Functional occurrence of the interaction of tissue plasminogen activator with the NR1 Subunit of N-methyl-D-aspartate receptors during stroke.

Despite its fibrinolytic effect, tissue-type plasminogen activator (tPA) displays deleterious effects in the brain, including proexcitotoxicity, that can reduce the overall benefit from thrombolysis during stroke. We have proposed that tPA potentiates excitotoxicity by interacting with and cleaving the aminoterminal end of the NR1 subunit of N-methyl-d-aspartate receptors, leading to an increased calcium influx, Erk1/2 activation, and neurotoxicity. Because this mechanism is debated, our aim was to demonstrate its in vivo occurrence and relevance. Because tPA is released under ischemic conditions, we hypothesized that if it indeed processes NR1, then the released fragment should reactivate the immune system in animals that had been immunized long before with recombinant aminoterminal end of the NR1. This effect should be exacerbated in ischemic animals thrombolysed with recombinant tPA.