Characterization and regulation of beta 1-adrenergic receptors in a human neuroepithelioma cell line.
Intact human neuroepithelioma SK-N-MC cells bound the beta-adrenergic antagonist (-)-[3H]-CGP 12177 with a KD of 0.13 nM and a Bmax of 17,500 sites/cell. When the cells were exposed to beta-adrenergic agonists, they accumulated cyclic AMP in the following order of potency: isoproterenol much greater than norepinephrine greater than epinephrine, which is indicative of a beta 1-subtype receptor. Membranes prepared from the cells bound (-)-3-[125I]iodocyanopindolol with a KD of 11.5 pM. Inhibition of agonist-stimulated cyclic AMP production and competition binding experiments indicated that the beta 1-selective antagonists CGP 20712A and ICI 89,406 were much more potent than the beta 2-selective antagonist ICI 118,551. Analysis of the displacement curves indicated that the cells contained only beta 1-adrenergic receptors. Northern blot analysis of SK-N-MC mRNA using cDNA probes for the beta 1- and beta 2-adrenergic receptors revealed the presence of a very strong beta 1-adrenergic receptor mRNA signal, while under the same conditions no beta 2-adrenergic receptor mRNA was observed. Thus, SK-N-MC cells appear to express a pure population of beta 1-adrenergic receptors. When the cells were exposed to isoproterenol, there was no observable desensitization during the first hour. After longer exposure, desensitization slowly occurred and the receptors slowly down-regulated to 50% of control levels by 24 h. Other agents that elevate cyclic AMP levels, such as forskolin, cholera toxin, and cyclic AMP analogues, caused no or little substantial receptor loss.
Fishman
P H
PH
Membrane Biochemistry Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892.
Nussbaum
E
E
Duman
R S
RS
D000319:Adrenergic beta-Antagonists / Q000378:metabolism / Q000494:pharmacology; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000096:biosynthesis; D015342:DNA Probes; D015536:Down-Regulation; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D007457:Iodine Radioisotopes; D020120:Iodocyanopindolol; D007545:Isoproterenol / Q000494:pharmacology; D018241:Neuroectodermal Tumors, Primitive, Peripheral / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D009693:Nucleic Acid Hybridization; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011412:Propanolamines / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000319:Adrenergic beta-Antagonists; D015342:DNA Probes; D007457:Iodine Radioisotopes; D011412:Propanolamines; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D020120:Iodocyanopindolol; D010869:Pindolol; D000242:Cyclic AMP; D007545:Isoproterenol; C033394:CGP 12177; D009638:Norepinephrine; D004837:Epinephrine