A mechanism for actin based propulsion in morpho-dynamics, the force-velocity relation of fish keratocytes and reconstituted systems

Date

Feb 17, 2011

Time

11:00 AM - 12:00 PM

Speaker

Martin Falcke

Affiliation

Max Delbrück Center for Molecular Medicine Berlin, Germany

Language

en

Main Topic

Biologie

Other Topics

Biologie

Host

Ewa Paluch

Description

The morpho‐dynamics of the lamellipodium leading edge have been shown to exhibit a few phenotypes, which are controlled by cell signaling (1). The variety of phenotypes reveals the internal dynamics of actin polymerization and retrograde flow inside the lamellipodium. Measurements of the force‐velocity relation of motile fish keratocytes with an AFM cantilever represent another dynamic experiment allowing for drawing conclusions on the internal processes (2). Actin based motility has been reconstituted with ActA coated oil droplets (3) and ActA coated beads (4). Both systems exhibit steady and saltatory motion. We present a mathematical model of actin based propulsion which provides a mechanism for velocity oscillations of Listeria (5), beads and oil droplets (6). It also describes the mechanisms of the morpho‐dynamic phenotypes (7) and the force velocity relation. The model accounts for the existence of two functionally different regions of the lamellipodium actin network observed in many studies (8). Network behavior is dominated by semi-flexible properties of filaments near the leading edge membrane, and it is more gel-like further towards the cell body (9). We include actin polymerization, filament binding to the leading edge membrane, retrograde flow, contraction of the actin network by myosin and a simple description of cell adhesion to the substrate into the model. 1. Machacek, M., and G. Danuser. 2006. Morphodynamic Profiling of Protrusion Phenotypes. Biophys J 90:1439‐1452. 2. Prass, M., K. Jacobson, A. Mogilner, and M. Radmacher. 2006. Direct measurement of the lamellipodial protrusive force in a migrating cell. J. Cell Biol. 174:767‐772. 3. Trichet, L., O. Camp? s, C. Sykes, and J. Plastino. 2007. VASP Governs Actin Dynamics by Modulating Filament Anchoring. Biophysical Journal 92:1081‐1089. 4. Bernheim‐Groswasser, A., J. Prost, and C. Sykes. 2005. Mechanism of Actin‐Based Motility: A Dynamic State Diagram. Biophys J 89:1411‐1419. 5. Gholami, A., M. Falcke, and E. Frey. 2008. Velocity oscillations in actin‐based motility. New Journal of Physics 10:033022. 6. Enculescu, M., A. Gholami, and M. Falcke. 2008. Dynamic regimes and bifurcations in a model of actin‐based motility. Physical Review E 78:031915. 7. Enculescu, M., M. Sabouri‐Ghomi, G. Danuser, and M. Falcke. 2010. Modeling of Protrusion Phenotypes Driven by the Actin‐Membrane Interaction. Biophysical Journal 98:1571‐1581. 8. Zimmermann, J., M. Enculescu, and M. Falcke. 2010. Leading edge ‐ gel coupling in lamellipodium motion. Physical Review E 82:051925. 9. Laurent, V. M., S. Kasas, A. Yersin, T. E. Schäffer, S. Catsicas, G. Dietler, A. B. Verkhovsky, and J.‐J. Meister. 2005. Gradient of Rigidity in the Lamellipodia of Migrating Cells Revealed by Atomic Force Microscopy. Biophys J 89:667‐675.

Last modified: May 27, 2011, 4:35:29 PM