52. Guo WH,Wang YL (2007) Retrograde fluxes of focal adhesion proteins in response to cell migration and mechanical signals. Mol Biol Cell. 18: 4519–4527. 53. Waterman-Storer C (2002) Fluorescent speckle microscopy (FSM) of microtu- bules and actin in living cells. Curr Protoc Cell Biol. Chapter 4: Unit 4.10. 54. Ballestrem C, Hinz B, Imhof BA, Wehrle-Haller B (2001) Marching at the front and dragging behind: differential alphaVbeta3-integrin turnover regulates focal adhesion behavior. J Cell Biol. 155: 1319–1332. 55. Saffman PG, Delbru¨ck M (1975) Brownian motion in biological membranes. Proc. Nat. Acad. Sci., USA, 72: 3111–3113. 56. Gambin Y, Lopez-Esparza R, Reffay M, Sierecki E, Gov NS, et al. (2006) Lateral mobility of proteins in liquid membranes revisited. Proc. Nat. Acad. Sci., USA, 103: 2098–2102. 57. Pelham RJ Jr, Wang Y-L (1997) Cell locomotion and focal adhesions are regulated by substrate flexibility. Proc. Natl. Acad. Sci. USA 94: 13661–13665. 58. Smith A, Carrasco YR, Stanley P, Kieffer N, Batista FD, et al. (2005) A talin- dependent LFA-1 focal zone is formed by rapidly migrating T lymphocytes. J Cell Biol. 170: 141–151. 59. Eddy RJ, Pierini LM, Matsumura F, Maxfield FR (2000) Ca2+-dependent myosin II activation is required for uropod retraction during neutrophil migration. J Cell Sci. 113: 1287–1298. 60. Kazarov AR, Yang X, Stipp CS, Sehgal B, Hemler ME (2002) An extracellular site on tetraspanin CD151 determines alpha 3 and alpha 6 integrin-dependent cellular morphology. J Cell Biol. 158: 1299–1309. 61. Ziyyat A, Rubinstein E, Monier-Gavelle F, Barraud V, Kulski O, et al. (2006) CD9 controls the formation of clusters that contain tetraspanins and the integrin alpha 6 beta 1, which are involved in human and mouse gamete fusion. J Cell Sci. 119: 416–424. 62. Hemler ME (2003) Tetraspanin proteins mediate cellular penetration, invasion, and fusion events and define a novel type of membrane microdomain. Annu Rev Cell Dev Biol. 19: 397–422. Integrin-Ligand Interactions Control Migration 63. Giannone G, Dubin-Thaler BJ, Dobereiner HG, Kieffer N, Bresnick AR, et al. (2004) Periodic lamellipodial contractions correlate with rearward actin waves. Cell. 116: 431–443. 64. Giannone G, Dubin-Thaler BJ, Rossier O, Cai Y, Chaga O, et al. (2007) Lamellipodial actin mechanically links myosin activity with adhesion-site formation. Cell. 128: 561–575. 65. Grashoff C, Hoffman BD, Brenner MD, Zhou R, Parsons M, et al. (2010). Measuring mechanical tension across vinculin reveals regulation of focal adhesion dynamics. Nature. 466: 263–266. 66. Oakes PW, Beckham Y, Stricker J, Gardel ML (2012) Tension is required but not sufficient for focal adhesion maturation without a stress fiber template. J Cell Biol. 196: 363–374. 67. Wehrle-Haller B, Imhof B (2002) The inner lives of focal adhesions. Trends Cell Biol. 12: 382–389. Review. 68. Yam PT, Wilson CA, Ji L, Hebert B, Barnhart EL, et al. (2007) Actin-myosin network reorganization breaks symmetry at the cell rear to spontaneously initiate polarized cell motility. J Cell Biol. 178: 1207–1221. 69. Cai Y, Biais N, Giannone G, Tanase M, Jiang G, et al. (2006) Nonmuscle myosin IIA-dependent force inhibits cell spreading and drives F-actin flow. Biophys J. 91: 3907–3920. 70. Ballestrem C, Erez N, Kirchner J, Kam Z, Bershadsky A, et al. (2006) Molecular mapping of tyrosine-phosphorylated proteins in focal adhesions using fluores- cence resonance energy transfer. J Cell Sci. 119: 866–875. 71. Eichinger L, Pachebat JA, Glo¨ckner G, Rajandream MA, Sucgang R, et al. (2005) The genome of the social amoeba Dictyostelium discoideum. Nature. 435: 43–57. 72. Parent CA (2004) Making all the right moves: chemotaxis in neutrophils and Dictyostelium. Curr Opin Cell Biol. 16: 4–13. PLoS ONE | www.plosone.org 15 July 2012 | Volume 7 | Issue 7 | e40202