The endoplasmic reticulum stress-responsive protein GRP78 protects neuronsagainst excitotoxicity and apoptosis: Suppression of oxidative stress and stabilization of calcium homeostasis

The 78-kDa glucose-regulated protein (GRP78) is localized in the endoplasmi c reticulum (ER), and its expression is increased by environmental stressor s in many types of nonneuronal cells. We report that levels of GRP78 are in creased in cultured rat hippocampal neurons exposed to glutamate and oxidat ive insults (Fe2+ and amyloid beta-peptide) and that treatment of cultures with a GRP78 antisense oligodeoxynucleotide increases neuronal death follow ing exposure to each insult. GRP78 antisense treatment enhanced apoptosis o f differentiated PC12 cells following NGF withdrawal or exposure to stauros porine. Pretreatment of hippocampal cells with 2-deoxy-D-glucose, a potent inducer of GRP78 expression, protected neurons against excitotoxic and oxid ative injury. GRP78 expression may function to suppress oxidative stress an d stabilize calcium homeostasis because treatment with GRP78 antisense resu lted in increased levels of reactive oxygen species and intracellular calci um following exposure to glutamate and oxidative insults in hippocampal neu rons. Dantrolene (a blocker of ER calcium release), uric acid tan antioxida nt), and zVAD-fmk (a caspase inhibitor) each protected neurons against the death-enhancing action of GRP78 antisense. The data suggest that ER stress plays a role in neuronal cell death induced by an array of insults and that GRP78 serves a neuroprotective function. (C) 1999 Academic Press.