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Updated: Jul 3, 2026
06:53
Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers
Published on: May 4, 2022
A myosin motor that selects bundled actin for motility
Stanislav Nagy1, Benjamin L Ricca, Melanie F Norstrom
1Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA.
Summary
Myosin X motors navigate the cell cytoskeleton by recognizing and moving along specific fascin-actin bundles within filopodia. This targeted motility mechanism ensures cargo delivery to precise locations within eukaryotic cells.
Area of Science:
- Cell Biology
- Cytoskeletal Dynamics
- Molecular Motors
Background:
- Eukaryotic cells utilize cytoskeletal filaments for intracellular transport.
- The cell cortex features complex actin arrangements, posing challenges for motor protein navigation.
- The mechanism by which myosin motors select specific actin filaments for cargo transport remains unclear.
Purpose of the Study:
- To investigate how myosin X motors identify and move along specific actin filaments within filopodia.
- To elucidate the role of fascin-actin bundles in directing myosin X motility.
- To understand the in vivo relevance of myosin X's interaction with actin structures.
Main Methods:
- In vitro motility assays using purified myosin X and actin filaments.
- Supercoiling assays to observe myosin X's interaction with individual actin filaments.
- Analysis of myosin X processivity on fascin-actin bundles and artificial actin bundles.
- In vivo experiments using fascin-depleted HeLa cells to assess myosin X localization and function.
Main Results:
- Myosin X exhibits poor motility on individual actin filaments but moves robustly and processively along fascin-actin bundles.
- Myosin X's processivity is dependent on the parallel and closely spaced arrangement of actin filaments, as demonstrated with artificial bundles.
- Myosin X localization at filopodial tips is disrupted in cells lacking fascin, indicating its in vivo importance.
- Myosin X selects fascin-actin bundles for motility, distinguishing them from other cortical actin structures.
Conclusions:
- Myosin X recognizes the structural organization of parallel, bundled actin filaments, specifically fascin-actin bundles.
- This recognition mechanism enables myosin X to sort cargo and direct it to specific target sites within filopodia.
- The study reveals a novel mechanism for cargo targeting based on the local structural properties of cytoskeletal filaments.
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