Journal of Biochemistry Advance Access published online on November 13, 2008
Journal of Biochemistry, doi:10.1093/jb/mvn151
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The role of actomyosin contractility in the formation and dynamics of actin bundles during fibroblast spreading
Department of Physics, Graduate School of Science, Tohoku University, Sendai, Miyagi 980-8578, Japan
Name: Yosuke Senju, Mailing address: Aoba 6-3, Aramaki, Aoba-ku, Sendai, 980-8578, JAPAN, Telephone number: +81-22-795-6466, Fax number: +81-22-795-6774, E-mail address: yosuke{at}bio.phys.tohoku.ac.jp
Received October 13, 2008; Accepted October 22, 2008
| Abstract |
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We studied the process of formation of stress fibers and involvement of phosphorylation of myosin-II during spreading of Swiss 3T3 fibroblasts. In cells that were allowed to spread for 1 hour on a glass surface, circular bundles of actin and myosin-II filament were present. At 2–3 hours after the plating, cells showed a polygonal and polarized shape. The proportion of the cells having circular bundles was decreased, whereas that of the cells with straight bundles of actin filaments was increased. At 4 hours after the plating, cells were completely polarized and stress fibers were present at the periphery and the dorsal and ventral surfaces of the cells. Thus, spreading cells possessed different forms of actomyosin bundles corresponding to the cell shape. In circular bundles and stress fibers, myosin regulatory light chains were diphosphorylated. Formation of circular bundles and stress fibers was suppressed after the treatment of the cells with Y-27632, a Rho-kinase inhibitor, or blebbistatin, a myosin-II inhibitor. In digitonin-extracted cells, circular bundles as well as stress fibers contracted following the addition of Mg-ATP. These results suggest that circular bundles are contractile structures containing actin and phosphorylated myosin-II filaments, and the formation of circular bundles is regulated by Rho-kinase.
Key Words: actin, adhesion, dynamics, myosin, polarity
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