Knowledge of the natural roles of cellular prion protein (PrPC) is essential to an understanding of the molecular basis of prion pathologies. This GPIanchored protein has been described in synaptic contacts, and loss of its synaptic function in complex systems may contribute to the synaptic loss and neuronal degeneration observed in prionopathy. In addition, Prnp knockout mice show enhanced susceptibility to several excitotoxic insults, GABAA receptor-mediated fast inhibition was weakened, LTP was modified and cellular stress increased. Although little is known about how PrPC exerts its function at the synapse or the downstream events leading to PrPCmediated neuroprotection against excitotoxic insults, PrPC has recently been reported to interact with two glutamate
receptor subunits (NR2D and GluR6/7). In both cases the presence of PrPC blocks the neurotoxicity induced by NMDA and Kainate respectively. Furthermore, signals for seizure and neuronal cell death in response to Kainate in Prnp knockout mouse are associated with JNK3 activity, through enhancing the interaction of GluR6 with PSD-95. In combination with previous data, these results shed light on the molecular mechanisms behind the role of PrPC in excitotoxicity. Future experimental approaches are suggested and discussed.