Quantitative analysis of G-actin transport in motile cells.
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.
Novak
Igor L
IL
Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.
Slepchenko
Boris M
BM
Mogilner
Alex
A
D001693:Biological Transport, Active / Q000502:physiology; D002465:Cell Movement / Q000502:physiology*; D003198:Computer Simulation; D008954:Models, Biological; D008956:Models, Chemical; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology
D020409:Molecular Motor Proteins