Neuron-specific expression of therapeutic proteins: Evaluation of different cellular promoters in recombinant adenoviral vectors

In order to achieve neuron-restricted expression of antiapoptotic proteins, cellular promoters were investigated for their expression profiles in the context of adenoviral vectors. Both the synapsin 1 gene and the tubulin alp ha1 gene promoters were strictly neuron specific in cocultures of primary n eurons with their essential feeder cells. The neuron-specific enolase gene promoter exhibited only weak activity in cultured hippocampal neurons and w as not neuron specific in preparations of cerebellar granule cells. By atta ining virtually 100% transduction efficiency we were able to generate "quas i-transgenic" primary neuron cultures using both differentiated and complet ely undifferentiated hippocampal neurons. In a functional assay, we used th e synapsin promoter to evaluate the effect of Bcl-X-L, overexpression on po tassium-withdrawal-induced apoptosis of cerebellar granule neurons. We foun d nearly complete inhibition of caspase-9 and -3 activation and apoptosis, indicating a major role for mitochondrial pathways in this paradigm of neur onal cell death. The excellent suitability of the synapsin promoter as a st rong panneuronal promoter was further demonstrated by its restricted neuron al activity in various brain regions of adult rats in vivo.