Regulation of an Opioid-Binding Protein in NG108-15 Cells Parallels Regulation of δ-Opioid Receptors

• Published in: Proceedings of the National Academy of Sciences - PNAS 1992-12, Vol.89 (23), p.11234-11238
• Main Authors: Lane, Cynthia M., Elde, Robert, Loh, Horace H., Lee, Nancy M.
• Format: Article
• Language: English
• Subjects: Agonists; Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Animals; Antibodies; Antiserum; Binding and carrier proteins; Biological and medical sciences; Carrier Proteins - metabolism; Cell Adhesion Molecules; Cell Compartmentation; Cell lines; Cell Membrane - metabolism; Cells, Cultured; Cellular immunity; Enkephalin, D-Penicillamine (2,5); Enkephalin, Leucine-2-Alanine - pharmacology; Enkephalins - pharmacology; Etorphine - pharmacology; Fluorescent Antibody Technique; Fundamental and applied biological sciences. Psychology; GPI-Linked Proteins; In Vitro Techniques; Liver cells; Membrane Glycoproteins - metabolism; Molecular Sequence Data; Nerve Tissue Proteins - metabolism; Neurons; Neurons - metabolism; Opioid analgesics; Opioid receptors; Peptides - chemistry; Peptides - immunology; Proteins; Rats; Receptors; Receptors, Opioid, delta - drug effects; Receptors, Opioid, delta - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.89.23.11234

An opioid-binding protein has recently been purified from bovine brain and cloned, and its cDNA sequence has been obtained. Indirect evidence suggests that this protein has a role in opioid-receptor function. However, because direct testing of its function by expression of its cDNA has not yet been possible and because its structure bears no resemblance to G protein-coupled receptors, the role of this protein in opioid-receptor activity is still in question. An antibody raised to a portion of the predicted amino acid sequence of opioid-binding cell-adhesion molecule (OBCAM) specifically labeled the surface of NG108-15 cells, as visualized by immunofluorescence with confocal microscopy. Furthermore, chronic treatment of these cells with opioid agonist, which down-regulates opioid receptors, reduced OBCAM immunoreactivity (ir). Down-regulation of both opioid receptors and OBCAM-ir was greatest after chronic treatment of NG108-15 cells with δ-opioid agonists, as well as with nonselective agonists such as etorphine, whereas other agonists including [D-Ala2-N-MePhe4-Glyol]kenkephalin, morphine, levorphanol, dynorphin A-(1-13), and U-50,488H were less effective or ineffective. Chronic treatment of NG108-15 cells with muscarinic agonists had no effect on OBCAM-ir. Furthermore, NG108-15 cells transfected with an antisense construct to OBCAM have a reduced density of opioid-binding sites as well as reduced OBCAM-ir. Taken together, these results strongly suggest that OBCAM has a role in opioid-receptor function in NG108-15 cells.