Cloning and Characterization of a Mouse σ1 Receptor

Abstract: A cDNA clone (S2‐1a) isolated from a mouse brain cDNA library, using a guinea pig σ1 cDNA as probe, has high homology to the predicted protein sequence of the guinea pig (88%) and human (90%) σ1 receptors. Northern analysis revealed a major mRNA of ∼1.8 kb in a wide range of mouse tissues, with highest levels in brain, liver, kidney, and thymus. Southern analysis and chromosomal mapping in the mouse suggested a single‐copy gene in region A5‐B2 of chromosome 4. Expression of the clone in MCF‐7 and CHO cells led to a pronounced increase in (+)‐[3H]pentazocine binding with a selectivity profile consistent with σ1 receptors. In vitro translation yielded a protein of ∼28 kDa, as did transfection of a probe containing the hemagglutinin (HA) epitope (S2‐1a.HA) into CHO cells, as determined by western analysis using an antibody directed against HA. (+)‐[3H]‐Pentazocine binding to immunopurified HA‐tagged receptor demonstrated conclusively that S2‐1a.HA encodes a high‐affinity (+)‐[3H]pentazocine binding site with characteristics of a murine σ1 receptor. An antisense oligodeoxynucleotide designed from S2‐1a potentiated opioid analgesia in vivo.