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A cytoskeletal demolition worker: myosin II acts as an actin depolymerization agent.

Lior Haviv¹, David Gillo, Frederic Backouche

¹Department of Chemical Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, Israel.

Journal of Molecular Biology

|November 21, 2007

Summary

Myosin II motors actively control actin bundle turnover in a concentration-dependent manner. These motors initiate disassembly through unbundling and depolymerization, suggesting a direct role in actin turnover.

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Area of Science:

Cell Biology
Cytoskeletal Dynamics
Molecular Motors

Background:

Myosin II motors are crucial for cellular processes involving cytoskeletal dynamics.
Their role in actin bundle turnover and filament recycling is established but not fully understood.
A link exists between myosin II ATPase activity and actin turnover rates.

Purpose of the Study:

To investigate the direct role of myosin II motors in actin turnover.
To elucidate the mechanism by which myosin II influences actin bundle disassembly.
To explore the concentration-dependent effects of myosin II on actin dynamics in vitro.

Main Methods:

High-resolution cryo-transmission electron microscopy (cryo-TEM).
In vitro reconstitution assays to observe myosin II and actin interactions.
Controlled variation of myosin II concentrations.

Main Results:

Myosin II motors control actin bundle turnover in a concentration-dependent manner.
Actin bundle disassembly proceeds in two stages: unbundling and depolymerization.
Evidence suggests myosin II directly participates in actin depolymerization.

Conclusions:

Myosin II motors possess direct actin depolymerization capabilities beyond contraction.
These motors may regulate actin turnover in vivo, potentially by fine-tuning local concentration and activity.
Findings offer new insights into the multifaceted roles of myosin II in cytoskeletal regulation.