Hyperphosphorylation of Intermediate Filament Proteins is Involved in Microcystin-Lr-induced Toxicity in HL7702 Cells

Microcystin-LR (MC-LR) has been regarded as a hepatotoxin, which can cause cytoskeletal reorganization, especially of the actin filaments. However, the underlying mechanisms remain unclear. In this study, whether MC-LR could induce microfilaments disruption was verified in the normal human liver cell line HL7702; and then the transcription, translation, and phosphorylation levels of major microfilament-associated proteins were measured; finally, the underlying mechanisms was investigated. After treatment with MC-LR, the actin filaments lost their characteristic filamentous organization in the cells, demonstrating increased actin depolymerization. The mRNA and protein levels of ezrin, vasodilator-stimulated phosphoprotein (VASP), actin-related protein2/3, and cofilin remained unchanged. However, the phosphorylation levels of ezrin and VASP were increased, when treated with 10 μM MC-LR. Moreover, P38 and ERK1/2 were involved in MC-LR-induced hyperphosphorylation of microfilament-associated proteins. In summary, this study demonstrates that MC-LR can cause disruption of actin filaments in HL7702 cells due to MC-LR-induced mitogen-activated protein kinase pathway activation and hyperphosphorylation of different types of microfilament-associated proteins.