APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014;
Denver, Colorado
Session F11: Focus Session: Active Soft Matter I - Transport, Biomimetics and Dynamic Response
8:00 AM–11:00 AM,
Tuesday, March 4, 2014
Room: 203
Sponsoring
Units:
DPOLY GSNP DBIO
Abstract ID: BAPS.2014.MAR.F11.2
Abstract: F11.00002 : Cytoskeletal organization by motor and polymerization forces
8:36 AM–9:12 AM
Preview Abstract
Abstract
Author:
Gijsje Koenderink
(FOM Institute AMOLF)
Cells need to constantly change their change to perform vital functions,
such as growth, division, and movement. Dysregulation of cell shape can have
severe consequences such as cancer. Our goal is to resolve physical
mechanisms that contribute to cell shape control. For this purpose, we study
simplified experimental model systems reconstituted from purified cellular
components. In this talk, I will give two examples of our recent work. The
first example concerns active contractility of the actin cortex, which lies
underneath the cell membrane and drives shape changes by means of myosin
motors. Using in vitro models, we studied how myosin motors and actin
filaments collectively self-organize into force-generating arrays. I will
show that motors contract actin networks only above a sharp threshold in
crosslink density. We discovered that right at this threshold, the motors
rupture the network into clusters that exhibit a broad distribution of
sizes, as expected in filamentous networks near a percolation threshold. The
second example I will discuss concerns cell shape polarization directed by
interactions between the actin and microtubule (MT) cytoskeletons. A
prominent example is the guidance of MT growth along F-actin bundles towards
specific targets, i.e. focal adhesions. It has been suggested that MT
end-tracking proteins ($+$TIPs) that also bind F-actin are responsible for
this process. We built an in vitro system involving a simplified actin-MT
crosslinker molecule and could show that the interaction between MT ends and
actin is sufficient to capture and re-direct MT growth along actin bundles.
By keeping MT growth tightly coupled to F-actin, this mechanism allows
linear arrays of actin bundles to act as templates for MT organization.
Instead, when interacting with single actin filaments, MT ends become the
dominant organizing factor, exerting forces that align, pull and even
transport actin filaments in the direction of MT growth. We conclude that
actin and MTs can influence each other's organization through coupling by
$+$TIP proteins.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.MAR.F11.2