Cloning and functional expression of the human type 1 sigma receptor (hSigmaR1)

We have isolated a cDNA clone from a human placental choriocarcinoma cell (JAR) cDNA library which codes for a functional type 1 sigma receptor. An RT-PCR product obtained from guinea pig kidney mRNA using primers specific for the guinea pig sigma receptor cDNA was used to screen the cDNA library. The hSigmaR1 cDNA predicts a protein of 223 amino acids with a single putative transmembrane domain. The amino acid sequence exhibits 93% identity with the guinea pig sigma receptor. When functionally expressed in HeLa cells, the hSigmaR1 cDNA enhances the binding of [3H]-haloperidol, a sigma receptor ligand, to the HeLa cell membranes. The inhibitor specificity of the cloned hSigmaR1 indicates that it is the type 1 sigma receptor. Several human tissues, including placenta, liver, and brain, and several human cell lines express the SigmaR1 mRNA (1.7 kb) to a variable extent.