Molecular Motor Function in Organelle Transport

Intracellular organelle transport relies on specialised molecular motors that convert chemical energy into mechanical force along cytoskeletal tracks. Kinesins and dyneins navigate microtubules over long distances, while myosin motors traverse actin filaments to mediate short-range delivery and tethering. These motors bind cargo via adaptor proteins and small GTPases, integrating motor activity with track assembly to ensure precise spatial distribution of mitochondria, secretory vesicles and pigment granules. Regulatory mechanisms include autoinhibition of motor domains, cargo‐activated conformational changes and coordination with actin nucleators and elongating factors. The interplay between motor processivity, filament dynamics and membrane‐associated signalling networks underpins essential cellular processes such as synaptic transmission, immune cell activation and pigmentation. Defects in motor function contribute to neurodegeneration, immunodeficiency and pigmentary disorders, emphasising the need for an integrated understanding of motor–track–cargo assemblies. Recent advances have begun to unravel how motors are coupled with actin‐assembly factors to generate organelle‐based transport networks, illuminating both evolutionary origins and therapeutic opportunities.

Research from Nature Portfolio

Recent studies have traced the origin of actin‐based organelle transport mechanisms to unicellular ancestors of animals. Actin nucleators of the SPIRE family, together with formin subunits and class-5 myosins, are shown to cooperate in early eukaryotes to drive exocytic cargo delivery, demonstrating functional conservation of motor–track assemblies across holozoans. This work reveals that SPIRE–formin–myosin complexes formed an ancestral transport module later co-opted in multicellular lineages. Complementing this evolutionary perspective, investigations into Rab27a effectors have established that Rab27a not only recruits myosin-Va adaptors but also organelle‐associated SPIRE proteins. By anchoring both track‐building factors and motors on melanosome membranes, Rab27a orchestrates a self-contained transport network that disperses organelles over long distances via dynamic actin meshes. Together, these findings highlight an integrated paradigm in which motors and nucleators assemble at cargo surfaces to implement robust actin-dependent trafficking.

Molecular Motor Function in Organelle Transport publication trend

The graph below shows the total number of articles in molecular motor function in organelle transport across all publications each year (not limited to Nature Index journals).

Technical terms

Molecular motor: A protein that converts ATP hydrolysis into directed movement along cytoskeletal filaments.

Actin filament: A helical polymer of actin monomers forming tracks for myosin motor movement.

Microtubule: A tubular polymer of tubulin dimers serving as long-range transport pathways for kinesin and dynein motors.

Adaptor protein: A molecule that links a motor to its cargo, often recognising both motor tail domains and organelle surface markers.

Rab GTPase: A family of small GTP-binding proteins that specify organelle identity and recruit motor and tethering factors.

SPIRE: An actin nucleator that initiates filament assembly, often cooperating with formin proteins to shape actin networks.

Formin: An actin-assembly factor that elongates actin filaments processively at their barbed ends.

References

1. Identification of a third myosin-5a-melanophilin interaction that mediates the association of myosin-5a with melanosomes. eLife (2024).
2. Actomyosin organelle functions of SPIRE actin nucleators precede animal evolution. Communications Biology (2024).
3. Coordinated recruitment of Spir actin nucleators and myosin V motors to Rab11 vesicle membranes. eLife (2016).
4. Slac2-a/Melanophilin, the Missing Link between Rab27 and Myosin Va IMPLICATIONS OF A TRIPARTITE PROTEIN COMPLEX FOR MELANOSOME TRANSPORT*. Journal of Biological Chemistry (2002).
5. Rab27a co-ordinates actin-dependent transport by controlling organelle-associated motors and track assembly proteins. Nature Communications (2020).