Excitotoxicity by kainate-induced seizure causes diacylglycerol kinase ζ to shuttle from the nucleus to the cytoplasm in hippocampal neurons

Abstract

Diacylglycerol kinase (DGK), which consists of several isozymes, plays a pivotal role in lipid second-messenger diacylglycerol metabolism. A nuclear isozyme, DGKζ, which is translocated from the nucleus to the cytoplasm in hippocampal neurons under transient ischemic stress, is implicated in nuclear events of delayed neuronal death. Kainate (KA)-induced seizure is another model used to study excitotoxic stress. Therefore, we examined whether DGKζ is implicated in a different type of degenerative excitotoxicity in hippocampal neurons. We conducted immunohistochemical analysis of rat hippocampi after KA-induced seizures. DGKζ in hippocampal neurons shuttles from the nucleus to the cytoplasm. It never relocates to the nucleus during KA-induced seizures. Marked change in the immunoreactivity is first observed in CA1 pyramidal neurons 2 h after injection during stage 3 seizures. Immunoreactivity for DGKι remains unchanged in the cytoplasm. That for NeuN remains mostly unchanged in the nucleus. Results show that nucleocytoplasmic translocation of DGKζ also occurs in a different model of excitotoxicity that results in apoptotic neuronal death. Cytoplasmic translocation of DGKζ might be involved in early events of the apoptotic cell death pathway in hippocampal neurons under stressed conditions.