EXPRESSION OF THE CALCIUM-BINDING PROTEIN, PARVALBUMIN, IN CULTURED CORTICAL-NEURONS USING A HSV-1 VECTOR SYSTEM ENHANCES NMDA NEUROTOXICITY

Calcium-binding proteins (CaBPs) are a family of proteins having a uni que distribution in the brain and are thought to be important in buffe ring intracellular calcium. Glutamate neurotoxicity is a process by wh ich the over-activation of glutamate receptors can cause the influx of excessive extracellular calcium and neuronal cell death. It has been proposed that neurons containing CaBP may be more resistant to glutama te neurotoxicity due to their increased ability to buffer calcium. Usi ng a herpes simplex virus-1 (HSV-1) vector system we packaged the CaBP gene, parvalbumin, or the marker gene, beta-galactosidase (beta-gal), correctly in viron particles, which were found upon infection to expr ess mRNA specific to these vectors. PC12 and neocortical cultures show ed strong immunohistochemical staining for either beta-gal or parv. Th e cortical cultures stained positively for endogenous glutamate decarb oxylase, a marker for GABAergic neurons, but not for endogenous parval bumin, indicating that parvalbumin was being expressed ectopically fro m the HSV-1 vector. Interestingly, the expression of parvalbumin incre ased cortical culture's susceptibility to N-methyl-D-aspartate-induced neurotoxicity. This increase in neurotoxicity was not due to the wild -type virus or the helper virus which accompanies the packaging of the se vectors. We speculate that the ectopic expression of parvalbumin in cortical cultures may be increasing glutamate release which in turn i ncreases cell death.