Slide 002: "Cell motility" [ 00:00:26 ]

Go To Slide: Protein Polymers, Crawling Cells, and Comet Tails Cell motility Four types of biological motors Cell structure depends on protein filaments Actin filament structure Actin filament polymerization Most cells in the human body are bacteria Actin-based motility of the intracellular bacterial pathogen Listeria monocytogenes Listeria monocytogenes actin-rich clouds and tails in cytoplasmic extract What do we understand? What don t we understand? Force generation by protein polymerization: Thermodynamics What can we do? What can we do? Movement of L. monocytogenes in cytoplasmic extracts High-resolution tracking Trajectories of 1000 bacteria Trajectories of 1000 bacteria Speeds vary significantly among genetically identical individuals For each individual, speed and actin density both fluctuate Cross-correlations between speed and actin density fluctuations What can we do? Movement of ActA-coated beads Movement of ActA-coated beads in cytoplasmic extract Symmetry is broken by variations in actin dynamic behavior Elastic Brownian ratchet model Stochastic model for symmetry-breaking based on the elastic Brownian ratchet The simple 2-D stochastic model reproduces qualitative aspects of symmetry-breaking Actin polymerization distorts vesicles Movement of ellipsoidal beads Two preferred orientations What can we do? How will we dissect the molecular basis of these complex mechanics? Listeria monocytogenes ActA site-directed mutagenesis Mechanical phenotype 1: Change in path persistence Mechanical phenotype 2: Skidding What about cell crawling? Symmetry-breaking in fish skin cells Conclusions Acknowledgements