MAP7 Protein

MAP7 Protein

Overview

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">MAP7 Protein</th>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>Microtubule-Associated Protein 7 (Ensconsin)</td>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>[MAP7](/genes/map7)</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>[Q3KQU3](https://www.uniprot.org/uniprot/Q3KQU3)</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~84 kDa</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Cytoplasm, cytoskeleton</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>MAP7/ensconsin family</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

MAP7 Protein

Overview

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">MAP7 Protein</th>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>Microtubule-Associated Protein 7 (Ensconsin)</td>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>[MAP7](/genes/map7)</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>[Q3KQU3](https://www.uniprot.org/uniprot/Q3KQU3)</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~84 kDa</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Cytoplasm, cytoskeleton</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>MAP7/ensconsin family</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

MAP7 (Microtubule-Associated Protein 7), also known as ensconsin or E-MAP-115, is a microtubule-binding protein encoded by the [MAP7](/genes/map7) gene that stabilizes microtubule networks and recruits kinesin-1 motors for intracellular transport.[@metzger2012][@hooikaas2019] Unlike [tau](/proteins/tau) and [MAP2](/proteins/map2-protein), which bind along the outer surface of microtubules, MAP7 occupies a distinct binding site and cooperates with kinesin-1 to facilitate axonal cargo transport.[@hooikaas2019] Disruption of MAP7 function has been linked to axonal transport deficits, and mutations in MAP7 family members have been associated with neurodevelopmental disorders and familial [amyotrophic lateral sclerosis](/diseases/amyotrophic-lateral-sclerosis).[@liao2019]

Structure

MAP7 contains two principal functional domains separated by a long central coiled-coil region:

• N-terminal microtubule-binding domain (aa 59–170): Binds directly to microtubule lattice at a site distinct from the [tau](/proteins/tau)/MAP2 binding groove, allowing MAP7 and tau to co-occupy the same microtubule.[@metzger2012][@hooikaas2019] The binding stabilizes microtubules against depolymerization and katanin-mediated severing.
• Central coiled-coil domain: Mediates dimerization and may provide structural rigidity for bridging the microtubule lattice to associated motor proteins.[@metzger2012]
• C-terminal kinesin-1 binding domain (aa 597–749): Directly interacts with the stalk region of kinesin-1 heavy chain (KIF5B), recruiting and activating kinesin-1 motors on the microtubule surface.[@hooikaas2019] This interaction is essential for kinesin-1-dependent axonal transport of mitochondria, synaptic vesicles, and signaling endosomes.

Normal Function

Kinesin-1 Recruitment and Axonal Transport

MAP7's most distinctive function is its role as a kinesin-1 co-activator on microtubules.[@hooikaas2019] In [neurons](/entities/neurons), kinesin-1 drives anterograde axonal transport of mitochondria, synaptic vesicle precursors, [APP](/entities/app-protein)-containing vesicles, and neurofilaments. MAP7 enhances kinesin-1 landing rate on microtubules and increases its processive run length, effectively boosting transport efficiency.[@hooikaas2019][@monroy2018] Single-molecule studies show that MAP7 binding to microtubules creates preferred "landing pads" for kinesin-1, while simultaneously inhibiting kinesin-3 motility — establishing a MAP-based code that partitions different motor proteins to different microtubule tracks.[@monroy2018]

Microtubule Stabilization

MAP7 stabilizes microtubules and promotes acetylation and detyrosination, post-translational modifications associated with long-lived, stable microtubules in the axon shaft.[@metzger2012] This stabilization function is complementary to tau, as MAP7 binds a non-overlapping site and the two proteins cooperatively enhance microtubule resistance to cold-induced depolymerization.

Neuronal Morphogenesis

During development, MAP7 expression increases as neurons mature and is enriched in axons over dendrites.[@metzger2012] MAP7 regulates axon branch formation and growth cone advance, and its depletion in cultured cortical neurons reduces axon length and branching complexity.

Role in Neurodegeneration

Axonal Transport Failure

Axonal transport deficits are an early and universal feature of neurodegenerative diseases including [Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), [ALS](/diseases/amyotrophic-lateral-sclerosis), and [Huntington's Disease](/diseases/huntington-disease).[@hares2018] Because MAP7 is the primary recruiter of kinesin-1 to microtubules, loss or dysfunction of MAP7 directly impairs the anterograde transport of mitochondria and synaptic components that is essential for maintaining long axons.[@hooikaas2019][@monroy2018]

Competition with Tau

In tauopathies, [hyperphosphorylated tau](/mechanisms/tau-hyperphosphorylation) detaches from microtubules and accumulates in the cytoplasm, but paradoxically, unphosphorylated tau at high concentrations can also impair axonal transport by blocking kinesin-1 motility.[@monroy2018] MAP7 counteracts this tau-mediated inhibition of kinesin-1 by occupying a separate binding site and directly recruiting the motor. The balance between MAP7 and tau on microtubule surfaces may determine whether transport proceeds normally or fails — a concept termed the "MAP code" for motor regulation.[@monroy2018]

ALS and Motor Neuron Disease

Mutations in MAP7 domain-containing protein 1 (MAP7D1) have been identified in familial ALS pedigrees, and MAP7 itself shows altered expression in motor neurons of SOD1 mutant mouse models.[@liao2019] Motor neurons, with axons up to 1 meter long, are exquisitely dependent on efficient kinesin-1-mediated transport, making them especially vulnerable to MAP7 family dysfunction.

Charcot-Marie-Tooth Disease

Peripheral neuropathies including CMT type 2 involve defective axonal transport in long peripheral nerves. MAP7 expression is critical in peripheral sensory and motor neurons, and its reduction correlates with axonal degeneration in animal models of CMT.[@liao2019]

Therapeutic Implications

• Transport enhancement: Strategies to increase MAP7 expression or activity could restore kinesin-1 recruitment and rescue axonal transport deficits in tauopathies and motor neuron diseases.[@hooikaas2019]
• MAP code modulation: Understanding how the MAP7-tau balance regulates motor protein access to microtubules could inform approaches that selectively enhance beneficial transport without globally destabilizing microtubules.[@monroy2018]
• Biomarker potential: MAP7 expression levels in cerebrospinal fluid or peripheral nerve biopsies could potentially serve as an axonal transport health biomarker in ALS or CMT progression monitoring.

See Also

• [Tau Protein](/proteins/tau)
• [Kinesin-1](/proteins/kinesin-1)
• [Axonal Transport](/mechanisms/axonal-transport)
• [Microtubule Dynamics](/mechanisms/microtubule-dynamics)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)

External Links

• [UniProt: MAP7 (Q3KQU3)](https://www.uniprot.org/uniprot/Q3KQU3)
• [NCBI Gene: MAP7](https://www.ncbi.nlm.nih.gov/gene/9053)
• [GeneCards: MAP7](https://www.genecards.org/cgi-bin/carddisp.pl?gene=MAP7)

References