Slow and steady moves the cell

More actin-based protrusion should mean more cell movement, or so it has been thought. Yet depletion of the Ena/VASP family of actin-binding proteins, which promote lamellipodial protrusion rates, actually causes cells to move faster. New results from James Bear, Tatyana Svitkina, Frank Gertler (MIT, Cambridge, MA), and colleagues explain this counterintuitive effect by putting the emphasis on the quality rather than the quantity of protrusions.

The group boosted Ena/VASP levels at the plasma membrane of fibroblasts and saw increases in protrusion velocity. But the protrusions were quickly withdrawn as ruffles. Within these lamellipodia, actin filaments were longer and less branched than normal and ran parallel to the membrane instead of perpendicular. “This tells us that the geometry of actin polymerization is critical for regulating the rate and stability of protrusions,” says Gertler....