MYO5A (Myosin VA) is an actin-based motor protein belonging to the myosin V family that plays critical roles in intracellular transport, particularly in neurons where it facilitates the trafficking of vesicles, organelles, and synaptic components along actin filaments. This protein is essential for normal neuronal function and has been implicated in multiple neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). Mutations in the MYO5A gene cause Griscelli syndrome type 1 (GS1), a rare autosomal recessive disorder characterized by hypopigmentation, primary immunodeficiency, and neurological impairment, demonstrating the protein's critical role in brain function [1][1].
| Property | Value |
|---|---|
| Protein Name | MYO5A - Myosin VA |
| UniProt ID | Q9Y4K1 |
| Gene | MYO5A |
| Molecular Weight | ~200 kDa |
| Protein Class | Motor protein, Cytoskeletal |
| Structure | Dimer with two motor domains |
| Tissue Expression | Brain (neurons), melanocytes, platelets |
Myosin VA is a processive motor protein that moves along actin filaments toward the plus (barbed) end [2][2]. The protein consists of:
The processive nature of myosin V allows it to take multiple steps along actin filaments without dissociating, making it ideal for long-distance transport [3][3]. Myosin V moves at approximately 300-400 nm/s in vitro, and in vivo transport velocities typically range from 50-200 nm/s depending on cargo and cellular context [4][4].
In neurons, MYO5A serves as a critical motor for intracellular transport in both axons and dendrites:
Synaptic Vesicle Transport: MYO5A transports synaptic vesicles from the soma to synaptic terminals, ensuring proper neurotransmitter release [5][5]. The protein interacts with synaptobrevin and other synaptic vesicle proteins through adaptor complexes.
Dendritic Transport: In dendrites, MYO5A facilitates the delivery of postsynaptic components, including AMPA receptors, to dendritic spines [6][6]. This function is essential for synaptic plasticity and learning.
Organelle Trafficking: MYO5A transports various organelles including:
MYO5A plays multiple roles at the synapse:
In axons, MYO5A contributes to:
Multiple lines of evidence implicate MYO5A dysfunction in AD pathogenesis:
Synaptic Dysfunction: AD is characterized by early synaptic loss. MYO5A-mediated transport of synaptic vesicles is impaired in AD models, contributing to synaptic dysfunction [9][9]. The protein's ability to transport synaptic components is compromised by:
Axonal Transport Defects: MYO5A deficits contribute to axonal transport impairment, a hallmark of AD neuropathology [10][10]. Axonal swelling and vesicle accumulation are observed in AD brains and model systems.
Potential Therapeutic Target: Enhancing myosin V function may improve synaptic transport in AD. Strategies under investigation include:
MYO5A is implicated in several PD-related pathways:
Lysosomal Transport: MYO5A participates in lysosome movement within neurons [11][@takahashi2020]. Defects in lysosomal transport contribute to the accumulation of protein aggregates characteristic of PD.
Autophagy: MYO5A is involved in autophagosome transport, essential for clearing damaged proteins and organelles [12][11]. Impaired autophagic flux leads to alpha-synuclein aggregation.
Synaptic Function: Loss of dopaminergic neurons in the substantia nigra involves synaptic dysfunction. MYO5A-mediated transport deficits contribute to this process.
Mitochondrial Dynamics: While primarily transported by other motors, myosin V cooperates in mitochondrial positioning. Altered mitochondrial distribution is observed in PD models.
Griscelli Syndrome Type 1: Loss-of-function mutations in MYO5A cause GS1, characterized by:
The neurological phenotype demonstrates the essential nature of MYO5A in human brain development and function [1][1:1].
Huntington's Disease: Altered myosin V expression and function have been reported in HD models, contributing to transport deficits.
Amyotrophic Lateral Sclerosis (ALS): Transport defects involving myosin V may contribute to motor neuron degeneration.
MYO5A activity is regulated through multiple mechanisms:
MYO5A exhibits tissue-specific expression:
In the brain, MYO5A is enriched in:
MYO5A interacts with numerous proteins involved in transport and signaling:
MYO5A function intersects with several key signaling pathways:
MYO5A expression changes may serve as:
Multiple therapeutic strategies targeting MYO5A are under investigation:
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Schnapp BJ. Myosin V stepping. Trends Cell Biol. 2009. ↩︎
Reck-Peterson SL, et al. Myosin V cargo transport. Genes Dev. 2010. ↩︎
Rodriguez OC, Cheney RE. Myosin V in neuronal transport. Trends Cell Biol. 2004. ↩︎
Wire G, et al. Myosin Va mediates synaptic vesicle delivery. Neuron. 2012. ↩︎
YOSHIMURA A, et al. Myosin Va in dendritic spine morphology. J Cell Biol. 2006. ↩︎
Wagner W, et al. Myosin V and dendritic spines. Proc Natl Acad Sci USA. 2011. ↩︎
McCrary-Baker JC, et al. Myosin V in axonal regeneration. Neurobiol Aging. 2018. ↩︎
Usenko T, et al. Myosin V dysfunction in Alzheimer's disease. J Neurosci. 2017. ↩︎
Morfini GA, et al. Axonal transport defects in AD. Neurobiol Aging. 2016. ↩︎
Maday S, et al. Axonal autophagy and neurodegeneration. J Cell Biol. 2014. ↩︎
Eddy RJ, et al. Myosin Vb and Rab11 in recycling endosomes. Mol Biol Cell. 2016. ↩︎