Delta opioid receptor gene expression in lymphocytes

Previous studies have shown that morphine stimulates simian immunodeficiency virus (SIV) replication in SIV-infected human CEM x174 cells as well as in monkey lymphocytes through a mechanism of delaying the lysis of infected cells (Biochem. Biophys. Res. Commun. 195:1165-1173, 1993). The present study describes the identification of brain-like opioid receptor sequences in RNA transcripts of both CEM x174 cells and monkey lymphocytes. Study of the gene sequence of a lymphocyte opioid receptor encompassing the third transmembrane domain and the third cytoplasmic loop indicates a 96% homology in amino acid composition to the delta opioid receptor in brain cells. Expression of such an opioid receptor sequence in lymphocytic cells is constitutive, since it could be detected in both saline-treated and morphine-treated monkeys as well as in morphine-treated monkeys after detoxification.