Biomedical Engineering Reference
In-Depth Information
Chapter 4
Involvement of Mechanical Strain
in Actin Network Reorganization
Actin network flow is an integral property of cell migration that is evident in many
cell types. To elucidate the mechanism of actin network flow and its role in the
migration process, this chapter outlines methods for tracking and mapping quantita-
tively actin network flow in the lamellipodia of fish keratocytes as highly suitable
models for cell migration research. Quantitative analysis of actin network deformation
associated with the flow is presented, and the contribution of negative deformation
to actin network disassembly is discussed with respect to coupling interactions
among mechanical and biochemical factors during cell migration.
4.1
Introduction
As discussed in Chap.
2
, an actively migrating cell on a substrate assumes a polarized
morphology, and undergoes motility through a series of complex but highly coordi-
nated processes that includes protrusion and attachment at the leading edge, and
retraction at the trailing edge. Rapidly migrating cells such as fish keratocytes
achieve continuous migration by synchronizing protrusion and retraction events
spatially and temporally through coupling mechanisms involving mechanical and
biochemical factors.
During cell migration, a combination of reaction forces (due to polymerization
against a rigid cell membrane) at the leading edge and contractile forces generated
by actomyosin interactions at the proximal site of the lamellipodium contributes to the
formation of retrograde flow of actin network toward the back of the lamellipodia
(where the cell nucleus is located). A few microns away from the leading edge, actin
filaments undergo severing and disassembly under the action of biochemical factors
such as ADF/cofilin. Thus, the actin network structure can be regarded as a complex
but spatiotemporally self-regulating system (Miyoshi et al.
2006
; Pollard and Borisy
2003
; Pollard
2003
; Kovar et al.
2006
; Higashida et al.
2004
).
