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Myosin II contributes to cell-scale actin network treadmilling through network disassembly.
Wilson CA, Tsuchida MA, Allen GM, Barnhart EL, Applegate KT, Yam PT, Ji L, Keren K, Danuser G, Theriot JA
Nature 2010 May 20 465(7296):373-7

Selected by | Frank Nelson and Kevin Conley, University of Washington, United States of America

Myosin II: a motor or a timing belt? Non-muscle myosin generates crawling locomotion by stabilizing the front and destabilizing actin in the rear of the cell to create a treadmill-like ‘rear-end drive’.

Muscle myosin generates movement by hydrolyzing ATP to activate ratcheting along an actin filament. In motile cells, a novel form of locomotion has been revealed that also involves actomyosin interaction and ATP hydrolysis, but in a mechanism more akin to a timing belt acting across the cell. In this study, Wilson et al. watched the movement of individual fluorescent markers across fish cytoskeletons to show that crawling locomotion involves myosin II stabilizing one end of the cell while disassembling actin at the other end. This gradual formation and reorganization of an actomyosin network allows the rear to flow forward to create motion, as with a treadmill driven at the rear-end, in contrast to myosin moving along actin in contractile systems. The long-range control of spatial and temporal disassembly of actin appears to be coordinated by myosin II but the mechanism is unclear. Some studies suggest a similar mechanism may be used in the kinetochore during cell division {1}, indicating that this timing belt role of non-muscle myosin may be quite common. Thus, the actomyosin interaction that acts as a ratcheting motor in muscle takes a new form with non-muscle myosin II to create a timing belt that coordinates actin dynamics across the cell to stabilize the front but destabilize the rear, resulting in locomotion by a ‘rear-end drive’.

References: {1} Robinson and Snyder, Protoplasma 2005, 225:113-22 [PMID:15868218].

Evaluated 8 September 2010