Disorganization of microfilaments is accompanied by downregulation of alpha-smooth muscle actin isoform mRNA level in cultured vascular smooth muscle cells.

In the previous report, we demonstrated that cAMP negatively regulated alpha-smooth muscle actin mRNA levels through destabilization of the mRNA [O. Ohara et al. (1991) J. Biochem. 109, 834-839]. We here report that the decline in the alpha-smooth muscle actin mRNA levels was well correlated with disorganization of microfilaments but not necessarily with the rise in intracellular cAMP levels in rat cultured vascular smooth muscle cells. The decrease in the alpha-smooth muscle actin mRNA induced by microfilament-disorganizing agents also resulted from enhancement of the turnover rate of the mRNA. These results raise the possibility that the post-transcriptional control of the alpha-smooth muscle actin expression is linked to the organization of actin filaments in smooth muscle cells.