Secrets of Attraction (among Cells)

esearchers have known for years that when one cell wants to attract another, it releases a trail of signaling molecules that travel toward the second cell, docking on its receptors. Then, like an animal following a scent, the second cell follows the trail. But the process by which this cell moves itself toward the first, known as chemotaxis, has long baffled scientists.

What’s especially puzzling is that the second cell’s receptors are equally distributed around its perimeter. Yet the cell only extends pseudopods—the “feet” it uses to drag itself across a surface—on its side facing the target. How, researchers wondered, does the cell determine which side will become the leading edge on which it stretches out its pseudopods?

To crack this conundrum, a team led by biochemist Peter Devreotes, Ph.D., has been studying a single-cell amoeba named Dictyostelium, which behaves like many chemotactic cells when it communes with its fellow amoebae. By sorting through which proteins become unevenly distributed in the amoeba during chemotaxis, the researchers have found that one type, called G-protein, clumps together to form the leading edge of the cell. It is this protein, they say, that sensitizes the edge to stimulation from signaling molecules and allows it to home in on its target.

So why do we care? “Chemotaxis is important in everything from inflammation, disease fighting and blood vessel growth to wound healing and prenatal development,” Devreotes says. “If we understand this process, we should be able to develop new treatments that put it to use to fight these conditions.”

-— Kate O'Rourke