Self-organization of actin filament orientation in the dendritic-nucleation/array-treadmilling model
Self-organization of actin filament orientation in the dendritic-nucleation/array-treadmilling model
Date
2006-11-16
Authors
Schaus, Thomas E.
Taylor, Edwin W.
Borisy, Gary G.
Taylor, Edwin W.
Borisy, Gary G.
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Keywords
Lamellipodium
Cytoskeleton
Plasma membrane
Cytoskeleton
Plasma membrane
Abstract
The dendritic-nucleation/array-treadmilling model provides a conceptual framework for
the generation of the actin network driving motile cells. We have incorporated it into a 2-D,
stochastic computer model to study lamellipodia via the self-organization of filament
orientation patterns. Essential dendritic-nucleation sub-models were incorporated,
including discretized actin monomer diffusion, Monte-Carlo filament kinetics, and flexible
filament and plasma membrane mechanics. Model parameters were estimated from the
literature and simulation, providing values for the extent of the leading edge
branching/capping-protective zone (5.4 nm) and the auto-catalytic branch rate (0.43 /s).
For a given set of parameters the system evolved to a steady state filament count and
velocity, at which total branching and capping rates were equal only for specific
orientations; net capping eliminated others. The standard parameter set evoked a sharp
preference for the ±35 deg. filaments seen in lamellipodial electron micrographs, requiring
~ 12 generations of successive branching to adapt to a 15 deg. change in protrusion
direction. This pattern was robust with respect to membrane surface and bending energies
and to actin concentrations, but required protection from capping at the leading edge and
branching angles greater than 60 deg. A +70/0/-70 deg. pattern was formed with flexible
filaments ~ 100 nm or longer and with velocities less than ~ 20% of free polymerization
rates.
Description
Author Posting. © The Author(s), 2006. This is the author's version of the work. It is posted here by permission of National Academy of Sciences of the USA for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences 104 (2007): 7086-7091, doi:10.1073/pnas.0701943104.