Sodium arsenite exposure alters cell migration, focal adhesion localization and decreases tyrosine phosphorylation of focal adhesion kinase in H9C2 myoblasts

Exposure to the environmental toxicant arsenic is reported to produce a variety of effects including disruption of signal transduction pathways, cell proliferation, and apoptosis. This suggests that arsenite may not have specific targets but rather extremely broad effects. The present study was designed to test the hypothesis that arsenite alters signaling involved in focal adhesion structure and function in cultured myoblasts. H9C2 cells were exposed to 1, 2.5, 5, or 10 mu M sodium arsenite for 48 h. MTT metabolism and staining by neutral red, trypan blue, and propidium iodide showed that sodium arsenite treatments of 5 mu M or less were not overtly cytotoxic. At these doses, sodium arsenite did not affect the amount of polymerized actin in cells, rate of protein synthesis, or amounts of vinculin, talin, paxillin, and focal adhesion kinase (FAK) in cells. However, sodium arsenite-treated cells contained fewer focal adhesions with an altered distribution pattern. Sodium arsenite exposure caused a dose-dependent reduction in cell migration and cell attachment rates. The average area of substrate covered by a cell was also reduced, although the average volume of cells was not significantly affected. Sodium arsenite exposure resulted in reduced tyrosine phosphorylation of FAK, its substrate paxillin and the FAK auto- phosphorylation site, Tyr397. Our results indicate that sodium arsenite can alter focal adhesion structure and function, thus affecting cell attachment and migration and possibly other aspects of focal adhesion function such as integrin signaling. These diverse consequences may be mediated by a relatively specific inhibition of FAK tyrosine phosphorylation, modifying scaffolding proteins.