title: Multiple receptors linked to inhibition of adenylate cyclase accelerate Na+/H+ exchange in neuroblastoma x glioma cells via a mechanism other than decreased cAMP accumulation.
abstract: alpha 2-Adrenergic receptors, a population of receptors linked to inhibition of adenylate cyclase, accelerate Na+/H+ exchange in NG108-15 neuroblastoma x glioma cells (Isom, L. L., Cragoe, E. J., Jr., and Limbird, L. E. (1987) J. Biol. Chem. 262, 6750-6757). We now report that two other receptor populations linked to inhibition of adenylate cyclase, muscarinic cholinergic and delta-opiate receptors, also alkalinize the interior of NG108-15 cells, as measured with the pH-sensitive fluorescent probe, 2,7-biscarboxyethyl-5(6)-carboxy-fluorescein. Manipulations that block Na+/H+ exchange, i.e. removal of extracellular Na+, reduction of extracellular pH to equal that of intracellular pH, and addition of 5-amino-substituted analogs of amiloride, all block alpha 2-adrenergic, delta-opiate, or muscarinic cholinergic receptor-induced alkalinization in a parallel fashion. These data suggest that all three populations of receptors alkalinize NG108-15 cells by acceleration of Na+/H+ exchange and do so via a shared or similar mechanism. Although these three receptor populations are linked to inhibition of adenylate cyclase, decreased production of cAMP does not appear to be the mechanism responsible for receptor-accelerated Na+/H+ exchange. Thus, ADP-ribosylation of intact NG108-15 cells with Bordetella pertussis islet-activating protein prevents attenuation of prostaglandin E1-stimulated cAMP accumulation by alpha 2-adrenergic, muscarinic, and delta-opiate agonists but has no measurable effect on the ability of these agonists to accelerate Na+/H+ exchange. Similarly, manipulations that block receptor-accelerated Na+/H+ exchange influence but do not block receptor-mediated attenuation of cAMP accumulation. Thus, the present data suggest that these two receptor-mediated biochemical events, acceleration of Na+/H+ exchange and attenuation of cAMP accumulation, occur through divergent mechanisms in NG108-15 cells.
authors.affiliation: Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232.
authors.forename: L L
authors.initials: LL
authors.lastname: Isom
authors.forename: E J
authors.initials: EJ
authors.lastname: Cragoe
authors.forename: L E
authors.initials: LE
authors.lastname: Limbird
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D000527:Alprostadil / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D005910:Glioma; D006825:Hybridomas / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D051379:Mice; D009447:Neuroblastoma; D037342:Pertussis Toxin; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000378:metabolism*; D011957:Receptors, Opioid / Q000378:metabolism*; D017465:Receptors, Opioid, delta; D017923:Sodium-Hydrogen Exchangers; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D037361:Adenylate Cyclase Toxin; D000067956:Adenylyl Cyclase Inhibitors; D002352:Carrier Proteins; D011942:Receptors, Adrenergic, alpha; D011976:Receptors, Muscarinic; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017923:Sodium-Hydrogen Exchangers; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D000584:Amiloride; D000242:Cyclic AMP; D037342:Pertussis Toxin; D000527:Alprostadil