of Work: Glutamate receptors play a pivotal role in several brain functions including fast excitatory neurotransmission, induction and maintenance of long term potentiation, and synaptic plasticity. However, over-activation of these receptors is thought to initiate a pathway of neuronal cell death in both acute and chronic brain insults. A major focus of this project is to discover the pathological roles that excitatory amino acid (glutamate) receptors play in neuronal cell loss in aging and Alzheimer?s Disease, and the mechanisms by which this cell loss occurs. One of our objectives is to determine how the N-methyl-D-Aspartate 1 receptor gene (NMDAR1) and other family member genes are regulated at the transcriptional level. Another objective of this project is to determine the mechanism by which glutamate causes cell death and the role activation of glutamate receptors plays in initiating a genetic cascade of programmed cell death. The promoter region of the NMDAR1 gene contains several transcriptional elements in the proximal region responsible for basal, NGF-inducible, and neuronal specific expression. These include GSG and overlapping Sp1 elements and a Neuron Restrictive Silencer Element (NRSE). The transcription factor Sp1 appears to be important in both basal and NGF induced expression of this gene. In recent work we have shown that single-stranded DNA binding proteins (SSBP) interact with the purine-rich strand at the GSG/Sp1 elements. NGF treatment of PC12 cells induces NMDAR1 gene expression and an increase in the binding of these SSBP at these promoter elements. We have proposed a mechanism by which NGF induced expression of NMDAR1 gene involves phosphorylation of Sp1 and decreased Sp1 binding to its cognate element and subsequent binding of single-strand DNA binding proteins. Other work also suggests an important role for Sp1 in gene expression. We have shown that the NMDA promoter contains a distal myocyte- enhancer factor 2C (MEF2C) binding site. MEF2C, together with Sp1, mediates synergistic activation of the NMDAR1 gene. Various studies suggest that this activation involves a direct interaction of Sp1 and MEF2C. Other elements in the NMDAR1 promoter are being studied including two Cyclic AMP responsive consensus sites in the proximal region. Also, we showed that glutamate treatment of a hippocampal cell line caused cell death which could be prevented by the over-expression of Bcl-2 protein. This death may be a form of glutamate-induced oxidative cell death and not excitotoxic cell death.
