Cellular plasma membrane domains.

The plasma membranes of migrating cells differentiate into at least three distinct domains as defined by the laser tweezers and the motile behaviour of particles bound to specific membrane glycoproteins. These domains are important for steps in the cell migration process. First, there is a domain at the leading edge of the lamellipodium where preferential attachment of cross-linked glycoproteins to the cytoskeleton occurs. The second domain at the rear of the cell is differentiated for releasing from substrata and shows decreased support of the membrane by the cytoskeleton. The third domain is the highly curved region(s) of the plasma membrane wherein certain membrane glycoproteins concentrate and is a site for controlling extension and attachment. Using single particle tracking and video analysis we find that the quantitative differences between plasma membrane domains are in the 4-20-fold range at any given time. These values are consistent with the rapid fluctuations seen in cell migration rates and directions. Over a longer time-scale, cells can possibly integrate these selective advantages to give a much higher overall fidelity for cell chemotaxis and neuronal path finding.