Recombinant GABA B receptors formed from GABA B1 and GABA B2 subunits selectively inhibit N-type Ca 2+ channels in NG108-15 cells

Abstract

Efficient transfection of NG108-15 cells with GABA B receptor subunits was achieved using polyethylenimine. Baclofen modulated high voltage-activated Ca 2+ current in differentiated cells transfected with GABA B1 and GABA B2 receptor subunits or with the GABA B2 subunit alone, but not with the GABA B1 subunit alone. Characteristics of the current modulation were very similar for cells transfected with GABA B1/2 and GABA B2 subunits. Using antisense oligonucleotides against GABA B1 subunits and also western immunoblotting, we are able to show that NG108-15 cells contain endogenous GABA B1 subunits. Therefore, functional receptors can be formed by the combination of native GABA B1 subunits with transfected GABA B2 subunits, in agreement with the proposed heteromeric structure of GABA B receptors. Finally, we used selective channel blockers to identify the subtypes of Ca 2+ channels that are modulated by GABA B receptors. In fact, in differentiated NG108-15 cells, the recombinant GABA B receptors couple only to N-type Ca 2+ channels.