Deformations in actin comets from rocketing beads
Ewa Paluch 1, Jasper van der Gucht 1, Jean-François Joanny 1 and Cécile Sykes 1*
1 Institut Curie/CNRS
* To whom correspondence should be addressed. E-mail: cecile.sykes{at}curie.fr.
Submitted on April 27, 2006
Revised on June 9, 2006
Accepted on 12 July 2006
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Abstract |
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The mechanical and dynamical properties of the actin network are essential for many cellular processes like motility and division and there is a growing body of evidence that they are also important for adhesion and trafficking. The leading edge of migrating cells is pushed out by the polymerization of actin networks, a process orchestrated by crosslinkers and other actin binding proteins. In vitro physical characterizations show that these same proteins control the elastic properties of actin gels. Here we use a biomimetic system of Listeria monocytogenes, beads coated with an activator of actin polymerization, to assess the role of various actin-binding proteins in propulsion. We find that the properties of actin-based movement are clearly affected by the presence of crosslinkers. By monitoring the evolution of marked parts of the comet, we provide direct experimental evidence that the actin gel continuously undergoes deformations during the growth of the comet. Depending on the protein composition in the motility medium, deformations arise from either gel elasticity or monomer diffusion through the actin comet. Our findings demonstrate that actin-based movement is governed by the mechanical properties of the actin network, which are fine-tuned by proteins involved in actin dynamics and assembly.
Key Words:
Listeria, actin, actin binding proteins, actin gel elasticity, diffusion, motility
