PEX3 Gene - Peroxisome Biogenesis Factor 3

PEX3 - Peroxisome Biogenesis Factor 3

Pathway Diagram

```mermaid
flowchart TD
PEX3["PEX3<br/>Peroxisome Biogenesis<br/>Factor 3"]

SQSTM1["SQSTM1/p62<br/>Autophagy Receptor"]
LC3["LC3<br/>Autophagy Marker"]
RB1CC1["RB1CC1/FIP200<br/>Autophagy Initiation"]

PARKIN["PARKIN<br/>E3 Ubiquitin Ligase"]
SNCA["SNCA<br/>alpha-Synuclein"]
SNCAIP["SNCAIP<br/>Synphilin-1"]

MFN1["MFN1<br/>Mitofusin 1<br/>Mitochondrial Fusion"]
BCL2["BCL2<br/>Anti-apoptotic<br/>Protein"]

ERN1["ERN1/IRE1alpha<br/>ER Stress<br/>Sensor"]
FAM134B["FAM134B<br/>ER-phagy<br/>Receptor"]

ATM["ATM<br/>DNA Damage<br/>Response"]
STING1["STING1<br/>Innate Immunity<br/>Signaling"]

PD["Parkinson's<br/>Disease"]
AD["Alzheimer's<br/>Disease"]
ALS["Amyotrophic<br/>Lateral Sclerosis"]
FTD["Frontotemporal<br/>Dementia"]

PEX3 -->|"regulates"| SQSTM1
SQSTM1 -->|"binds"| LC3
PEX3 -->|"interacts"| RB1CC1

PEX3 -->|"interacts"| PARKIN
PARKIN -->|"ubiquitinates"| SNCA
PEX3 -->|"interacts"| SNCAIP
SNCA -->|"aggregates"| PD

PEX3 -->|"regulates"| MFN1
PEX3 -->|"interacts"| BCL2
MFN1 -->|"maintains"| BCL2

PEX3 -->|"responds_to"| ERN1
PEX3 -->|"interacts"| FAM134B
ERN1 -->|"activates"| FAM134B

PEX3 -->|"interacts"| ATM
PEX3 -->|"modulates"| STING1
ATM -->|"triggers"| STING1

SQSTM1 -->|"dysfunction"| AD
PARKIN -->|"mutations"| PD
ERN1 -->|"stress_response"| ALS
ATM -->|"damage_response"| FTD

style PEX3 fill:#006494

PEX3 - Peroxisome Biogenesis Factor 3

Pathway Diagram

Introduction

PEX3 encodes Peroxisome Biogenesis Factor 3, an essential peroxisomal membrane protein critical for peroxisome biogenesis, peroxisomal membrane protein (PMP) import, and peroxisome proliferation. PEX3 is one of the earliest factors required for peroxisome formation and serves as the primary docking site for the peroxisomal targeting signal type 2 (PTS2) receptor complex. Mutations in PEX3 cause severe peroxisome biogenesis disorders (PBDs) and are associated with impaired peroxisomal function in neurodegenerative diseases including Alzheimer's disease and Parkinson's disease[@muntau2000]. [@muntau2000]

<div class="infobox infobox-gene"> [@steinberg2015]
<div class="infobox-header">Gene Information</div> [@kou2021]
<div class="infobox-row"> [@cook2020]
<div class="infobox-label">Gene Symbol</div> [@fujiki2020]
<div class="infobox-value">PEX3</div>
</div>
<div class="infobox-row">
<div class="infobox-label">Full Name</div>
<div class="infobox-value">Peroxisome Biogenesis Factor 3</div>
</div>
<div class="infobox-row">
<div class="infobox-label">Chromosomal Location</div>
<div class="infobox-value">6q24.2</div>
</div>
<div class="infobox-row">
<div class="infobox-label">NCBI Gene ID</div>
<div class="infobox-value">[5679](https://www.ncbi.nlm.nih.gov/gene/5679)</div>
</div>
<div class="infobox-row">
<div class="infobox-label">Ensembl ID</div>
<div class="infobox-value">ENSG00000034693</div>
</div>
<div class="infobox-row">
<div class="infobox-label">UniProt ID</div>
<div class="infobox-value">[Q9Y5Y8](https://www.uniprot.org/uniprot/Q9Y5Y8)</div>
</div>
<div class="infobox-row">
<div class="infobox-label">Protein Aliases</div>
<div class="infobox-value">Pex3p, Peroxin-3</div>
</div>
<div class="infobox-row">
<div class="infobox-label">Associated Diseases</div>
<div class="infobox-value">Zellweger Syndrome, Peroxisome Biogenesis Disorders, Alzheimer's Disease, Parkinson's Disease</div>
</div>
</div>

Overview

PEX3 is a 476-amino acid peroxisomal membrane protein that plays a central role in peroxisome biogenesis. It is evolutionarily conserved from yeast to humans and is essential for life. PEX3 functions at multiple stages of peroxisome formation:

In [neurons](/entities/neurons), PEX3 is particularly important for maintaining peroxisomal function in regions with high metabolic demand and oxidative stress, making it relevant to neurodegenerative processes.

Protein Structure

Domain Organization

PEX3 contains several functional domains:

Structural Features

• PEX19 binding motif: PH3-like domain for PEX19 interaction
• Membrane topology: Type 3 peroxisomal membrane protein
• Oligomerization: Forms homooligomers important for function

Post-Translational Modifications

• Phosphorylation: Regulates peroxisome proliferation
• Ubiquitination: Controls PEX3 turnover

Molecular Functions

Peroxisome Biogenesis

PEX3 is essential for peroxisome formation through several mechanisms:

Import of Peroxisomal Proteins

| Pathway | Receptor | Cargo | PEX3 Role |
|---------|----------|-------|------------|
| PTS1 | PEX5 | Matrix proteins with SKL motif | Docking site |
| PTS2 | PEX7/PEX5/PEX18 | Matrix proteins with N-terminus | Indirect role |
| PMP import | PEX19 | Membrane proteins | Direct docking |

Peroxisome Dynamics

• Proliferation: PEX3 responds to cellular signals for new peroxisome formation
• Division: Coordinates with [DRP1](/proteins/drp1-protein) for peroxisome fission
• [Autophagy](/entities/autophagy): PEX3 regulates pexophagy (peroxisome-specific autophagy)

Brain Expression and Function

Cellular Distribution

| Cell Type | Expression | Notes |
|-----------|------------|-------|
| Neurons | Moderate | Higher in metabolically active regions |
| [Astrocytes](/entities/astrocytes) | High | Peroxisomes abundant for lipid metabolism |
| [Microglia](/cell-types/microglia-neuroinflammation) | Moderate | [ROS](/entities/reactive-oxygen-species) handling, inflammation |
| Oligodendrocytes | High | Myelin lipid synthesis |

Regional Expression

PEX3 is expressed throughout the brain with notable levels in:

• Cerebral [cortex](/brain-regions/cortex) (pyramidal neurons)
• [Hippocampus](/brain-regions/hippocampus) (CA1-CA3, dentate gyrus)
• Cerebellum (Purkinje cells)
• Substantia nigra (dopaminergic neurons)

Functions in Neural Cells

Disease Associations

Zellweger Spectrum Disorders

PEX3 deficiency causes the most severe form of Zellweger syndrome[@steinberg2015]:

Clinical Features:

• Severe developmental delay

• Hepatomegaly and liver dysfunction
• Severe neurological impairment
• Absence of peroxisomes

• Null mutations: Severe phenotype
• Missense mutations: Variable presentation

Alzheimer's Disease

Association: Peroxisomal dysfunction in AD[@kou2021]

Mechanisms:

• Reduced PEX3 expression in AD brain
• Peroxisome numbers decreased in neurons
• Impaired VLCFA metabolism
• Accumulation of very-long-chain fatty acids
• Reduced plasmalogens (myelin lipids)

• Post-mortem studies show decreased peroxisomes in AD brain
• PEX3 expression inversely correlates with amyloid burden
• Plasmalogen levels reduced in AD patients

Parkinson's Disease

Association: Peroxisomal dysfunction in PD[@cook2020]

Mechanisms:

• [α-Synuclein](/proteins/alpha-synuclein) may impair peroxisome function
• PEX3 expression altered in substantia nigra
• Mitochondrial-peroxisomal cross-talk
• Lipid metabolism abnormalities

• Peroxisome function reduced in PD models
• PEX3 knockout mice show dopaminergic vulnerability

Other Associations

• Zellweger-like disorders: Variant forms
• Autism spectrum: Some patients with PEX3 variants
• Hearing loss: Associated with peroxisomal dysfunction

Therapeutic Implications

Peroxisome-Targeted Therapies

| Strategy | Approach | Status |
|----------|----------|--------|
| Gene therapy | AAV-PEX3 delivery | Preclinical |
| Small molecules | PEX3 expression modulators | Research |
| Plasmalogen supplementation | Restore membrane lipids | Clinical trials |
| Antioxidants | Reduce oxidative stress | Investigational |

Challenges

• [Blood-brain barrier](/entities/blood-brain-barrier) penetration
• Delivery to specific neuronal populations
• Balancing peroxisome biogenesis with potential risks

Animal Models

Knockout Mice

Pex3−/− mice:

• Embryonic lethal (required for development)
• Severe peroxisomal deficiency
• Model for Zellweger syndrome

Conditional Knockouts

Neuron-specific Pex3 knockout:

• Progressive neurodegeneration
• Behavioral deficits
• Accumulation of VLCFAs

Transgenic Models

• PEX3 overexpression: Protected against oxidative stress
• Human PEX3 mutants: Model peroxisome biogenesis disorders

Genetic Variants

Pathogenic Mutations

| Mutation Type | Examples | Effect |
|---------------|----------|--------|
| Null | Frameshift, nonsense | Severe phenotype |
| Missense | R67Q, G170R | Variable severity |
| Splice site | IVS5+1G>A | Aberrant splicing |

Polymorphisms

• Various SNPs with unknown functional significance
• Population-specific variants

Interactions and Pathways

Protein Interactions

• PEX19: Chaperone for PMP import
• PEX5: PTS1 receptor
• PEX7: PTS2 receptor
• PEX11: Peroxisome proliferation
• PEX10: Import complex component

Signaling Pathways

• PPARα signaling: Peroxisome proliferation
• Mitochondrial dynamics: Cross-talk with mitochondria
• Autophagy: Pexophagy regulation

Research Directions

Unanswered Questions

Background

The study of Pex3 Gene Peroxisome Biogenesis Factor 3 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

See Also

• [Peroxisome](/genes/pex1)
• [Peroxisome Biogenesis Disorders](/content/genes)
• [PEX2](/genes/pex2)
• [PEX19](/genes/pex19)
• [PEX1](/genes/pex19)
• [PEX5](/genes/pex5)
• [VLCFA Metabolism](/proteins/met)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)

External Links

• [NCBI Gene: PEX3](https://www.ncbi.nlm.nih.gov/gene/5679)
• [UniProt: PEX3](https://www.uniprot.org/uniprot/Q9Y5Y8)
• [Ensembl: PEX3](https://www.ensembl.org/Homo_sapiens/ENSG00000034693)
• [OMIM: PEX3](https://omim.org/entry/614789)

References

Pathway Diagram

The following diagram shows the key molecular relationships involving PEX3 Gene - Peroxisome Biogenesis Factor 3 discovered through SciDEX knowledge graph analysis: