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The proteolytic activity of tissue-plasminogen activator enhances NMDA receptor-mediated signaling


Tissue-plasminogen activator (t-PA) is now available for the treatment of thrombo-embolic stroke but adverse effects have been reported in some patients, particularly hemorrhaging. In contrast, the results of animal studies have indicated that t-PA could increase neuronal damage after focal cerebral ischemia. Here we report for the first time that t-PA potentiates signaling mediated by glutamatergic receptors by modifying the properties of the N-methyl-D-aspartate (NMDA) receptor. When depolarized, cortical neurons release bio-active t-PA that interacts with and cleaves the NR1 subunit of the NMDA receptor. Moreover, the treatment with recombinant t-PA leads to a 37% increase in NMDA-stimulated fura-2 fluorescence, which may reflect an increased NMDA-receptor function. These results were confirmed in vivo by the intrastriatal injection of recombinant-PA, which potentiated the excitotoxic lesions induced by NMDA. These data provide insight into the regulation of NMDA-receptor–mediated signaling and could initiate therapeutic strategies to improve the efficacy of t-PA treatment in man.

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Figure 1: The catalytic activity of t-PA enhances neuronal death induced by exposure to NMDA.
Figure 2: Depolarization induces the release of biologically active t-PA from cortical neurons.
Figure 3: t-PA interacts with and cleaves the NR1 subunit of the NMDA receptor.
Figure 4: rt-PA treatment enhances the NMDA-evoked Ca++ increase in cortical neurons.
Figure 5: rt-PA induces a cleavage in the NR1 subunit of the NMDA receptor and enhances the NMDA-induced neuronal death.


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We thank L. Plawinski for his technical assistance and A. Ruocco for his involvement in this study. We were supported by grants from the CNRS and the University of Caen. The following received doctoral bursaries: O.N. (Commissariat à l'Energie Atomique-CEA), F.D. (Regional Council of Lower Normandy), and C.A. (Ministry of Education and Research). The investigation was carried out within the framework of the Functional Neuroimaging Institute (IFR 47).

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Correspondence to Denis Vivien or Alain Buisson.

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Nicole, O., Docagne, F., Ali, C. et al. The proteolytic activity of tissue-plasminogen activator enhances NMDA receptor-mediated signaling. Nat Med 7, 59–64 (2001).

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