Acid sphingomyelinase mediates 50-Hz magnetic field-induced EGF receptor clustering on lipid raft

Abstract

Previously, we found that exposure to a 50-Hz magnetic field (MF) could induce epidermal growth factor receptor (EGFR) clustering and phosphorylation on cell surface. In order to explore the possible mechanisms, the roles of acid sphingomyelinase (ASMase) and lipid raft in MF-induced EGFR clustering were investigated in the present study. Human amnion epithelial (FL) cells were exposed to a 50-Hz MF at 0.4 mT for different durations. Intracellular ASMase activity was detected using the Amplex® Red Sphingomyelinase Assay Kit. EGFR clustering, ASMase, and lipid rafts on cell membrane were analyzed using confocal microscopy after indirect immunofluorescence staining. Results showed that disturbing lipid rafts with nystatin could inhibit MF-induced EGFR clustering, indicating that it was dependent on intact lipid raft. Exposure of FL cells to MF significantly enhanced ASMase activity and induced ASMase translocation to membrane that co-localized with lipid rafts. Treatment with imipramine, an ASMase inhibitor, inhibited the MF-induced EGFR clustering. This inhibitory effect could be blocked by the addition of C2-ceramide in the culture medium. It suggested that ASMase mediated the 50-Hz MF-induced EGFR clustering via ceramide which was produced from hydrolyzation on lipid rafts.

• Acid sphingomyelinase
• clustering
• epidermal growth factor receptor
• extremely low-frequency magnetic field
• lipid raft

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the contents and writing of the article.

This work was supported by grants from the Major State Basic Research Development Program of China (973 Program) (No. 2011CB503700) and the National Natural Science Foundation of China (No. 31570 846, 30970671, 31370831).