Alteration of OBCAM conformation as a result of opioid receptor expression and opioid ligand treatment.
Several lines of evidence link the opioid binding cell adhesion molecule (OBCAM) to opioid function. When delta-opioid receptor cDNA (DOR-1) was expressed in CHO cells, OBCAM immunoreactivity (OBCAM-ir) was detected. Transfected cell lines which displayed high opioid binding also expressed high cell surface OBCAM-ir, while untransfected CHO and vector control cells did not. The positive control, neural cell adhesion molecule (NCAM), a protein with structural homology to OBCAM, displayed the same levels of immunofluorescence in transfected and nontransfected cell lines. Membranes from CHO cells transfected with and expressing a variety of muscarinic and dopamine receptors were tested for immunoreactivity. No significant OBCAM-ir was detected in any of these cell membranes. When anti-OBCAM peptide antibodies were used for immunoblots of CHO cells, untransfected, non-binding transfected, and high binding transfected cells revealed the same banding patterns with approximately equal intensity. These observations suggest that in untransfected cells OBCAM is either not present on the extracellular side of the CHO cell membrane or that it exists in an altered conformation which changes upon transfection with opioid receptors to allow recognition of the non-denatured protein by anti-OBCAM antibodies.
Lane
C M
CM
Department of Pharmacology, University of Minnesota Medical School, Minneapolis 55455, USA.
Jones
C R
CR
Reisine
T
T
Yu
L
L
Lee
N M
NM
D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins / Q000737:chemistry*; D015815:Cell Adhesion Molecules / Q000737:chemistry*; D002460:Cell Line; D006224:Cricetinae; D005455:Fluorescent Antibody Technique; D006822:Hybrid Cells; D008024:Ligands; D009363:Neoplasm Proteins / Q000737:chemistry*; D019006:Neural Cell Adhesion Molecules / Q000032:analysis; D011487:Protein Conformation; D017465:Receptors, Opioid, delta / Q000235:genetics*
D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; D008024:Ligands; D009363:Neoplasm Proteins; D019006:Neural Cell Adhesion Molecules; D017465:Receptors, Opioid, delta