

Preprint 99/2006
Actin Dynamics and Cell Motility: Minimal Models for the Initiation of Cell Movement
Jan Fuhrmann, Josef Käs, and Angela Stevens
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Submission date: 15. Sep. 2006
Pages: 17
Bibtex
MSC-Numbers: 92C17
PACS-Numbers: 87.17.Aa, 87.17.Jj
Keywords and phrases: cell motility, actin dynamics, resting cell, cell movement
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Abstract:
The actin driven motility of eukaryotic cells has been one of the
most rapidly developing research areas in biology over the last decades.
Polymerization and depolymerization of filaments is the driving force
behind the crawling motion of individual cells. There is a large variety
of proteins known or suspected to be involved in this polymerization
machinery. The question arises which of them are essential for the
ability of a cell to move directionally. Many studies have been conducted
on cells which are already in motion - or at least polarized with
established lamellipods, and several mechanisms have been shown to
be essential for sustaining the large movement velocities observed
in vivo. The question we addressed here is what minimal requirements
have to be met by a non polarized resting cell to react to an external
stimulus in a prescribed direction.
For that purpose, we develop a minimal model for actin turnover, examine
its steady states, and try to figure out which types of perturbations
are most appropriate to turn the cytoskeleton into a polarized state
which may be viewed as the beginning of directed motion. We analyze
a one dimensional model for a resting cell describing the actin network
therein. For the time being we restrict ourselves to describing the
dynamics of barbed ends accumulating near the cell membrane. Pushing
the membrane forward and establishing a lamellipod would be the next
step in the initiation of movement and shall be investigated in future.
In our simulations we found that very few mechanisms are sufficient
to create a significant modification of the cytoskeleton. Moreover
we see a striking effect of the diffusion coefficient for the actin
monomers on the strength of this modification.