Nanosecond pulsed electric fields act as a novel cellular stress that induces translational suppression accompanied by eIF2α phosphorylation and 4E-BP1 dephosphorylation

Recent advances in electrical engineering enable the generation of ultrashort electric fields, namely nanosecond pulsed electric fields (nsPEFs). Contrary to conventional electric fields used for DNA electroporation, nsPEFs can directly reach intracellular components without membrane destruction. Although nsPEFs are now recognized as a unique tool in life sciences, the molecular mechanism of nsPEF action remains largely unclear. Here, we present evidence that nsPEFs act as a novel cellular stress. Exposure of HeLa 53 cells to nsPEFs quickly induced phosphorylation of eIF2 alpha, activation of its upstream stress-responsive kinases, PERK and GCN2, and translational suppression. Experiments using PERK- and GCN2-knockout cells demonstrated dual contribution of PERK and GCN2 to nsPEF-induced eIF2 alpha. phosphorylation. Moreover, nsPEF exposure yielded the elevated GADD34 expression, which is known to downregulate the phosphorylated eIF2 alpha. In addition, nsPEF exposure caused a rapid decrease in 4E-BP1 phosphorylation irrespective of the PERK/GCN2 status, suggesting participation of both eIF2 alpha and 4E-BP1 in nsPEF-induced translational suppression. RT-PCR analysis of stress-inducible genes demonstrated that cellular responses to nsPEFs are distinct from those induced by previously known forms of cellular stress. These results provide new mechanistic insights into nsPEF action and implicate the therapeutic potential of nsPEFs for stress response-associated diseases. (C) 2012 Elsevier Inc. All rights reserved.