Reporting in the current issue of the journal Cell, the scientists show that a protein called PTEN goes to the back of the cell when a chemical attractant is sensed, allowing the cell to move purposefully toward the attractant. Because PTEN "brings up the rear," the molecules crucial for allowing the cell to reach out and move forward are restricted to the front of the cell.
"How do cells determine which direction to go to find an attractant? How do they sense the differences in concentration of the chemical, alter their membranes and move forward?" asks Peter Devreotes, Ph.D., professor and director of cell biology in the school's Institute for Basic Biomedical Sciences. "It's a very complex puzzle, and we've found another piece."
Postdoctoral fellow Miho Iijima, Ph.D., and Devreotes used specially labeled versions of PTEN that glowed green to see where the protein is in the cell during movement of living amoeba. They also monitored the movement and sensing abilities of amoeba whose PTEN gene was removed or altered.
"PTEN is found only in the back of the cell in moving amoeba, and is actually attached to the cell's membrane," says Devreotes. "Without PTEN or without it attached properly, the amoeba couldn't determine direction as well. Instead of moving in a straight line and adjusting quickly if the source of the attractant is moved, cells without PTEN have bigger 'fronts' that tugged them in a number of directions at once, impeding their progress."
In the same issue of Cell, other researchers report that another protein is found only in the front of amoeba. The two reports fit well together because PTEN and the other protei
Contact: Joanna Downer
Johns Hopkins Medical Institutions