MARCH5 Protein

MARCH5 Protein

Overview

MARCH5 protein (Membrane Associated Ring-CH-Type Finger 5, also known as MITOL) is a mitochondrial outer membrane E3 ubiquitin ligase encoded by the [MARCH5/MARCHF5](/genes/march5) gene. MARCH5 is a RING-CH type ubiquitin ligase that spans the outer mitochondrial membrane four times and ubiquitinates misfolded proteins, mitochondrial dynamics regulators ([DRP1](/proteins/drp1-protein), [MFN1/2](/proteins/mfn2-protein)), and innate immune signaling components. MARCH5 is a critical component of mitochondrial protein quality control, and its dysfunction leads to mitochondrial fragmentation and neuronal vulnerability in [Parkinson's disease](/diseases/parkinsons-disease) and [ALS](/diseases/amyotrophic-lateral-sclerosis).

MARCH5 Protein

Overview

MARCH5 protein (Membrane Associated Ring-CH-Type Finger 5, also known as MITOL) is a mitochondrial outer membrane E3 ubiquitin ligase encoded by the [MARCH5/MARCHF5](/genes/march5) gene. MARCH5 is a RING-CH type ubiquitin ligase that spans the outer mitochondrial membrane four times and ubiquitinates misfolded proteins, mitochondrial dynamics regulators ([DRP1](/proteins/drp1-protein), [MFN1/2](/proteins/mfn2-protein)), and innate immune signaling components. MARCH5 is a critical component of mitochondrial protein quality control, and its dysfunction leads to mitochondrial fragmentation and neuronal vulnerability in [Parkinson's disease](/diseases/parkinsons-disease) and [ALS](/diseases/amyotrophic-lateral-sclerosis).

<div class="infobox infobox-protein"> [@karbowski2007]
<div class="infobox-header">MARCH5 Protein</div> [@yoo2015]
<table> [@sugiura2013]
<tr><td class="infobox-label">Protein Name</td><td>E3 ubiquitin-protein ligase MARCH5</td></tr> [@nagashima2014]
<tr><td class="infobox-label">Gene</td><td>[MARCH5 (MARCHF5)](/genes/march5)</td></tr>
<tr><td class="infobox-label">UniProt ID</td><td>[Q9NX47](https://www.uniprot.org/uniprot/Q9NX47)</td></tr>
<tr><td class="infobox-label">Molecular Weight</td><td>35.3 kDa</td></tr>
<tr><td class="infobox-label">Subcellular Localization</td><td>Outer mitochondrial membrane</td></tr>
<tr><td class="infobox-label">Protein Family</td><td>MARCH family E3 ubiquitin ligases</td></tr>
<tr><td class="infobox-label">Associated Diseases</td><td>[PD](/diseases/parkinsons-disease), [AD](/diseases/alzheimers-disease), [ALS](/diseases/amyotrophic-lateral-sclerosis), [HD](/diseases/huntingtons-disease)</td></tr>
</table>
</div>

Structure

Domain Architecture

• N-terminal cytoplasmic region (residues 1-30): Short cytoplasmic tail
• Transmembrane domain 1 (TM1, residues 31-50): First membrane-spanning helix
• RING-CH domain (residues 51-100): The catalytic E3 ubiquitin ligase domain facing the cytoplasm; contains the Zn2+-coordinating His-Cys motif characteristic of MARCH family proteins; transfers ubiquitin from E2 conjugating enzymes to substrate lysine residues
• TM2-TM4 (residues 101-230): Three additional transmembrane helices that form the substrate recognition interface
• C-terminal cytoplasmic tail (residues 231-278): Substrate interaction and regulatory region

RING-CH Domain

• E2 partners: UBE2D (UbcH5) family, UBE2E1, UBE2J1
• Catalytic mechanism: RING domain positions the E2~Ub thioester for direct transfer to substrate lysines
• Critical residues: His43 and Cys65 are essential for catalytic activity; H43W mutation abolishes ubiquitin ligase function

Membrane Topology

Normal Function

Mitochondrial Protein Quality Control

• Recognizes and ubiquitinates misfolded or damaged proteins exposed on the OMM
• Partners with the AAA-ATPase [VCP/p97](/genes/vcp) for substrate extraction and proteasomal delivery
• Clears mislocalized tail-anchored proteins that target mitochondria instead of the ER
• Essential component of mitochondria-associated degradation (MAD)

Mitochondrial Dynamics

• [DRP1](/proteins/drp1-protein): K48-linked ubiquitination regulates DRP1 activity and turnover at fission sites
• MFN1/MFN2: Ubiquitination modulates fusogenic activity
• MiD49/MiD51: MARCH5 ubiquitinates mitochondrial fission receptors
• Loss of MARCH5 → excessive DRP1 accumulation → mitochondrial fragmentation

Innate Immune Signaling Control

• K48-linked ubiquitination of MAVS terminates RIG-I/MDA5-dependent IFN-β production
• MARCH5 prevents chronic interferon signaling from damage-associated mtDNA
• Relevant for neuroinflammation: MARCH5 deficiency prolongs sterile IFN responses

Disease Substrate Clearance

• Mutant [SOD1](/proteins/sod1-protein) (ALS) — clears misfolded SOD1 from OMM
• PolyQ [huntingtin](/proteins/huntingtin-protein) fragments (HD) — ubiquitinates mitochondria-associated aggregates
• [α-Synuclein](/proteins/alpha-synuclein) (PD) — clears mitochondria-imported α-syn fragments
• [Amyloid-beta](/proteins/amyloid-beta) (AD) — assists clearance of Aβ-associated mitochondrial damage

Role in Disease

Parkinson's Disease

• MARCH5 cooperates with [PINK1](/proteins/pink1-protein)/[Parkin](/proteins/parkin-protein) for mitophagy initiation
• Initial OMM ubiquitination by MARCH5 primes the Parkin-dependent ubiquitin amplification cascade
• α-Synuclein accumulation suppresses MARCH5, creating mitochondrial dysfunction feed-forward
• MARCH5 also ubiquitinates LRRK2-G2019S on mitochondria, promoting its clearance

ALS

• Mutant SOD1 misfolding on the OMM overwhelms MARCH5 capacity
• [TDP-43](/mechanisms/tdp-43-proteinopathy) C-terminal fragments accumulate on mitochondria as MARCH5 substrates
• MARCH5 overexpression delays motor neuron death in SOD1-G93A cultures

Alzheimer's Disease

• MARCH5 expression reduced in AD hippocampal [neurons](/entities/neurons)
• MARCH5 deficiency exacerbates Aβ-induced mitochondrial fragmentation

Therapeutic Targeting

• MARCH5 gene therapy: AAV-MARCH5 overexpression enhances mitochondrial quality control
• USP30 inhibitors: Block the deubiquitinase that opposes MARCH5/Parkin; enhance mitochondrial clearance
• Combination approaches: MARCH5 + PINK1/Parkin activation for synergistic mitochondrial protection

See Also

• [MARCH5 Gene](/genes/march5)
• [PINK1](/genes/pink1) / [Parkin](/genes/prkn) — mitophagy pathway
• [Mitochondrial Dysfunction](/mechanisms/mitochondrial-dysfunction)
• [DRP1](/genes/dnm1l) — mitochondrial fission GTPase
• [USP30](/genes/usp30) — opposing deubiquitinase

External Links

• [UniProt: Q9NX47](https://www.uniprot.org/uniprot/Q9NX47)
• [GeneCards: MARCHF5](https://www.genecards.org/cgi-bin/carddisp.pl?gene=MARCHF5)

References