Published online
doi:10.1083/jcb.200703178
The Journal of Cell Biology, Vol. 179, No. 2, 229-238
The Rockefeller University Press, 0021-9525 $30.00
© Tokuo et al.
The motor activity of myosin-X promotes actin fiber convergence at the cell periphery to initiate filopodia formation
Hiroshi Tokuo1,
Katsuhide Mabuchi2, and
Mitsuo Ikebe1
1 Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655
2 Muscle Research Group, Boston Biomedical Research Institute, Watertown, MA 02472
Correspondence to Mitsuo Ikebe: Mitsuo.Ikebe{at}umassmed.edu
Filopodia are actin-rich fingerlike protrusions found at the leading edge of migrating cells and are believed to play a role in directional sensing. Previous studies have shown that myosin-X (myoX) promotes filopodia formation and that this is mediated through its ability to deliver specific cargoes to the cell periphery (Tokuo, H., and M. Ikebe. 2004. Biochem Biophys. Commun. 319:214–220; Zhang, H., J.S. Berg, Z. Li, Y. Wang, P. Lang, A.D. Sousa, A. Bhaskar, R.E. Cheney, and S. Stromblad. 2004. Nat. Cell Biol. 6:523–531; Bohil, A.B., B.W. Robertson, and R.E. Cheney. 2006. Proc. Natl. Acad. Sci. USA. 103:12411–12416; Zhu, X.J., C.Z. Wang, P.G. Dai, Y. Xie, N.N. Song, Y. Liu, Q.S. Du, L. Mei, Y.Q. Ding, and W.C. Xiong. 2007. Nat. Cell Biol. 9:184–192). In this study, we show that the motor function of myoX and not the cargo function is critical for initiating filopodia formation. Using a dimer-inducing technique, we find that myoX lacking its cargo-binding tail moves laterally at the leading edge of lamellipodia and induces filopodia in living cells. We conclude that the motor function of the two-headed form of myoX is critical for actin reorganization at the leading edge, leading to filopodia formation.
Abbreviations used in this paper: FKBP, FK506-binding protein; FN, fibronectin; myoV, myosin-Va; myoVII, myosin-VIIa; myoX, myosin-X; SAH, stable
helix; shRNA, small hairpin RNA.

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