Alteration in MARCKS phosphorylation and expression by methylmercury in SH-SY5Y cells and rat brain.

The molecular mechanisms mediating methylmercury (MeHg)-induced neurotoxicity are not completely understood. Because myristoylated alanine-rich C kinase substrate (MARCKS) plays an essential role in the differentiation and development of neuronal cells, we studied the alteration of MARCKS expression and phosphorylation in MeHg-induced neurotoxicity of neuroblastoma SH-SY5Y cells and in the rat brain. Exposure to MeHg induced a decrease in cell viability of SH-SY5Y cells, which was accompanied by a significant increase in phosphorylation and a reduction in MARCKS expression. Pretreatment of cells with a protein kinase C inhibitor or an extracellular Ca(2+) chelator suppressed MeHg-induced MARCKS phosphorylation. In MARCKS knock-down cells, MeHg-induced cell death was significantly augmented in comparison to control siRNA. In brain tissue from MeHg-treated rats, MARCKS phosphorylation was enhanced in the olfactory bulb in comparison to control rats. The present study may indicate that alteration in MARCKS expression or phosphorylation has consequences for MeHg-induced neurotoxicity.