Studies On Molecular Mechanism Of Learning And Memory Enhancement In NR2B Transgenic Mice

N-methyl-D-aspartate (NMDA) receptor plays a pivotal role in different forms of memory. Overexpression of one of the subunit of NMDA receptor, NR2B, in the forebrain of transgenic (Tg) mice leads to enhanced activation of NMDA receptor, facilitating synaptic potentiation in response to stimulation at 10±100 Hz. These mice exhibit superior ability in learning and memory in various behavioral tasks. However, the molecular mechanism of the enhancement of learning and memory in NR2B transgenic mice is to be elucidated. First, we examined the mRNA expression level of the three subunits of NMDA receptor NR1, NR2A and NR2B of the hippocampus and cortex in 19- and 24-month Tg mice by Real-time PCR. Next, the gene expression profiles of the hippocampus and cortex of 3-, 19-, 24-month Tg mice were examined by oligonucletide microarray and Real-time PCR. The results were ananlyzed using cluster 3.0 to identify the related genes and signaling pathways.The results showed that intracellular calcium release channel genes ryanodine receptor (RyR) and its related genes Triadin 2 (Trdn), histidine rich calcium binding protein (Hrc), Ca2+/Calmodulin dependent protein kinase IV (CaMKIV) and some important transcription related genes were altered in Tg mice. It has been well established that RyR plays an important role in memory. On the postsynaptic density, through the proteins PSD95, GKAP and Shank, NR2B links Homer together with the NMDA receptor complex. Homer-1c has been shown to interact with RyR1 and RyR2 to regulate its activity in skeletal muscle. It would be interesting to know whether the protein-protein interaction is also present in the brain. In addition, RyR not only affects gene transcription, but also is involved in NO-cGMP-PKG pathway and increase the release of the intracellular calcium, which in turn causes phosphorylation of CREB during the induction of L-LTP.In this study, we examined the expression changes of RyR1-3 and related genes, the interaction of RyR and Homer-1c, expressions of the phospho-CREB using the Real-time PCR, co-Immunoprecipation and Western blot technologies, respectively. Our results have provided important clues for the molecular mechanism of learning and memory enhancement in NR2B Tg mice.1. The expression of the NMDA receptor NR1, NR2A and NR2B subunit in NR2B transgenic mice.