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| Protein Name | Microtubule-Associated Protein 4 |
| Gene | [MAP4](/genes/map4) |
| UniProt | P27816 |
| Molecular Weight | ~210 kDa |
| Subcellular Localization | Cytoskeleton, Axons, Dendrites |
| Protein Family | MAP family |
| Aliases | MtAP4, MAP4, neuronal Prof |
MAP4 (Microtubule-Associated Protein 4), encoded by the MAP4 gene, is a prominent microtubule-associated protein that plays critical roles in neuronal function, cell division, and intracellular transport. As a member of the MAP family, MAP4 shares structural and functional similarities with tau protein, which is heavily implicated in Alzheimer's disease pathogenesis. This connection makes MAP4 a protein of significant interest in neurodegenerative disease research [1].
MAP4 is a large protein (~210 kDa) with a modular domain structure:
¶ N-terminal Projection Domain
- Projects outward from the microtubule surface
- Contains multiple phosphorylation sites
- Interacts with other cytoskeletal proteins
- Regulates microtubule bundling and organization
¶ C-terminal Microtubule-binding Domain
- Contains three to four tau-like repeat motifs (PXXP)
- Binds to tubulin heterodimers
- Mediates microtubule stabilization
- Contains the microtubule polymerization promoting protein (MIPP) region
- Multiple serine/threonine phosphorylation sites
- Phosphorylation regulates microtubule binding affinity
- Key sites: Ser696, Ser787, Ser1133 (human MAP4)
The structural similarity to tau protein (~50% homology in microtubule-binding domain) has important implications for understanding tauopathies.
MAP4 is a major stabilizer of microtubules in non-neuronal cells and neurons:
- Prevents depolymerization: Binds along microtubule length, stabilizing protofilaments
- Promotes polymerization: Facilitates tubulin assembly into microtubules
- Regulates dynamics: Modifies microtubule instability
By stabilizing microtubules, MAP4 indirectly supports:
- Axonal transport: Facilitates vesicle and organelle movement along axons
- Dendritic transport: Supports synaptic vesicle trafficking
- Cytoplasmic transport: Enables long-distance transport in neurons
In dividing cells, MAP4:
- Stabilizes mitotic spindles
- Regulates chromosome segregation
- Controls cell cycle progression
MAP4 plays roles in:
- Axon guidance
- Dendrite formation
- Synapse development
MAP4 is closely connected to tau pathology in AD:
Hyperphosphorylation: Like tau, MAP4 becomes hyperphosphorylated in AD brains:
- GSK-3β phosphorylates MAP4 at multiple sites
- CDK5 also contributes to MAP4 phosphorylation
- Phosphorylation reduces microtubule binding
Tau-like Pathology: MAP4 exhibits tau-like behavior:
- Forms aggregates in AD brains
- Colocalizes with neurofibrillary tangles
- May contribute to tangle formation
Axonal Transport Defects: MAP4 dysfunction contributes to:
- Impaired axonal transport
- Synaptic loss
- Neuronal dysfunction
In Parkinson's disease, MAP4 involvement includes:
- α-Synuclein interaction: Possible cross-talk with alpha-synuclein pathology
- Microtubule disruption: Lewy bodies may disrupt microtubule function
- Axonal degeneration: Similar mechanisms to AD
- Tauopathies: MAP4 is affected in all tauopathies
- Amyotrophic lateral sclerosis (ALS): Microtubule dysfunction
- Huntington's disease: Axonal transport impairment
Targeting kinases that phosphorylate MAP4:
- GSK-3β inhibitors: Lithium, tideglusib
- CDK5 inhibitors: Roscovitine derivatives
Drugs that stabilize microtubules bypass MAP4 dysfunction:
- Taxanes: Paclitaxel, docetaxel (limited CNS penetration)
- Epothilones: Better CNS penetration
- Protein phosphatase activators
- Kinase inhibitors
Key findings from recent research:
- MAP4 phosphorylation is an early event in AD progression
- Genetic variants of MAP4 may modify AD risk
- MAP4 aggregates are found in aging brains