Glutamate‐induced antigenic changes of phospholipase C‐δ in cultured cortical neurons

Phosphoinositide‐specific phospholipase C (PLC) is a key enzyme in signal transduction. It was previously demonstrated that an antibody to an isozyme of PLC, PLC‐δ, produces intense staining of neurofibrillary tangles (NFT), the neurites surrounding senile plaque (SP) cores and neuropil threads in the brains of patients with Alzheimer's disease (AD). Although the etiology of neuronal degeneration in AD is still to be defined, excitotoxic glutamate might be a candidate. In the present study, an anti‐PLC‐δ antibody was used to examine the influence of glutamate on PLC‐δ immunoreactivity in cultured rat cortical neurons. Exposure to glutamate caused the death of cultured cortical neurons and exhibited increased immunostaining with the anti‐PLC‐δ antibody. Subtoxic doses of glutamate also increased PLC‐δ immunoreactivity in a dose‐dependent manner. Both glutamateinduced neuronal degeneration and the increases in PLC‐δ immunoreactivity were prevented by removal of extracellular Ca2+ or the application of an N‐methyl‐D‐aspartate (NMDA) receptor antagonist, MK801. The glutamate‐induced increase in PLC‐δ immunoreactivity was also prevented by N^ω‐nitro‐Larginine, a nitric oxide (NO) synthase inhibitor. These results suggest that NO formation secondary to Ca²⁺ influx by NMDA receptor activation leads to similar modifications of PLC‐δ to those seen in AD. © 1995 Wiley‐Liss, Inc.