N-methyl-D-aspartate receptor-induced translocation of protein kinase C to the nucleus in rat cerebellar slices

Isoform-specific translocation of protein kinase C following glutamate administration in primary hippocampal neurons

High concentrations of glutamate, the major excitatory neurotransmitter in the mammalian brain, lead to intracellular calcium overload resulting in excitotoxic damage and death of neurons. Since protein kinase C (PKC) is involved in neuronal degeneration resulting from cerebral ischemia and from glutamate excitotoxicity, we investigated the effect of glutamate on changes in the cellular distribution of various PKC isoforms in cultured hippocampal neurons in comparison with the effects elicited by the PKC activator phorbol ester. Out of the expressed PKC isoforms alpha, gamma, epsilon, zeta and lambda only the conventional isoforms PKC alpha and gamma responded to glutamate. Using subcellular fractionation and Western blotting with isoform-specific antibodies and immunocytochemical localization with confocal laser scanning microscopy, we observed that phorbol ester and glutamate have different effects on PKC isoform redistribution: Whereas phorbol ester resulted in translocation of PKC alpha and PKC gamma toward a membrane fraction, the glutamate-mediated rise in intracellular calcium concentration induced a translocation mainly toward a detergent-insoluble, cytoskeletal fraction. Immunocytochemical analysis revealed an isoform-specific translocation following glutamate treatment: PKC gamma was translocated mainly to cytoplasmic, organelle-like structures, whereas PKC alpha redistributed to the plasma membrane and into the cell nucleus. The latter result is of special interest, as it indicates that nuclear PKC may play a role in processes of excitotoxic cell damage.

Messengers from the synapses to the nucleus (MSNs) that establish late phase of long-term potentiation (LTP) and long-term memory

The late stage of long-term potentiation (LTP) and long-term memory is believed to be largely governed by altered gene expression for its generation and maintenance, while the early stages of LTP and memory are controlled mainly by the phosphorylation-dephosphorylation of the synaptic proteins. For the altered gene expression, synaptic information must be transmitted from the synaptic sites to the nucleus. This article describes the presence of specific messenger molecules that transmit synaptic information to the nucleus; these molecules are referred to as MSNs (Messengers from Synapse to the Nucleus). In addition, recent studies have indicated that certain transcription factors localize at postsynaptic sites as well as the nucleus, and may function as MSNs.