Postsynaptic expression of Ca2+-permeable AMPA-type glutamate receptor channels by viral-mediated gene transfer

The ability to artificially express a particular receptor protein in the postsynaptic sites of neurons in the central nervous system (CNS) would be useful for the study of synaptic function of cloned receptor genes as well as for gene therapy of neurological disorders caused by dysfunction of postsynaptic receptors. In this study, we aimed to express the cDNA of unedited GluR2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptor that forms inwardly rectifying and Ca2+-permeable channel in CNS neurons by using adenoviral-mediated gene transfer. For this purpose, we have constructed a recombinant adenovirus bearing an expression-switching unit, where the unedited GluR2 cDNA can be activated by the Cre recombinase-mediated excisional deletion of a stuffer DNA interposed between the promotor and the coding region. When PC12 cells were infected with this recombinant adenovirus together with an adenovirus expressing Cre recombinase, the inwardly rectifying and Ca2+-permeable AMPA receptor channels were expressed in nearly 100% of infected cells. Two days after co-infection of cultured rat hippocampal neurons with these adenoviruses, fast excitatory neurotransmission in the glutamatergic synapse was mediated predominantly by the inwardly rectifying and Ca2+-permeable AMPA receptor channels. This indicates that the native AMPA receptors in the postsynaptic sites of the glutamatergic synapse are replaced rapidly with recombinant receptors newly produced by the viral-mediated gene transfer.