IMPACT OF ALTERED ACTIN GENE-EXPRESSION ON VINCULIN, TALIN, CELL SPREADING, AND MOTILITY

Previous studies have demonstrated a strong correlation between the ex pression of vinculin and the shape and motility of a cell (Rodriguez F ernandez et al., 1992a, b, 1993), This hypothesis was tested by compar ing the expression of vinculin and talin with the motility of morpholo gically altered myoblasts, These mouse C2 myoblasts were previously ge nerated by directly perturbing the cell cytoskeleton via the stable tr ansfection of a mutant-form of the beta-actin gene (beta sm) and three different forms of the gamma-actin gene; gamma, gamma minus 3'UTR (ga mma Delta'UTR), and gamma minus intron III (gamma Delta IVSIII) (Schev zov et at, 1992; Lloyd and Gunning, 1993). In the case of the beta sm and gamma-actin transfectants, a two-fold decrease in the cell surface area was coupled, as predicted, with a decrease in vinculin and talin expression, In contrast, the gamma Delta IVSIII transfectants with a seven-fold decrease in the cell surface area showed an unpredicted sli ght increase in vinculin and talin expression and the gamma Delta 3'-U TR transfectants with a slight increase in the cell surface area showe d no changes in talin expression and a decrease in vinculin expression , We conclude that changes in actin gene expression alone can impact o n the expression of vinculin and talin, Furthermore, we observed that these actin transfectants failed to show a consistent relationship bet ween cell shape, motility, and the expression of vinculin. However, a relationship between talin and cell motility was found to exist, sugge sting a role for talin in the establishment of focal contacts necessar y for motility.