Calcium‐dependent activation of transglutaminase 2 by nanosecond pulsed electric fields

• Published in: FEBS open bio 2017-07, Vol.7 (7), p.934-943
• Main Authors: Morotomi‐Yano, Keiko, Yano, Ken‐ichi
• Format: Article
• Language: English
• Subjects: Aggregates; Apoptosis; Biotin; Cadaverine; calcium; Calcium (intracellular); Calcium influx; Cell death; Cytotoxicity; Electric fields; Homeostasis; Ionomycin; nanosecond pulsed electric field; Parkinson's disease; Pathogenesis; Physiology; Proteins; protein‐protein crosslinking; RNA-mediated interference; Signal transduction; Transglutaminase 2
• ISSN: 2211-5463; 2211-5463
• DOI: 10.1002/2211-5463.12227

Exposure of cultured human cells to nanosecond pulsed electric fields (nsPEFs) elicits various cellular events, including Ca2+ influx and cell death. Recently, nsPEFs have been regarded as a novel physical treatment useful for biology and medicine, but the underlying mechanism of action remains to be fully elucidated. In this study, we investigated the effect of nsPEFs on transglutaminases (TGs), enzymes that catalyze covalent protein modifications such as protein–protein crosslinking. Cellular TG activity was monitored by conjugation of cellular proteins with biotin‐cadaverine, a cell‐permeable pseudosubstrate for TGs. We applied nsPEFs to HeLa S3 cells and found that overall catalytic activity of cellular TGs was greatly increased in a Ca2+‐dependent manner. The Ca2+ ionophore ionomycin significantly augmented nsPEF‐induced TG activation, further supporting the importance of Ca2+. Among human TG family members, TG2 is known to be the most ubiquitously expressed, and its catalytic activity requires elevated intracellular Ca2+. Given the requirement of Ca2+ for TG activation by nsPEFs, we performed depletion of TG2 by RNA interference (RNAi). We observed that TG2 RNAi suppressed the nsPEF‐induced TG activation and partially alleviated the cytotoxic effects of nsPEFs. These findings demonstrate that TG2 activation is a Ca2+‐dependent event in nsPEF‐exposed cells and exerts negative effects on cell physiology. Nanosecond pulsed electric fields (nsPEFs) have been regarded as a novel physical treatment for cancer. This study demonstrates that nsPEFs activate transglutaminase 2 (TG2) in a Ca2+‐dependent manner. TG2 depletion partially alleviated the cytotoxicity of nsPEFs, suggesting that TG2 activation brings about deleterious effects on biological functions of various proteins and ultimately contributes to the cytotoxic actions of nsPEFs.