γ-Actin regulates cell migration and modulates the ROCK signaling pathway

Cell migration plays a crucial role in numerous cellular functions, and alterations in the regulation of cell migration are required for invasive transformation of a tumor cell. While the mechanistic process of actin-based migration has been well documented, little is known as to the specific function of the nonmuscle actin isoforms in mammalian cells. Here, we present a comprehensive examination of gamma-actin's role in cell migration using an RNAi approach. The partial suppression of gamma-actin expression in SH-EP neuroblastoma cells resulted in a significant decrease in wound healing and transwell migration. Similarly, the knockdown of gamma-actin significantly reduced speed of motility and severely affected the cell's ability to explore, which was, in part, due to a loss of cell polarity. Moreover, there was a significant increase in the size and number of paxillin-containing focal adhesions, coupled with a significant decrease in phosphorylated paxillin in gamma-actin-knockdown cells. In addition, there was a significant increase in the phosphorylation of cofilin and myosin regulatory light chain, suggesting an overactivated Rhoassociated kinase (ROCK) signaling pathway in gamma-actin-knockdown cells. The alterations in the phosphorylation of paxillin and myosin regulatory light chain were unique to gamma-actin and not beta-actin knockdown. Inhibition of the ROCK pathway with the inhibitor Y-27632 restored the ability of gamma-actin-knockdown cells to migrate. This study demonstrates gamma-actin as a potential upstream regulator of ROCK mediated cell migration.-Shum, M. S. Y., Pasquier, E., Po'uha, S. T., O'Neill, G. M., Chaponnier, C., Gunning, P. W., Kavallaris, M. gamma-Actin regulates cell migration and modulates the ROCK signaling pathway. FASEB J. 25, 4423-4433 (2011). www.fasebj.org