1. Listeria Cycle of Propagation

4. Cell migration: a cyclic process of force generation
Membrane-Cyto. Adhesion Resists Extension a PIP2. Sheetz, Nature Rev. MCB. 2:392 (2001)
Extracellular Matrix Adhesion
Linked to Force Generation by Rearward Flow
Cell migration 5 STEP cycle: describe cycle
Focus our attention on the 2 STEP extension and attachement
Lamellipodial extension and ECM probing involve forces generated by actin:
Forward on the memebrane and rearward on integrins
Laser tweezers experiments allow us to explore force exerted by the actin reaward flow on integrins
Mike already described the effect of forces on the integrin-cytoskeleton interactions
Transition: definition of the lamellipodia
How do cells locally trans-duce Matrix rigidity into a signal used to direct cell edge extension?

5. Lamellipodial extension driven by actin assembly
Rac-GTPase
lamellipodia
Difference between the lamellipodia and the lamella
Protrusion of the membrane during cell edge extension is driven by actin polymerization and depolymerization.
Polymerization at the front
Stabilization of the meshwork
Depolymerization at the back
Relatively constant length and a stationary gradient reflecting a steady-state process of assembly at the front and disassembly at the rear
Account for extension, but ECM probing?
No myosin
Myosin is required for migration and cell spreading
The cytoskeletal treadmilling cycle can power actin-based movement of beads or bacteria, without the need for myosin-based contractility
Components that will be involved in this talk are LIM kinase, cofilin, Rac GTPase.
lamella
Actin plolymerization (front) and
depolymarization(rear)
define the lamellipodial width
Forces generated by Myosins?
Cell spreading and migration require myosin activity

6. Model for Propulsion of Listeria

14. Several Pathogens Co-Opt Actin

19. Salmonella Injects Critical Proteins

20. Shigella Targets MTs and Actin

21. Mycobacteria Modify Actin Dynamics

23. Enteropathic E. coli Break Contacts