Actin network mechanics and cell motility

The structural and mechanical properties of cytoskeletal networks are important determinants of their ability to generate protrusive forces in cells. The interplay between these properties, however, is not fully understood. Moreover, these properties are controlled by numerous actin binding proteins in vivo. In order to understand the basic principles of such complex systems, we examine the structural and mechanical properties of reconstituted in vitro actin networks in the presence of the actin regulating Vasodilator Stimulating Protein (VASP). We study VASP’s effects in two systems using multiple techniques. The first approach observes bulk assays using confocal microscopy, rheology and both active and passive microrheology in order to determine the fundamental structural and viscoelastic properties of VASP-mediated actin networks. The second approach investigates VASP’s influence on biomimetic assays in which microspheres are propelled by actin “comet tails” much like the bacteria Listeria monocytogenes. These assays more faithfully reproduce cellular and bacterial protrusion.
Nematode sperm cells use the Major Sperm Protein (MSP) rather than actin for protrusion. MSP is functionally similar to, though biochemically dissimilar from actin. We study the structural and mechanical properties of reconstituted MSP networks using the techniques described above. By comparing these two different cytoskeletal systems that have identical roles in cell movement, we hope to define the universal biochemical and physical properties governing cell motility.

More information: Brian Gentry
Collaborators: Julie Plastino, Institut Curie, Paris, France and Laurent Kreplak, Dalhousie University, Halifax, Canada