MODULATION OF ALPHA-ACTININ LEVELS AFFECTS CELL MOTILITY AND CONFERS TUMORIGENICITY ON 3T3 CELLS

alpha-Actinin is an abundant actin crosslinking protein, also localize d at adherens type junctions. In adhesion plaques, alpha-actinin can l ink the actin filaments to integrin via vinculin and talin, or directl y by binding to the cytoplasmic domain of beta(1)-integrin. The expres sion of alpha-actinin is rapidly elevated in growth-activated quiescen t cells, and is reduced in SV40-transformed 3T3 cells and various diff erentiating cell types (reviewed by Gluck, U., Kwiatkowski, D. J. and Ben-Ze'ev, A. Proc. Nat. Acad. Sci. USA 90, 383-387, 1993). To study t he effect of changes in alpha-actinin levels on cell behavior, alpha-a ctinin expression was elevated in 3T3 cells by transfection with a ful l-length human nonmuscle alpha-actinin cDNA. To suppress alpha-actinin levels, 3T3 cells were transfected with an antisense alpha-actinin cD NA construct. Cells overexpressing alpha-actinin by 40-60% displayed a significant reduction in cell motility, as demonstrated by their slow er locomotion into an artificial wound, and by forming shorter phagoki netic tracks on colloidal gold-coated substrata. 3T3 cells in which th e expression of alpha-actinin was reduced to 25-60% of control levels, after antisense alpha-actinin transfection, had an increased cell mot ility. Moreover, such alpha-actinin-deficient 3T3 cells formed tumors upon injection into nude mice. The results demonstrate that modulation s in alpha-actinin expression can affect, in a major way, the motile a nd tumorigenic properties of cells, and support the view that decrease d alpha-actinin expression could be a common regulatory pathway to mal ignant transformation of 3T3 cells.