PLA2 signaling is involved in calpain-mediated degradation of synaptic dihydropyrimidinase-like 3 protein in response to NMDA excitotoxicity

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 PLA2 signaling in NMDA-induced DPYSL3 degradation. Exposure of rat primary cortical neurons (PCN) to PLA2 and COX-2 inhibitors significantly prevented NMDA-induced DPYSL3 degradation. Since the metabolic product of PLA2 signaling, PGE2, 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 PLA2 signaling to NMDA-induced calpain activation and subsequent degradation of synaptic protein DPYSL3.