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Actin Network Architecture Can Determine Myosin Motor Activity

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Science  08 Jun 2012:
Vol. 336, Issue 6086, pp. 1310-1314
DOI: 10.1126/science.1221708

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Actin Up

Actomyosin interactions lie at the heart of fundamental cellular processes—including morphogenesis, establishment of polarity, and overall motility—but the general principles driving the spatiotempotal orchestration of these interactions have remained elusive. Working in vitro, using micropatterned substrates, Reymann et al. (p. 1310) demonstrate that myosins can use a “selection orientation” mechanism to pull selectively on actin filaments, contract the actin network and disassemble it, or walk on the filaments, align them, allow their growth, and control filament orientation.

Abstract

The organization of actin filaments into higher-ordered structures governs eukaryotic cell shape and movement. Global actin network size and architecture are maintained in a dynamic steady state through regulated assembly and disassembly. Here, we used experimentally defined actin structures in vitro to investigate how the activity of myosin motors depends on network architecture. Direct visualization of filaments revealed myosin-induced actin network deformation. During this reorganization, myosins selectively contracted and disassembled antiparallel actin structures, while parallel actin bundles remained unaffected. The local distribution of nucleation sites and the resulting orientation of actin filaments appeared to regulate the scalability of the contraction process. This “orientation selection” mechanism for selective contraction and disassembly suggests how the dynamics of the cellular actin cytoskeleton can be spatially controlled by actomyosin contractility.

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