Ewa Paluch

Actin cortex mechanics and cell shape

Current research

The cell cortex is a network of actin, myosin and associated proteins that lies under the plasma membrane and determines the shape of most animal cells. The cortex enables the cell to resist externally applied stresses and to exert mechanical work. As such, it plays a role in normal physiology during events involving cell deformation such as mitosis, cytokinesis, and cell locomotion, and in the pathophysiology of diseases such as cancer where cortical contractility is upregulated. Despite its importance, little is known about how the cortex is assembled and regulated.

As the cortex is an intrinsically mechanical structure (its biological activity results from its ability to contract and to exert forces), its physiological properties cannot be understood in isolation from its mechanics. The main focus of the group is to understand how these mechanical properties are determined by the molecular components of the cortex and how these properties are regulated, locally and globally, to allow the cell to undergo deformations, particularly during cytokinesis and migration. We combine biophysical and molecular approaches and focus on:

        •    the molecular basis of cortical mechanical properties,
        •    the mechanisms of formation of blebs, cellular protrusions directly resulting from cortical contractions,
        •    the role of cortex tension and blebs during cytokinesis,
        •    the formation and role of different types of protrusions during migration in vivo

Figure 1: A bleb (spherical membrane protrusion) induced by laser-ablation of the actin cortex

Figure 2: Blebbing during cytokinesis in a mouse fibroblast (green: myosin-GFP)

Future prospects and goals

We want to further analyze the mechanical and molecular mechanisms of protrusion formation in 3-dimensional environments.
Ultimately, we also want to use cellular fragments to better understand the minimal components required for cortical contractility and shape dynamics.

About

2005: PhD in Biophysics, Université Paris 7 / Institut Curie, Paris, France 2005: Staff scientist at the Max Planck Institute of Molecular Cell Biology and Genetics, Dresden since 2006: Joint MPI-CBG / PAN Group leader, Dresden

Selected publications

Tinevez J.Y., Schulze U., Salbreux G., Roensch J, Joanny J.F. and E. Paluch (2009): Role of cortical tension in bleb growth, PNAS 106:18581-6

Paluch E. and C.P. Heisenberg (2009): Biology and physics of cell shape changes in development, Curr. Biol. 19:R790-9

Paluch E. and G. Charras (2008): Blebs lead the way: how to migrate without lamellipodia, Nat. Rev. Mol. Cell Biol. 9:730-736

Paluch E., van der Gucht J., Joanny J.-F. and C. Sykes (2006): Deformations in actin comets from rocketing beads. Biophys. J. 91: 3113-3122

van der Gucht J., Paluch E., Plastino J. and C. Sykes (2005): Stress release drives symmetry breaking for actin-based movement. PNAS 102:7847-7852

Paluch E., Piel M., Prost J., Bornens M. and C. Sykes (2005): Cortical actomyosin breakage triggers shape oscillation in cells and cell fragments. Biophys. J. 89:724-733 

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