Biomedical Engineering Reference
In-Depth Information
Chapter 5
Regulation of Actin Network Dynamics
by Actomyosin Contractility
To clarify the self-regulatory nature of the actin cytoskeleton in migrating cells, this
chapter explores the role of actomyosin contractility in the process. We focus on the
interaction between actin and myosin II: the two principal components of the cyto-
skeleton that play key roles in cell migration. Using perturbation approach, an
indepth analysis is carried out to determine how activating or inhibiting the activity
of myosin II affects the dynamics of lamellipodial actin network during cell migra-
tion. We present a mechanical regulatory pathway that highlights the roles of
mechanical factors in the regulation of actin dynamics in migrating cells.
5.1
Introduction
It is well established that the interaction between F-actin and myosin II generates
contractile forces especially along stress fibers (SFs) that drive actin network
transport and also cause the forward translocation of the cell body (Verkhovsky
et al.
1999
; Svitkina et al.
1997
). Moreover, studies have demonstrated that these
contractile forces are necessary for the formation and stability of SF (Sato et al.
2006
; Costa et al.
2002
) and focal adhesions (Choquet et al.
1997
; Kaverina et al.
2002
; Tan et al.
2003
). Indeed, it is well known that cell migration is impaired when
either myosin II or actin polymerization is inhibited.
Probing the dynamics of the F-actin network during cell migration using such
quantitative tools as fluorescent speckle microscopy (FSM) (Waterman-Storer et al.
1998
; Danuser and Waterman-Storer
2006
) combined with computer tracking algo-
rithms have provided useful insights into the organization of cytoskeletal functions.
For instance, as discussed in Chap.
4
, information from F-actin network flow can be
utilized to determine quantitatively the deformation induced in the actin filament
network in the lamellipodia during cell migration. It is excepted that this deformation,
in conjunction with the action of biomechanical factors such as cofilin, contributes
