Identification of mammalian brain and spinal cord opioid receptor by photoaffinity labeling

Josef Rudinger Memorial Lecture 2002. The chemistry of the opioid receptor binding sites

Since the discovery of the opioid receptors and their endogenous ligands an immense research work has been devoted to the exploration of their specificity, the mechanism of ligand binding and ligand-receptor interactions. One of the main goals has been the location and characterization of the binding sites. The present review compiles the results achieved in this field in the last quarter of a century, and puts some questions concerning the success of these efforts.

Investigation of opioid receptor binding protein in adult and fetal mouse brain membranes by photoaffinity labeling

125I-[D-Ala2,p-N3-Phe4-Met5]Enkephalin was used to investigate the opioid receptor from brain membranes of adult (6 months old) and fetal (16 days gestation) mice. The photolabeled membranes were analyzed by sodium dodecyl sulfate gel electrophoresis. A 46,000-Da protein was specifically photo-labeled in the adult mouse brain membranes. The photolabeling of this protein was inhibited in the presence of [D-Ala2,Met5]enkephalin and a peptide ligand specific for the mu-opioid receptor. No specific labeling of any protein was detected in the brain membranes of the fetal mice. This apparent lack of the opioid receptor in the fetal mouse brain suggests that the appearance of the opioid receptor in the adult mouse brain is subject to developmental regulation.