Tropomyosin in peripheral ruffles of cultured rat kidney cells

Tropomyosin distribution has been studied in two normal lines and one transformed line of rat kidney cells during the early phases of substrate attachment and growth. One non-motile normal line, which spreads rapidly after attachment, immediately begins to assemble prominent stress fibers that contain tropomyosin. It displays small peripheral ruffles that are not noticeably stained with anti-tropomyosin. The other normal line is motile and produces large ruffles that are brightly stained with anti-tropomyosin. Large numbers of tropomyosin-positive stress fibers assemble only after the cells stop moving and lose the peripheral ruffles. The transformed line does not assemble stress fibers but does contain large numbers of actin filament bundles in ruffles on the cell surface that are stained with anti-tropomyosin. These observations indicate that cytoskeletal tropomyosin is not restricted in distribution to stress fibers, and may undergo re-organization along with actin during the transition from motile to non-motile behavior.