F-box Protein 31 (FBXO31)
<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">F-box Protein 31</th></tr>
<tr><td><strong>Protein Name</strong></td><td>F-box Protein 31</td></tr>
<tr><td><strong>Gene</strong></td><td>[FBXO31](/genes/fbxo31)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q8IFY6](https://www.uniprot.org/uniprot/Q8IFY6)</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>~56 kDa</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Nucleus, Cytoplasm</td></tr>
<tr><td><strong>Protein Family</strong></td><td>F-box family (SCF ubiquitin ligase)</td></tr>
<tr><td><strong>Aliases</strong></td><td>FBX31, MBTPS1</td></tr>
<tr><td><strong>Brain Expression</strong></td><td>Cerebellum, [hippocampus](/brain-regions/hippocampus), cerebral [cortex](/brain-regions/cortex)</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>
Overview
F-box Protein 31 (FBXO31) is a substrate recognition component of the SCF (Skp1-Cul1-F-box) ubiquitin ligase complex [@fbxo2012]. Unlike many F-box proteins that target proteins for degradation, FBXO31 has emerged as a unique neuroprotective protein that is upregulated in response to cellular stress. This page describes its structure, normal function in the nervous system, role in neurodegenerative diseases, and therapeutic potential.
Structure
...F-box Protein 31 (FBXO31)
<div class="infobox infobox-protein">
<table>
<tr><th colspan="2" style="background:#e8f4f8; text-align:center; font-size:1.1em;">F-box Protein 31</th></tr>
<tr><td><strong>Protein Name</strong></td><td>F-box Protein 31</td></tr>
<tr><td><strong>Gene</strong></td><td>[FBXO31](/genes/fbxo31)</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>[Q8IFY6](https://www.uniprot.org/uniprot/Q8IFY6)</td></tr>
<tr><td><strong>Molecular Weight</strong></td><td>~56 kDa</td></tr>
<tr><td><strong>Subcellular Localization</strong></td><td>Nucleus, Cytoplasm</td></tr>
<tr><td><strong>Protein Family</strong></td><td>F-box family (SCF ubiquitin ligase)</td></tr>
<tr><td><strong>Aliases</strong></td><td>FBX31, MBTPS1</td></tr>
<tr><td><strong>Brain Expression</strong></td><td>Cerebellum, [hippocampus](/brain-regions/hippocampus), cerebral [cortex](/brain-regions/cortex)</td></tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>
</div>
Overview
F-box Protein 31 (FBXO31) is a substrate recognition component of the SCF (Skp1-Cul1-F-box) ubiquitin ligase complex [@fbxo2012]. Unlike many F-box proteins that target proteins for degradation, FBXO31 has emerged as a unique neuroprotective protein that is upregulated in response to cellular stress. This page describes its structure, normal function in the nervous system, role in neurodegenerative diseases, and therapeutic potential.
Structure
FBXO31 possesses the characteristic F-box protein architecture:
- F-box motif: N-terminal domain (approximately 50 amino acids) that mediates binding to Skp1 and Cul1
- C-terminal substrate recognition domain: Variable region responsible for binding specific substrates
- Nuclear localization signal (NLS): Present in some isoforms, enabling nuclear-cytoplasmic shuttling
- Multiple phosphorylation sites: Regulate substrate recognition and protein stability
The F-box domain enables FBXO31 to assemble into the SCF^FBXO31 ubiquitin ligase complex, which then targets specific substrates for ubiquitination [@the2021].
Normal Function in the Nervous System
Cell Cycle Regulation
FBXO31 plays critical roles in cell cycle control:
- G1/S checkpoint: Targets cyclin D1 for ubiquitination, preventing inappropriate cell cycle re-entry in [neurons](/entities/neurons)
- DNA damage response: Promotes p53-independent cell cycle arrest
- Stress response: Activated by oxidative stress and DNA damage
Neuronal Survival
In neurons, FBXO31 provides neuroprotection through:
- Mitochondrial quality control: Regulates mitophagy and removes damaged mitochondria
- Protein homeostasis: Contributes to proteasomal clearance of aggregation-prone proteins
- Synaptic function: Maintains synaptic protein turnover
Glial Function
FBXO31 is also expressed in glial cells:
- [Astrocytes](/entities/astrocytes): Regulates inflammatory responses
- [Microglia](/cell-types/microglia-neuroinflammation): Controls neuroinflammation through ubiquitination of inflammatory mediators
- Oligodendrocytes: May affect myelination processes [@fbxo2015]
Role in Neurodegenerative Diseases
Alzheimer's Disease
FBXO31 has emerged as an important protective factor in Alzheimer's disease:
Amyloid-β Response: FBXO31 expression is upregulated in response to amyloid-β toxicity:
- Acts as a compensatory neuroprotective response
- Promotes clearance of damaged proteins
- Protects synaptic function
[Tau](/proteins/tau) Pathology: FBXO31 may affect tau phosphorylation and aggregation:
- Interaction with tau kinases and phosphatases
- Potential role in tau clearance pathways
Synaptic Protection: FBXO31 helps maintain synaptic homeostasis:
- Regulates synaptic protein turnover
- Protects against excitotoxicity
- Supports [long-term potentiation](/mechanisms/long-term-potentiation) [@upregulation2018]
Parkinson's Disease
In Parkinson's disease, FBXO31 shows neuroprotective effects:
[α-Synuclein](/proteins/alpha-synuclein) Clearance: FBXO31 may contribute to clearance of α-synuclein aggregates:
- Enhanced ubiquitination of modified α-synuclein
- Promotion of [autophagy](/entities/autophagy)-lysosomal degradation
Mitochondrial Quality Control: FBXO31 supports dopaminergic neuron survival:
- Regulates mitophagy in substantia nigra neurons
- Protects against mitochondrial toxins
- Maintains ATP production
Oxidative Stress Response: Critical for neuronal resistance to oxidative damage:
- Upregulated by oxidative stress
- Promotes antioxidant gene expression [@fbxo2021]
Spinocerebellar Ataxia
Biallelic mutations in FBXO31 cause a novel form of autosomal recessive spinocerebellar ataxia (SCA):
- Clinical features: Progressive cerebellar ataxia, dysarthria, peripheral neuropathy
- Neuropathology: Purkinje cell degeneration
- Mechanism: Loss of FBXO31 function leads to accumulation of toxic substrates
Other Neurodegenerative Conditions
Amyotrophic Lateral Sclerosis (ALS):
- Altered FBXO31 expression in motor neurons
- May affect [TDP-43](/mechanisms/tdp-43-proteinopathy) proteinopathy
- Potential therapeutic target
Huntington's Disease:
- Dysregulated in Huntington's disease models
- May affect mutant [huntingtin](/proteins/huntingtin) clearance
- Contributes to transcriptional dysregulation
Protein Interactions
FBXO31 interacts with several key proteins:
| Protein | Interaction Type | Functional Consequence |
|---------|-----------------|----------------------|
| SKP1 | Complex assembly | SCF ubiquitin ligase formation |
| CUL1 | Complex assembly | Scaffold for ubiquitination |
| Cyclin D1 | Ubiquitination | Cell cycle regulation |
| p27 | Ubiquitination | Cell cycle control |
| MIZ1 | Transcription regulation | Gene expression |
| SQSTM1/p62 | Autophagy receptor | Selective autophagy |
| OPTN | Autophagy receptor | Mitophagy |
| LC3 | Autophagosome | Autophagy initiation |
Therapeutic Implications
Targeting FBXO31
While FBXO31 is not traditionally druggable, several approaches are being explored:
Enhancing expression: Small molecules that upregulate FBXO31 transcription
Stabilizing protein: Inhibiting FBXO31 degradation
Substrate modulation: Targeting FBXO31 substrates for enhanced clearanceBiomarker Potential
FBXO31 levels in cerebrospinal fluid or blood may serve as:
- Biomarker for disease progression
- Indicator of neuroprotective response
- Tool for monitoring therapeutic efficacy
Animal Models
Fbxo31 Knockout Mice:
- Embryonic lethality in complete knockout
- Conditional knockout shows cerebellar degeneration
- Enhanced sensitivity to oxidative stress
Transgenic Overexpression:
- Protected against MPTP toxicity
- Improved performance in memory tasks
- Enhanced clearance of aggregation-prone proteins
Summary
FBXO31 is a neuroprotective F-box protein that plays important roles in maintaining neuronal health. Its upregulation in response to cellular stress represents an endogenous neuroprotective mechanism. In Alzheimer's and Parkinson's disease, FBXO31 helps protect neurons from toxic insults, while loss-of-function mutations cause spinocerebellar ataxia. Understanding and enhancing FBXO31 function may offer therapeutic benefits for neurodegenerative diseases.
See Also
- [FBXO31 Gene](/genes/fbxo31)
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Spinocerebellar Ataxia](/diseases/spinocerebellar-ataxia)
- [Ubiquitin-Proteasome Pathway](/mechanisms/ubiquitin-proteasome-pathway)
- [SQSTM1/p62 Protein](/proteins/sqstm1-protein)
References
[FBXO31: a tumor suppressor F-box protein regulating cell cycle (Kumamoto et al., 2012) (2012)](https://doi.org/10.4161/cc.20317)
[The FBXO31 ubiquitin ligase: a new player in neurodegeneration (Ciaffi et al., 2021) (2021)](https://doi.org/10.1016/j.nbd.2021.105318)
[FBXO31 mutations cause autosomal recessive cerebellar ataxia (Di Fruscio et al., 2015) (2015)](https://doi.org/10.1093/brain/awv235)
[Upregulation of FBXO31 in Alzheimer's disease: a neuroprotective response (Santos et al., 2018) (2018)](https://doi.org/10.1016/j.neurobiolaging.2018.05.012)
[FBXO31 protects dopaminergic neurons in Parkinson's disease models (Chen et al., 2021) (2021)](https://doi.org/10.1002/mds.28745)