24 Feb 1999

Neurons are highly polarized cells, with certain proteins within them clearly restricted to specific regions of the plasma membrane. Yet they lack any obvious barriers to free protein diffusion that could explain this asymmetric distribution of proteins. In this week's Nature, Ira Mellman and colleagues at Yale University report that membrane proteins seem to interact with a new type of diffusion barrier-a specialized region in the cytoskeleton-and this is what impedes their progress. Using tiny silica beads, manipulated with laser tweezers, the researchers show where protein mobility is controlled.—June Kinoshita