Actin crosslinking proteins at the leading edge.

The lamellar membrane at the leading edge of motile cells participates in a series of complex movements that involve the assembly and reorganization of actin bundles and networks, both structures formed by actin crosslinking proteins. Immunofluorescence microscopy localizes within lamellipodia and filopodia several crosslinking proteins including fascin, fimbrin, alpha-actinin and filamin. While these proteins may organize actin into bundles and networks, fimbrin and alpha-actinin may play an additional role of linking the cytoskeleton to cell-substratum adhesion sites.