PI3K (arrows) accumulates in the stretching pseudopods of a slithering cell.
Slime mold cells make a beeline for their bacterial food, and researchers have dissected the pathway that controls this directional travel. Bacterial molecules prod G-protein–coupled receptors on the cell surface, leading to activation of the proteins Ras and PI3K. In turn, PI3K cranks out PIP3, which spurs actin molecules to polymerize and push the cell membrane forward. But scientists didn't know what governs cells' random crawling in search of food.
Many of the same molecules participate, Sasaki et al. learned when they studied slime mold cells that lack G-protein–coupled receptor signaling. Ras and PI3K switched on, PIP3 formed, and cell extensions elongated...
