Excitatory amino acids (EAAs) and their receptors play many important physiological roles in the central nervous system. They are involved in brain development, neural plasticity, and memory acquisition. In addition there is much circumstantial evidence suggesting a role for EAAs and their receptors in neurodegenerative disorders of aging, including Alzheimer's Disease. The receptors for EAAs exist in different functional forms due to the presence of multiple subunits and isoforms and their differential distribution in the brain. We propose the hypothesis that abnormal regulation of expression of EAA receptors or their persistent overactivity may be responsible for the neuropathology seen in these disorders. We previously cloned the promoter of the NMDAR1 gene and observed that a proximal region is sufficient to confer neuronal specific expression. We now show that both Sp1 and GSG motifs are required for basal activity suggesting control over NMDA receptor expression by immediate early genes. An Sp1-like and several other transcription factors cooperatively interact to control this activity. We show that CREB protein induces reporter gene activity. Various trophic factors also induce expression of a reporter gene including NGF and FGF. Interestingly, TPA stimulates expression greater than 5-fold suggesting a role for PKC in regulating NMDAR1 expression. A combination of cAMP and NGF treatment increases expression 7-fold suggesting phosphorylation events are also critical in regulating gene activity. The regulation of NMDAR1 gene expression appears to be complex and tightly controlled. We also cloned promoter regions for NMDAR2-A,B, and C genes and are currently characterizing them. Transgenic technology, utilizing lacZ promoter constructs will be used to confirm the neuronal specificity and regulation of this promoter. A neuronal cell culture model is being developed to examine receptor gene expression and signal transduction cascades involved in glutamate mediated cell death.
