Up-regulation of NMDAR1 subunit gene expression in cortical neurons via a PKA-dependent pathway.

Transcription mediated by protein kinase A and the cAMP response element binding protein (CREB) has been linked to the establishment of long-term memory and cell survival. However, all of the major targets for activated CREB have yet to be identified. Given the fact that CREB-mediated transcription is intimately involved in cellular processes of learning and memory and that CREB activity can be regulated by synaptic N-methyl-d-aspartate receptors (NMDARs) and metabotropic GABA receptors, we have studied the role of the cAMP-dependent signaling pathway in the regulation of the NMDA receptor subunit 1 (NMDAR1), a subunit required for functional receptor formation. We now report that levels of NMDAR1 subunit protein in primary neocortical cultures are increased 66% in response to forskolin, an activator of adenylyl cyclase. Up-regulation of NMDAR1 is paralleled by a twofold increase in mRNA levels and an 83% increase in NMDAR1 promoter/luciferase reporter activity that is dependent on protein kinase A. Three cAMP regulatory elements (CREs) in the rat NMDAR1 promoter (- 228, - 67, and - 39) bind CREB in vitro and forskolin increases binding to two of the sites (- 228 and - 67). Chromatin immunoprecipitation of neuronal rat genomic DNA reveals that CREB is bound in vivo to the endogenous NMDAR1 gene. Increased presence of the activated Ser133 phosphorylated form is dependent on the length of exposure to forskolin. Taken together with the results of mutational analysis, the findings strongly suggest that transcription of NMDAR1 is regulated by the c-AMP signaling pathway, most likely through the binding of CREB and its activation by signal-dependent phosphorylation.