Antisense inhibition of beta-actin mRNA localization and its effect on smooth muscle cell migration.

A crucial step in cell migration involves changes in the actin cytoskeleton in response to extracellular signals. We have previously shown that beta-actin transcripts are associated with mobile regions of mouse 3T3 fibroblasts when grown in the presence of serum. In the current study we used in situ hybridization and laser scanning confocal microscopy to show that cultured rat smooth muscle cells also localize beta-actin mRNA to the cell periphery and that this peripheral pool of beta-actin mRNA is dependent on the presence of growth factors in the culture medium. We also show that antisense phosphorothioated oligonucleotides directed against sequences in the 3' untranslated region of rat beta-actin mRNA block peripheral localization of beta-actin mRNA while the corresponding control oligonucleotides have no effect. Time-lapse video analysis demonstrates that the antisense oligonucleotides inhibit rat smooth muscle cell migration in culture and analysis of beta-actin mRNA confirms this is not due to changes in beta-actin gene expression or instability of the message. Our results suggest that depletion of beta-actin transcripts from the cell periphery is associated with suppression of SMC migration.