N-methyl-D-aspartate receptor activation results in regulation of extracellular signal-regulated kinases by protein kinases and phosphatases in glutamate-induced neuronal apototic-like death

Extracellular signal-regulated kinases (ERK1/ERK2) have been shown transien tly activated and involved in excitotoxicity. We searched for upstream mole cules responsible for the regulation of glutamate-induced ERK1/ERK2 activat ion and ERK1/ERK2-mediated apototic-like death in cultured rat cortical neu rons. ERK1/ERK2 activation (monitored by anti-active ERK1/ERK2 antibody) wa s almost completely prevented by blockage of NMDA receptor (NMDA-R) or elim ination of extracellular Ca2+, but not any other glutamate receptor or L-ty pe voltage-gated Ca2+ channel. It was prevented largely by inhibition of pr otein kinase C (PKC), protein-tyrosine kinases (PTK), respectively, but mil dly by that of CaM kinase II. Combined inhibition of CaM kinase IJ (but not PTK) and PKC had an additive effect. Reversion of ERK1/ERK2? activation wa s largely prevented by inhibition of protein phosphatase (PP) 1 or protein tyrosine phosphatase (PTP). Combined inhibition of PP 1 and PTP had no addi tive effect. Glutamate-induced apoptotic-like death (determined by DAPI sta ining) was largely prevented by inhibition of NMDA-R, PKC, CaM kinase II, P TK and MEK1/MEK2 (ERK1/ERK2 kinase). respectively. Combined inhibition of C aM kinase II (but not PKC or PTK) and MEK1/MEK2 had an additive effect. Glu tamate-induced apoptotic-like death was promoted by inhibition of PP1 and P TP, respectively. The above results suggested that in glutamate-induced cor tical neurotoxicity ERK1/ERK2? activation be mainly mediated by NMDA-R. Sub sequently, a pathway dependent on both PKC and PTK was mainly involved, whi ch was also mainly responsible for ERK1/ERK2-mediated apoptotic-like death, and a CaM kinase II-dependent pathway was relatively mildly involved. Reve rsion of ERK1/ERK2 activation was mainly mediated by a pathway dependent on both PPI and PTP, which might be involved in the restrain of glutamate-ind uced neurotoxicity. (C) 2000 Elsevier Science B.V. All rights reserved.