PEX6 Protein
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">PEX6 Protein - Peroxisome Biogenesis Factor 6</th>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>Pex6p (Peroxin-6)</td>
</tr>
<tr>
<td class="label">Gene</td>
<td>PEX6</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9Y5X3</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~104 kDa</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Peroxisomal membrane and cytosol</td>
</tr>
<tr>
<td class="label">AAA ATPase Family</td>
<td>Type I peroxin</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>6p21.1</td>
</tr>
<tr>
<td class="label">Disorder</td>
<td>Phenotype Severity</td>
</tr>
<tr>
<td class="label">Zellweger Syndrome</td>
<td>Severe</td>
</tr>
<tr>
<td class="label">Neonatal Adrenoleukodystrophy (NALD)</td>
<td>Intermediate</td>
</tr>
<tr>
<td class="label">Infantile Refsum Disease</td>
<td>Milder</td>
</tr>
<tr>
<td class="label">Mutation Type</td>
<td>Examples</td>
</tr>
<tr>
<td class="label">Missense</td>
<td>p.Y428C, p.L664P</td>
</tr>
<tr>
<td class="label">Nonsense</td>
<td>p.R398X, p.Q857X</td>
</tr>
<tr>
<td class="label">Frameshift</td>
<td>c.1654delC</td>
</tr>
<tr>
<td class="label">Splice site</td>
<td>c.2128-1G>A</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
Introduction
PEX6 (Peroxisome Biogenesis Factor 6) is a key AAA ATPase protein essential for peroxisome biogenesis and function. It partners with PEX1 in the peroxisomal targeting receptor recycling pathway and plays critical roles in maintaining cellular homeostasis, particularly in [neurons](/entities/neurons) where peroxisomes are essential for lipid metabolism and [reactive oxygen species](/entities/reactive-oxygen-species) (ROS) detoxification[@steinberg2004].
Overview
Structure
PEX6 is a member of the AAA (ATPases Associated with diverse cellular Activities) family:
- N-terminal domain: Contains the PEX1 interaction domain
- AAA1 domain: First ATPase domain (residues 400-550)
- AAA2 domain: Second ATPase domain (residues 560-720)
- C-terminal domain: Regulatory and membrane interaction region
The protein forms a hexameric complex with PEX1, using ATP hydrolysis to generate mechanical force for extracting PEX5 from the peroxisomal membrane[@gardner2015]. Structurally, PEX6 shares homology with other AAA ATPases including CDC48/p97 and NSF, which perform similar protein extraction functions in other cellular compartments.
Normal Function
Peroxisomal Receptor Recycling
The primary function of PEX6 (with PEX1) is recycling the peroxisomal targeting receptor PEX5:
PEX5 import: PEX5 delivers proteins with the peroxisomal targeting signal type 1 (PTS1) into the peroxisome matrix
Receptor extraction: After cargo release, PEX5 must be recycled back to the cytosol for another round of import
ATP-dependent extraction: PEX6-PEX1 complex uses ATP hydrolysis to extract PEX5 from the peroxisomal membrane[@francisco2017]
Recycling completion: Extracted PEX5 can be reused for subsequent import cyclesPeroxisome Biogenesis
PEX6 is essential for peroxisome biogenesis:
- De novo formation: Required for the initial formation of peroxisomes from the endoplasmic reticulum
- Matrix protein import: Enables import of all peroxisomal matrix proteins
- Membrane protein insertion: Facilitates insertion of peroxisomal membrane proteins
- Peroxisome division: Coordinates with the fission machinery for peroxisome proliferation
Cellular Homeostasis
Peroxisomes are essential for:
- Beta-oxidation of very long-chain fatty acids (VLCFAs)
- Biosynthesis of plasmalogens (ether phospholipids)
- Hydrogen peroxide metabolism via catalase
- Polyunsaturated fatty acid metabolism
- Bile acid synthesis
Disease Associations
Zellweger Spectrum Disorders
PEX6 mutations cause autosomal recessive peroxisome biogenesis disorders within the Zellweger spectrum[@steinberg2015]:
Rhizomelic Chondrodysplasia Punctata Type 4 (RCDP4)
Recessive PEX6 mutations cause RCDP4, characterized by:
- Rhizomelic shortening of limbs
- Chondrodysplasia punctata (calcification of growth plates)
- Severe intellectual disability
- Cataracts
- Recurrent seizures
Heimde Syndrome
A milder peroxisome biogenesis disorder caused by PEX6 mutations:
- Sensorineural hearing loss
- Enamel hypoplasia
- Mild intellectual disability
- Retinal degeneration
Neurodegenerative Diseases
While not directly causative, peroxisomal dysfunction contributes to:
Alzheimer's Disease:
- Impaired peroxisomal function in AD brain tissue
- Reduced catalase activity and increased oxidative stress
- Abnormal VLCFA metabolism
- Interaction with [amyloid-beta](/proteins/amyloid-beta) pathology[@van2020]
Parkinson's Disease:
- PEX6 expression altered in PD substantia nigra
- Role in mitophagy and mitochondrial quality control
- Potential involvement in [alpha-synuclein](/proteins/alpha-synuclein) pathology
Amyotrophic Lateral Sclerosis (ALS):
- Peroxisomal abnormalities in ALS motor neurons
- Altered lipid metabolism
- Increased oxidative stress
Expression Pattern
PEX6 is ubiquitously expressed with highest levels in:
- Brain: Neurons and glial cells, particularly in [cortex](/brain-regions/cortex), [hippocampus](/brain-regions/hippocampus), and basal ganglia
- Liver: Hepatocytes for lipid metabolism
- Kidney: Renal tubular cells
- Skeletal muscle: Myocytes for fatty acid oxidation
- Heart: Cardiac muscle for energy metabolism
In the brain, PEX6 is expressed in:
- Pyramidal neurons (cortical and hippocampal)
- Dopaminergic neurons (substantia nigra)
- [Astrocytes](/entities/astrocytes) and oligodendrocytes
- Microglial cells
The [Allen Brain Atlas](https://human.brain-map.org/microarray/search/show?search_term=PEX6) shows widespread expression across brain regions with particularly high expression in metabolically active neuronal populations.
Interaction Partners
Core Complex
- PEX1: AAA ATPase partner, forms functional heterodimer
- PEX5: Primary substrate for recycling
- PEX26: Membrane anchor for the PEX1-PEX6 complex
Peripheral Interactions
- PEX2, PEX10, PEX12: Components of the peroxisomal import machinery
- PEX11A/B/G: Peroxisome proliferation regulators
- ABCD1/2/3: Peroxisomal ABC transporters for fatty acid import
Disease-Associated Mutations
Over 40 pathogenic PEX6 mutations have been identified:
Therapeutic Implications
Current Challenges
- [Blood-brain barrier](/entities/blood-brain-barrier): Delivery of therapeutic agents to the CNS
- Timing: Intervention likely needs to precede significant neuronal loss
- Enzyme replacement: PEX6 is a large protein (~104 kDa)
Emerging Approaches
Gene Therapy:
- AAV vectors encoding functional PEX6
- CRISPR-based gene correction for specific mutations
- Antisense oligonucleotides for splice-site mutations
Pharmacological:
- PEX6 activity enhancers (experimental)
- Proteostasis modulators to improve mutant protein folding
- Antioxidants to address secondary oxidative stress
Supportive:
- Dietary management (low VLCFA diet)
- Vitamin supplementation
- Physical and occupational therapy
Research Directions
Structural studies: Cryo-EM structures of the PEX1-PEX6 complex
Patient-derived models: iPSC lines from PEX6-deficient patients
Gene therapy: AAV-PEX6 delivery in animal models
Biomarkers: Development of peroxisomal function biomarkers
Modifier genes: Understanding intrafamilial variabilityBackground
The study of peroxisome biogenesis factors has revealed critical insights into cellular metabolism and neurodegenerative disease mechanisms. PEX6, as a key component of the peroxisomal protein import machinery, is essential for maintaining peroxisome function across all tissues, with particular importance in neurons that rely on peroxisomal lipid metabolism and antioxidant defense[@waterham2014].
Historical milestones in peroxisome research include Christian de Duve's discovery of peroxisomes (Nobel Prize, 1974), identification of the peroxisome biogenesis pathway, and more recent advances in understanding the structure and function of the PEX1-PEX6 AAA ATPase complex. These discoveries have direct implications for understanding and treating peroxisome biogenesis disorders and related neurodegenerative conditions.
See Also
- [PEX6 Gene](/genes/pex6)
- [Peroxisome](/mechanisms/peroxisome-dysfunction-neurodegeneration)
- [Zellweger Syndrome](/diseases/zellweger-syndrome)
- [Rhizomelic Chondrodysplasia Punctata](/mechanisms/dopaminergic-neuron-vulnerability)
- [PEX1 Protein](/proteins/pex1-protein)
- [PEX5 Protein](/proteins/pex5-protein)
- [Peroxisome Biogenesis Disorders](/companies/biogen)
- [Very Long](/mechanisms/dopaminergic-neuron-vulnerability)
- [Proteins Index](/proteins)
External Links
- [NCBI Gene: PEX6](https://www.ncbi.nlm.nih.gov/gene/5191)
- [UniProt: Q9Y5X3](https://www.uniprot.org/uniprot/Q9Y5X3)
- [OMIM: 614920](https://www.omim.org/entry/614920)
- [Allen Brain Atlas - PEX6 Expression](https://human.brain-map.org/microarray/search/show?search_term=PEX6)
- [PeroxisomeDB](http://www.peroxisomedb.org/)
References
[Steinberg D, et al, (2004) (2004)](https://doi.org/10.1093/hmg/ddh210)
[Gardner BM, et al, (2015) (2015)](https://doi.org/10.1038/ncb3235)
[Francisco T, et al, (2017) (2017)](https://doi.org/10.1007/s00018-016-2442-4)
[Steinberg S, et al, (2015) (2015)](https://doi.org/10.1186/s13023-015-0238-5)
[Van Vliet T, et al, (2020) (2020)](https://doi.org/10.1016/j.bbadis.2020.165936)
[Waterham HR, et al, (2014) (2014)](https://doi.org/10.1146/annurev-biochem-030914-034305)