PLA 2 signaling is involved in calpain-mediated degradation of synaptic dihydropyrimidinase-like 3 protein in response to NMDA excitotoxicity

Abstract

Dihydropyrimidinase-like 3 (DPYSL3) is believed to play a role in neuronal differentiation, axonal outgrowth and neuronal regeneration, as well as cytoskeleton organization. Recently we have shown that glutamate excitotoxicity and oxidative stress result in calpain-dependent cleavage of DPYSL3, and that NOS plays a role in this process [R. Kowara, Q. Chen, M. Milliken, B. Chakravarthy, Calpain-mediated truncation of dihydropyrimidinase-like 3 protein (DPYSL3) in response to NMDA and H2O2 toxicity, J. Neurochem. 95 (2005) 466–474; R. Kowara, K.L. Moraleja, B. Chakravarthy, Involvement of nitric oxide synthase and ROS-mediated activation of L-type voltage-gated Ca(2+) channels in NMDA-induced DPYSL3 degradation, Brain Res. 1119 (2006) 40–49]. The present study investigates the involvement of PLA 2 signaling in NMDA-induced DPYSL3 degradation. Exposure of rat primary cortical neurons (PCN) to PLA 2 and COX-2 inhibitors significantly prevented NMDA-induced DPYSL3 degradation. Since the metabolic product of PLA 2 signaling, PGE 2, which augments toxic effect of NMDA, is known to stimulate cAMP, the effect of adenyl cyclase activator (forskolin plus IBMX) and inhibitor (MDL12,300) on NMDA-induced DPYSL3 degradation was tested. Our data indicate that the activation of adenyl cyclase contributes to NMDA-induced DPYSL3 degradation. Furthermore, cAMP-dependent protein kinase (PKA) inhibitor PKI (14–22) provided additional evidence of PKA involvement in NMDA-induced DPYSL3 degradation. In summary, the obtained data show the contribution of PLA 2 signaling to NMDA-induced calpain activation and subsequent degradation of synaptic protein DPYSL3.