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Biophys J. 2008 Aug;95(4):1627-38. doi: 10.1529/biophysj.108.130096. Epub 2008 May 23.

Quantitative analysis of G-actin transport in motile cells.

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1
Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.

Abstract

Cell migration is based on an actin treadmill, which in turn depends on recycling of G-actin across the cell, from the rear where F-actin disassembles, to the front, where F-actin polymerizes. To analyze the rates of the actin transport, we used the Virtual Cell software to solve the diffusion-drift-reaction equations for the G-actin concentration in a realistic three-dimensional geometry of the motile cell. Numerical solutions demonstrate that F-actin disassembly at the cell rear and assembly at the front, along with diffusion, establish a G-actin gradient that transports G-actin forward "globally" across the lamellipod. Alternatively, if the F-actin assembly and disassembly are distributed throughout the lamellipod, F-/G-actin turnover is local, and diffusion plays little role. Chemical reactions and/or convective flow of cytoplasm of plausible magnitude affect the transport very little. Spatial distribution of G-actin is smooth and not sensitive to F-actin density fluctuations. Finally, we conclude that the cell body volume slows characteristic diffusion-related relaxation time in motile cell from approximately 10 to approximately 100 s. We discuss biological implications of the local and global regimes of the G-actin transport.

PMID:
18502800
PMCID:
PMC2483760
DOI:
10.1529/biophysj.108.130096
[Indexed for MEDLINE]
Free PMC Article
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