Fig. 5.

tPA interacts with the NR2B-containing NMDA receptors. The interaction of tPA with the individual NMDA receptor subunits was examined by coimmunoprecipitation. Hippocampal homogenates from wild-type mice were incubated with anti-tPA, -NR1, -NR2A, or -NR2B antibodies followed by adsorption to protein G-sepharose. Immunoprecipitated proteins were eluted with electrophoresis-loading buffer, and the blots were developed by using antibodies against individual subunits of NMDA receptor. The strongest interaction was detected between tPA and NR2B. Weak bands corresponding to NR1 and NR2A detected in the anti-tPA-immunoprecipitated material may reflect indirect interaction through NR2B binding. In control experiments, the immunoprecipitating antibodies were replaced with irrelevant antibodies from the same species. The experiment was repeated on five different occasions with similar results.