Mitofusin-2 Protein

Mitofusin-2 Protein

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2">Mitofusin-2 (MFN2)</th></tr>
<tr><td>Gene</td><td>[MFN2](/genes/mfn2)</td></tr>
<tr><td>UniProt ID</td><td>[O95140](https://www.uniprot.org/uniprot/O95140)</td></tr>
<tr><td>PDB</td><td>6JFL, 5YEM, 5GOM</td></tr>
<tr><td>Molecular Weight</td><td>99.3 kDa</td></tr>
<tr><td>Localization</td><td>Mitochondrial outer membrane</td></tr>
<tr><td>Family</td><td>Dynamin superfamily, mitofusin family</td></tr>
<tr><td>Disease</td><td>CMT2A, PD, AD, ALS</td></tr>
</table>
</div>

Overview

Mitofusin-2 (MFN2) is a dynamin-related GTPase embedded in the mitochondrial outer membrane that mediates mitochondrial fusion, endoplasmic reticulum-mitochondria tethering, and mitophagy. Mutations in MFN2 cause Charcot-Marie-Tooth disease type 2A (CMT2A), the most common axonal form of hereditary neuropathy. MFN2 dysfunction is increasingly implicated in Parkinson's disease, Alzheimer's disease, and ALS.

Structure

MFN2 has a characteristic domain organization:

• N-terminal GTPase domain: Hydrolyzes GTP to power membrane fusion
• HR1 (heptad repeat 1): Mediates dimerization
• Two transmembrane domains: Anchor protein in outer membrane (both N- and C-termini cytosolic)
• HR2 (heptad repeat 2): Forms antiparallel coiled-coils for tethering
• Coiled-coil regions: Mediate protein-protein interactions

MFN2 functions through both:

• Homotypic interactions: MFN2-MFN2 complexes
• Heterotypic interactions: MFN2-MFN1 complexes for fusion

Normal Function

...

Mitofusin-2 Protein

<div class="infobox infobox-protein">
<table>
<tr><th colspan="2">Mitofusin-2 (MFN2)</th></tr>
<tr><td>Gene</td><td>[MFN2](/genes/mfn2)</td></tr>
<tr><td>UniProt ID</td><td>[O95140](https://www.uniprot.org/uniprot/O95140)</td></tr>
<tr><td>PDB</td><td>6JFL, 5YEM, 5GOM</td></tr>
<tr><td>Molecular Weight</td><td>99.3 kDa</td></tr>
<tr><td>Localization</td><td>Mitochondrial outer membrane</td></tr>
<tr><td>Family</td><td>Dynamin superfamily, mitofusin family</td></tr>
<tr><td>Disease</td><td>CMT2A, PD, AD, ALS</td></tr>
</table>
</div>

Overview

Mitofusin-2 (MFN2) is a dynamin-related GTPase embedded in the mitochondrial outer membrane that mediates mitochondrial fusion, endoplasmic reticulum-mitochondria tethering, and mitophagy. Mutations in MFN2 cause Charcot-Marie-Tooth disease type 2A (CMT2A), the most common axonal form of hereditary neuropathy. MFN2 dysfunction is increasingly implicated in Parkinson's disease, Alzheimer's disease, and ALS.

Structure

MFN2 has a characteristic domain organization:

• N-terminal GTPase domain: Hydrolyzes GTP to power membrane fusion
• HR1 (heptad repeat 1): Mediates dimerization
• Two transmembrane domains: Anchor protein in outer membrane (both N- and C-termini cytosolic)
• HR2 (heptad repeat 2): Forms antiparallel coiled-coils for tethering
• Coiled-coil regions: Mediate protein-protein interactions

MFN2 functions through both:

• Homotypic interactions: MFN2-MFN2 complexes
• Heterotypic interactions: MFN2-MFN1 complexes for fusion

Normal Function

MFN2 has diverse mitochondrial functions:

Outer Membrane Fusion: Tethers and fuses adjacent mitochondria via GTP hydrolysis[@koshiba2004]

ER-Mitochondria Contacts (MAMs): Tethers mitochondria to ER, regulating calcium signaling and lipid transfer[@brito2008]

Mitophagy: Acts as receptor for Parkin-mediated mitophagy

Axonal Transport: Links mitochondria to microtubule motors

Metabolism: Influences glucose homeostasis and insulin sensitivity

The ER-mitochondria tethering function is particularly important for:

• Calcium homeostasis
• Phospholipid biosynthesis
• [Apoptosis](/entities/apoptosis) regulation
• Autophagosome formation

Role in Neurodegeneration

Charcot-Marie-Tooth Disease Type 2A (CMT2A)

MFN2 mutations cause the most common axonal hereditary neuropathy:

Common pathogenic variants:

• R94Q: Impaired GTPase activity
• T105M: Altered mitochondrial distribution
• R364W: Disrupted fusion activity

Disease mechanisms:

Impaired fusion: Fragmented mitochondrial network

ER-mitochondria uncoupling: Disrupted calcium homeostasis

Axonal transport defects: Impaired mitochondrial trafficking to synapses[@baloh2007]

Mitophagy failure: Accumulation of damaged mitochondria

Parkinson's Disease

MFN2 contributes to PD through:

• PINK1/Parkin pathway: MFN2 is ubiquitinated by Parkin to promote mitophagy
• [α-synuclein](/proteins/alpha-synuclein) interaction: Oligomeric α-synuclein disrupts MFN2-mediated fusion
• Mitochondrial quality control: Loss of MFN2 impairs mitophagy of damaged mitochondria[@chen2013]

Reduced MFN2 expression observed in PD substantia nigra.

Alzheimer's Disease

MFN2 dysfunction in AD:

• Amyloid-β toxicity: [Aβ](/proteins/amyloid-beta) oligomers reduce MFN2 expression
• MAM disruption: Altered ER-mitochondria contacts
• Mitochondrial fragmentation: Contributing to synaptic loss

ALS

MFN2 involvement in motor neuron disease:

• Axonal transport: Critical for long motor axons
• Mitochondrial distribution: Defects lead to distal axon degeneration
• CHCHD10 interaction: Shared pathway with ALS-linked protein

Therapeutic Targeting

| Strategy | Mechanism | Status |
|----------|-----------|--------|
| Leflunomide | Enhances MFN2 expression | Phase II (CMT) |
| M1 agonist peptide | Promotes fusion | Preclinical |
| Gene therapy | AAV-MFN2 delivery | Preclinical |
| Mitochondrial antioxidants | Reduce oxidative damage | Clinical |
| HDAC6 inhibitors | Enhance mitochondrial transport | Clinical trials |

Leflunomide has shown promise in restoring mitochondrial fusion in CMT2A models[@rocha2020].

See Also

• OPA1 - Inner membrane fusion partner
• DRP1 - Mitochondrial fission protein
• Parkin - Mitophagy E3 ligase
• PINK1 - Mitophagy regulator
• [Charcot-Marie-Tooth Disease](/diseases/charcot-marie-tooth-disease)
• [Mitochondrial Dysfunction](/mechanisms/mitochondrial-dysfunction)

References

[Koshiba et al, Mitofusins are required for mitochondrial fusion and cell viability (2004)](https://doi.org/10.1126/science.1079368)

[Unknown, de Brito and Scorrano. Mitofusin-2 tethers ER to mitochondria. . 2008;456(7222):605-610 (2008)](https://doi.org/10.1038/nature07797)

[Baloh et al. Mitofusin2 is required for axonal transport of mitochondria, J Neurosci (2007)](https://doi.org/10.1523/JNEUROSCI.1361-07.2007)

[Unknown, Chen and Dorn. PINK1-phosphorylated mitofusin 2 is a Parkin receptor. . 2013;340(6131):471-475 (2013)](https://doi.org/10.1126/science.1241430)

[Rocha et al. Leflunomide promotes mitochondrial fusion in CMT2A models, J Clin Invest (2020)](https://doi.org/10.1172/JCI131617)