Cell Biology

Moving Through a Crowd

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Science  25 Jul 2008:
Vol. 321, Issue 5888, pp. 467
DOI: 10.1126/science.321.5888.467a

Amigrating eukaryotic cell has a dense mesh of cortical actin at its leading edge, with long parallel actin bundles extending into microspikes and filapodia. Myosin X localizes at the ends of filapodia, where it may be involved in processes such as adhesion and signaling. How does myosin X find the appropriate actin filaments and travel along them to reach its destination?

Nagy et al. show that although myosin X processive runs on single filaments are short and rare, it moves robustly and at length on fascin-bundled actin, which makes up the core of filapodia. Myosin X has a short neck so that its step size is probably smaller than the actin pseudo-helical repeat, which might account for its low processivity on single filaments. On actin bundles it can move with one head tracking one filament and the other head on the adjacent filament. Furthermore, myosin X was observed to move even farther and faster on artificially bundled (by molecular crowding) actin, suggesting that filament proximity facilitates its movement rather than structural features specific to actin monofilaments. — VV

Proc. Natl. Acad. Sci. U.S.A. 105, 9616 (2008).

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