Regulation of an opioid-binding protein in NG108-15 cells parallels regulation of delta-opioid receptors.
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 delta-opioid agonists, as well as with nonselective agonists such as etorphine, whereas other agonists including [D-Ala2-N-MePhe4-Gly-ol]enkephalin, 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.
Lane
C M
CM
Department of Pharmacology, University of Minnesota, Minneapolis 55455.
Elde
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Loh
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Lee
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NM
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D015815:Cell Adhesion Molecules; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D020881:Enkephalin, D-Penicillamine (2,5)-; D016308:Enkephalin, Leucine-2-Alanine / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology; D005048:Etorphine / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D058851:GPI-Linked Proteins; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000276:immunology; D051381:Rats; D017465:Receptors, Opioid, delta / Q000187:drug effects / Q000378:metabolism*
D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; D004745:Enkephalins; D058851:GPI-Linked Proteins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; C489215:Opcml protein, rat; D010455:Peptides; D017465:Receptors, Opioid, delta; D005048:Etorphine; D016308:Enkephalin, Leucine-2-Alanine; D020881:Enkephalin, D-Penicillamine (2,5)-