DYNAMIC ACTIN STRUCTURES STABILIZED BY PROFILIN

We describe the production and analysis of clonal cell lines in which we have overexpressed human profilin, a small ubiquitous actin monomer binding protein, to assess the role of profilin on actin function in vivo. The concentration of filamentous actin is increased in cells wit h higher profilin levels, and actin filament half-life measured in the se cells is directly proportional to the steady-state profilin concent ration. The distribution of actin filaments is altered by profilin ove rexpression. While parallel actin bundles crossing the cells are virtu ally absent in cells overexpressing profilin, the submembranous actin network of these cells is denser than in control cells. These results suggest that in vivo profilin regulates the stability, and thereby dis tribution, of specific dynamic actin structures.