRISPR be used to study GO:0016562?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect receptor recycling.
What is the difference between PEX5 and PEX7 recycling?
PEX5 is the PTS1 receptor and recycles via cysteine ubiquitination, while PEX7 is the PTS2 receptor and often requires co-receptors.
Where can I find authoritative data on GO:0016562?
QuickGO provides the official definition and annotations for GO:0016562, and PubMed literature offers experimental details.
Conclusion
GO:0016562, protein import into peroxisome matrix, receptor recycling, is a critical step in peroxisome biogenesis that ensures the continuous import of matrix proteins. The process involves cargo release, receptor ubiquitination, ATP-dependent extraction, and deubiquitination, with PEX5 and PEX7 as central receptors and PEX1/PEX6 as key AAA-ATPases. Defects in this pathway cause peroxisome biogenesis disorders and contribute to cellular stress. Researchers can leverage CRISPR-based models and a range of biochemical and imaging methods to dissect the molecular mechanisms and identify therapeutic targets.
References
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- 3. Eckert JH et al.. 2003. Peroxisome biogenesis.. Rev Physiol Biochem Pharmacol 147:75-121 PMID: 12687401
- 4. Skowyra ML et al.. 2022. PEX5 translocation into and out of peroxisomes drives matrix protein import.. Mol Cell 82(17):3209-3225.e7 PMID: 35931083
- 5. Yusuf IF et al.. 2025. Role of AAA-ATPase Cdc48p in peroxisomal quality control.. Cell Rep 44(10):116405 PMID: 41076631
- 6. Baker A et al.. 2010. Peroxisome biogenesis and positioning.. Biochem Soc Trans 38(3):807-16 PMID: 20491668
- 7. Baker A et al.. 2005. Peroxisome protein import: some answers, more questions.. Curr Opin Plant Biol 8(6):640-7 PMID: 16182600
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