Cloning of ligand-specific cell lines via gene transfer: Identification of a D₂ dopamine receptor subtype

Using rat genomic DNA, we have established a transfected mouse fibroblast cell line that expresses a spiperone binding site with the pharmacological characteristics of a D₂ dopamine receptor. The expressed D₂ receptors are the product of a gene that is distinct from that reported by Bunzow et al. [Bunzow, J.R., Van Tol, H.H.M., Granoly, D.K., Albert, P., Salon, J., Christie, M., Machida, C.A., Neve, K.A. and Civelli, O. (1988) Nature (London) 336, 783-787]. Flow cytometry with the Ca²⁺-sensitive dye indo-1 demonstrated that activation of the expressed D₂ sites resulted in increases in intracellular calcium that were dependent on the influx of external Ca²⁺. These general cloning procedures should be applicable to the production of cell lines expressing a variety of genes for which only functional assays are available.